Analyzing Potential Overpressuring by a Pump

[MAPower]

Hi,

I've been asked to review if a particular pump can overpressure a piping system. The piping system is 300# class and the pumps are centrifugal type pumping anhydrous ammonia. What are the different things I need to look at? Is it just shut-off head? Or do I have to look at the pump curve.

New to pumps here, thanks for the help.

 

[JJPellin]

The maximum discharge pressure that the pump can produce is found by adding the maximum suction pressure to the shut-off head. I am a little bit confused by the wording of your questions since I would typically get the shut-off head from the pump curve. Of the two numbers that you have to add together, the pump head is the easy one. Figuring out the maximum suction pressure to the pump can be trickier. If the pump takes suction from a vessel that is PSV protected, you can be conservative and use the PSV setting plus any head pressure from the PSV down to the pump. If the suction comes from some other system, you have to go to that system and figure out what the maximum pressure would be from the other system.

Johnny Pellin

 

[MAPower]

Thanks for the response.

The suction is coming from a tank, so I can get that information pretty easily. I do not have a pump curve on the pump. All I have at this moment is the shut-off head (someone told me). Thanks again.

 

[BigInch]

Well, (in lieu of std. rant) its not only the pump that contributes to maximum pressure. Be sure to add any surge pressures.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[SeanB]

Since you don't have a pump curve you can estimate the pump shut off pressure and compare what you calculate to the information that has been provided to you. Normally we specify pumps with a 25% rise to shut off. So if you know your delta P at your normal flowrate, multiply that by 1.25 to give you the shut off head.

 

[pleckner]

Sorry but there is no reason you can't get a hold of a pump curve. Get the model and serial number from the nameplate and either call the manufacturer and/or go to their website. If the nameplate is in bad shape, then you should at least be able to get the manufacturer's name and I would bet you can find out the model of the pump. Check your maintenance shop, they must have records on this pump.

Note that if your facility falls under OSHA PSM requirements, you must have this information to document that this calculation (blocked-in) was checked against the PSV sizing.

 

[Yorkman]

One concern that I would voice when deadheading any pump but even more so with ammonia is the heat heat build up in the volute if alloweed to run for an extended time. I have seen pump casing crack/break when a dead head pump had its discharge vavle open and then get shocked with cold water. Cold liquid ammonia hitting that casing and cracking it opens up a whole new world of death and destruction. Just my 2 cents

I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI