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Routine maintenance of ball valves
Ball valves have a long service life and maintenance free period, which will depend on the following factors: normal operating conditions, maintaining a harmonious temperature/pressure ratio, and reasonable corrosion data
When the ball valve is closed, there is still pressurized fluid inside the valve body
Before maintenance: relieve the pipeline pressure and keep the valve in the open position; Disconnect the power or air source; Detach the actuator from the bracket
Before disassembly and disassembly, it is necessary to verify that the upstream and downstream pipes of the ball valve have been depressurized
During disassembly and reassembly, care must be taken to prevent damage to the sealing surface of parts, especially non-metallic parts. Special tools should be used when taking out O-rings
During assembly, the bolts on the flange must be tightened symmetrically, gradually, and evenly
The cleaning agent should be compatible with the rubber parts, plastic parts, metal parts, and working media (such as gas) in the ball valve. When the working medium is gas, gasoline (GB484-89) can be used to clean metal parts. Clean non-metallic parts with purified water or alcohol
After cleaning, non-metallic parts should be taken out of the cleaning agent immediately and should not be soaked for a long time
After cleaning, it is necessary to wait for the volatilization of the cleaning agent on the cleaned wall surface (it can be wiped with a silk cloth that is not soaked in the cleaning agent) for assembly, but it must not be left for a long time, otherwise it will rust and be contaminated by dust
New parts also need to be cleaned before assembly
During assembly, it is not allowed to have metal debris, fibers, grease (except for those specified for use), dust, other impurities, foreign matters, etc. contaminate, adhere to or stay on the surface of the parts or enter the inner cavity. If there is slight leakage at the filler, the valve rod nut must be locked again.
Note: Do not lock it too tightly. Usually, lock it for another 1/4 to 1 turn, and the leakage will stop.
A) Disassembly
Place the valve in the half open position to flush and remove potentially hazardous substances inside and outside the valve body.
Close the ball valve, remove the connecting bolts and nuts on both flanges, and then completely remove the valve from the pipeline.
Disassemble the drive unit in sequence - actuator, connecting bracket, lock washer, valve stem nut, butterfly spring piece, Glenn, wear plate, and valve stem packing.
Remove the body cover connecting bolts and nuts, separate the valve cover from the valve body, and remove the valve cover gasket.
Confirm that the valve ball is in the "off" position, which can easily be taken out of the valve body, and then take out the valve seat.
Gently push the valve rod downward through the middle hole of the valve body until it is completely removed, and then take out the O-ring and the lower packing of the valve rod.
Note: Please operate carefully to avoid scratching the valve stem surface and the sealing part of the valve body stuffing box.
B) Reassembly
Clean and inspect the removed parts, and it is strongly recommended to replace the valve seat, bonnet gasket, and other seals with a spare parts kit.
Assemble in the reverse order of disassembly.
Tighten the flange connecting bolts crosswise with the specified torque.
Tighten the valve stem nut with the specified torque.
After installing the actuator, input the corresponding signal to drive the valve core to rotate through the rotating valve rod, making the valve open and closed.
If possible, please conduct a pressure seal test and performance test on the valve according to relevant standards before reinstalling the pipeline.
1. Principle
The opening and closing member of a ball valve is a ball that rotates around the center line of the valve body to achieve opening and closing.
2. Applicable place
Places on low pressure and small diameter pipelines that are used to cut off water flow and change the distribution of water flow or require rapid opening and closing.
3. Features
1) Low flow resistance;
2) Simple structure;
3) Small size and light weight;
4) The sealing surface material of the ball valve is plastic, with good sealing performance;
5) Easy to operate, fast to open and close, and convenient for remote control;
6) Convenient maintenance, sealing rings are generally movable, and easy to disassemble and replace;
7) When fully open or fully closed, the sealing surfaces of the ball and valve seat are isolated from the medium, and the passage of the medium will not cause erosion of the valve sealing surface.
4. Classification
1) According to their working principles, commonly used ball valves are divided into floating ball valves, fixed ball valves, and lift rod ball valves.
2) Ball valves can be divided into straight-through, three-way, and right-angle types according to their channel positions. The latter two ball valves are used to distribute media and change the flow direction of the media.
5. Key points of construction and installation
1) The installation position, height, inlet and outlet directions must meet the design requirements, and the connection should be firm and tight.
2) The handle of various manual valves installed on insulated pipes shall not be downward.
3) Visual inspection must be conducted before valve installation. The nameplate of the valve should comply with the current national standard "General Purpose Valve Signs" GB 12220. For valves with a working pressure greater than 1.0 MPa and having a cutoff effect on the main pipe, strength and tightness tests should be conducted before installation, and they can only be used after passing the tests. During the strength test, the test pressure shall be 1.5 times the nominal pressure, and the duration shall not be less than 5min. The valve shell and filler shall be free of leakage, which is considered qualified. During the tightness test, the test pressure shall be 1.1 times the nominal pressure; The test pressure during the duration of the test shall comply with the requirements of GB 50243 standard, and the valve flap sealing surface shall be qualified if there is no leakage.
4) Install sealing gasket between valve flange and pipeline flange according to pipeline design requirements.
5) The ball valve with transmission mechanism shall be installed according to the product instructions.
