Valve daily maintenance and maintenance valve leakage five technical methods to deal with

Valve daily maintenance and maintenance valve leakage five technical methods to deal with

Valves are not only used in various industries, but also in different environments. Some valves in poor working environments are prone to problems. Because valves are important equipment, especially for some large valves, once there is a problem to repair or replacement is quite troublesome. So do a good job of daily maintenance and maintenance is particularly important. Let’s have a look at some little knowledge about valve maintenance.
Valves are not only used in various industries, but also in different use environments. Some valves in poor working environments are prone to problems. Because valves are important equipment, especially for some large valves, once there is a problem to repair or replacement is quite troublesome. So do a good job of daily maintenance and maintenance is particularly important. Let’s have a look at some little knowledge about valve maintenance.
1. Storage and daily inspection of valves
1, the valve should be stored in a dry and ventilated room, both ends of the pathway must be blocked.
2, long-term storage of the valve should be regularly checked, dirt, and rust oil coated on the processing surface.
3. After installation, regular inspection should be carried out. The main inspection items are:
(1) Sealing surface wear.
(2) trapezoidal thread wear of stem and stem nut.
(3) whether the packing is outdated and invalid, if damaged, it should be replaced in time.
(4) After valve maintenance and assembly, sealing performance test should be carried out.
Two, valve grease maintenance work
The professional maintenance of the valve before welding and after production plays a vital role in the production and operation of the valve. The correct and orderly and effective maintenance will protect the valve, make the valve function normally and extend the service life of the valve. Valve maintenance may seem simple, but it is not. There are often overlooked aspects of work.
Valve grease, often ignore the problem of grease amount. After grease filling, the operator selects the connection between valve and grease filling, and then carries out grease filling. There are two situations: on the one hand, the amount of grease is less than enough, and the sealing surface is worn faster because of the lack of lubricant. On the other hand, excessive fat injection causes waste. There is no accurate calculation of the valve seal capacity according to the valve type class. You can calculate the sealing capacity by valve size and category, and then inject a reasonable amount of grease.
Second, valve grease, often ignore the problem of pressure. During the operation of lipid injection, the lipid injection pressure has a regular peak-valley change. The pressure is too low, the seal leakage or failure pressure is too high, the grease injection port is blocked, the grease in the seal is hardened, or the sealing ring is locked with the valve ball and valve plate. Usually when the grease injection pressure is too low, the injected grease flows into the bottom of the valve chamber, generally occurring in small gate valves. While the grease injection pressure is too high, on the one hand, check the grease nozzle, if the grease hole is blocked, replace it; On the other hand, lipid hardening, cleaning fluid should be used to repeatedly soften the failed seal grease, and inject new grease replacement. In addition, seal type and seal material, also affect the injection pressure, different seal forms have different injection pressure, in general, the hard seal injection pressure is higher than the soft seal.
Do the above work, I believe to extend the service life of the valve is very helpful, but also can reduce a lot of unnecessary trouble.
Five technical methods to deal with valve leakage
A valve body and valve cover leakage:
The reason:
1. Casting quality of cast iron is not high, and there are trachoma, loose organization, slag inclusion and other defects on the valve body and valve cover body
2. Freezing crack;
3. Poor welding, slag inclusion, unwelded, stress cracks and other defects;
4. Cast iron valve damaged by heavy object impact.
Maintenance Methods:
1. Improve casting quality and conduct strength test in strict accordance with regulations before installation;
2. For valves whose temperature is 0¡ã or below, heat preservation or mixing shall be carried out, and water shall be removed from valves that are out of service
3. The welds of the body and valve cover composed of welding shall be carried out according to the relevant welding operation rules, and the flaw detection and strength test shall be carried out after welding;
4. It is forbidden to push and put heavy objects on the valve. It is not allowed to hit the cast iron and non-metal valve with a hammer.
Two, the leakage of packing (leakage of the valve, the proportion of packing is relatively large)
The reason:
1. Packing selection is wrong, not resistant to medium corrosion, not resistant to high pressure or vacuum valve, high temperature or low temperature use;
2. The packing is not installed correctly, there are some defects such as replacing the small with the large, the helix winding joint is not good, the upper tight and the lower loose.
3. The packing has aged and lost elasticity beyond its service life
4. Stem precision is not high, bending, corrosion, wear and other defects
5. The number of packing rings is insufficient, the gland is not pressed;
6. Gland, bolts, and other parts are damaged, so that the gland can not be compressed;
7. Improper operation, excessive force, etc.;
8. Gland skew, gland and stem gap is too small or too large, resulting in stem wear, packing damage.
Maintenance Methods:
1. The material and type of packing should be selected according to the working conditions;
2. According to the relevant provisions of the correct installation packing, the root of the pan should be placed and pressed round by turn, the joint should be 30¡æ or 45¡æ;
3. The packing with too long service life, aging and damage should be replaced in time;
4. Valve stem bending, wear should be straightened, repair, serious damage should be replaced in time;
5. The packing should be installed according to the prescribed number of turns, the gland should be symmetrical and evenly tightened, the pressure sleeve should have more than 5mm pretightening gap;
6. The damaged gland, bolts and other parts should be repaired or replaced in time;
7. Should comply with the operating procedures, except the impact of the handwheel, with uniform speed normal force operation;
8. The gland bolt should be tightened evenly and symmetrically. If the gap between gland and valve stem is too small, the gap should be appropriately increased. If the gap between gland and stem is too large, it should be replaced.
Three. Leakage of sealing surface
The reason:
1, sealing surface grinding uneven, can not form a close line;
2, the connection between the stem and the closing part at the center of the suspension, is not straight or wear;
3, the valve stem bending or assembly is not correct, so that the closing part is skewed or not in the middle;
4. Improper selection of sealing surface material quality or not selection of valve according to working conditions
Maintenance Methods:
1. Correctly select the material and type of bouncing gasket according to the working conditions;
2, careful adjustment, smooth operation;
3, should be evenly and symmetrically screw the bolt, if necessary, should use torque wrench, preload should meet the requirements, not too large or small. Flange and thread joints should have a certain preload clearance;
4, the gasket assembly should meet the center, the force is uniform, gasket is not allowed to lap and use double gasket;
5, static sealing surface corrosion, damage processing, processing quality is not high, should be repaired, grinding, coloring inspection, make the static sealing surface meet the relevant requirements;
6. When installing the gasket, attention should be paid to cleaning, sealing surface should be kerosene clear, and the gasket should not fall to the ground.
Four, sealing ring connection leakage
The reason:
1, sealing ring rolling is not strict
2, sealing ring and body welding, surfacing quality is poor;
3, sealing ring connection thread, screw, pressure ring loose;
4. The sealing ring is connected and corroded.
Maintenance Methods:
1. The leakage in the sealed rolling place should be fixed by injecting adhesive and then rolling;
2. The sealing ring should be repaired according to the welding specification. When the surfacing cannot be repaired, the original surfacing and processing should be carried out;
3. Remove the screws, clean the pressure ring, replace the damaged parts, grind the sealing and connecting seat close surface, and assemble again. The parts with large corrosion damage can be repaired by welding, bonding and other methods;
4. The sealing ring connection surface is corroded, which can be repaired by grinding and bonding, and the sealing ring should be replaced when it cannot be repaired.
5. Leakage caused by falling off of closing parts:
The reason:
1, poor operation, so that the closing piece is stuck or more than the dead point, the connection is damaged and broken;
2, close the connection is not firm, loose and fall off;
3, the choice of connection material is not right, can not stand the corrosion of the medium and mechanical wear.
Maintenance Methods:
1, correct operation, close the valve can not force too much, open the valve can not exceed the dead point, the valve is fully opened, the handwheel should reverse a little;
2. The connection between the closing part and the valve stem should be firm, and the thread connection should have a backstop part;
3. Fasteners used for connecting the closing parts and the valve stem should withstand the corrosion of the medium, and have certain mechanical strength and wear resistance.