Mechanical seal manufacturer Quality inspection process of

The mechanical seal is a sealing device composed of two sealing elements (static ring and dynamic ring) perpendicular to the shaft, smooth and straight surfaces that stick together and rotate relative to each other. It is achieved by the pressure of the sealing medium to generate appropriate compression force on the contact surface (end face) of the rotating dynamic ring and static ring, so that the two end faces can be closely combined, and an extremely thin liquid film is maintained between the end faces. This layer of liquid film has both dynamic and static pressure, which plays the role of lubrication and balance force.

1. Cleaning and inspection of mechanical seal

1) The working principle of mechanical seal requires that there is no impurity inside the mechanical seal. Clean the moving ring, stationary ring, shaft sleeve and other parts before assembling the mechanical seal.

2) Check whether there are scratches, cracks and other defects on the surface of the moving and stationary rings, which will cause serious leakage of the mechanical seal. If possible, special tools can be used to check whether the sealing surface is flat or not. If the sealing surface is uneven, pressure water will enter the sealing surface of the dynamic and static rings of the mechanical seal after assembly, separating the dynamic and static rings, and the mechanical seal will fail. If necessary, tooling can be made for hydrostatic test before assembly.

3) Check whether the rotating and stationary ring seats have defects that affect the sealing. If there is any defect on the mating surface between the movable and stationary ring seat and the sealing ring of the movable and stationary ring.

4) Check whether the mechanical seal compensation spring is damaged and deformed, and whether the obstinacy coefficient changes.

5) Check whether there are burrs, grooves and other defects in the seal shaft sleeve.

6) Clean and check all sealing rubber rings for cracks, pores and other defects, and measure whether the diameter of rubber rings is within the tolerance range.

7) For the mechanical seal with pumping mechanism, check whether the spiral line of the screw pump has cracks, broken lines and other defects.

2. Mechanical seal assembly technical dimension check

1) Measure the dimension of the sealing surface of the rotating and stationary rings. This data is used to verify the radial width of the moving and stationary rings. When different friction materials are selected, the radial width of the hard material friction surface should be 1~3mm larger than that of the soft material, otherwise it is easy to cause the edges and corners of the hard material end face to be embedded in the soft material end face.

2) Check the clearance between the moving and stationary rings and the shaft or shaft sleeve. The inner diameter of the stationary ring is generally 1~2mm larger than the shaft diameter. For the moving ring, the inner diameter is 0.5~1mm larger than the shaft diameter to ensure the floatability, which is used to compensate for the vibration and deflection of the shaft. However, the clearance should not be too large, otherwise the moving ring seal ring will be stuck in, causing damage to the mechanical seal function.

3) Check the tightening force of mechanical seal. The mechanical seal tightening force we usually talk about is the end face specific pressure. The end face specific pressure should be appropriate. If it is too large, the friction surface of the mechanical seal will heat up, accelerate the end face wear, and increase the friction power; Too small, easy to leak. The end face specific pressure is determined when the mechanical seal is designed, and we can only determine it by measuring the mechanical seal tightening force when assembling. The normal measurement method is to measure the vertical distance between the installed stationary ring end face and the gland end face, and then measure the vertical distance between the moving ring end face and the gland end face. The difference between the two is the tightening force of the mechanical seal.

4) Measure whether the length of the compensation spring changes. The change of spring performance will directly affect the face specific pressure of mechanical seal. Generally, the length of the spring will be shortened after a long time of operation, and the mechanical seal of the compensation spring on the moving ring will also be deformed due to centrifugal force.

5) Measure the length of the static ring anti rotation pin and the depth of the pin hole to prevent the pin from being too long and the static ring from being assembled in place. This will damage the mechanical seal.

3. Grinding of moving ring and stationary ring end faces

1) After the moving ring is removed, rough grinding is carried out first, then fine grinding, and polishing can be carried out if conditions permit.

2) During rough grinding, 80~160 # abrasive shall be used to remove the machining trace. Then, use more than 160 # abrasive for fine grinding to make the finish meet the design requirements. Hard alloy or ceramic moving ring shall be polished with polishing machine after fine grinding. The strength of polishing machine can be M28~M5 boron carbide. The mirror surface is reached after polishing. The ceramic ring can be polished with chrome oxide after fine grinding with M5 agate powder.

3) The graphite filled PTFE stationary ring can be finely grinded with kerosene, gasoline or clean water without adding abrasives because of its soft material. It can also be self researched during running in, so the requirements for smoothness are not too high.

4) For the grinding method, if there is a grinder, it can be grinded on the grinder, and if there is no grinder, it can be grinded on the flat glass manually in figure 8.

4. Shaft sleeve inspection

1) Check the corrosion and wear of the shaft sleeve after it is removed for maintenance. If the corrosion or wear is slight, polish it with fine sandpaper and use it again. If the corrosion or wear is serious, electroplating after machining or replacing the shaft sleeve can be used.

5. Sealing O-ring

1) After a period of use, the sealing ring loses its elasticity or is aged in most cases. Generally, it needs to be replaced with a new one.

6. Spring

1) If the spring is not seriously rusted and can maintain its original elasticity, it can not be replaced. If the corrosion is serious or the elasticity decreases a lot, the spring needs to be replaced.

2) For mechanical seals with assembly boxes, clean the boxes and check whether the grooves are worn or deformed for correction, repair, re grooving or replacement.

3) After the mechanical seal elements are repaired, they shall be reassembled. After assembly, the pressure test shall also be carried out, and then they shall be put into normal operation.