1. Submersion test

For small containers or pipes subject to low internal pressure. Fill the container or pipeline with compressed air at a certain pressure (0.4-0.5MPa) before the inspection. Then submerge in water to check the tightness, such as leakage on the right; there must be air bubbles in the water. This is also a common means of checking for leaks in bicycle inner tubes.

2. water test

Use the static pressure generated by the water’s own weight to check whether there is any leakage in the structure. Based on visual inspection, it is suitable for general welded structures that are not under pressure but require airtightness.

3. Ammonia leakage test

The purpose is the same as the kerosene leak test, and its sensitivity is higher than that of the kerosene leak test. Before the test, stick a white paper strip or bandage soaked in 5% HgNO3, aqueous solution or phenolphthalein reagent on the side of the weld that is easy to observe, and then fill the container with ammonia gas or a compressed gas with a volume fraction of 1% nitrogen. Air. If there is a leak, it will appear as a colored spot on the white strip or bandage. Those soaked in 5% HgNO3 aqueous solution are black spots, and those soaked in phenolphthalein reagent are red spots.

4. Kerosene penetration test

It is used for welded structures subject to small internal pressure and requiring a certain degree of sealing. Kerosene has strong permeability and is very suitable for tightness inspection of weld seams. Before the inspection, brush lime water on the side of the weld that is easy to observe, and brush kerosene on the other side of the weld after drying. If there are penetrating defects, kerosene spots or kerosene bands will appear on the lime layer. The observation time is 15-30min.

5. Helium mass spectrometry test

The helium mass spectrometry test is currently the most effective means of airtightness test. The helium mass spectrometer is extremely sensitive and can detect helium with a volume fraction of 10-6. Fill the container with helium before the test, and then check for leaks outside the weld of the container. The disadvantage is that helium is expensive and the inspection period is long. Although helium has a very strong penetrating power, it still takes a long time to penetrate very small gaps (such gaps cannot be detected by other means), and the leak detection of some thick-walled containers often lasts for tens of hours. Proper heating can speed up leak detection.

6. Air tightness test

An Airtightness test is a routine inspection method for boilers, pressure vessels, and other important welded structures that require airtightness. The medium is clean air, and the test pressure is generally equal to the design pressure. The pressure should be increased step by step during the test. After reaching the design pressure, apply soapy water on the outside of the weld or sealing surface and check whether the soapy water bubbles or not. Because the airtightness test has the risk of explosion, it should be carried out after the water pressure test is passed.