The current pump mechanical seal in a wide range of products, and as raising the level of product technology and energy conservation requirements, the mechanical seal will be more extensive application prospects. Also known as seal mechanical seal, which has a rotating axis perpendicular to the face, the face in the fluid pressure and external elastic compensation machinery under the influence of co-dependent on secondary seal to keep fit with the other side, and sliding, to prevent fluid leakage. Daqing Petrochemical Plant Bandung property company to use the boiler circulation pump light, model 200LGY75A, flow rate 275 m3 / h, working pressure 0.4MP, working temperature is 95, medium is water, seal mechanical seal pumps, the author of this article actual work, of what the pump sealing problems.

A water pump mechanical seal and the reasons for the leakage phenomenon

Leakage due to pressure generated 1.1
1.1.1 The vacuum caused by the mechanical seal leakage operation
Pump at the start, stop the process, clogging the pump inlet, pumping medium containing gas and other reasons, there may be negative pressure to the sealed chamber, the seal cavity if the negative pressure, can cause seal face friction, will have built-in mechanical seal leak (water) phenomenon, vacuum seal and pressure seal sealing the object is different from the direction of differences, and mechanical seal has its adaptability to a certain direction.
Strategy: The double mechanical seal, which helps improve the lubrication conditions, and improve sealing performance.
1.1.2 pressure and pressure wave caused by the mechanical seal leakage
Since the spring pressure than the pressure and the design is better than too big and seal cavity pressure exceeds 3MPa, makes the seal face pressure ratio is too large, difficult to form film seal face wear serious, more heat, causing thermal deformation of the sealing surface.
Solution: In the mechanical seal assembly, the spring according to the provisions of a certain amount of compression, not allowed to have too large or too small, the phenomenon of mechanical seal under high pressure conditions should be taken. In order to face reasonable force, to minimize the distortion, can be hard alloy, ceramics and other materials with high compressive strength, and to strengthen measures to cool the lubricant, the choice of a reliable transmission mode, such as keys, pins and so on.
1.2 Periodic leakage
1.2.1 The periodic vibration of the rotor. The reason is the stator and the upper and lower end caps or not on the impeller and shaft unbalance, cavitation, or bearing failure (wear), this will shorten the life span and seal the leakage.
Solution: According to maintenance standards to correct the problem.
1.2.2 The axial movement of large pump rotor, the auxiliary shaft seal and the large amount of interference, a flexible ring can not move on the shaft. Flip the pump, dynamic and static ring wear, not compensated displacement.
Solution: In the assembly of mechanical seals, shaft axial movement should be less than 0.1mm, auxiliary shaft seal and the amount of interference should be moderate, while ensuring the radial seal, ring in the shaft after assembly to ensure that mobile and flexible (the ring pressure to spring free to bounce back.)
1.2.3 sealing surface friction caused by lack of lubricant or napping seal faces.
Solution: oil chamber cavity height should be added above the oil dynamic and static ring sealing surface.
1.3. Because of other problems caused by the mechanical seal leakage
1.3.1 Installing the shaft seal ring (or sleeve) and installation of static face seal gland seal ring (or shell) in the end should be chamfered and light repair, so as not to bruise movement ring seal assembly.
1.3.2 a certain amount of compression spring according to the provisions, does not allow too large or too small, the phenomenon of error ¡À 2mm, excessive increase in compression than face pressure, too much friction and heat, causing thermal deformation of the sealing surface and accelerated wear face , the small amount of static and dynamic compression ring less than the pressure face, you can not seal.