System pressure

[Jeff1971]

The contractor had noticed that the minimum suction pressure was 84 psi in the original submittal. This is what the engineer had designed around and was approved (also attached). The site informed our contractor that the cold-water system pressure delivered to the booster is 61 psi and are now concerned. Is this likely to create issues or should we be OK?

From our start up report, it sounds like we were able to meet setpoint at only 30 Hz. Is there anything else we need to be worried about? The contractor specifically asked about cavitating pumps/Performance. 61psi at the suction side of the pumps should be PLENTY to avoid any type of cavitation. Can someone please assist here? the NPSH is showing less than 9 ft. so I don’t see this to be an issue if we only have 61 at the suction side of the booster system.

If system pressure is 124 psi, technically, our “Boost” pressure would have to increase from 40 psi to 63 psi. With this information, my only concern is the NOL HP. We have 5 hp motors. It looks like this pump operating with (3) pumps in parallel has a NOL of 5.19 HP. I know most motors have some sort of safety factor (1.15) so maybe we should be OK.

I appreciate your support.

 

[1503-44]

I assume your 9ft is NPSHR, in which case that looks OK.
But, not much else makes sense.

Why are you talking about 40psi? Going to 63?
What is "NOL"?
You have 3 x 5Hp pumps? Or you have 3 pumps using a total of 5.19Hp?
I probably have no idea of what you are trying to say.

Slow down and give us a good description of this system, normal and minimum inlet pressure, normal outlet pressure, flow rate, rated data and the pump curve too.



--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[LittleInch]

Nothing attached and this is a bit of a jumble of information.

You should have no issue over cavitation, but power we need to know flow

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Jeff1971]

NOL - non overloading on motor. Triplex booster system, 3x 5hp. It is jumbled due to trying to cut and paste with jumble sent to me. Rest is somewhat self explanatory.

 

[1503-44]

Sorry. I don't ask questions twice.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[georgeverghese]

So at these triplex booster pumps, absorbed power would go up by a factor of (124-61)/(124-84) = 1.58
So, what is the stated ABSORBED power in the design case when suction pressure is 84psi? See your "original submittal".