Pressure-limiting valves, pre-load valves
Pressure-limiting valves are a type of pressure control valve. They safeguard the system against excessive system pressure or limit the operation pressure.
Pre-load valves, also called sequence valves are a type of pressure control valve. They generate a largely constant pressure gradient between the inlet and outlet on the valve. In the opposite direction the flow can pass freely. In the normal position the valve has minor leakage.