Pump Types

A progressing cavity pump is a positive displacement pump. The pump is occasionally referred to as a single screw pump. The rotor, single helix, rolls eccentrically in the stator, double helix. The single helix/double helix combination creates cavities which move towards the discharge end of the pump as the rotor turns.

Features:

• Moves viscous fluids
• non-pulsating flows
• Quiet operation
• Passes solids
• Low shear pumping action
• Good for suction lift conditions

High-pressure pumps are used in almost every industry. Typical high-pressure requirements are found in boiler-feed pumps in paper mills to spray guns in car washes. High-pressure pumps are built in both centrifugal and positive displacement pump styles.

For centrifugal pumps, pressures over 100 psi or 250 ft are considered high-pressure. The high pressures are generated by multiple stages within the pump casing with each stage impeller adding more pressure to the fluid than the previous. Single stage high-pressure centrifugal pumps commonly run at 3600 rpm and beyond. High pressure centrifugal pumps are best suited for flows over 50 gpm and fluids with viscosity like water.

Most common high-pressure pumps are positive displacement style as they are more compact, use less energy and cost less to build, particularly for flow rates under 50 gpm.

Positive displacement pumps are inherently designed to generate high pressures. With each shaft rotation or cycle, a certain amount of fluid displacement occurs regardless of the discharge pressure encountered. For this reason, positive displacement high pressure pumps require a pressure relief valve in case an accidental blockage downstream occurs.

High-pressure positive displacement pumps are built in several pump types such as mechanical diaphragm, piston plunger or rotary lobe being most common. Pressures up to 1500 psi can be generated by mechanical diaphragm and up to 7000 psi using a piston plunger pump.

Vertical pumps are used when floor space is limited and typically used where the pumped fluid level is below floor grade.

As the motor is mounted atop vertical pumps, this reduces the space needed compared to a horizontal pump. Vertical pumps general construction consists of three (3) main parts: a vertically mounted motor coupled to a line shaft containing intermediate stages in-turn connected to the centrifugal wet end parts at the bottom.

Vertical pumps are available in a wide range of flows, pressures and various lengths of their column- the shaft distance from motor to wet end. They have a versatile design and can cost less than horizontals. Because the wet end is totally submersed in the fluid being pumped, no shaft seal behind the impeller is needed.

Their range of flow and pressure is almost equal to that of horizontal centrifugal pumps. The line shaft intermediate bearings are lubricated by either encapsulated grease seals or by clean external seal water fluid.

Obvious benefits include portability for these often used pumps at site locations where flooding or pond water is required to be moved. Trailer mounted pumps are usually centrifugal trash pumps capable of removing debris and solids with high flow rates and low heads. They are required simply to remove debris-laden water from one area to another.

Trash mounted trailer pumps are usually gas or diesel motor driven, as electricity is usually not available at many job sites. Trash mounted trailer pumps are almost always self-priming as the trailer is above the liquid level being pumped. Trash pumps are made of rugged construction and most accept solids of up to 3" in diameter.

The three screw design is positive displacement rotary design pump. These pumps are commonly used for machinery lubrication, hydraulic elevators, fuel oil transport, powering hydraulic machinery, refinery processes, and high pressure coolant service for machine tools. Screw pumps use an Axial flow multi-rotor positive displacement pump design. Two symmetrically opposed idler rotors act as rotating seals confining the fluid in a succession of closures of stages. The idler rotors are in rolling contact with the central power rotor and are free to float in their respective housing bores on a hydrodynamic oil film.

Features:

• Quiet operation typically noise levels are below 75 dBa at 3 ft.
• High speed capability. No rubbing parts. This allows the use of a smaller, less expensive pump.
• Delivers non-pulsating flow.
• Excellent suction lift and low horsepower consumption

Sump pumps are used to remove water that accumulates in a sump or pit. A sump or pit is needed when water accumulates below municipal sewer lines. Sump pits collect drainage water.

A sump pump removes water from the sump or pit and back to a sewer line or other location. Sump pumps generally come in two types, pedestal or submersible.

A pedestal style has its motor mounted above the sump, on top of the pump and outside of the pumped fluid. A submersible pump has its motor specialty sealed to prevent an electrical shortage, as it is totally submersed inside the liquid and down in the sump.

Submersible pumps is the name given to pumps that are designed to be immersed in the liquid they are pumping. These pumps are typically centrifugal pump and are used to empty tanks or sumps. Submersible pumps are available in manual or automatic operation and are capable of handling some solids.

Features:

• Very compact design.
• Can be used with a guide rail system for ease of maintenance.
• Are available with explosion proof motors.
• Eliminates suction lift limitations.

The term "self-priming" describes a centrifugal pump that can use an air-water mixture to reach fully primed pumping conditions. A standard centrifugal pump would air-bind under these conditions but a self-priming pump overcomes the problem by mixing air with water to create a fluid with pumping properties. The pump then gets rid of the air and moves the fluid only. Self-priming pumps are designed with a reservoir built into the casing so that the pump, once primed the first time, will always have fluid in it. It is important to note that a self-primer must have water in the casing. You cannot pull any self priming pump out of the box, turn it on, and expect it to pump. "Self priming" refers to the pump's ability to repeat the priming cycle once it is initially primed.

Features:

• Low NPSHR.
• Available in different materials of construction.
• High flow rates.
• Good for suction lift conditions.

Sanitary pumps are used to transport or meter fluids made of food or agricultural solutions that require a desired or mandated level of cleanliness. A mandated level of cleanliness is required for food health safety purposes as required by the FDA for many food processing and pharmaceutical plants.

The level of sanitation required per process or industry is determined by the government regulatory agency overseeing that specific industry. Many food-processing plants use sanitary pumps. Sanitary pumps are designed to be cleaned easily, have food grade compatible elastomers and are made of high-grade alloys such as 316 stainless steel.

Sanitary pumps are mostly centrifugal or rotary lobe positive displacement style pumps. For viscous solutions over 500 centi-poise, a sanitary rotary lobe pump is recommended. For solutions under 500 centi-poise, a less expensive sanitary centrifugal pump can be used.

The lobe type pump is a variation of a gear pump. There are many rotor styles and materials of construction available to handle a variety of fluids. Usually run at lower speeds rotary lobe pumps are capable of handling solids & highly viscous fluids. Sanitary versions are perfect for use in the food and beverage industries.

Features:

• Gentle low shear solids
• Wide viscosity range
• Mounting flexibility