API Plan 11


Product recirculation from pump discharge to seal through a flow control orifice.


1. Prevents product from vaporizing by maintaining positive pressure above vapour pressure.

2. Becomes a self-venting plan for horizontal pumps.

3. Default API Plan for most single seals.


1. In general, applications with clean non-polymerizing fluids with moderate temperatures.


1. Calculation of recirculation flow rate, heat removal and orifice size are required.

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

3. Check the margin between discharge pressure and seal chamber pressure to ensure proper flow of fluid.

4. Do not use with media containing solids and abrasives.



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