Tie Guide Part 2 Changes - Railway Tie Association

TABLE OF CONTENTSINTRODUCTION ................................................................................................................................................................... 3THE TREATMENT OF WOOD CROSSTIES ......................................................................................................................... 4TECHNICAL ASPECTS AND A LESSON IN WOOD ............................................................................................................ 6A BRIEF HISTORY OF WOOD PRESERVATION .................................................................................................................. 11WHY SHOULD WOOD BE TREATED WITH PRESERVATIVE? .......................................................................................... 12A SUMMARY OF THE COMMERCIAL TIMBERS USED AS CROSSTIE MATERIAL ....................................................... 14THE ENGINEERED WOOD CROSSTIE ................................................................................................................................. 27— Solid Sawn Material— Hybrid Engineered Combination MaterialAPPENDIX ............................................................................................................................................................................ 34— Specifications for Timber Crossties .................................................................................................................................. 35-37— American Wood-Preservers’ Association Preservative Standards, P1/P13, P2, P3 and P4 .............................................. 39-42— American Wood-Preservers’ Association Commodity Specification C, “Crossties and Switch Ties” ............................. 43REFERENCES ........................................................................................................................................................................ 46THE CONDITIONING & TREATMENT OF WOOD CROSSTIES ........................................................................................ 48PREPARATION OF CROSSTIES AND TIMBERS FOR TREATMENT ................................................................................. 49EFFECT OF WOOD STRUCTURE ON TREATMENT .......................................................................................................... 57MOISTURE CONTENT AND ITS EFFECT ON TREATMENT ............................................................................................. 58WOOD PRESERVATIVE AND THE PRESSURE PROCESSES ............................................................................................... 60THE TREATMENT PROCESSES ........................................................................................................................................... 62STANDARDS AND SPECIFICATIONS FOR TREATMENT ................................................................................................ 65QUESTIONS AND ANSWERS .............................................................................................................................................. 66ABOUT THE AUTHORS ....................................................................................................................................................... 76FOR MORE INFORMATION CONTACT USRailway Tie Association • 115 Commerce Drive, Suite C • Fayetteville, GA 30214770.460.5553 (voice) • 770.460.5573 (fax) • ties@rta.org (email) • www.rta.org (website)1

I N T R O D U C T I O NThe wood crosstie has served theAmerican railroad industry since itsearliest days when wood ties were usedas a foundation for the rail in the trackstructure. The dependability and servicelife of this wood component has beenexemplary. The information provided inthis booklet will provide the reader with adescription of the identification, treatmentand ultimate use of wood in theengineered crosstie system.Wood is the only structural buildingmaterial that is renewable. As a timbercrop which can be cut and harvested ona rotation basis, wood sawn for crossties,has served the railroad industry over acentury.With the use of wood preservatives,the durability and service life of wood issignificantly enhanced. This bookletbrings together wood technologyprinciples with a focus on the practicalapplication for “the tie grader in the yard”as her performs his duties of classifyingoaks, mixed hardwoods and softwoodsthat will be treated with a creosotepreservative solution and subsequentlyinstalled in a railroad track.The task is to develop a commonthread illustrating the development andultimate performance of the treated woodcrosstie. It should be noted that withinthis booklet there are some practicalapplications given along with certaintechnical details outlined in the woodcrosstie engineering section. The RailwayTie Association Performance Standardfound in the engineered wood crosstiesection of this manual describes specificstrength property characteristics and loadtraffic environment applications for the varioustypes of wood tie material.This booklet intended for use in theclassroom as well as a practical guide. TheRailway Tie Association, as part of its primarymission, sponsors seminars in the practicalidentification and grading of wood crosstiesand on the engineering principals behind tieperformance. This manual will be aninstructional component in these seminars.3

THE TREATMENT OF WOOD CROSSTIESWood is a cellulosic materialwhich can be adversely affected bydecay fungi, insects, and marineborers. The use of chemicalpreservatives (organic and/orinorganic) must be used to protectwood from attack from theseorganisms.The degree of protectionobtained is dependent upon the typeof preservative used and achievementof proper penetration and retentionof the chemicals. As will bediscussed in later chapters, there is adifference in the treatability of woodspecies. There is also a difference inthe treatability of the sapwood and theheartwood portion of the tree.With respect to wood crossties, theAmerican Wood Preservers’ AssociationUse Category System- UC4 (previouslyreferred to as Standard C-6) for crosstiesand switch ties, gives the generalrequirements for preservative treatment bypressure processes. In addition, describedwithin the Standard are the processing,conditioning, treatments, results of treatment(quality control), and storage of treatedcrosstie materials.The processing and treatment of woodcrossties are somewhat unique.This product, as used by the Americanrailroad industry, has historically beentreated with a creosote solution meeting therequirements of AWPA Standard P2. Thereare also occasions when other timberproducts such as bridge material will betreated using the AWPA Standard P1/P13meeting the requirements for coal tar.A heavy petroleum oil that meets AWPA P4Standard has also been used for blending withcreosote. This creosote/petroleum solution hasbeen used extensively for many years to reducethe cost of the preservation solution. Its use,however, has been in the Western and RockyMountain states and Canada which are areasthat have climatic conditions which are lessconducive to wood deterioration from fungi andinsects. Organisms that attack wood - fungi andtermites - are not as active at low temperatureand humidity levels found in many areas of thesegeographic regions.4

THE TREATMENT OF WOOD CROSSTIESCreosote and its solutions are thepreservatives most widely used.Crossties are typically pressuretreated using the empty-cell method(Lowry or Rueping Process). Thespecified creosote net retention isusually between six and ten poundsper cubic foot (pcf).Prior to treatment, wood crosstiesmust be properly conditioned in orderto achieve the desired preservativepenetration and retention. The variousconditioning methods and processingprocedures are described in theAWPA Book of Standards. A currentcopy of the AWPA Standards isreadily available to anyone who isinvolved in the procurement, treatment,and use of wood crossties and may beobtained at nominal costs from either theAWPA or RTA. (Note that a copy of theAWPA UC4 is included in the appendix.)The treatment results are described asthe retention of preservative andpenetration of preservative. Theaccepted method for retention ofpreservative is based on the readings ofwork tank gauges or scales. Penetrationof preservative is determined by boring arepresentative sample number ofcrossties within a charge of material.Individual railroad customers typicallyadd more specific requirements to theAWPA UC4 Use Category, thus creatinga railroad “specific use” standard.For additional reference materials forthe treatment of wood crossties, oneshould consult the specifications for thetreatment of crossties as described inAREMA (American Railway Engineeringand Maintance-of-Way Association). Thesespecifications also cover the preservativetreatment of crossties and switchties.5

TECHNICAL ASPECTS ANDA LESSON IN WOODWood varies significantly with regard toits structure. The hardwood species differfrom the softwoods. In addition, withineach of these groups there are alsodifferences between the wood species. Tobe even more specific there are differenceswithin the same tree, because theheartwood usually contains substances notfound in the sapwood. These differenceshave an influence on the permeability ofliquids, such as wood preservatives, into thestructure of wood.The hardwood timbers or broadleaftrees, such as the hickories, oaks andmaples, have a cellular structure that serveas sap conductors. These cells, which arepositioned end to end, are commonlyknown as pores or vessels, which fromsomewhat contiuious passages within thewood. The mechanical support is providedby fibers that surround the vessels.6

TECHNICAL ASPECTS ANDA LESSON IN WOODThe softwood timbers or needlebearing trees know as conifers – such asDouglas-fir, the pines, hemlocks and truefirs – do not have the specialized sapconductingcells that are found inhardwoods, but instead have elongatedcells called tracheids or fibers, which havea closed end. These fibers also serve asthe mechanical support and to conduct thesap.The terminology hardwood andsoftwood is often misleading, because thereare some softwoods that are actuallyharder than some hardwoods from astructural standpoint. For instance yellowpoplar, although a broadleaf tree andtermed a hardwood, is actually lower inspecific gravity, less dense and softer thanDouglas-fir, which is classified as asoftwood.Hardwoods are classified based onpore size and distribution within a growthring (annual ring). The hardwood timbers,such as beech, birch, the gums and maples,in which the pores are somewhat uniform insize and distribution, are called “diffuseporous”woods. While those woods whichhave alternate layers of small and largepores, such as ash, hickory and oak, aretermed ring-porous woods. Those woodsthat exhibit cellular structure in betweendiffuse- and ring-porous woods areclassified as semi-ringed-porous (or semidiffuse-porous).Black walnut andpersimmon are semi-ringed-porous woods.The primary cause for the difference in thepenetration of preservatives in bothhardwoods and softwoods is the differencein the amount of heartwood and sapwood.Young trees are usually all sapwood. As atree grows older the heart-wood volumeincreases in the center of the tree as thesapwood layers continue to be formed.The sapwood is the “living” portion ofthe wood, which transmits fluids andnutrients between the roots and leaves ofthe tree. The heartwood, which often isdarker in color than the sapwood, no longertransmits fluids; it is inactive.The pores of the heartwood are“blocked” or partially closed with variouspith-like growths called tyloses, or withgum-like materials; while in the conifers thevessel openings become partially or totallyoccluded and thus resistant to the passageof liquids.With most wood species the changefrom sapwood to heartwood increases theresistance to preservative penetration.However, there are exceptions; forexample, both the sapwood and heartwoodof eastern hemlock are resistant to thepenetration of liquids. In addition, there aresome woods, such as red oak, that arerelatively easily penetrated by liquids.7

TECHNICAL ASPECTS ANDA LESSON IN WOODThe general rule is that the treatabilityof heartwood is more difficult thansapwood. Reference Table 1 lists fourgroups of woods, rating the degree ofpenetration difficulty for the various woodspecies.Pith-like growths known as tyloses,develop in the heartwood of somehardwoods. With regard to commercialtimbers used for crossties, tyloses arecommonly found in black locust and thewhite oaks. The influence of tyloses on thepenetration of preservatives into theheartwood is easily illustrated bycomparing penetration in the white oakgroup and the red oaks.By using Table 1, it would be generallyconcluded that all white oaks are difficult topenetrate with preservative; similarly all redoaks can easily be treated. There aresome exceptions to this “rule.” Forexample, chestnut oak (Quercus montana)is a white oak that has few tyloses and thusthe heartwood is treatable. While the redoak known as black jack or jack oak (Q.marilandica) has pores that are closed bytyloses impending the penetration of liquids.Penetration of liquid preservative canoccur in wood in a three directions;– longitudinally, which is the direction thelength of the tree trunk;– radially, which is in the direction of theradius through the center of tree;– tangetially, which is in the direction of theannual rings.With few exceptions, practically allspecies are most easily penetratedlongitudinally. This can be illustrated byvisualizing the wood fibers or vessels as a“bundle of straws.” These vessels or“straws” vary in length, with the endsclosed. “Holes” or pits occur between thevessels, which allow for passage of liquidsfrom one vessel to another. However, thefact remains that liquids move more easilylongitudinally within the vessel rather thanradially or tangentially between the vessels.Even though considerable research wasused to develop the process over manydecades, in practice, the preservativetreatment of wood using pressure methodsis not necessarily an exact science. Thisoccurs due to the variability of wood itselffrom within a given species and between thevarious wood species. Exploring thenumerous reference books cited in theAppendix will confirm that there is an “artand science” to wood treatment.8

TABLE 1TREATABILITY WITH CREOSOTE FOR CROSSTIESHeartwood least difficult to penetrate-MOST TREATABLE (#1)Softwoods• Ponderosa Pine (Pinus ponderosa)• Redwood (Sequoia sempervirens)Hardwoods• American basswood (Tilia americana)• Black tupelo/ black gum (Nyssa sylvatica)• Green ash (Fraxinus pennsylvanica)• River birch (Betula nigra) • Red oaks (Quercus spp.)• Slippery elm (Ulmus rubra) • Sweet birch (Betula lenta)• Water tupelo (Nyssa aquatica) • White ash (Fraxinus americana)Heartwood moderately difficult to penetrate-MODERATELY TREATABLE (#2)Softwoods• Baldcypress (Taxodium distichum)• Douglas fir, coastal (Pseudotsuga menziesii)• Eastern white pine (Pinus strobus)• Jack pine (P. banksiana)• Longleaf pine (P. palustris)• Red pine (P. resinosa)• Shortleaf pine (P. echinata)• Sugar pine (P. lambertiana)• Western hemlock (Tsuga heterophylla)• Loblolly pine (Pinus taeda)Hardwoods• Chestnut oak (Quercus prinus)• Cottonwood (Populus spp.)• Bigtooth aspen (P. grandidentata)• Mockernut hickory (Carya tomentosa)• Silver maple (Acer saccharinum)• Sugar maple (A. saccharum)• Yellow birch (Betula lutea)Heartwood difficult to penetrate-DIFFICULT TO TREAT (#3)Softwoods• Eastern hemlock (Tsuga canadensis)• Engelmann spruce (Picea engelmann)• Grand fir (Abies grandis)• Lodgepole pine (Pinus contorta)• Noble fir (Abies procera)• Western larch (Larix occidentalis)• White fir (Abies concolor)Hardwoods• American sycamore (Platanus occidentalis)• Hackberry (Celtis occidentalis)• Rock elm (Ulmus thomasi)• Yellow poplar (Liriodendron tulipifera)Heartwood very difficult to penetrate-MOST DIFFICULT TO TREAT(#4)Softwoods• Douglas fir, intermountain (Pseudotsuga menziesii)• Northern white cedar (Thuja occidentalis)• Tamarack (Larix laricina)• Western red cedar (Thuja plicata)Hardwoods• American beech (red heartwood) (Fagus grandifolia)• Black locust (Robinia pseudoacacia)• Blackjack oak (Quercus marilandica)• Sweet gum (redgum) (Liquidambar styraciflua)• White Oaks (Quercus spp.)9

THE TREATMENT OF WOOD CROSSTIESWood preservation began in earnestduring the second half of the nineteenthcentury. The first commercial treating plantwas built in Lowell, Massachusetts in 1848.The treating process utilized a water-bornesolution of the inorganic salt mercuricchloride as the wood preservative. Thiswood preservative solution was alsoreferred to as the Kyanizing Process. Theprimary use of this treatment was on woodcrossties for installation on several easternrailroads.In addition, there were two otherinorganic chemical compounds- coppersulfate and zinc chloride- used aswaterborne treatments to preserve wood.Subsequently, it was determined that thesewaterborne mixtures of salt solutions readilyleached out of the wood when placed inexterior exposure conditions where therewas “free running” water.In order to improve the effectiveness ofthese waterborne inorganic chemicalcompounds, the wood was first treated withzinc chloride followed by a treatment withcreosote. In 1906 J.B. Card patented aone step impregnation process with amixture of zinc chloride and creosote. Themixture of zinc chloride/creosote for thetreatment of crossties reached a peak in themiddle 1920’s with the subsequenttreatment process being abandoned in1934.The first full cell creosote treating plantwas built in 1865 in Somerset,Massachusetts. However, there is moresignificance attached to the plant that waserected in 1875 in West Pascagoula,Mississippi. This plant was built by the10Louisville and Nashville Railroad for thetreatment of the various wood materialsincluding crossties that were to be usedwithin the railroad system. It is generallyconsidered that this marked the initialdevelopment of the modern pressure woodtreating plants.The full cell process was also know asthe Bethell Process and was used almostexclusively for all of those early treatments.Because it was not always possible tosatisfactorily treat unseasoned timbers(“green” crossties with high moisture) theBoulton Process was patented in the UnitedStates in 1881. This conditioning method(Boulton Process), or boiling under vacuum,removed free water from the wood cells,which then allowed creosote to beimpregnated into the wood.The full cell process placed themaximum amount of preservative into thewood. Thus, for economic reasons twonew empty cell processes were developed.These empty cell processes were named forthe two individuals who developed andpatented them-Max Rueping in 1902 andC.B. Lowry in 1906.

A BRIEF HISTORY OF WOOD PRESERVATIONThe Rueping and Lowry Processes(empty cell) provide for coating the woodcell with creosote and thus, results in asignificantly smaller retention ofpreservative than that which would havebeen retained with the Bethell Process. Thisempty cell process, with certainmodifications is the primary treatment usedtoday for wood crossties.With additional focus on providing aneconomical treating solution for creosotetreated crossties, such materials as coal tar,water-gas tar and petroleum were mixedwith creosote. These diluents were added toreduce the overall preservative cost of themixture without significantly reducing itseffectiveness. Water-gas tar is no longeravailable and the creosote preservativemanufacturers have minimized the additionof coal tar. The use of heavy petroleum stillcontinues and is mixed with creosote for useby several railroads in arid climates west ofthe Mississippi. Creosote/petroleummixtures are exclusively used by theCanadian railroads for treatment of woodcrossties.The use of creosote and its solutionsreached a peak in 1929 when 203 plantsreported treatment of approximately 360million cubic feet of wood which included 60million crossties. Creosote continued to bethe dominant treatment until shortages of thepreservative occurred during World War II.During the early 1950spentachlorophenol (5-9% concentration) in acarrier-oil began to be used for thetreatment of utility poles. In the decade ofthe 1960s, significantly more leach resistantwaterborne preservative solutions of copperchrome arsenate (CCA), ammoniacalcopper arsenate (ACA) and a formulationrevised to include zinc (ACZA), along withseveral other copper containing preservativeformulations were developed. Thesewaterborne preservatives have had asignificant impact in the increased volume ofpressure treated lumber produced for use inthe consumer markets.That being said, both the railroad and woodtreating industries will continue to look for potentialnew developments for preserving thewood crosstie. Beside creosote and its solutions,two oilborne preservatives – pentachlorophenoland copper naphthenate are allowedfor use in UC4 AWPA Specifications for thetreatment of crossties and switch ties. In recentyears there has been research in the useof borates, both as a pre-treatment and remedialtreatment to improve the service life ofthe wood crossties. The application would bein the southern climate high decay zones.However, creosote and its solutionscontinue to be the preservative of choice inthe treatment of wood that is used by therailroads. The treatment of the woodcrosstie with creosote and its solutions notonly protects the wood from decayorganisms and insects, such as termites, thatwill attack and destroy the wood, it alsoprovides the wood with a degree ofweatherability.Creosote does not readily mix withwater. In fact when wood is treated withcreosote, the water will be repelled. Inaddition, the service life of the treated woodcrosstie is estimated to be over 30 years.With the creosote treated wood crosstiehaving been used since the 1880’s - wellover 100 years - it is not difficult tounderstand the reluctance of railroads to partcompany with such a reliable partner.11

WHY SHOULD WOOD BE TREATED WITH A PRESERVATIVE?Wood always been apreeminent material forconstruction. And rightly so, aswithin North America, as well asother parts of the world, thereexists an abundant timberresource. And, wood is aconstruction material that isrenewable. With such a valuableresource as wood, it is possible tosee why the wood preservingindustry was developed - that is,to conserve and extend the usefulservice life of this resource.Many wood products, andnotably crossties, along with otherwood materials used by therailroad industry, aremanufactured from trees that canbe grown within a reasonable period oftime. For economic and durability reasons,it is important to extend the service life ofwood products. This is the primaryobjective for the use of preservativematerials in the treatment of wood products.By extending the service life of wood, theultimate cost of the product is significantlydecreased and provides for permanence inconstruction.The crosstie industry is a prime exampledemonstrating the benefits of thepreservative treatment of wood. During theearly part of this century, the average servicelife of untreated crossties was approximatelyfive and a half (5 1/2) years. Subsequently,the treatment with creosote extended thatservice life to an estimated average life inexcess of thirty (30) years.To illustrate further a comparison can bemade between treated and untreated redand white oak crossties. Red oak andwhite oak are considered to have similarstructural strength properties. When useduntreated white oak will exhibit an averageservice life of twelve (12) years. Thus, theservice life of this naturally decay-resistantwhite oak material is more than double thatof red oak. However, the service life ismaximized when creosote is impregnatedinto either of these two oak wood groups.12

WHY SHOULD WOOD BE TREATED WITH A PRESERVATIVE?The conclusion should never be drawnthat “naturally durable woods” will giveacceptable service life as a crosstie or asother components of wood construction. Itcan be concluded that wood preservativesincreases life of timber products by as muchas five (5) to eight (8) times.To give the maximum durability, woodpreservatives must penetrate the wood toenough depth to inhibit attack from variouswood destroying organisms that includedecay fungi, insects (i.e. termites) and marineborers. With respect to crossties, decayfungi and termites are usually the organismsof concern. When properly treated with apreservative such as creosote, deteriorationdue to these organisms is essentiallyeliminated.It is also important to note that there arephysical agents that come under the broadclassification of weatherability, that haveeffects on the wood structure. These agentsinclude ultraviolet light, heat, abrasion, andexposure to alternating climatic conditions.These physical agents and their effect onwood can be minimized when the crosstiehas been treated with creosote or an oiltypepreservative.Achieving maximum durability and thusincreasing the service life of the woodcrosstie material, requires preservativetreatment. Historically, the performance ofcreosote and its solutions has beenexemplary. The use of this preservativemakes the wood crosstie a durable andeconomical timber product, produced froma renewable timber resource. Thisunmatched performance is why woodremains the predominant choice by therailroads for building and maintaining the railtrack structure.13

SUMMARY OF THE COMMERCIALTIMBERS USED AS CROSSTIE MATERIALMany wood species are used forrailroad crossties. The most commonwoods used are the oaks and what isknown as the mixed hardwoods, whichinclude the gums, maples, birches, andhickories. Several softwood species suchas Douglas fir, hemlocks, true firs andseveral pine species are also utilized ascrosstie material. The relative suitabilityand use of the various wood species for thecrossties depends on their strengthcharacteristics.The most important strength propertiesconsidered for wood as a crosstie materialare:– bending strength– end-hardness, which is strength incompression parallel to grain; thusindicating the resistance to lateralthrust and spike pull-out– side hardness, which iscompression perpendicular to thegrain; thus indicating resistance toplate-cuttingFor the purpose of this chapter on the“Summary of the Commercial TimbersUsed as Crosstie Material” all of the woodspecies recognized by the AREMA andRTA will be grouped into seven categoriesfor Solid Sawn Wood of Crossties. Thenext chapter on the Engineered CrosstieSystem gives the material and strengthcharacteristics according to the sevenwood species groups listed as follows:– Oaks– Northern Mixed Hardwoods– Southern Mixed Hardwoods– Southern Yellow Pine– Eastern Softwoods– Western Softwoods– Douglas-FirsThe information given for the variouswood species used for crosstie materialsmust be separated according to treatability,performance and strength characteristics.Typically the density, of specific gravity,indicates the strength characteristics of awood species (Figure 1).THE OAKSEach of the seven solid sawn woodcrosstie groups is made up of numerouswood species. For example, the oaks canbe separated into two groups, red andwhite. There are twelve (12) wood specieslisted for the red oaks; and ten (10) for thewhite oaks. Common names and scientificnames are given for each species.Within North America, crosstie fromred and white oaks are primarily producedfrom those states and provinces of theAtlantic coastal region, Southern andAppalachian Mountain regions and thecentral lake state areas (note Table 2 andFigure 1 which highlights geographiclocations for the various wood species).There are two exceptions for the oaks;California black oak (red oak group) andOregon oak (white oak group).14

FIGURE 1Specific Gravity at 12% MCGymnosperms Sp. Gr. Angiosperms1.00.950.900.850.800.75Shagbark Hickory0.700.650.60Black LocustWhite OakBeech, Red OakYellow BirchWhite AshSouthern Yellow PineTamarackDouglas FirWestern HemlockEastern SpruceRedwoodEastern PineWestern Red Cedar0.550.500.450.400.350.30Black WalnutRed GumBlack CherrySassafrasChestnutCatalpaYellow PoplarButternutBasswoodCottonwood15

SUMMARY OF THE COMMERCIALTIMBERS USED AS CROSSTIE MATERIALFor the most part, the separation of thered and the white oak groups indicates theirrelative treatability; the red oaks are easilytreated, while the white oaks are difficult totreat due to the presence of tyloses. Thereare two exceptions to this; in the red oakgroup, blackjack oak has tyloses, thus isdifficult to treat; while chestnut oak, in thewhite oak group, does not have tyloses andis easily treated.The sapwood of both red and whiteoak groups is white in color, between oneand two inches in thickness and is easilytreated. The heartwood of the red oakgroup is generally considered to be reddishbrown. The wood rays are generally broadand conspicuous. The heartwood of thewhite oaks is usually grayish brown and thewood rays are less noticeable. With thetwo exceptions previously referred to, thepresence of tyloses is a distiguishablecharacteristic between the red and whiteoaks.Even though the heartwood of the whiteoaks is difficult to penetrate withpreservatives, it has moderately satisfactorydecay resistance. It is important to properlycondition white oak ties with “an envelope”of preservative in their exterior surfaces.The Oaks as a group are oftenspecified by the railroad industry forcrossties because of their hardness,durability, and excellent service life.NORTHERN & SOUTHERNMIXED HARDWOODSThis is the second and third groups ofcommercial timbers used by the woodtreating industry to produce railroadcrossties. With respect to volume treatedwhen combined together, these two groupsrepresent the second largest amount ofwood used as crosstie material. Aspreviously indicated, it is predominately thegums, maple, birches and hickories thatmake up the total mixed hardwood group ofwoods.As indicated by the section followingthis descriptive summary of the variouswoods used for crossties, there are thirtyfour(34) wood species that make up thenorthern mixed hardwood group (Table3); while there are twenty one (21) differentwood species listed in the southern mixedhardwood group (Table 4). It should be16

SUMMARY OF THE COMMERCIALTIMBERS USED AS CROSSTIE MATERIALnoted that because of the regions in whichthe various species grow, there is “overlap”between the mixed hardwood groups. Forexample both the hickories and maples willbe found growing in northern and southernlocalities - red maple in Pennsylvania andGeorgia.The treatability of the two mixedhardwood groups is given along with theregion from within North America that theyare harvested in Figure 1 and Tables 3 and4. The treatability of the mixed hardwoodsvaries from easy to very difficult. The gums- with exception of sweetgum - and birchesare the most treatable; while both thehickories and maples are consideredmoderately treatable. Both hackberry andsycamore are somewhat more difficult totreat; while the most difficult to treat of themixed hardwood groups is beech, blacklocust, catalpa, mulberry and sweetgum.In even the most difficult woods to treat,the “outer” sapwood can be readily treated,thus creating an “envelope” of preservativeto provide protection to the crosstie. Itshould be noted that an asterisk (*) is givenfor several woods - black cherry, blackwalnut, honey locust, osage orange, etc.There is no scientific data available on thetreatability of the heartwood of these woodspecies. Generally it has been consideredthat the “dark colored” heartwood of thesewoods will not be penetrated by liquidpreservatives and if sapwood is present itwill be treated. Of course the real questionis, “How many black cherry and blackwalnut ties find their way into the treatingcylinder in the future?”The wood species that makeup thenorthern and southern mixed hardwoodgroups have given excellent serviceperformances as railway crosstie material.This is important because the forest resourceconstantly changes and the utilization of allappropriate wood species allows railroadsto improve the overall economics for thewood crosstie. The Canadian railroads forexample have had excellent service life fromhard maple; while several railroads in theUnited States have had more thansatisfactory service from the gums.SOUTHERN YELLOW PINESThere are five (5) species that make upthis group of woods. The wood from thevarious species is quite similar inappearance. The heartwood begins to formwhen the tree is about twenty (20) years old.The treatability (heartwood) and geographiclocation are given in Table 5. Generally thesapwood, which is easily treated, makes upthe greater portion (volume) of the timbersthat are produced.In order to obtain heavy, structurallystrong wood from the southern pines, it isnecessary to specify “high density” material.The visual characteristics (i.e., growth ringsper inch) are sited in the specifications forthe structural material. Dense southern pinehas been used extensively by many railroadsfor bridge ties and timbers with verysatisfactory service performance. However,17

REGION LOCATOR FOR COMMERCIALTIMBERS USED AS A CROSSTIE MATERIAL18

TABLE 2OAKSCommercial Name for Timber (Species) Location TreatabilityRed Oaks• Black Oak (Quercus velutina) I,II,IV 1• Blackjack Oak (Q. marilandica) II,III 4• California Black Oak (Q. kelloggii) VI 1• Northern Pin Oak (Q. ellipsoidalis) IV 1• Northern Red Oak (Q. rubra) I,II,IV 1• Pin Oak (Q. palustis) I,IV 1• Scarlet Oak (Q. coccinea) I,II,IV 1• Shingle Oak (Q. imbricaria) I,III,IV 1• Shumard Oak (Q. shumardii) II,III,IV 1• Southern Red Oak (Q. falcata) I,II 1• Water Oak (Q. nigra) II,III 1• Willow Oak (Q. phellos) II,III 1White Oaks• Bur Oak (Q. macrocarpa) I,III,IV 4• Chestnut Oak (Q. primus) I,IV 2• Chinquapin Oak (Q. muehlenbergii) I,II,III,IV 4• Live Oak (Q. virginiana) II 4• Oregon Oak (Q. garryana) VI 4• Overcup Oak (Q. lyrata) II 4• White Oak (Q. alba) I,II,IV 4• Post Oak (Q. stellata) I,II,III 4• Swamp Chestnut Oak (Q. michauxii) II 4• Swamp White Oak (Q. bicolor) I,IV 419

TABLE 3NORTHERN MIXED HARDWOODSCommercial Name for Timber (Species) Location Treatability• White Elm (Ulmus americana) I,II,III,IV 1• Slippery Elm (U. rubra) I,II,III,IV 1• Hackberry (Celtis occidentalis) I,IV 3• Black Locust (Robinia pseudoacacia) I,II,III 4• Red Mulberry (Morus rubra) I,II,III,IV 4• Hardy Catalpa (Catalpa speciosa) I 4• Honey Locust (Gleditsia triacanthos) II,III,IV *• White Ash (Fraxinus americana) I,II,III,IV 1• Sassafras (Sassafras albidum) I,II,IV *• Persimmon (Diospyros virginiana) I,II,IV 2Hickory• Shagbark (Carya ovata) I,II,IV 2• Shellbark (C. laciniosa) I,IV 2• Pignut (C. glabra) I,II,IV 2• Mockernut (C. tomentosa) I,II,IV 2• Bitternut (C. cordiformis) I,II,IV 2• Pecan (C. illinoensis) II,III,IV 2• Sycamore (Platanus occidentalis) I,II,III,IV 3• Beech (Fagus grandifolia) I,II,IV 4Maple• Sugar (Acer saccharum) I,IV 2• Silver (A. saccharinum) I,II,IV 2• Black (A. nigrum) I,IV 2• Red (A. rubrum) I,II,IV 2• Boxelder (A. negundo) I,II,III,IV,V 2• Black Cherry (Prunus serotina) I,II,III,IV *• Black Walnut (Juglans nigra) I,II,III,IV *• Butternut (Juglans cinerea) I,III,IV *• Yellow Birches (Betula alleghaniensis) I,IV 1• Sweet Birch (Betula lenta) I,II 1• River Birch (Betula nigra) I,II,IV 1• Cottonwood (Populus deltoides) II,III,IV 1• Black Gum (Nyssa sylvatica) I,II,IV 1• Red or Sweet Gum (Liquidambar styraciflua) I,II,III 4• Yellow Poplar (Liriodendron tulipifera) I,II,IV 3• Basswood (Tilia americana) I,IV 120

TABLE 4SOUTHERN MIXED HARDWOODSCommercial Name for Timber (Species) Location Treatability• Cork Elm (Ulmus alata) II 3• Osage Orange (Maclura pomifera) III *• Coffeetree (Gymnocladus dioicus) I,II,IV *• Persimmon (Diospyros virginiana) I,II,IV *Hickory• Shagbark (Carya avata) I,II,IV 2• Pignut (C. glavbra) I,II,IV 2• Mockernut (C. tomentosa) I,II,IV 2• Bitternut (C. cordiformis) I,II,IV 2• Pecan (C. illinoensis) I,III,IV 2• Nutmeg (C. myristicaeformis) II *• Water (C. aquatica) I,III *Maple• Silver (Acer saccharimum) I,II,IV 2• Red (A. rubrum) I,II,IV 2• Boxelder (A. negundo) I,II,III,IV,V 2• Black Cherry (Prumus serotina) I,II,III,IV *• Black Walnut (Juglans nigra) I,II,III,IV *• Butternut (Juglans cinerea) I,III,IV *• River Birch (Betula nigra) I,II,IV 1Guns• Black Gum (Nyssa sylvatica) I,II,IV 1• Red or Sweet Gum (Liquidambar styracifua) I,II,III 4• Water Tupelo (Nyssa aquatica) II 1Footnote * - as indicated no reference could be found for these wood speciesand the treatability of the heartwood21

EXAMPLE HARDWOOD SPECIES SECTIONSSource: Mississippi State University22

SUMMARY OF THE COMMERCIALTIMBERS USED AS CROSSTIE MATERIALconsideration must be given to the fact thatthe southern pines are for the most partlower in density than the oaks and mixedhardwoods and thus will not resist “platecutting”to the same degree. This is thereason that for higher density “mainline”track the more dense woods are specified.EASTERN AND WESTERNSOFTWOODSThe fifth and sixth groups of woods thatare used for crossties are made up ofseveral species from the eastern andwestern regions of North America. Thereare six (6) woods from the eastern regionand thirteen (13) species from the westernarea. Location of growth and treatabilityinformation are given in Tables 6 and 7 forthe respective two groups of softwoods.Of the eastern softwoods, whitecedars, fir, hemlock, spruces and tamarackhave very limited actual use for crossties ina mainline track. There is undoubtedlysome use of eastern softwoods in thoseregions near the local harvest area.Timbers would be used for the constructionof secondary track and bridge timbers. Allof the eastern softwoods are considereddifficult to treat with preservatives such ascreosote. Even the sapwood of easternhemlock is difficult to treat and with thisspecies incising is necessary, not only toassist in drying the crosstie, but to improvethe penetration of preservatives.DOUGLAS-FIRThe final timber used for wood crosstiesis Douglas-fir. It is the only species with thedata for growth location and treatabilitygiven in Table 8. There are however, twotypes of Douglas-fir - Coastal andIntermountain. The coastal variety isconsidered moderately treatable; while theintermountain type is most difficult to treat.Treatment with creosote of Douglas-firrequires incising ties and timbers foracceptable preservative penetration.This wood species is one that isreferred to as having “thin-sapwood”;usually not more than one-inch in thickness,but in second-growth trees of commercialsize the sapwood may be as much as threeinches.The range of Douglas-fir extendsfrom the Rocky Mountains to the Pacificcoast and from Mexico to central BritishColumbia. Considerable quantities of thiswood species finds its way into railroadcrossties for use in track primarily inCanada and the western United States.Douglas-fir timber has also been usedextensively for bridge timbers.23

TABLE 5SOUTHERN YELLOW PINESCommercial Name for Timber (Species) Location TreatabilityShortleaf Pine (Pinus echinata) II,III 2Loblolly Pine (P. taeda) II,III 2Longleaf Pine (P. palustris) II,III 2Slash Pine (P. elliottii) II,III 2Virginia Pine (P. virginiana) II,III 2TABLE 6EASTERN SOFTWOODSCommercial Name for Timber (Species) Location TreatabilityEastern Spruces (Picea spp.) I,II,IV 3Tamarack (Larix laricina) I,II,IV 3Eastern Hemlock (Tsuga canadensis) I,II,IV 3Balsam Fir (Abies balsamea) I,II,IV 3Northern White Cedar (Thuja occidentalis) I,II,IV 3Atlantic White Cedar (Chamaecyparis thyoides) I,II,IV 324

TABLE 7WESTERN SOFTWOODSCommercial Name for Timber (Species) Location TreatabilityWestern White Pine (Pinus monticola) III,V,VI,VII *Limber Pine (P. flexilis) III,V,VI,VII *Jeffery Pine (P. jeffreyi) III,V,VI,VII *Lodgepole Pine (P. contortai) III,V,VI,VII 3Ponderosa Pine (P. ponderosa) III,V,VI,VII 1Engelmann Spruce (Picea engelmannii) III,V,VI,VII 3Western Larch (Larix occidentalis) III,V,VI,VII 3Port Orford Ceder (Chamaecyparis lawsoniana) III,V,VI,VII *White Fir (Abies concolor) III,V,VI,VII 3Grand Fir (Abies grandis) III,V,VI,VII 3Redwood (Sequoia sempervirens) III,V,VI,VII 1Western Hemlock (Tsuga heterophylla) III,V,VI,VII 2Western redceder (Thuja plicata) III,V,VI,VII 4Footnote * - as indicated no reference could be found for these wood speciesand the treatability of the heartwoodTABLE 8DOUGLAS FIRCommercial Name for Timber (Species) Location TreatabilityCoastal (Pseudotsuga menzeisii) VI 2Intermountain (Pseudotsuga menzeisii) VI 425

EXAMPLE SOFTWOOD SPECIES SECTIONSSource: Mississippi State University26

THE ENGINEERED WOOD CROSSTIEIn an earlier section of this booklet,“Why Should Wood Be Treated WithPreservative?”, the statement wasbrought forward that wood is the onlyconstruction material that is a renewableresource. History books and variousliterature citations make numerousreferences to wood as a long standingmaterial of construction. To illustrate a fewexamples concerning the importance ofwood in the development of this country,a few brief statements are offered.* The average early frontier log cabinsrequired about 80 logs, as well assmaller timbers. Wood roof shakesand wood pegs were used to holdthe structure together.* During the first part of the 18thcentury settlers in the ConestogaValley of Pennsylvania built awagon almost completely of wood.The Conestoga wagons transportedfreight supplies throughout theeastern part of the country.* Boats, bridges and roads were madeof wood. The “wooden plank” roadran between New York and Newarkover wet marshland. During the19th century two thousand miles ofwood roads were built in the statesof New York, Michigan, Wisconsinand other Midwestern states hadextensive systems. In some states,such as Alabama, plank roadsdelayed the coming of the railroads.* Wood was the predominate materialof construction even into the firstpart of the 20th century. Becausewood was plentiful and the vasttimber resource seemed unending,the production and preservativetreatment of crossties for the railroadindustry became well established.The hand hewn-tie and subsequentlythe sawn-tie were producedaccording to standard cross-sectionaldimensions (inches) - 6x7, 7x7, 7x8and 7x9. Length of the woodcrosstie depended on that specifiedby the railroad; eventually movingto an acceptable standard length ofeither eight and one half or nine feet.The wood crosstie thus has specificphysical dimensions with specificmeasurements. In addition, thespecifications for timber crossties as quotedfrom the American Railway Engineering andMaintenance of Way Association(AREMA) Manual for Railway Engineering,Section 3.1.1.2.1 General Quality:“Except as hereinafter provided,all ties shall be free from anydefects that may impair theirstrength or durability as crossties,such as decay, large splits, largeshakes, slanting grain, or large ornumerous holes or knots.”27

THE ENGINEERED WOOD CROSSTIETo further emphasize the importanceplaced on physical characteristics a quotefrom the same AREMA Manual is takenfrom Section 3.2.1.2.2 Resistance to Wear:“When so ordered, ties from needleleaved trees shall be of compactwood throughout the top fourth ofthe tie, where any inch of anyradius from the pith shall have sixor more rings of annual growth.”The point of this dialogue is that wood is avery important structural material, and whenused solely for crossties, historically, thephysical characteristics have been the mostimportant consideration.The wood crosstie is now thought of asthe Engineered Wood Crosstie with itsown set of specifications based on structuralstrength test data. Given in Table 9 are thestrength characteristics for the seven types ofsolid sawn woods that are used in theproduction of crossties:— Oaks— Northern Mixed Hardwoods— Southern Mixed Hardwoods— Southern Yellow Pine— Eastern Softwoods— Western Softwoods— Douglas-FirThis new specification for timber ties isunder development by The Railway TieAssociation (RTA), in cooperation withAREMA, to provide data to the engineerwho desires to use the data in the structuraldesign of the “rail track system”. Inaddition, the RTA will be working incooperation with those manufacturingfacilities to provide structural strengthinformation for Composite WoodMaterials.Two examples of Composite Wood Materialswould be glue laminated lumber andparallel strand lumber laminated products.Currently one example of a commercial materialis Trus-Joist’s Parallam ®. These fabricatedproducts can be made from severaldifferent wood species and engineered tomeet specific strength characteristics.28

THE ENGINEERED WOOD CROSSTIE29

MATERIAL PROPERTIES OF SOLID SAWNWOOD CROSSTIE MATERIALSWood is an extremely versatile andeffective material for use as a railroadtrack crosstie. However, the keyproperties of wood will vary with thewood species. In order to allow for thepotential use of a broad range of types,the wood tie properties presented in thissection have been divided into seven (7)categories of wood as given in Table 10.For each category a representativewood species was used. The materialproperties given to Table 9 represent a“minimum” value for each category(useless otherwise noted). This is to allowfor the use of these material properties in“design” calculations. The value arebased on a collection of material properlydata, to include both handbook sampledata and full tie test data (with adjustmentto compensate for the differences).An explanation for the wood properlyvalues given to Table 9 are as follows:* Dimensions are based on theAREMA specification that allowsa 1/4-inch reduction in width anddepth.* Volume is calculated based ondimensions.* Density is based on 40% moisturecontent (as determined from theoven-dry volume). Seven (7) lbs./cu.ft. of creosote was added tothe density and the total reducedby 10% to account for variationsin values in the material propertytable and in the treatment process.* Weight is the density multiplied bythe volume.* Moment of inertia is calculatedbased on the defined dimensionsand rectangular cross-section.* Section modulus was calculatedfrom dimensions and rectangularcross-section.* Modulus of Elasticity (MOE) isbased on “green” values plus 10%of the difference between the greenand the dry values (to account forthe fact that the outside of the tie isdrier than the interior of the tie).Ninety percent (90%) of thecalculated value is taken todetermine a “minimum” value fordesign purposes.* Modulus of Rupture (MOR) isbased on “green” values plus 10%of the difference between the greenand the dry values (to account forthe fact that the outside of the tie isdrier than the interior of the tie).Ninety percent (90%) of thecalculated value is taken todetermine a “minimum” value fordesign purposes.* Rail Seat Compression Test isbased on “green” values plus 10%of the difference between the greenand dry values (to account for thefact that the outside of the tie isdrier than the interior of the tie) andbased on handbook data forCompression Perpendicular to the30

MATERIAL PROPERTIES OF SOLID SAWNWOOD CROSSTIE MATERIALSGrain. Ninety percent (90%) of thecalculated value is taken todetermine a “minimum” value fordesign purposes.* Material Surface Hardness Test isbased on “green” values plus 10%of the difference between the greenand the dry values (to account forthe fact that the outside of the tie isdrier than the interior of the tie) andbased on handbook data forHardness Perpendicular to theGrain. Ninety percent of thecalculated value is taken todetermine a “minimum” value fordesign purposes.* Static Bending Strength is atheoretical calculation based on theMOR and the section modulus.* Flexibility (which is a moreappropriate term than stiffness-loaddeflection) is a theoreticalcalculation based on a applied loadof 10,000 lbs. And a sixty (60) inchsupport spacing.* Lateral resistance values are basedon field tests taken by USDepartment of Transportation,Volpe Transportation SystemsCenter, using single tie push tests.Results are based on “minimum”value for consolidated track. Toaccount for differences in density(weight), 50% lateral resistance wasvaried linearly as a function of theweight of the ties, using mixedhardwoods as the base reference.To account for the non-weightrelated component of lateralresistance (due to side and endeffects that do not change withweight) only 50% of the lateralresistance was varied with weight,with the remaining 50% heldconstant.31

TABLE 10Crosstie CategoryWood SpeciesOakNorthern Mixed HardwoodsSouthern Mixed HardwoodsSouthern PineWestern SoftwoodsEastern SoftwoodsDouglas-firSouthern red oakWhite birchSilver mapleShortleaf pinePonderosa pineEastern hemlockCoastal Douglas-firTHE ABOVE WOOD SPECIES WERE USED TO CALCULATE THECATEGORY VALUES FOR STRENGTH PROPERTIES IN TABLE 932

HYBRID ENGINEEREDWOOD CROSSTIE MATERIALSThe solid sawn creosote treated woodcrosstie, which was discussed earlier inthis section, has an average service life ofwell over thirty five (35) years. To thispresent day, it continues to be the majortrack component that binds the steel railstogether. These solid sawn treated woodcrossties will undoubtedly continue as thepreferred material of choice by therailroads.In the early part of this century thecrosstie material used by the railroadsprogressed form an untreated hand-hewntie to the creosote treated solid sawn tie.So it may be fitting that as we move into anew century, there are new progressionsin the field of wood technology occurring.The Railway Tie Association, through itsResearch and Development Committee,continues to take a leadership role incoordinating significant research projectsin this area. These include the evaluationof: under-utilized wood species, dowellaminatedwood, glue-laminated wood,parallel oriented wood fiber and fiberreinforced laminated wood for use ascrosstie material.For lack of a better term, all of thesematerials should be called “hybrid” woodproducts. They bring together structuraladhesives, polymeric fibers, and wood invarious combinations to provide anengineered wood structurally suitable foruse as crosstie, switch tie and bridgetimber materials. These new productsmay provide advantages over the existingmaterials for crosstie. It is a fact that someof these hybrid products are already in useby the railroads in widely varyingapplications.Given in Table 10 are structural data forthe solid sawn and engineered woodproducts. It must, however, be recognizedthat because these are “engineered” woodproducts – i.e., glue-laminated timbers, etc.– the strength characteristics can be“adjusted” by varying the density, woodspecies and the orientation/ use of woodmaterials. Because of this it is not possibleto provide structural test data for all thevariations. However, one can assume thatthe goal is to “engineer in” strengthproperties that will be greater that solidsawn products, while keeping economicsunder consideration.Wood is a renewable resource but thelarger old growth timber, once abundant, isincreasing less accessible to harvest.Second-growth and third-growth trees thatare currently harvested are typically smallerin diameter. While the majority of crosstiesproduced will remain solid sawn materialfor the foreseeable future, the changesoccurring in managing the resource willrequire increasing utilization of alternativespecies and engineered hybrid woodproducts. As the demand for crosstiecontinues, it is realistic to expect that theengineered hybrid wood crosstie has asignificant future.33

APPENDIXSpecifications for Crosstie Timbers 35-37American Wood-Preservers’ Association Preservative 39-42Standards, P1/P13, P2, P3 and P4American Wood-Preservers’ Association Use Category System 43-45Standard UC4, “Crossties and Switch Ties—Preservative Treatment by Pressure Processes”34

SPECIFICATIONS FORTIMBER CROSSTIES(Latest Revision as of January 2003)These specifications were arrived at by a jointcommittee of the Railway Tie Association and theAmerican Railway Engineering and Maintenance of WayAssociation, and are identical to Chapter 30 of the AREMAManual for Railway Engineering. This publication doesnot include numerous other requirements of AREMAspecifications.AREMA Manual Chapter 30 is a multi-page workcovering many additional practices regarding crosstiesand switch ties, including adzing, boring, trimming,branding, application of anti-splitting devices, log storage,air seasoning, treatment, and care after preservativetreatment. It is available from AREMA PublicationsDepartment, 8201 Corporate Drive, Suite 1125, Landover,MD 20785, for $125 (non-member price is $150) for theindividual Chapter 30 or $425 (non-member price is $650)for the complete Manual. Prices are subject to changewithout notice.3.1.1 SPECIFICATIONS FOR TIMBER CROSSTIESNOTE: It is recommended for West Coast speciesthat W.C.L.B. Grading Rules apply.3.1.1.1 MATERIAL3.1.1.1.1 Kinds of Wood*Before manufacturing ties, producers shall ascertainwhich of the following kinds of wood suitable for crosstieswill be accepted:Ashes Gums OaksBeech Hackberries PinesBirches Hemlocks PoplarsCatalpas Hickories RedwoodsCherries Larches SassafrasDouglas fir Locusts SprucesElms Maples SycamoresFirs (true) Mulberries Walnuts*Each railway will specify only the kind of wood itdesires to use.Others will not be accepted unless specially ordered.3.1.1.2 PHYSICAL REQUIREMENTS3.1.1.2.1 General QualityExcept as hereinafter provided, all ties shall be freefrom any defects that may impair their strength ordurability as crossties, such as decay, large splits, largeshakes, slanting grain, or large or numerous holes or knots.3.1.1.2.2 Resistance to WearWhen so ordered, ties from needle-leaved trees shallbe of compact wood throughout the top fourth of the tie,where any inch of any radius from the pith shall have sixor more rings of annual growth.3.1.1.3 DESIGNSize Categories for 7" & 6" Crossties 1" of WaneAllowed —— 20% Square 7" x 8" Allowed3.1.1.3.1 DimensionsTies shall be 8'-0", 8'-6", or 9'-0" long as specified bythe customer. Thickness, width, and length specified areminimum dimensions for green ties. Dry or treated tiesmay be 1/4" thinner or narrower than the specified sizes.Ties exceeding these dimensions by more than 1" shall berejected. The grade of each tie shall be determined at thepoint of most wane on the top face of the tie within the railbearingareas. The rail-bearing areas are those sectionsbetween 20" and 40" from the center of the tie. The topof the tie shall be the narrowest face and/or the horizontalface farthest from the heart or pith center.All rail-bearing areas shall measure as follows: 7"grade crossties shall be 7" x 9" in cross section with amaximum of 1" of wane in the top rail-bearing areas. Amaximum of 20% of the ties in any given quantity maybe square-sawn 7" x 8" in cross section with no wane in therail-bearing areas. A 6" grade tie shall be 6" x 8" in crosssection with a maximum of 1" of wane permitted in thetop rail-bearing areas. For both 6" and 7" grade ties, waneshall be permitted on the bottom face so long as it does notexceed 1" at any given point.3.1.1.4 INSPECTION3.1.1.4.1 PlaceTies will be inspected at suitable points as specified inthe purchase agreement of the railway.3.1.1.4.2 MannerInspectors will make a reasonably close examinationof the top, bottom, sides and ends of each tie. Each tie willbe judged independently, without regard to the decisionson others in the same lot. Rafted or boomed ties toomuddled for ready examination will be rejected. Tieshandled by hoists will be turned over as inspected, at theexpense of the producer.3.1.1.4.3 DecayDecay is the disintegration of the wood substance dueto the action of wood destroying fungi. “Blue stain” is notdecay and is permissible in any wood.3.1.1.4.4 HolesA large hole is one more than 1/2" in diameter and 3"deep within, or more than 1/4 the width of the surface onwhich it appears and 3" deep outside, the sections of thetie between 20" and 40" from its middle. Numerous holesare any number equaling a large hole in damaging effect.Such holes may be caused in manufacture or otherwise.3.1.1.4.5 KnotsWithin the rail-bearing areas, a large knot is one havingan average diameter more than 1/3 the width of the surfaceon which it appears, but such a knot will be allowed if it islocated outside the rail-bearing areas. Numerous knotsare any number equaling a large knot in damaging effect.3.1.1.4.6 ShakeA shake is a separation along the grain, most of whichoccurs between the rings of annual growth.3.1.1.4.8 ChecksA check is a separation of the wood due to seasoningwhich appears on one surface only. Do not count the endas a surface. Ties with continuous checks whose depth ina fully seasoned and/or treated tie is greater than 1/4 thethickness and longer than 1/2 the length of the tie will berejected.3.1.1.4.9 Slope of GrainExcept in woods with interlocking grain, a slant in grainin excess of 1 in 15 will not be permitted.3.1.1.4.10 Bark SeamsA bark seam or pocket is a patch of bark partially orwholly enclosed in the wood. Bark seams will beallowed provided they are not more than 2" below thesurface and/or 10" long.3.1.1.4.11 Manufacturing DefectsAll ties must be straight, square-sawn, cut square at theends, have top and bottom parallel, and have bark entirelyremoved. Any ties which do not meet the followingcharacteristics of good manufacture will be rejected:a. A tie will be considered straight when astraight line from a point on one end to acorresponding point on the other end is nomore than 1-1/2" from the surface at allpoints.b. A tie is not well-sawn when its surfaces arecut into with score marks more than 1/2"deep, or when its surfaces are not even.c. The top and bottom of a tie will be consideredparallel if any difference at the sides or endsdoes not exceed 1/8".d. For proper seating of nail plates, tie endsmust be flat, and will be considered squarewith a sloped end of up to 1/2", which equalsa 1 in 20 cant.The procedure illustrated in the above diagrams shallbe used in determining the length of a shake. One whichis not more than 1/3 the width of the tie will be allowed,provided it does not extend nearer than 1" to any surface.3.1.1.4.7 SplitA split is a separation of the wood extending fromone surface to an opposite or adjacent surface. Do notcount the end as a surface when measuring the length ofa split. In unseasoned crossties, a split no more than 1/8"wide and/or 4" long is acceptable. In a seasoned crosstie,a split no more than 1/4" wide and/or longer than the widthof the face across which it occurs is acceptable. Inseasoned crossties, a split exceeding the limit is acceptable,provided split limitations and anti-splitting devices areapproved by the buyer and properly applied.35

SPECIFICATIONS FORTIMBER SWITCH TIES(Latest Revision as of January 2003)These specifications were arrived at by a jointcommittee of the Railway Tie Association and theAmerican Railway Engineering and Maintenance of WayAssociation, and are identical to Chapter 30 of the AREMAManual for Railway Engineering.AREMA Manual Chapter 30 is a multi-page workcovering many additional practices regarding crosstiesand switch ties, including adzing, boring, trimming,branding, application of anti-splitting devices, log storage,air seasoning, treatment, and care after preservativetreatment. It is available from AREMA PublicationsDepartment, 8201 Corporate Drive, Suite 1125, Landover,MD 20785, for $125 (non-member price is $150) for theindividual Chapter 30 or $425 (non-member price is $650)for the complete Manual. Prices are subject to changewithout notice.3.2.1 SPECIFICATIONS FOR TIMBERSWITCH TIESNOTE: It is recommended for West Coast speciesthat W.C.L.B. Grading Rules apply.3.2.1.1 MATERIAL3.2.1.1.1 Kinds of WoodBefore manufacturing ties, producers shall ascertainwhich of the following kinds of wood suitable for switchties will be accepted:Ashes Firs (true) MaplesBeech Gums OaksBirches Hemlocks PinesCherries Hickories RedwoodDouglas Fir Larches SprucesElms Locusts WalnutsOthers will not be accepted unless specially ordered.3.2.1.2 PHYSICAL REQUIREMENTS3.2.1.2.1 General QualityExcept as hereinafter provided, all ties shall be freefrom any defects that may impair their strength ordurability as switch ties, such as decay, large splits, largeshakes, slanting grain, or large or numerous holes or knots.3.2.1.2.2 Resistance to WearWhen so ordered, ties from needle-leaved trees shallbe of compact wood throughout the top fourth of the tie,where any inch of any radius from the pith shall have 6 ormore rings of annual growth.3.2.1.3 DESIGN3.2.1.3.1 DimensionsAll unseasoned or green switch ties shall measure incross section a minimum of 7" in side thickness and 9" inface width. A maximum of 1" of wane is allowed on thetop or bottom faces within the rail-bearing area, which isdefined as the section between 12" from each end of thetie. Seasoned or treated switch ties may be 1/4" under thespecified dimensions for thickness and width, or not morethan 1" over the specified dimensions. Lengths and lengthtolerances shall be specified by the customer.36All thickness and face width dimensions apply to therail-bearing area. All determinations of face width shallbe made on the top of the switch tie, which is the narrowesthorizontal face. If both horizontal faces are of equal width,the top shall be that face with the narrowest or no heartwood.3.2.1.4 INSPECTION3.2.1.4.1 PlaceTies shall be inspected at suitable points as specified inthe purchase agreement of the railway.3.2.1.4.2 MannerInspectors will make a reasonably close examinationof the top, bottom, sides and ends of each tie. Each tie willbe judged independently, without regard for the decisionson others in the same lot. Ties too muddied for readyexamination will be rejected. Ties handled by hoists willbe turned over as inspected, at the expense of the producer.3.2.1.4.3 DecayDecay is the disintegration of the wood substance dueto the action of wood destroying fungi. “Blue stain” is notdecay and is permissible in any wood.3.2.1.4.4 HolesA large hole is one more than 1/2" in diameter and 3"deep within, or more than 1/4 the width of the surface onwhich it appears and 3" deep outside, the section of the tiebetween 12" from each end of the tie. Numerous holes areany number equaling a large hole in damaging effect.Such holes may be caused in manufacture or otherwise.3.2.1.4.5 KnotsA large knot is one whose average diameter exceeds 1/4 the width of the surface on which it appears; but such aknot may be allowed if it occurs outside the section between12" from each end of the tie. Numerous knots are anynumber equaling a large knot in damaging effect.3.2.1.4.6 ShakeOne which is not more than 1/3 the width of the tie willbe allowed. The procedure and diagrams shown in 3.1.1.4.6for crossties shall also apply to switch ties for measuringthe length of a shake.3.2.1.4.7 SplitA split is a separation of the wood extending from onesurface to an opposite or adjacent surface. Do not countthe end as a surface when measuring the length of a split.In unseasoned or green switch ties, a split no more than1/8" wide and/or 5" long is acceptable. In a seasoned ortreated switch tie, a split no more than 1/4" wide and/orlonger than the width of the face across which it occurs isacceptable. A split exceeding the limit is acceptable,provided split limitations and anti-splitting devices areapproved by the buyer and properly applied.3.2.1.4.8 ChecksA check is a separation of the wood due to seasoningwhich appears on one surface only. Do not count the endas a surface when measuring the length of a check. Tieswith continuous checks whose depth in a fully seasonedand/or treated tie is greater than 1/4 the thickness and longerthan 1/2 the length of the tie will be rejected.3.2.1.4.9 Slope of GrainExcept in woods with interlocking grain, a slope of grainin excess of 1 in 15 will not be permitted.3.2.1.4.10 Bark SeamsA bark seam or pocket is a patch of bark partially orwholly enclosed in the wood. Bark seams will be allowedprovided they are not more than 2" below the surface and/or 10" long.3.2.1.4.11 Manufacturing DefectsAll ties must be straight, square-sawn, cut square at theends, have top and bottom parallel, and have bark entirelyremoved. Any ties which do not meet the followingcharacteristics of good manufacture will be rejected:a. A tie will be considered straight when a straight linefrom a point on one end to a corresponding point on theother end is no more than 2" from the surface at all points.b. A tie is not well-sawn when its surfaces are cut intowith score marks more than 1/2" deep, or when its surfacesare not even.c. The top and bottom of a tie will be considered parallelif any difference at the sides or ends does not exceed 1/4".d. For proper seating of nail plates, tie ends must beflat, and will be considered square with a sloped end of upto 1/2", which equals a 1 in 20 cant.3.2.1.5 DELIVERY3.2.1.5.1 On Railway PremisesTies shall be delivered and stacked as specified in thepurchase agreement of the railway. If ties are to beinspected, they must be placed so that all ties are accessibleto the inspector.3.2.1.5.2 Risk, RejectionAll ties are at the owners risk until accepted. Allrejected ties shall be removed within one month afterinspection.3.2.1.5.3 Species Groups for Seasoning andTreatingSwitch ties shall be grouped as shown below for airseasoningor artificial seasoning and subsequentpreservative treatment. Only the kinds of wood named ina group may be processed together.Group TaGroup TbBlack Locust Douglas Fir RedwoodHoney Locust Firs (True) SprucesRed OaksHemlocksWhite OaksLarchesBlack WalnutPinesGroup TcGroup TdGums Ashes ElmsBeech Hard MaplesBirches HickoryCherries Soft MaplesWhite Walnut3.2.1.6 SHIPMENTTies forwarded in cars or vessels shall be separatedtherein according to the above groups, and also accordingto the above sets or lengths if inspected before loading, oras may be stipulated in the contract or order for them.

SPECIFICATIONS FOR TIMBERINDUSTRIAL GRADE CROSSTIES(Latest Revision as of January 2003)These specifications were arrived at by a jointcommittee of the Railway Tie Association and theAmerican Railway Engineering and Maintenance of WayAssociation, and are identical to Chapter 30 of the AREMAManual for Railway Engineering.AREMA Manual Chapter 30 is a multi-page workcovering many additional practices regarding crosstiesand switch ties, including adzing, boring, trimming,branding, application of anti-splitting devices, log storage,air seasoning, treatment, and care after preservativetreatment. It is available from AREMA PublicationsDepartment, 8201 Corporate Drive, Suite 1125, Landover,MD 20785, for $125 (non-member price is $150) for theindividual Chapter 30 or $425 (non-member price is $650)for the complete Manual. Prices are subject to changewithout notice.3.9.1 SPECIFICATIONS FOR TIMBERINDUSTRIAL GRADE CROSSTIES3.9.1.1 Material3.9.1.1.1 Kinds of WoodBefore manufacturing ties, producers shall ascertainwhich of the following kinds of wood suitable for crosstieswill be accepted:Ashes Gums OaksBeech Hackberries PinesBirches Hemlocks PoplarsCatalpas Hickories RedwoodsCherries Larches SassafrasDouglas Fir Locusts SprucesElms Maples SycamoresFirs (true) Mulberries Walnuts3.9.1.2 GeneralAll procedures regarding quality, manufacture,inspection, shipment, and delivery will comply fully withthose specified for grade crossties in Part 1, GeneralConsiderations unless excepted by information containedin this part.3.9.1.3 Classification and DesignThe following sizes, lengths, minimum faces andtolerances are allowed:Grade Dimensions Minimum Faces Allowed6" IG 6"x 8" x 8’0"/8’6" 6" face on top or bottom7" IG 7"x 8" x 8’0"/8’6" 6" face on top or bottom7" IG 7"x 9" x 8’0"/8’6" 6" face on top or bottomThe above minimum face requirements apply to therail-bearing areas, which are the areas between 20" and40" from the middle of the industrial grade crossties.Outside the rail-bearing areas, wane will be limited to halfthe face width on the top or bottom of the tie. The gradeof each tie shall be determined at the point of most wane,on the top or bottom, within the rail-bearing areas. (Thetop is defined as the horizontal face farthest from theheartwood or pith center).Dry or treated ties may be 1" narrower or 1/2" thinnerthan the specified sizes. Thickness and width may not varymore than 1" from end to end. The tie body may be out ofsquare by no more than 1" throughout the length. Tielength may vary from +1" to -3" for the length specified.3.9.1.4 DEFINITION OF DEFECTS3.9.1.4.1 WaneWane is defined as bark or the lack of wood (see 3.9.1.3for allowance).3.9.1.4.2 DecayA decayed knot greater than 3/4" in diameter will berejected within the rail-bearing area. Also, slight incipientdecay may be allowed if the tie, as a whole, is basicallyof good quality. Decay is allowed outside the rail-bearingarea if the decayed area does not exceed 2" in diameter.Ties with decay up to 2" in diameter appearing in both endsof the tie will be rejected.3.9.1.4.3 HolesTies having holes on any surface within the rail-bearingareas that are greater than 1/2" in diameter or greater than3" deep will be rejected. Holes on any surface outside therail-bearing areas which are greater than 3" in diameter ordeeper than 4" will be rejected.3.9.1.4.4 KnotsA knot greater than 3" in diameter within the rail-bearingarea will not be permitted.3.9.1.4.5 ShakesSeasoned or treated ties with shakes having a length onthe cross-section greater than 5" or extending to within 1"of any surface shall be rejected. Length measurementsshall be made using 3.1.1.4.6 as a guide.3.9.1.4.6 SplitsA split is a separation of wood extending from onesurface to an opposite or adjacent surface – not countingthe ends as a surface. A seasoned or treated tie with a splitgreater than 1/2" wide or 11" long will be rejected with orwithout a nail plate.3.9.1.4.7 ChecksA check is a separation of wood due to seasoning whichappears on the surface only – not counting the end as asurface. Season checks greater than 2" deep or 3/4" wideshall be rejected as industrial grade ties.3.9.1.4.8 Cross or Spiral GrainExcept in species with interlocking grain, ties havingcross, slant, or spiral grain greater than 2" in 15" of lengthwill be rejected.3.9.1.4.9 Bark SeamsBark seams will not be acceptable if more than 2" deepor more than 10" long anywhere in the tie.3.9.1.4.10 Manufacturing DefectsAll ties must be straight and have top and bottomparallel. Any ties which do not meet the followingcharacteristics of good manufacture will be rejected:a. A tie will be considered straight when a straight linefrom a point on one end to a corresponding point on theother end is no more than 2" from the surface at all points.b. The top and bottom of a tie will be considered parallelif any difference at the sides or ends does not exceed 1".c. A tie is not well-sawn when its surfaces are cut withscore marks more than 1" deep.d. For proper seating of nail plates, tie ends must beflat, and will be considered square with a sloped end of upto 1/2", which equals a 1 in 20 cant.37

AMERICAN WOOD-PRESERVERS’ ASSOCIATIONPRESERVATIVE STANDARDS, P1/P13, P2, P3 AND P4PAGES 39-42AMERICAN WOOD-PRESERVERS’ ASSOCIATIONPRESERVATIVE COMMODITY STANDARD UC4“USER SPECIFICATION FOR TREATED WOOD” and T1-05“PROCESSING AND TREATMENT STANDARD”PAGES 43-45ALL AMERICAN WOOD-PRESERVERS’ASSOCIATION SPECIFICATIONS PRINTED WITH PERMISSION38

AMERICAN WOOD-PRESERVERS’ ASSOCIATION STANDARD(This Standard is promulgated according to a consensus procedure and is under the jurisdiction of AWPA Subcommittee P-3)P1/P13-01STANDARD FOR CREOSOTE PRESERVATIVENote: AWPA Standard P1/P13-01 consists of one page.1. The creosote shall be a distillate derived entirely from tar produced by the carbonization of bituminous coal.2. The new material and the material in use in treating solutions shall conform to the following detailed requirements.2.1 Water, % by Volume2.2 Matter Insoluble in Xylene, % by wt.2.3 Specific Gravity at 38 O C Compared to water at 15.5 O C:Whole CreosoteFraction 235-315 O CFraction 315-355 O C2.4 Distillation: The distillate, % by wt. on a waterfree basis, shall be within the following limits:Up to 210 O CUp to 235 O CUp to 270 O CUp to 315 O CUp to 355 O CNew MaterialMaterial In UseNot Not Not NotLess More Less MoreThan Than Than Than–– 1.5 –– 3.0–– 0.5 –– 1.51.070 –– 1.070 ––1.028 –– 1.028 ––1.100 –– 1.100 –––– 2.0 –– 2.0–– 12.0 –– 12.010.0 40.0 10.0 40.040.0 65.0 40.0 65.065.0 77.0 65.0 77.03.0 Tests to establish conformance with the foregoing requirements shall be made in accordance with the standardmethods of the American Wood-Preservers’ Association. (See Standard A1.)Standard P1/P13-95 was reaffirmed in 2000 and 2001 with minor editorial corrections.The title was amended in 1999, 2000 and 2001.39

AMERICAN WOOD-PRESERVERS’ ASSOCIATION STANDARD(This Standard is promulgated according to a consensus procedure and is under the jurisdiction of AWPA Subcommittee P-3)P2-01STANDARD FOR CREOSOTE SOLUTION1. The material shall be a pure coal tar product derived entirely from tar produced by the carbonization of bituminous coal.It may either be a coal tar distillate or a solution of coal tar in coal tar distillate.2. The new material and the material in use in treating operations shall conform to the following detailed requirements.2.1 Water, % by Volume2.2 Matter Insoluble in Xylene, % by wt.2.3 Specific Gravity at 38 O C Compared to water at 15.5 O C:Whole CreosoteFraction 235-315 O CFraction 315-355 O C2.4 Distillation: The distillate, % by wt. on a waterfree basis, shall be within the following limits:Up to 210 O CUp to 235 O CUp to 315 O CUp to 355 O CNew MaterialMaterial In UseNot Not Not NotLess More Less MoreThan Than Than Than–– 1.5 –– 3.0–– 3.5 –– 4.51.080 1.130 1.080 1.1301.025 –– 1.025 ––1.085 –– 1.085 –––– 5.0 –– 5.0–– 25.0 –– 25.032.0 –– 32.0 ––52.0 –– 52.0 ––3.0 Tests to establish conformance with the foregoing requirements shall be made in accordance with the standard methodsof the American Wood-Preservers’ Association. (See Standard A1.)Proceedings: 1917, 1918, 1921, 1923, 1933,1935, 1936, 1941, 1942, 1947, 1953, 1954, 1957, 1958, 1968, 1985, 1989,1995, 1998 and 2001.Standard P2 was reaffirmed in 1995 with minor editorial correction; and amended in 1998 to remove, without prejudicedue to lack of use and obsolescence, a coke residue requirement, and reaffirmed with minor editorial corrections in 2001.40

AMERICAN WOOD-PRESERVERS’ ASSOCIATION STANDARD(This Standard is promulgated according to a consensus procedure and is under the jurisdiction of AWPA Subcommittee P-3)P3-01STANDARD FOR CREOSOTE-PETROLEUM SOLUTIONNote: AWPA Standard P3-01 consists of one page.1. Creosote-Petroleum Solution (CPS) shall consist solely ofspecified proportions of Creosote conforming to AWPAStandard P1/P13 and of Petroleum Oil conforming to AWPAStandard P4.1.1. No Creosote-Petroleum Solution shall contain lessthan 50 percent by volume of such Creosote, nor more than 50percent by volume of such Petroleum Oil.2. The test to establish conformance with the foregoingrequirements shall be made in accordance with AmericanWood-Preservers’ Association Standard A22.4, Due to the limited accuracy of this test, the purchaser maywish to obtain the materials separately and have them blendedunder his supervision.Standard P3 was reaffirmed in 2000 and in 2001 with a change in format.41

AMERICAN WOOD-PRESERVERS’ ASSOCIATIONSTANDARD(This Standard is promulgated according to a consensus procedure and is under the jurisdiction of AWPA Subcommittee P-3)P4-03STANDARD FOR PETROLEUM OIL FOR BLENDING WITH CREOSOTE1. Petroleum oil for blending with creosote (Standard P1/P13) shall conform to the following requirements:Not Less Than1.1 Specific Gravity1,2at 15.5°C/15.5°C (60°F/60°F) (not 0.96greater than 15.9° A.P.I.) ASTM Standard D 287Not More Than1.2 Water & Sediment, % by volume ASTM Standard D 96 1.01.3 Flash Point3 . Flash point as determined by the Pensky- 79°CMartens closed tester. ASTM Standard D 931.4 Viscosity4 . The viscosity shall be expressed as Kinematic 4.2 10.2vs. cST at 99°C (210°F) by ASTM Standard D 4451To convert the specific gravity of Group 0 petroleum oils at 15.5°C/15.5°C (60°F/60°F) to specific gravity at 38°C/15.5°Csubtract 0.0140. Group 0 oils have a specific gravity not less than 0.9665 at 15.5°C/15.5°C (60°F/60°F). The conversion forspecific gravity of Group 1 oil is made by subtracting 0.0162 and Group 1 oil has a specific gravity not less than 0.8504and not over 0.9664 at 15.5°C/15.5°C (60°F/60°F)2Petroleum oil with a lower specific gravity may be used provided experience or testing shows that it may be blended increosote without the formation of excessive sludge.3In the interest of plant and worker safety, petroleum oil shall have a minimum flash point of 79°C (174°F) by TCC (D 56).4Petroleum oils with a higher viscosity may be used provided the penetration requirements are met. The purchaser mayspecify the viscosity best suited to his/her requirements, allowing the supplier a tolerance of plus or minus 10% of thevalue specified (Equivalent vs. SUS at 99°C (210°F) shall be 40 min. to 60 max. by ASTM D 88).5Each of the foregoing determinations shall be made in accordance with the ASTM method currently in effect. TheASTM Standards referred to herein may be obtained from the American Society for Testing and Materials, 100 BarrHarbor Drive, West Conshohocken, PA 19428 (www.astm.org).42

U1-05 — Use Category System: User Specification for Treated Wood © 2005COMMODITY SPECIFICATION CCROSSTIES AND SWITCHTIES(This Commodity Specification is promulgated pursuant to a consensus procedureand is under the jurisdiction of AWPA Subcommittee T-3)1. INTRODUCTION: Commodity Specification Ccovers preservative pressure treatment ofcrossties and switchties. It includes generalrequirements, minimum preservative penetrationand retention requirements for its Use Category,special requirements and special information .1.1 The preservative retentions and penetrationsassigned to the Use Category in CommoditySpecification C are minimum retentions andpenetration depths for the commodity,preservative and species treated. They havebeen found to be satisfactory for their UseCategory.1.2 The requirements for preservativepenetration and retention assigned to any UseCategory for any combinations of preservativesor species are equally important for any productto be acceptable under this Standard, all thelisted requirements including preservativepenetration and retention must be met.2. GENERAL REQUIREMENTS: CommoditySpecification C is to be used in conjunction withAWPA Standard T1, Use Category System:Processing and Treatment Standard.2.1 Refer to Section 4 of the Use CategoryStandard for preservatives listed in thisCommodity Specification.2.2 Marking. Ties shall be branded withidentifying information, year of production, andany additional information which may bespecified by the purchaser. The brands shall besufficiently deep so that all characters are plainlylegible after treatment. This brand is to establishidentification, traceability and ownership of theproducts.2.3 Product Quality. Crossties and switchtiesshall conform to the physical requirements of thespecifications under which they have beenpurchased. Material shall be processed in such amanner as to prevent damage and degrade.2.4 Cleanliness. Crossties and switchties shall besupplied reasonably free of exudate and surfacedeposits.2.5 Conditioning. Crossties and switchties shallbe suitably seasoned or conditioned prior totreatment.2.6 Machining. Crossties and switchties shouldbe manufactured in their final form prior totreatment to eliminate any necessity forsubsequent cutting or boring of the treatedwood.2.7 Incising. Incising is required for Cypress,Coastal Douglas-fir, Western Hemlock, WesternLarch, Intermountain Douglas-fir, Jack Pine,Lodgepole Pine and Red Pine. Incising isoptional for Oak and Hickory, Mixed Hardwoods,Southern Pine and Ponderosa Pine.2.8 Sampling and Testing. A borer core shall betaken from 20 ties well distributed throughoutthe charge. If 80% of the cores meet thepenetration requirement shown in theCommodity Specification C penetration table forthe species treated, the charge shall be accepted.Except for Oak, if the average penetration of the20, 75 mm (3.0-in.) borings meet the penetrationrequirement, the charge shall be accepted.Specific instructions or the calculation ofpercentage of rings penetrated in Oak are givenin Standard M2, Paragraph5.3.2.Retention in ties shall be determined by gauge.Users requiring retention results by assayshould refer to Commodity Specification A.43

U1-05 — Use Category System: User Specification for Treated Wood © 20053.0 PRESERVATIVE RETENTION SPECIFICATIONS (Crossties and Switchties) – UC4A, UC4B, UC4CRetentions in English (pcf) unitsRetentions in English (pcf) unitsUse Category SystemRetention Specification by Gauge (pcf).(UC4A, UC4B and UC4C) Creosote Pentachlorophenol Cu NaphthenateSpecies CR CR-S, CR-PS PCP-A, PCP-C CuNOak and Hickory 7.0 or Refusal 7.0 or Refusal 0.35 or Refusal 0.055 or RefusalMixed Hardwoods 7.0 7.0 0.35 0.06Southern and Ponderosa Pine 8.0 8.0 0.4 0.06Coastal Douglas-fir, WesternHemlock, Western Larch8.0 or Refusal 8.0 0.4 0.06Intermountain Douglas-fir Refusal Refusal Refusal ---Jack, Red & Lodgepole Pine 6.0 7.0 --- ---Retentions in metric (kg/m3) unitsUse Category System (UC4A,Retention Specification by Gauge (kg/m3).UC4B and UC4C) Creosote Pentachlorophenol Cu NaphthenateSpecies CR CR-S, CR-PS PCP-A, PCP-C CuOak and Hickory 112 or Refusal 112 or Refusal 5.6 or Refusal 0.88 or RefusalMixed Hardwoods 112 112 5.6 0.96Southern and Ponderosa Pine 128 128 6.4 0.96Coastal Douglas-fir, WesternHemlock, Western Larch128 or Refusal 128 6.4 0.96Intermountain Douglas-fir Refusal Refusal Refusal ---Jack, Red & Lodgepole Pine 96 (6.0) 112 --- ---44

T1-05 — Use Category System: Processing and Treatment Standard © 20058.3.1 Seasoning. Where circumstances or climaticconditions permit, ties may be air seasoned. Airseasoning procedures are given in AWPA StandardM1. The maximum moisture content shall not bemore than:Oven DrySeasoning moistureSpecies (Months) Content (%)Locust, Oak, Black Walnut 9-14 50Douglas-fir, Western Larch 5-10 20Gum-Black, Tupelo, Sweet 4-7 40Southern Pine 3-6 30Hickory, all other hardwoods 4-10 40The moisture content of air-seasoned ties are tobe obtained from 50 mm (2 in.) borings taken midwaybetween the ends midway across the edge-face, andhalfway up the stack. Kiln-drying is permitted insuch a manner that causes no serious damage.Boulton drying is permitted for all species. Wherepermitted, steam conditioning temperature shall notexceed 115 O C (240 O F). Total duration shall not exceed17 hours for Southern and Ponderosa Pine and 3hours for Red Pine, Jack Pine, and Lodgepole Pine.Steam conditioning is not permitted for other species.8.3.2 Pressure Limitations. Minimum pressure is850 kPa (125 psig) for the refusal treatments.Maximum pressures shall not exceed:1750 kPa (250 psig) for Oak, Hickory, and mixedhardwoods1400 kPa (200 psig) for Southern Pine, PonderosaPine 1200 kPa (175 psig) for jack, red and Lodgepole8.3 CROSSTIES AND SWITCHTIES(AWPA Subcommittee T-3))pine. 1050 kPa (150 psig) for Coastal Douglas-fir,Intermountain Douglas-fir, Western hemlock,Western Larch8.3.3 Minimum Preservative Concentrations Theminimum preservative concentration forpentachlorophenol for refusal treatment shall be 5%wt/wt. The minimum preservative concentration forcopper naphthenate for refusal treatment shall be0.8% wt/wt copper as metal.8.3.4 Expansion Baths. Expansion baths for recoveryof preservative and retarding bleeding are permittedon all tie species as long as temperatures do notexceed those listed in Section 8.3.18.3.5 Retention Testing. The net retention in anycharge shall not be less than 90 percent of theretention specified, but the retention of 5consecutive charges shall be at least 100 percent.When a contract comprises less than 5 charges, thenet retention in any charge shall not be less than 95percent of that specified. The retention ofpreservative solution retained shall be calculatedafter correcting the volume of preservative to 40 O C(100 O F) for creosote using factors in AWPA StandardF1 and to 16 O C (60 O F) for pentachlorophenol usingfactors in AWPA Standard F2.8.3.6 Penetration Requirements. A borer core shallbe taken from the center of 20 ties in each charge. If80 percent of the borings meet the penetrationrequirements, the charge shall be accepted. For Oak,if the average penetration of twenty 75mm (3 in)borings meets the penetration requirements, thecharge shall be accepted.8.3.6 Minimum Preservative Penetration Requirements For Crossties And SwitchtiesFootnotes: Penetration Tables(a) Wherever depth “or” percent of sapwood penetration is specified, it shall be interpreted to mean whichever is less.(b) Wherever depth “and” percent of sapwood penetration is specified, it shall be interpreted to mean whichever is greater.(c) For Red Oak, the penetration must average a minimum of 65% on 20 - 75 mm (3.0 in.) cores.45

LITERATURE REFERENCESAmerican Wood-Preservers’ Association (AWPA). 2005.THE BOOK STANDARDS. The American Wood-Preservers’ Association,Selma, AL.American Railway Engineer Maintance-Of-Way Association (AREMA).2003. TIES AND WOOD PRESERVATION, Chapter 30. Landover, MD.Hoadley, R. Bruce. 1990. IDENTIFYING WOOD.The Taunton Press, Newtown, CN.Hoadley, R. Bruce. 1980. UNDERSTANDING WOOD.The Taunton Press, Newtown, CN.Hunt, G. M. and G. A. Garratt. 1938. WOOD PRESERVATION.McGraw-Hill Company, New York, NY.Nicholas, D. D., Editor. 1973. WOOD DETERIORATION AND ITSPREVENTION BY PRESERVATIVE TREATMENTS, Volumes I & II.Syracuse University Press, Syracuse, NY.The Railway Tie Association (RTA). 2003. SPECIFICATIONS FORTIMBER CROSSTIES & SWITCH TIES. Published by The Railway Tie Association,Fayetteville, GAUSDA Agriculture Handbook No. 40. 1952. PRESERVATIVETREATMENT OF WOOD BY PRESSURE METHODS. Superintendentof Documents, Washington, DC.USDA Agriculture Handbook No. 72. 1974. WOOD HANDBOOK:WOOD AS AN ENGINEERING MATERIAL. Superintendent ofDocuments, Washington, DC.Webster, P. D. 1992. THE WOOD CROSSTIE ..... A THREE QUARTERSOF A CENTURY HISTORY. Published by The Railway Tie Association,Gulf Shores, AL.Youngquist, W. G. and H. O. Fleischer. 1977. WOOD IN AMERICANLIFE - 1776 - 2076. Forest Products Research Society, Madison, WI.46

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CONDITIONING & TREATMENTOF WOOD CROSSTIESWood is a cellulose material which canbe adversely affected by decay fungi,insects, and marine borers. For all nondurablewood species and the sapwood ofall woods, the use of chemical preservativesmust be applied to protect wood fromattack from these organisms.The degree of protection given to thewood depends upon the type of preservativeused and proper penetration andretention of the preservative. In addition,there is a difference in the treatabilityof the various wood species. Alsothere is a difference in the treatability ofthe sapwood and the heartwood portionof the various wood species.With respect to wood crossties, theAmerican Wood Preservers’ Association(AWPA) Commidity Standard UC4 forcrossties and switch ties, gives the generalrequire-ments for preservative treatment bypressure processes. In addition, theStandard describes processing, conditioning,treatment, results of treatment(quality control), and storage of treatedcrosstie materials.It is the intention of this booklet toprovide a general overview of the conditioningand treatment of wood crossties.It is recognized that there are other treatedwood materials which are used by therailroad transportation industry. Thesewould include poles, piling, and otherlumber products. In generic terminologywhen there is a discussion concerningwood crossties, there will be someoverlap with switch tie and timberproduct materials.48

PREPARATION OF CROSSTIES ANDTIMBERS FOR TREATMENTIf there is one process in the treatmentof wood products that is more importantthan any other, it is the preparation andconditioning of wood prior to treatment. Itis necessary to remove most of the freewaterfrom within the wood cells. Thismust be accomplished in order to put thewood preservative within those cells.When all the free-water has been removedfrom within the wood cells then it is saidthat the fiber saturation point has beenreached. With most wood species it isthirty (30) percent moisture based on theoven-dry weight of the wood. It isbelow the fiber saturation point thatwood begins to shrink and developschecks and splits. This occurs mostnotably in large timbers such ascrossties.The removal of water can beaccomplished in four ways:• Kiln Drying• Air Seasoning• Boulton Drying• Steam Conditioningeconomical to process materials such ascrossties and other large timbers in thismanner.Air SeasoningThis drying process is the preferredmethod for conditioning wood crosstiesprior to treatment. It is the generalpractice to segregate the wood accordingto species and the size of the timber. Forpractical purposes, the species separationis into two groups - the oaks andmixed hardwoods (refer to the first sectionof this book for a more thoroughdiscussion). In addition, some railroads foruse purposes ask that treating companiessegregate the red and white oaks, andpossibly other species.Climatic conditions significantlyinfluences air seasoning. In some partsof the Southeast where the temperatureand humidity are relatively high during alarge part of the year, it can be difficultto air season crossties and timbers. It isKiln DryingWith respect topractical applicationswithin the crosstieindustry, the process ofkiln drying is not used toremove water from largetimbers (six to eight inchcross-section). To date, ithas not been found to be49

PREPARATION OF CROSSTIES ANDTIMBERS FOR TREATMENTimperative in these locations that air seasoningbe carefully monitored under theseconditions to avoid premature or incipientdecay. Within the treating industry this isoften termed “stack-burn”. There arecertain wood species such as hackberry,because of its high sugar content, thatshould be pretreated with a preservativechemical to prevent this surface decay/stack-burn potential.As with any of the conditioning/seasoningprocesses for removal of moisturefrom wood, there are both advantagesand disadvantages. The airseasoningprocess is the preferredmethod because it is the most economical.The extra time in the treating cylinder foreither the Boultonizing or steamconditioningis considered expensive incontrast. On the other hand, a majorshortcoming of the air-seasoning processis the inventory cost of the accumulated,untreated crossties and timbers. Dependingon the climate, regional locationand the wood species, the required airseasoningtime can range from four totwelve months and in some instances,even longer than twelve months (seeRTA Research Compendium, Volume I,Tab 21).50

PREPARATION OF CROSSTIES ANDTIMBERS FOR TREATMENTBoulton Conditioning MethodIn dry or more arid regions of thecountry, rapid drying of the timber cancause severe checking and splitting. Theconditioning procedure best suited forwater removal in these regions is theBoulton process. In addition, a significantadvantage for the Boulton dryingprocedure is that material can be processedrapidly from the “green” condition.It speeds up the drying process. Ascurrently used in the industry, theBoulton process can be described asfollows:The green/wet wood materialsare placed in the treating cylinderwhich is then filled withhot creosote. It is important tocompletely cover the timberswith the creosote and that theequipment have sufficient voidspace for the collection of moisturevapor. The creosote is heatedunder vacuum to draw themoisture vapor out of the woodcells. It is important 1) to knowthe moisture content of the woodprior to treatment and 2) that allwood within the treating cylinderbe uniform in moisture content.The treating operatormust be able to measure theamount of water that has beenremoved from the charge of woodmaterial. In addition there willbe a volatile portion of the51

PREPARATION OF CROSSTIES ANDTIMBERS FOR TREATMENT52creosote whichwill condensealong with thewater.These shouldbe separated fromthe water with thevolatile materialsreturned to thecreosote worktank.Once the Boultonconditioning processhas been completed,the pressure treatmentof the wood with creosote can thenproceed. This process will be describedin a later section of the paper. It is generallyconsidered that the total Boultonprocessing time will be between six andten hours. The variability in the time forconditioning will be wood species andtemperature dependent. For example,there can be a variation between the timerequired for Douglas fir and the oaks.Also, a charge of crossties to be Boultonizedin January in Ontario, Canadawill necessarily be longer as comparedto a charge of material to be Boultonizedin July in a location such as centralTexas.There are advantages and disadvantagesin using the Boulton process inconditioning wood. Major advantagesare listed as follows:• Crossties and timbers can effectivelybe conditioned/seasoned in amuch shorter time as compared toair seasoning. This results in asignificantly reduced total timeto process and creosote treat thewood products.• As compared to the steam conditioningmethod, the Boulton processuses a significantly mildertemperature with a minimumeffect on wood strength properties.• Again when compared to thesteaming process, a lower moisturecontent level within thewood can be achievedThe chief disadvantages of the Boultonprocess are that it is only suitable forcreosote and other oil preservatives; itoften costs more than air seasoning; andit heats the wood more slowly than the

PREPARATION OF CROSSTIES ANDTIMBERS FOR TREATMENTsteaming process.The Steam Conditioning MethodThe final conditioning process forremoving water from wood prior totreatment is known as the steam conditioningprocess. In applying the steamconditioning process, as currently usedin the industry, it can be described asfollows:A charge of green pinematerial is placed in the cylinderand steamed for several hours.The total time for steaming isdependent on the size of the timbers.At the conclusion of thesteaming period, a vacuum isapplied to remove the moisturevapor from the wood. It isimportant to note that thesteaming time is dependent upon1) temperature of the wood 2)cross-sectional dimensions ofthe wood and 3) wood density.It is important for the vacuumto be applied as soon as possibleafter the steaming cycle has beencompleted. When the temperatureof the wood surface is loweredsignificantly, the averageamount of water removed duringthe vacuum will be lower than ifthe vacuum had been appliedimmediately after the steamingcycle.53

PREPARATION OF CROSSTIES ANDTIMBERS FOR TREATMENTOften a common practicewithin the treating industry is toapply the steam in one cylinderand remove the charge from thecylinder; and then continue withthe vacuum and creosote pressuretreating process in a secondcylinder. This practice is not themost efficient because the maximumamount of water vapor cannotbe removed.The common practice of steamingsouthern pine timbers (assuming twentypounds gauge pressure) will effectivelycondition a charge of material in a timeperiod of ten to fourteen hours. Thisincludes both the steaming and vacuumperiods of the conditioning cycle. Aswith the Boulton cycle, these times willvary 1) with the temperature of the woodand 2) pine species and its density.Currently within the industry thisprocess is generally used only withsouthern pine timbers and to a lesser extentfor other pines. The primary reasonfor using steam conditioning is that theair-seasoning process of this wood cannotbe effectively performed withoutsome decay occurring in the southernclimate areas. There are advantages anddisadvantages to the steaming process.The principal advantages of the steamingprocess are:• Steam heats faster than any otherheating mediums• Easily applied and usually does notrequire any special equipment in thetreating cylinder• The temperature can be easily controlledThe disadvantages are as follows:• Only a limited amount of moisture54

PREPARATION OF CROSSTIES ANDTIMBERS FOR TREATMENTcan be removed in the steaming/vacuumcycle• It is often necessary to use highertemperatures than are used, forexample, inthe Boultonprocess (notethat the AWPAStandardshave maximumtimesand temperaturesthat canbe used in thesteamingprocess).MechanicalPreparationThe first partof this paper hasfocused on themethods for removalof moisturefrom wood crosstiesand timbers inorder to conditionthem prior to creosotetreatment.However, it isnecessary to takea “step-back” andnote several mechanical procedures thatneed to be implemented before thecondition-ing processes are initiated.It is assumed that the crossties andtimbers that will be conditioned andsubsequently treated have been inspec-ted for or by the customer, who has purchasedthe material. An inspection “inthe-white”is important to eliminatedthose pieces which have defects. Thereare a number ofdefects that willcause a cross-tie,for example, to beculled. Theseinclude ring-shake,wane, large knots,incipient decayand excessivesplits and checks.There are threemechanicalprocedures usuallyperformed oncrossties andtimbers; they arelisted as follows:• anticheckingdevices• framing, adzingand boring• incisingHistorically,antichecking ironscommonly knownas S-iron and C-iron were used toreduce severe end-splitting in crosstiesand switch ties. Today a product knownas an end-plate is also in widespreaduse. It is generally believed that endplates are effective in reducing theamount of end-splits. End-plates are55

PREPARATION OF CROSSTIES ANDTIMBERS FOR TREATMENTgenerally inserted on those crossties that arejudged by an inspector to have the potentialto split at the end.Whenever practical, all framing,adzing and boring of crossties and timbersshould be done before the pressuretreating process. Cutting into the timberafter treatment can expose untreatedwood. As a normal practice the standard7x9 inch crosstie will not be cut ordrilled; however, there can often be considerableframing, etc., that will be performedon bridge crossties and timbers.It is important to have all this work doneprior to treatment.The incising of crossties and timbershas been a common practice for thosewood species that are resistant to penetrationof liquid preservatives. In particular,the Rocky Mountain and westernspecies, such as Douglas fir, have beenpassed through a machine equipped with56cutting teeth projecting from the rollers.This is what is referred to as the incisingprocess.The primary benefit of incisingwoods that are difficult to treat is to cutthrough the fiber and expose end-grainto allow preservative penetration of thewood. There is an additional benefit.By incising crossties and large timbersin the original green state, it is possibleto achieve a more uniform drying/conditioningof the wood. The use of incisingminimizes severe checks and splits thatoften occur in large timbers. This is whymost ties today are incised whether ornot they are resistant to liquid preservativepenetration.

EFFECT OF WOOD STRUCTURE ONTREATMENTWood varies greatly in its structure.The hardwoods differ from the softwoodsand within these groups the individual speciesare different. It is not the intent of thispublication to provide a wood technologylesson, however it is of importance to notesome of the wood structural differences thateffect the treatability of various wood species.Listed as follows are some of the woodcharacteristics that could possibly influencepreservative treatment:• Within a specific wood species it isgenerally accepted that the sapwood ismore easily treated than the heartwood.The heartwood may contain gums,resins, extractive and pigment materials.Because of these materials, the heartwoodis a darker color.• Wood density does not significantlyinfluence the treatability of a wood species.There are too many other considerationssuch as open pores in red oak,tyloses found in whiteoak, the presence of resinin the heartwood of varioussoftwoods.• The longitudinal woodcells in softwoods(termed tracheids orfibers that have closedends) and hardwoodswhich have open cellsstacked end to end andknown as vessels. Onecould think of the longitudinalwood cells asbeing a “bundle of straws”. Thesoftwood fibers have bordered pits inthe cell walls and these allow liquids topass readily between the cells. Hardwoodsdo not have this type of cellstructure. The penetrability of the liquidpreservative depends to a greatextent on the open or closed conditionof the longitudinal cells.• The directional structure differenceswithin a cross-section of wood influencethe penetration of liquids. Alongwith the previously mentioned longitudinalfiber direction of wood cells,would be the tangential direction flowingaround with the wood growth ringsand third the radial direction across thegrowth rings and parallel to the woodrays. The most easily penetrated fibersare those in the longitudinal direction.57

MOISTURE CONTENT AND ITSEFFECT ON TREATMENTAt the beginning of the paper, a definitionfor the fiber saturation point wasgiven as approximately thirty (30)%moisture content. This is an importantdefinition to keep in mind. For example,when trees are freshly cut, the greenmoisture content for Douglas firsapwood is 115%; the heartwood is37%. The sapwood of white oak has amoisture content of 78% and the heartwoodis 64%.The water within the cells of thewood completely fills the void space inthe cell. This is known as free water.The cell walls remain saturated withwater; thus, the term fiber saturation.As this moisture is removed from thewood fibers, shrinkage of the wood willoccur. It is important to control thismoisture loss in order to minimize thechecking and splitting of wood. Thisfact was illustrated in the previous sec-tionsin the discussion of Conditioning Processesand the use of incising in the mechanicalpreparation of crossties and timbers.The presence of moisture in wood canbe a determining factor for treatability. Ifthe wood has not been conditioned and thecells are full of water there is no place forthe preservative to enter the wood. Largetimbers, such as crossties and switch ties,do not have to have their moisture contentreduced to fiber saturation point when thetreatment will be creosote or an oilbornepreservative. Satisfactory penetration andretention of preservative can be achievedwith a moisture content in the range of 40 to45%.Consideration needs to be given to thefact that when treating with creosote thewood can be too dry. With the emphasistoday on clean and dry treated products,58

MOISTURE CONTENT AND ITSEFFECT ON TREATMENTlaminated bridge timbers that have amoisture content of 15% can be significantlyover treated. There are procedures thatcan be used to minimize this over treatment.These will be discussed in the sectiondealing with treatment processes.The moisture content of the woodproduct is an important piece of informationthat needs to be known by thetreating operator before the charge ofmaterial is to be treated. The followingis just a couple of examples:• For green crossties that are to beBoultonized, how much water needs tobe removed?• For air-dried timbers that are to betreated with creosote, has sufficientmoisture been removed to allow forproper penetration of the preservative?• What is the moisture content of pinetimbers? Do they need to be steam conditioned?It is important to rememberthat the process known as treatment torefusal can only be used with refractorywood species such as Douglas fir andwhite oak.59

WOOD PRESERVATIVE AND THEPRESSURE PROCESSESThe processingandtreatment ofwood crossties,switch ties andtimbers aresomewhatunique. Thisproduct as usedby the NorthAmerican railroadindustryhas historicallybeen treated with a creosote solutionmeeting the requirements of AWPAStandard P2. There are also occasionswhen ties and other timber products suchas bridge materials will be treated usingthe AWPA Standard P1/P13 .In addition, another creosote preservativeblend material has been used bythe industry to treat crossties and timbers.In those regions of North Americathat have an arid climate or in northernzones where the potential decay andinsect attack are less, a heavy petroleumoil that meets AWPA P4 Standard hasbeen used with creosote. This creosote/petroleum solution has been usedextensively for many years to reduce thecost of the preservation solution. Its usehas been primarily in the western UnitedStates and Canada in which conditionsof use are less conducive to wooddeterioration.Creosote and its solutions are thepreservatives most widely used. Thecrossties arepressuretreated usingthe empty cellmethod(Lowry orRuepingProcess). Thespecified creosotenet retentionisusually betweensix andten pounds per cubic foot (pcf).As previously discussed prior totreatment the wood crossties and timbersmust be properly conditioned in order toachieve the desired preservative penetrationand retention. As reference, itshould be noted that the various conditioningmethods and processing proceduresare described in the AWPA Book ofStandards. A recent copy of the AWPAStandards should be readily available toanyone who is involved in the treatmentand use of wood crossties.Before initiating a discussion on thepressure treatment process it should benoted that many of the railroad customersspecify and many of the treatingplants that produce crossties use a sterilizationcycle just prior to pressure treatment.To achieve sterilization laboratorystudies have shown that the heating conditionsrequired to kill wood-destroyingfungi require both a specific temperatureand duration of time. The results also60

WOOD PRESERVATIVE AND THEPRESSURE PROCESSESindicate that it is not practical to sterilizewood at temperatures below 150 degreesF. The following table shows the temperature/timesto attain sterilization in wood:Temperature (F)Time (minutes)150 ................................... 75170 ................................... 30180 ................................... 20200 ................................... 10212 .................................... 5However, it must be taken into considerationthat the temperature required isan internal one not an external temperature.Thus the center of a 7 x 9 crosstie,or any other large sawn timber, must reachthat desired temperature. Given as followsare a few examples:Time (hours) to ReachSize of Timber (inches) Temperature of 150º F *4 x 4 ....................................... 1 ¼6 x 6 ......................................... 36 x 8 ......................................... 47 x 9 ......................................... 58 x 10 ...................................... 6 ½10 x 10 ..................................... 8 ½• At conclusion of the pressureprocess, initiate post conditioningprocedures; i.e., final vacuumand possibly steaming,• Make the determination if thewood has been properly treatedusing inspection procedures forpenetration and retention of thepreservative.A more detailed description of thepressure treating process will now begiven.* Note that inital wood temperature was 60degrees F. with the external heat source being 200degrees F.The pressure treatment process isbriefly outlined as follows:• Properly condition the wood to betreated (procedures describedpreviously),• Determine the pressure process tobe used either Full or Empty Cell,61

THE TREATMENT PROCESSESBecause the vast majority of railroadcrossties, switch ties and timbers aretreated only with creosote and its solutions,the procedures used for pressuretreating with this preservative will be theonly one discussed. As previously indicated,there are two pressure processesthat can be used in the treatment ofcrossties and timbers with creosote.These two principal types are the full cell(Bethell) and the empty cell (Lowry andRueping). The most commonly used is theempty cell process. For the purposes ofthis booklet, a somewhat limited practicalapplication for these two pressure treatingprocesses will be described. Additionalinformation can be obtained by the readeron this subject from reference books.The major difference between the fullcelland the empty cell processes is that apreliminary vacuum is applied to the treatingcylinder during the initial phase of the fullcell process while with the empty cellprocess, air pressure is applied instead of avacuum. That initial air pressure can beatmospheric pressure as defined by theLowry process. The Rueping process isthe most commonly used. Air pressure isforced into the treating cylinder before thepreservative is admitted. The air pressure isthen maintained while the cylinder is filledwith preservative. Thus the wood cells willcontain air under pressure and preservativeunder pressure as well.Depending upon the desired preservativeretention level and the wood species,the initial air pressure may varybetween 20 and 60 psi. The ultimateobjective is to vary the retention levelbased on the amount of the preservative“kick-back” from the wood cells during thefinal post-conditioning vacuum cycle. Uponrelease of the pressure, the preservative isbeing forced out of the wood by the62

THE TREATMENT PROCESSESexpanding air. The amount of recoveredpreservative will be greater when the initialair pressure is higher.A good example would be the treatmentof southern pine.• With the full-cell process and theapplication of a vacuum, 25 pcfcreosote will be retained.• With the Lowry process and atmosphericinitial pressure, theretention level could be 20 pcf.• With the Rueping process and aninitial air pressure of 10 psi, thecreosote retention could be 16 pcf.• With an initial air pressure of 30 psi,the creosote retention level couldbe 12 pcf.• With the initial air pressure being60 psi, the creosote retentionlevel could be 8 pcf.The above is strictly a theoreticalexample to show the effect the vacuumand initial air pressure can have on thepreservative retention level. It is importantfor any treating plant operator to beaware of these differences and effects ofvacuum and the amounts of air pressure.The Pressure PeriodOnce the creosote preservative hasbeen admitted into the cylinder and theinitial air pressure or vacuum has beenmaintained during the creosote fillingprocess, the charge of material is thenput under pressure. The pressure periodmay vary depending upon the wood productthat is being treated. AWPA UC4gives recommended maximum and minimumlevels of pressure depending upon thewood species. There is a similarrecommendation for the maximum andminimum temperature level for the creosoteduring the pressure period.The pressure period can also varydepending upon the conditioning cyclewhich was used to make the wood readyfor treatment. In addition to the woodspecies, the size of timber can effect thelength of the pressure period. For example,kiln dried southern pine 6x6 inchtimbers will have a shorter pressure periodas compared to Boultonized oakswitch ties. This assumes that both productshave approximately the same creosoteretention level. Once again, it isimportant that the treating operator haveknowledge of the products that are beingtreated and the operation of his ownplant facility.Post Conditioning ProcessesOnce the pressure period is completed,the final post conditioning process isone that focuses in several areas to (1)recovery of preservative and (2) environmentalconsiderations have become importantissues and it is imperative surface63

THE TREATMENT PROCESSESdeposits and bleeding creosote woodproducts be minimized. The postconditioning processes are as follows:• Temperature considerations of thepreservative as the pressure periods iscompleted,• Expansion bath to assist in the recoveryof the creosote preservative,• Vacuum cycles to recover preservative,• Possible use of steaming improvessurface appearance of the treated woodmaterial.There are four post conditioning procedureslisted above. The first and thethird processes are the most importantand must be used in every treating cycle.A brief description of each of the aboveprocesses follows:Temperature considerations —within two hours of completion ofthe pressure period, the temperatureof the creosote treating solutionshould reach its peak. That temperaturenormally should be between 190and 200 degrees Fahrenheit.Expansion bath — this is a procedurethat is often used with Douglasfir timbers. As the pressure withinthe cylinder is released and the creosoteremains in the cylinder with thecharge of timber still submerged, thetemperature of the preservative israised approximately 10 degreesFahrenheit. A vacuum is appliedduring this period which assists inremoving the air and some creosotefrom the wood.Vacuum cycles — once the creosote64has been drained from the cylinder, itis imperative that at least one vacuumcycle (minimum 22 inches Hg)be applied to the charge of material.The duration of this vacuum cyclewill be dependent upon the material(species and size) that has beentreated. For optimum surface cleanliness,it is recommended that followingthe first vacuum cycle and“breaking” back to atmosphericpressure, that a second vacuum cyclebe applied. The duration of thissecond cycle will be based upon thetreating operator’s experience.Steaming cycle — the use of steamin the post conditioning part of thetreating cycle is definitely optional.Treating plants do not favor the useof steam because it accumulateswaste water that needs to be processed.However, steaming betweenthe two vacuum cycles is an extremelyeffective way of expandingthe air which remains in the treatedtimber which is ultimately removedwith the second vacuum cycle. Thesteam that is applied should not be“live” steam. The steam shouldoriginate from water that has beenput into the cylinder to cover thecoils and thus, generates steam fromthe boiling of the water (closedsteaming operation).

STANDARDS AND SPECIFICATIONSFOR TREATMENTStandards and specifications are an extremelyimportant segment of any industry.They are the guide by which products areproduced. They allow the consumer, whopurchases and uses the product, to haveconfidence that what has been purchasedwill perform to expectations that the producerhas advertised to the purchaser.The wood treating and railroad transportationindustries are no different. There areessentially three (3) sets of specifications andstandards that govern the industry:• The AREMA specifications for timber crossties,switch ties and industrial grade crosstieswere jointly developed by the Railway TieAssociation (RTA) and the American RailwayEngineering and Maintenanceof-WayAssociation (AREMA).These set of specifications pertain tothe untreated (white material) priorto its treatment with preservative.Within these specifications are giventhe physical requirements, inspectioncriteria and the definition of defects.• The second set of standards which isimportant to the wood treatingindustry pertains to the type ofcreosote that is used in treatment ofcrossties and timbers. These AmericanWood-Preservers’ Standards(AWPA) are listed as follows:- P1/P13, Standard for CreosotePreservative- P2, Standard for Creosote Solution- P3, Standard for Creosote -Petroleum Solution- P4, Standard for Petroleum Oil forBlending with Creosote• The final Standard that is importantto the wood treating and railwaytransportation industries is thatwhich brings together the treatmentof “white stock material” and the creosotepreservative used in the pressure process forthe treatment of crossties and timbers. Thisis the AWPA UC4, the Standard for Treatmentof Crossties and Switch ties - PreservativeTreatment by Pressure Processes.The above stated Standards and Specificationscan all be found in the Appendixsection of this Tie Guide, published in 2005by the Railway Tie Association (RTA).65

QUESTIONS AND ANSWERSNOTE: These questions apply to both sections of the Tie Guide. A review of eachsection is necessary to answer all questions.(circle the one correct answer)• Which American Wood -Preservers’ Association (AWPA) Standard pertains tothe treatment of crossties and switch ties?Standard UC2 UC3 UC4 UC5• What is the fiber saturation point of wood?Moisture Content of 20% 25% 30% 34%• When treating a Boulton charge of hardwood crossties, what would be anacceptable moisture content at which the ties could be treated?Moisture Content of 25% 32% 35% 42%• Which of the four conditioning processes is the least used by the treating industryfor removing moisture from crossties and timbers?Kiln DryingBoulton DryingAir SeasoningSteam Conditioning• Below what moisture content does wood start to shrink?Moisture Content of 20% 30% 35% 38%66

QUESTIONS AND ANSWERS• Wood being a cellulosic material, what primary mechanism causes the deteriorationof the wood crosstie?Termites Carpenter ants Fungi Mechanical Damage• What is the primary creosote treating solution used to impregnate woodcrossties?P1/P13 P2 P3 P4• Which set of Standards are the ones used primarily by the wood treating industry?American Wood-Preservers’ Association (AWPA)Railway Tie Association (RTA)American Standard for Testing Materials (ASTM)American Railway Engineering and Maintenance-of-Way Association (AREMA)• The first commercial wood treating plant was built in which location?West Pascagoula, MississippiLowell, MassachusettsSomerset, MassachusettsLouisville, Kentucky• The full cell pressure treating process is often referred to as ...Boulton Process Rueping Process Lowry Process Bethell Process67

QUESTIONS AND ANSWERS• In the early 1900’s, J. B. Card added which material to creosote for the treatmentof crossties?sodium chloride pentachlorophenol zinc chloride copper sulfate• Which of these hardwood species is one that is not often used as crosstie material?red oak red maple hickory basswood• Which of these softwood species is one that is not often used as crosstie material?southern yellow pine Douglas fir Western hemlock Eastern white pine• Which of these white oak species does not have tyloses?Oregon oak chestnut oak post oak swamp white oak• Which of these softwood species has been used predominately as timber bridgematerial?tamarack southern yellow pine eastern hemlock Ponderosa pine• Which of the western softwood species is considered a timber to be of significantused in the railway transportation industry?Western Hemlock Port Orford Cedar Redwood Douglas fir68

QUESTIONS AND ANSWERS• During the wood treating process which of the following mediums is the mostefficient?electric heat steam heat Boulton heat liquid heat transfer• End-plates are used for what primary reason?reduce abrasion on the end of crosstiehold large knots “in-place”reduce ring-shakereduce end-splitting• What is the primary reason that incising is beneficial when applied to a crosstiethat is green and in the “white”?more uniform dryingreduce moisture losehelp preservative penetrationprevent decay• Which of these wood characteristics influence treatment with liquid preservative;thus assist in the penetration of the preservative?wood densityheartwood cellstyloseslongitudinal wood cells69

QUESTIONS AND ANSWERS• In recent years there has evolved an emphasis on “clean and dry” treated woodproducts. Of the following techniques used in a treating cycle, which would havethe most effect on wood surface cleanliness?pressure cycle temperature steam vacuum• What information is probably the most important for a treating operator toknow about the charge of wood that is going to be treated?wood speciesmoisture contentdesired preservative retentiontype of treating cycle to be used• When adjusting the treating cycle in order to have an effect on raising or loweringthe preservative retention level, which of the following techniques will bemost influential?temperature initial air pressure vacuum steam pressure• At the conclusion of the pressure cycle when treating with creosote at whattemperature is it most desirable to have the charge of crossties?Degrees Fahrenheit — 150 175 195 225• The final vacuum cycle used to remove excess air and creosote from a charge ofcrosstie, it is imperative that what level of vacuum be achieved?Inches of Mercury (Hg) — 10 18 22 3070

QUESTIONS AND ANSWERSQUESTIONS EITHER ARE TRUE OR FALSE — circle the correct one• The most important Standards writing organization for the treating industry isthe American Standards for Testing Materials (ASTM)TrueFalse• The service life of wood products is significantly enhanced when pressure treatedwith a preservative solution.TrueFalse• In the Western and Rocky Mountain states and in Canada, it is possible to use aheavy petroleum oil that meets AWPA P4 Standard treat wood and achievesatisfactory service life for crosstie material.TrueFalse• Decay organisms that attack untreated wood - fungi and termites - are highlyactive at low humidity and low temperature.TrueFalse• The heartwood of a tree is generally more easily treated with preservative than isthe sapwood.TrueFalse71

QUESTIONS AND ANSWERS• Of the hardwood (oak) species, one of the most easily treated is red oak.TrueFalse• One of the most important factors in the treatment of wood is its moisture content.TrueFalse• Some of the “free-water” needs to be removed from within the wood cell in orderto treat wood.TrueFalse• Climate conditions in a specific region of North America can influence the airseasoningof crossties and switch ties.TrueFalse• When considering the conditioning processes, the most efficient means of heatinga charge of timber is by using Boulton Process.TrueFalse• The mechanical procedure known as incising performed on crossties is an excellentprocedure to encourage uniform air-drying of the wood material.TrueFalse72

QUESTIONS AND ANSWERS• The heartwood of most white oak species is difficult to treat because of thepresence of tyloses.TrueFalse• Creosote-petroleum solutions are often used to treat crossties in Western aridregions of the United StatesTrueFalse• Creosote attained its dominant use as preservative treatment for crossties andtimbers just following World War I and during the early 1920’s.TrueFalse• Creosote has been used for well over 100 years in the treatment of wood productsand it still remains the preferred preservative of choice for the treatment ofcrossties.TrueFalse• The mixed hardwoods are primarily made up of the following wood species:beech, cherry, black locust, sassafras and catalpa.TrueFalse73

QUESTIONS AND ANSWERS• One of the heaviest and most dense wood species used for crossties is beech.TrueFalse• Premature or incipient decay in crossties can be caused by the Boulton conditioningprocess.TrueFalse• When steam conditioning a charge of southern yellow pine timber, an acceptableand efficient practice is to apply the steam in one cylinder; remove the chargeand place in a second cylinder in order to complete the vacuum cycle and creosotepressure process.TrueFalse• The most common type of anti-checking device is known as the S-iron.TrueFalse• Wood density does not significantly influence the treatability of a wood species.TrueFalse• The liquid preservative moves through wood cells most easily across the growthrings of the wood.TrueFalse74

QUESTIONS AND ANSWERS• The term “treatment to refusal” should only be used when a refractory woodspecies such as Douglas fir or white oak are the charge of material that is to betreated.TrueFalse• The Hybrid Engineered Wood Crosstie is a highly refined structural materialthat does not need to be treated with preservative.TrueFalse• As second and third growth timber - typically smaller in diameter - that arecurrently being harvested reach the market, it is reasonable to expect the hybridengineered wood products will have a future in the transportation industry.TrueFalse75

AuthorAuthorConsultingEngineerEditor76ABOUT THE AUTHORSGeoff WebbGeoff Webb is graduate of the Pennsylvania State University with a BS in ForestProducts and has an MBAin Marketing and International business fromDuquesne University. His experiences include product development, technicalservice and sales in the adhesive, chemical and forest products industries. Atthe time of this publication, Geoff was a Product Specialist with Kop-Coat, Inc.,Pittsburgh, PA, servicing the stain prevention needs of lumber mills inthe northern Appalachian states.David A. WebbDave Webb has a BS degree from Baldwin-Wallace College and Master of Forestryfrom Duke University in Wood & Forest Products. He has over 35 years of experiencein the field of wood products and wood preservation. He has developed newproducts in the areas of wood adhesives, finishes and preservatives; authoredover 40 technical papers on various subjects concerning wood products; is theholder of four US patents; and has a consulting business in the area of woodproducts and preservatives. He was formerly President of the American WoodPreservers’ Association (AWPA) and acted as Chairman of RTA’s Research andDevelopment Committee. Mr. Webb received the Association’s Award of Merit in2001.Dave Webb can be reached at 724.898.9663 voice, or by E-mail: davidawebb@aol.comAllan M. Zarembski, P.h.D., P.E.Dr. Zarembski is the author of over 80 published papers on railroad trackanalysis and behavior, rail fatigue, and freight car analysis. He has heldpositions of director of research for Panarol, Inc. and Speno Rail Services, Inc.,as manager of the Association of American Railroads Track Research Division,and now is president of ZETA-TECH and Associates a consulting firmspecializing in analysis of railway systems and operations, failure behavior ofrailway components, applied economics and computer modeling and softwaredevelopment. Dr. Zarembski may be reached through his office at:609.779.7795 voice, or by E-mail: zarembski@zetatech.comJames C. GaunttExecutive Director of the Railway Tie Association -Jim Gauntt has spent all of his 26 year career in the wood preserving industry. Hiswork includes acting as the national director of codes and product acceptance forthe Osmose Wood Preserving Company of America, vice president of sales forRandall Brothers, Inc., a 120 year old major architectural millwork, building materialdistributor and pressure treating facility for wood products and as executive directorof the Railway Tie Association. Mr. Gauntt regularly provides editorials and articlesfor Crossties magazine, an RTA publication that reaches over 3,000 readers bimonthly.Mr. Gauntt can be reached through the Railway Tie Association offices at:115 Commerce Drive, Suite CFayetteville, Georgia 30214770.460.5553 voice 770.460.5573 faxE-mail: ties@rta.org • Website: www.rta.org