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In industries such as petroleum refining and chemical industry, more than 80% of the rotating equipment for conveying liquid media adopt mechanical seals. The zero escape, high reliability, long life, and low wear of mechanical seals are the research and development directions in the field of mechanical seals. A well-working mechanical seal auxiliary system is a necessary condition to ensure the long life of the mechanical seal. The auxiliary system scheme stipulated in API682 can basically meet the normal operation of mechanical seals under most working conditions.Among the auxiliary system schemes specified in API682, schemes No. 23 and No. 52/53 (as shown in the figure below), require sealing protection or isolation buffer to be able to circulate to take away the heat generated by the sealing end faces of mechanical seals and reduce the sealing working temperature.
There are three ways to promote the circulation of sealing fluid: (1) Add a small pipeline circulation pump to the system pipeline to complete the circulation; (2) Use thermosiphon effect to form natural flow circulation; (3) A rotating part with a pumping effect —— a pumping ring, is added to the seal to complete the circulation of the sealing fluid. For the circulation method (1), the additional small circulation pump involves a series of problems such as pressure resistance, temperature resistance, sealing, explosion-proof, etc., and the cost investment is relatively large, so it is rarely used in general
For the (2) circulation mode, a certain temperature difference is required to form a circulation, and the circulation speed is relatively slow, and the effect is not obvious when it is used in the occasions with high speed and high heat generation. It is generally used in occasions with low speed and low heat generation
(3) circulation mode—pumping ring, which is fixed on the rotating part of the mechanical seal and rotates together. The function of the pumping ring is to transfer the buffer liquid in the seal chamber (isolation liquid or self-flushing fluid in the pump chamber) and sent back to the pipeline after passing through the cooler storage tank to meet the requirements of sealing liquid circulation. Compared with the mechanical seal device itself, the cost is very low. Except for very little consumed shaft power, it does not involve other problems. It is economical and practical. So it is widely used in mechanical sealing.
