Mechanical seal for kettle There are three main reasons for the sealing function failure of

(1) Sealing surface open

When repairing mechanical seals, 85% of seal failures are not caused by wear, but have leaked before wear.

As soon as the sealing surface is opened, solid particles in the medium enter the sealing surface under the action of liquid pressure. After the sealing surface is closed, these solid particles are embedded on the surface of the soft ring (usually the right ink ring), which is actually a "grinding wheel" that will damage the surface of the hard ring.

Since the moving ring or rubber ring is fastened on the shaft (shaft sleeve), when the shaft is in series, the moving ring cannot fit in time, which causes the sealing surface to open and the sealing surface to close behind time, so that solid particles enter the sealing surface.

At the same time, there are also solid particles between the shaft (sleeve) and the sliding parts, which affect the sliding of the rubber ring or dynamic ring (relative dynamic sealing point, common fault). In addition, the medium will also produce crystals at the friction part between the rubber ring and the shaft (shaft sleeve), and there will also be solid substances at the spring, which will open the sealing surface. Mechanical seal

(2) Overheating

Since heat will be generated on the sealing surface, the operating temperature of the rubber ring shall be lower than the design specification. The service temperature of fluororubber and polytetrafluoroethylene is 216 ℃, and the service temperature of nitrile rubber is 162 ℃. Although they can withstand higher temperatures, the rubber ring is in danger of continuing vulcanization due to the high heat generated by the sealing surface, and eventually loses its elasticity and leaks. (Cold brittleness is considered in cold zone)

Heat will also cause crystallization of the medium between the sealing surfaces, such as carbon deposition, which will cause the sliding parts to be stuck and the sealing surface to be condensed. Moreover, some polymers become coking due to overheating, and some fluids lose lubrication due to overheating, and even flash.

Overheating can not only change the condition of the medium, but also aggravate its corrosion rate. For deformation of metal parts, cracking of alloy surface, and some coating cracks, balanced mechanical seal shall be selected for design to reduce specific pressure and prevent overheating.