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PUMPS

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Fans, Pumps, Motors, and Lighting Workshop. Todd Sears. Pumps are the second most ... wear with fewer replacement parts. Centrifugal pump concerns. Viscosity ... – PowerPoint PPT presentation

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Title: PUMPS


1
Muscatine Power WaterFans, Pumps, Motors, and
Lighting Workshop
  • PUMPS
  • Energy efficiency and
  • improving pumping system performance

Todd Sears
Power Process Equipment Inc.
2
  • Pumps are the second most
  • common machine in use today,
  • they are exceeded in numbers only by electric
    motors
  • Pump represent 27 of the electricity consumed in
    the manufacturing sector

3
Pumping system components
  • Typical pumping systems contain five basic
    components
  • Pump
  • Prime mover
  • Piping
  • Valves
  • End-user equipment
  • (e.g. heat exchangers, tanks, other equipment)

4
WHAT IS THE PURPOSE OF A PUMP?
  • Pumps are designed to move fluid
  • Pumps transfer fluid for processing
  • In most plants pumps are a critical part of daily
    operation

5
Pump terms
-Flow Measured in gallons per
minute -Pressure Measured in PSIG -Head Measu
red in feet -Pump curve Displays flow, head
Eff. -Best efficiency point Relates to energy
consumption -Cavitation Upset condition inside
a pump -Deadhead No discharge flow from a
pump -Suction, Discharge Fluid
connections -Base Foundation for pump and
driver -Alignment lining up pump shaft with
driver
6
Pump types
  • Positive displacement
  • Fixed displacement, fluid is captured in
    cavities within the pump and mechanical energy
    moves it from the inlet to discharge
  • Centrifugal
  • Velocity is added to fluid by a spinning
    impeller and converted to pressure energy inside
    the pump. Pressure differential moves the fluid
    through the pump

7
Positive displacement pumps strengths
  • Low flow
  • High pressure
  • High viscosity
  • Self priming
  • Metering
  • High energy efficiency

8
Positive displacement pump concerns
  • Not for water thin fluids
  • Relief valves required
  • Solids can be a problem
  • Flow limited by size and speed
  • Pulsating flow
  • More complicated machine
  • May require speed reducers
  • Higher initial cost
  • Higher repair costs

9
Positive displacement pumps
10
Centrifugal pump strengths
  • High flow capability
  • Variable flow rates
    even at constant speed
  • Wide range of operation
  • Solids handling
  • Lower initial cost
  • Lower repair costs
  • Simple and safe to operate
  • Less wear with fewer replacement parts

11
Centrifugal pump concerns
  • Viscosity limitations
  • High pressure may require multiple impellers
  • Self priming issues
  • Lower energy efficiency
  • Piping system back pressure controls flow

12
Centrifugal pump operation
13
Centrifugal pumps
14
Energy efficiency comparison Positive
displacement vs. Centrifugal pumps
  • Conditions of service
  • 105 GPM
  • 48Cps
  • 80 PSIG discharge pressure

PD pump -1750 RPM -9.2 HP -15 HP motor
  • Centrifugal pump
  • -3600 RPM
  • 13.2 HP
  • 20 HP motor

30 Horsepower difference Potential of over
1300/yr. savings
15
(No Transcript)
16
Common pump sizing issues
  • The importance of pumps to the daily operation of
    many facilities promotes the practice of
    conservatively sizing pumps to ensure that the
    needs of the system will be met under all
    conditions
  • In addition to inefficient operation, oversized
    pumps typically require more frequent maintenance
    than properly sized pumps

17
Oversized pumps
  • Oversizing pumps adds to system operating costs
    both in terms of energy and maintenance
    requirements
  • -These costs are often overlooked during the
    system specification process
  • Since many of these operating and maintenance
    costs are avoidable, correcting an oversized pump
    can be a cost-effective system improvement

18
Indications of an oversized centrifugal pump
  • High flow noise
  • Highly throttled flow control valves
  • Heavy use of bypass lines
  • Frequent bearing and seal replacement
  • Intermittent pump operation

19
High flow noise
  • Oversized pumps tend to create high noise levels
  • The cumulative damage that results from
    flow-induced pipe vibrations can significantly
    accelerate system wear
  • Pump is running at high flow conditions and using
    extra energy

20
Throttled flow control valves
  • Throttle valves provide flow control in two ways
    by increasing upstream backpressure, which
    reduces pump flow, and by directly dissipating
    fluid energy.
  • This dissipating of energy is an inefficiency
    that can be addressed

21
Bypass lines
  • Bypass lines prevent the buildup of damaging
    pressure differentials
  • The energy used to push fluid through bypass
    lines is wasted
  • A system that normally operates with a large
    number of open bypass valves indicates that the
    system is performing inefficiently due to
    improper balancing, oversized pumps, or both

22
Frequent bearing and seal
replacement
  • Excess system flow can extend beyond high energy
    costs
  • Oversized pumps often operate far from their Best
    efficiency point (BEP)
  • They tend to experience greater bearing and seal
    wear

23
Moving towards Shut-Off
BEP
Pump Operating Point
/- 15
Extreme Runout
24
Hydraulic loads on the impeller
BEP
Impeller Radial Force
High load
Low load
Capacity
25
Simultaneous loads on pump shaft
Impeller Radial Thrust
Impeller Axial Thrust
Hydraulic Induced Forces due to Recirculation
Cavitation
Seal or Packing
Impeller Axial Thrust
Radial Thrust due to Hydraulic Imbalance
Hydraulic Imbalance
26
Head flow impact on pump reliability
Head
150
BEP
125
100
Impeller Damage
Low Flow Cavitation
75
Suction Recirculation
High Temperature Rise
Bearing Seal Life Reduced
Discharge Recirculation
50
High Flow Cavitation
25
0
0
20
40
60
80
100
120
140
160
Capacity
Presented by S. Gopalakrishnan 5th International
Pump Symposium Houston, TX
27
Intermittent Pump Operation
  • Pumps are often used to maintain fluid levels in
    tanks, either by filling or draining
  • Systems with level controls activate the pumps
    automatically
  • The cumulative effect of energizing and
    de-energizing a pump shortens the lives of the
    motor controller and the pump assembly

28
Ways to control flow of centrifugal pumps
  • Discharge throttle valves
  • Bypass valves
  • Impeller trimming
  • Speed control
  • Multiple pump arrangements

The most appropriate flow control method depends
on system size and layout, fluid properties, and
system sensitivity to flow rate changes
29
Discharge throttle valves
  • Throttle valve chokes fluid flow such that less
    fluid can move through the valve, creating a
    pressure drop across it.
  • Throttle valves are more efficient than bypass
    valves. As the flow is limited the power required
    by the pump is reduced

30
Bypass valves
  • Bypass lines allow fluid to flow around a system
    component
  • Bypass lines increase system flow and require
    more power
  • The power used to pump the bypassed fluid is
    wasted

31
Impeller trimming
  • Impeller trimming refers to the process of
    machining the diameter of an impeller to reduce
    the energy added to the system fluid.
  • Impeller trimming offers a useful correction to
    pumps that are oversized for their application.
  • A 2 percent reduction in impeller diameter
    creates about a 2 percent reduction in flow, a 4
    percent reduction in head, and an 8 percent
    reduction in power

32
When to consider impeller trimming
  • High noise or vibration levels exist indicating
    excessive flow.
  • Highly throttled discharge flow control valves.
  • Systems bypass valves are open, indicating excess
    flow available.

Note Impeller trim should be limited to 70 of
full diameter
33
Variable speed control
  • Pump speed adjustments provide an efficient
    means of controlling pump flow.
  • By reducing pump speed, less energy is imparted
    to the fluid and less energy needs to be
    throttled or bypassed.

34
Multiple pump arrangements
  • Multiple pump arrangements are flexible,
    redundant, and have the ability to efficiently
    meet changing flow needs in systems with high
    static head components
  • Multiple pumps are usually parallel combinations
    of the same pump model to provide balanced load
    sharing during periods when all the pumps are
    operating

35
Systems approach to energy savings
  • The systems approach seeks to increase the
    efficiency of electric motor systems by shifting
    the focus from individual components and
    functions to total system performance.
  • In addition to energy savings, these improvements
    will yield a number of other economic benefits,
    including increased control over manufacturing
    processes, reduced maintenance, and higher levels
    of quality control.

36
Efficient pumping system considerations
  • Piping system layout that minimizes pressure
    drops
  • Larger pipes create less friction loss
  • Minimize unnecessary pressure drops by avoiding
    sharp bends, expansions, contractions, and where
    possible keep piping as straight as possible.
  • Use of low-loss components. valves, long sweep
    elbows, and components.

37
Pump system Life cycle costs
  • A highly efficient pumping system is not merely a
    system with an energy-efficient motor.
  • Overall system efficiency is the key to maximum
    cost savings. Often users are only concerned with
    initial cost, accepting the lowest bid for a
    component, while ignoring system efficiency.
  • To achieve optimum pumping system economics,
    users should select equipment based on life cycle
    economics and operate and maintain the equipment
    for peak performance.

38
References and sources for more information
  • Improving Pumping System Performance A
    sourcebook for Industry.
  • -Motor Challenge January 1999
  • Cameron Hydraulic Data
  • -Ingersoll Dresser Pumps
  • Pump Principals Manual, Form 07865
  • -A.W. Chesterton Company

39
Thank you
  • Todd Sears
  • Power Process Equipment Inc.
  • Cell 309-738-3481
  • Email todds_at_ppei-mn.com
  • Working with Industry to improve reliability
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