API Plan 23 is one of the seal piping flush plans detailed in the API 682 standards. The plan effectively changes the environment in which the seal operates. An analogy of how the plan works can be made with a greenhouse or glass house. A greenhouse creates a micro climate that will enable delicate plants to thrive in a cosseted environment regardless of the harsh, cold conditions that would exist in the outside world. Tropical species can be grown in high northern latitudes where they would have no chance of existence. In a centrifugal pump, Plan 23 uses a throat bushing to effectively isolate the seal chamber from the pump media. The small volume of liquid in the seal chamber is circulated through a local cooler or heat exchanger. Mechanical seals are potentially fragile components and their reliability significantly reflects the life of a pump asset. By placing the mechanical seal in its own micro climate and maintaining the temperatures in this area to temperatures where a seal can comfortably exist, extended life and reliable service are possible even on some of the most hostile high temperature duties.
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