Transcription

A Guide to the Selection,Application & Functionof Pipe HangersA Global Solution25/05/2013 16:26

OVER 100 YEARS EXPERIENCE, SUPPLYING POWER GENERATION,OIL, GAS, OFFSHORE, PETROCHEMICAL, PHARMACEUTICAL,CHEMICAL AND WATER INDUSTRIES WORLDWIDEAATtppiaFcfmtaIofraMission Statement. “We are committed to being the premier choiceIn March 2011 we acquired The Paterson Group of companiespipe support company for our customers, suppliers and employees.”incorporating Bergen Pipe Support Inc., Carpententer & PatersonInc., and Process Pipe Support SystemsInc., Canada. This hasGlobal Service. Pipe Supports Limited was formed in 1968 tobrought over 100 years of US market experience to the Group.design and manufacture the Comet rangeof pipe hangers. Nowpart of the Hill and Smith Holdings PLC group of companies, PipeThe Pipe Support Group has a continual development programmeSupport Group has an enviable reputation for quality, reliability,resulting in the most comprehensive range of products availablecompetitiveness, engineering excellence and financial strength. Ourfrom one source.To ensure the products are oh the highest standard,products have been supplied to every continent of the world throughthey are produced in manufacturing plants equipped with the latestan international sales network dedicated to meeting it’s customers’technology. All of our manufacturing plants offer the same Bergenstringent quality and delivery requirements.Pipe Supports product range.From its origins in the heart of the United Kingdom, Pipe SupportsThrough this global manufacturing presence, we are able to offerGroup has grown into a worldwide organisation with manufacturingcompetitive prices for projects around the World.plants in the UK, USA China, India and Thailand.wBPScover-ARTWORK.indd 3-4

mA Guide To The Selection,Application & Function OfPipe HangersThis booklet is a guide to the business of pipe supports. It sets out to introducethe reader to the important facts and questions around supporting all sorts ofpipework from the complex behaviour in power generation, oil and gas,petro-chemical, water treatment, pulp& paper as well as the renewable energyindustries, right through to the more simple requirements of basic commercialapplications.From new people to the industry to experienced pipework designers, this guidecontains nuggets of information from our experience supplying the industryfor more than half a century. It is not intended to be an authoritative technicalmanual and should be used only as an informative text. The reader must usethe information it provides in the context in which it is written and not applyany part of this as a ‘hard & fast’ rule.It is hoped that the information will help to provide a broad overview of the topicof pipe hangers and restraints together with better understanding of what isfundamentally a relatively simple product range made complicated by the vastrange of combinations and permutations of size, load, temperature, environmentand locality!www.pipesupports.com0320/05/2013 11:02

Contents1. A Short History of the PipeSupports Group Providing a generalunderstanding of the Pipe Supports Group& the market place2. What is a Pipe SupportAn overview of the principles of theapplication and need for the product andtogether with a description of the typesVMWYVK\J[ HUK ZLY]PJL VɈLYLK 3. Spring Hangers;OL ZLSLJ[PVU HUK :WLJPÄJH[PVU VM :WYPUN Hangers – encompassing manual methodsVM ZLSLJ[PUN JVUZ[HU[ HUK ]HYPHISL LɈVY[ supports together with a review of theselection methods described in our productcatalogue and detailed descriptions of howeach of these items functions.4. Ancillary ItemsTheir application and how to specify them.Includes a review of our standard rangeof ancillary items and considers the bestcombinations for particular circumstancesHUK TVZ[ JVZ[ LɈLJ[P]L ZVS\[PVUZ 5. Dynamic RestraintsConsiders the full range of restraintsincluding snubbers & rigid struts as well astheir application. Review of information givenPU JH[HSVN\LZ ZLSLJ[PVU HUK ZWLJPÄJH[PVU methods.6. Sway BracesWhat are they, what do they do and how tospecify them. A review that goes beyond thecatalogue and looks at how to specify thesway brace of your choice.04BPS 40PP brochure.indd 4-517. Slide Bearings and IsolationProducts( YL]PL VM [OL HWWSPJH[PVU HUK ILULÄ[Z VM the Comlin range and the basics of how tospecify and design Easislide bearings.8. Cryogenic Pipe SupportsA review of the options of low temperatureinsulation of pipes and pipe supports and adiscussion of the application of High DensityPolyurethane Foam and how to include it inthe support structure.9. Steel WorkThe need for non-standard hangers andrestraints; considers the basic principlesin selecting and specifying non-standardsupport elements and the implications theycan have on other equipment.10. Basic Drafting and DetailingWhat does a drawing tell you? Who usesa drawing and what are the messages thedrawing conveys?11. SoftwareSoftware Packages make life easier forthe pipework designer. Simplifying thecalculations and speeding up the repetitiveaspects of developing drawings12. Quality Assurance and ControlEngineering standards, QA manuals andprocedures and national and internationalZ[HUKHYKZ JHU IL H TPULÄLSK OLU KLZPNUPUN and building major plants around the world,but they are fundamental for the safety andsecurity of everything that we build.www.pipesupports.comTfG sLhAJjLtrt;L/[it;sMsTYUaiMZIvLfcw

1. A Short History of the Pipe Supports GroupThe Pipe Supports Group grew out of a long established engineering andfabrication business as a result of strong relationships with the Central ElectricityGenerating Board (CEGB). \YPUN [OL ÄM[PLZ HUK ZP [PLZ [OL *,.) JVUZ[Y\J[LK THU SHYNL JVHS ÄYLK WV LY stations in England and Wales. British Industrial Engineering (BIE) built up anLU]PHISL YLW\[H[PVU MVY Z\WWS PUN VWLU TLZO ÅVVYPUN SHKKLYZ WSH[MVYTZ HUK hand railing to these major construction projects.As a result of the relationships created BIE were invited to manufacture aJVUZ[HU[ LɈVY[ Z\WWVY[ \UKLY H SPJLUJL HNYLLTLU[ [OYV\NO [OL *,.) (M[LY just a few years the engineers at BIE had developed their own, improved constantLɈVY[ Z\WWVY[ :OVY[S [OLYLHM[LY H ]HYPHISL LɈVY[ Z\WWVY[ HZ KL]LSVWLK HUK then a range of pipe clamps and complementary hardware based upon therequirements of BS3974, the British Standard for pipe supporting equipment atthe time (Superseded by EN13480 in 2004).;OLYL OH]L UV ILLU ZL]LYHS NLULYH[PVUZ VM [OL JVUZ[HU[ LɈVY[ Z\WWVY[ LHJO KL]LSVWTLU[ PUJVYWVYH[PUN UL MLH[\YLZ HUK ILULÄ[Z [V [OL \ZLY /V L]LY [OL TVZ[ PTWVY[HU[ HUK \UPX\L MLH[\YL HZ ÄYZ[ PUJVYWVYH[LK PU [OL KLZPNU VM [OL ]HYPHISL LɈVY[ Z\WWVY[ ;OL T\S[P SVJR HUK IHSHUJL PUKPJH[VY is a means of allowing the spring to be pre-set at any position throughout itstravel range.;OL T\S[P SVJR HZ UV[ PUJVYWVYH[LK PU [OL JVUZ[HU[ LɈVY[ Z\WWVY[ \U[PS [OL SH[L seventies when the Mark V support was developed. Since then this device hasMLH[\YLK PU HSS Z\IZLX\LU[ KL]LSVWTLU[Z VM IV[O [OL JVUZ[HU[ HUK ]HYPHISL LɈVY[ support. mThrough the eighties and nineties we continued to develop both our productYHUNL HUK [OL ZLY]PJLZ L LYL HISL [V VɈLY V\Y J\Z[VTLYZ 6\Y JH[HSVN\L UV VɈLYZ [OL WPWL Z\WWVY[ KLZPNULY [OL TVZ[ JVTWYLOLUZP]L YHUNL VM WYVK\J[Z and technical assistance available anywhere in the world and we are stillimproving and developing.Much like the growth of our product range, the Pipe Supports Group has grownZPNUPÄJHU[S ZPUJL ILPUN HJX\PYLK I /PSS :TP[O /VSKPUNZ 7SJ PU Initially we established a World-wide network of agents then we formed jointventures and strategic alliances which led to the beginnings of our globalL WHUZPVU ;OHPSHUK ILJHTL V\Y ÄYZ[ OVSS V ULK V]LYZLHZ THU\MHJ[\YPUN facility followed a few years later by China & more recently a large plantconstructed in India to meet the demands of the Indian domestic market.www.pipesupports.com0520/05/2013 11:02

L LZ[HISPZOLK V\Y V U ZHSLZ VɉJLZ PU :PUNHWVYL 1HWHU ;HP HU 2VYLH France, the USA and the Middle East.Most recently we added The Paterson Group, a large US based hanger businesswhose history stretches back to 1908. From that acquisition we have re-brandedour whole product range which is now known as ‘Bergen Pipe Supports’.Further expansion is planned with the latest a manufacturing facility now underconstruction in India and additional facilities coming on-line in the US over thenext 18 months.;OL 7PWL :\WWVY[Z .YV\W VɈLYZ H [Y\S .SVIHS :VS\[PVU [V TLL[ HSS WPWL supporting needs & will continue to expand where opportunities arise.a. BackgroundPeople around the world use a lot of pipe supports and restraints, spendingsomewhere in the region of 250million on ‘engineered supports’ each yearand over many Bn on standard brackets and hangers.The majority of pipes that require support and restraint by engineered hangersHYL HJ[\HSS PU LɈLJ[ SVUN [OPU WYLZZ\YL ]LZZLSZ VWLYH[PUN H[ L [YLTL WYLZZ\YLZ and temperatures. In general they connect one large piece of equipment toHUV[OLY HUK MHJPSP[H[L [OL ÅV VM Å\PK IL[ LLU [OL ]HYPV\Z WYVJLZZLZ During the operating cycle of the plant there is inevitably a change in temperature.,]LU JOHUNLZ PU [LTWLYH[\YL IL[ LLU KH HUK UPNO[ JHU OH]L ZPNUPÄJHU[ LɈLJ[Z on long pipe-lines or pipes made from non-metallic materials.Almost all materials expand or contract as their temperature is increased ordecreased. A pipe that carries steam from a boiler to a turbine heats up fromambient temperature to 570oC. This change in temperature will cause the pipeto expand by approximately 7.5mm/m, though the change is most prominentin the length of the pipe rather than in its diameter. A 100m length of pipe willtherefore increase in length by 750mm.Imagine if the pipe could not expand or contract freely, the force generatedin preventing the expansion to take place would cause substantial damageto either the pipe or the equipment at each end of it!Consider the pipe work in a power station and liken it to your own centralOLH[PUN Z Z[LT OLYL Å\PK PZ W\TWLK HYV\UK H JSVZLK Z Z[LT 0U [OL IVPSLY water is heated under pressure allowing its temperature to be increased to overÄ]L [PTLZ [OL UVYTHS IVPSPUN [LTWLYH[\YL VM H[LY (U LZJHWL VM Z[LHT \UKLY BPS 40PP brochure.indd 6-7TtawoTVoIQ6boab2. What is a Pipe oTVYsw

mthese conditions could simply cut a man in half.This steam passes through the piping into the turbine where the pressure drivesthe turbine and generates the electricity. Inside the turbine the pressure is reducedand the temperature of the steam decreases. It is then sent back to the boilerwhere it is heated up again and so the cycle continues. The greater the demandon the power station, the higher the operating pressure and temperature will be.The analogy with the central heating system is that when your heating comesVU VY NVLZ VɈ V\ OLHY HSS ZVY[Z VM JYLLRZ HUK I\TWZ HZ [OL Z Z[LT OLH[Z \W or cools-down. That is simply because the piping is expanding and contractingIL[ LLU Ä LK WVPU[Z HUK [OL UVPZLZ HYL K\L [V [OL WPWL TV]PUN HNHPUZ[ [OL QVPZ[Z HUK ÅVVY IVHYKZ VM V\Y OV\ZL 6U H SHYNL JVHS ÄYLK WV LY Z[H[PVU [OL IVPSLY TH IL HZ [HSS HZ H [LU Z[VYL building and the turbine will be perhaps 500m away from the boiler. The lengthof pipe could quite easily be 1km between the two. When you consider theamount of the expansion mentioned above, the whole pipe will grow in lengthby 7.5m.Peel away the insulation around the pipe when it is hot and you will actuallysee the pipe glowing a dull cherry red - at this temperature the metal from whichthe pipe is made becomes like plasticine. If it is not supported correctly it willsag and deform and this will cause problems for the subsequent operationof the plant. Drainage slopes will become disturbed, excessive forces will betransferred to the boiler and turbine connections and eventually the powerstation will not be able to operate.An example of what can go wrong under such situations occurred at a large coalÄYLK WV LY Z[H[PVU PU 0YLSHUK ZVTL LHYZ HNV :[LHT HZ YLSLHZLK PU[V WPWPUN where a pool of water had gathered, the pressure of the steam forced the waterthrough the pipe causing severe damage to the pipe, the supports and even thebuilding structure. A very costly repair followed!b. What type of support is required?Where expansion and contraction occurs it is important that the supportingsystem allows it to take place without exerting additional forces on the pipe.Spring hangers, both constants and variables allow the pipe to move verticallywhile hanger rods and slide bearings allow the pipe to move horizontally.Dynamic restraints control the pipe during undesirable events such as earthquakesor system disturbances like that described above.To support a piping system properly there will be a combination of rigid hangersVY Z\WWVY[Z ]HYPHISLZ HUK JVUZ[HU[ LɈVY[ Z\WWVY[Z ;OLYL PSS IL H ZLJVUKHY YLZ[YHPU[ Z Z[LT \ZLK MVY WYV[LJ[PVU [OH[ ZOV\SK UV[ OH]L HU PUÅ\LUJL VU [OL supporting system.www.pipesupports.com0720/05/2013 11:02

After deciding the layout of the main items of plant the plant designer will routehis pipe work. From this information the piping engineer will carry out the pipinganalysis. Some analysis programmes will actually specify the type and size ofspring or snubber to be used but they do little more from our point of view.The minimum information required is that the support spacing and location PSS OH]L ILLU PKLU[PÄLK" [LTWLYH[\YL SVHKZ HUK TV]LTLU[Z PSS OH]L ILLU JHSJ\SH[LK HUK TVZ[ WYVIHIS [OL [ WL VM Z\WWVY[ PSS OH]L ILLU PKLU[PÄLK From the above conditions we can identify which spring units or snubbers areZ\P[HISL /V L]LY P[ PZ UV[ X\P[L ÄUPZOLK [OLYL HZ L OH]L [V KLZPNU VY ZLSLJ[ all of the other parts of the hanger.Ideally the pipe will have been routed and the supports located beneath orHIV]L [OL I\PSKPUN Z[Y\J[\YL HUK [OL ZWHJL OLYL [OL Z\WWVY[ Ä[Z PSS IL JSLHY of obstructions - unfortunately it is rarely this easy. It is often necessary tosupply secondary steel work and to support a pipe that passes beneath anotherWPWL ;OLZL MHJ[VYZ PSS HɈLJ[ [OL JOVPJL VM [OL LX\PWTLU[ L \ZL In power stations the task of supporting a pipe is often relatively simple because[OLYL PZ X\P[L H SV[ VM ZWHJL PU OPJO [V Ä[ [OL Z\WWVY[ (KKP[PVUHS Z[LLS VYR JHU IL Ä[[LK HUK V[OLY WPWLZ VY LX\PWTLU[ JHU IL LHZPS H]VPKLK 0U [OL WL[YV JOLTPJHS PUK\Z[Y [OL WYVISLTZ HYL VM[LU KPɈLYLU[ OLYL VɈZOVYL oil and gas platforms are built to very tight space and weight constraints,which impose substantial restrictions on what can be supplied. ChemicalHUK 6PS WYVJLZZPUN WSHU[Z OH]L ZPTPSHY ZWHJL JVUZ[YHPU[Z HWWSPLK VM[LU ILPUN constructed in modular form.Driven by ever reducing space & weight demands we redesigned both our*VUZ[HU[ ]HYPHISL LɈVY[ Z\WWVY[Z HUK UV VɈLY Z\WWVY[Z [OH[ HYL HZ ZTHSS or smaller than any of our competitors. P[O [OL ]LY KPɈLYLU[ YLX\PYLTLU[Z IL[ LLU WV LY NLULYH[PVU HUK WL[YV chemical installations and the wider development of the petro-chemical sideof the Group we saw opportunities to develop new products. High densitypolyurethane foam (HD PUF) and Comlin isolation products are just two suchranges that are rarely applied to the power-generation industry.IaWsM(LZLaeiJTlSCasp0OLZHD PUF is predominantly used in the LNG, gas transportation & storage industrywhere cryogenic or very low temperatures are experienced. Comlin wasdeveloped to eliminate galvanic corrosion and reduce vibration, wear andnoise that often occurs between the pipe and the structure.b;IVed6\Y WOPSVZVWO OHZ HSZV ILLU [V VɈLY [OL WPWPUN LUNPULLY HUK WPWL Z\WWVY[ designer a comprehensive design package within our product catalogues. Thisincludes the wide range of other products such as slide bearings, insulation andisolation materials.0iam08BPS 40PP brochure.indd 8-9www.pipesupports.comw

mIt is important to remember that these are engineered product or solutions andare primarily sold to engineers.Worldwide there are perhaps only ten or twelve similar manufacturers that cansupply these products, and normally on an international bid list there will only beMV\Y VY Ä]L Z\WWSPLYZ HZRLK [V Z\ITP[ VɈLYZ (SS VM [OLZL JVTWHUPLZ L JLW[ VUL VɈLY JVUJLW[\HSS [OL ZHTL [ WL VM JVUZ[HU[ LɈVY[ Z\WWVY[ HZ L KV HUK HSS VɈLY JVUJLW[\HSS [OL ZHTL [ WL VM ]HYPHISL LɈVY[ Z\WWVY[ ( THQVY JVTWL[P[VY MYVT .LYTHU KPɈLYZ PU [OLPY KLZPNU VM JVUZ[HU[ LɈVY[ Z\WWVY[ Z\IZ[HU[PHSS MYVT [OL YLZ[ VM [OL VYSK PU [OH[ [OLPY \UP[ \[PSPZLZ a main spring opposed or assisted by two smaller springs whereas everyoneelse uses a single spring operating through a bell-crank. Recently, a competitorin the US has copied the German manufacturer and is marketing a similarJVUZ[HU[ LɈVY[ Z\WWVY[ The advantages and disadvantages of the in-line type of unit will be coveredlater in the booklet.Spring Hangers - The Selection of Variable andConstant Effort Supportsa. Why use a spring in a support?-YVT [OL WYL]PV\Z KPZJ\ZZPVU V\ PSS YLJHSS [OH[ JVUZ[HU[ HUK ]HYPHISL LɈVY[ supports are used when it is desirable to provide a support that will allow thepipe to alter primarily its height during expansion and contraction.0U [OPZ KPZJ\ZZPVU L PSS SVVR H[ [OL ZWLJPÄJ YLHZVUZ MVY ZLSLJ[PUN H ZWYPUN OHUNLY HUK [OL MHJ[VYZ [OH[ PUÅ\LUJL OL[OLY L \ZL H JVUZ[HU[ VY H ]HYPHISL LɈVY[ Z\WWVY[ -PYZ[ L PSS JVUZPKLY O L JHSS [OLZL KL]PJLZ H ]HYPHISL VY H JVUZ[HU[ LɈVY[ Z\WWVY[ HUK [OL ZPNUPÄJHUJL VM [OL VYK LɈVY[ b. Variable Effort Supports;OL VYK LɈVY[ TLHUZ L HJ[S OH[ P[ PTWSPLZ [OH[ [OLYL PZ LɈVY[ NLULYH[LK I [OL ZWYPUN [V Z\WWVY[ [OL WPWL 0U H YPNPK Z\WWVY[ H Ä LK SLUN[O OHUNLY VY WLKLZ[HS JHYYPLZ [OL WPWL HUK HS[OV\NO P[ PZ KPɉJ\S[ [V PTHNPUL [OH[ YPNPK element is exerting an upwards force identical in magnitude though opposite indirection to the weight of the pipe at that position.0ZHHJ 5L [VU HZ [OL ÄYZ[ WLYZVU [V KLÄUL [OL ILOH]PV\Y VM ZVSPK IVKPLZ HUK identify the phenomenon of gravitational force. His work showed that for everyaction there is an equal and opposite reaction such that a body will continue tomove in one direction unless acted upon by another force.www.pipesupports.com0920/05/2013 11:02

Imagine a set of kitchen weighing scales where you place one kilogram of sugaror rice into the dish and the dish settles down a few millimetres until the pointerbecomes stationary on the 1kg mark. Place more material into the weighing dishand the dish drops even lower.tAps( ]HYPHISL LɈVY[ Z\WWVY[ YLHJ[Z PU L HJ[S [OL ZHTL H [V HU L [LYUHS MVYJL HZ [OL ZJHSLZ [OL VUS KPɈLYLUJL ILPUN [OH[ L OH]L WYL JVTWYLZZLK [OL ZWYPUN in our test rig to balance the pipe weight. By so doing we have taken theuncertainty out of the installation process.As(ce OLU [OL ]HYPHISL LɈVY[ Z\WWVY[ PZ PUZ[HSSLK HUK [OL LPNO[ VM [OL WPWL PZ transferred onto the spring there should be little or no further compression orextension of the spring.When the spring is unlocked it should remain at its pre-set height until the pipebegins to move then as the pipe moves upwards or downwards the spring forceLP[OLY YLK\JLZ VY PUJYLHZLZ /LUJL [OL Z\WWVY[PUN LɈVY[ PZ ]HYPHISL HJJVYKPUN [V the displacement of the spring.c. Constant Effort Supports USPRL H ]HYPHISL LɈVY[ Z\WWVY[ H JVUZ[HU[ LɈVY[ Z\WWVY[ OHZ H TLJOHUPZT [OH[ HS[LYZ [OL JOHYHJ[LYPZ[PJ VM [OL ZWYPUN THRPUN P[ ILOH]L ]LY KPɈLYLU[S You will recall from the previous discussion that the majority of supportTHU\MHJ[\YLYZ \ZL [OL ZHTL JVUJLW[ MVY [OLPY JVUZ[HU[ LɈVY[ Z\WWVY[Z P[O [OL exception of one competitor. We shall discuss this type of support later.TKrTwtWal;tm;OL )LSS *YHUR [ WL VM JVUZ[HU[ LɈVY[ Z\WWVY[ \ZLK I )LYNLU 7PWL :\WWVY[Z utilises a rotating bell-crank connected at one side to the spring and the other tod0Jwwww.pipesupports.comw010BPS 40PP brochure.indd 10-11

hthe pipe.As an analogy consider the bell-crank as a seesaw where the spring ispressing down on one side of the fulcrum and the pipe is resting on the otherside of the fulcrum.As the pipe moves further away from the fulcrum its weight must reduce if theseesaw is to remain in balance.( M\Y[OLY HUHSVN MVY [OL JVUZ[HU[ LɈVY[ Z\WWVY[ PZ [OH[ VM H MYPJ[PVUSLZZ W\SSL carrying the pipe on one side of a wire rope and on the other a mass havingequal weight to the pipe.The tension in both sides of the rope is equal such that if the pipe movesKV U HYKZ [OL LPNO[ TV]LZ \W HYKZ P[O aLYV LɈVY[ VY JOHUNL PU rope tension.The purpose is therefore to allow the pipe to move up or downwith no change in force other than that necessary to overcomethe frictional resistance within the support.When the support is installed, the locking device can be removedand because we have calibrated the unit to the exact designload, perfect balance is achieved. (Well nearly perfect balance!!);OL [LYT JVUZ[HU[ LɈVY[ TLHUZ SP[LYHSS [OH[! [OL [LUZPVU PU the hanger rod remains constant throughout the full range ofmovement that the support can accommodate.od. Why a Variable rather than a Constant?0U ]LY IYVHK HUK ZPTWSL [LYTZ H ]HYPHISL LɈVY[ Z\WWVY[ PZ T\JO JOLHWLY [OHU H JVTWHYHISL JVUZ[HU[ LɈVY[ Z\WWVY[ ZV PM H ]HYPHISL PSS KV [OL QVI V\ YLX\PYL why pay more?mwww.pipesupports.com01120/05/2013 11:02

But what is the job that we want the variable to do?When we consider the selection criteria for a spring unit there are three basicMHJ[VYZ [OH[ PSS PUÅ\LUJL V\Y JOVPJL ¶ The weight of the pipe we wish to support. The vertical displacement due to thermal expansion or contraction thatPZ WYLKPJ[LK H[ [OH[ ZWLJPÄJ Z\WWVY[ SVJH[PVU The allowable change in force that the pipe can tolerate betweenP[Z KLZPNU SVHK HUK [OL Z\WWVY[PUN LɈVY[ ;OPZ PZ VM[LU JHSSLK [OL ]HYPHIPSP[ or allowable deviation.4HRPUN [OL VI]PV\Z WVPU[ ÄYZ[ ]HYPHISL LɈVY[ Z\WWVY[Z OH]L H TH PT\T [YH]LS range of 280mm, therefore if we know the pipe will move more than this ourZLSLJ[PVU OHZ [V IL H JVUZ[HU[ LɈVY[ Z\WWVY[ ;OLYL HYL L JLW[PVUZ OLU L TH KLZPNU H ]LY ZWLJPHS ]HYPHISL LɈVY[ Z\WWVY[ I\[ MVY [OL W\YWVZL VM this discussion we shall consider standard catalogue products.) ConstantLɈVY[ Z\WWVY[Z JHU HJJVTTVKH[L \W [V TT VM [YH]LS KLWLUKPUN \WVU [OL combination of load and travel required.But what if we want a support to accommodate only 75mm of travel and weassume the travel is downwards and the design load is 1660kg. We now havethe choice of either a constant or a variable to do the job.9LMLYLUJL [V [OL ]HYPHISL LɈVY[ Z\WWVY[Z ZLJ[PVU VM V\Y JH[HSVN\L PSS ZOV the kgf selection chart. If we consider our selection to be a V3-20, the springZ[PɈULZZ YH[L PZ RN TT 4\S[PWS TT I RN TT HUK L NL[ H JOHUNL in load of 407.25kg. If we take this from our design load we obtain a pre-setload of 1252.75kg. The minimum load of a V3-20 is 921kg and the maximumis 1681kg.;\YUPUN UV [V [OL JVUZ[HU[ LɈVY[ Z\WWVY[ ZLJ[PVU VM [OL JH[HSVN\L [V ÄUK the kgf selection chart and assuming a minimum over-travel of 25mm we arelooking for a support that allows 100mm of travel. In this case we would select a* OPJO H[ TT [YH]LS WYV]PKLZ H Z\WWVY[PUN LɈVY[ VM RN 9LMLYYPUN back to the seesaw analogy, we only want 1660kg.2050 x 100 123.5mm1660This means that we would have to increase the distance that the pipe acts fromthe fulcrum by 23.5% to give us the perfectly balanced situation we desire.We therefore have two apparently acceptable solutions when we consider onlyload and movement though with the variable being less than 50% of the costof the constant it is reasonably obvious which option the customer will take.012BPS 40PP brochure.indd 12-13www.pipesupports.comHoDbo;sI1STYZd\(tg B LTw

amHowever, when we introduce the third criterion of variability we can discard oneof the above selections.Deviation or limiting variability is expressed as the allowable change in loadbetween the pre-set condition and the design or operating load. In the majorityof cases this is normally limited to 20%.;OL ZPNUPÄJHUJL VM KL]PH[PVU PZ [OH[ P[ SPTP[Z [OL HWWSPJH[PVU YHUNL VM H ]HYPHISL LɈVY[ support and forces us to select a constant before we would perhaps want to.If we now re-consider the above example where we have an operating load of1660kg and a displacement of 75mm L]PH[PVU ʻ 5.43 x 75 x 100 24.5%1660So immediately we can exclude the V3-20 as a viable selection in this instance.There are occasions when the customer may specify other criteria that willYLZ[YPJ[ [OL HWWSPJH[PVU VM ]HYPHISL LɈVY[ Z\WWVY[Z -VY L HTWSL ZVTL 1HWHULZL ZWLJPÄJH[PVUZ VM[LU Z[H[L [OH[ JVUZ[HU[ LɈVY[ Z\WWVY[Z ZOHSS IL \ZLK OLU [OL displacement exceeds 50mm. Such requirements will normally necessitate the\ZL VM TVYL JVUZ[HU[ LɈVY[ Z\WWVY[Z [OHU PM L HWWS [OL ZPTWSL KL]PH[PVU SPTP[H[PVU (Z H N\PKL OLU ZLSLJ[PUN ]HYPHISLZ V\ JHU \ZL [OL HIV]L LX\H[PVU MVY ʻ HUK transpose it to calculate the maximum spring rate that can be tolerated for thegiven selection criteria –k max ʻ ɣ OLYL! ɣ ;OLYTHS KPZWSHJLTLU[W Design Loadwk Maximum Spring RateBy using this equation it is possible to quickly decide whether you require a V1, VY ]HYPHISL LɈVY[ Z\WWVY[ VY PM PU MHJ[ V\ ULLK [V ZLSLJ[ H JVUZ[HU[ LɈVY[ Z\WWVY[ k max 0.2 x 166075 4.427kg/mmThis indicates that our selection above could not have been viable since thewww.pipesupports.com01320/05/2013 11:02

TH PT\T ZWYPUN Z[PɈULZZ JV\SK VUS IL RN TT HUK YLMLYLUJL [V [OL ZLSLJ[PVU JOHY[ PU [OL ]HYPHISL LɈVY[ Z\WWVY[ ZLJ[PVU VM V\Y JH[HSVN\L ZOV Z [OH[ [OL ULHYLZ[ ZWYPUN V\SK IL H P[O H Z[PɈULZZ VM RN TT ;OL JVZ[ VM [OL ]HYPHISL PZ Z[PSS H SP[[SL SV LY [OHU [OL JVZ[ VM [OL JVUZ[HU[ LɈVY[ Z\WWVY[ but in this situation it falls to customer preference.e. What is a Constant Effort Support?/H]PUN KPZJ\ZZLK PU IYVHK [LYTZ [OH[ H JVUZ[HU[ LɈVY[ Z\WWVY[ KLSP]LYZ H nominally constant resisting force through its full range of travel and that itILOH]LZ ZVTL[OPUN SPRL H ZLL ZH L PSS UV SVVR H[ [OL ZWLJPÄJ [OLVY ILOPUK the functioning of the support.The dilemma felt by most people when faced with the workings of a constantLɈVY[ Z\WWVY[ PZ ¶ ºOV JHU H ZWYPUN [OH[ PZ ILPUN JVTWYLZZLK NP]L H JVUZ[HU[ load output?’Simple! It’s all in the mathematics.Consider the schematic diagram –-VY HU NP]LU ZWYPUN ZPaL - HUK 9 HYL Ä LK KPTLUZPVUZ [OL HUNSLZ ( HUK ) HYL HSZV Ä LK relative to each other and restricted within therotational range of the bell-crank. R1 however,can vary and it decides how much verticaldisplacement the rotation of the bell-cranktranslates into. FR2cosBSince the only thing that we are able to vary is R1 then W must also varyinversely with R1. If R1 is doubled W must be halved.It is that simple.This philosophy can be clearly seen by looking at the selection charts in theBPS 40PP brochure.indd 14-15H [email protected][ow;ZocosA014(sJobTwRelating back to the seesaw analogy, thesupport must always be balanced, that is tosay, the spring side of the bell-crank must be balanced by an equal force on thesupporting side of the bell-crank.WR1)tbImvfWR1cosA FR2cosBSoJmylcwww.pipesupports.comstcAHw

K emJVUZ[HU[ LɈVY[ Z\WWVY[ ZLJ[PVU VM [OL JH[HSVN\L ;HRL [OL ÄYZ[ JVS\TU" PM V\ multiply the load by the corresponding travel at any position down the columnyou will obtain nominally the same answer. The larger the spring size theless sensitive this calculation is to rounding error and the more accurate thecorrelation is.)LJH\ZL JVUZ[HU[ LɈVY[ Z\WWVY[Z HYL ZV WYLJPZLS IHSHUJLK P[ PZ ]P[HSS PTWVY[HU[ that we select and specify the most accurate W and R1 we can, otherwise thebalance is not achieved and the operation of the support is compromised.(YTLK P[O [OL HIV]L PUMVYTH[PVU HIV\[ IV[O ]HYPHISL HUK JVUZ[HU[ LɈVY[ supports the basic selection of spring size can be accomplished. With theJVUZ[HU[ LɈVY[ Z\WWVY[Z [OLYL HYL H ML IHZPJZ SPTP[H[PVUZ [V OLU ]HYPV\Z [ WLZ of support can be used. These restrictions are shown on the selection charts byboth a heavy black line and a heavy red line.Having established the spring size that we require we must then establish OPJO JVUÄN\YH[PVU PZ ILZ[ Z\P[LK [V [OL ZP[\H[PVU ;OPZ PZ KLWLUKLU[ VU [OL boundary connections of the spring unit, for example a pedestal type such asthe BM variables or the HBMCS type of constant will be used if the pipe is beingsupported from below.If there is substantial horizontal movement of the pipe it is desirable to providemaximum articulation within the hanger assembly where ideally a TS1 type ofvariable or a VS-TS3 constant using weldless eye nuts or spherical washers willfacilitate this.The whole hanger/support assembly will be discussed in the next chapter whenwe consider ancillary equipment.f. Types of Constant Effort [email protected]\ PSS YLJHSS [OH[ [OL JVUZ[HU[ LɈVY[ Z\WWVY[ THU\MHJ[\YLK I H .LYTHU JVTWHU PZ M\UKHTLU[HSS KPɈLYLU[ PU P[Z VWLYH[PVU MYVT [OL [YHKP[PVUHS ILSS JYHUR [ WL VM Z\WWVY[ ;OPZ JVTHWU VɈLY H T\JO TVYL SPTP[LK YHUNL VM WYVK\J[Z P[O only 15 spring sizes to cover their traditional range of variable supports whereaswe have 145.;OL WYPUJPWHS VM VWLYH[PVU VM [OLPY JVUZ[HU[ LɈVY[ Z\WWVY[ PZ [V \ZL H THPU JLU[YHS ZWYPUN PU [OL ZHTL H HZ H ]HYPHISL LɈVY[ Z\WWVY[ OLYL [OL ZWYPUN HJ[Z KPYLJ[S on the pipe.The schematic diagram above illustrates the principal of operation; as the largespring begins to compress the two outer springs are pushing upwards againstthe compressive load and are therefore increasing the apparent force required tocause the spring to compress.As the large spring reaches the mid-point of its travel the two outer springs areHJ[PUN OVYPaVU[HSS HNHPUZ[ LHJO V[OLY HUK [OLPY LɈLJ[ VU [OL SHYNL ZWYPUN PZ aLYV www.pipesupports.com01520/05/2013 11:02

Beyond this mid-position the two outer springsare helping to compress the large spring andso the apparent force required to compressthe large spring is reduced. The net result is aJVUZ[HU[ LɈVY[ V\[W\[ ;OL RL ILULÄ[ VM [OPZ [ WL VM Z\WWVY[ PZ [OH[ the load-line is symmetrical through t

specify and design Easislide bearings. 8. Cryogenic Pipe Supports A review of the options of low temperature insulation of pipes and pipe supports and a discussion of the application of High Density Polyurethane Foam and how to include it in the support structure. 9. Steel Work The need for non-standard hangers and