What is recommended practice for venting the SC in a gas seal design?
What is recommended practice for venting the SC in a gas seal design?
(OP)
I know there is a common problem with nitrogen accumulation, particularly in vertical stand-by pumps with gas seals using nitrogen as the barrier gas. Over time the nitrogen accumulation can lead to liquid displacement from the eye of the impeller and a rough start-up that often requires operators to block in the nitrogen gas supply to the dual gas seal assembly (resulting in premture failure).
Is the recommended mode of venting simply taking a line from the seal chamber back to the suction riser or vapor space in the suction vessel? I know some people choose to simply run a simple plan 13 but how effective is it in ensuring all gas vapors are evacuated from the impeller area? On the line back to the suction riser/vessel, I would think a simple block valve is required and is left open while in standby mode correct?
Is the recommended mode of venting simply taking a line from the seal chamber back to the suction riser or vapor space in the suction vessel? I know some people choose to simply run a simple plan 13 but how effective is it in ensuring all gas vapors are evacuated from the impeller area? On the line back to the suction riser/vessel, I would think a simple block valve is required and is left open while in standby mode correct?





RE: What is recommended practice for venting the SC in a gas seal design?
Vapor space of the suction is optimal, but if you set up a vent line with isolation valve as you described, taken from the seal chamber to a point outside of the suction valve of the pump, you should be fine. As stated, this is more of an issue on in-line vertical pumps, but can occur on horizontally mounted pumps at low flow rates.
RE: What is recommended practice for venting the SC in a gas seal design?
When you say "point outside of the suction valve of the pump", are you suggesting a tie-in point upstream or downstream of the suction valve?
RE: What is recommended practice for venting the SC in a gas seal design?