1. Leakage location and condition The connecting
steel flange bolts on both sides of the DN150 valve body leak. Since the steel flange connection gap is extremely small, it is impossible to inject sealant through the gap to eliminate the leakage. The leakage medium is steam, the temperature of the leakage system is 400-500°C, and the system pressure is 4MPA.
2. Sealing construction method According to the on-site survey of the leakage site, in order to achieve effective sealing, the fixed fixture method is used to contain the leakage point to form a sealing cavity, and the sealant is injected to eliminate the leakage.
A. Fixture design
(1) Determine the structure of the fixture
①Contain the leakage point, and establish a sealing cavity between the valve body steel flange and the pipe steel flange connection nipple flange. In order to prevent re-leakage at the potential leak between the valve body and the steel flange due to pressure suppression, an annular cavity is provided to inject glue at the joint between the fixture and the outer edge of the valve body steel flange.
②During the injection process of steel flanges with different diameters, the fixture is prone to displacement to the small-diameter steel flange side, so the tooth-shaped contact clamping limit measure is adopted.
B. Sealant selection and dosage estimation
(1) Sealant selection According to the temperature of the leakage system and the characteristics of the leakage site, TXY-18#A type sealant is used. The sealant has excellent performance in temperature resistance, medium resistance and injection process, and it is easy to establish a uniform and dense sealing structure, and the sealing can maintain long-term stability.
(2) Quantity estimation: 4.5KG of sealant is required for one side leakage point.
C. Construction operation
(1) Fixture installation, due to the contact of the tooth shape, the inner diameter of the tooth tip is small. During installation, it is necessary to knock the outer wall of the fixture in circles to deform the tooth end and clamp the limit.
(2) After the injection operation is completed, the fixture, valve body and steel flange annular cavity are injected into the sealing cavity, and then the intermediate cavity is injected. During the injection process, pressure should be applied evenly, and attention should be paid to refilling and pressing to prevent stress relaxation.
(3) After the sealant is cured, after observing the effect, carry out local replenishment and compaction to prevent stress relaxation, and then close the injection hole.
