Centrifugal horizontal split case fire pumps - Suction
Centrifugal horizontal split case fire pumps - Suction
(OP)
I can only find the following references regarding the requirement that a centrifugal horizontal split case fire pump must have a positive suction supply.
6.1.2* Application. Centrifugal pumps shall not be used where a static suction lift is required.
A.6.1.2 The centrifugal pump is particularly suited to boost the pressure from a public or private supply or to pump from a storage tank where there is a positive static head.
I have a location with six 2,000 gpm @ 100 psi centrifugal horizontal split case fire pumps. I recently performed the annual flow test activities. This is a new customer for us, but the pumps have been in place for 15+ years. They area all arranged to take suction from an open top reservoir (approximately 100 ft. x 100 ft.) which is 15 ft. deep. The reservoir water level is 1 ft. above the top of the fire pump, so the STATIC suction pressure is 0.5 psi when the reservoir is completely full. Technically (based on the text listed above), this is acceptable based on NFPA. I do not think this arrangement should be considered acceptable. Centrifugal horizontal split case fire pumps are intended for applications which have positive suction pressures. What will happen after the deluge systems have operated for 30-60 minutes and the reservoir is 5-10 ft. below full?
Has anyone else seen a similar arrangement? Is this an acceptable arrangement based on NFPA?? Are there any NFPA requirements which I am missing which indicate this arrangement is unacceptable??
Thanks in advance!
6.1.2* Application. Centrifugal pumps shall not be used where a static suction lift is required.
A.6.1.2 The centrifugal pump is particularly suited to boost the pressure from a public or private supply or to pump from a storage tank where there is a positive static head.
I have a location with six 2,000 gpm @ 100 psi centrifugal horizontal split case fire pumps. I recently performed the annual flow test activities. This is a new customer for us, but the pumps have been in place for 15+ years. They area all arranged to take suction from an open top reservoir (approximately 100 ft. x 100 ft.) which is 15 ft. deep. The reservoir water level is 1 ft. above the top of the fire pump, so the STATIC suction pressure is 0.5 psi when the reservoir is completely full. Technically (based on the text listed above), this is acceptable based on NFPA. I do not think this arrangement should be considered acceptable. Centrifugal horizontal split case fire pumps are intended for applications which have positive suction pressures. What will happen after the deluge systems have operated for 30-60 minutes and the reservoir is 5-10 ft. below full?
Has anyone else seen a similar arrangement? Is this an acceptable arrangement based on NFPA?? Are there any NFPA requirements which I am missing which indicate this arrangement is unacceptable??
Thanks in advance!





RE: Centrifugal horizontal split case fire pumps - Suction
RE: Centrifugal horizontal split case fire pumps - Suction
If you run the water level down the pump will start taking in pockets of air and you could burn out the pump during a fire.
RE: Centrifugal horizontal split case fire pumps - Suction
Thanks to David CR.....I was not aware of the text you referenced. These sections are very helpful and relevant.
RE: Centrifugal horizontal split case fire pumps - Suction
Thanks again to David CR
RE: Centrifugal horizontal split case fire pumps - Suction
The 1' of water above the pump suction would certainly act as the priming water. With the bottom of the resevoir 14' below the pump suction, the maximum lift required would be just over 6 psi, well under atmospheric pressure in most areas.
Do the pumps have suction pipes that extend down toward the bottom of the resevoir? Was the applicable version of NFPA 20 something prior to the 1974 edition? If both answers are 'yes', the installation may have met the original design standards.
Having said all that, I gotta agree with everyone else - not a good design.
RE: Centrifugal horizontal split case fire pumps - Suction
Than God it wasn't all in my mind!
I started my sprinkler career in the mid 1970's and I remember reading the section on suction lift and priming water. I also remember seeing a couple large split case horizontal pumps, it was an oil refinery that was hurriedly built during the second world war, taking suction from Lake Erie just east of Toledo. Digging around old WW2 built sites makes one feel like an archaeologist because you never know what you will uncover.
These pumps were finally removed from service in the 1990's and I am thinking the water level had to be further down than just foot or two especially when there is a strong southwest wind which I've seen drop the level two or three feet piling it up on the Canadian side.
If the pump was installed prior to the mid to late 70's it's probably alright.
RE: Centrifugal horizontal split case fire pumps - Suction
This forum is very beneficial.
Thanks again to each of you for your input!