PD pump with multiple destination!

[shahyar]

I am just thinking what will happen if I want to use my PD pump to discharge to different locations? (Chemical injection application)
As far as I know, discharge pressure of a PD pump is determined by dishcharge point pressure.
I think pump just confused which pressure should be picked up

Thanks

 

[Artisi]

This become a complex calculation - as the head (pressure) is determined by the restricton to flow thru the discharge points and the pipeline to these points which in turn is a function of pressure acting on the discharge points and the pipeworkto these points.

 

[dcasto]

Without control valves, the PD pump will deliver to the lowest pressure point. To design this, select the highest pressure point of delivery and add a few psig to compensate for line drop (or calculate it exactly by the line and rate to that point). Then you'll need a pressure reduction valve at each of the other points. Of course, you'll need a control scheme to control rate to each point and a PSV or PCV that will recycle unused flow back to the suction of the pump.

 

[ccfowler]

shahyar,

I've used this arrangement several times quite cleanly. The key elements involved using pressure compensated flow control valves to control the flow rate to each branch and a pressure relief valve to limit the maximum pressure. There is some obvious energy waste involved, but if the pressures in the several branches are reasonably similar, the wasted energy can be quite small. The use of a suitable adjustable speed drive for the pump can minimize the energy requirement if the total flow requirement varies substantially.

 

[ccfowler]

Oops!

I intended to add that in many cases, suitable manually adjustable pressure compensated flow control valves are usually available at quite modest costs. (These "cheap" valves will not usually handle anything but clean liquids.)

If necessary, you can always jack up the costs substantially by getting fancier control valves, computer control valves, etc.

 

[shahyar]

Thanks. I had never heard about pressure compensated flow control valves.