A positive displacement pump is a machine where chambers fill (suction) and empty (discharge) each cycle of operation. This type of pump delivers a near constant flow rate regardless of the system pressure. When using a positive displacement pump care needs to be taken to ensure the flow is not restricted causing pressures in excess of the pump or system design and/or power requirements in excess of the design. Refer to ANSI/HI 3.1-3.5, 4.1-4.6, 6.1-6.5, 8.1-8.5, 7.1-7.5 and 10.1-10.5 for complete nomenclature and definitions for positive displacement pumps. For more information, refer to our Postive Displacement pumps e-learning page.
A rotary pump is a positive displacement pump consisting of a chamber containing gears, cams, screws, vanes, plungers, or similar elements actuated by relative rotation of the driveshaft to casing, and which has no separate inlet and outlet valves. These pumps are characterized by their close running clearances. There are seven common basic types of rotary pumps identified by the type of pumping element. Relationships between these types of pumps are outlined in ANSI/HI 3.1-3.5.
The below figures are provided as a helpful illustration to rotary pumps.
A subset of rotary pumps that utilize a magnetic coupling to eliminate the need for a dynamic shaft seal. Other means of eliminating the shaft seal are axial magnetic couplings, eddy current (slip) drives and canned motors; however, the main method is magnetic coupling. These methods are discussed in ANSI/HI 4.1-4.6.
A positive displacement pump driven by power from an outside source applied to the crankshaft (power end) attached to a piston or plunger with check valves that allow filling and evacuation of champers (liquid end). There are several variations and types of reciprocating power pumps, which are provided in horizontal and vertical configurations outlined in ANSI/HI 6.1-6.5 and illustrated below.
A reciprocating positive displacement pump that is directly powered by a reciprocating (steam) engine or other compressed gas. There are several variation and types of Direct Acting (Steam) Pumps as outlined in ANSI/HI 8.1-8.5.
Controlled-volume metering pumps (also known as metering pumps, proportioning pumps, chemical injection/ feed pumps, or dosing pumps) are reciprocating positive displacement pumps typically used for the injection of chemical additives, proportional blending of multiple components, or metered transfer of a single liquid. These types of pumps are used in applications requiring highly accurate, repeatable, and adjustable rate of flow. The typical elements of a controlled-volume metering pump is described in ANSI/HI 7.1-7.5.
An air-operated pump is a positive-displacement reciprocating pump used for general liquid transfer. It is driven by means of a compressed gas (usually air) from an outside source. Air-operated pumps fall into three basic categories and are thoroughly described in ANSI/HI 10.1-10.5.