1、 Leakage position and condition: the connecting flange bolts on both sides of DN150 valve body leak. Because the flange connection gap is very small, it is impossible to eliminate the leakage by injecting sealant into the gap. The leakage medium is steam, the leakage system temperature is 400 ~ 500 ℃, and the system pressure is 4MPa.
2、 Sealing construction method according to the field survey of the leakage part, in order to achieve limited sealing, the fixed fixture method is used to contain the leakage point, form a sealing cavity, and inject sealant to eliminate the leakage.
1. Fixture design
(1) Determination of fixture structure
① Contain the leakage point and establish the sealing cavity between the valve body flange and the pipe flange connecting nipple flange. In order to prevent re leakage at the potential leakage of the gap between the valve body and the flange due to pressure holding, an annular cavity shall be set at the coincidence between the clamp and the outer edge of the valve body flange for glue injection.
② During the agent injection process of reducing flange, the fixture is easy to shift to the side of small diameter flange, so the limit measure of tooth contact clamping is adopted.
(2) The fixture drawing and relevant dimensions of fixture structure for construction are shown in Figure 1.
2. Sealant selection and dosage estimation
(1) The sealant shall be txy-18#a sealant according to the temperature of the leakage system and the characteristics of the leakage part. The sealant has excellent temperature resistance, medium resistance and injection process performance, is easy to establish a uniform and dense sealing structure, and the sealing can be kept stable for a long time.
(2) It is estimated that 4.5kg sealant is required for unilateral leakage point.
3. Construction operation
(1) During fixture installation, due to the tooth contact, the inner diameter of the tooth tip is small. During installation, the outer wall of the fixture needs to be knocked around the ring to deform the tooth end and clamp the limit.
(2) After the agent injection operation is completed, the clamp, valve body and flange annular cavity shall be injected into the sealing cavity, and then the agent injection in the middle cavity shall be carried out. The agent injection process shall be balanced, and pay attention to supplementary injection and compression to prevent stress relaxation.
(3) After the sealant is cured, conduct local supplementary injection and compression after effect observation to prevent stress relaxation, and then close the injection hole.
Post time: Dec-07-2021