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In Piping Plan 11 there is recirculation from a high-pressure region of the pump (typically the pump discharge or the pump discharge piping) through a flow control orifice to the seal.
With purchaser approval, the flow control orifice may be omitted if it is not needed to achieve the required flush flow rate.
Piping Plan 11 is the default seal flush plan for all Arrangement 1 and 2 seals. In Piping Plan 11, product is routed from the pump discharge to the seal chamber to provide cooling for the seal and to vent air or va- pors from the seal chamber. Fluid then flows from the seal chamber back into the process stream. It is the most commonly used flush plan for clean general service equipment. For high-head applications, careful consideration should be given to calculation of the required flush flow rate. Calculations are required to determine the proper orifice and throat bushing dimensions to assure adequate seal flush flow. In pumps with low differential head or pumping high-viscosity fluids, the required flow rate for the piping plan may be achieved without the flow control orifice. Care shall be taken when using this plan with polymerizing fluid that may plug the orifice and connecting piping.
Malavazi NOTE: For liquids with crystallization characteristics, Quench is recommended due to micro leakage on the faces, otherwise plug the injection connection (flush inlet) leaving the drain free to prevent environmental disasters, since the floating ring will act as a safety point.