1. Basic concept of mechanical seal of centrifugal pump:?
Mechanical seal refers to a device which consists of at least a pair of end faces perpendicular to the rotating shaft, keeps in contact and slides relatively under the action of fluid pressure and elastic force (or magnetic force) of compensation mechanism, and with the cooperation of auxiliary seal. The auxiliary seal of the compensation ring is a metal bellows, which is called bellows mechanical seal. ?
2. Composition of mechanical seal:?
There are mainly the following four types of components. A. main seal: moving ring and static ring. B. auxiliary seal: sealing ring. Compression parts: spring and push ring. D. transmission part: basket seat and key or fixing screw?
Two. ? Problems needing attention in mechanical sealing work:?
1. Precautions during installation?
A. Pay special attention to avoid installation deviation during installation.
(1) Tighten the gland after the coupling is centered, and the bolts should be evenly supported to prevent the end face of the gland from deviating. Check all points with a feeler gauge, and the error is not more than 0.05 mm. ..
(2) Check the fit clearance (i.e. concentricity) between the gland and the outer diameter of the shaft or sleeve, which should be uniform around, and check the tolerance of each point with a feeler gauge not greater than 0.01mm.. ?
B. The compression of the spring should be carried out according to the regulations, and it is not allowed to be too large or too small, and the error requirement is 2.00 mm. If the pressure is too high, the specific pressure of the end face will increase, and the end face will wear at another speed. If it is too small, the specific pressure will be insufficient and the sealing effect will not be achieved. ?
C. After the movable ring is installed, the beard can move flexibly on the shaft, and the movable ring should be able to rebound automatically after being pressed on the spring. ?
2. Precautions during disassembly?
A. be careful when removing the mechanical seal. Never use a hammer and a flat shovel to avoid damaging the seal. You can make a pair of steel wire hooks and pull out the sealing device at the position where it extends into the gap of the transmission seat in the self-financing direction. If the scale cannot be removed, it should be cleaned before removal. ?
B. If both ends of the pump are mechanically sealed, take care of each other during assembly and disassembly to prevent one from paying attention to the other. ?
C for the mechanical seal that has been operated, if the gland is loose and the seal moves, the moving ring and static ring parts must be replaced, and it is not allowed to be tightened again for further use. Because the original running track of the friction pair will change after the sample moves, the seal of the contact surface is easy to be destroyed. ?
Three. ? Normal operation and maintenance of mechanical seal:
1.？ What are the preparations and precautions before departure?
A. Check whether the mechanical seals, accessories and pipelines are installed completely and meet the technical requirements. ?
B before starting the mechanical seal, conduct a static pressure test to check whether the mechanical seal leaks. If there are many leaks, find out the reasons and try to eliminate them. If it is still invalid, it should be disassembled for inspection and reinstalled. General hydrostatic test pressure is 2 ~ 3kg/cm2. ?
C. Turn the car in the direction of the pump to check whether it is light and uniform. If the steering is difficult or not moving, check whether the assembly size is wrong and whether the installation is reasonable. ?
2. Installation and shutdown?
A. Before starting, keep the sealed cavity filled with liquid. When conveying curing medium, steam should be used to heat the sealed cavity to melt the medium. Turn the car before starting to prevent the soft ring from breaking due to sudden start. ?
B. For the mechanical seal using the external oil seal system of the pump, the oil seal system should be started first. Finally stop the oil sealing system after parking. ?
C. After the hot oil pump stops, the cooling water of the oil seal cavity and the end face seal cannot be stopped immediately. Only when the oil temperature at the end face seal drops below 80 degrees can the cooling water be stopped to avoid damaging the sealing parts. ?
3. running?
A if there is slight leakage after the centrifugal pump is started, it should be observed for a period of time. If the leakage does not decrease after 4 hours of continuous operation, the pump should be stopped for inspection. ?
B. The working pressure of the pump shall be stable, and the pressure fluctuation shall not be greater than 1kg/cm2. ?
C during the operation of the pump, evacuation should be avoided to avoid dry friction of the sealing surface and seal damage. ?
D. check the sealing condition frequently. In operation, when the leakage exceeds the standard, the heavy oil is not more than 5 drops/min and the light oil is not more than 10/ min. If there is still no improvement trend within 2-3 days, stop the pump bolts and check the sealing device. ?
1. Install the left part first; Installed on the sealing plate
2. Then install the right moving ring, and the sealing surfaces of the moving ring and the static ring should be clean.
3. Reinstall Ping Jian and impeller. Install the gasket and nut.
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