Installation and Operating Requirements of Mechanical Seals

Mechanical seals are one of the precision and complex mechanical basic components, and are key components of various equipment such as pump-type mechanical seals, reaction synthesis reactors, turbo compressors, and submersible motors. Their sealing performance and service life depend on many factors, such as selection, machine accuracy, correct installation and use.

Requirements for precision of mechanical seals

  • The radial jumping tolerance of the shaft (or shaft sleeve) at the installation position of the mechanical seal should not exceed 0.04-0.06MM.

  • The axial movement of the rotor should not exceed 0.3MM.

  • The jumping tolerance of the sealing cavity and the positioning end face of the sealing end cover combined with the shaft (or shaft sleeve) surface should not exceed 0.04-0.06MM.

Confirmation of mechanical seals

  • Confirm whether the installed seal is consistent with the required model.

  • Before installation, carefully check against the assembly drawing to ensure the completeness of the parts.

  • For mechanical seals driven by a coiled spring, the spring is either left- or right-hand wound, and must be selected according to the direction of rotation of the shaft.

Installation of mechanical seals

The installation method varies depending on the type of mechanical seal and the type of machine, but the installation essentials are almost the same. The installation steps and precautions are as follows:

(1) Determination of the installation size: When installing, the installation size of the mechanical seal should be guaranteed according to the product manual or sample.

(2) Before installation, the shaft (or shaft sleeve) and the cover should have no burrs, and the bearing condition should be good. The seal, shaft, sealing cavity, and cover should be cleaned. In order to reduce the friction resistance, a thin layer of oil should be applied to the part where the mechanical seal is installed on the shaft for lubrication. Considering the solubility of the rubber mechanical seal O-ring, if oil is not suitable, soap water can be used. For the floating-type static ring structure without anti-rotation pins, it is not suitable for oiling, and the cover should be dry-installed.

(3) First, install the static mechanical seals ring with the cover on the shaft, being careful not to collide with the shaft, and then install the dynamic ring assembly. The fastening screws of the spring seat or transmission seat should be tightened evenly in several steps.

Before fixing the cover, push the compensating ring by hand for axial compression. After releasing, the compensating ring should automatically rebound without sticking, then lock the cover bolts evenly.

Use of mechanical seals

  • When the conveying medium has high or low temperature, or contains impurities, flammable, explosive, toxic, corresponding measures such as blockage, flushing, cooling, and filtration must be taken to ensure the normal use of mechanical seal parts.

  • Before operation, manually turn the car and pay attention to whether the torque is too large, whether there is rubbing and abnormal sound.

  • Pay attention to the direction of rotation, whether the coupling is centered, whether the lubricating oil is added properly to the bearing part, and whether the piping is correct.

  • Before operation, first open the valves for the medium and cooling water, check whether the gas in the sealing chamber is completely discharged to prevent leakage caused by static pressure, and then start the machine.

  • Whether the operation after starting is normal and stable, whether there is abnormal torque caused by shaft rotation, abnormal sound and overheating.

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