pressure relief valves are intended for a different role than their safety counterparts. A pressure relief valve is intended to vent excess pressure from the system. These valves are, in a sense, a type of pressure regulator. When the pressure exceeds a preset level, the relief valve opens and bleeds down the system. These valves normally have an external adjustment so that the cracking pressure may be tuned to match any given application. The poppets of these valves are generally designed with a tapered plug so that they only bleed the excess pressure and reclose at their set point. Pressure relief valve adjustments can be found in a variety of forms, from a threaded cap and lock nut to a micrometer barrel. These valves usually carry some type of manual actuator.