Question about Pumps

Thealanator · Jun 25, 2012

We are in the review stage of a project to install a fluid cooler that will service four compressors. I think the compressors will require 50 GPM each for cooling. Height will be ~13 feet (3 feet from buried pipe to pump and 10 feet from pump to top pipe on the fluid cooler. We plan to install flow control valves (Griswold or equivalent) on each compressor's water outlet.

I have seen mention of steep vs. flat pump curves. Is one type better for use in this situation?

bimr · Jun 25, 2012

That discussion is somewhat irrelevant to your application. Your pump application is on the small side. Also, your pump discharge head should be relatively constant.

Your best approach is to carefully estimate the actual discharge head and select a pump that will operate in the BEP.

bimr · Jun 25, 2012

Here are some addition comments:

Flat curve: applied on closed piping systems with modulating valves. A flat-curve pump provides good pressure regulation where the flow rate fluctuates rapidly.

With a flat curve, the head rise is limited at reduced flows. A very high head rise as a result of closing control valves may cause problems. Excessive flow rates through the coils and greater pressure differences across the control valves are some of the problems that can be avoided with a flat pump curve.

Steep curve: usually for open piping systems (cooling towers), with high pressure, constant flow, multiple pumps systems. The use of steep-curve pumps is sometimes desirable because they permit some adjustment of the discharge pressure without changing impellers.

http://85.185.231.196/mekanik/CD_3/pump handbook/section 9-12.pdf

Thealanator · Jun 25, 2012

Thanks for the feedback. I failed to mention that the water circulating through the compressors will be in a closed loop. The fluid cooler looks like a cooling tower, but has separate water systems. More like a heat exchanger, I suppose.