Dorin Popescu How Do You Consider Steam Hammer - Intergraph CADWorx & Analysis

17.3.2014 How do you consider steam hammer - Intergraph CADWorx & Analysis

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How do you consider steam hammer

Twing Member

Registered:05/11/05 Posts: 50 Loc: China

Dear particular,as far as we konw,when valve is closedquickly,there are water hammer generated eitherupstream or downstream of this valve.But refer toturbine trip,the main steam valve at the inlet of HPturbine will be closed quickly,we know there will besteam hammer act on main steam pipe which at inletside of HP.But at outside of HP turbine,is there steamhammer as same as downstream of closed valve?Howcan we consider the influence of the turbine?And didyou calculate steam hammer of Cold reheat steam ofplant?Thanks for your reply in advance!

_________________________Regards!WangXuDong

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Re: How do you consider steamhammer

Twing Member


Maybe somebody have this experience,would youplease share it with us?


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Richard

Yee Member

Registered:12/16/99 Posts: 166 Loc:Chesterfield,MO 63017

twing,

The difference between water hammer and steamhammer will hinge on the relative incompressibility ofliquid versus compressibility (and expansion) of vapor(steam). Yes, the possibility of steam hammer at thetrip valve at turbine inlet should be considered andrestraint provided.The downstream flow after the turbine will not be likethat of liquid that might have column separation withvapor pockets. The fluid is already a vapor. Theturbine extracts energy out of the steam flow.

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12/06/09 11:14 AM



#4992 - 03/03/06 07:40 PM

#4993 - 03/04/06 12:49 AM

Pressure and density are reduced at the turbine outlet.The vapor would expand to equalize a reducedpressure pocket in the downstream piping. If there is atrip valve for the reheat section of turbine then asimilar calculation of steam hammer could be doneusing the reduced pressure of reheat steam for inlet toreheat trip valve. I don't have experience with reheatturbines to say if there is an actual steam hammerobserved at the reheat outlet, or not.

_________________________R Yee

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Twing Member


Thanks RechardYee,I agree with you about differentbetween steam hammer and water hammer,and I thinkthat the turbine's rotato will influence the pressurewave in cold reheat pipe,so maybe my question is howcan we analysis steam hammer in cold reheat pipe?Best regards!


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sam Member

Registered:02/25/04 Posts: 465

Cold reheat pipe will face sudden decrease in flow fromsteam turbine outlet. As steam density and velocityare lower than the same in main steam piping, steamhammer will not be as pronounced.

It is neither very cheap to carry out this analysis, norit is required - below 500MWe units or nukes, we havenever carried out this analysis.

If turbine trip closing time is not very fast - say notbelow 100 millisecond, one may not have to bothermuch about steam hammer.

One should have a validated fluid transient software,model volumes of boiler suprheater, reheater, steamturbine stages, SRVs, trip valve, steam turbine bypasspiping & valve - all with some simplifying assumptionsbased on experience & then have to be prepared tomitigate the effect with strategic placement ofoptimized combinations of mechanical snubber & rigidstruts for both turbine trip & seismic event & co-



#4994 - 03/04/06 02:35 AM

#4995 - 03/05/06 10:23 PM

ordinate with structural group for restraint loadtransfer.

regards,sam

__________________________

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Twing Member


Thanks for your reply,Sam.As far as we know,in EBASCO's rules,if the MSV'Sclosing time is lower than 0.2 second,we must considersteam hammer to main steam pipe,but refer to coldreheat pipe, there is no limit in our rules.Our design plant is 600MW ,and the MSV's closing timeis 0.12 second,so we must consider the influence ofsteam hammer.Regards!


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sam Member


You are right; you should consider steam hammerforce.

In cold reheat piping, you will have steam hammer dueto fast closure of MSV, after that say, HPT modelledas 1 m^3 volume, NRVs, CR piping, RH (relatively largervoume), HR piping & HR control valve. Here, the MSVclosure of 0.12 s is the reason of highest steamhammer pressure rise/fall in MS/CR piping & consequentforce. If you have access to a fast transient capablesimulator or you have experienced a turbine trip fromcontrol room or data logger prints of a similar size, youcan better understand the sequence.

regards,

sam

__________________________

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#4996 - 03/06/06 09:28 AM

#4997 - 03/06/06 10:36 PM

#4998 - 03/07/06 04:48 AM


Twing Member


Sam,Thanks for your reply,it's so helpful to me.My trouble is that I have no any data about turbinetrip and we all use pipenet transient(peoducted bysunrise of U.K) to calculate steam hammer,but there isno model of turbine in it.so our result of CRP steamhammer will ignore the influence of turbine's rotato,butI think it's an important thing to CRP's steamhammer.Would you please tell me which transient softyou use?Best regards!


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sam Member


Last four years I am away from power plant design.I have used our organization's own software. Everygood E&C firm in power sector has at least one suchsoftware calibrated with industry standardbenchmarks.

You can use BOS FLUIDS in public domain software,Bechtel's GAFT for single phase steam hammer & wellknown nuclear safety code RELAP5 for multiphase fluidtransients.

But, with PIPENET-Transients, you can have have thisanalysis done with some small loss of accuracy whichyou can cover up by some factor of safety.

regards,

sam

__________________________

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Twing Member


Thanks for your patient explain,Sam.Maybe I should go to some power plants to collectmore data about turbine trip.Heretobefore,I have noany data about steam hammer in CRP,and I have nothear any accident about CRP steam hammer,maybe our



#4999 - 03/08/06 03:15 AM

#5000 - 03/08/06 04:25 AM

design is too safety coefficient.But who can promisehis desin is safe absolutely?At least I can not nowbecause I have not learn about the stage of steamhammer in CRP.Thanks for your reply again.Best regards!


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Twing Member


According to ASMEB31.1 Appenix V-10.2,it's asfollows"Piping response to these momentaryunbalanced loads can be significant in high pressuresteam systems,such as main steam,hot and coldreheat steam,bypass and ..........",but it'snonmandatory,so we have two choice:one is considermore and pay more,another is ignoring the steamhammer in CRP to save some cost of snubber ormaterial.Which one choice would you select?Thanks for your kind attention!


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sam Member


You have to realize your responsibility of maintainingintegrity against collapse. due to primary load, ofpiping after full load trip; for an unitsize of 600 MW, itmay be costly to ignore steam hammer just to savecost of rigid struts, mechanical snubber, associatedcivil structural strengthening & analysis.

You must have some reference plant design / mentorsto use as seed for calculation.

Making piping flexible to meet steam turbine allowableloads & stability calculations are for better operability.To have good slopes & steam drain facility in piping &code comliance for steam hammer is for avoidingdeformation & accident post full load trip. None can beignored.

regards,sam



#5001 - 03/09/06 03:49 AM

#5002 - 03/09/06 05:09 AM

#5003 - 03/09/06 08:36 AM

__________________________

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LeonardStephen

Thill Member

Registered:06/17/00 Posts: 38 Loc: P. O.BOX 36132,DALLAS, TX.7...

sam Member Member # 884 March 07, 2006, 02:50AM: Message edited by: sam

RE: You can use BOS FLUIDS in public domainsoftware.

TECHNICAL NOTE:BOS FLUIDS by Paulin Research Grouphttp://www.paulin.com/

My understand is not public domain software.

_________________________LEONARD STEPHEN THILLSENIOR ENGINEER

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sam Member


I am very sorry for wrongly writing 'Paulin ResearchGroup's BOS FLUIDS as public domain software.

What I wanted to write that it is a software whoseuser license can be bought unlike the proprietarysoftwares of A/E firms.

It's my mistake, I accept.

regards,sam

__________________________

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Twing Member


Dear sam,you are right,none should beignored,especially we have no data about steamhammer in CRP.But you know,stress engineer considermore about the safty of the piping system,but theowner cosider more about the cost.If there is nosnubber on CRP in all his other plants,the owner will



#5004 - 03/23/06 04:26 PM

Hop to: CAESAR II Go

ask why we use it here,I shall only answer:"more costmean more safty." so maybe it's only my business,but Iwant to know who have used snubber to preventsteam hammer of CRP in our form.If all not,at least wecan know that is not more important in our analysis.Sam,Thanks for your kind again,you help me a lot.


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GeoffreyD StoneFIMechE

C.Eng Member

Registered:01/11/06 Posts: 3 Loc:Australia

Twing, If you have some idea of the steam hammerload from minimum to maximum you could use youravailble software to undertake a sensitivity analysis.This could take into account the turbine rotation etc.

If this shows no problem over a large range ofconditions you can justifiably go no further. If you findthere are problems you may need to engage aspecialist company to show you how to analyse it.Then in the future you can invest in the correctsoftware and perhaps do this analysis yourself.

_________________________Geoffrey D Stone

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Dorin Popescu How Do You Consider Steam Hammer - Intergraph CADWorx & Analysis