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 outward 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 leaving the groove, causing the leakage surface to become larger and larger.

2、 Leakage of flanges
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 inadequate 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 aspects that require special attention for flange leaks. In addition, the valve body may also experience leakage due to space limitations, so we will not elaborate on it here.

3、 Methods 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 to deal with external leakage of high and medium pressure butterfly valves in power plants, among which the injection type pressure plugging technology has a higher safety, and this has been concluded in detail. This method uses special fixtures and hydraulic injection tools to inject sealant into the sealing cavity formed on the outer surface of the fixture and the leaking part, which has a good effect on remedying 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. There are two types of sealing agents that are widely used and promoted in China today: (1) Heat cured sealing agents. The use of this injection agent needs to meet certain conditions, which is temperature. When the temperature reaches a certain level, the injection agent is elastic and generally 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 more than 8 millimeters, 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 position to drill a hole with a diameter of 10.5 millimeters or 8.7 millimeters on the outer wall of the packing box of the high and medium pressure butterfly valve. It should be emphasized that this hole should not be drilled through, and the distance left should be between 1-3 millimeters. 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 choose 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 toxic substances sprayed out, can cause certain injuries to the workers. Mild injuries can occur, and serious ones can even threaten 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 for pressure plugging with small gaps between two flanges, uniform gaps, and low leakage medium pressure. The bolt specific injection agent joint should be placed on the removed bolt, with two being lower and 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. Adhesive method

If it is a pressure medium or a sand hole with small leakage, you can first polish the area around the leakage point to a metallic luster, then use a tapered pin to align with the leakage point and inject it with appropriate force, mainly to reduce leakage or temporarily seal it. The curing speed of adhesive is relatively fast, which can be used to apply adhesive around the pins, forming a new solid sealing structure, which can produce a leak proof effect to a certain extent. If the medium pressure is high and the leakage is large, 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 pressure screw is used to align the axial direction of the top pressure screw with the leakage point. The rotating pressure screw is used to tightly press the rivet at the end of the top pressure screw onto 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 of the same diameter as the circular hole onto the circular hole of the iron plate. Open the isolation valve, align the center hole of the iron plate with the leakage point and press it against the valve body, allowing the leaked 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, then the iron plate is welded to the valve body, and the isolation valve is closed. This can achieve a better sealing effect.