When should relief valves be used in pump systems?

Relief valves are essential components in pump systems, particularly for positive displacement pumps. These pumps can generate high pressures because they move a fixed volume of fluid with each stroke or rotation. Unlike centrifugal pumps, which are generally governed by the system's pressure and flow characteristics, positive displacement pumps can continue to push fluid against a closed valve situation, leading to a potentially dangerous increase in pressure.

The use of relief valves in these systems is critical for maintaining safe operating conditions. When the pressure exceeds a predetermined level, the relief valve opens and allows some fluid to bypass, thus protecting the pump and associated piping from damage due to overpressure. This prevents equipment failure and hazardous situations that might arise from excessive pressure.

While relief valves can be useful in some scenarios for centrifugal pumps, their primary necessity is in positive displacement applications where the risk of pressure increases is significant. Hence, stating that relief valves should be used for all types of pumps, or just in centrifugal or gas pumping contexts, overlooks the vital role they play specifically in positive displacement pumps.