In terms of propane pump ratings, _____ is the difference between the pressure at the outlet side of the pump and the pressure at the inlet side of the pump.

• A. Pressure drop
• B. Volume
• C. Flow rate
• D. Differential

Answer: (D)

When you look at two pressures on opposite sides of a device, the difference between them is called the differential pressure. In a propane pump, the rating describes the pressure rise the pump provides from inlet to outlet, i.e., outlet pressure minus inlet pressure. For example, if the inlet is 60 psi and the outlet is 110 psi, the differential is 50 psi. This term is used because it neutrally describes the change in pressure across the pump, regardless of direction, whereas a pressure drop would imply a loss of pressure through a component. Volume and flow rate are about how much fluid moves and how fast, not about the pressure difference across the pump. So the term that best fits the difference between outlet and inlet pressures is differential.