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In Piping Plan 23 there is recirculation from a circulation device in the seal chamber through a cooler and back into the into the seal chamber.
NOTE: In Piping Plan 23, product in the seal chamber is isolated from that in the impeller area of the pump by a throat bushing. The seal is equipped with an internal circulating device that circulates seal chamber fluid through a cooler and back to the seal chamber. To maximize circulation, the piping losses should be minimized through the proper selection of pipe size, elimination of fittings, use of large radius bends, and reduction in the length of piping runs.
In Piping Plan 23, the cooler cools only that fluid in which the seal operates, and this cool fluid does not enter the process. This results in high energy efficiency. Lessening the duty is very desirable because it extends the life of the cooler. The industry has considerable negative experience with Piping Plan 21 and Piping Plan 22 because of cooler plugging.
Piping Plan 23 is the plan of choice for all hot water services. Particularly boiler feed water, and many hy-drocarbon services. This plan is the standard selection for hot water at 80 °C (180 °F) and above, and boiler feed water. Hot water has very low lubricity above 80 °C (180 °F), resulting in high seal face wear.
This plan is also desirable in many hydrocarbon and chemical services where it is necessary to cool the fluid to establish the required margin between fluid vapor pressure (at the seal chamber temperature) and seal chamber pressure. In a Piping Plan 23, the cooler only removes seal face-generated heat plus heat soak from the process. This duty is usually much less severe than that in Piping Plan 21 or Piping Plan 22.
Effective flow of the Piping Plan 23 system is only achieved with proper exclusion of all gas and air bubbles from the seal cooler and piping. Venting of the system during commissioning is critical to proper operation.
High-freezing-point and viscous products should be considered when selecting a Piping Plan 23 flush system. The cooler might cool the fluid below the point of circulation. In these applications, consider using steam as a cooling medium, or utilize a Piping Plan 21 system. Vent line should be connected to drain or recovery system to prevent exposing the operator to process during venting.
A distributed flush injection is not recommended with a Piping Plan 23.
Malavazi NOTE: It is recommended to install the vent, at a high point to the heat exchanger, and the clearance between the shaft and throat restriction bushing reduced, to avoid the reflux of hot to cold liquid.
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.