Valve maintenance knowledge:
Instructions on how to maintain the valve:
1、 Leakage at packing
Analyze production reasons:
1. Aging of packing;
2. Excessive force during operation;
3. The packing gland bolt is loose;
1. The aged and damaged sealing packing shall be replaced in time and placed one by one. The joint shall be 30 ° ~ 45 °;
2. Operate uniformly under normal stress, and do not add casing or lengthen the arm by other means;
3. Evenly tighten the bolts for pressing the packing gland;
2、 Leakage of sealing surface
1. The installation direction of the valve is inconsistent with the flow direction of the medium;
2. The valve is not closed in place;
3. The valve that has been closed for a long time scales on the sealing surface;
4. The sealing surface is slightly scratched;
5. The sealing surface is seriously damaged;
1. Pay attention to valve installation inspection;
2. Readjust the high-speed screws on the actuator and close them in place;
3. Open the valve to a slot to let the high-speed liquid wash away the scale;
4. High speed gasket for compensation;
5. Regrinding and high-speed gasket compensation;
3、 External leakage of flange connection
1. The tightening force of studs is uneven;
2. The gasket is aged and damaged;
3. The gasket material is inconsistent with the working condition medium requirements;
1. Tighten the bolts evenly again;
2. Replace the gasket;
3. Select the gasket materials and forms correctly according to the working conditions. If necessary, please contact the manufacturer to ask for help in material selection and type selection. When ordering, please specify the requirements in detail.
4、 Handle and hand wheel damaged
1. Incorrect use;
2. Loose solid parts;
3. The connection of handle, hand wheel and valve rod is damaged;
1. It is forbidden to use pipe tongs, extension levers, impact tools, etc;
2. Repair the supporting equipment at any time;
3. Repair at any time;
5、 Clamping of worm gear and worm drive
1. Dirt embedded, affecting lubrication;
2. Incorrect operation;
1. Remove the dirt, keep it clean and refuel regularly;
2. If the operation is found to be jammed and the torque is large, the operation cannot be continued, stop immediately and check thoroughly;
6、 Electric valve installation failure
1. Poor lubrication, foreign matters stuck in the valve, causing great damage to the torque side;
2. Motor failure;
1. Refuel the oil to make the oil pipe in good condition, and the packing shall be compacted properly. Remove the foreign matters in the valve in time and keep it clean;
2. The working time of the motor shall not exceed 15 minutes, and the power supply shall be normal to prevent the motor from getting damp.
Causes of valve leakage:
Valve leakage is very common in life and production. If it is light, it will cause waste or bring danger to life. If it is light, it will cause serious consequences, such as toxic, harmful, flammable, explosive and corrosive leakage in chemical industry, which will seriously threaten personal safety, property safety and environmental pollution. An electric butterfly valve depends on the external force to rotate and drive the opening and closing valves. A sealing device is designed, which is used to install a certain number of packing rings in the packing culvert to achieve the sealing effect. But what is the sealing condition? The leakage of packing is one of the most likely parts in the valve, but there are two reasons.
1、 One reason is corrosion.
The corrosion conditions include: 1. Natural oxidation corrosion of the valve stem. The surface of the valve stem packing is oxidized to produce ferric oxide (rust), which causes the valve stem to become thinner and cause leakage; 2. Leakage caused by chloride ion corrosion of asbestos packing; 3. Corrosion of graphite filler on stainless steel; 4. Corrosion of medium on the valve stem.
2、 Reasons for packing.
At present, the main uses of packing are: 1. Asbestos. Due to the chloride ion corrosion of asbestos materials on the valve rod, in addition, asbestos contains carcinogens, which is harmful to human health. The state has banned or reduced the use of local products; 2. Synthetic resin and synthetic fiber. Some of these products are limited in the scope of use, such as the use temperature of pure polytetrafluoroethylene It must be ≤ 150 ℃, filled with polytetrafluoroethylene ≤ 250 ℃, and polytetrafluoroethylene particle packing has poor compensation performance, which is only suitable for low-pressure valve, PTFE fiber, carbon fiber or both mixed packing, and the price is too high, which is not conducive to promotion; 3. Expanded graphite will cause serious electrochemical corrosion.
Procedures for valve maintenance:
General procedures for valve maintenance:
1. When removing the valve, use steel words on the valve and the flange connected with the valve, mark the maintenance number, and record the working medium, working pressure and working temperature of the valve, so as to select corresponding materials for repair.
2. The maintenance of valves shall be carried out in a clean environment. First, clean the outer surface of the valve, or blow with compressed air or clean with kerosene. But remember the nameplate and other marks. Check the appearance damage and make records. Then dismantle other parts of the valve, clean them with kerosene (do not use gasoline to clean them in case of fire), check the damage of other parts and make records.
3. Conduct strength test on valve body and bonnet. If it is a high-pressure valve, NDT shall be carried out, such as ultrasonic testing and X-ray testing.
4. Red lead powder can be used to inspect the sealing ring, and the consistency of valve seat and gate (disc) can be checked. Check whether the valve rod is bent, corroded or not, and how the thread is worn. Check the wear of the stem nut.
5. Deal with the problems found. Valve body repair welding defects. Weld or renew the sealing ring. Straighten or replace the stem. Repair all other parts that should be repaired; replace those that cannot be repaired.
6. Reassemble the valve. During assembly, the gasket and packing shall be replaced completely.
Common faults and treatment of valves
LD solenoid stuck:
The fit clearance between the slide sleeve and the valve core of the solenoid valve is very small (less than 0.008mm), which is generally a single assembly. When there are mechanical impurities or too little lubricating oil, it is easy to get stuck. The steel wire can be pierced through the small hole in the head to make it bounce back. The fundamental solution is to remove the solenoid valve, take out the valve core and valve core sleeve, and clean it with CCI4, so that the valve core can move flexibly in the valve sleeve. During disassembly, pay attention to the assembly sequence and external wiring position of each component, so as to reassemble and wire correctly, and check whether the fuel injection hole of the oil mist atomizer is blocked and whether the lubricating oil is sufficient. Steam solenoid valve
Ten precautions for valve maintenance:
(1) It is necessary to find out that the pressure of upstream and downstream pipes of the valve has been removed before disassembling.
(2) The non-metallic parts shall be taken out of the cleaning agent immediately after cleaning and shall not be soaked for a long time.
(3) During assembly, the bolts on the flange must be tightened symmetrically, step by step and evenly.
(4) The cleaning agent shall be compatible with rubber parts, plastic parts, metal parts and working medium (such as gas) in the valve. When the working medium is gas, the metal parts can be cleaned with gasoline (gb484-89). Clean non-metallic parts with pure water or alcohol.
(5) The disassembled individual parts can be washed by immersion. For the metal parts that have not been decomposed, clean and fine silk cloth impregnated with cleaning agent (to avoid fiber falling off and adhering to the parts) can be used for scrubbing. During cleaning, all grease, dirt, glue and dust adhering to the wall surface shall be removed.
(6) 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 the O-ring.
(7) After cleaning, it needs to be assembled after the cleaning agent on the washed wall evaporates (it can be wiped by the silk cloth without cleaning agent), but it can not be used for a long time, otherwise it will rust and be polluted by dust.
(8) New parts should also be cleaned before assembly.
(9) Lubricate with grease. The grease shall be compatible with the metal materials, rubber parts, plastic parts and working medium of the valve. When the working medium is gas, for example, te221 grease can be used. Apply a thin layer of grease on the surface of the installation groove of the seal, rubber seal and the sealing and friction surfaces of the valve rod.
Control valve bypass
Bypass shall be set in the following cases:
(1) Corrosive fluid;
(2) 8.2.3 occasions of severe wear of valve trim as mentioned in 2 of clause 8.2.3;
(3) Other important occasions, such as boiler feed water regulating valve.
Bypass may not be set in the following cases:
(1) Clean the fluid;
(2) When the nominal diameter DN > 80mm;
(3) When the LD control valve breaks down or is overhauled, it will not cause process accidents;
(4) Where bypass valve is not allowed or cannot be used in the process. For example: emergency interlock vent valve, slurry and easy to crystallize fluid, etc.
Hanson Wuxi Xinyi Automatic Machinery Factory& Wuxi Burket Industrial Co,.Ltd
Contact Person: Mr. Hanson