What does "BD 6" refer to on a PSV rating plate?

"BD 6" on a Pressure Safety Valve (PSV) rating plate refers to the blowdown range, which is an important parameter for the valve's operation. The blowdown range indicates the difference between the set pressure, at which the valve opens to relieve pressure, and the reseat pressure, at which the valve closes again after relieving the excess pressure.

Understanding the blowdown range is critical for safety and efficiency in systems involving pressure relief, as it helps ensure that the valve operates correctly under varying conditions. Maintaining a proper blowdown prevents the valve from rapidly cycling, which can lead to wear and tear, and helps maintain system pressure stability.