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The maintenance steps for valves that are in operation are as follows:
1. Cleaning
A lot of dust, oil, and medium residues are easy to accumulate on surfaces of a valve, trapezoidal threads on valve stems and stems' nuts, sliding parts of the valve stem's nut and bracket, gears, worm gears and other components, which will cause wear and corrosion to the valve. Therefore, it is very important to keep the exterior and moving parts of valves clean and to protect the integrity of the valve paint. The brush and compressed air are suitable for sweeping or blowing the valve. Dirt on and between trapezoidal threads should be cleaned by rags. Oil and residues on the valve should be cleaned with steam purging, or even use copper wire to brush till the machined surface, the matching surface shows metallic luster and the painted surface shows the true color of the paint. The steam trap valve should be inspected by a dedicated person at least once per shift. Open the plug which is at the bottom of the flush valve and steam strap valve to wash, or disassemble and flushed them regularly to avoid clogging the valve with the dirty matter.
 
2. Lubrication of valves
The trapezoidal thread of valves, sliding parts of the valve stem's nut and bracket, bearing parts, meshing parts of gears and worm gears, worms and other coordinated movable parts all require good lubrication to reduce mutual friction and avoid mutual wear. Some parts are specially equipped with oil cups or nozzles. If they are damaged or lost in operation, they should be repaired and replaced; the oil circuit should be smooth. Lubricated parts should be regularly lubricated according to specific conditions. For valves that are frequently opened or of high temperature should be lubricated once every other week to a month. Valves with infrequent openings or low temperature may have a longer lubricating cycle. Lubricants include organic oil, grease, molybdenum disulfide, and graphite. Valves with high temperatures shouldn't be lubricated by oil and grease, because they will be melted and lost due to high temperatures. Add molybdenum disulfide and friction graphite powder. As for the exposed parts that need to be lubricated, such as trapezoidal threads, gears, etc., if grease is used, it is easy to be contaminated by dust, while molybdenum disulfide and graphite powder are good for lubrication, which has a better lubricating effect than that of grease. Graphite powder is not easy to apply directly, which can be mixed with a little oil or water to form a paste. The plug valve sealed by grease should be filled with oil according to the specified time. Otherwise, it is easy to wear and leak.
 
3. Maintenance of valves
Various valve parts should be complete for valves that are in operation. Bolts used for flanges and brackets are indispensable. Threads should be in a good condition. If the nuts on the handwheel are loose, they should be tightened in time, so that the connecting part won't be worn or handwheels and nameplates won't be lost. Adjustable wrenches can't be replaced with handwheels if they are lost, which should be replaced with new ones. A protective cover should be provided for valve stems when valves are located in places where they can be contaminated by rain, snow, dust, and sand easily. It's forbidden to hit, stand or put heavy objects on valves when they are in operation, especially for non-metal valves and cast iron valves.
 
The daily maintenance of electric devices is generally not less than once a month. The appearance of electric devices should be cleaned and no dust. The electric device should not be contaminated by air, water, and oil. The electric device should be well sealed. The electric device should have a good lubricating condition. It should be lubricated on time and according to regulations. Apply grease for the stem's nut. The electrical part should be intact; avoid moisture and dust. If the electric device is damp, you need to use a 500V megohmmeter to measure the insulation resistance between all current-carrying parts and the shell, and the value should not be less than 0.38 megohm. Otherwise, the relevant parts should be dried. The indicator light should display correctly, and there is no phase loss, short circuit a broken circuit. The working state of the electric device should be normal, and its on-off key should be flexible.
 
The daily maintenance of the pneumatic device is usually not less than once a month. The pneumatic device should have a clean appearance and it should not be contaminated by air, water, and oil. The pneumatic device should be well sealed. Each sealing surface and point should be complete, firm, tight, and undamaged. The mechanism operated manually should be well lubricated, and can be opened and closed flexibly. Air joints of the inlet and outlet of the cylinder are not allowed to be damaged. Each part of the cylinder and air piping system should be carefully inspected, and there should be no leakage that affects the performance. Dents are not allowed for pipes. The annunciator should be in a good condition, and its indicator light should be intact. The annunciator should be in a good condition, and its indicator light should be intact. The valve on the pneumatic device should be intact, free from leakage, of flexible opening and closing as well as smooth airflow. The entire pneumatic device should be in a normal working state, with flexible opening and closing.
 

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