How can pipeline leakage be solved without parking?
In the production process of chemical enterprises, pipelines are the main means of transportation for production devices, and the circulation of its material supply process depends on different specifications, realized by pipelines with different pressure levels and shapes, there are countless flanges, elbows, welds and other interfaces in the continuous bending chemical pipeline, if there is one welding junction failure or leakage out of control, it will be a serious threat to the normal operation of the device. If it is toxic, harmful, flammable, explosive, corrosive media, such as leakage, prone to poisoning, fire, explosion and other casualties, serious pollution of the surrounding environment damage people’s health. How to use the pressure plugging technology when the leakage does not need to stop the device for treatment has become a more important technology in production. The following summarizes the treatment methods and techniques for pipeline leakage control with pressure for reference.
Pipeline leakage form and factors
1. Straight pipe leakage
Leakage failure of straight pipeline may be caused by manufacturing defects of the pipeline itself and quality problems of pipe fittings, or may be due to pipe welding, it is caused by the reasons such as corrosion caused by unsuitable material selection of group pairs or pipes.
2. Elbow leakage
The leakage of elbow is mostly on the large radius outside of the elbow. When the media flows through the elbow, the media receives the resistance of the elbow, it leads to poor corrosion resistance of the material and unreasonable connection structure between the elbow and the straight pipe. There are gaps left, which can lead to the retention and concentration of the corrosion medium.
3. Pipe flange leakage
The pipe flange seal mainly depends on the pre-tightening force of the connecting bolt, and reaches enough sealing pressure through the gasket to prevent the leakage of the sealed pressure fluid medium. There are many reasons for its leakage, the pressure of the sealed gasket is insufficient, and the roughness of the joint surface does not meet the requirements, gasket deformation and mechanical vibration, etc. will cause the sealing gasket and flange joint surface is not tight and leakage occurs. In addition, Bolt deformation or extension, gasket aging, reduced resilience, cracking, etc. will also cause leakage due to lax sealing of flange surface. There are also human factors that cannot be ignored in the leakage of flange, such as the misalignment of the sealing gasket, which makes the partial sealing pressure insufficient and the tightening force is excessive, exceeding the design limit of the sealing gasket, in addition, during the process of fastening the flange, the uneven force or the deviation of the center line of the two flanges will cause the phenomenon of false tightening, which will easily lead to leakage.
Principle and advantages of pressure plugging
1. Principle of plugging technology with pressure
While the device is in operation, media leakage occurs. Under the condition of not changing working conditions and not affecting the operation of the equipment, a sealing chamber is established by using bandaging, isolation or making fixtures to cover the leakage point, by injecting the sealant into the sealing cavity, according to the system temperature and the rheological characteristics of the agent, control the coordination of the propulsion speed and the curing time of the sealing agent to ensure the filling effect of the agent, the sealing layer injected into the sealing cavity is even and dense, and an effective sealing pressure is formed so that leakage is stopped, thus establishing a new sealing structure.
2. The advantage of plugging with pressure
- (1) the system parking is not required, thus ensuring the long-term operation of the device.
- (2) there is no need to perform pressure relief replacement on the system.
- (3) avoid the loss caused by device parking and damage to other equipment.
- (4) economic losses and environmental pollution have been greatly reduced.
According to the specific situation of the production site of the company, under the circumstances that the production can be temporarily isolated or the process medium can be operated with fire, the methods of replacing pipelines, flange gaskets or welding holes can be adopted to eliminate general leakage. But for the pipelines of key parts of the device, when the working condition is that flammable and explosive media cannot be isolated or the welding hot work cannot be carried out, corresponding leak plugging techniques with pressure must be adopted to eliminate leakage, to ensure the safe and stable operation of the unit.
1. Pipeline leakage with pressure plugging technology
1.1 Quick binding plugging technology
The quick bundling plugging technology applies to the straight pipes, elbows, reducer, pipe coupling, flange roots and so on whose specification is less than or equal to DN300mm. It is also applicable to the pipes with working pressure ≤ 1.0MPa and working temperature ≤ 150℃. The plugging material adopts high-strength high-temperature resistant plastic binding tape. The operation principle is: wrap the leakage points tightly with high-strength high temperature resistant plastic banding tape. The plugging method is shown in Figure 1.
Figure.1 quick bundling plugging technology
1.2 Steel band binding pressure pad plugging technology
Leakage control technology of steel band binding pressure pad is suitable for straight pipe, elbow, reducer pipe, flange root, etc. It is suitable for pipes with working pressure ≤ 2.0MPa and working temperature ≤ 180 ℃. Plugging materials are special metal steel belts and high temperature resistant rubber pads. The operation principle is: Press the high temperature resistant rubber pad to the leakage point, use the steel belt tensioner to tighten the steel belt, and tighten the high temperature resistant rubber pad.
Fig.2 leakage control technology of steel band binding pressure pad
1.3 Injection glue plugging technology of metal fixture
Metal fixture glue plugging technology applicable to straight pipe, bend pipe with large bending radius, and the leakage points are welding line, sand hole, crack and other peripheral areas without large area thinning and corrosion. Applicable to working pressure ≤ 20MPa, the pipe with working temperature ≤900℃. The operation principle is: processing the fixture according to the shape of the pipe and pipe fitting and the size of the leakage point the fixture is a cavity at the leakage point, the cavity edge of the fixture is consistent with the shape of the pipe or pipe fitting the fixture is set with glue-injection screw holes; tighten the fixture, connect the high-pressure glue gun, and inject glue into the fixture cavity to establish a sealed cavity to achieve the plugging effect, as shown in figure 3.
Fig.3 leakage control technology of steel band binding pressure pad
1.4 Isolation type fixture plugging technology
The leakage control technology of the isolation fixture is suitable for straight pipes and bends with large bending radius, and the surrounding of the leakage point is obviously thinned and widespread corrosion. If the injection glue leakage control technology is adopted, it is easy to inject sealant into the pipeline and even break the pipeline, it is applicable to pipelines with working pressure ≤ 10MPa and working temperature ≤ 900℃. Plugging theory is to process the fixture according to the shape of the pipe, the size of the pipe and the leakage point. The whole section of the corrosion or thinning pipeline is all covered with a cavity, and a valve is added to the lower part of the fixture space, establish a sealing groove between the fixture cavity and the fixture periphery, inject glue into the sealing groove to isolate the medium from the external of the fixture, and finally turn off the drainage valve to achieve the plugging effect, as shown in figure 4.
Figure.4 plugging technology of isolation fixture
Compare four pipeline leakage plugging methods: banding method and steel strip method are only applicable to low pressure, low temperature and single point leakage. The fixture glue injection method can be used at all temperatures and pressures, and has a wide range of applications. The disadvantage is that it is not applicable when the leakage point corrosion is serious, multi-point leakage, and the pipeline thinning. Isolation fixture leakage control technology is a new technology, a supplement to fixture leakage control method, a special treatment method for pipeline multi-point leakage, corrosion thinning and other serious working conditions. This kind of separation type fixture leakage technology is suitable for the company’s liquid ammonia leakage, acid and alkali medium, combustible gas, pipeline thinning and serious corrosion pipeline. It makes up for the gap of our previous plugging, and its disadvantage is that it requires enough clamping space around the leaking part. It takes a long time to make a special fixture for processing.
2. Pipe flange leakage leakage plugging technology with pressure
2.1 Fixture glue plugging method
Metal fixture glue plugging technology is suitable for all flange leakage, regardless of size, reducer, eccentricity, temperature from-200 ℃ to 900 ℃, all pressure can be used. The operation principle is: Tailor-made fixture according to the outer dimensions of the pipe flange, clamp it on the leak flange to form a cavity, and then inject sealant into the fixture through the glue injection thread, thus the sealing cavity is established to achieve the plugging effect, as shown in figure 5.
Figure.5 Schematic diagram of pipe flange fixture
2.2 The packing and glue plugging technology of steel belt
Steel Band binding glue plugging technology is suitable for Flange gasket leakage, and is suitable for flanges with working pressure ≤ 2.5MPa and working temperature ≤ 450 ℃. The material is special steel strip and high temperature resistant flexible sealant. The operation principle is: tighten the steel belt along the outer diameter of the flange; Remove the flange nut, install the glue nut, connect the high-pressure glue gun, and inject glue to the flange gasket; Replace the original flange nut. See Figure 6 for the plugging method.
Fig. 6 leakage control technology of steel belt bundle and injection glue
2.3 Alloy mosaic plugging technology
The Alloy mosaic plugging technology is applicable to the places around the hole seam where the base material is hard. It is applicable to flanges with working pressure ≤1.0mpa and working temperature ≤180℃. The operation principle is: Insert the alloy material with a certain taper between the two flanges with a hammer, then remove the flange nut, install the glue nut, connect the high-pressure glue gun, and inject glue to the flange gasket.
Fig.7 Alloy mosaic plugging technology
2.4 Steel rope binding glue plugging technology
Steel rope binding glue plugging technology applies to the flange with two flanges clearance greater than millimeters and working pressure ≤12mpa and working temperature ≤600 ℃. The operation principle is: use special tools to hoop the flange gap with a steel rope, then add an injection valve on the steel rope, and inject a sealant into the leaking flange, thus establishing a sealed cavity to achieve the plugging effect.
Figure.8 plugging technology of steel rope binding and injection
Compared with four pipe flange leakage plugging methods, the fixture injection method is simple, convenient and wide in use. Its disadvantage is that it needs machine tool processing, takes a long time and cannot handle the leakage point in the first time. The other three plugging methods do not need to process fixtures, which is convenient, fast and timely, but all have certain limitations.
- 1. There are many methods of plugging with pressure. Before implementing plugging with pressure, the leakage situation should be found out to formulate a feasible technical scheme of plugging with pressure.
- 2. The operation safety plan should be formulated before plugging with pressure. Protective equipment must be worn when plugging with pressure. When implementing leakage plugging with pressure in pipe trenches and inspection wells, attention must be paid to the ambient temperature to avoid hypoxia, leakage surface expansion and even uncontrollable situation.
- 3. A variety of pressure plugging techniques can be used. If the application of Alloy mosaic plugging, the outer surface is still added with steel strip and fixture to strengthen the fixed.
- 4. Pipeline crack leakage caused by thermal stress, while plugging, measures should be taken to eliminate or reduce thermal stress to prevent secondary leakage.
- 5. The design strength of steel clamp and steel fixture should meet the requirements of working pressure.
- 6. Plugging technology with pressure is mostly an emergency treatment, and long-term reliable repair should be carried out during normal pipeline maintenance.
Plugging with pressure is a kind of emergency repair work. The leakage point of leakage plugging treatment with pressure is a temporary treatment measure with certain limitations and timeliness. Under the condition, it is necessary to thoroughly overhaul the leaking parts. Eliminate the phenomenon of “running, running, dripping and leaking” on site and improve the stable operation of equipment is to rely on the rationality of planned maintenance and improve the level of equipment maintenance. The working environment for pressure and leakage plugging of the device is harsh, the working time is long, the labor intensity is large, there are many uncertain factors in the operation and the operation risks are large. The safety preparation before work is very important, the risk analysis before operation must be sufficient, and the implementation of safety measures must be in place. Moreover, the technology of plugging with pressure is very professional, which requires the on-site strain capacity of operators, the mastery of mechanical professional knowledge and the use of special tools for plugging with pressure, etc. Due to the high requirements for operators and special equipment, professional training is required for operators and certain qualifications are obtained to engage in this technical work. Plugging technology with pressure has its own limitations and application scope. Plugging with pressure cannot solve all leakage problems, and we still need continuous study and exploration in our future work.
Source: China Alloy steel Pipeline Manufacturer – Yaang Pipe Industry Co., Limited (www.steeljrv.com)
(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)
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