Page 208 - Valve Selection Handbook
P. 208
Pressure Relief Valves 195
Figure 5-32. Force/Lift Diagram Displaying the Operational Behavior of
Conventional Spring-Loaded Pressure Reliet Valves that Pop Open Fully in One
Stroke (Typical Only).
When rising system pressure reaches the set pressure at operating
point A, the valve will modulate open until reaching the operating point
B. At this point, lifting and closing forces are in balance. At the com-
mencement of any further pressure rise, the lifting force grows faster
than the spring force, causing the valve to pop open fully in one stroke to
operating point C. As the system pressure rises further as permitted by
the applicable code of application, the valve reaches its rated capacity at
operating point D.
