Sealing treatment for leakage of stainless steel flange

 Leakage position and condition The bolts connecting the stainless steel flange on both sides of the DN150 valve body are leaking. Because the connection gap of the stainless steel flange is very small, it is impossible to inject sealant into the gap to eliminate the leakage. The leakage medium is steam, the leakage system temperature is 400~500 ℃, and the system pressure is 4MPA.

　　The sealing construction method is based on the site survey of the leakage site. In order to achieve limited sealing, the fixed clamp method is used to contain the leakage point to form a sealing cavity, and the sealant is injected to eliminate the leakage.

　　1. Fixture design

　　(1) Determination of fixture structure

　　① Contain the leakage point, and establish the sealing chamber between the stainless steel flange of the valve body and the stainless steel flange of the pipe connection nipple. In order to prevent re-leakage at the potential leakage of the gap between the valve body and the stainless steel flange due to pressure holding, an annular cavity is set at the junction of the clamp and the outer edge of the stainless steel flange of the valve body.

　　② During the injection process of reducing diameter stainless steel flange, the fixture is easy to move towards the side of small diameter stainless steel flange, so the limit measure of tooth contact clamping is adopted.

　　2. Sealant selection and dosage estimation

　　(1) TXY-18 # A sealant is selected according to the temperature of the leakage system and the characteristics of the leakage location. The sealant has excellent temperature resistance, medium resistance and injection process performance, is easy to establish uniform and dense sealing structure, and the sealing can maintain long-term stability.

　　(2) The amount of sealant is estimated to be 4.5KG at the leakage point on one side.

　　3. Construction operation

　　(1) During fixture installation, due to the tooth shape contact, the inner diameter of the tooth tip is small. During installation, it is necessary to knock the outer wall of the fixture around the ring to cause the tooth end deformation and clamp the limit.

　　(2) After the injection operation is completed, the clamp, valve body and stainless steel flange annular cavity are injected into the sealing cavity, and then the intermediate cavity is injected. During the injection process, the pressure should be balanced, and attention should be paid to refilling and compaction to prevent stress relaxation.

　　(3) After the sealant is cured, after the effect is observed, local supplementary injection and compaction shall be carried out to prevent stress relaxation, and then the injection hole shall be sealed.