This example shows a test circuit built to check the pressure-flow characteristic of a direct-acting pressure-relief valve. The valve model is a subsystem built of an orifice with roundholes, translational converter, preloaded spring, and a hardstop.
The pump, which is simulated with an ideal flow rate source, delivers fluid to a system through an initially-opened variable orifice. As the orifice gets closed, pressure gradually builds up and eventually reaches the setting of the pressure-relief valve. At this pressure, the valve starts diverting flow to a tank and maintains preset pressure at the pump outlet. As the orifice is opened again, the pressure-relief valve is closed and the entire flow passes through the variable orifice.