- Leakage of packing in high and medium pressure butterfly valves
The valve stem and packing will form a state of motion between each other, which will be reflected in the use of high and medium pressure butterfly valves. The more times the high and medium pressure butterfly valve opens and closes, the more movement it will have. Coupled with the effects of temperature, pressure, etc., the possibility of packing leakage in high and medium pressure butterfly valves will be greatly increased. During this period, the pressure of the packing will gradually decrease, resulting in aging and elasticity no longer exists. The pressure medium will leak out from the contact gap between the packing and the valve stem. If this problem is not properly solved, as time goes by, it will cause the problem of seasoning blowing away and the valve stem coming out of the groove, making the leakage surface wider. Come bigger.
- Leakage of flange
There are often more than one reasons for flange leakage, such as insufficient pressing force of the sealing gasket, roughness of the joint surface differing from the requirements by a certain distance, deformation of the gasket, etc., which results in the sealing gasket and flange not being fully adequate. A gap will appear due to contact, and leakage will occur. At the same time, the causes of loose flange surface sealing include bolt deformation or elongation, gasket aging, reduced resilience, cracks, etc., which can also cause leakage. In addition, human factors are also aspects that require special attention for flange leakage. In addition, the valve body will also cause leakage problems. Due to space limitations, we will not go into details here.
Methods to deal with external leakage of high and medium pressure butterfly valves in power stations
- Pressure plugging treatment for leakage in packing chamber
There are many ways to deal with external leakage of high and medium pressure butterfly valves in power stations. Among them, the safer one is the injection pressure leakage plugging technology, which has been concluded in detail. This method uses a special clamp and a hydraulic injection tool to inject the sealant into the sealing cavity formed by the clamp and part of the outer surface of the leakage area. The effect of remedying the leakage defect is relatively good and the time taken is relatively short. When the pressure of the injection exceeds the pressure of the leaking medium, the leakage will be forcibly stopped, causing the injection to transform from a plastic body into an elastomer. At this time, the sealing structure has a certain elasticity, and there is also a certain working sealing specific pressure. Secondary A seal finally forms, which definitely adds to the good sealing. The following two types of sealing injections are most commonly used and promoted in my country today: (1) Heat-curing sealing injections. The use of this injection agent needs to meet certain conditions, that is, temperature. When the temperature reaches a certain level, the injection agent will be elastomer, and generally it will be solid. (2) Non-thermal curing sealant. Its application range is very wide, it can be operated under various temperature conditions, it can also be installed in high-pressure injection guns, its injectability and filling performance are relatively good, and the switching function of medium and medium pressure butterfly valves can also be well preserved. When the wall thickness of the stuffing box of the high and medium pressure butterfly valve is more than 8 mm, the injection pressure can be used to solve the leakage problem by directly setting injection holes on the wall of the stuffing box of the high and medium pressure butterfly valve. The sealing cavity is the stuffing box of the high and medium pressure butterfly valve itself. Sealing compound can perform the same function as filler. Find a suitable position to drill a drill bit with a diameter of 10.5 mm or 8.7 mm in the outer wall of the high and medium pressure butterfly valve stuffing box. What needs to be emphasized here is that this hole must not be drilled through. The distance left should be between 1-3 mm. Pull out the drill bit and tap with an M12 or MIO tap. When the work is completed, tighten the special plug valve for injection. The valve should be in an open state, and then select a long rod drill bit. The diameter 3 should be selected. mm, the purpose is to drill through the remaining wall of the stuffing box of the high and medium pressure butterfly valve, and the leakage will be ejected in the direction of the drill bit. There is a certain degree of danger when drilling, mainly because excessive temperature or pressure or the spraying out of toxic substances will cause certain harm to the workers, ranging from injury to people to life-threatening in severe cases. , so this must not be ignored. Using a baffle before drilling is a better control method.
- Pressure plugging treatment of flange leakage Copper wire containment method
The scope of application of this method is that the gap between the two flanges is small, the gap amount is uniform, and the leakage medium pressure is low. The special injection joint shadow of the bolt is placed on the removed bolt. The two are lower and should be larger than two. When installing the injection joint, do not tighten all the nuts, but loosen one. After installing the injection joint, tighten the nuts immediately and install other injection joints. What needs to be emphasized here is that the required joint nuts cannot be installed at the same time. Loosen, because it will reduce the sealing specific pressure on the gasket, increase the leakage, and in serious cases, the leaked material will blow away the gasket. If this happens, it will be difficult to have remedial measures, and the loss will be immeasurable.
- Pressure plugging treatment for valve body leakage
1. Bonding method
If it is a blistered area with small pressure medium and small leakage, you can first polish the area around the leakage point to a metallic luster, then use a tapered pin to align the leakage point and drive it in with appropriate force, mainly to reduce leakage or temporarily seal it. Blocking. The adhesive cures relatively quickly. This feature can be used to apply adhesive around the pin to form a new solid sealing structure, which can prevent leakage to a certain extent. If the medium pressure is high and the leakage is large, the sealing operation can be carried out by using a top-pressure tool. During the operation, the top-pressure mechanism is fixed on one side of the high- and medium-pressure butterfly valve, and the high-speed top pressure screw is used to make the axial direction of the top-pressure screw. Face the leakage point, rotate the pressure screw, and use the rivet at the end of the pressure screw to press the leakage site tightly. This is also an effective way to stop leakage. If the top of the rivet is smaller than the area of the leakage point, a soft metal sheet can be placed under the rivet. When the leakage stops, the metal surface around the leakage point should be cleaned in time.
2. Welding method
If the pressure of the leaking medium in the valve body is low and the leakage is small, a nut with an inner diameter more than twice as large as the leakage point can be used to allow the leaking medium to flow out of the nut. Weld the nut to the valve body and match it with a nut. For bolts with the same specifications as the nut, place a rubber pad or asbestos pad at the bottom of the nut, wrap raw tape around the top of the bolt and screw it into the nut, which can effectively reduce leakage. If the leakage medium pressure of the valve body is high and the leakage volume is large, then the flow welding method is a better method. First use an iron plate with a round hole in the middle, weld an isolation valve with a diameter equivalent to the round hole on the round hole of the iron plate, open the isolation valve, align the center hole of the iron plate with the leakage point and fit it to the valve body. Let the leaking medium flow out through the center hole of the iron plate and the isolation valve. For situations where the fitting surface is not good, you can place a rubber or asbestos pad on the fitting surface, then weld the iron plate around the valve body, and then close the isolation valve. This will achieve a better sealing effect.