The main purpose of the air tightness experiment of the bellow expansion joint is to detect the air tightness and air tightness of the compensator to ensure that the compensator does not leak under working conditions. The airtightness test pressure is generally double the planned pressure.

1. Apply foaming agent to joints such as welds and flanges. If the bellows compensator leaks, blisters will occur;

2. Regarding the smaller size bellow expansion joint, usually immerse it in a pool, and check whether the bellow expansion joint is tight according to whether there is air bubbles;

3. Paste a test paper 2mm wider than the welding seam on the outer wall of the bellow expansion joint, observe whether there is any discoloration, and judge whether there is leakage. For example, test paper impregnated with phenolphthalein reagent will appear red when in contact with it.