Gaskets will leak after long-term use of the pipeline. When replacing the gasket, it is difficult to open the connecting flange. The simple self-made tool shown in Figure 8-6 can be used to force the two flanges apart. The number and diameter of the bolt holes on the adapter flange and the specifications of the connecting bolts are specified in the relevant adapter flange standards. The flange bolt holes are generally 2 to 3mm larger than the diameter of the bolt or stud.

1. Reasons why the flange connection is not tight:
The sealing surfaces of the two connected flanges are not parallel;
Defects on the sealing surface of the adapter flange;
After the pipeline is put into operation, the second tightening of the flange bolts is not carried out;
Gasket failure: ① improper material selection; ② too thick gasket, punctured by high-pressure medium; ③ gasket wrinkled, cracked or broken; ④ gasket failure after long-term use;
After the pipeline is put into operation, the second tightening of the flange bolts is not carried out.

2. Elimination method:
Hot bending the pipe on the flange side: On the side that needs to be bent, use an oxyacetylene flame to heat a strip with a length equal to 3 times the diameter and a width not greater than the radius, and then bend the pipe to seal the two flanges face parallel;
The pits and radial scratches with a depth of no more than 1mm shall be processed on a lathe; for the defects with a depth of more than 1mm in the connecting flange, electric welding shall be used to repair the defect surface after cleaning, and then cleaned, scraped or ground with a hand file. ;
After the pipeline is put into operation, when the temperature and pressure rise to a certain value, properly tighten the bolts, and check the bolts as soon as possible in the first few days after operation;
Replace the new gasket of the adapter flange, the gasket material should be selected according to the type of medium and pressure; the gasket thickness of the gasket meets the requirements; the gasket of qualified quality is modified; the new gasket of the adapter flange is replaced regularly;
After the pipeline is put into operation, when the temperature and pressure rise to a certain value, the bolts should be properly tightened, and the tightening of the bolts should be checked frequently during the first few days of operation.