A double diaphragm pump functions as a type of positive displacement pump, designed to move various fluids. It relies on two flexible diaphragms, which work in a coordinated, reciprocating motion, powered by compressed air. Its primary role involves the efficient transfer of liquids, slurries, or even mixtures containing solids.
Essential Components
A double diaphragm pump includes several components for fluid transfer. The core elements are two flexible diaphragms, often made from rubber or specialized elastomers for chemical compatibility. These diaphragms connect via a common shaft, ensuring they move in unison. A central air valve directs the compressed air that drives the diaphragms.
Fluid enters and exits through inlet and outlet manifolds. Check valves, typically ball or flap valves, are positioned within these manifolds. These valves control fluid direction, preventing backflow and ensuring unidirectional movement.
The Pumping Mechanism
The pump operates through a continuous, alternating suction and discharge cycle. Compressed air, directed by the central air valve, pushes one diaphragm outward, pressurizing the fluid in its chamber and forcing it out through the outlet check valve. Simultaneously, the common shaft pulls the opposite diaphragm inward, creating a vacuum in its fluid chamber.
This vacuum draws new fluid into the chamber through the inlet manifold, causing the inlet check valve to lift. When the outward-moving diaphragm completes its stroke, the air valve automatically shifts. This redirects compressed air to the newly filled chamber, reversing the diaphragms’ roles and ensuring continuous fluid transfer.
Air Valve Operation
The central air valve acts as the control system for the double diaphragm pump, orchestrating its reciprocating motion. This valve receives compressed air and precisely directs it to one side of the diaphragms while simultaneously venting air from the opposing side. This air distribution drives the alternating movement.
As compressed air pushes one diaphragm, the air valve ensures that the air behind the other diaphragm is exhausted to the atmosphere. This venting allows the pulled diaphragm to move freely inward, creating the necessary vacuum for fluid intake. The air valve automatically switches the airflow when a diaphragm completes its stroke.
Operating Characteristics
Double diaphragm pumps handle a wide range of fluids, including highly viscous materials, abrasive slurries, and liquids containing solids, without causing damage. This is due to the diaphragms acting as a barrier, isolating the fluid from moving mechanical parts, and the pump’s large internal clearances.
These pumps are self-priming, drawing fluid without prior suction line filling. They can also run dry indefinitely without sustaining damage. The gentle, low-shear pumping action makes them suitable for transferring shear-sensitive fluids, preserving delicate materials. The absence of mechanical seals eliminates potential leakage points, enhancing their reliability.