Engineering ToolBox - Resources, Tools and Basic Information for Engineering and Design of Technical Applications!

Centrifugal Pumps - Capacity Modulation

Modulating pumps to adapt capacities to variable process demands.

Sponsored Links

It is often necessary to adapt pump capacities to temporary or permanent changes in the process demand.

The capacity of a centrifugal pump can be regulated either at

  • constant speed, or
  • varying speed

Capacity Regulating by Varying Speed

Pumps - modulate variable speed

Speed modulation is energy efficient since the energy to the pump is reduced with by decreasing the impeller speed.

The speed of the pump can be varied with

  • hydraulic/hydrostatic drives - hydraulic coupling between input and output shaft - speed ratio 5 to 1 is controlled by adjusting the  volume of oil in the coupling
  • mechanical drives - belt and sheave drive
  • eddy current drive/clutch - magnetic coupling transfer load torque between input and output shaft
  • variable speed drives - inverters - AC drives - adjustable frequency drives - operates by varying the frequency and voltage to the electric motor

The change in power consumption, head and volume rate can be estimated with the help of the affinity laws.

Modulating Capacity at Constant Speed

Capacity can be regulated at constant speed by

  • throttling
  • bypassing flow
  • changing impeller diameter
  • modifying the impeller

Throttling

Throttling can be carried out by opening and closing a discharge valve.

Pump - modulating capacity by throttling

Throttling is energy inefficient since the energy to the pump is not reduced. Energy is wasted by increasing the dynamic loss.

Bypassing Flow

The discharge capacity can be regulated by leading a part of the discharge flow back to the suction side of the pump. Bypassing the flow is energy inefficient since the energy to the pump is not reduced.

Changing the Impeller Diameter

Reducing the impellers diameter is a permanent change and the method can be used where the change in process demand is not temporary. The method may be energy efficient if the motor is changed and the energy consumption reduced.

The change in power consumption, head and volume rate can be estimated with the help of the affinity laws.

Modifying the Impeller

The flow rate and the head can be modulated by changing the pitch of the blades. Complicated and seldom used.

Pump Regulation and Power Consumption

Comparing power consumption:

Pumps - modulating capacity and power consumption

Sponsored Links

Related Topics

  • Pumps

    Piping systems and pumps - centrifugal pumps, displacement pumps - cavitation, viscosity, head and pressure, power consumption and more.
  • Water Systems

    Hot and cold water service systems - design properties, capacities, sizing and more.

Related Documents

Sponsored Links

Search

Search is the most efficient way to navigate the Engineering ToolBox.

Engineering ToolBox - SketchUp Extension - Online 3D modeling!

3D Engineering ToolBox Extension to SketchUp - add parametric components to your SketchUp model

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with older versions of the amazing SketchUp Make and the newer "up to date" SketchUp Pro . Add the Engineering ToolBox extension to your SketchUp Make/Pro from the Extension Warehouse !

Translate this Page

Translate this page to Your Own Language .

About the Engineering ToolBox!

Privacy Policy

We don't collect information from our users. More about

Citation

This page can be cited as

  • The Engineering ToolBox (2006). Centrifugal Pumps - Capacity Modulation. [online] Available at: https://www.engineeringtoolbox.com/pumps-discharge-regulation-d_310.html [Accessed Day Month Year].

Modify the access date according your visit.

3D Engineering ToolBox - draw and model technical applications! 2D Engineering ToolBox - create and share online diagram drawing templates! Engineering ToolBox Apps - mobile online and offline engineering applications!

Unit Converter

















































2.27.11

Sponsored Links
.