API Plan 13


Product recirculation from seal chamber to pump suction via a flow control orifice.


1. Provides continuous vent for vertical pumps.


1. Wherever Plan 11 is not usable due to low-pressure margin between discharge and seal chamber pressure.

2. Used in vertical pumps.


1. Check margin between seal chamber pressure and suction pressure.

2. Orifice size should be at least 1/8” (3.2mm).



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