Air-Operated Pumps

10.1 Types and nomenclature

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. Where “air” is used throughout this document, it should be taken to mean any compressed gas, but usually air.

Air-operated rotodynamic and rotary pumps are not included in this standard.

10.1.1 Types of air-operated pumps

Air-operated pumps fall into the basic types shown in Figure 10.1 and described below.

10.1.1.1 Air-operated diaphragm pump

An air-operated diaphragm pump contains a single diaphragm or double diaphragms connected to a reciprocating shaft in which one side of the diaphragm is in contact with the liquid being pumped and the other side is in contact with the compressed air. A typical air-operated double diaphragm (AODD) pump configuration is shown in Figure 10.2.

10.1.1.2 Air-operated bellows pump

An air-operated bellows pump contains two bellows connected to a reciprocating shaft in which one side of the bellows is in contact with the liquid being pumped and the other side is in contact with the compressed air. A typical configuration is shown in Figure 10.3.

10.1.2 Configuration of pumping devices

10.1.2.1 Single-acting pump (simplex)

Contains one diaphragm or bellows driven by one shaft.

10.1.2.2 Double-acting pump (duplex)

Contains two diaphragms or bellows driven by one connecting shaft.

10.1.3 Nomenclature

The nomenclature and definitions in these standards were prepared to (1) provide a means for identifying the various pump components covered by these standards, and (2) to serve as a common language for all who deal with this type of equipment.

The following definitions and drawings illustrate typical constructions of air-operated pump components, but do not necessarily represent recommended designs.

Variations in design may exist without violating the intent of these standards.

10.1.3.1 Air-distribution system

The air-distribution system consists of all parts within the pump required to operate the pump from the air inlet to the air exhaust. Various air-distribution system designs exist, but all perform the same basic function.

10.1.3.2 Air chamber

The air chamber houses the pressurized air that causes the diaphragm or bellows to be displaced.

10.1.3.3 Diaphragm assembly

10.1.3.3.1 Diaphragm

The diaphragm provides for separation of the process liquid and the compressed-air power source. To perform adequately, the diaphragm should be of sufficient thickness and of appropriate material to prevent degradation or permeation in specified process liquid. Various diaphragm materials and configurations exist, but all perform the same basic function.

10.1.3.3.2 Inner and outer diaphragm plates

The inner and outer diaphragm plates provide a means to support and to connect the diaphragm to the reciprocating shaft and aid in sealing the liquid side from the air side of the diaphragm.

10.1.3.4 Bellows assembly

10.1.3.4.1 Bellows

The bellows provide for separation of the process liquid and the compressed-air power source. Various bellows materials and configurations exist, but all perform the same basic function.

10.1.3.4.2 Bellows end caps and connecting rods

The bellows end caps and connecting rods provide a means to connect the bellows to the center block.

10.1.3.5 Wetted path housings

10.1.3.5.1 Liquid chamber

The liquid chamber is filled with the liquid being pumped during the suction stroke and empties during the discharge stroke. It is separated from the compressed gas by the diaphragm or bellows.

10.1.3.5.2 Inlet manifold

The inlet manifold contains the suction passageways of the pump. The inlet manifold for an air-operated reciprocating pump is typically at the bottom of the pump for configurations with ball check valves, but can be at the top for some configurations containing check valves other than ball check valves.

10.1.3.5.3 Discharge manifold

The discharge manifold contains the discharge passageways of the pump. The discharge manifold for an air-operated reciprocating pump is typically at the top of the pump for configurations with ball check valves but can be at the bottom for some configurations containing check valves other than ball check valves.

10.1.3.6 Check valves

An air-operated pump uses suction and discharge check valves to produce directional flow of process liquid in the liquid chamber assembly. Various configurations of check valves are available for specific applications. The most common types are shown in Figure 10.4.