Differential Set Pressure

Differential set pressure, also called delta P or delta pressure, is the difference in pressure between two points in a system at which a pressure relief valve or pressure regulating valve is designed to operate.  This parameter is essential for determining when these valves should start to open or close in response to changes in pressure.

In the context of pressure relief valves and safety valves

• The differential set pressure is the difference between the pressure at which the valve starts to open (cracking pressure) and the pressure at which the valve fully opens to allow fluid to escape and relieve the excess pressure.
• For example, if a pressure relief valve has a cracking pressure of 100 psi and a full lift pressure of 110 psi, the differential set pressure is 10 psi.

In the context of pressure-regulating valves

• The differential set pressure is the difference between the inlet pressure (the pressure upstream of the valve) and the outlet pressure (the pressure downstream of the valve) at which the valve starts to open or close to maintain a consistent pressure downstream.
• For example, if an upstream pressure of 150 psi and a downstream pressure of 130 psi are required to maintain the desired pressure downstream, the differential set pressure is 20 psi.

The differential set pressure is a crucial parameter in valve design and operation, as it determines the range within which the valve remains closed or fully open, and when it transitions between these states.  Properly setting the differential set pressure ensures that pressure relief valves respond appropriately to prevent overpressurization, and pressure regulating valves maintain the desired pressure downstream.  In industrial applications, especially in sectors involving hazardous materials or critical processes, understanding and accurately configuring the differential set pressure is vital for maintaining the safety, efficiency, and reliability of the systems in which these valves are employed.