design considerations for aluminum hull structures - Ship Structure ...

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-74-(b)MechanicalTensile Strength 65,000 to 75,000 PSI(As C~St)Yield Strength 28,000 to 38,000(c)PhysicalElongation 35 to 50(per cent in 2 inches)Reduction in Area 50 toboBrinnell Hardness 120 to 150AIST 30L,and 316 stainless steels could be used but are not consideredto be as good for this service as the 2S per cent nickel - 20 per centchrome stainless steel.Aluminum Alloy 3S6-T6 has been used with apparently excellent resultson the hydrofoil DENISON. This material has excellent corrosion resistance,good machinability and excellent pressure tightness. This alloy has thelollowing properties:(a)ChemicalSiliconIronCopperManganeseMagnesiumZincTitaniumAluminumPer Cent6.5 tO 7.10.5 Max.0.2 Max.0.10 Max.0.2 to 0.40.20 Max.0.20 Max.Remainder(b)MechanicalUlti3nateStrengthYield Strength33,000 PSI22,000 PSIThis alloy has one disadvantage incent for sand castings and perhapsmaterial would have to be approvedU.S. Coast Guard, since it=use onthat the elongation is only about 6 per12 per cent for permanent molds. Thisby the American Bureau of Shipping and theDENISON was approved only for that specific case.The trim material will have to be carefully selected, depending onthe material used for the valve body. H aluminum valves are used, then304 or 316 stainless steel can be considered. If the staimess steelvalves are used then monel 400 could be considered as the trim material.Valves of al~inw alloys suitable for use in sea water are notreadily available and are very difficult to obtain.Cbst data is based on the actual aluminum alloy used, size and quantity.Valves of 2!JNickel - 20 Chrome, and 304 or 316 stainless steel are morereadily available in sizes 1/2 inch to 6 inches. A cost comparison ofaluminum alloy versus stainless steel valves is as follows:
-75-SizeIFSPressureServiceLbs304, 316 and2S Nickel - 20 ChromeStainless Steel$/Each3S6-T6Alum~ruunAlloy$/Each3ItFlgd4“ Flgd6“ Flgd81’Flgd3“ Flgd4“ Flgd6“ Flgd1so150150150150150150GateGateGateGateGlobeGlobeGlobe263.00376.00610.0040; .00h78 .00809.00268.00389.00622.00809.00273.00512.00891.00Cast stainless steel, 25 Nickel, 20 Chrome valves are recommended.However, as stated above, special approval to use materials other thanthose listed in the Regulations will have to be obtained from the AmericanBureau of Shipping and the U.S. Coast Guard.- The ballast system for the steel CHAIJXNGER consistsof fcRw- mch reams through the tanks, one each in the port and starboardupper wing tanks and double-bottom tanks, with 8 inch branches to eachtank. The necessary piping connections are provided in the engine room tofill and empty the tanks. In addition, the upper wing tanks are fittedwith 6 inch shell valves to permit rapid deballasting directly overboard bygravity. All pipe within the tanks is Schedule 80 galvanized steel.Several different materials may be used in the ballast system forthe aluminum hull ship, with the ultimate choice being based on the balanceof installed cost versus compatibility with aluminum and reliability andmaintenance cost. The different piping materials considered are aluminum,black steel, galvanized steel, fiberglass reinforced plastic, PVC coatedsbeel pipe, 90-10 copper nickel alloy and stainless steel pipe. Each ofthese materials have advantages and disadvantages which will be discussed.An aluminum pipe system with aluminum valves has the basic advantageof being completely compatible with the surrounding hull structure. IL isweldable and bendable and there is extensive experience in its use andinstallation. Because of its corrosion resistance Schedule 40 thicknesscan be used for ballast piping service. Its major disadvantage is its highinitial cost.A black steel pipe system with black steel or nodular iron valves hasthe advantages of low material cost and is easily fabricated, bent andwelded. However, it is not compatible with the aluminum hull structure,therefore, many measures have to be taken to protect the structure asfollows:(a)(b)(c)(d)Each bulkhead penetration has to be a thick aluminum spool piece.On each side of this bulkhead spool piece another thick aluminumspool piece has to be fitted to act as a waster piece to protectthe bulkhead fitting.Cathodic protection using expendable aluminum anodes must befitted within the tanks to protect the aluminum structure.Pipe supports must be carefully insulated.
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CONTENTSI.. II.III.Iv.v.VI ●VII.I
Page 9 and 10:
LIST OF FIGURES(Cent’d)FIGURE NO.
Page 11 and 12:
I. INTRODUCTIONThis report summariz
Page 13:
art in fabricating and maintaining
Page 16 and 17:
MONTEROSSO GRANA /17VALGRANA / CARA
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-8-Numerous references have been re
Page 20 and 21:
.10.TABLE 2. Mechanical Properties
Page 22 and 23:
TABLE 2 Mechanical Properties of Al
Page 24 and 25:
TABLE 3 Mechanical Property Limits
Page 26 and 27:
-16-l?igures5, 6, 7 ati 8 present f
Page 28 and 29:
-18-ti-’”’-”-””””-L
Page 30 and 31:
-20-60 .r---.— ..,.— -——,L-
Page 32 and 33:
.22-each stress level, rate of load
Page 34 and 35: -24-!Z456-H321 = 0.485083-H321 = 0.
Page 36 and 37: -26-(c)Members with partial or cont
Page 38 and 39: -28-AllOyS 5083 and 54.56(~ content
Page 40 and 41: -30-The previous paragraphs have de
Page 42 and 43: -32-The problem of cargo hold abras
Page 44 and 45: -34-The question of residual stress
Page 46 and 47: .36-Each alloy was given a relative
Page 48 and 49: -38-GENERAL OBSERVATIONSFYior to a
Page 50 and 51: -40-The question of comparative imp
Page 52 and 53: -42-(d)(e)Poor quality welds due to
Page 54 and 55: -44-The ABS criteria noted above we
Page 56 and 57: -46-DNV would consider fatigue in e
Page 58 and 59: -48-is less, for the exposed side s
Page 60 and 61: Equation (2):-50-Hu1l SMa~um = Hull
Page 62 and 63: -52-Another aspect of vibrations wh
Page 64 and 65: -54-000000000Bottom Shell PlateSide
Page 66 and 67: -56-at the deck and keel. This stre
Page 68 and 69: -58-AT is the change inUT= Thermal
Page 70 and 71: -60-SUl@!ARYAll parties contacted f
Page 72 and 73: -62-(c)(d)(e)(f)T~e exterior side o
Page 74 and 75: TABLE 12 Aluminum Bulk Carrier - Su
Page 76 and 77: .66-INSUT.ATION AND SHEATHINGShell8
Page 78 and 79: -68-(b)(c)(d)(e)(f)(g)(h)(i)(j)At l
Page 80 and 81: -70-IIF.INSTALLATION OF SYSTEMS AND
Page 82 and 83: Rudder Assembly -carrier should be
Page 86 and 87: -76-(e)The steel piping must be of
Page 88 and 89: -78-Other Piping Systems and Valves
Page 90 and 91: -80-struetion for the aluminum hull
Page 92 and 93: -82-Large heavy type machine~ must
Page 94 and 95: suffers attack in an alkaline envir
Page 96 and 97: -86-REPAIRSObtaining proper repairs
Page 98 and 99: -88-The design of the midship s~cti
Page 100 and 101: -90-assuming the increase is applic
Page 102 and 103: LIGHT SHIP WEIGHT ESTIMATE-92-In or
Page 104 and 105: -94-TABLE 20 Aluminum Bulk Carrier
Page 106 and 107: TABLE 22 Trim and StabilityFull Loa
Page 108 and 109: -98-TABLE 24 Price of Steel Bulk Ca
Page 110 and 111: GaseNumber. . . -.,- .TABLE 27 Comp
Page 112 and 113: -1o2-TABLE 28CarriersComparison of
Page 114 and 115: 12 ---n..T.[T7%l,=LEGS IU ORF=ErY
Page 116 and 117: -106-such as iron ore, on two of th
Page 118 and 119: -108-7)is,zg~ gg~5e mzz~E’4E!~K2j
Page 120 and 121: -11o-(a)(b)(c)(d)Inerting system fo
Page 122 and 123: -112-fatigue, particularly in the p
Page 124 and 125: -114-2k* Installation of Systems an
Page 126 and 127: -116-LIST OF REFERENCES(7)Fatigue P
Page 128 and 129: -11.8-LLST OF REFERENCES(Cent’d)(
Page 130 and 131: -120-ADDITIONAL SOURCES OF INFORMAT
Page 132 and 133: -122-redistribution of the still wa
Page 134 and 135:
-124-APPENDIX BEXCERPTS FROMRULES A
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-126-92.07-10(d)(~) Interior stairs
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-128-~gE1+0102030- .. ..—405060
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ectintyclassification4KEYWORDSROLEL
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SHIP STRUCTURE COMMITTEE PUBLICATIO
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