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In Piping Plan 31 there is recirculation from a high-pressure region of the pump (typically the pump discharge or the pump discharge piping) through a cyclone separator delivering the clean fluid to the seal chamber. The solids are delivered to the pump suction line.
Piping Plan 31 is specified only for services containing solids with a specific gravity at least twice that of the process fluid. A typical use of this plan is water service to remove sand or pipe slag. In Piping Plan 31, product is routed from the discharge of the pump into a cyclone separator. Solid particles are centrifuged from the stream and routed back to suction. The seal flush is routed from the cyclone separator into the flush connection on the seal gland plate. If the process stream is very dirty or is a slurry, Piping Plan 31 typically is inadequate and is not recommended. The use of a pump throat bushing is recommended when a Piping Plan 31 is specified.
Cyclone separators are not generally recommended for process fluids that contain gases.
Field experience has shown that abrasive wear on the inside of the cyclone may result in reduced reliability.
This plan has not proven to consistently achieve a three-year (3-yr) operating life.
Malavazi NOTE: For this process, it is important to evaluate the pressure differential between discharge and suction, in order to obtain the best performance of the separator at least 1.5 Kgf/cm².
For liquids with crystallization characteristics, Quench is recommended due to micro leakage on the faces, otherwise plug the injection connection leaving the drain free to prevent environmental disasters, since the floating ring will act as a safety point.