Mechanical seal cooling and flushing method is an indispensable operating point in the process of product use, but many users know this operation, but do not understand the specific operating points, so the following is a detailed introduction to it.
Due to the friction of the end face will produce a lot of friction heat, which will increase the temperature of the friction secondary ring. At the same time, if the temperature of the sealing medium itself is high, it will make the end face of the friction pair always operate at a very high temperature, in this case, if the flushing cooling measures are not taken, it will make:
(1) Dry friction due to evaporation of liquid film between end faces;
(2) Auxiliary seals made of rubber and plastic materials will age, crack and even fail;
(3) Accelerate the corrosion of the sealing medium on the sealing parts;
(4) dynamic and static ring deformation;
(5) increased end wear;
(6) serious end leakage.
From this point of view, the use of washing oil and cooling water for seals is to reduce the temperature of friction, ensure that there is a complete liquid film between the friction surface, reduce friction loss, reduce power consumption, and ensure that the liquid film is not destroyed by high temperature vaporization. Therefore, the flushing and cooling measures of the seals are essential to ensure that the seals have good sealing performance and long service life.
Common mechanical seal flushing, cooling see below
Direct injection of liquid into the high-pressure side of the double or single face seal is called "flushing". General pumps should be flushed, especially light hydrocarbon pumps. The purpose of flushing is to seal, cool and lubricate:
(1) The sealing cavity is sealed with a liquid external circulation compatible with the medium), so as to prevent high temperature, toxic and valuable media from leaking out of the pump shaft; Prevent the medium containing solid particles from leaking into the sealing cavity and wearing the sealing surface; Prevent the medium that is easy to vaporize and freeze, such as liquefied gas, from leaking into the sealing cavity to produce gas, causing thousands of friction and wear the sealing surface; Prevent the medium that is easy to crystallize from leaking into the sealing cavity, and wear the sealing surface due to the formation of crystallization by cooling; Under negative pressure, prevent air and flushing fluid from leaking into the pump.
(2) cooling to prevent high temperature media from entering the sealed cavity; Frictional heat generated when the guide ring and the static ring work.
(3) Lubrication There is a layer of liquid film between the sealing surface to lubricate.
1. Self-washing
Features: With the sealed medium as the flushing liquid, a small part of the liquid is drawn from the pump outlet side, injected directly into the high-pressure side of the seal end face, washed, and then flowed into the pump chamber.
Application: The pressure in the sealing chamber is less than the pump outlet pressure, greater than the pump inlet pressure, the medium temperature is not high temperature ≤80C), without impurities.
2. External rinse
Features: Another flushing solution is used, and the flushing solution should be:
(1) Clean, non-corrosive without solid particles, low temperature (usually 40"C).
(2) It has a certain lubricity and does not affect the quality of process products.
(3) It is not easy to produce vaporization under operating conditions.
Use: It is used for the occasions where the temperature of the sealed medium is high, it is easy to vaporize and the impurity content is high. The pressure of the liquid is 0.1~ 0.2MPa higher than the pressure of the medium in the sealed chamber.
3, circulation rinse
Features: By means of the impeller in the sealing cavity, the liquid in the sealing ring is circulated. The heat taken away is the heat generated by the mechanical seal, and the cooling water consumption is less than that of the self-washing.
Application: Because the impeller head in the pump is small, it is suitable for the occasions where the pressure difference between the inlet and outlet of the pump is small.