(1) The leakage of mechanical seal caused by high pressure and pressure wave, when the design of spring specific pressure and total specific pressure is too large and the pressure in the seal cavity exceeds 3Mpa, which will make the specific pressure of the seal end face too large, the liquid film is difficult to form, the seal end face will be severely worn and the heat generation will increase, resulting in the thermal deformation of the seal face.
Countermeasures: when assembling the mechanical seal, the spring compression must be carried out according to the regulations and it is not allowed to be too large or too small. Measures should be taken for the mechanical seal under high pressure. In order to make the stress on the end face reasonable and reduce the deformation as much as possible, cemented carbide, ceramics and other materials with high compressive strength can be used and the lubrication measures of cooling can be strengthened.
(2) In the process of starting and stopping the mechanical seal leakage pump caused by vacuum operation, due to the blockage of the pump inlet and the gas contained in the pumped medium, it is possible to cause negative pressure in the seal cavity. If the seal cavity is negative pressure, it will cause dry friction on the seal end face, and the built-in mechanical seal will produce air (water) leakage. The difference between the vacuum seal and the positive pressure seal is that the directions of the object sealed are different, the mechanical seal also has its adaptability in a certain direction.
Countermeasures: double face mechanical seal is adopted, which helps to improve lubrication conditions and sealing performance.
According to JB/T4127.3-1999 Technical Conditions for Acceptance of Mechanical Seal Products, the service life of medium mechanical seal is one year, and the service life of corrosion-resistant mechanical seal is six months. "if the working conditions are harsh, such as high temperature, high pressure, high speed, high viscosity liquid, special highly corrosive medium or particle medium and if it is frequently operated or stopped, the service life and average leakage of products should be agreed by the user and the manufacturer ", and the mechanical seal storage after acceptance should be clearly required: "it shall be stored in a ventilated and dark room no less than -15 and no more than 40, with a storage period of 1 year ".