Cracking pressure is defined as

Cracking pressure is defined as

• A. Full flow pressure
• B. Cracking pressure
• C. Operating pressure
• D. Downstream pressure

Answer: (B)

Cracking pressure is the minimum pressure at the valve inlet needed to overcome the closing force (such as the seal and any spring) so the valve begins to open and allow flow. Before reaching this threshold, the valve stays closed and holds back the upstream pressure. Once that pressure is reached, flow starts and the valve opens further as pressure continues to rise, depending on the valve design. This is different from full flow pressure (when the valve is fully open and flow is at its maximum), operating pressure (the normal running pressure of the system), and downstream pressure (the pressure on the outlet side). For example, a relief valve with a cracking pressure of 100 psi will not vent until the inlet pressure reaches about 100 psi, at which point it begins to open to limit further pressure rise.

Cracking pressure is the minimum pressure at the valve inlet needed to overcome the closing force (such as the seal and any spring) so the valve begins to open and allow flow. Before reaching this threshold, the valve stays closed and holds back the upstream pressure. Once that pressure is reached, flow starts and the valve opens further as pressure continues to rise, depending on the valve design. This is different from full flow pressure (when the valve is fully open and flow is at its maximum), operating pressure (the normal running pressure of the system), and downstream pressure (the pressure on the outlet side). For example, a relief valve with a cracking pressure of 100 psi will not vent until the inlet pressure reaches about 100 psi, at which point it begins to open to limit further pressure rise.