The equipment and application of mechanical seals for pumps are widely used in various types of pumps. Mechanical seal is a high-precision sealing device that requires certain equipment and operating conditions.

1. General guidelines for the use of mechanical sealing equipment

(1) Clarify the situation of the equipment by knowing the rotational speed and diameter of the equipment shaft; The manufacturing accuracy and sealing chamber scale of the equipment, the service life of the equipment itself, and the orientation of the equipment in the production process need to be fully balanced.

(2) Budget medium pressure. The sealing chamber pressure of a pump is usually not the pump outlet pressure, but lower than the pump outlet pressure

(3) Clarify the condition of the sealing medium. You need to know the condition of the sealing medium, whether it is in gas or liquid state, whether the medium contains particles, and the particle situation; Knowing the properties and temperature of the medium is essential for selecting appropriate cooling, flushing, and smoothing methods.

2. Skill requirements for the application of mechanical sealing equipment

(1) The radial runout of the shaft or sleeve of the mechanical seal part of the equipment should comply with Table 1. The surface roughness of the shaft or sleeve should meet the skill requirements, and the outer diameter scale should be h6.

(2) The axial displacement of the transmission shaft shall not exceed 0.2mm.

(3) The runout of the sealed cavity end face to the shaft surface should comply with Table 2

Table 1 Radial Jump Service

(4) The end faces of the shaft or sleeve and the sealing chamber should have chamfers.

(5) When the temperature of the transport medium is too high, too low, or rich in impurity particles, flammable, explosive, or toxic, corresponding measures such as sealing, flushing, cooling, and filtering should be adopted.

(6) For some mechanical seals that rely on tension spring transmission, it is necessary to pay attention to the rotation direction of the tension spring, that is, the direction of shaft rotation should make the tension spring tighter and tighter, otherwise it will cause seal failure. The selection of tension spring rotation direction is determined by the following method: from the static ring to the dynamic ring, when the shaft rotates clockwise, a right-handed tension spring is used, and conversely, a left-handed tension spring is selected.

3. Equipment methods for mechanical seals

Mechanical seal components have strict requirements in terms of manufacturing accuracy and equipment accuracy. If the equipment is not suitable, it will affect the lifespan and sealing function of the seal, and in severe cases, it will cause the seal to fail quickly.

Preparation before equipment and equipment precautions

① Check if the type and specifications of the mechanical seal to be used for the equipment are correct, and if the parts are missing.

② Check if there is any damage to the components of the mechanical seal, especially whether the sealing end faces of the moving and stationary rings are damaged. If any damage is found, it needs to be repaired or replaced with new parts. Each sealing component needs to be cleaned with gasoline or kerosene, and the surface of each component should be free of dust and foreign objects.

③ Are there burrs, grooves, etc. on the surface of the shaft or sleeve, the inner wall of the sealing chamber, and the inner and outer surfaces of the sealing end cover. If burrs or grooves are found, they should be smoothed and polished, and cleaned with gasoline or kerosene. Keep cleaning and there should be no dust or debris attached to the surface.

④ Do not use unclean cloth or cotton gauze to wipe the surface of the moving and stationary rings. Instead, use clean and soft gauze, degreased cotton, or other materials to wipe them.

⑤ During the equipment process, cleanliness should be maintained to ensure that the sealing end faces of the moving and stationary rings are not scratched or damaged. In order to facilitate installation, the oil should be altered on the surface of the shaft or shaft sleeve, as well as on the surface of the cover and sealing ring to avoid dry conflicts during start-up.

Equipment second

① Assembly of mechanical seal stop components:

a. Insert the anti rotation pin into the corresponding hole of the sealed end cover;

b. Place the static ring sealing ring onto the static ring, and insert the static ring into the sealing end cover, taking care to ensure that the anti rotation pin enters the groove of the static ring. When covering the equipment, be careful not to let the static ring touch the shaft. The bolts should be tightened evenly in several stages.

② Assembly of mechanical seal rotating components: Assemble the rotating components of the mechanical seal onto the shaft in sequence. If there is a shaft sleeve, the rotating parts of the mechanical seal should be assembled onto the shaft sleeve in sequence, and then the shaft with the rotating parts of the mechanical seal should be fitted onto the shaft.

③ The end cap is installed on the sealing body and evenly tightened with screws.

④ Is the test drive easy? If the test drive is not moving or difficult, check if the equipment dimensions are correct.

4. Troubleshooting of mechanical seal operations

1 leaked from the beginning

① Check if the quality of the equipment meets the skill requirements and if the tightening amount of the spring conforms to the rules.

② Check if the sealing end faces of the moving and stationary rings are damaged.

③ Check if the sealing end face is compliant.

There were too many leaks in the homework, and it is necessary to park and check at this moment

① Check the wear condition and changes in appearance quality of the sealing end faces of the dynamic and static rings. If they are damaged, they should be repaired or replaced with new parts.

② Check if the equipment orientation of the auxiliary sealing rings of the dynamic and static rings is correct (such as the lip of the V-ring facing the pressure end) and if there is any damage. If there is an installation error, start the device from scratch. If it is damaged, replace it from scratch.

③ Check if solid impurities are mixed into the sealed chamber and if the transmission seat is filled with impurities that affect the axial lifting of the moving ring and the compensation of the tension spring.

④ Check if the fastening screw is loose and if it affects the normal operation of the mechanical seal.

⑤ Check if the screws securing the end cap are loose, causing the sealing end cap to deflect.

⑥ Check if the axial displacement and radial oscillation of the pump exceed the skill requirements for application.

⑦ If installing the shaft sleeve, check if the seal between the shaft sleeve and the shaft is damaged and if the orientation is correct.

⑧ Check for the circulation of sealing fluid inside the sealed body and whether the mechanical seal is in a dry conflict state

There are various types of mechanical seals used in pumps, but there are primarily five leakage points:

(l) Sealing between shaft sleeve and shaft;

(2) Sealing between the moving ring and the shaft sleeve;

(3) Sealing between dynamic and static rings;

(4) Sealing between the stationary ring and the stationary ring seat;

(5) The sealing between the sealing end cap and the pump body.