What type of valves should be removed before performing a hydrostatic test?

Removing pressure relief valves before performing a hydrostatic test is essential for ensuring safety and the integrity of the test results. Pressure relief valves are designed to open at a specific pressure to prevent excessive pressure buildup in a system. If these valves remain installed during a hydrostatic test, they could inadvertently open due to the test pressure, leading to inaccurate readings and potential safety hazards. Their presence could cause the test to fail or reveal weaknesses in the system that are not representative of actual operating conditions.

In contrast, while control valves, isolation valves, and check valves play important roles in a piping system, they do not have the same critical safety function during a hydrostatic test as pressure relief valves do. Control valves manipulate flow, isolation valves control the flow of fluid into or out of a section of piping, and check valves prevent backflow. However, their operation is not intended to relieve pressure and therefore does not pose the same risks during the testing process. This is why it is particularly crucial to address pressure relief valves when preparing for such tests.