09 DTI Case History- DTIs Save More the $150000 - TurnaSure

DIRECT TENSION INDICATORSTO ASTM F959(Hented,

At Gerald Gentleman Unit 2...Direct Tension lndicators Save 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 the entire station.The sizes of the boiler building andbuilding for the two units areidentical,but the tons of strucruralsteel are slightly differentbecause the boiler and turbineequipment were purchasedfrorn different manufacrurers.In round numbers, the steelworkin the boiler and turbinebuildings of each unit can berated at I 1,300 tons.the turbinelWbtn Unit 1 of the 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 the 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 the Dit'ect Tinsiott(CD I unlque Opportunityto Study Direct TensionlndicatorsThe high-strength bolts onUnit 1 were inspected by thetorque-wrench method. DirectTension Indicators were usedon Unit 2. This case historycovers the experience on thecomparable portions of the twounits.

CD Owner's GonstructionManagement on Unit 2_fim Atwood, the (.ir i1Cons(ruction (-oot'tl i tt.t,,r' tirrNPPD, was rn()st irrr,,lvctl rviththe day-to-drrl ri,,rk rt tlie site.His errthusi:r.rrr l,,r' ])ircct'Ibnsion Inrlicrt,,r'. i' lilsetl uroreon the provclr rntcsrin'of thebolted joints thrn ()n cost slrvings.As rn e r,tnrPlc: llrior to theinstlllation of tirc rn.rssrvc steanlilrum,-Jinr checketl l(X)'2, of thebolts in the 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 the protrusions bearins against a hardened surface- either the underside of the bolt head, or ahardened flatwasher. Figure I shows one ofthemost used assemblies: the Direct Tension Indicatorunder the bolt head, with the nut rurned by thewrench.Note the gap before tightening.When the bolt and nut are tightened, as shown inFigure 2, the clamping force partially flattensthe protrusions and reduced the gap. When thegap is closed to the required dimension (0.015in.), the bolt and nut are properly tightened.Figure 3 shows two other methods to positionthe Direct Tension Indicator. In both theseassemblies, the Direct Tension Indicator is underthe turned element, i.e. the element of the assemblythat is turned by the wrench. Note that ahardened flat washer must be used between theDirect Tension Indicator and the turned element.The required gap dimension in these 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