1.?Basic knowledge of water pump mechanical seals:?
1. Basic concepts of centrifugal pump mechanical seals:?
Mechanical seals refer to at least one pair of A device that prevents fluid leakage by keeping the end faces perpendicular to the axis of rotation and sliding relative to each other under the action of fluid pressure, the elastic force (or magnetic force) of the compensation mechanism, and the cooperation of auxiliary seals. If the auxiliary seal of the compensation ring is a metal bellows, it is called a bellows mechanical seal. ?
2. The composition of mechanical seal: ?
There are mainly the following four types of components. a. Main seals: moving ring and static ring. b. Auxiliary seal: sealing ring. c. Pressing parts: spring, push ring. d. Transmission parts: spring pan seat and key or fixing screw?
2. What should be paid attention to when working on machine seal:?
1. Precautions during installation?
a. Pay great attention to avoid installation deviations during installation
(1) Tightening the gland should be done after the coupling is aligned, and the bolts should be evenly supported to prevent the end face of the gland from Deflection, check each point with a feeler gauge, the error is not greater than 0.05 mm.
(2) Check the matching gap (i.e. concentricity) between the gland and the outer diameter of the shaft or sleeve. It should be uniform all around. Use a feeler gauge to check that the tolerance of each point is not greater than 0.01 mm. ?
b. The spring compression amount must be carried out according to regulations. It is not allowed to be too large or too small. The required error is 2.00 mm. Excessive pressure will increase the end face specific pressure and accelerate end face wear. If it is too small, the specific pressure will be insufficient and the sealing effect will not be achieved. ?
c. After the moving ring is installed, it must be able to move flexibly on the shaft. The moving ring should be able to spring back automatically after being pressed against the spring. ?
2. Precautions when disassembling?
a. Be careful when disassembling the mechanical seal. It is strictly forbidden to use hand hammers and flat shovels to avoid damaging the sealing components. A pair of steel wire hooks can be made, extending into the gap of the transmission seat in the direction of self-financing and loss, and pulling out the sealing device. If it cannot be disassembled due to scaling, it should be cleaned before disassembly. ?
b. If mechanical seals are used at both ends of the pump, take care of each other during assembly and disassembly to avoid focusing on one at the expense of the other. ?
c. For a mechanical seal that has been operated, if the gland is loose and the seal moves, the dynamic and stationary ring parts must be replaced and should not be re-tightened for continued use. Because after such movement, the original running trajectory of the friction pair will change, and the sealing of the contact surface will be easily destroyed. ?
3. Issues with normal operation and maintenance of machine seals: ?
1. Preparations and precautions before starting?
a. Comprehensive inspection Whether the mechanical seal, ancillary devices and pipelines are installed completely and meet the technical requirements. ?
b. Conduct a static pressure test before starting the mechanical seal to check whether there is leakage in the mechanical seal. If there is a large amount of leakage, the cause should be identified and eliminated. If it still doesn't work, it should be disassembled, inspected and reinstalled. Generally, the static pressure test pressure is 2~3 kg/cm2. ?
c. Turn the pump according to the rotation direction and check whether it is light and even. If turning is difficult or does not move, check whether the assembly dimensions are wrong and whether the installation is reasonable. ?
2. Installation and shutdown?
a. The sealing chamber should be filled with liquid before starting. When transporting solidified media, steam should be used to heat the sealed chamber to melt the media. The car must be cranked before starting to prevent the soft ring from breaking due to sudden start. ?
b. For mechanical seals that use an oil sealing system outside the pump, the oil sealing system should be started first. After parking, stop the oil sealing system last. ?
c. After the hot oil pump is stopped, the cooling water in the oil seal chamber and the end face seal cannot be stopped immediately. The cooling water can only be stopped when the oil temperature at the end face seal drops below 80 degrees to avoid damage. Seal parts. ?
3. Operation?
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 operating pressure of the pump should be stable, with pressure fluctuations not greater than 1 kg/cm2.
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c. When the pump is in operation, evacuation should be avoided to avoid dry friction on the sealing surface and seal damage. ?
d. The sealing condition should be checked frequently. During operation, when the leakage exceeds the standard, the heavy oil should not exceed 5 drops/min, and the light oil should not exceed 10/min. If there is still no improvement within 2-3 days, the pump should be stopped and the sealing device should be checked. ?
1. Install the left part first; install it on the sealing plate
2. Then install the moving ring on the right. The sealing surfaces of the moving ring and the static ring must be clean
3. Reinstall the flat key and impeller. Install the gaskets and nuts
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