Fasteners - hdgasa

The use of hot dip galvanizing in general miningmake a very important contribution tothe profitability and safety of the miningoperation.Painted steelUnlike hot dip galvanized steel, paintedsteel, generally irrespective of the paintsystem used, does not tolerate damageand in corrosive mining conditions willbe highly susceptible to corrosion.Unlike other conditions where paintedsteel, or paint coatings in general, arebeneficially used, e.g. in buildings,residential homes or for roof cladding,in underground mining conditions andother mining conditions like oreprocessing plants, painted steel willrequire regular and frequentmaintenance to the coating in the formof either repair of the coating orreplacement of the coating. As statedpreviously, in these conditions,maintenance is often impractical, verycostly and, importantly, inefficient, asthe conditions are far removed fromthose optimally required for repainting.The conditions under whichmaintenance has to be performed arevery different from those under whichthe original coatings were applied. Inthe case of shaft steel, damage to thecoating can occur to erection orconstruction and accordingly corrosioncould be initiated before theinstallation has even beencommissioned. Even if a very optimisticview is taken, any calculation of lifecycle costs, which includes thepredicted future maintenance paintingroutines, if this is possible, will be highand very much higher than comparativelife cycle costs for hot dip galvanizedsteel.Local damage to protective paintcoatings will initiate localised corrosion,the final consequence of which iscorrosion pitting. Corrosion pitting,especially where relatively thin gaugesteel is used, is extremely concerning asit is difficult to monitor and negates theconcept of a ‘corrosion allowance’which assumes general or uniformcorrosion. A very good example of thisis the case of shaft buntons or hollowsections used for shaft guides. Here, hotdip galvanized steel has a major benefitin that the inner sections are zinccoated. Where welds may containdefects, or where mechanical damagecauses perforations, the subsequentingress of water to provide stagnantwater conditions are extremely harmfuland can only be efficiently protectedagainst by the interior zinc coating.Painted steel is generally not anappropriate material of construction forthe harsher mining conditions likeunderground shafts and haulages aswell as for most types of ore processingplants and material handling facilities. Ifpainted steel is used for theseconditions, the life cycle costs areusually very high as are the production,economic, safety and environmentalrisks.Procurement of hot dipgalvanized steelAs stated previously, the only apparentdisadvantage of hot dip galvanized steelin mining conditions is the perceptionby the user, owner or project manager,that the procurement process of thematerial is complex and difficult, andvery likely to cause problems inachieving project objectives.The complexity of specifying, designing,producing and transporting hot dipgalvanized steel, where this complexityrefers to the number of players in theprocess and the relationships betweenthe players does, indeed, complicatethe procurement process. Unless theprocess is properly managed andcontrolled, problems will undoubtedlyoccur, such as late delivery times,articles getting lost or misplaced,inappropriate fabrication processes thatlower the efficiency and effectiveness ofthe coating and galvanized articlesbeing severely damaged in the transportprocess. Effective management of theprocurement process is essentiallybased on ensuring that therelationships between all parties are‘open’ so as to allow an effectiveexchange of information. In most caseswhere such problems have occurred, itSpecialists inhot dip galvanizingwith quick turnaround timesHOT DIP GALVANIZINGTO APPROVED QUALITYSTANDARDS20 Dekenah StreetAlrode 1449P.O. Box 124581Alrode 1451Tel.: (011) 908-3411(011) 908-3418(011) 908-3420Fax: (011) 908-3329Volume 3 Issue 4 2006 Hot Dip Galvanizing Today 7