reducing for pump discharge pressure

[mohamed elgohary]

dear all,

i have a problem with discharge pressure of fire fighting pump where is ( 15 bar @ 1000gpm) and i need only 11 bar @1000gpm) ,
i have been install PRV for reduced pressure to protect the sprinkler system where the maximum allowable working pressure for sprinkler is 12bar.but the problem is for electrical pump starting at 18 bar.
is there any advice to solve mentioned problem

 

[ashtree]

Do you have a pump curve?
There could be a number of options depending on the pump and the system.Here are some but I am sure some of the other guys will come up with others. None of the options are totally satisfactory but might give you what you require.
1) Variable speed drive-probably not a good option for a fire pump.
2) Trim the impeller
3) Feedback loop between discharge and suction with control valve .
4) Operate with the discharge valve partially closed.
5) Install an orifice plate or Maric valve.


Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[LittleInch]

As usual, someone has added allowance on allowance and then added a bit so you end up with apump too big (high head) for your needs.

your best long term solution is to trim the impellor.

A shorter term solution is to fit regulating / control valves between pump and system or Pressure relief systems running back to the tank.

MAWP of the sprinklers is 12 bar, but what is max overpressure? I assume by 18 bar you mean the pressure at no flow from the pump?



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

 

[pumpking]

Littleinch has answered perfectly. Only suggestion is make it a permanent 'non tamper' solution such as impeller trims... If the worst ever happens and you need to use the pumps in anger, there is every chance settings could 'be changed' to assist in fire fighting, but implications could be massive.

We see and hear all too often with operators running plants that things are 'changed' to make the processing time a few minutes quicker - human nature...

Ash Fenn

http://www.cdrpumps.co.uk