High-Performance Centrifugal Pumps

Introduction

A centrifugal pump is a rotodynamic pump that uses a rotating impeller to increase the pressure and flow rate of a fluid. Centrifugal pumps are the most common type of pump used to move liquids through a piping system. The fluid enters the pump impeller along or near to the rotating axis and is accelerated by the impeller, flowing radially outward or axially into a diffuser or volute chamber, from where it exits into the downstream piping system.

Centrifugal pumps are most often associated with the radial flow type. However, the term "centrifugal pump" can be used to describe all impeller type rotodynamic pumps including the radial, axial and mixed flow variations.

Design

Oberdorfer Centrifugal pumps are of the single stage and end suction. Models use open vane style and enclosed style impellers. Centrifugals convert driver energy to kinetic energy in a liquid by accelerating it to the outer rim of a revolving impeller. Since the amount of energy given to the liquid corresponds to the velocity at the impeller's vane tip, the faster the impeller revolves (or the bigger the impeller is), the higher the velocity of the liquid at the vane tip and the greater the energy imparted to the liquid. In comparison to positive displacement devices, centrifugals are quieter and require no relief valve to protect the pumps from pressure build-up.

Application Range

Centrifugals are well suited for thin fluids and normally run at 3450 RPM speed. Because these units have large internal clearances, they can handle small impurities in the fluid. Bronze centrifugals can pump a variety of common fluids in the PH range from 4-11 and are particularly well suited for non-potable water or sea water service. The temperature limit for units equipped with buna seals is 212oF. Solvent handling and higher temperatures are possible with viton or teflon seals. Centrifugals are not well suited for viscous fluids; becoming less efficient with increased viscosities. The product portfolio of over 28 models spans a hydraulic coverage range from 2.2 GPM to 100 GPM with pressures to 58 psi (135 feet).

Pump Driver Mounting

• Close Coupled Pump Heads - pump adapters provide the required alignment to C-faced motors.
• Impeller Shimming - Since jet pump motor shaft projections can vary, pump heads are provided with impeller shim kits. In general, an air gap of 0.010” to 0.015” is recommended between the rear shroud of the impeller and the motor adapter face. Once the pump casing is mounted, check to be sure that the impeller is not rubbing against the casing. Adjust shimming as needed.
• Pedestal Pumps - Some base mount kits designed for use with Oberdorfer Bronze Gear Pumps, may also be adaptable for use with Oberdorfer Pedestal Centrifugal pumps. These kits include baseplate, coupling components, coupling guard, and hardware.

Construction

• Housings: Oberdorfer Pumps metal pump housings are made of top quality rugged cast bronze or light weight corrosion resistant cast aluminum. Shafts are corrosion resistant stainless steel or Monel.
• Bearings: Pedestal Pumps use heavy duty "lubricated for life" ball bearings suitable for pulley loads. Most of the Close Coupled pumps are designed to fit jet pump C-faced motors; relying on the motor bearings to support pump loads.
• Seals: Conventional mechanical shaft seals with carbon and ceramic faces are used. A variety of elastomers and seal styles are available. Model 170M uses a lip seal instead. Static housing sealing is accomplished with elastomeric O-ring seals or cellulose gaskets.