An Australian positive displacement pump pumps fluids by enclosing a volume that is fixed repeatedly and then moving it through the system mechanically. The pumping action of this pump is cyclic and can be driven by screws, pistons, rollers, gears, vanes and diaphragms.
How do PD pumps work?
Although there are different types of PD pump designs, most of these pumps can be placed into two main categories: rotary and reciprocating pumps.
Reciprocating PD pumps
A reciprocating PD pump works by the repeated movement of back and forth of the plunger, diaphragm or piston, the cycles are known as reciprocation. In piston pumps, the first strop creates a vacuum and opens up an inlet valve and then closes the outlet valve. This draws fluid into the chamber. As the motion reverses, the inlet valve is closed and the outlet valve is opened allowing the fluid in the piston chamber that should be discharged.
The bicycle pump is a simple example that uses this method. Piston pumps can be double acting with the outlet and inlet valves on both sides of the piston. Whilst the piston is usually in suction on one side, it is usually in compression on the other. Radial versions are typically used for industrial applications.
Plunger pumps also operate in a similar way. The fluid moved by the piston pump depends on the volume of the cylinder. In plunger pumps, it depends on the size of the plunger. The seal around the plunger or piston is very important as it maintains the pumping actions. This happens to avoid leaks. A water solutions company usually makes the plunger pump seal easier to maintain because it is stationary at the top of the cylinder of the pump whereas the seal around the piston moves repeatedly moving up and down in the chamber of the pump.
On the other hand, the diaphragm pump uses a membrane that is flexible and a plunger or piston to move the fluid. By expanding the diaphragm, the pumping chamber’s volume is increased and the fluid is drawn into the pump. A diaphragm pump reduces the volume and expels some fluid. The diaphragm pumps have the benefit of being hermetically sealed systems and this makes them ideal for the pumping of hazardous fluids.
Reciprocating pumps have a cyclic action that creates the discharge with the acceleration of the fluid during the compression phase of pumping and slowing at suction phase and this can cause soma damaging vibrations in your installation and some form of smoothing or damping is employed. You can minimise pulsing by using two pistons, diaphragms or plungers with one of its compression phases while the other is in suction.
The predictable and repeatable action of reciprocating pumps makes them great for applications where accurate dosing or metering is needed. When you alter the stroke rate or length, it is possible to provide measuring quantities of the pumped liquid. A rotary Australian positive displacement pump uses the action of rotating gears or cogs to transfer fluids, rather than the forward and backwards motion of these pumps.