The common mechanical seal structure used in pumps consists of components such as a stationary ring (static ring), rotating ring (dynamic ring), elastic element spring seat, fastening screws, rotating ring auxiliary sealing ring, and stationary ring auxiliary sealing ring. The anti-rotation pin is fixed on the pressure cover to prevent the stationary ring from rotating. The rotating ring and stationary ring are often referred to as compensating or non-compensating rings depending on whether they have axial compensation ability.
Pay attention to avoid installation deviation during mechanical seal installation. The tightening of the pressure cover should be carried out after aligning the coupling, and the bolts should be evenly supported to prevent the end face deviation of the pressure cover. Use a plug gauge to check each point, and the error should not be greater than 0.05mm. Check the fit clearance (i.e., concentricity) between the pressure cover and the shaft or shaft sleeve. It should be uniform on all sides, and the allowable deviation of the plug gauge check for each point is not greater than 0.01mm.
The spring compression amount shall be in accordance with the requirements, and no phenomena such as excessive or insufficient compression are allowed. The error requirement is 2.00mm. Excessive compression will increase the end face contact pressure and accelerate the end face wear. Insufficient compression will cause insufficient contact pressure and fail to achieve the sealing effect.
After the dynamic ring is installed, it should be able to bounce back automatically after being pressed against the spring.
In order to ensure the stable operation, long service life, and low leakage performance of the pump mechanical seal, it is very important to install it correctly on the machine. Matters needing attention when installing the pump mechanical seal:
Confirm the components
When installing the pump mechanical seal on the machine, it is necessary to check it carefully against the assembly drawing to confirm whether the parts are complete. At this time, attention should be paid to abnormal phenomena such as scratches or defects on the sealing friction pair sealing surface, sealing ring, etc. and to the surface of the shaft or shaft sleeve that comes into contact with the packing and sealing ring. If anomalies are found, they must be replaced or repaired before use.
Do not bring more parts than needed to the site during installation
If there are remaining parts after installation, there must be places where components are missed during installation; if there is a shortage of parts, unnecessary parts are assembled, which is exactly a self-check during installation.
The pump mechanical seal is a highly precise mechanical component, and its correct installation and operation have a great influence on its service life. The technical requirements for the pump and the pump mechanical seal mating parts for installing the pump mechanical seal are as follows:
Shaft bending: not more than 0.05mm.
Rotor swing: not more than 0.06mm near the shaft sleeve where the dynamic ring sealing ring is located.
The axial movement of the shaft cannot exceed ±0.5mm. If a shaft sleeve is used, there must be no looseness in the shaft sleeve.
The alignment error range for gear-type couplings is no more than 0.08-0.10mm and for flexible couplings, it is no more than 0.05-0.06mm.
The end parts of the shaft sleeve where the dynamic ring sealing ring is installed and the end parts of the pressure cover where the stationary ring sealing ring is installed should be chamfered and smoothed.
The allowable deviation of the concentricity between the pressure cover (stationary ring seat) and the seal mating stop groove to the shaft centerline is 0.05mm. The perpendicularity value of the surface in contact with the gasket to the centerline should be 0.03-0.05mm. If the requirement cannot be met, the seal cavity needs to be processed.