Problems and Solutions of Machine Sealing at High Temperature

Mechanical seals are used in various industrial fields, so they will be used in different environments and working conditions. In general, if the temperature of the medium exceeds 120°C, it is considered to be a high temperature seal. At this time, there may be some problems with the mechanical seal.

(1) Due to the increase of the end face temperature of the friction pair, the liquid film between the sealing end faces is vaporized, the friction coefficient increases, the wear is increased, the temperature rise increases, and the sealing ring is thermally deformed or thermally cracked and fails.

(2) The auxiliary sealing ring material in the mechanical seal is generally rubber or polytetrafluoroethylene, which is easy to age and decompose in a high temperature environment for a long time, resulting in seal failure.

(3) The elastic elements of the mechanical seal are prone to fatigue and creep under high temperature, which makes the seal fail.

(4) High temperature will aggravate the corrosion of metal materials and shorten the service life of the mechanical seal.

In order to ensure the normal operation of the mechanical seal in a high temperature environment, the following measures can be taken to solve the problem.

1. Add cooling and flushing device to the machine seal.

2. Choose high temperature resistant materials and choose different materials according to different working temperatures.

The upper temperature limit for nitrile rubber is 80°C, for silicone rubber and fluororubber 200°C, and for PTFE is 250°C. In addition, the non-metallic friction pairs in the mechanical seal are mostly made of graphite impregnated materials, so different types of impregnated graphite should be selected according to different working temperatures. Generally, the applicable temperature range of babbitt-impregnated graphite is less than 150°C, and the applicable temperature range of resin-impregnated graphite is 170~200°C. Graphite impregnated with copper, aluminum and lead can be used under working conditions of less than 400°C. The moving ring assembly should use materials with similar expansion coefficients as much as possible to prevent the connection between the moving ring and the moving ring seat from loosening under high temperature.

3. Select metal bellows mechanical seal.

Metal bellows seals have been used a lot in high temperature sealing in recent years, and have achieved good results. In this type of mechanical seal, the metal bellows replaces the spring in the ordinary mechanical seal, eliminating the need for the auxiliary seal ring of the moving ring, and does not need to overcome the friction and wear between the moving ring and the rotating shaft during compensation, so it is generally used at high temperatures. Can achieve good results.

There are many types of mechanical seals, and some are professional in the industry. When users choose, they must make a reasonable choice according to the specific operating conditions, environment and field of use, especially in such a high temperature environment. For use under high temperature, be sure to choose a material that can adapt to high temperature.