4 replies to this topic

[chemtan]

Hi All,

As per NFPA Standard, can I trip Firewater pump at low low level of Firewater tank? OR it should be manually switched off by operator on Alarm at Low Low level?

What is the normal practice in this regard? Would be thankful if you can please mention the NFPA Standard also.

Have a good day ahead.

[ankur2061]

Hi All,

As per NFPA Standard, can I trip Firewater pump at low low level of Firewater tank? OR it should be manually switched off by operator on Alarm at Low Low level?

What is the normal practice in this regard? Would be thankful if you can please mention the NFPA Standard also.

Have a good day ahead.

chemtan,

I had a look at NFPA 20 & it does not say anything about auto trip on source tank low level or manual stop by operator on source tank low level.

However, my suggestion would be to provide a low pressure switch on the pump suction line upstream of the pump suction strainer (if it is provided) & set it to trip at low suction pressure, which basically means that the suction line is not flooded. This will however require a careful evaluation of the setpoint to ensure that the pump only trips when the suction line is starved & no spurious trips are encountered.

Hope this helps.

Regards,
Ankur.

[chemtan]

Thanks Ankur.

I also spent the day going through NFPA 20, I did get some help from it though.

Edition 1999, clauses 9-5.2.6 & 7-5.4:
These have an exception informing that if Firewater pump is the sole source of water to sprinkler and standpipe in fire water circuit, then Fire Water pump shall not be automatically shutdown.

The firewater system that I'm working on only has hydrants and monitors. Fire water pump is now being tripped when water level is 250mm above suction nozzle... this is also reasonable because we have only couple of minutes of fire water left at that point.

Edited by chemtan, 06 November 2009 - 04:49 AM.

[luuquocdai]

Dear Ankur
I read the topic which you post in Chemforum. You said about NFPA standard. Can you share with me this standards?
My email address is luuquocdai@gmail.com
Looking forwards your email reply.
Thanks in advance.

[VikingUK]

Hi All,

As per NFPA Standard, can I trip Firewater pump at low low level of Firewater tank? OR it should be manually switched off by operator on Alarm at Low Low level?

What is the normal practice in this regard? Would be thankful if you can please mention the NFPA Standard also.

Have a good day ahead.

Firewater pumps are set to run to destruction. There should NEVER be a trip for any reason.
However most pumps have a "TEST" mode which may be switched on when running for maintenance.
This allows the pump to trip out on the same settings a normal pump would.