The cause of the problem caused by the leakage of the mechanical seal of the pump? -

The cause of the problem caused by the leakage of the mechanical seal of the pump?

　2016-11-23　　

　　Mechanical seals are currently widely used in pump products. With the improvement of product technology and energy-saving requirements, the application prospect of pump mechanical seals will be more extensive. Pump mechanical seal or seal, which has a pair of faces perpendicular to the axis of rotation, the pressure of the fluid under the action of elastic force and the mechanical seal outside the compensation mechanism, have the dependence on the other end of the auxiliary seal and maintain health, and relative sliding, thus Prevent fluid leakage. This article will discuss mechanical seals for pumps.

　　1 pump mechanical seal leakage phenomenon and cause

　　1.1 Pressure will cause the pump mechanical seal to leak

　　 Because 1.1.1 the mechanical seal of the vacuum state operation leaks

　　During the start-up process, the pump is stopped. The reason for the blockage of the pump inlet, such as the pumped air containing medium, can make the mechanical seal cavity negative pressure. If the seal cavity negative pressure, it will cause dry friction on the sealing surface, and the built-in mechanical seal The leakage of the structure will cause the phenomenon of (water). Different vacuum seals and positive pressure seals are the object's poor orientation and sealing. Mechanical seals have a certain directionality.

　　Countermeasure: Adopt double end face mechanical seal, which helps to improve lubrication conditions and improve sealing performance.

　　1.1.2 High pressure and pressure wave caused by the leakage of the mechanical seal of the pump

　　 Because the design of the spring pressure and the total pressure ratio is too large and the seal cavity pressure exceeds 3MPa, it will cause the end surface specific pressure of the pump mechanical seal to be too large, and it is difficult to form a sealing film, wear, and heat increase, which is caused by the thermal deformation of the sealing surface.

　　 Countermeasures: When assembling the mechanical seal, the spring compression must be in accordance with the regulations. Excessive or too small phenomena are not allowed. The measures should be taken under the conditions of high-pressure mechanical seals. In order to make the surface stress reasonable and minimize the deformation, high-strength materials such as cemented carbide and ceramic can be used, and the cooling and lubrication measures should be strengthened, and the selection of reliable transmission methods, such as keys, pins, etc.

　　1.2 Periodic mechanical seal leakage

　　 1.2.1 Periodic vibration of the rotor. The reason is that the stator and the lower end cover are absent or imbalanced in the impeller and main shaft, cavitation or bearing damage (wear), which will shorten the life of mechanical seal leakage.

　　Countermeasures: Solve the problem of periodic mechanical seal leakage according to maintenance standards.

　　1.2.2 The axial momentum of the pump rotor interferes with the number of auxiliary mechanical seals and the shaft, and the moving ring cannot move flexibly on the shaft. In the pump reverse, dynamic, static ring wear, there is no compensation displacement.

　　Countermeasures: In the mechanical seal device, the axial momentum shaft should be less than 0.1mm, and the mechanical seal and the shaft amount for the auxiliary pump should be moderate. While ensuring the radial seal, ensure that the shaft can be moved flexibly in the moving ring assembly (dynamic The ring can bounce freely against the spring).

　　Insufficient amount of lubricating oil on the surface is caused by dry friction or mechanical seal design for brush-sealed end pumps.

　　Countermeasure: The height of the lubricating oil surface of the oil chamber cavity should be added to the above dynamic and static ring sealing surfaces.

　　1.3. Other problems caused by the leakage of the mechanical seal of the pump

　　1.3.1 Ring installation The shaft (or sleeve) end of the mechanical seal for the pump and the end surface of the installation (or housing) of the static ring seal gland sealing ring should be chamfered, and the assembly is to avoid scratching the sealing ring.

　　1.3.2 The spring compression must be in accordance with the regulations. Too large or too small is not allowed. The error is 2mm. Excessive compression increases the specific pressure of the end face, excessive frictional heat, and surface wear causes thermal deformation and acceleration of the sealing surface. , If the compression is too small, the specific pressure of the static ring's end face is insufficient, and it can be sealed.　　6.html,

There are three main reasons for the failure of the sealing function of mechanical seals. 　　 Which equipment uses mechanical seals?