09 DTI Case History- DTIs Save More the $150000 - TurnaSure
09 DTI Case History- DTIs Save More the $150000 - TurnaSure
09 DTI Case History- DTIs Save More the $150000 - TurnaSure
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DIRECT TENSION INDICATORSTO ASTM F959(Hented,
At Gerald Gentleman Unit 2...Direct Tension lndicators <strong>Save</strong> Five TimesTheir Initial GostGerrleulr PowenSrnrronnd, NebraskaNebraska Public Power DistrictGolumbus, Nebraska.Engineer: Stearns-RogerDenver, GoloradoGontractor:: National Industrial Constructors, Inc.Dallas, TexasAustin Power, Inc.Dallas, Texas(CD unit I Gompared to Unit 2Unit 1 was a more extensive project since it includedcoal handling, ash handling, precipitator, serviceand office structures that serve <strong>the</strong> entire station.The sizes of <strong>the</strong> boiler building andbuilding for <strong>the</strong> two units areidentical,but <strong>the</strong> tons of strucruralsteel are slightly differentbecause <strong>the</strong> boiler and turbineequipment were purchasedfrorn different manufacrurers.In round numbers, <strong>the</strong> steelworkin <strong>the</strong> boiler and turbinebuildings of each unit can berated at I 1,300 tons.<strong>the</strong> turbinelWbtn Unit 1 of <strong>the</strong> Gerold Gentlemon Stntion enteredseruice in April 1979, it becttmt l'.ieltraskn's lorge* fossilfueledgeneratingJacility. Work on Unit 2 ltegntt Jure1977, with com,pletion in 1981. The rated genu'ntingcapaciry of each unit is 6t0,000 kilowatts. With both mitsin sernice, Gerald Gentlem.sn is <strong>the</strong> largest powar stntiort irtNebraskn.INSTALLING BOLTS WITH DIRECT TENSION INDICATORS ONBoh installntion began on tlte ground, whare ltohs oJ'propcr langth nnd qunntity were rassem.bh' inchtded n Direct Tension Indicntor - I^ed undu'thc ltoh bed - md rt hardeBohs were tightened by a two-m.an crew. One rn.nn oltset'ucd <strong>the</strong> Dit'ect Tinsiott(CD I unlque Opportunityto Study Direct TensionlndicatorsThe high-strength bolts onUnit 1 were inspected by <strong>the</strong>torque-wrench method. DirectTension Indicators were usedon Unit 2. This case historycovers <strong>the</strong> experience on <strong>the</strong>comparable portions of <strong>the</strong> twounits.
CD Owner's GonstructionManagement on Unit 2_fim Atwood, <strong>the</strong> (.ir i1Cons(ruction (-oot'tl i tt.t,,r' tirrNPPD, was rn()st irrr,,lvctl rvith<strong>the</strong> day-to-drrl ri,,rk rt tlie site.His errthusi:r.rrr l,,r' ])ircct'Ibnsion Inrlicrt,,r'. i' lilsetl uroreon <strong>the</strong> provclr rntcsrin'of <strong>the</strong>bolted joints thrn ()n cost slrvings.As rn e r,tnrPlc: llrior to <strong>the</strong>instlllation of tirc rn.rssrvc steanlilrum,-Jinr checketl l(X)'2, of <strong>the</strong>bolts in <strong>the</strong> L'nit I lroiler building.Hc bclisctl this ri'.tsessentill bccrrusc sorne rnernbershrcl been renroverl ,rnd repllceclto tttlrkc rt rtr lirt' ot Ite I' crectitlttwork. l-his chcckup took only 2l/l thvs -ri e ll wortl-rthc resultingc
MER on Direct Tension IndicatorsTbnsion Indicator is a hardened round washer withpressed oat of tbe flet sarfoce. It is a simple and accurateng and inspeaing high-strength bolts.The Direct Tension Indicator is placed on a boltwith <strong>the</strong> protrusions bearins against a hardened surface- ei<strong>the</strong>r <strong>the</strong> underside of <strong>the</strong> bolt head, or ahardened flatwasher. Figure I shows one of<strong>the</strong>most used assemblies: <strong>the</strong> Direct Tension Indicatorunder <strong>the</strong> bolt head, with <strong>the</strong> nut rurned by <strong>the</strong>wrench.Note <strong>the</strong> gap before tightening.When <strong>the</strong> bolt and nut are tightened, as shown inFigure 2, <strong>the</strong> clamping force partially flattens<strong>the</strong> protrusions and reduced <strong>the</strong> gap. When <strong>the</strong>gap is closed to <strong>the</strong> required dimension (0.015in.), <strong>the</strong> bolt and nut are properly tightened.Figure 3 shows two o<strong>the</strong>r methods to position<strong>the</strong> Direct Tension Indicator. In both <strong>the</strong>seassemblies, <strong>the</strong> Direct Tension Indicator is under<strong>the</strong> turned element, i.e. <strong>the</strong> element of <strong>the</strong> assemblythat is turned by <strong>the</strong> wrench. Note that ahardened flat washer must be used between <strong>the</strong>Direct Tension Indicator and <strong>the</strong> turned element.The required gap dimension in <strong>the</strong>se assemblies is0.005 in.J&M Turner's Direct Tension Indicator ispatented.NOTEI The Direct Tension Indicator is a precision-madedevice and should never receive anytreatfirent after leaving our plant. Also, DirectTension Indicators should not be reused.FIGURE 1FIGURE 2J&M TUrner Inc.1310 Industrial BoulevardSouthhampton, PA 18966Telephone: 215-953-118800-525-7 r93Facsimile: 2 | 5 -953-I 125Telex: 288965FIGURE 3