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Self-venting pump

Self-venting pump

Self-venting pump

Can anyone please give specific configuration of a centrifugal pump that is self-venting?
API 610 states that all pumps shall be provided with vent and drain connections, except that vent connections may be ommitted if the pump is made self-venting by the arrangement of the nozzles.
What kind of nozzle arrangement is it exactly?Can a overhung end-top nozzle pump with discharge nozzle through pump casing centerline like the ones in ASME B73.1 be self-venting?

Thank you for your help.

RE: Self-venting pump

Self-venting pump - a pump whose casing can be flushed of entrained gas by simply opening its suction and discharge control valves and rotating the shaft manually prior to starting. The pump casing does not have a vent connection. In a multistage pump, only the first stage volute needs to be self-venting.

API Standard 610 considers a pump to be self-venting "if the nozzle arrangement and casing configuration permit adequate venting of gases from the first-stage impeller and volute area to prevent loss of prime during the starting sequence."


RE: Self-venting pump


Sometimes venting is more important in some cases,
API 610 11 says: All pumps shall be provided with vent and drain connections, except that vent connections may be
omitted if the pump is made self-venting by the arrangement of the nozzles. Pumps that are not self-venting shall
be provided with vent connections in the pressure casing, as required (see 6.8.10).

So there is no mandatory to be selfventing in API610 11 edition.
Talking about OH2 pump type, Selfventing will have vertical centerline top discharge nozzle.
Non-Selfventing will have vertical tangential discharge nozzle.

I hope this helps.


RE: Self-venting pump

Thank you PumpSmart,

With the little brain that I have, my understanding is that in-line pumps like OH3 & OH6 will be not self-venting. Am I correct?

Knowing that the pump is OH2 type, should it mean that we specify vent connections in the data sheet especially during FEED engineering even if we do not know yet the orientation of the discharge nozzle if it is centerline or tangential?


RE: Self-venting pump

Add a paragraph in your specification: all pump shall be supplied with separate vent connections unless pump is self venting due to the arrangement of nozzles.

RE: Self-venting pump

Pump manufacturers know well if the type of pump needs venting or not.The purchaser will only need to specify type of vent / drain connection is preferred such as simple threaded plugs or flanged and valved connections.

RE: Self-venting pump


Thanks for your help. I agree with you.

RE: Self-venting pump

You are right, in in-line vertical pumps, it is mandatory to vent the pump, to be clear, to vent seal chamber for preventing air burble formation on mechanical seal faces that could damage them.
Some API Plans , like 14 in my expecience in in-line vertical pumps, help to do that in addition to lubricate and refrigerate seal faces.

I hope this helps.

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