Correct installation and use of mechanical seals

A mechanical seal refers to a device that prevents fluid leakage by keeping at least one pair of end faces perpendicular to the rotation axis under the action of fluid pressure and the elastic force (or magnetic force) of the compensation mechanism and the cooperation of the auxiliary seal to keep fit and slide relatively. The elastic loading mechanism and auxiliary seal are mechanical seals of metal bellows, which we call metal bellows seals. In light-duty seals, rubber bellows are also used as auxiliary seals. The rubber bellows have limited elasticity, and generally need to be supplemented by springs to meet the loading elasticity. 'Mechanical seal' is often referred to simply as 'mechanical seal'.

The correct installation and use of the mechanical seal is the key to ensuring long-term stability, safety and reliability. Improper installation and use will result in poor sealing performance, shortened life or seal failure. The following briefly introduces the installation and use precautions for reference:

1. Check: Whether the dimensional accuracy, geometric accuracy and mutual relationship of the relevant parts of the installation mechanical seal meet the requirements.

1. The dimensional tolerance, surface roughness and chamfer transition shape of the shaft and static ring seat matched with the mechanical seal are shown in the figure below;

2. The radial runout of the shaft should be ≤0.04mm, and the axial movement should be ≤0.3mm;

3. The verticality between the sealing cavity and the gland combined with the positioning end facing the axis centerline is ≤0.04mm;

4. Check whether the axial and radial dimensions of the assembly position of the sealing chamber and the gland are correct.

2. Installation:

1. The assembly size must be guaranteed as required;

2. During the entire installation process, the mechanical seal and the equipment sealing cavity should be kept clean, and it is strictly forbidden to bump or knock, so as to avoid deformation and damage of the friction pair of the mechanical seal and seal failure;

3. The sealing part can be coated with a layer of clean lubricating fluid for smooth installation. It is recommended to use soapy water or silicone ester for ethylene-propylene rubber;

4. When installing the static ring gland, the tightening bolts must be evenly stressed to ensure that the end face of the static ring is perpendicular to the center line of the end cover, and note that the anti-rotation groove on the back of the static ring should be aligned with the anti-rotation pin, but not in conflict;

5. When installing the seal related to the rotation direction (such as the coil spring transmission and the hook spring transmission), pay attention to whether the spring rotation direction is correct, and the spring should be tightened as it is rotated;

6. When installing the rotating ring part, when relying on the retaining ring or the impeller or the spring seat to be fixed with the shaft, the working length of the rotating ring part should be guaranteed. After installation, the rotating ring should be compressed by hand to make the rotating ring move flexibly in the axial direction, and able to restore the bit;

7. After installation, turn the shaft by hand to check whether there is a sense of weight. If so, check whether the installation is correct.

3. Use:

1. Before normal driving, a static pressure test is required to check the sealing effect of the end face of the mechanical seal, the sealing ring and the sealing end. If there are any problems, check and solve them one by one.

2. Before normal use, run at normal pressure and temperature, and run in for a period of time to make the end faces fit more evenly, and then run under normal working conditions;

3. During work, the sealing cavity should be filled with liquid or sealed medium, keep the end face lubricated, and avoid the phenomenon of evacuation and dry friction.

4. When the temperature of the conveying medium is too high, too low, easy to crystallize or contains impurities, particles, flammable, explosive and toxic, the corresponding flushing, cooling and filtering must be taken according to the piping system in JB/T6629 or API610 standard. , blocking and other measures to ensure the normal operation of the mechanical seal.