Low NPSHa brine pump 1

[Freon66]

Application: pumping LiBr solution to an absorption column at 0.1 psia. NPSHa available 1 to 2 feet. Target flow rate of brine 25 to 40 gpm. Any recommended pump type???

 

[arsef]

Dig a pit and install the pump. Next time elevate the column

 

[MJCronin]

arsef is right...its ugly and will cause drainage problems, but lowering the pump may be the best answer

During the preliminary layout design phase of the facility, the very low NPSHa should have been evaluated.....why was this not considered earlier ?

You can find "low NPSHa" pumps advertised.....but as I recall, the NPSH that they require is about 5 feet....

All NPSHr quoted by pump vendors are in terms of "feet of water"....if your process liquid has a significantly different density that water, you must adjust

My thoughts only.....

MJC

 

[sshep]

Can you give yourself more NPSHa by cooling the solution before pumping? If this is near boiling point even 10F cooling could give you the extra margin you need. This can sometimes be done by a small spillback to suction which is cooled down to CW temp.

 

[Freon66]

Since the absolute pressure of the brine would be 5 to 25 torr, cooling would only cut down on this vapor pressure by few to several torr which would not translate in a useful NPSH gain, hardly a fraction of one inch.

Luckily, some pumps out there work well with 1 to 2 feet of NPSH. Thus just worked around the cost and now we are ordering a reasoanbly priced one.

Thanks to all for the feedback.

Freon66

 

[tkdhwjd]

I recommend looking for low NPSHr pumps instead of digging a pit. It will likely become a confined space once you start digging and interfere with planned/unplanned maintenance.

 

[unclesyd]

Here is a pump we used in similar conditions. I don't have the exact conditions other than it was LiBr Brine.

http://www.discflo.com/P-coni.htm#

 

[dcasto]

Use a verticle can pump. The pump is lowered into a piece of vertically buried pipe to a depth slightly more than its required NPSH. The tandum seal and motor are at ground level. Afton is one of the better pumps and they have solved a lot of the thurst problems.