Functions of the mechanical seal auxiliary system for centrifugal pumps

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The mechanical seal assembly of a centrifugal pump generally consists of: the primary seal, the secondary seal, and the auxiliary system. The primary seal serves to seal the working medium within the pipeline, while the secondary seal provides supplementary sealing support to the primary seal. The auxiliary system is primarily intended to create a favorable environment around the primary and secondary seals and to ensure that the primary seal operates under optimal conditions. Guangyi Water Pumps has learned that the mechanical seal auxiliary system can control and improve the sealing conditions in three aspects: temperature control function, fluid replacement (blocking/buffering) function, and impurity removal function. 1. Temperature control: The main function of the mechanical seal auxiliary system is temperature control, with common methods including flushing, cooling, back cooling, and circulation. Flushing is the most effective method for controlling temperature and extending the lifespan of mechanical seals. Flushing can remove the heat generated by the system, effectively lowering the temperature of the shaft seal box, preventing the vaporization of the liquid film, improving lubrication conditions, and preventing the accumulation of impurities and the formation of air pockets. Flushing can be classified according to the source of the flushing fluid: self (internal) flushing and external flushing. 2. Fluid substitution (blocking/buffering): Under certain specific operating conditions, single-face seals are not sufficient to meet the sealing requirements in actual production. In such cases, a dual-seal system with or without pressure is necessary, and a blocking/buffering fluid is used to replace the medium that is to be sealed, especially in the following situations: (1) Media that are toxic or explosive ； (2) Highly corrosive media ； (3) Media with poor lubricity or no lubricity, etc. 3. Removal of impurities: During the daily operation of oil fields, the fluid pumped through pipelines using centrifugal pumps often contains various impurities such as dirt, crystals, and solid particles. These impurities accelerate the wear and damage of seals, so it is necessary to take measures to eliminate them. (1) Before the sealing medium enters the sealing chamber, a filter is used to remove solid impurities. Filters are used in situations where the impurity concentration is low (less than 2%); otherwise, the filters need to be cleaned and regenerated frequently, with a particle size of generally 10–50 um. (2) The external flushing method is employed to prevent solid impurities from penetrating the sealing surface. This method is recommended when the impurity content in the medium is high and the temperature is high. (3) Adjusting the temperature to prevent crystallization is a suitable method for sealing certain solvent pumps.