Control principles for variable speed pumping:Methods of controlling a rotodynamic pump

Methods of controlling a rotodynamic pump

The methods of controlling a pump for varying duty are covered in more detail in other sections, but as an introduction to control principles a summary is presented.

When the user wants to reduce the flow in a process, valve control (see Figure 8.1) can be used either to directly throttle, or control a bypass (see Figure 8.2). Alternatively, speed control (see Figure 8.3) can be applied using a VSD.

Valve control will effectively reduce the flow, however, the consumed energy is often significantly lower if speed control is used. On-off control can be used to vary pumped volume in systems where an intermittent flow

VARIABLE SPEED PUMPING-0757

VARIABLE SPEED PUMPING-0758

is acceptable . These systems often require a storage facility.

If there is a static head in the pumping system, a substantial amount of energy may be used for lifting, compared with the energy required to overcome the friction in the pipes. Only small speed variations are possible and although energy savings can still sometimes be achieved, applications must be individually evaluated.

In many pumping applications several pumps are used in parallel to produce the required flow when the flow demand varies substantially (typically water and waste water systems) . See Section 4 .2.2.3.

Related posts:

Case studies:Variable speed drive on a circulating pump in a batch process
Pumps:Pumps in series switched to meet demand
Vacuum and Low Pressure:Vacuum pumps
System selection considerations:Pipeline conveying capacity.
Optimizing and up-rating of existing systems:Optimizing existing systems
Review of pneumatic conveying systems:Staged systems and Dual vacuum and positive pressure systems.
Conveying characteristics:The determination of conveying characteristics
Hydraulic fluids:Fire-resistant fluids
Pressure measurement.
INTRODUCTION AND OVERVIE:A NOTE ON DIMENSIONS AND UNITS
PROPERTIES OF PURE SUBSTANCES:PROPERTY TABLES
POWER AND REFRIGER A TION CYCLES:AIR-STANDARD ASSUMPTIONS
POWER AND REFRIGER A TION CYCLES:THE REVERSED CARNOT CYCLE
RADIATION HEAT TRANSFER:RADIATION SHIELDS AND THE RADIATION EFFECTS
NATURAL CONVECTION:EQUATION OF MOTION AND THE GRASHOF NUMBER

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