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Pressure regulating valve plugging technology in thermal power plant
Thermal power plant regulating valve pressure plugging technology: 1 Introduction Power plant regulating valve is mainly used to control a variety of devices and their pipeline fluid medium operation, regulating valve leakage often occurs in the packing, flange seals and valve body Long-term regulation of the valve leakage can cause stem and flange sealing surface erosion, the final valve can be scrapped, coupled with the loss of fluid medium, the power plant consumption increases, the cost increases, economic decline. If the medium fluid is toxic, flammable, explosive, corrosive and so on, leakage, such as poisoning, fire, explosion and other casualties and accelerating the corrosion rate of plant equipment, shorten the service life, pollute the surrounding environment seriously and damage the power Production, damage people's health. The existence of the leak poses a serious threat to safe production, resulting in an increase in unplanned downtime of power plants. The following describes some of the reasons for regulating valve leakage and plugging methods and regulating valve repair and maintenance methods for reference. 2 regulating valve leakage in the form and factors 2.1 regulating valve packing leakage and the reasons for regulating the valve during operation, there is a relative movement between the stem and packing, which includes rotation and axial movement. As the number of switches increases, the number of relative motions also increases, as well as the effects of temperature, pressure and the characteristics of the fluid medium. Regulating valve packing is the most prone to leakage. It is due to the gradual reduction of contact pressure of packing, filler aging itself, loss of elasticity and other causes. At this time, the pressure medium will leak outwardly along the contact gap between the packing and the stem, and will blow away a part of the filler and flush the stem out of the groove for a long time, so as to enlarge the leakage. 2.2 Flange Leakage Adjustment Valve flange seal is mainly relying on the bolt preload, through the gasket to achieve a sufficient seal than the pressure to prevent the sealed pressure fluid medium leakage. There are many reasons for its leakage, gasket insufficient pressure, the surface roughness does not meet the requirements, gasket deformation and mechanical vibration, etc. will cause the seal gasket and the flange surface of the joint lax strict leak . In addition bolt deformation or elongation, gasket aging, resilience decline, such as cracks can also cause the flange surface sealing lax and strict. Flange leaks can not be ignored as human factors, such as partial installation of gaskets, partial pressure than partial tight tight, over the gasket design limits, and the uneven force in the process of flange fastening or two methods Lan center line offset, resulting in fake tight phenomenon are prone to leakage. 2.3 The leakage of the valve body and the reasons for leakage of the valve body is mainly due to the adjustment valve manufacturing process caused by casting or forging defects, such as trachoma, porosity, cracks, etc., and fluid medium erosion and cavitation is also caused by valve leakage Common factors. 3 with pressure plugging principle and advantages 3.1 Principle of pressure plugging The principle of pressure plugging is based on the liquid medium under dynamic conditions, the solid sealing material sealing mechanism as the basic basis. Method is to install special equipment leak site, the use of sealing parts and special equipment formed between the chamber, the use of special high-pressure plastic injection tools will be injected into the chamber sealant, and filled the entire chamber space, the sealant squeeze The force is balanced with the pressure of the leakage medium, and a new sealing structure is established to block the passage of the leakage pores and block the leakage of the medium. 3.2 The advantages of pressure plugging (1) does not require downtime or isolation of the system. (2) No pressure relief to the system. (3) Save a lot of energy and manpower. (4) greatly reduce the power loss caused by equipment isolation or downtime. (5) Reduce the social and economic losses. 4 Several common leakage point pressure sealing method introduced According to the specific circumstances of the power plant production site, you can use to replace the regulator valve, replace the regulator valve packing, replace the flange gasket or fill the hole to eliminate the general method of leakage. However, for the production and operation of the regulating valve, in the case can not be isolated, you must take the appropriate technical means to eliminate leakage in order to ensure the normal operation of unit production safety. 4.1 Power Plant Regulating Valve Leakage Pressure Leakage Leakage Treatment Using injection type pressure leaking technology is a safe and reliable technology, it uses special fixtures and hydraulic injection tools, the injection of sealant to the fixture and leakage Part of the outer surface of the cavity formed by the seal, quickly make up for a variety of complex leak defects. In the injection pressure is greater than the pressure of the leakage medium conditions, the leakage was forcibly stopped, the injection itself in a short period of time by the plastic body into an elastomer to form a flexible sealing structure and can maintain a certain working pressure than the pressure , To achieve the purpose of re-sealing. At present, the domestic and foreign production and use of seal injection can be divided into two categories: one is the thermal curing seal injection, such injection only reaches a certain temperature can be changed from plastic body to elastomer, at room temperature as a solid; the other One is the non-heat-curing seal injection agent, which is suitable for dynamic sealing operations at room temperature, low temperature and high temperature requirements, such sealing agent made of stick-shaped solid or two-component material, put it in high pressure injection gun After a certain pressure with good injection process and filling, without losing the function of regulating the valve switch. The following describes two commonly used methods: (1) For regulating valve packing box wall thickness greater than 8mm, under dynamic conditions using the injection pressure with plugging to eliminate defects, you can directly adjust the valve packing box wall to open a note The way the agent hole, the sealing chamber is the regulation valve packing box itself, into the regulation valve packing box sealing agent role and filler play the same role. First of all, adjust the position of the outer wall of the stuffing box of the valve with a drill of 10.5mm or 8.7mm in diameter. The hole can not be drilled, about 1 ~ 3mm left. Remove the drill bit and tap the tap of M12 or M10. After the end of the injector dedicated plug valve screwed on, and make it in the open position, with a 3mm diameter rod drill to the remaining regulatory valve packing box wall penetration, then the leakage of media along the bit row direction Spray, in order to prevent drilling high temperature, high pressure, toxic or corrosive medium spray wounding, drilling before the hole can be used a baffle, the first drill in the baffle with a diameter of 5mm holes to make it Can set too long drill bit, with the remaining wall thickness baffle drilling is not dangerous. Drill through the hole after the drill bit removed, the special stopper screwed to the screw position, cut off the medium to connect high-pressure injection gun injection seal injection operation. If the regulator valve packing box media pressure is low, you can also use a long diameter of 3mm drill directly through the hole, and then seal the injection operation. June 2003, Panzhihua Iron and Steel Power Plant 3 # main steam valve self-sealing Gland leak is the use of this plugging technology to solve the leakage of the regulatory valve to avoid a non-shutdown can not be resolved. (2) For the filling valve wall thinner control valve, you can use the auxiliary fixture for dynamic sealing operations. Auxiliary fixture just to make up for regulatory valve packing box wall thickness of the inadequacy, the equivalent of a fixed valve in the outer wall of the packing box special connector to connect high-pressure injection gun. Fixture of the machining method is difficult to get the ideal local fit surface, under conditions permitting, you can properly adjust the outer wall of the valve packing letter to make it better with the auxiliary fixture fit. If the shape of the filler wall of the leakage control valve is complicated or the condition of dressing is not allowed, a piece of asbestos rubber or rubber plate may be padded on the bottom of the auxiliary clamp, and the clamp bolt may be tightened so that the rubber plate on the bottom can well block the gap of the fitting surface . The auxiliary fixture should have a thread plug fitted with a stopper plug, followed by the same thickness of the stuffing box operation, the entire sealing operation is completed, do not immediately switch the control valve, and other sealed injection curing agent before they can invest Normal use. Mid-November 2002, Panzhihua Iron and Steel Power Plant high-pressure heater inlet valve flange valve flange leak, due to the regulatory valve packing box wall is thinner, is the use of auxiliary fixture for the production of dynamic sealing operations to solve the regulatory valve leakage problem. 4.2 Power Plant Valve Flange Leakage Pressure Leakage Treatment 4.2.1 Copper wire plugging method It applies to the two flanges smaller gap, uniform gap, low pressure medium leakage sealing plug, you can remove Bolt directly on the bolt-specific injection fittings, generally not less than two. When installing the injection fitting, loosen a nut, install the injection fitting, quickly retighten the nut, and then install another injection fitting, and can not release the required joint nut at the same time, so as to avoid the pressure on the gasket being higher than the pressure Significant decline, increased leakage, and even leakage media will blown away pads, leading to irreparable consequences. If the original large amount of leakage, G-shaped clip can be used to maintain a balanced pressure than the balance, after installing the bolting agent, the tool diameter or slightly smaller than the gap between the leakage flange embedded in the gap between the copper flange, while the law The outer edge of the flange rushes out of the lip to secure the copper wire in the flange clearance so that a new seal chamber is formed. Then you can connect the high-pressure injection gun for dynamic sealing operation, the injection direction should be carried out from the opposite point of the leak, and the end point should be close to the leak point. June 2003, Panzhihua Iron and Steel Power Plant # 1 low pressure Unicom vertical flange leakage is the use of this plugging technology to solve the problem of Unicom pipe flange leakage, to avoid a downtime. 4.2.2 strip around the law When the gap between the two flanges is slightly larger and does not exceed 8mm, the media pressure is less than 2.5MPa, the strip can be used to carry around the operation of the sealing method. It has high requirements on the coaxiality of the two flanges, and the requirement on the uniformity of the flange gap is not high. Steel strip generally use the thickness of 1.5--3.0mm, the width of 20 - 30mm can be produced by welding or riveting, the two joints need to add a transition gasket below, according to the size of the flange to determine the number of injection fittings installed. The installation of steel, the steel strip should be located in the gap between the two flanges, the connection bolts slightly twist a few buckets, then add the two transition pads, all wrapped flange gap, continue to tighten the bolts, and ultimately form a complete seal Cavity, then you can conduct dynamic sealing operations. 4.2.3 Flange convex clamp blocking method When the leakage flange gap is greater than 8mm, the medium pressure is greater than 2.5MPa, from the safety and reliability considerations, should be designed and manufactured into a precise size, the overall sealing performance, high pressure method Lan fixture, which has a high success rate of dynamic sealing operations, is a widely used sealing technology. Before operation, install the stopcock on the fixture and keep the stopcock open. Operators should stand on the vents. If leakage pressure or flow rate is large, use compressed air to blow the leakage medium aside or Attach long rods to the clamps to keep the operator from contact with the media. During installation, the injection hole of the fixture should be in the middle of the two flange connection bolts, and the injection hole near the leakage should be ensured. Do not align the injection hole with the bolt to avoid increasing the resistance of the injection. Fixture bolts tightened, the maximum gap between the fixture and the flange contact should not exceed o.5mm, the injection should start from the farthest point of leakage began to inject, gradually close to the leak, until the leak stopped. This method can also be used for pipe sealing. This method of plugging in Panzhihua Iron and Steel Plant # 1, # 2, # 3 unit routine maintenance of the universal application of pipe valve maintenance professionals must master a plugging method. For example, in 2003 # 1 and # 2 units gave the pump positive warm water back to the hydrophobic first and second valve flanges for leakage; in February 2003, # 2 auxiliary steam to deaerator hydrophobic 70% electric isolation valve front flange Of the leak; March 2003 # 1 high pressure heaters imported flange leakage and so on. 4.3 Power Plant Regulating Valve Leakage Pressure Leakage Treatment Valve body leakage treatment can be applied to the pipeline leakage treatment, there are two ways, 4.3.1 Adhesion It is the use of special adhesive tape pressure sealing A method. For the pressure medium and the leakage of small trachoma parts, the first leak around the polished metal luster, and then taper pin alignment leaks, the appropriate intensity into the leakage significantly reduced or temporary closure. The use of adhesive curing fast features, in a timely manner around the pin coated with adhesive, the establishment of a new solid sealing structure, to achieve the purpose of leakage. High pressure for the medium, the leakage of large defects available top pressure tools for sealing operations, the top pressure mechanism is fixed on the side of the regulating valve operation, high-speed top-pressure screw, so that the top of the screw axial pressure against the leak, Rotate the top pressure screw, using the top of the screw rivets tightly pressed on the leak site, forcing the leak to stop. If the top of the rivet is smaller than the leakage point, a piece of soft metal may be placed under the rivet. After the leakage is stopped, the metal surface around the leakage point should be cleaned in time to remove the rust and oil, and the prepared adhesive should be smeared on the periphery. After the adhesive is fully cured, remove the fixing screw of the screw and the rivet and remove the pressing mechanism. In order to ensure the pressure-proofing effect, it can be reinforced with glass cloth or the like in the leaking parts. 4.3.2 Welding Method a) In the case of low leakage medium pressure of the valve body and small leakage, a nut with an inner diameter more than double the leakage point may be used to let the leakage medium flow out from the nut and the nut cap On the valve body, add a bolt of the same size as the nut, place a rubber pad or asbestos pad at the bottom of the nut, and screw the top of the bolt around the upper tape to the nut to prevent the leakage. For the leakage of medium pressure, the large amount of leakage valve body, available drainage welding method. First of all, with a piece of iron, the middle to open a round hole, the diameter of a hole with a diameter of the isolation valve welded to the round hole in the iron, open the isolation valve, the center of the iron plate at the leak point fit in the valve body, Let the leakage medium through the iron center hole and isolation valve outflow. If the fit surface is not good, the rubber or asbestos pad can be placed on the fitting surface, and then welded around the iron plate and the valve body, and then close the isolation valve to achieve the purpose of re-sealing. b) high temperature and pressure in the leakage medium of the valve body, but the adjustment valve has a larger overall size, the amount of leakage is not large can also be used welding method, the first valve directly to the leakage point of the gap are welded to death Not welding point), and then use a section of the working conditions (working temperature, pressure) pipe length depending on the site environment may be (usually take about 200mm), its diameter should be greater than the leak, put a tube compatible Adjust the valve welded to one end of the pipe, and fully open the valve, and then take the other end of the pipe alignment leak welding, turn off the regulating valve to stop the leak .44 omnipotent plugging method regardless of which part of the regulating valve leak If the above methods are difficult to operate when the "parcel method" can also be used: the use of plate (pipe) in line with the working conditions of the production of a valve can be wrapped around the valve body or a leaky box, it is welded to the regulating valve So that it can be wrapped live leak, if there are difficulties in welding the box, you can open the hole in the box to stay the last method of welding method b) Method: plus steam valve method Can easily seal welding. The welding method is used repeatedly in the draining system of the main steam pipe of No. 1 machine of Panzhihua Iron and Steel Plant, the secondary door of # 3 main steam path by-pass, the high-pressure heater of 1 #, 2 # and 3 # units , Have achieved satisfactory success. This method of plugging in Panzhihua Iron and Steel Power Plant # 1, # 2, # 3 unit for routine maintenance with the best effect of a method, but also pipe valve maintenance professionals must master a plugging method. 5 Conclusion There are other components in the power plant production site pressure plugging, if we can grasp some of the basic knowledge of plugging, for the improvement of the power plant is of great help. Only a plant I 100MW start and stop a unit, the direct economic losses amounted to 300,000 yuan or more. Therefore, we can successfully carry out pressure leaking of on-site leakage points and reduce the number of unscheduled downtime, of which the benefits are significant. In short: (1) pressure plugging belongs to a nature of emergency repair work. Leakage with pressure plugging treatment is a temporary treatment measures, there are some limitations and timeliness. In the conditions of the situation, or to leak parts thoroughly overhaul. Elimination of the scene of "run, run, drip, drain" phenomenon, improve the health of equipment operation and maintenance of the fundamental method is to rely on the rationality of planned maintenance and equipment maintenance and improve the maintenance process. (2) The work environment with pressure and sealing is abominable, the operation time is long, the labor intensity is large, there are many uncertainties in the operation, and the operation risk is large. Pre-job safety preparation is very important, pre-job risk analysis must be full, the implementation of safety measures must be in place. (3) Pressure Seal is a highly specialized technology that requires the on-site response ability of the operator, has a high requirement on the mastery of mechanical expertise and the use of special tools for sealing with pressure. Due to the high requirements of workers and special equipment, this technology has some difficulties in the promotion of thermal power plants. At present the scene of the pressure plugging work by a number of professional companies to complete. (4) Pressure seal is a new technology, it also has a continuous improvement and improvement of the process, it has its own limitations and scope of application. With pressure plugging and can not solve all the leakage problem, is still in the exploration and improvement stage. Keyword search: Regulating valve information regulating valve products