How to deal with flange leakage sealing method

First, the leakage location and condition. The bolts connecting the flanges on both sides of the DN150 valve body are leaking. Due to the extremely small gap between the flange connections, it is impossible to eliminate the leakage by injecting sealant through the gap. The leakage medium is steam, the leakage system temperature is 400-500℃, and the system pressure is 4MPA.
Second, the sealing construction method is based on the on-site survey of the leakage location. To achieve effective plugging, 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. Clamp design
(1) Determination of the clamp structure:
① Contain the leakage point and establish a sealing cavity between the valve body flange and the pipeline flange connection short flange. To prevent the potential leakage of the gap between the valve body and the flange due to the pressure, an annular cavity is set at the joint between the clamp and the outer edge of the valve body flange for injection.
② During the injection process of the different diameter flange, the clamp is easy to move toward the small diameter flange side, so the tooth contact clamping limit measure is adopted.

2. Sealant selection and dosage estimation
(1) Sealant selection According to the temperature of the leaking system and the characteristics of the leaking part, TXY-18#A type sealant is used. This sealant has excellent heat resistance, medium resistance, and injection process performance, and is easy to establish a uniform and dense sealing structure, and the seal can remain stable for a long time.
(2) Dosage estimation: 4.5 kg of sealant is required for a single-side leak point.

3. Construction operation
(1) Fixture installation. Due to the tooth contact, the inner diameter of the tooth tip is small. During installation, it is necessary to knock the outer wall of the fixture in a circle to deform the tooth end and clamp it.
(2) After the injection operation is completed, the fixture, valve body, and flange annular cavity are injected into the sealing cavity, and then the intermediate cavity is injected. The injection process should be balanced and pressure should be applied, and attention should be paid to refilling and compacting to prevent stress relaxation.
(3) After the sealant is cured, after observing the effect, local refilling and compacting are carried out to prevent stress relaxation, and then the injection hole is closed.