The handling method for leakage of high and medium pressure butterfly valves
Addtime：2023-04-23 From： View：479
Leakage of high and medium pressure butterfly valves is a relatively common problem. However, in some critical system equipment, if a high and medium pressure butterfly valve leaks, it will affect industrial production, and in more serious cases, it will even endanger the lives and property safety of the people. The high-pressure butterfly valves of the power station are connected to the main and auxiliary equipment and systems of the power station, and their significance is self-evident. Below are several methods for handling the leakage of the high-pressure butterfly valves in the power station:
1. Leakage of packing material for high and medium pressure butterfly valves
The valve stem and the packing will form a moving state with each other, which will be reflected in the operation of high and medium pressure butterfly valves. The more times the high and medium pressure butterfly valve is opened and closed, the more movement there will be. In addition, the effects of temperature and pressure will greatly increase the possibility of packing leakage in the high and medium pressure butterfly valve. During this period, the pressure of the packing will gradually decrease, and its elasticity will no longer exist. 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 lead to the problem of the packing being blown away and the valve stem detaching from the groove, causing the leakage area to become larger and larger.
II. Leakage of the Flange
The causes of flange leakage are often not limited to a single aspect. For instance, the compression force of the sealing gasket may be insufficient, the roughness of the joint surface may deviate from the required standard by a certain margin, or the gasket may deform. As a result, the sealing gasket and the flange do not achieve a complete and sufficient contact, resulting in a gap and leakage occurs accordingly. At the same time, other reasons that lead to poor sealing of the flange surface include bolt deformation or elongation, aging of the gasket, decreased resilience, cracking, etc., all of which can also cause leakage. In addition, human factors are also an aspect that needs special attention for flange leakage. Moreover, the valve body may also have leakage problems. Due to the limitation of the text, I will not elaborate on this here.
III. Methods for Handling External Leakage of High and Medium Pressure Butterfly Valves in Power Stations
Pressure-containment treatment for leakage in the filler chamber
There are various methods for dealing with external leakage of high-pressure butterfly valves in power stations. Among them, the one with relatively high safety is the injection-based pressure-sealing technology, which has been concluded in a detailed manner. This method uses special fixtures and hydraulic injection tools to inject sealant into the sealed cavity formed by the fixture and the outer surface of the leakage area. The effect of remedying the leakage defect is quite good, and the time taken is relatively short. When the injection pressure exceeds the pressure of the leakage medium, it will force the leakage to stop, and the injection agent will transform from a plastic body to an elastic body. At this time, the sealing structure has certain elasticity and also has a certain working sealing pressure ratio. The secondary sealing eventually forms. This undoubtedly increases the good sealing performance. Currently, the most commonly used sealing injection agents in China are the following two types: (1) Thermosetting sealing injection agent. The use of this injection agent requires certain conditions, that is, the temperature. When the temperature reaches a certain level, the injection agent becomes an elastic body, usually in the form of a solid. (2) Non-thermosetting sealing injection agent. Its application range is very wide. It can be operated under various temperatures, and it can also be installed in the high-pressure injection gun. The injection and filling performance are both good, and the switching function of the high-pressure butterfly valve can also be well preserved. When the wall thickness of the packing chamber of the high-pressure butterfly valve is more than 8 millimeters, the leakage problem can be directly handled by using the injection-based pressure-sealing method on the wall surface of the packing chamber of the high-pressure butterfly valve. The sealing cavity is the packing chamber itself of the high-pressure butterfly valve. The injection agent can play the same role as the packing. Find an appropriate position to drill a hole with a diameter of 10.5 millimeters or 8.7 millimeters on the outer wall of the packing chamber of the high-pressure butterfly valve. It should be emphasized that this hole must not be drilled through, and the distance left should be between 1 and 3 millimeters. Remove the drill bit, and use an M12 or MIO tap to tap. After this work is completed, tighten the special valve plug for injection agent. The valve should be in the open state. Then choose a long drill bit, a diameter of 3 millimeters should be selected. The purpose is to drill through the remaining wall of the packing chamber of the high-pressure butterfly valve. The leakage will be sprayed out in the direction of the drill bit. There will be certain risks during the drilling process, mainly because excessive temperature or pressure or the spraying of toxic substances will cause certain harm to the workers. Mildly, it will cause injury; severely, it will even threaten life safety. Therefore, this must not be ignored. Before drilling, using a shield is a good control method.
Pressure-resistant leak sealing treatment using copper wire containment method for flange leaks
The applicable scope of this method is for pressure-sealing operations where the gap between the two flanges is small, the gap is uniform, and the pressure of the leaking medium is low. The special injection connector for bolts should be placed on the removed bolts. Two of them should be lower and should be larger than the other two. When installing the injection connector, do not tighten all the nuts at once. Instead, loosen one nut and install the injection connector properly. Then, immediately tighten the nuts after installing the injection connector. For other injection connectors, it is necessary to emphasize that the required connector nuts should not be loosened simultaneously, as this will reduce the sealing pressure on the gasket, increase the leakage, and in severe cases, the leakage substance may even blow away the gasket. If such a situation actually occurs, it will be very difficult to take remedial measures, and the losses will be incalculable.
Pressure-resistant leak sealing treatment for valve body leakage
Bonding method
If the pressure medium is a gas or vapor and the leakage volume is small, the area around the leakage point can be ground to have a metallic luster first. Then, a tapered pin can be aligned with the leakage point and pushed in with appropriate force. The main purpose is to reduce the leakage or temporarily seal it. The adhesive cures quickly, so this characteristic can be utilized to apply the adhesive all around the pin, thereby forming a new solid sealing structure. This can achieve a certain degree of leak prevention effect. If the pressure of the medium is high and the leakage volume is large, sealing operations can be carried out. Using a pressure-pressing tool, during the operation, the pressure-pressing mechanism is fixed on one side of the high-pressure butterfly valve, and the high-speed pressing screw is pressed, making the axial direction of the pressing screw align with the leakage point. Rotate the pressing screw, and use the rivet at the end of the pressing screw to tightly press on the leakage area. This is also an effective way to stop the 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 promptly.
2. Welding method
If the pressure of the leaked medium in the valve body is low and the leakage volume is small, a nut with an inner diameter twice as large as the leakage point can be used. This will allow the leaked medium to flow out through the nut and then the nut can be welded onto the valve body. A bolt of the same specification as the nut should be used, and a rubber or asbestos pad should be placed at the bottom of the nut. The top of the bolt should be wrapped with rubber tape and then screwed into the nut. This can effectively reduce the occurrence of leakage. If the pressure of the leaked medium in the valve body is high and the leakage volume is large, then the引流 welding method is a better approach. First， use a piece of iron plate with a circular hole in the middle. Weld a isolation valve with an aperture of the same diameter as the hole onto the circular hole of the iron plate. Open the isolation valve and place the center hole of the iron plate flush against the leakage point on the valve body. Let the leaked medium flow out through the center hole of the iron plate and the isolation valve. For cases where the fitting surface is not good， a rubber or asbestos pad can be placed on the fitting surface， then weld the periphery of the iron plate to the valve body， and then close the isolation valve. The sealing effect achieved in this way is also relatively good.
1. Leakage of packing material for high and medium pressure butterfly valves
The valve stem and the packing will form a moving state with each other, which will be reflected in the operation of high and medium pressure butterfly valves. The more times the high and medium pressure butterfly valve is opened and closed, the more movement there will be. In addition, the effects of temperature and pressure will greatly increase the possibility of packing leakage in the high and medium pressure butterfly valve. During this period, the pressure of the packing will gradually decrease, and its elasticity will no longer exist. 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 lead to the problem of the packing being blown away and the valve stem detaching from the groove, causing the leakage area to become larger and larger.
II. Leakage of the Flange
The causes of flange leakage are often not limited to a single aspect. For instance, the compression force of the sealing gasket may be insufficient, the roughness of the joint surface may deviate from the required standard by a certain margin, or the gasket may deform. As a result, the sealing gasket and the flange do not achieve a complete and sufficient contact, resulting in a gap and leakage occurs accordingly. At the same time, other reasons that lead to poor sealing of the flange surface include bolt deformation or elongation, aging of the gasket, decreased resilience, cracking, etc., all of which can also cause leakage. In addition, human factors are also an aspect that needs special attention for flange leakage. Moreover, the valve body may also have leakage problems. Due to the limitation of the text, I will not elaborate on this here.
III. Methods for Handling External Leakage of High and Medium Pressure Butterfly Valves in Power Stations
Pressure-containment treatment for leakage in the filler chamber
There are various methods for dealing with external leakage of high-pressure butterfly valves in power stations. Among them, the one with relatively high safety is the injection-based pressure-sealing technology, which has been concluded in a detailed manner. This method uses special fixtures and hydraulic injection tools to inject sealant into the sealed cavity formed by the fixture and the outer surface of the leakage area. The effect of remedying the leakage defect is quite good, and the time taken is relatively short. When the injection pressure exceeds the pressure of the leakage medium, it will force the leakage to stop, and the injection agent will transform from a plastic body to an elastic body. At this time, the sealing structure has certain elasticity and also has a certain working sealing pressure ratio. The secondary sealing eventually forms. This undoubtedly increases the good sealing performance. Currently, the most commonly used sealing injection agents in China are the following two types: (1) Thermosetting sealing injection agent. The use of this injection agent requires certain conditions, that is, the temperature. When the temperature reaches a certain level, the injection agent becomes an elastic body, usually in the form of a solid. (2) Non-thermosetting sealing injection agent. Its application range is very wide. It can be operated under various temperatures, and it can also be installed in the high-pressure injection gun. The injection and filling performance are both good, and the switching function of the high-pressure butterfly valve can also be well preserved. When the wall thickness of the packing chamber of the high-pressure butterfly valve is more than 8 millimeters, the leakage problem can be directly handled by using the injection-based pressure-sealing method on the wall surface of the packing chamber of the high-pressure butterfly valve. The sealing cavity is the packing chamber itself of the high-pressure butterfly valve. The injection agent can play the same role as the packing. Find an appropriate position to drill a hole with a diameter of 10.5 millimeters or 8.7 millimeters on the outer wall of the packing chamber of the high-pressure butterfly valve. It should be emphasized that this hole must not be drilled through, and the distance left should be between 1 and 3 millimeters. Remove the drill bit, and use an M12 or MIO tap to tap. After this work is completed, tighten the special valve plug for injection agent. The valve should be in the open state. Then choose a long drill bit, a diameter of 3 millimeters should be selected. The purpose is to drill through the remaining wall of the packing chamber of the high-pressure butterfly valve. The leakage will be sprayed out in the direction of the drill bit. There will be certain risks during the drilling process, mainly because excessive temperature or pressure or the spraying of toxic substances will cause certain harm to the workers. Mildly, it will cause injury; severely, it will even threaten life safety. Therefore, this must not be ignored. Before drilling, using a shield is a good control method.
Pressure-resistant leak sealing treatment using copper wire containment method for flange leaks
The applicable scope of this method is for pressure-sealing operations where the gap between the two flanges is small, the gap is uniform, and the pressure of the leaking medium is low. The special injection connector for bolts should be placed on the removed bolts. Two of them should be lower and should be larger than the other two. When installing the injection connector, do not tighten all the nuts at once. Instead, loosen one nut and install the injection connector properly. Then, immediately tighten the nuts after installing the injection connector. For other injection connectors, it is necessary to emphasize that the required connector nuts should not be loosened simultaneously, as this will reduce the sealing pressure on the gasket, increase the leakage, and in severe cases, the leakage substance may even blow away the gasket. If such a situation actually occurs, it will be very difficult to take remedial measures, and the losses will be incalculable.
Pressure-resistant leak sealing treatment for valve body leakage
Bonding method
If the pressure medium is a gas or vapor and the leakage volume is small, the area around the leakage point can be ground to have a metallic luster first. Then, a tapered pin can be aligned with the leakage point and pushed in with appropriate force. The main purpose is to reduce the leakage or temporarily seal it. The adhesive cures quickly, so this characteristic can be utilized to apply the adhesive all around the pin, thereby forming a new solid sealing structure. This can achieve a certain degree of leak prevention effect. If the pressure of the medium is high and the leakage volume is large, sealing operations can be carried out. Using a pressure-pressing tool, during the operation, the pressure-pressing mechanism is fixed on one side of the high-pressure butterfly valve, and the high-speed pressing screw is pressed, making the axial direction of the pressing screw align with the leakage point. Rotate the pressing screw, and use the rivet at the end of the pressing screw to tightly press on the leakage area. This is also an effective way to stop the 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 promptly.
2. Welding method
If the pressure of the leaked medium in the valve body is low and the leakage volume is small, a nut with an inner diameter twice as large as the leakage point can be used. This will allow the leaked medium to flow out through the nut and then the nut can be welded onto the valve body. A bolt of the same specification as the nut should be used, and a rubber or asbestos pad should be placed at the bottom of the nut. The top of the bolt should be wrapped with rubber tape and then screwed into the nut. This can effectively reduce the occurrence of leakage. If the pressure of the leaked medium in the valve body is high and the leakage volume is large, then the引流 welding method is a better approach. First， use a piece of iron plate with a circular hole in the middle. Weld a isolation valve with an aperture of the same diameter as the hole onto the circular hole of the iron plate. Open the isolation valve and place the center hole of the iron plate flush against the leakage point on the valve body. Let the leaked medium flow out through the center hole of the iron plate and the isolation valve. For cases where the fitting surface is not good， a rubber or asbestos pad can be placed on the fitting surface， then weld the periphery of the iron plate to the valve body， and then close the isolation valve. The sealing effect achieved in this way is also relatively good.