problems with NSPH for piston pump
problems with NSPH for piston pump
(OP)
Dear All Good day,
our case is :we have a piston pump in platform used in TEG package , this pump start to have problem because of NSPHR .
My question could we use a booster pump up stream the piston pump? If yes where should I pay attention to?
our case is :we have a piston pump in platform used in TEG package , this pump start to have problem because of NSPHR .
My question could we use a booster pump up stream the piston pump? If yes where should I pay attention to?





RE: problems with NSPH for piston pump
some more data would be useful - type of pump, number of cylinders, flow, pressure, temperature, why you're getting NPSH issues (fluid lift?)
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: problems with NSPH for piston pump
First look to see if it is possible to modify system to allow for more inlet pressure (changing elevations, less drop across filters, etc.). Failing that, you must look at the end-user spec requirements however, you may be forced into using an API pump as the booster....very expensive.
In that case, it may be cheaper to get a bigger piston pump so that it can run slower and require less NPIP (that is the term (Net positive Inlet Pressure) the authorities are telling us to use for positive displacement pumps in lieu of NPSH).
RE: problems with NSPH for piston pump
Thank you for your reply . Please check the attachment s for more information you asked for please advice sooner
RE: problems with NSPH for piston pump
Or check to see if you can use other than an API pump as charging pump.
RE: problems with NSPH for piston pump
Could you explain to me the second option more please
RE: problems with NSPH for piston pump
The real consideration is the seals in the charge pump and making sure you have compatible with TEG, and good drip pan system to collect any inadvertent leakage.
Figure out the capacity and head needed to "charge" the Peroni and ask recommendations of a couple of good pump distributors in your area.
RE: problems with NSPH for piston pump
RE: problems with NSPH for piston pump
The 30% over comment I know is just a rule of thumb, but opens up one of the least understood, and researched areas in all of pumping: feeding the suction side of a valved recip pump.
I'm guessing this rule of thumb came about at some point as a safety margin after a "properly sized" centrifugal was in fact undersized after all and ended up running out on the curve and ITSELF being starved. Just a guess.
I do know that, at some point of the recip being "overfed", there is risk of overcoming the spring tension that closes the suction valve and it stays open a bit too long in the cycle. Instead of closing at the end of the suction stroke, it will stay open a tad bit long into the discharge stroke and you will get leakage back through it. This can lower volume out of the recip and in abrasive services (especially drilling mud) can lead to washing out the suction valve prematurely.
Very few studies done on what the proper NPIP is for a recip pump.....I think because the term acceleration head scares so many people. Sure does me.
RE: problems with NSPH for piston pump
RE: problems with NSPH for piston pump
Correct what you write about the spring tension and the backflow but the loss in flow is rather negligible as long as the valves are not worn out. The valves close as soon as the plunger moves forward as it (the plunger) always creates a pressure higher than the suction pressure as long as the fluid is incompressible.
RE: problems with NSPH for piston pump
I have heard the 30% rule before (actually just have heard "oversized"); and it is surely better for the charge pump to be oversized than undersized! And yes, it is correct that the charge pump will be feeding two cylinders rather than one, for a time.
So yes, I think it is agreed that oversized is good, I'm just thinking about the limits: where does oversizing start to hurt performance and why.
I recall as a young hand in the oilfield having suction valves pushed open so forcefully that the discharge stroke could not close them anywhere near in time and a very appreciable amount of flow was lost (as well as very rough treatment of all parts concerned). In this case, we would put either a stronger spring, or double spring on top of the suction valve to make sure it closed quickly. But we were young and dumb, and that made the problem go away so we never considered further. The point is, there is a line you cross when oversizing the charge pump that can make bad things happen.
Mainly, what I don't get is why there have not been more published studies on exactly how to properly charge a recip. There are hundreds of incredibly intense technical papers written around every imaginable topic on the suction side of a centrifugal. Not so with the poor recip pump.
Again, I say people are scared of acceleration head.
RE: problems with NSPH for piston pump
I am really thank you very much for your kind support.
please could tell how the 30% calculated for triplex pump?
and where could we consider that the flow is over sized so much and will effect our pump ?
Many thanks for your help
RE: problems with NSPH for piston pump
Johnny Pellin
RE: problems with NSPH for piston pump
Would you mind elaborating on what this is, sounds very interesting. Yes, anything to forego a booster pump would be a huge plus.
RE: problems with NSPH for piston pump
It might be worth asking mustafa2014 what symptoms lead them to believe that NPSH is the problem. Is it reduced capacity? Is it vibration and noise at the pump? Is it vibration and noise in the piping? There have been papers written that studied the effects of cavitation is piston pumps. Cavitation, in and of itself is not destructive in a piston pump like it can be in a centrifugal. But, if there is high vibration in the pump or piping, it can cause other problems. The OP stated that NPSH is the problem. And we took him at his word that this was the problem. Perhaps we should ask more questions about how he came to that conclusion.
Johnny Pellin