What are the effects of overheating when using a mechanical seal?

According to different working conditions and medium properties, mechanical seals include high and low temperature resistant mechanical seals, high pressure corrosion resistant mechanical seals, particle medium resistant mechanical seals and mechanical seals suitable for easily vaporized light hydrocarbon media, etc. Mechanical seals of different structure types and materials should be selected according to different uses.

A gap appears on one or both end faces, indicating that the distance between the two end faces is too large, and a gap occurs when the two end faces are tightly closed. A common cause of end face separation is the rapid evaporation of the imported mechanical seal medium. For example, water, especially in hot water systems or liquids containing condensed water, expands as it evaporates, separating the two ends. Cavitation of the pump and blockage of the seal can also be the cause of the seal face clearance. In this case, vibration and coupling misalignment are not the cause, as it is not enough to notch the end face. Reducing the end face temperature is a common method to prevent the end face from being damaged by the rapid evaporation of the medium. At the same time, it is also beneficial to use materials with good thermal conductivity, such as nickel-based cemented carbide, copper-impregnated graphite, etc. In addition, use a balanced mechanical seal, or use a special corrosion-resistant mechanical seal gland to inject liquid from the outside for cooling, or directly cool the seal in the cavity, etc. It is very effective in reducing the temperature of the sealing end face.

When the mechanical seal fails, the end face of the friction pair often leaves small radial cracks, or radial cracks with blisters or even cracks. This is caused by overheating of the seal, especially ceramic and cemented carbide seal faces are susceptible to this damage. Poor medium lubricity, overload, high working temperature, high linear speed, improper combination of paired materials, etc. The superposition of any one or several of these factors can generate excessive frictional heat. If the frictional heat is not released in time, thermal cracks will occur in the dyeing and finishing mechanical seals, resulting in excessive wear and high leakage. In order to solve the problem of overheating of the seal, in addition to changing the face area and reducing the load, it can also be solved by using a static seal and adding a guide bush to force the cooling of the circulating fluid to guide the sealing face, or opening a hydrodynamic groove on the sealing face. Numerous tiny hot spots and isolated areas of discoloration on the rubbing end face indicate that the seal has deformed under the influence of high pressure and high temperature. For the thermal deformation of the end face, the general calculation method is not allowed, and the finite element method should be used for calculation to improve the design of the sealing ring.