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Flange seal and leak seal treatment methods
Flange seals affect the flange seal is many factors. Mainly: bolt preload; sealing surface type; gasket performance; flange stiffness; operating conditions. For decades, ANSI Flanges designed by the National Institute of Standards have provided a proven seal technology for the oil and gas industry and have been very successful. However, as the needs of the oil and gas industry have changed, defects in ANSI flanges continue to emerge. Cost-benefit principles, environmental protection, and best health and safety assurance are the three major topics facing operators and contractors in the 21st century. As a result, people are beginning to consider new ways to seal their flanges. The sealing principle of the ANSI flange is extremely simple: the two sealing faces of the bolt press against the flange gasket and form a seal. But this also led to the destruction of the seal. In order to maintain the seal, you have to maintain a huge bolt force. To do this, the bolt needs to be bigger. Larger bolts, on the other hand, must match larger nuts, which means that larger diameter bolts are required to create the conditions for tightening the nut. As everyone knows, the larger the diameter of the bolt, the applicable flange will become curved, the only way is to increase the flange part of the wall thickness. The entire installation will require extreme size and weight, which becomes a particular problem in offshore environments where weight is always a major issue that one must pay attention to. And, fundamentally, the ANSI flange is an ineffective seal that requires 50% of the bolt load to be used to compress the gasket while leaving only 50% of the load to hold the pressure. However, the main design disadvantage of ANSI flanges is that it can not guarantee zero leakage. This is its design deficiencies: the connection is dynamic, and periodic loads such as thermal expansion and undulation, can cause movement between the flange faces, affecting the function of the flange, thereby compromising the integrity of the flange and eventually leading to leakage. The new flange developed by Vector Corporation overcomes the shortcomings of ANSI flanges. Compact flange has all the advantages: The standard flange not only saves space, reduce the weight, more importantly, to ensure that the joints will not leak. The reason why the compact flange size is reduced is due to the reduced diameter of the seal which will reduce the cross-section of the sealing surface. Second, the flange gasket has been replaced by a seal ring to ensure that the sealing surface is matched to the sealing surface. As a result, only a small amount of pressure is required to compress the sealing surface. As the required pressure is reduced, the size and number of bolts required can be reduced accordingly. The result is a new product that is small in size and light in weight (70% to 80% lighter than conventional ANSI flanges). Flange leak sealing method I. Leaking parts and conditions DN150 flange on both sides of the flange bolts connected to the flange connection gap is extremely small, it is impossible to inject through the gap sealant to eliminate leakage. Leakage medium is steam, leaking system temperature 400 ~ 500 ℃, system pressure 4MPA. Two. Sealing construction method According to the scene of the leak site survey, in order to achieve a limited block, the use of fixed jig method to contain the leakage point to form a sealed chamber, injection sealant, thereby eliminating leakage. 1. Fixture design (1) fixtures structure form to determine ①Inclusion of leakage points, the establishment of the valve flange and pipe flange connection flange between the seal cavity. In order to prevent pressure leaks between the valve body and the flange clearance due to pressure suppression, an annular cavity is filled with plastic at the anastomosis between the fixture and the outer flange of the valve body. ② Reducing flange In the process of injection, the fixture tends to displace to the flange side of the smaller diameter, so it adopts the limit measures of the tooth-shaped contact and clamping. 2. Sealant selection and dosage estimates (1) sealant selection According to the leakage temperature and leakage characteristics of the site, the use of TXY-18 # A-type sealant. The sealant is resistant to temperature, media and injection process performance, easy to establish a uniform and dense seal structure, and the seal can maintain long-term stability. (2) dosage estimates unilateral leakage point sealant 4.5KG. 3. Construction operation (1) fixture installation, due to tooth contact, tooth tip diameter smaller size, the installation needs peripheral knock fixture outer wall tooth deformation occurs, clamping limit. (2) After the injection operation is completed, the jig and the valve body and flange annular cavity are filled with the sealing cavity, and then the middle cavity is injected. The injection process should be balanced with pressure and pay attention to the re-pressing to prevent the stress relaxation. (3) After the sealant is cured, after the observation of the effect, local replenishment compaction, to prevent stress relaxation, and then close the injection hole.