Several Cooling Methods of Mechanical Seals

A mechanical seal is a shaft sealing device for rotating machinery. Such as centrifugal pumps, centrifuges, reactors and compressors and other equipment. Since the transmission shaft runs through the inside and outside of the equipment, there is a circumferential gap between the shaft and the equipment, and the medium in the equipment leaks out through the gap. If the pressure in the equipment is lower than the atmospheric pressure, the air leaks into the equipment, so there must be a shaft seal to prevent leakage. There are many types of shaft seals. Because mechanical seals have the advantages of less leakage and long service life, mechanical seals are the most important shaft sealing methods in these equipment in the world.

1. Mechanical seal flushing cooling

Mechanical seal for pumps are usually flush-cooled. The inlet of the flushing fluid is aimed directly at the friction surface. The purpose of flushing is to keep the temperature of the friction surface within a certain range and to prevent the accumulation of impurities near the sealing face. This is a commonly used cooling method, which can be divided into self-flushing and external flushing.

The self-flushing uses the sealed medium as the flushing liquid, which can be applied to the general mechanical seals for pumps. A small part of the liquid is drawn from the pump outlet, directly flushes the friction end face, and then flows into the pump cavity. When conveying high temperature or medium with particles, a cooler or filter can be added to the pipeline between the pump outlet and the flushing inlet.

External flushing is a separate flushing fluid system for flushing and cooling. It is mostly used to seal high temperature or particle-containing media, but its structure is more complicated.

2. Mechanical seal static ring back cooling

The cooling method of mechanical seal for pump is to send the cooling medium (such as water) directly to the friction end face that needs to be cooled through the back of the static ring, and the cooling medium and the working medium are not mixed. This cooling method has a simple structure, good effect, and its applicable temperature range is also wide. But its disadvantage is that the hardness of cooling water is required to be low, especially the sealing of high temperature medium. Because the hardness of the water is high, scale will be generated on the shaft near the end face of the seal and the seal will fail. At the same time, it is necessary to prevent the cooling water from leaking out along the extension end of the shaft.

3. Cooling of the outer periphery of the static ring of the mechanical seal

In order to solve the scale problem, the mechanical seal for pump adopts the method of cooling the outer circumference of the static ring. This method avoids the generation of scale on the shaft or the shaft sleeve because the cooling water does not directly contact the shaft or the shaft sleeve, and also prevents the water from running along the shaft. If it leaks to the atmosphere side, the requirements for the quality of cooling water can be reduced, but its cooling effect is not as good as the cooling of the back of the static ring.