stay Mechanical seal for kettle Questions to pay attention to when selecting and using

The operating pressure of the seal shall be the pressure of the sealing medium in the seal chamber. Since the medium pressure in the seal chamber and the mechanical seals are not equal to the operating pressure of the pump, and sometimes the operating pressure of the seal is higher, equal to or lower than the operating pressure of the pump, the operating pressure of the seal should be determined according to the detailed pump structure and conditions. For example, for a single-stage cantilever pump, consider whether the impeller has a balance hole or a back blade, and determine the operating pressure of the shaft seal according to the placement of the multi-stage pump stages.

Generally, in the practice of mechanical seal, when the operating mechanical seal pressure is higher than 3MPa, it is regarded as a high-pressure mechanical seal, and a balanced seal is required. When the pressure exceeds 15MPa, a multi-stage seal can be used and stepwise pressure reduction can be made.

When the pressure exceeds 1MPa, the structure type of eliminating force deformation (such as multi face seal) shall be considered for the seal.

Generally, for seals with good lubricity and higher density than gasoline products, non-equilibrium seals can be selected below 0.7MPa; Non balanced seal is also used when the value is lower than 6.6MPa. m/s. For oil products with density lower than 0.6kg/L, balanced seal shall be used. For the occasions with low viscosity and poor lubrication, the balanced seal shall be selected under the pressure of 0.2-0.33MPa.

2. Weekly speed

Generally, the seal face circumferential velocity is indicated by the uniform circumferential velocity of the seal face. Seals with a peripheral speed higher than 25 m/s are generally considered as high-speed seals. For high-speed seals, in order to avoid the influence of centrifugal force and mixing heat, stop type seals should be selected. If the circumferential speed is high and the pV value is too high, the central ring can be used to reduce the circumferential speed, or the hydrodynamic seal or hydrostatic seal can be used.

3. Temperature

The operating temperature is usually indicated by the medium temperature in the sealing box. Mechanical seals are generally applicable when the sealing medium temperature is below 80 ℃. With regard to easily gasified media, it should be considered together with the pressure to make the upper working temperature 13.9 ℃ lower than the boiling point, otherwise a stable liquid film cannot be guaranteed.

Generally, the medium temperature is 80-150 ℃, which is a normal hot commodity (ordinary heat) seal, while the mechanical seal with a temperature higher than 150 ℃ is a high-temperature seal. The data of auxiliary sealing elements are usually subject to temperature constraints. The seal with temperature lower than - 20 ℃ is usually low-temperature seal, while the seal with temperature lower than - 50 ℃ is cryogenic seal. The sealing method for operation at high and low temperature shall not only adopt data and structure methods, but also cooling and insulation methods for auxiliary methods.

4. Shaft diameter

Large shaft diameter seal usually refers to the seal with shaft diameter greater than 120mm; Small shaft diameter seal usually refers to the seal with shaft diameter less than 25mm, which is usually a mechanical seal.

5. Medium property

For the medium with weak corrosivity, the built-in seal can be selected. For the medium with strong corrosivity, it is difficult to handle the selection of tension spring in the elastic element. External seal can be selected, which is applicable when the pressure is low.

For products that are easy to crystallize, solidify and have high viscosity, the single large tension spring structure should be selected, which is better than the small tension spring structure scattered at multiple points, because it is not easy to block. For flammable, explosive and toxic goods, it is necessary to consider double end face or cascade or multistage sealing to ensure positive sealing.