Corporate News
Leakage of high and medium pressure butterfly valves is a common problem, but in some important system equipment, leakage of high and medium pressure butterfly valves can affect industrial production and, in severe cases, endanger the safety of people's lives and property. The high and medium pressure butterfly valves in power plants are connected to the main and auxiliary equipment and systems, and their importance is self-evident. The following is an analysis of several treatment methods for leakage of high and medium pressure butterfly valves in power plants:
1、 Leakage of high and medium pressure butterfly valve packing
The valve stem and packing will form a motion state between each other, which will be reflected in the use process of high and medium pressure butterfly valves. The more times the high and medium pressure butterfly valve is opened and closed, the more movement it will have. In addition, the effects of temperature, pressure, and other factors will significantly increase the possibility of leakage of the high and medium pressure butterfly valve packing. During this period, the pressure of the packing will gradually decrease, leading to aging and the loss of elasticity. And the pressure medium will leak out from the contact gap between the packing and the valve stem. If this problem is not properly solved, over time, it will form the problem of seasoning blowing away and the valve stem detaching from the groove, causing the leakage surface to become larger and larger.
2、 Leakage of flange
The reasons for flange leakage often lie in more than one aspect, such as insufficient compression force of the sealing gasket, a certain distance difference between the roughness of the joint surface and the requirements, gasket deformation, etc., resulting in incomplete contact between the sealing gasket and the flange, resulting in gaps and leakage. At the same time, the reasons for the loose sealing of the flange surface include bolt deformation or elongation, gasket aging, decreased rebound force, cracking, etc., which can also cause leakage. In addition, human factors are also an aspect of flange leakage that requires special attention. In addition, the valve body may also experience leakage due to space limitations, so we will not elaborate on it here.
3、 Method for Handling External Leakage of High and Medium Pressure Butterfly Valves in Power Plants
Pressure plugging treatment for leakage in the packing chamber
There are also many methods for dealing with external leakage of high and medium pressure butterfly valves in power plants, among which the injection type pressure plugging technology has higher safety, which has been concluded in detail. This method uses special fixtures and hydraulic injection tools to inject sealant into the sealing cavity formed by the external surface of the fixture and the leaking part, which has a good effect on repairing the leakage defect and takes a relatively short time. When the pressure of the injection exceeds the pressure of the leaking medium, it will forcibly stop the leakage, causing the injection to transform from a plastic body to an elastic body. At this time, the sealing structure has a certain elasticity, and there is also a certain working sealing pressure ratio. The secondary sealing is eventually formed, which undoubtedly increases good sealing performance. The following two types of sealing injection agents are widely used and promoted in China today: (1) Thermal curing sealing injection agents. The use of this injection agent needs to meet certain conditions, that is, temperature. When the temperature reaches a certain level, the injection agent is an elastic body, and generally it is a solid. (2) Non thermal curing sealing agent. It has a wide range of applications and can be operated under various temperature conditions. It can also be installed in high-pressure injection guns, with good injection and filling properties. The switching function of high and medium pressure butterfly valves can also be well preserved. When the wall thickness of the packing box of the high and medium pressure butterfly valve is above 8mm, the use of injection pressure can be used to solve the leakage problem. Injection holes can be directly set on the wall surface of the packing box of the high and medium pressure butterfly valve, and the sealing chamber is the packing box itself of the high and medium pressure butterfly valve. The sealing injection can play the same role as the filling material. Find a suitable location to drill a hole with a diameter of 10.5mm or 8.7mm on the outer wall of the high and medium pressure butterfly valve packing box. It should be emphasized that this hole should not be drilled through, and the distance left should be between 1-3mm. Remove the drill bit and tap it with an M12 or MIO tap. After this work is completed, tighten the special plug valve for injection. The valve should be in the open state, and then select a long rod drill bit, The choice should be a diameter of 3mm, with the aim of drilling through the remaining high and medium pressure butterfly valve packing box wall, and leakage will spray out along the direction of the drill bit. There is a certain degree of danger when drilling, mainly because excessive temperature or pressure, or the spraying of toxic substances, can cause certain harm to workers. It can be mild to personal injury, and severe to life safety. Therefore, this cannot be ignored. Using a baffle before drilling is a good control method.
Copper wire containment method for flange leakage under pressure
The scope of application of this method is to plug under pressure when the gap between the two flanges is small, the gap amount is uniform, and the pressure of the leakage medium is low. The bolt special injection joint should be placed on the removed bolt, and the two are lower, which should be greater than two. When installing the injection joint, do not tighten all the nuts, but loosen one. After installing the injection joint, immediately tighten the nuts and install other injection joints. It should be emphasized that the required joint nuts cannot be loosened at the same time, as it will reduce the sealing pressure on the gasket, increase the leakage, and in severe cases, the leakage material will also blow away the gasket. If this situation really occurs, it is difficult to take remedial measures, The losses are also incalculable.
Pressure plugging treatment for valve body leakage
1. Bonding method
If it is a pressure medium or a sand hole with small leakage, the area around the leakage point can be polished to a metallic luster first, and then pointed at the leakage point with a tapered pin and inserted with appropriate force, mainly to reduce leakage or temporarily seal it. The curing speed of the adhesive is relatively fast, which can be used to coat the adhesive around the pin to form a new solid sealing structure, which can produce a leak proof effect to a certain extent. If the medium pressure is high and there is a large amount of leakage, sealing operations can be carried out by using top pressure tools. 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 top pressure screw, and use the rivets at the end of the top pressure screw to tightly press on the leakage site, which is also an effective way to prevent 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. After the leakage stops, the metal surface around the leakage point should be cleaned in a timely manner.
2. Welding method
If the pressure of the leakage medium in the valve body is low and the leakage amount is small, a nut with an inner diameter greater than twice the leakage point can be used to allow the leakage medium to flow out of the nut. The nut should be welded onto the valve body, and a bolt with the same specification as the nut should be added. A rubber or asbestos pad should be placed at the bottom of the nut, and the top of the bolt should be wrapped with adhesive tape and screwed into the nut to effectively reduce leakage. If the leakage medium pressure of the valve body is high and the leakage amount is large, then the drainage welding method is a better method. First, use an iron plate with a circular hole in the middle, weld an isolation valve with a diameter equivalent to the circular hole on the iron plate, open the isolation valve, align the center hole of the iron plate with the leakage point and stick it to the valve body, allowing the leakage medium to flow out through the center hole of the iron plate and the isolation valve. For situations where the bonding surface is not good, a rubber or asbestos pad can be placed on the bonding surface, and then the iron plate can be welded to the valve body, and the isolation valve can be closed. This can achieve a better sealing effect.