Dear sir ,

When i receieve the allowable load from equipment vendor,which load combination case should compare with them ? Shall i just only use operating case (W+D+T+P) to check or need to consider (W+D+T+P+wind load / seismic load)?

Thanks for your kindly advice.

my opinion:

You should check nozzle load in
1)Hydrotest case, if your piping system need hydrotest
2)SUS case,
3)OPE case, design temperature
4)OPE + wind, if your piping system is not shielded by building.
5)OPE +seismic, if your piping is located in an area which need to be consider seismic load.
6)steam/ liquid hammer case.

etc....

Various organisations have different specifications and opinion on this. Please refer your project specification/company standard. However mostly I found as follows:

1) Static Equipments : All analysis cases (e.g. HYD, Design temp. case, Normal and maximum Operation temp. case, Sustain, and all occasional cases)

2) Rotating Equipments : All analysis cases except Design temperature case.

However some people believe that occasional loads like earthquake may only result in misalignment of nozzle in case of rotating equipments(usually inspected after such occurance and corrected) and hence they do not check nozzle loads in occassional cases also.

If we check the allowable load with the case (OPE+WIND/SEISMIC) and find it higher then vendor's provide , it means we need to change our
piping routine to meet the requirement ?

Thanks for your kindly advise

Hello oyuuyo ,

You may want to have a look at the "Piping Flexibility" posting of October 14, 2005. There were many informed opinions expressed on this topic in that thread.

If you are convinced that a creditable piping loading on the strain sensitive equipment exceeds the OEM recommendations, you have two options. 1. Contact the OEM and ask if your loadings are acceptable, or, 2. modify your design to reduce the loadings such that they will be less than those allowed by the OEM. Remember, you may be calculating loadings that will in fact be higher than those which will actually be transferred to the equipment - or, maybe not.

Remember that hydrostatic testing loadings are NOT necessarily to be applied to a vessel or a pump. The purpose of the hydro test is to test the piping for internal pressure (and leaks). For that test you might want to add temporary supports and/or you might want to disconnect the pipe from strain sensitive equipment (use a blind flange and support the end).

I would recommend that you do a "search" on this topic here on this web site as this is a question that has been asked before.

Regards, John.

Dear all ,

Thanks for your kindly help.
But I still have one problem regarding the large pipe.The allowable load (in static equipment case) for big size isn't always "good" for us.It is possible for me to meet the OEM recommendatios at ope.case(W+D+T+P);however if I consider all case need to meet the requirement , it is too tough even I re-analyze with nozzle flexibility.For piping analysis system , it is global veiw that's the reason why we need to consider any wind / seismic loading and design the guide restraints to make sure the whole stablility of piping system.For nozzle load checking , it is local view that's why the design pressure and design temperature goven all checking method ie. WRC-107..
If the basis is different from piping and equipment , how can we use the ope.case (W+D+T+P+WIND/seismic)to compare with the vendor's recommondation ?

Thanks for your kindly advise.

Oyuuyo,

When applying ope load combinations to nozzles or supports remember that you must not apply double jeopardy, i.e you cant apply wind and siesmic loads together or design temp with wind, or design temp with siesmic loads, only apply single jeopardy to your combinations.

Regards
A