Centrifugal Pump Air Release
Centrifugal Pump Air Release
(OP)
Hi guys,
Currently we are installing a process plant that features a closed hot water loop. There is effectively an atmospheric holding tank, that loads out directly to the suction of a centrifugal pump discharging to the various process applications. The flow in the supply line not used/returning from a heat exchange application then returns to the holding tank and the process repeats etc etc. The tank is complete with low level switches etc to ensure pump doesn't run dry.
A question popped up today around the installation of an air release valve on the discharge of the centrifugal pump. This is highlighted in a rev cloud on the attached sketch. I am curious as to why this would be required, given there is one on the return header (ultimately the same line) which is also the highest point in the system. A few things i want to run by you are:
- is an additional air release valve required on the immediate pump discharge or is the current air release adequate to protect the pump?
- if we were to add an additional air release, is this the best place for it?
Effectively i dont think it is required and the current set-up is adequate. Just want to check if i am missing something
Thanks in advance
Currently we are installing a process plant that features a closed hot water loop. There is effectively an atmospheric holding tank, that loads out directly to the suction of a centrifugal pump discharging to the various process applications. The flow in the supply line not used/returning from a heat exchange application then returns to the holding tank and the process repeats etc etc. The tank is complete with low level switches etc to ensure pump doesn't run dry.
A question popped up today around the installation of an air release valve on the discharge of the centrifugal pump. This is highlighted in a rev cloud on the attached sketch. I am curious as to why this would be required, given there is one on the return header (ultimately the same line) which is also the highest point in the system. A few things i want to run by you are:
- is an additional air release valve required on the immediate pump discharge or is the current air release adequate to protect the pump?
- if we were to add an additional air release, is this the best place for it?
Effectively i dont think it is required and the current set-up is adequate. Just want to check if i am missing something
Thanks in advance





RE: Centrifugal Pump Air Release
My advice would be to not do it.
Regards
Ashtree
"Any water can be made potable if you filter it through enough money"
RE: Centrifugal Pump Air Release
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(2B)+(2B)' ?
RE: Centrifugal Pump Air Release
If it is an ARV, it does seem a bit OTT I must admit.
Is the flow velocity very low? So long as you have >1m/sec in pipework you should be able to flush out air pockets and then only need to put vents or an air release valve on the HX.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Centrifugal Pump Air Release
I don't see any harm with having a second ARV. It's a cheap preventative measure to minimize damage to the process equipment and extend the life of said equipment.
Personally, I'd rather see an air separator upstream of the pump to protect the pump and process equipment. Especially when dealing with an atmospheric tank as described (lots of potential for entrained air in that tank).
RE: Centrifugal Pump Air Release
RE: Centrifugal Pump Air Release
The return line is top entry to the buffer tank as shown, at approx 4m and thus higher than the high level switch/level in the tank. Velocity in the line is 1m/s. I don't think aeration from the tank is likely from the return line injection. The water in the tank should have time to settle a bit. I assumed the current air release prior to entry back into the tank was primarily for start-up, with minimal air being able to re enter the system during operation.
If protection of pump/heat exchanger should be considered then shouldn't the air relief be on the pump suction in theory
RE: Centrifugal Pump Air Release
=====================================
(2B)+(2B)' ?
RE: Centrifugal Pump Air Release
RE: Centrifugal Pump Air Release
I have to respectfully disagree with this. I believe you are underestimating the ability of water to absorb and transport dissolved air. Especially when you have a flow of water falling through an air gap as you have detailed.
RE: Centrifugal Pump Air Release
The heat exchanger will probably have a drain on it to purge the air.
Your system is pumping upward to a tank that you show as being 40 meters high. Air binding is more of a problem if you are pumping downward, not upward. Design for a velocity of 1 m/s and you will not have to worry about the air. A velocity of 0.8 m/s will clear the air out of a 2-Inch diameter pipe installed at 900 slope.
Air release valves in small pipes may be of little or no value. You do not need any air release valves.
RE: Centrifugal Pump Air Release
This trapped gas venting can be done manually also everytime this pump is started up. An auto release may be justified only if the standby recirc pump is auto started.
Troubleshooting the source of this air accumulation in the standby pump is another topic altogether, from what little we know so far.
RE: Centrifugal Pump Air Release
RE: Centrifugal Pump Air Release
RE: Centrifugal Pump Air Release
RE: Centrifugal Pump Air Release