Suction strainers for the two fire water pumps

[panteo]

Hope someone could recommend me the appropriate mesh size for suction strainer of fire water pumps.

We have installed fire water pumps recently as bellows.
1) Main pump #1: 3,000 GPM (Driven by electric motor)
2) Main pump #2: 3,000 GPM (Driven by diesel engine)
3) Jockey pump : 300 GPM (Driven by electric motor)
*. Discharge pressure: 10Bar
*. Water tank capa': 5,000 M3 ( H: 20 METER, D: 18 METER)

The problem is the suction strainers on the pumps.
It's 40mesh strainer. During the 8hours test run, the strainer clogged. We consider that the mesh size is not acceptable for the pumps.
I contacted the manufacture of the pumps and received the data as follows.
*Maximum passing sphere size through impeller, single stage:
Maker: Peerless , fire pump. cetrifugal
Motor pump: 0.95 inch (Pump model 10AEF20)
Engine pump: 1.38 inch (Pump model 8AEF15A)

With above data, it's very difficult for us to decide the appropriate mesh size for the pump.
Someone told me that NFPA does not allow suction strainer for the fire water pumps. Is that correct?

Regarding the water quality, it's relativeley clean.
The water is supplied from the make-up water for cooling water.

Best regards

 

[Artisi]

I cannot comment on the NPFA spec - The easy way to find out is - ask the NFPA authority, but I can see the logic in not having inlet strainers, from the point you have already demonstrated in your test run, a blocked strainer that rendered the pump inoperative while your wharehouse burnt to the ground..

So what caused the strainers to become blocked during your test run, the water supply for a fire pump should be from a clean source not requiring any inlet strainer. In your case as you are using the make up water for a cooling tower
it is possible that some foreign matter could in fact get into the supply source - you therefore need to exclude this by use of trash screen or similar between the pump inlet pipe and the source.


International College
Naresuan University
Phitsanulok
Thailand

 

[Artisi]

I would add to my previous note: the trash screen should be located away from the pump inlet pipe work and sized so as not to impeded flow to the pump/s when considerably fouled.

International College
Naresuan University
Phitsanulok
Thailand