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Assembly and inspection of mechanical seal of md mine wear-resistant multi-stage centrifugal pump

30 Mar 2021Email

The maintenance process of the mechanical seal of md wear-resistant multi-stage centrifugal pumps for mining is more complicated. To ensure that the mechanical seals of the assembled wear-resistant multi-stage centrifugal pumps for mining are leak-free, it is necessary to check the technical dimensions of the mechanical seal.

MD mine wear-resistant multi-stage centrifugal pump mechanical seal assembly technology size check

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

2. Check the clearance between the moving ring, the static ring and the shaft or the shaft sleeve. The inner diameter of the static ring is generally 1-2mm larger than the shaft diameter. For the moving ring, to ensure floatability, the inner diameter is 0.5-1mm larger than the shaft diameter to compensate Vibration and deflection of the shaft, but the gap should not be too large, otherwise the moving ring seal ring will be stuck and the mechanical seal function will be damaged.

3. Check the tightness of the mechanical seal. The mechanical seal tightening force we usually talk about is the end-face specific pressure. If the end-face specific pressure is appropriate, if it is too large, it will heat the friction surface of the mechanical seal, accelerate the wear of the end face, and increase the friction power; if it is too small, it is easy to leak. The specific pressure of the end face is determined during the design of the mechanical seal, and we can only determine it by measuring the tightness of the mechanical seal during assembly. The usual measurement method is to measure the vertical distance from the end face of the installed static ring to the end face of the gland. When measuring the vertical distance from the end face of the moving ring to the end face of the gland, the difference between the two is extremely tight force of the mechanical seal.

4. Measure whether the length of the compensation spring has changed. Changes in spring performance will directly affect the specific pressure of the mechanical seal. Under normal circumstances, 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 anti-rotation pin of the static ring and the depth of the pin hole to prevent the pin from being too long and the static ring cannot be assembled in place. This situation will damage the mechanical seal.

 

Assembly of mechanical seal of md mine wear-resistant multi-stage centrifugal pump

The mechanical seal can be reassembled after cleaning, inspection and technical dimension check. In this process, the following points should be paid attention to:

1. When assembling, all sealing rings should be coated with soapy water and other lubricants, so as to avoid damaging the rubber rings during the assembly process. Grease is applied between the sealing surfaces of the moving and static rings to prevent the sealing surfaces of the moving and static rings from wearing before the pump starts.

2. When assembling the floating ring, be careful not to knock down the floating ring spring, so as not to affect the floating performance of the floating ring after the spring is knocked down. After the floating ring is assembled, you can gently press the floating ring to determine whether there is good floating performance.

3. When installing the seal, handle it with care to prevent damage to the seal, and clean the seal and cavity during installation.

4. When tightening the mechanical seal gland, the tightening bolts should be evenly stressed to prevent uneven force from damaging the mechanical seal. For quick-fitting mechanical seals, do not forget to fix the position of the positioning piece radially away from the shaft after the overall assembly is completed.

 

Inspection of mechanical seal of md mine wear-resistant multi-stage centrifugal pump

The working principle of the mechanical seal requires no impurities inside the mechanical seal. Before assembling the mechanical seal, clean the moving ring, static ring, shaft sleeve and other parts thoroughly. Key inspection:

1. Whether there are defects such as scratches, cracks, etc. on the surface of the moving and static rings, these defects will cause serious leakage of the mechanical seal. If possible, you can use special tools to check whether the sealing surface is flat or not. The pressure water will enter the dynamic and static ring sealing surfaces of the mechanical seal after assembly, separate the dynamic and static rings, and the mechanical seal will fail. If necessary, the tooling can be made for hydraulic test before assembling.

2. Check whether the dynamic and static ring seat has defects that affect the seal. For example, whether there are defects such as scratches on the mating surface of the dynamic and static ring seat and the dynamic and static ring sealing rubber ring.

3. Check whether the mechanical seal compensation spring is damaged and deformed, and whether the stubborn coefficient changes.

4. Check whether there are defects such as burrs and groove marks on the sealing shaft sleeve.

5. Clean and check whether there are cracks, pores and other defects in all sealing rubber rings, and measure whether the diameter of the rubber ring is within the working tolerance range.

6. For mechanical seals with pumping mechanisms, check the spiral line of the pump for cracks, disconnections and other defects.

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