re: Pump Gas-locking
re: Pump Gas-locking
(OP)
Hi there,
I am gathering info to understand the issues of gas-locking in a pump. What cause gas-locking, typical scenario of a gas-locking in a plant application, methods to prevent and mitigation etc.
Thanks
I am gathering info to understand the issues of gas-locking in a pump. What cause gas-locking, typical scenario of a gas-locking in a plant application, methods to prevent and mitigation etc.
Thanks





RE: re: Pump Gas-locking
Some common things are not having enough NPSH, as pumps wear, they can require more than the original design.
Piping on the suction to small (NPSH again) due to more volume than originally design.
On PD pumps, bad valves can contribute.
Piping on the inlet has pockets.
The minimum flow bypass valve causing flashing.
There are loads more.
RE: re: Pump Gas-locking
Air entering thru' the shaft seal.
Phitsanulok
Thailand
RE: re: Pump Gas-locking
The scenario is: Two cooling vertical centrifugal pumps running during a maintenance condition with the suction coming from water tanks or headers with hugh surface area. The pump bypass valves are also partially open. System fluid is heavy water (D20). When during maintenance on some plant equipment, these headers are drained to low level. One pipe is connected on the side of the tank at about 1/3 of the tank. The pipe is open atmospheric during maintenance. Normally, the submergence level is higher than 1/3 so that no air entrapment. However, system disturbances may cause the water level to fluctuate into the low level below the open pipe connection.
To what extent of air entrapment will cause the gas-locking of the pump? I am thinking that if one cooling pump tripped, it may cause the water level to drop temporarily to the extent that gas-lock of another pump.
RE: re: Pump Gas-locking
If everything is just right, the water level is 1/8" over the tank nozzel, I've seen where: when the pump starts, the level drops in a vortex and you suck in enough air to lock the pump. That might be something to look at. A vortex breaker may help.
RE: re: Pump Gas-locking