In the context of valves, particularly pressure relief valves, the term "bench set" refers to the pressure at which the valve is set or adjusted during testing or calibration while it is removed from the system or "on the bench." It represents the pressure at which the valve is designed to open and begin relieving excess pressure from the system to protect it from overpressure conditions.

During the bench set process, the pressure relief valve is typically removed from the system and placed on a test bench or fixture specifically designed for testing and calibration purposes. The valve is then subjected to a controlled pressure source, such as a hydraulic pump or air pressure system, which gradually increases the pressure applied to the valve until it reaches the desired set pressure.

Once the pressure relief valve reaches the specified bench set pressure, it is adjusted or calibrated as needed to ensure that it opens and begins relieving pressure at the correct set point. This adjustment may involve modifying the tension of the valve spring, adjusting the position of the spring seat, or other means depending on the type and design of the valve.

After the bench set process is completed and the valve is calibrated to the correct set pressure, it can be installed back into the system with confidence that it will operate as intended and provide reliable overpressure protection.

In summary, the bench set refers to the process of setting or adjusting the pressure relief valve to the desired set pressure while it is removed from the system and tested on a bench or test fixture. It is a critical step in ensuring the proper operation and performance of pressure relief valves in protecting systems from overpressure conditions.