Many manufacturers—including those in the food and beverage, personal care, cosmetics, dairy or meat processing industries—benefit from a positive displacement pump. These pumps maintain a constant volume and positively displace any liquid—such as juice, fats, oil, gelatin, mayonnaise, syrup, creams, milk products, automobile paint and polymers—from a fixed-volume container.
Definition of Positive Displacement Pumps
We like The Engineering Toolbox’s definition: “Positive Displacement Pumps use an expanding cavity on the suction side and a decreasing cavity on the discharge side. Liquid flows into the pump as the cavity on the suction side expands, and the liquid flows out of the discharge as the cavity collapses. The volume is a constant given each cycle of operation.”
These pumps are divided into two main groups: rotary and reciprocating pumps.
Benefits of Positive Displacement Pumps
There are many benefits of positive displacement pumps for varying applications. Below we outline the main reasons many operations choose to use them. For more information, we recommend taking the Hydraulic Institute‘s new Positive Displacement (PD) Pumps: Fundamentals, Design and Applications e-Learning course.
- PD pumps are sometimes called constant-volume pumps because they maintain a constant speed and flow. Even if the system pressure varies, the flow remains constant.
- PD pumps can handle a variety of fluid types: high, low and variable viscosity; shear sensitive fluids; solids; and liquids with a high percentage of air or gas entrainment.
- Their capacity is not affected by the operation pressure.
- They are excellent for applications with flows below 100-gpm and above 100-psi.
- They can be 10 to 40 points more efficient than centrifugal pumps when handling viscous fluids.
- PD pumps are able to self-prime.
- They can be designed as a sealless pump.