Main­te­nance plan­ning

Save money and de­crease lead times, while still com­ply­ing with stan­dards and pro­vid­ing re­quired per­for­mance.

DEMM Engineering & Manufacturing - - EDITORIAL - BY: JANELLE PRUSHA

MANY END USERS ask for a re­view of their tech­ni­cal spec­i­fi­ca­tions to iden­tify areas adding un­nec­es­sary cost and lead time to their valve, ac­tu­a­tor, po­si­tioner and re­lated ac­ces­sory pur­chases.

They need help eval­u­at­ing if their re­quire­ments were truly needed or were ac­tu­ally more than re­quired for their spe­cific ap­pli­ca­tions. A re­view of spec­i­fi­ca­tions typ­i­cally re­veals in­stances where cost­sav­ing prod­ucts and op­tions are over­looked, along with in­clu­sion of un­nec­es­sary items and pro­ce­dures.

In many cases, th­ese mis­takes drive up cost and lead time be­cause users spec­ify “gold- plated” con­trol valves in ap­pli­ca­tions where less ex­pen­sive op­tions would work just as well. Th­ese over-spec­i­fied valves not only cost more up front, but can also be harder to main­tain and re­quire more spare parts. The pre­ferred al­ter­na­tive is to spec­ify just the valve needed (see Image 1), sav­ing time and money.

This ar­ti­cle de­scribes is­sues of­ten seen when re­view­ing end user tech­ni­cal spec­i­fi­ca­tions and shows how process en­gi­neers can spec­ify just what they need – and no more – when order­ing valves, ac­tu­a­tors, po­si­tion­ers and re­lated ac­ces­sories.

Re­duc­ing costs to green light projects

The big­gest chal­lenge fac­ing most cap­i­tal projects is cost jus­ti­fi­ca­tion. All too of­ten, a valve up­grade or new valve project is based on what has been done tra­di­tion­ally. Un­for­tu­nately, this of­ten in­cludes the use of out­dated tech­nol­ogy, un­nec­es­sary op­tions and overly strin­gent spec­i­fi­ca­tions and stan­dards, which can add lay­ers of avoid­able costs.

Process en­gi­neers are in­creas­ingly recog­nis­ing the need to in­cor­po­rate a de­sign with­out th­ese lay­ers. In­stead, they want a fit-for- pur­pose ap­proach us­ing in­dus­try stan­dards and com­mon de­signs ver­sus cus­tomiza­tion that adds cost and devel­op­ment time.

Start­ing at this zero- base by us­ing only what is nec­es­sary for the project to be safe, le­gal and re­li­able, valve ven­dors can help eval­u­ate the ap­pli­ca­tion and make value- driven choices. When spec­i­fy­ing valves, the end user, con­trol valve ven­dor and per­haps a sys­tems in­te­gra­tor or en­gi­neer­ing, pro­cure­ment and con­struc­tion (EPC) firm should eval­u­ate the com­pany’s valve re­quire­ments early in the process. All par­ties in­volved should dis­cuss how each party can help op­ti­mise the spec­i­fi­ca­tions and elim­i­nate ex­ces­sive re­quire­ments. Th­ese areas in­clude op­ti­miz­ing the con­trol valve, weld­ing and non­de­struc­tive eval­u­a­tion (NDE) spec­i­fi­ca­tions.

Some of the re­quire­ments lead­ing to un­nec­es­sary added costs and ex­ces­sive lead times in­clude:

• All assem­bly must oc­cur in North Amer­ica.

• No cast­ings from In­dia or China

• Third- party wit­ness of all weld­ing.

• The first and sec­ond points are out­dated rem­nants of a world gone by. Most valve man­u­fac­tur­ers have global fa­cil­i­ties with qual­ity equal to Amer­i­can-made prod­ucts.

For ex­am­ple, an Emer­son cus­tomer was able to waive the assem­bly re­quire­ment, sav­ing the project USD1.2 mil­lion and re­duc­ing lead time by 20 weeks.

The “no cast­ings” re­quire­ment is a re­peat of­fender in spec­i­fi­ca­tions and one that reg­u­larly meets re­sis­tance to re­moval. Many valve man­u­fac­tur­ers have global qual­ity stan­dards en­forced on all the foundries they use. Un­der­stand­ing what th­ese stan­dards are and en­sur­ing they are ac­cept­able to an EPC or end user can save 25% on project cost and re­duce lead times by up to 12 weeks.

The “third- party wit­ness of all weld­ing” re­quire­ment can also be dis­missed in al­most ev­ery case. A valve sup­plier can pro­vide weld pro­ce­dures for ap­proval by the user and EPC and skip hav­ing some­one ac­tu­ally come and wit­ness the weld­ing. The weld­ing will still be in com­pli­ance with all ap­pli­ca­ble reg­u­la­tions and stan­dards. This saved a cus­tomer USD200,000 and re­duced the lead time of the project by 12 weeks.

Un­nec­es­sary spec­i­fi­ca­tions

While re­view­ing mul­ti­ple tech­ni­cal spec­i­fi­ca­tions from cus­tomers just this past year, areas were of­ten dis­cov­ered where prod­ucts and tech­nol­ogy would be ex­cluded for rea­sons that may have been true years ago, but no longer ap­ply. Us­ing the word “shall” in a spec dic­tates no de­vi­a­tion from what is writ­ten, of­ten forc­ing ven­dors to pro­vide more ex­pen­sive so­lu­tions.

Some un­nec­es­sary spec­i­fi­ca­tions in­clude:

• Pro­vide throt­tling ball valve for pulp mill ap­pli­ca­tions.

• Pro­vide globe valves for hot gas re­cy­cle ap­pli­ca­tions.

• Cage-guided valves should not be used with high-vis­cos­ity flu­ids, flu­ids that con­tain solids or in slur­ries.

• Ro­tary valves shall have splined shafts to limit lost mo­tion.

• Stel­lite is not ac­cept­able in boiler feed­wa­ter due to at­tack of wa­tertreat­ing chem­i­cals.

Such re­quire­ments of­ten deny a plant the chance to use new or dif­fer­ent proven tech­nolo­gies.

For ex­am­ple, a high-per­for­mance but­ter­fly valve works just as well as a ball valve in most pulp mill ap­pli­ca­tions. An­gle valves can han­dle hot gas re­cy­cle ap­pli­ca­tions just as well as globe valves in many in­stances, sav­ing weight and of­ten cost and lead time.

Of­ten mul­ti­ple so­lu­tions for the same ap­pli­ca­tion, such as out­gassing, ex­ist. In th­ese in­stances, ser­vice con­di­tions, siz­ing meth­ods par­tic­u­lar to the ap­pli­ca­tion (such as bracket siz­ing), and end user ex­pe­ri­ence should help de­ter­mine what valve is the best fit for a par­tic­u­lar ap­pli­ca­tion. In out­gassing ap­pli­ca­tions, there are some cases where a more cost- ef­fec­tive

ro­tary so­lu­tion can be used, and oth­ers where a highly en­gi­neered se­vere-ser­vice so­lu­tion must be used to with­stand harsh op­er­at­ing con­di­tions.

The re­quire­ment that cageguided valves should not be used with high-vis­cos­ity flu­ids, flu­ids that con­tain solids or in slur­ries does not al­low a plant to use new trim de­signs even when they would be per­fectly ac­cept­able and even a lower cost op­tion in many cases.

The re­quire­ment that con­trol valves with spe­cial trim for noise re­duc­tion should have globe bod­ies and cage trims elim­i­nates the use of an­gle bod­ies or an even more costeffective so­lu­tion – a ro­tary valve with a noise at­ten­u­a­tor. De­pend­ing on the ap­pli­ca­tion, an an­gle valve might be a bet­ter op­tion than a globe valve, or a ro­tary valve with an at­ten­u­a­tor could re­duce noise lev­els and save money.

The re­quire­ment that ro­tary valves shall have splined shafts to limit lost mo­tion ex­cludes large sizes of ro­tary valves and scotch yoke pneu­matic ac­tu­a­tors, of­ten to the detri­ment of project costs and lead times.

As for the stel­lite re­quire­ment, in 2005 Emer­son con­cluded an in­ves­ti­ga­tion re­veal­ing that feed­wa­ter treat­ment tech­nolo­gies and meth­ods have changed sig­nif­i­cantly over the past 25 years, al­low­ing Al­loy 6 stel­lite to be an ac­cept­able so­lu­tion. And in many cases, 440C stain­less steel is more cost- ef­fi­cient and pro­vides sim­i­lar ero­sion re­sis­tance.

Ex­clu­sion of op­tions

Gold- plated specs tend to elim­i­nate less ex­pen­sive op­tions, of­ten re­quir­ing more ex­pen­sive so­lu­tions with no cor­re­spond­ing oper­a­tional im­prove­ments. Some of th­ese in­clude:

• Threaded seat rings are not ac­cept­able.

• Bon­net bolts shall not be used to at­tach ac­tu­a­tors or mount­ing brack­ets. Re­verse-act­ing spring di­aphragm ac­tu­a­tors that in­cor­po­rate seals or glands should be avoided.

Valve yokes may be cast iron for fluid op­er­at­ing tem­per­a­tures up to 800 º F, but shall be cast steel for tem­per­a­tures ex­ceed­ing 800 ºF.

The threaded seat ring ex­clu­sion and the no- bon­net- bolts spec drive a user to more ex­pen­sive valves by elim­i­nat­ing cost- sav­ing al­ter­na­tives. Stat­ing that re­verse-act­ing spring di­aphragm ac­tu­a­tors in­cor­po­rat­ing seals or glands should be avoided is in­cor­rect. If a valve must fail open, it needs a re­verse-act­ing ac­tu­a­tor.

Spec­i­fy­ing that valve yokes may be cast iron or cast steel for var­i­ous tem­per­a­tures is an in­com­plete spec be­cause it does not state if ex­ten­sion bon­nets can help with high-tem­per­a­ture ap­pli­ca­tions, which is of­ten a more cost- ef­fec­tive so­lu­tion.

It is dif­fi­cult to cap­ture all the op­tions of­fered by valve man­u­fac­tur­ers, and it is hard to know if some­thing put into a spec­i­fi­ca­tion will elim­i­nate an op­tion that could bring the over­all project cost down. This is why early re­view and op­ti­mi­sa­tion of spec­i­fi­ca­tions and re­quire­ments is crit­i­cal. If valve ven­dor tech­ni­cal per­son­nel can re­view specs be­fore the project is bid, they can walk users through the specs and iden­tify prob­lem­atic areas.

Op­ti­mi­sa­tion of work pro­cesses

The project team should eval­u­ate its doc­u­men­ta­tion re­quire­ments and their im­pact on the over­all sched­ule. In many cases, end users con­tinue to rely on out­moded and out­dated pa­per­work re­quire­ments and pro­ce­dures. The goal should be to op­ti­mize the pro­vi­sion and use of:

• Data sheets and siz­ing cal­cu­la­tions.

• Draw­ings and pro­ce­dures.

• Data packs.

• Elec­tronic data ex­change, FF2.0 to SPI.

Sub­mit­tal and ap­proval process

Op­ti­mis­ing th­ese doc­u­men­ta­tion re­quire­ments can re­sult in sub­stan­tial sav­ings. For ex­am­ple, with out­dated work pro­ce­dures, the project team must man­u­ally en­ter data and cre­ate/ mod­ify 3D con­trol valve shapes for the pip­ing de­sign. In a typ­i­cal project, this can re­quire:

• Edit­ing 500 data sheets x one hour aver­age per tag = 500 en­gi­neer­ing hours.

• En­ter­ing 500 data sheets into a com­puter sys­tem x 0.5 hour each = 250 work hours.

• Build­ing 500 valves in 3D mod­els at 0.5 hour each = 250 de­sign hours.

• Check­ing, re­vi­sions and man­age­ment of change = 250 work hours.

• To­tal: 1,250 work hours.

Many valve man­u­fac­tur­ers now of­fer com­puter- based work pro­ce­dures re­quir­ing con­sid­er­ably less time. For ex­am­ple, some pro­ce­dures al­low end users and EPCs to re­ceive data elec­tron­i­cally from the ven­dor to build pre­pop­u­lated spec sheets, 3D shapes and di­men­sions – with only a few fields re­quir­ing edit­ing – re­sult­ing in:

• Edit­ing 500 data sheets x 0.2 hour aver­age per tag = 100 en­gi­neer­ing hours.

• Im­port­ing 500 data sheets into valve siz­ing soft­ware x 0.002 hour each = 1 work hour.

• Plac­ing 500 DDP shapes in 3D model at 3 min­utes each = 25 de­sign hours.

• No check­ing nec­es­sary. Re­vi­sions and man­age­ment of change = 20 work hours.

• To­tal: 145 work hours.

Us­ing man­ual data edit­ing adds 2.5 man- hours per valve, while us­ing au­to­mated pro­ce­dures takes only about 0.3 man- hours per each valve. Au­to­mated work pro­cesses also re­duce re­work dur­ing con­struc­tion and min­imise sched­ule de­lays.



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