If the temperature is too low or too high, it will cause certain damage to the mechanical seal. The following describes the specific maintenance method of the mechanical seal at low temperature.
In the refinery chemical plant, the medium transported at a low temperature generally has the characteristics of small creepage, poor lubricity, and easy gasification, and the medium absorbs a large amount of heat during gasification, causing the ambient temperature to drop sharply, causing condensation of moisture in the air. Leading to the end face and its surrounding ice, so that the end face is not tight enough to cause leakage. At the same time, due to poor lubricity, the end face friction generates more heat. If it cannot be transferred in time, it will inevitably increase the gasification at the end face, causing a vicious cycle and accelerating the early failure of the sealing surface. In addition, the low-temperature sealed auxiliary seal ring is hard to break off at low temperatures and is also prone to leakage.
For low temperature sealing, in addition to selecting the appropriate auxiliary sealing ring material, pay attention to the following points.
1. Improve the sealing structure and correctly select the friction pair material. Practice has proved that opening a circular arc groove on the surface of the static ring can form a hydrodynamic seal, increase the bearing capacity of the fluid film, improve the lubrication condition of the end face, and effectively extend the working life of the machine seal. In terms of end face pairing. Tungsten carbide-M106K graphite team is generally superior to other materials because of its good lubricity, low friction coefficient and good thermal conductivity.
2. Select the appropriate end face specific pressure. Low-temperature sealing is prone to gasification and icing due to poor lubricity of the end face, so the end face specific pressure can be appropriately reduced under the premise of ensuring reliable sealing. Generally, the mechanical seal ratio is recommended to be 0.29--0.59MPA, and the lower limit can be taken for low-temperature sealing. For the metal bellows mechanical seal, since the moving ring has no axial friction, the end face specific pressure can even be lower than the lower limit.
3. Take appropriate measures on the process. For example, the water content of the medium should be reduced as much as possible; the pressure in the sealed chamber should be kept relatively stable; the flushing and cooling device should be matched as much as possible; and the machine seal should be properly preheated before the equipment is started.
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