How is flushing——the most important auxiliary facility of mechanical seal ——carried out

Auxiliary facilities for mechanical seals refer to lubricating, cooling or temperature-regulating, flushing, purifying, diluting and flushing away the leakage medium to improve the working environment of the mechanical seal by means of flushing, cooling, filtering and separation.

The primary mode of operation of all ancillary facilities of the mechanical seals is flushing. There are two ways for the flushing fluid to enter the seal chamber: single-point flushing and multi-point flushing. Single-point flushing: the flushing liquid is flushed from one outlet, and can be divided into three types: radial, axial and tangential.

Radial flushing: the sealing fluid flushes the friction pair of the mechanical seal vertically along the radial direction, with a simple structure, and is a method that is widely used. However, the amount of flushing should not be too large to prevent the graphite ring from being flushed out of the gap.Axial flushing: the sealing fluid enters the sealing cavity along the axial direction, avoiding the erosion of the graphite ring, and can be used in pumps with corrosive media. Tangential flushing:Tangential flushing: The flushing fluid flushes the friction pair of the mechanical seal along the tangential direction, which is a better way in single-point flushing.

The structure of single-point flushing is simple, but the temperature distribution around the mechanical seal is uneven. In order to avoid eroding the graphite ring of the mechanical seal, the flow rate of the radial flushing liquid flowing into the sealing chamber  of the mechanical seal should not be higher than 3m/s, and the diameter of the flushing hole should not be less than 5mrn. For this reason, the amount of flushing must be controlled. Tangential flushing makes the temperature of the circumference of the sealing surface tend to be uniform, and also reduces the erosion of the graphite ring  of the mechanical seal, which is a recommended method.

Multi-point flushing: The flushing liquid enters the sealed cavity of the mechanical seal at the same time along the multiple small holes distributed at the circumference part, and plays a flushing role.Multi-point flushing overcomes the shortcomings of single-point flushing and makes the temperature distribution around the friction pair of the mechanical seal more uniform. However, the structure is relatively complicated, and a flushing ring needs to be added, with 6 to 8 small holes with a diameter of 3 to 4 mm. Multi-point flushing is used in media that is easy to vaporize, and can also be used in high pv value occasions that generate more frictional heat. The position of the flushing hole should be opened at the friction pair of the mechanical seal as far as possible, so as to better conduct heat away. The single-point flushing cannot be directly aimed at the graphite ring (stationary ring) of the mechanical seal, nor can it be far away from the friction pair, in which case the flushing effect will be weakened.