Basic working principle of pressure-sealing

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Basic principle of plugging leaks under pressure: When leaks occur in flanges, pipes, valves, and other components of equipment operating under normal production conditions, and the leaking fluid is ejected outward while still hot and under pressure, it is possible to select or create appropriate clamps at the location of the leak. These clamps can utilize their existing sealed chambers, or a new sealed chamber can be created at that location. A sealant that is plastic, capable of curing, and resistant to the leaking fluid as well as high temperatures is then injected into this sealed chamber. This increases the pressure inside the chamber above the pressure within the system; under certain conditions, the sealant cures rapidly, thereby creating a new, stable sealing structure that eliminates the leak. Technical characteristics of plugging leaks under pressure: 1. Plugging leaks under pressure offers significant economic benefits: when stopping a leak, operations can be carried out while the system is still at operating temperature and under pressure, without the need to shut down the system; this ensures that normal production continues, avoiding the economic losses associated with shutdowns for repairs. 2. Safe and reliable: When eliminating leaks in flammable and explosive areas, the entire process ensures no sparks are generated, no welding is required, thus guaranteeing safety. 3. Wide range of applications: This technology can be used to eliminate leaks in all types of fluid media. 4. Strong versatility: No special treatment is required at the leakage site; sealing can be carried out under pressure. It enables simple, flexible, safe, and rapid elimination of leaks. 5. Good detachability: Without damaging the original structure of the equipment or pipes, the new sealing structure can be easily removed, facilitating future maintenance of the equipment. 6. Low price. Application scope of pressure-based leak sealing: 1. Leakage locations: holes, cracks, welding defects on flanges, equipment, and pipelines, as well as leaks at threaded connections and packing boxes. 2. Leaking media: This technology can be used to eliminate leaks from almost all types of media, including various waters, water vapor, air, oxygen, nitrogen, hydrogen, gas, ammonia, liquefied gas, gasoline, diesel, heavy oil, lubricating oils, acids, bases, esters, alcohols, benzene derivatives, various heat carriers, various hydrocarbons, and various chemical gases and liquids. 3. Temperature of the medium being leaked: -195°C–900°C. 4. Medium pressure under leakage: Vacuum 0–32 MPa (320 Kg/cm2). Economic and social benefits of plugging leaks under pressure: 1. The benefit obtained from applying this technology is the avoidance of losses caused by unplanned shutdowns. 2. It prevents significant energy losses; among the eliminated leakage points, the majority (80%) were steam leaks. Apart from some major leaks that affected production, most were minor leaks. 3. It reduces the loss of certain raw materials, supplies, and products. 4. It eliminates leaks of flammable and explosive substances, prevents fire and explosion accidents in the equipment, and ensures safe production. 5. It eliminates noise and reduces environmental pollution. 6. It is easy and fast to operate, reduces maintenance time, and lowers repair costs. The cost of sealing under pressure can be recovered in the short term from the energy and materials saved by eliminating leaks. Services and contents for plugging leaks under pressure: 1. Technical consultation: Providing answers to various questions raised by users regarding the theories and practical challenges associated with pressure-sealing techniques. 2. Technology transfer and technical training: The content of technology transfer and training includes fixture design, techniques for eliminating leaks, various construction methods, the proper use of specialized tools and equipment, as well as the principles and methods for selecting sealants. Through lectures, watching technical videos, observing demonstration operations, and hands-on practice, trainees learn the aforementioned skills so that they can carry out pressure-sealing operations independently. 3. On-site emergency services: In the event of a severe leak in the user’s equipment, our company is willing to send professional sealing technicians to the site of the leak in order to resolve it as quickly as possible and ensure the safe continuation of production. 4. Supply of tools for sealing under pressure: (1) Special tools for injecting sealants: There are various specialized tools for injecting sealants, including manual, pneumatic, hydraulic, and mechanical types, available for selection. (2) Special tools for construction: These include various small pneumatic tools, rechargeable tools, tensioning devices, specialized clamps, various connectors and their accessories, all of which make pressure-bearing and sealing operations more convenient. 5. Supply of sealants: A variety of sealant models are available, suitable for various media and operating in temperature ranges from -195°C to 900°C. 6. Provision of protective equipment with pressure-sealing features: including professional one-piece work clothes, waterproof suits, heat-insulating leather work clothes, waterproof and heat-insulating gloves, safety helmets with face shields, noise-canceling earplugs, etc. Pressure-sealing methods: Different sealing methods are used depending on the location of the leakage. 1. There are three sealing methods for flange leaks: (1) Fixed flange clamps (Figure 1) – the clamps are designed based on the pressure and temperature of the leaking system, as well as the dimensions of the leakage site. An injection valve must be pre-installed on the fixture and in an open state; after the fixture is installed, it is necessary to ensure that there is an injection valve at the leakage point. Adjust the gap on the fixture to meet the requirements, and then the sealant can be injected. (2) Steel band clamping method: A stainless steel band with a thickness of 1–2 mm is wrapped around the outer circumference of the flange at the location of the leak, thereby serving as a replacement for flange clamps. It is only suitable for leakage points with a pressure of 2 MPa or less. The installation steps are as follows: A. Remove a nut near the leakage point, install a threaded insert joint, and then tighten the nut. To ensure safety, use a clamp to secure the area before removing the nut; repeat the same steps on the corresponding nut. (Figure 2) B: Select an asbestos gasket that is slightly larger than the flange gap, and use a hammer to gently press it into the gap so that there is an overlap of about 5 mm. C. Use a tensioner to tighten the steel strip. (Figure 3) D. Attach the injection gun at the joint to inject the sealant. (3) Soft brass wire containment method: A. Follow the construction steps of the steel strip fastening method (Figure 2) to install the screw hole injection joint. B. Use a flat chisel attached to a pneumatic hammer to insert the copper wire into the flange gap (Figure 4). C. Seal the gap with a round-bladed chisel attached to a pneumatic chisel to prevent the copper wire from coming out (Figure 5). D. Install the injection gun to inject the sealant. (4) The injection of sealant is carried out following a specific procedure: generally, injection starts from the point farthest from the leak, moving alternately from both sides toward the leak site, and finally sealant is injected at the leak site until the leak is completely eliminated. 2. The sealing method for leaks in pipe elbows, tees, and straight pipes typically involves using appropriate box-type clamps to completely enclose the leaking area, after which a sealant is injected into the enclosed space to eliminate the leak. The method of injecting sealant is the same as that used for flange sealing. It is also possible to use seal ring grooves designed according to the applicable temperature, pressure, and medium; asbestos packing is placed in these grooves, the clamp is applied to the leaking area, and then sealant is injected into the asbestos packing in the grooves to compress it against all the connection points, thereby eliminating the leak. (Figure 6) 3. Sealing methods for valve stuffing boxes (1) Kalan method: Fix the Kalan ring on the outer surface of the middle and lower parts of the stuffing box; use a long drill bit with a diameter of 3–4 mm to penetrate the wall of the stuffing box through the inner hole of the Kalan set screw. Then attach a syringe to the set screw and inject sealant, which quickly eliminates leaks. (Figure 7) (2) Threaded injection valve: When the size of the large valve’s packing box is relatively large, a blind hole is drilled on the outer surface of the lower part of the packing box; threads are created using a tap, and an injection valve is installed. The plug is then opened, and a drill bit with a diameter of about 3–4 is used to drill through the wall of the packing box. An injection gun is then attached to the injection valve, and sealing material is injected, which quickly eliminates any leaks. (Figure 8) 4. Sealing method for leaks at threaded connections: Place a clamp on the outer surface of the area where there is a thread leak, secure it with a set screw. Through the hole in the set screw, use a long drill bit with a diameter of about 3–4 mm to drill through the wall of the female thread. Then, use an injection gun to insert a small amount of sealant, which will quickly eliminate the leak. (Figure 9) Precautions for plugging leaks under pressure: 1. Select the appropriate sealant based on the conditions of the leak site (temperature, pressure, medium). 2. A correct analysis of the cause of the leakage is necessary; for example, if leakage occurs due to corrosion or erosion of the equipment or pipes by the medium, resulting in thin walls, such approaches should be used with caution. This technology primarily addresses sealing, rather than strengthening the equipment. 3. For leaks caused by cracks in the weld or base metal, this technique should not be used when it is impossible to control the further propagation of those cracks. 4. Operators working at the site where leaks occur must strictly follow the relevant safety and technical procedures; work must be carried out in a safe manner, and hasty actions must be avoided. Article source: baidu