What type of pump may be damaged if started with the discharge valve closed?

A positive displacement pump may be damaged if started with the discharge valve closed because of its operating principle. Unlike centrifugal pumps, which rely on velocity and kinetic energy to move fluid, positive displacement pumps move a fixed amount of fluid with each cycle or stroke. When the discharge valve is closed, the pump continues to push fluid into a contained space, which can cause the pressure to rise significantly. This high pressure can lead to mechanical failure, seal damage, or even catastrophic failure of the pump components.

In contrast, centrifugal pumps typically handle excess pressure by recirculating fluid within the pump itself or by allowing some fluid to backtrack, making them less susceptible to damage under similar conditions. Submersible pumps, which are designed to operate underwater and often incorporate some form of protection against dry running, also have a different mechanism that mitigates damage in this scenario. Diaphragm pumps may have some capacity to handle closed discharge situations without immediate damage, depending on their design and the materials used. However, positive displacement pumps are particularly vulnerable to pressure overloads when discharge is obstructed.