Centrifugal pump mechanical seal selection precautions

Centrifugal pump mechanical seal selection precautions



First, the sealing pressure

Sealing pressure is one of the important parameters to consider when selecting a mechanical seal. Under normal circumstances, when the sealing pressure is less than 0.7Mpa, both balanced and unbalanced mechanical seals can meet the requirements of use. When the sealing pressure is 0.7~12MPa, consider using a balanced mechanical seal. When the sealing pressure is greater than 12 MPa, it is considered to adopt a series seal type (pressureless double mechanical seal) to achieve step-by-step pressure reduction.

Second, the physical and chemical properties of the transport medium

For media that are not corrosive or corrosive, a built-in mechanical seal is available. For corrosive media, it is difficult to solve the problem of Spring selection in the elastic element. When the pressure is low, an external mechanical seal can be used. For media that are easy to crystallize, have solid particles, and have high viscosity, a single spring structure should be used. For flammable, explosive, toxic and other media that are prohibited from leaking, double mechanical seals must be considered to ensure absolute safety.

Third, the working temperature

Operating temperature generally refers to the temperature of the medium within the sealed chamber. When the working temperature is lower than 80 °C, the general mechanical seal can be applied. For easy vaporization medium, it should be considered at the same time as the pressure, so that the working temperature is 13.9 °C lower than the boiling point, otherwise it is difficult to ensure a stable liquid film between the sealing friction pairs. Mechanical seals with media temperatures between 80 and 150 ° C are common seals, while mechanical seals with temperatures above 150 ° C are high temperature seals. For high temperature sealing, the auxiliary system with heat exchanger is usually used according to the specific working conditions, so that the temperature of the medium in the sealed chamber is controlled within a reasonable range, and the temperature of the sealing ring and the friction pair does not exceed the specific sealing technical conditions. Specified usage limits. Mechanical seals used below 20 ° C are low temperature seals. For mechanical seals operating in low temperature environments, in order to avoid the formation of ice in the air outside the friction pair, the PLAN62 system is usually required to remove water vapor using a nitrogen purge. For mechanical seals operating at high temperatures and low temperatures, in addition to selecting the appropriate auxiliary system, the sealing material and structure must be fully considered.

Fourth, the sealing work speed

The sealing working speed refers to the linear speed of the sealing working surface, which is an important factor affecting the running stability and the wear of the sealing end face. When the line speed is greater than 30 m/s, it is often referred to as a high speed seal and a static mechanical seal should be used. Dynamic and static ring end materials should also be specially treated to meet wear requirements.

Hebei Innovation Sealing Material Co., Ltd.

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