Leakage Prevention of Leakage of Pump Mechanical Seals and Countermeasures

Mechanical seal, also known as the end seal, which has a pair of perpendicular to the axis of rotation of the end surface, the end of the fluid pressure and compensate mechanical external elastic force, rely on the auxiliary seal with the other end to maintain fit and slide relative to prevent Fluid leaks.

First, the common cyclical leakage

1, the axial displacement of the pump rotor large, secondary seal and shaft interference large, flexible ring can not move on the axis. In the pump flip, moving, static ring wear, not to compensate for displacement.

Countermeasures: When assembling the mechanical seal, the axial displacement of the shaft should be less than 0.1 mm, the interference between the auxiliary seal and the shaft should be moderate, and the radial seal should be ensured at the same time that the movable ring can be flexibly moved on the shaft after assembling Moving ring pressure spring can bounce back freely)

2, the sealing surface of the lack of oil caused by dry friction or hair sealing surface

Strategy: Oil chamber oil surface height should be higher than the dynamic and static seal surface

3, the periodic vibration of the rotor, because the stator and the upper and lower end cover is not in the impeller or spindle imbalance, cavitation or bearing damage

Second, leakage due to pressure

1, high pressure and pressure wave caused by mechanical seal leakage

As the spring than the pressure and the total pressure than the design is too large, the pressure within the sealed chamber exceeds 3Mpa, will make the seal end surface pressure is too large, difficult to form the liquid film, seal face serious wear and tear, increased heat, causing the sealing surface thermal deformation.

Countermeasures: mechanical seal assembly, the amount of compression spring must be carried out according to regulations, not allowed to be too large or too small. Mechanical seals under high pressure conditions should take measures to force the end face is reasonable, you can use hard alloy, ceramic and other materials with high compressive strength and enhance cooling lubrication measures.

2, the vacuum state of the mechanical seal caused by leakage

Pump in the starting and stopping process, due to blockage of the pump inlet, pumping medium containing gas and other reasons, there may be negative pressure in the sealed chamber, and then cause the sealing surface dry friction.

Countermeasures: The use of double-sided mechanical seal, which will help improve the lubrication conditions, improve the sealing performance.

Third, due to leakage caused by the media

Medium particles, impurities into the sealing surface, the seal failure; dynamic and static seal secondary seal medium weak acid, weak base corrosion, loss of function.

Countermeasures: To ensure the cleanliness of the bottom cover, oil chamber, clean the oil assembly is forbidden; mechanical seal oil surface oil line should be higher than the sealing surface; according to different media use different structures of the mechanical seal, such as corrosive media , Rubber parts should be used high temperature resistant, weak acid, weak base of fluorine rubber, easy access to the solid particles in the position of tungsten carbide on the choice of mechanical friction pair of mechanical seals.

Fourth, due to other problems caused by mechanical seal leakage

There are mechanical seal design, selection, installation and other unreasonable place

Countermeasures: Spring compression error should be between -2 mm -2 mm, too large increase the pressure on the end face, friction heat too much, easily lead to sealing surface thermal deformation and accelerated wear on the face, too small then the dynamic and static end face ratio Pressure is not enough, can not be sealed; seal ring seal installed gland (or shell) end surface should be chamfered and light, so as not to bump in the assembly dynamic and static ring seals.

The above summarizes the more common causes of mechanical seal leakage and countermeasures. Mechanical seal itself is a demanding precision parts. In use, should analyze a variety of factors, the mechanical seal suitable for a variety of pump technical requirements and the use of media requirements, so as to ensure long-term reliable operation.

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