1. Installation and use requirements of mechanical seal
1. Mechanical seal requirements for machine accuracy (take pump mechanical seal as an example)
(1) The radial runout tolerance of the shaft (or sleeve) where the mechanical seal is installed does not exceed 0.04～0.06mm.
(2) The axial movement of the rotor does not exceed 0.3mm.
(3) The tolerance of the positioning end of the sealing cavity combined with the sealing end cover facing the surface of the shaft (or sleeve) does not exceed 0.04 to 0.06mm.
2. Confirmation of seals
(1) Confirm whether the installed seal is consistent with the required model.
(2) Before installation, carefully compare with the assembly drawing, whether the number of parts is complete.
(3) The mechanical seal is driven by parallel coil springs. The springs are divided into left and right, which must be selected according to the rotation direction of the rotating shaft.
Second, selection method
According to different working conditions and medium properties, mechanical seals include high temperature and low temperature resistant mechanical seals, high pressure resistant and corrosion resistant mechanical seals, particle resistant mechanical seals and mechanical seals suitable for light hydrocarbon media that are easy to vaporize. Use of mechanical seals of different structural types and materials.
The main parameters of selection include: the pressure of the sealed cavity (MPa), the temperature of the fluid (℃), the working speed (m/s), the characteristics of the fluid and the effective space for installing the seal.
The basic principles of type selection are: 1. According to the pressure of the sealing cavity, determine whether the sealing structure adopts balanced or unbalanced type, single end face or double end face, etc.
2. According to the working speed, determine whether to use rotary or static type, fluid dynamic pressure type or non-contact type.
3. According to the temperature and fluid properties, determine the friction pair and auxiliary sealing materials, as well as the correct selection of lubrication, flushing, heat preservation, cooling and other mechanical seal circulation protection systems.
4. According to the effective space for installation and sealing, determine the use of multiple springs or single springs or wave springs, internal or external.
3. Installation
The installation method varies with the type of mechanical seal and the type of machine, but the installation methods are almost the same. The installation steps and precautions are as follows: (1) The installation size is determined according to the product instruction manual or sample. Ensure the installation size of the mechanical seal.
(2) Before loading, the shaft (sleeve) and the gland should be free of burrs, and the bearings should be in good condition; seals, shafts, sealed chambers, and gland should be cleaned. In order to reduce frictional 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 compatibility of rubber O-rings, if oil is not suitable, soapy water can be applied. The floating static ring has no anti-rotation pin structure and should not be oiled. It should be installed dry into the gland.
(3) First install the static ring together with the gland on the shaft, taking care not to touch the shaft, and then install the moving ring assembly. The set screws of the spring seat or transmission seat should be tightened evenly in several times.
Before fixing the gland, push the compensation ring by hand for axial compression. After loosening, the compensation ring can automatically spring back without jamming, and then lock the gland bolt evenly.
Fourth, use
(1) When the temperature of the conveying medium is too high, too low, or contains impurity particles, flammable, explosive, and toxic, corresponding measures such as blocking, washing, cooling, and filtering must be taken.
(2) Before turning, use a handcart, pay attention to whether the torque is too large, whether there is friction or abnormal sound.
(3) Pay attention to the direction of rotation, whether the coupling is centered, whether the addition of lubricating oil at the bearing is appropriate, and whether the piping is correct.
(4) Before operation, first open the medium and cooling water valves, check whether the gas in the sealed chamber is completely discharged to prevent leakage caused by static pressure, and then start the operation.
(5) Whether the work is normal and stable after driving, whether there is abnormal torque caused by shaft rotation, and abnormal noise and overheating.
|
Top News