A common periodic leakage
1. axial movement of the pump rotor volume, auxiliary shaft seal interference with the large, flexible ring can not move in the axis. Flip the pump, the dynamic and static ring wear, without compensation displacement.
Strategy: In the assembly of the mechanical seal, the axial runout should be less than 0.1 mm, auxiliary shaft seal and the moderate amount of interference, while ensuring the radial seal, ring after assembly to ensure flexibility in the shaft movement ( the pressure ring are free to bounce back to the spring)
2. sealing surface friction caused by insufficient lubrication or napping seal faces
Countermeasures: oil lubricant oil chamber height should be higher than the dynamic and static sealing surface ring
3. periodic vibration of the rotor, because the stator and the upper and lower end caps or not on the impeller and shaft unbalance, cavitation, or bearing damage
Second, due to the leakage of stress
1. high pressure and pressure wave caused by the mechanical seal leakage
As the spring pressure than the pressure and is better than the design is too large, sealed chamber when the pressure exceeds 3Mpa, will seal faces pressure ratio is too large, difficult to form film, seal faces serious wear, the heat is increased, resulting in thermal deformation of the sealing surface.
Strategy: In the mechanical seal assembly, the spring compression according to the provisions must not allow too large or too small. Under high pressure mechanical seals should take measures, in order to face reasonable force can be used cemented carbide, ceramics and other materials with high compressive strength, and enhance the lubrication cooling measures.
2. run the vacuum caused by the mechanical seal leakage
Pump starting and stopping the process, because blocking the pump inlet, pumping medium containing gas and other reasons, there may appear negative pressure sealed chamber, thereby causing the sealing surface friction.
Strategy: double mechanical seal, which helps to improve the lubrication conditions, improve sealing performance.
Third, due to leakage caused by media
Medium particles, impurities into the sealing surface to seal failure; dynamic and static secondary seal ring by the media as weak acid, weak base erosion, loss of proper function.
Strategy: to ensure cover in the oil room cleanliness, unclean oil prohibit assembly; mechanical seal cavity oil line should be higher than seal oil surface area; selected according to different media with different mechanical seal structure, such as the corrosive medium , rubber parts should be selected high temperature resistance, weak acid, weak base of fluorine rubber, the solid particles used easily accessible location on the tungsten carbide tungsten carbide mechanical seal friction pairs.
Fourth, because of other problems caused by mechanical seal leakage
Mechanical seal in design, selection, installation, unreasonable
Strategy: Spring compression error should be -2 mm -2 mm, too large an increase of end-specific pressure, friction and heat too much, could easily lead to heat distortion and speed up the sealing surface face wear, is too small the static and dynamic than the ring face enough pressure can not be sealed; installation ring sealing gland ring (or shell) in the end should be chamfered and repair of light, to avoid bumps assembly static and dynamic ring seal.
Above summarizes the more common mechanical seal leakage and the countermeasures. Mechanical seal itself is a demanding precision parts. In use, a variety of factors should be analyzed so that the pump mechanical seal suitable for all kinds of technical requirements and use of media requests, so as to ensure the long-term reliable operation.
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