Which statement about diaphragm pumps is true?

• A. They are never used for chemical dosing
• B. They require continuous lubrication
• C. They cannot handle viscous fluids
• D. They protect the pumping mechanism from the material being pumped

Answer: (D)

Diaphragm pumps work by flexing a flexible diaphragm to create a sealed pumping chamber, with a drive mechanism located on the other side of a barrier. That barrier—the diaphragm and its seals—keeps the pumped liquid away from the mechanical parts that drive the pump. Because of this separation, the internal pumping mechanism is protected from whatever is in the fluid, whether it’s corrosive, abrasive, or viscous. This isolation makes diaphragm pumps especially suitable for chemical dosing and for handling challenging liquids without corroding or fouling the moving drive components.

That protective isolation is the core reason this statement is true. They are indeed used for chemical dosing and can handle a range of fluids, including viscous ones. The other points aren’t universal truths about diaphragm pumps—some designs require lubrication for moving parts, but the pumped fluid generally doesn’t need continuous lubrication, and many models are well-suited to viscous fluids, so the statement about never, or always, needing those conditions isn’t accurate.