Hi,

I am doing fire water discharge piping analysis.
Design & Ope temp is 80 & 50degC respectively.
Seismic factor is G=0.15

In four pumps (3 working+1 standby)Following scenario considered in this analysis:
Pump-A,B,C, D @ 50degC.
Pump-A,B,C @ 50degC. & D @ 21degC
Pump-A,B,D @ 50degC. & C @ 21degC
Pump-A,C,D @ 50degC. & B @ 21degC
Pump-B,C,D @ 50degC. & A @ 21degC

Considering the above, piping load on pumps are within the allowable limit.

Now client commented to consider the occasional effects also. (W+T+P+WIN, W+T+P+U). considering this, piping load on pumps exceeding the allowable. Almost 3 times load exceeding.

Is it necessary to check the pump nozzle in the occasional cases also??
Design temp (80degC) wants to be considered in this pump nozzle checking??

Kindly give your suggestion.


Thanks,
Kannapiran.K

Hi,
Use of design temp: - Yes, Consider the loads cases at design temperature. Since you do not have much difference in operating and design temp. This might be the maximum operating temp of the system. also be aware about the stand by operating cases, as you will have some intermediate temp when it comes to stand by operating condition. YOu can not just use design temp and room temp directly..I mean this is my suggetion.

Use of occasional cases: - If you are talking about the wind then, question is do you have pumps located on outside (open area)? if the pumps are located inside the close container then no questioon of wind to be consider. If located outside, consider the wind effect and try to reduce down the loads.

For seismic case, yes you need to consider that and try to get the loads on lower side.

However, if the loads are not getting within the allowable, you have to make sure that the supporting arrangement near the pump nozzle is adequate enough to withstand the seismic effect. Generally these loads are very rare and will only cause the issue of misalingement. And as per the site normal working practice, after occurance of any such events they have to check and make sure that the alingment is porpoely maintaine for the pump shaft. This I will use to convey the client of I am having large size pumps, for smaller ones I guess we can manage with the API-610.

Comments are welcome.

Regards,
R.K.

Hi,

Thanks for your valuable suggestion RK.

Pump type is a vertical centrifugal, mounted on the Fire water Pit. Capacity:1022 cum/hr. Pump Nozzle size is 14".

We are not in the position to change the layout and pipe support types, since piping construction already had been completed.
In the final revision only, client commented to include the occasional effects (W+T+P+WIN, W+T+P+U) for pump nozzle checking.

Is there any validation/supporting document, to convince the client???


Thanks,
Kannapiran.K

hi Again,

There are no such documents (as far as I know) are avaialble. It will all be based on the experince you can convince the client. As I already stated in the above post, the occasional load failuer will only have impact on the alinegment.
Because in plants we generally have the tripping mechanism which will work when there will be abrupt earthquake....So talk with your senior and take his help/opinion to explain the things in proper way to client.

I hope this helps.

Regards,
R.K.