Limit check of ball valves
When the valve is operating normally, check the valve limit online. For the opening and closing limit reference marks made during the installation stage, you can directly observe whether the limit marks correspond; for ball valves with valve position observation holes, you can directly observe whether the limit marks correspond to the opening position of the valve. Open the valve position observation hole to check whether the valve position is correct; for valves with unlimited position reference marks and no valve position observation hole, the valve can be placed in the fully closed or fully open position, and the valve end cover can be opened to check the direction of the keyway opening. Generally, when the valve is in the fully open position, the keyway opening direction is parallel to the valve connecting pipeline; when the valve is in the fully closed position, the keyway opening direction is perpendicular to the valve connecting pipeline.
 
Limit adjustment of ball valves
When the valve switching operating torque is too great or cannot be operated during operation, or the internal leakage in the closed position is serious, it is necessary to check the operation of the actuator and whether the valve limit is accurate. If the limit is inaccurate, further inspection is required for the valve limit.

Method 1: For valves that have been marked with a closing limit mark, set the valve in the fully closed position, loosen the closing limit bolt of the valve gearbox, adjust the valve opening to the position of the closing limit mark, and tighten the closing limit bolt.

Method 2: For valves that have not been marked with a closing limit mark, set the valve in the fully closed position, open the gearbox end cover, loosen the valve gearbox closing limit bolt, and adjust the valve opening to the direction of the valve stem keyway opening to where the valve is. In the vertical position of the pipeline direction, tighten the closing limit bolt and make a full closing limit mark.
 
Method 3:
(1) Place the valve in the fully closed position, slowly open the valve drain nozzle, and gradually evacuate the gas in the valve cavity until the drain nozzle is fully open.
(2) If the leaked gas from the sewage nozzle continues without significant weakening, grease maintenance can be performed on the high-pressure side valve seat to control leakage and establish conditions for further treatment.
(3) Keep the drain nozzle open and loosen the valve gearbox closing limit bolt.
(4) Rotate the valve within ±5° of the fully closed position, and slowly adjust the opening and closing of the valve.
(5) In the slow adjustment process, listen to the exhaust volume of the sewage nozzle until there is no exhaust sound or the exhaust volume is minimal. The position at this time is the best limit for the valve to close. If the sewage nozzle still leaks, the internal leakage of the valve should be dealt with.
(6) Tighten the gearbox, close the limit bolt, and close the drain nozzle.
 
Internal leakage treatment of ball valves
After it is judged that the internal leakage of the valve is not caused by incorrect valve limit, indicating that the surface of the valve core is scratched or the soft seal of the valve seat is defective, then the following steps are performed to eliminate or reduce internal leakage:
(1) Place the ball valve in the fully closed position.
(2) Unscrew the protective cap of the grease nozzle. If it cannot be tightened by hand, use two explosion-proof wrenches. The unscrewed safety cap must be placed in the designated position and must not be left randomly. When tightening the safety cap, the operator should not face the grease nozzle to avoid danger.
(3) Clean the dirt on the grease nozzle, then connect the grease gun loaded with grease to the valve grease nozzle, and turn on the switch on the connection joint to make the grease injection channel unobstructed.
(4) Start injecting grease and observe the changes in injection pressure. The injection pressure should not exceed 3000 PSI. The amount of grease injected into each grease nozzle of the valve is equal. During the first maintenance, the total amount of grease injected into the valve should be 100% of the theoretical volume of the valve sealing system. After the first maintenance, the amount of grease injected into the valve should be 100% of the theoretical volume of the valve sealing system. 1/4 of the volume after the first time.
(5) After the grease injection is completed, release the pressure in the grease gun and remove the connecting joint. When taking out the connecting joint, the operator should not face the grease nozzle to avoid danger.
(6) After the grease injection is completed, clean the grease nozzle with a rag and tighten the safety cap to ensure that the grease nozzle is clean and prevents corrosion.
(7) Open and close the valve 1 to 2 times. The angle of the switching stroke is not less than 30°, and fully lubricates the valve seat and sealing surface. If the internal leakage cannot be eliminated by injecting sealing grease once, it can be injected repeatedly to deal with the internal leakage.
 
If the valve grease channel is blocked, the sealing grease is hardened, or the sealing system has a lot of impurities, cleaning fluid should be injected into the valve seat sealing system.
(1) Use a manual grease gun or a pneumatic grease machine to inject the specified amount of valve cleaning fluid evenly and slowly into each grease nozzle. The cleaning fluid should be injected slowly, and a manual grease gun should be used as much as possible. However, in individual cases, the sealing channel may be blocked. At this time, a pneumatic grease injection machine should be used for rapid injection to make the valve sealing channel unblocked.
(2) After the cleaning fluid is injected, the valve should be opened and closed as much as possible 5 to 10 times, then the specified amount of valve grease or sealing grease should be injected, and the valve should be opened and closed 1 to 2 times according to the production conditions.
If the valve still leaks internally, it means that the valve seat or ball has been seriously damaged, and the valve seat needs to be replaced or offline maintenance is required.