Selection of mechanical seal-according to working parameters and shaft diameter-

Selection of mechanical seal-selection according to working parameters and shaft diameter

　2017-08-21　　

Mechanical seal selection-selection according to working parameters and shaft diameter:

p refers to the medium pressure in the sealed cavity. According to the value of p, it can be preliminarily determined whether to choose a balanced seal and the degree of balance. Generally in the practice of mechanical seals, when p>3MPa is regarded as a high-pressure mechanical seal, a balanced seal is required. At that time, the general single-end face balanced seal was difficult to meet the sealing requirements. At this time, a series-type multi-end face seal can be used and the pressure is reduced step by step. For media with high viscosity, good lubricating performance, p<0.8MPa, or low-viscosity, poor lubricating media, p<0.5MPa, unbalanced seals are usually used.

v refers to the average peripheral speed when the seal end face rotates. According to the value of v, it can be determined whether the elastic element rotates with the shaft, that is, the spring rotating or spring static structure is adopted. Generally, the spring rotation type can be used for v<20~30m/s. In the case of high speed, in order to avoid the strong vibration caused by the unbalanced mass of the rotating parts and avoid the influence of centrifugal force and stirring heat, it is best to adopt a spring static structure. If # is too high, measures such as an intermediate ring can be used to reduce the peripheral speed, or a hydrodynamic or static pressure seal can be considered.

t refers to the temperature of the sealed medium, that is, the working temperature. When the temperature of the sealed medium is below 80°C, general mechanical seals can be applied. For the easily gasified medium, the working temperature should be about 14℃ lower than the boiling point to ensure a stable liquid film along with the pressure. According to the size of t, the material of the auxiliary sealing ring, the cooling method of the sealing curve and its auxiliary system can be determined. When the temperature t is in the range of 0~80℃, the auxiliary sealing ring usually uses nitrile rubber O-ring. Generally, the temperature of the medium is within the range of 80~150℃, and the mechanical seal is high temperature sealing. Generally, the auxiliary sealing element material is subject to temperature restrictions. The seal with a temperature lower than -20°C is an ordinary low-temperature seal; the seal with a temperature lower than -50°C is a cryogenic seal.

When t is in the range of -50~150℃, according to the corrosiveness of the medium, fluororubber, silicone rubber or PTFE molded packing seal ring can be selected; when the seal is high temperature seal or cryogenic seal, rubber And polytetrafluoroethylene is prone to low-temperature brittleness or high-temperature aging, in this case, a metal bellows structure can be used instead. For seals that work at high and low temperatures, not only measures are taken in terms of materials and structures, but also cooling and heat preservation measures are also taken in terms of auxiliary measures.

The shaft diameter is the diameter of the rotating shaft. Generally, a seal with a shaft diameter greater than 120mm is called a large shaft diameter seal, a seal with a shaft diameter less than 25mm is called a small shaft diameter seal, and the seal between the two is a general seal. The seal type can be selected according to the standard.

High temperature oil pump cartridge metal bellows mechanical seal

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Selection of mechanical seal structure type 　　 Selection of mechanical seal-selection according to medium characteristics