The pressure testing of a heat exchanger involves both hydraulic and pneumatic tests.
In principle, the primary method for pressure testing is the hydraulic test, commonly referred to as the hydrostatic test when clean water is the testing medium. If other liquids are utilized, they must be non-hazardous, and their temperature should remain below the boiling point. When conducting a hydraulic test with a flammable liquid, the test temperature must be below the liquid's flash point. Additionally, the test site should be free of nearby fire sources, and appropriate firefighting equipment should be on hand.
In cases where the pressure vessel cannot be completely filled with liquid due to structural or support constraints or when the operating conditions disallow residual test liquid, an air pressure test can be performed according to the design drawings. For instance, this is applicable to large spherical tanks, cement foundations, pillars, and other situations where the container volume is too large to bear the weight of water. In situations with complex structures, where a hydraulic test may not adequately test every part's pressure, the air pressure test is preferred. The hydrostatic test may cause structural damage due to the load considerations in the initial design, or the test medium may lead to corrosion damage to the container's shell wall and inner lining.
