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What Are The Requirements For The Selection And Use Of Mechanical Seals?
Apr 10, 2018

What are the requirements for the selection and use of mechanical seals?

Each type of mechanical seal can only function effectively if it is used within the specified range. Improper selection of mechanical seals can lead to a significant reduction in sealing performance, shortened life, and even failure. The following is a selection guide for mechanical seals:


Sealing chamber medium pressure P

     P ≤ 0.8 MPa, non-equilibrium type, P ≥ 0.5 MPa, use mechanical seal balance type.

     Mechanical seal selection guide

     Line speed V

     The speed of the line should be combined with the pressure, temperature, media characteristics, etc. to determine the form of the spring.

The PcV value relates to the stability (vaporization) of the fluid film between the sealing surfaces and the wear resistance of the friction pair.

     Without external cooling, the maximum service temperature of the seal generally depends on the safe use temperature of the auxiliary seal material.

The speciality of the medium

     Certain media may have special requirements for secondary seals. For example, solvents such as solvents cannot use fluoroelastomers, mineral oils cannot use EPDM rubber, and users should pay special attention.

     1) The low-viscosity medium is easy to produce dry friction, and the balance type is preferred; the high-viscosity medium should use the forced transmission structure.

     2) Externally mounted PTFE bellows seals are recommended for strong corrosion.

Mechanical seal considerations

     1. The radial runout of the sealed main shaft should be ≤ 0.04mm (0.06mm) and the axial turbulence ≤ 0.3mm, and the corresponding parts of the shaft and the stationary ring seat should be machined as shown in the figure.

     2. All parts of the sealed chamber, shaft, and mechanical seal should be cleaned without contamination, bumps, scratches, and extraordinary to prevent impurities, dust and particles from being carried into the sealed chamber.

     3. It is forbidden to collide and beat wildly during installation. The surface of the friction pair should be absolutely clean.

     4. The static ring gland must have sufficient strength, and tighten the screws evenly during installation to ensure that its end face is perpendicular to the axis.

     5. After installation, lightly press the ring, and it should be flexible and flexible; manually turn the car, it should be able to run freely.

     6. Conduct a static pressure test to see if there is a leak.

     7. start the trial run, pay attention to whether there is abnormal sound.

     8. the use of temperature exceeds 80 °C forced circulation method should be used to seal the cooling.

     9. sealed pipeline must be kept open; dry friction is strictly prohibited.

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Susie Ding


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