What is the preferred fluid in hydrostatic testing of boilers and pressure vessels?

Water is preferred in hydrostatic testing of boilers and pressure vessels primarily due to its availability, cost-effectiveness, and favorable physical properties. When conducting hydrostatic tests, the main goal is to ensure the integrity and strength of the equipment being tested. Water is incompressible, which means that its use can create a uniform pressure across the surface of the boiler or vessel, allowing for accurate detection of leaks or weaknesses.

Additionally, using water allows for a safe test environment. In case of a failure during the testing process, water poses significantly less risk compared to gases, which can expand rapidly and cause violent ruptures or explosions. Water also has a high thermal capacity, making it suitable for applications involving temperature fluctuations.

Other fluids like nitrogen or compressed air are gases that are more compressible and can lead to hazardous situations if a leak occurs. Hydraulic oils, while also incompressible, can pose environmental concerns and may impact testing results if contaminants are introduced. Overall, water remains the standard due to its balance of safety, effectiveness, and practicality in pressure testing applications.