The metal compensator expansion joint used in the engineering pipeline does not all need to be air-tight test, in most cases, the metal compensator expansion joint will be air-tight test before leaving the factory, so as to check the fineness and tightness of the weld, and ensure that the metal compensator expansion joint is installed without leakage before normal operation.

Q: Under what circumstances does the metal compensator expansion joint need to be tested for air tightness? What problems should be paid attention to in the process of air tightness test?

Answer: According to the regulations, as long as the medium of the pipeline activity is flammable and explosive or moderately damaged, and when operating under vacuum conditions, the vacuum degree is greater than 0.085MPA or there are special requirements for leakage, it is necessary to carry out the air tightness test of the metal compensator expansion joint installed.

In the process of air tightness test, the following points should be noted:

1. Add 1% ammonia in the experimental gas medium, paste a test paper 2Omm wider than the weld on the outer wall of the metal compensator expansion joint, and investigate whether there is color change to determine whether it is leakage. For example, test paper impregnated with phenolphthalein turns red when exposed to ammonia.

2, in the weld, flange and other connecting parts of the foaming agent (such as the proportion of 10% soapy water) to check. If the metal compensator expansion joint leaks, there will be bubbling.

3, submerged view. For the metal compensator expansion joint of small scale, it is generally sunk in the pool to check, according to whether there is no bubble emerging, to determine whether the metal compensator expansion joint is tight. In the metal compensator expansion joint for air tightness test, there should also be appropriate safety protection methods.