Flange seal and leak seal treatment method
Flange seal
The factors that affect the flange seal are manifold. Mainly: bolt pre-tightening force; sealing surface type; gasket performance; flange stiffness; operating conditions. [Flange seal manufacturer flange seal manufacturer flange seal supplier]
ANSI flanges designed by the American National Standards Institute have provided a suitable sealing technology for the oil and gas industry for decades, and have been effective. But as the demand for the oil and gas industry has changed, the deficiencies of ANSI flanges are constantly being exposed. Cost-effectiveness principles, environmental protection, and optimal health and safety assurance are the three major issues facing operators and contractors in the 21st century. Therefore, people are beginning to consider new flange sealing methods. The sealing principle of ANSI flanges is extremely simple: the two sealing faces of the bolt press each other against the flange gasket and form a seal. But this also causes damage to the seal. In order to maintain the seal, it is necessary to maintain a huge bolt force. To do this, the bolts have to be made even bigger. Larger bolts are matched to larger nuts, which means that larger diameter bolts are needed to create the conditions for tightening the nuts. As everyone knows, the larger the diameter of the bolt, the more suitable the flange will become. The only way is to increase the wall thickness of the flange. The entire device will require a great size and weight, which becomes a special problem in the offshore environment, because weight is always a major concern for people in this situation. Moreover, fundamentally, the ANSI flange is an ineffective seal that requires 50% of the bolt load to be used to squeeze the gasket, while the load used to maintain the pressure is only 50%.
However, the main design disadvantage of ANSI flanges is that it does not guarantee leak-free. This is the design flaw: the connection is dynamic, and cyclic loads such as thermal expansion and undulations cause movement between the flange faces, affecting the function of the flange, thereby impairing the integrity of the flange and ultimately leakage.
The new flange developed by Vector has overcome the shortcomings of ANSI flanges. The compact flange has all the advantages: the standard flange not only saves space, reduces weight, but more importantly ensures that the joint does not leak. The reduced size of the compact flange is due to the reduced diameter of the seal which will reduce the cross-section of the seal face. Secondly, the flange gasket has been replaced by a sealing ring to ensure that the seal faces the sealing surface. In this way, only a small amount of pressure is required in order to press the cover tightly. As the required pressure is reduced, the size and required number of bolts can be reduced accordingly. The result was a new product that was small and lightweight (70% to 80% lighter than traditional ANSI flanges).
Flange leak sealing treatment method [Flange seal manufacturer flange seal manufacturer flange seal supplier]
I. Leakage location and condition The flange bolts on both sides of the DN150 valve body leak. Because the flange connection gap is extremely small, it is impossible to inject the sealant through the gap to eliminate leakage. The leakage medium is steam, the leakage system temperature is 400-500 ° C, and the system pressure is 4 MPA.
Second, the sealing construction method According to the site investigation of the leakage site, in order to achieve limited sealing, a fixed fixture method is used to contain the leakage point to form a sealed cavity, and a sealant is injected to eliminate leakage.
1, fixture design
(1) Determination of the structure of the fixture
1 Contain the leak point and establish the sealing cavity between the valve body flange and the pipe flange connection between the short flanges. In order to prevent the leakage of the potential leakage between the valve body and the flange due to the pressure, the annular cavity is injected at the outer edge of the clamp and the flange of the valve body.
2 During the different diameter flange injection process, the clamp is easy to be displaced to the small-diameter flange side, so the limit action of the tooth-shaped contact clamping is adopted.
2, sealant selection and dosage estimation [Flange gasket manufacturer flange seal manufacturer flange seal supplier]
(1) Sealant selection According to the leakage system temperature and leakage characteristics, TXY-18#A type sealant is used. The sealant is excellent in temperature resistance, medium resistance and injection process performance, and is easy to establish a uniform and dense sealing structure, and the seal can maintain long-term stability.
(2) Estimation of the amount of one side leakage point requires a sealant 4.5KG.
3. Construction operation
(1) Fixture installation, due to the tooth-shaped contact, the inner diameter of the tooth tip is small, and the outer ring of the outer ring of the clamp is required to be deformed when the installation is performed, and the limit is clamped.
(2) After the injection operation completion clamp and the valve body and the flange annular cavity are injected into the sealed cavity, the intermediate cavity injection is performed, and the injection process should be balancedly applied, and the injection pressure should be paid attention to prevent stress relaxation.
(3) After the sealant is cured, after the effect observation, local refilling is performed to prevent stress relaxation, and the injection hole is closed. (Source: Shengwei Seal)
Expanded PTFE gasket
product manual:
1. Made of 100% expanded PTFE, almost resistant to all chemical media;
2. Soft, twistable and tightly flanged;
3. Excellent resistance to cold flow and creep resistance;
4. Use in the alternating parts of temperature and pressure.
Description: [Flange seal manufacturer flange seal manufacturer flange seal supplier]
The expanded PTFE gasket is made of expanded PTFE plate. It maintains the performance of the expanded PTFE plate. It has outstanding effect in the sealing part where the temperature and pressure are alternating. Anti-creep. Anti-cold flow. Expanded PTFE pad The sheet can be tightly combined with the flange surface. The sealing effect is outstanding.
Outstanding performance:
> 1. Easy to disassemble and load
> 2. Can be used as an asbestos gasket. Alternative gasket for non-metallic gaskets,
> 3. It is possible to add components such as glass fiber and silica to improve the use characteristics of the gasket.
> 4. Any type of gasket can be manufactured. The manufacturing process is simple. It is easy to handle and purchase.
Technical data:
Operating temperature: -286 ~ 320 oC, pressure: 19.6MPa.
[Flange seal manufacturer flange seal manufacturer flange seal supplier]
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