Flow Solutions
Energy-Efficient Flow
Solutions By Design
Positive Displacement Sliding Vane
Pump Technology Delivers Superior
Energy-Saving Advantages in
Process Applications
Process
|
Energy
|
Military & Marine
When Efficiency is Measured in Kilowatts . . . It’s Time to Put Some
Energy Into Learning About Positive Displacement Sliding Vane Pumps
Introduction
n Increase operational reliability and process
integrity by emphasizing the use of energy-efficient
technologies that support enhanced mechanical
efficiency
Today, high energy prices impose an unprecedented
profit-robbing threat to every manufacturing operation,
large or small, worldwide. Left unmanaged, energy
expenditures can quietly, and quickly, erode a company’s
financial performance, productivity and ultimately its
competitiveness.
n Reduce vulnerability to energy price volatility
Since pumps account for nearly 27% of total electricity
use in the industrial sector, as manufacturers work
to align their energy-efficiency initiatives with their
business goals, pump system improvements will play an
increasingly important role in this effort. Because there
is no “one-pump-fits-all” solution, particular attention
to proper pump selection will become increasingly
important in the effort to select the right pump not
only to deliver productivity gains, but to also control
energy consumption.
With this threat in mind, manufacturing operations
around the globe are implementing energy management
processes and procedures that seek to:
n Drive productivity improvements that increase
financial performance
n Control energy expenses by reducing power
consumption without compromising output
performance or, preferably, while simultaneously
improving production levels
With this in mind, by virtue of its inherent energy and
mechanically-efficient design, positive displacement
sliding vane pump technology is uniquely suited to offer
manufacturers immediate, high-value advantages and
solutions in fulfilling their energy-saving initiatives.
Table of Contents
Mission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Reduce Energy Costs & Improve System Performance . . 3
Measuring & Managing Energy Consumption . . . . . . . . . . 5
Calculating Potential Energy Savings . . . . . . . . . . . . . . . . . 7
Reducing Energy Waste Through Proper Pump
Selection & Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7
Barriers to Proper Pump Selection & Pump
System Optimization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Using Life Cycle Costs for Proper Pump Selection . . . . . 9
Proper Pump Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Proper Pump Selection for Energy Efficiency . . . . . . . . . . 15
Energy Costs Comparison . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Sliding Vane Pumps vs. Gear Pumps . . . . . . . . . . . . . . . . . . 16
Advanced Sliding Vane Pump Technology
Provides Energy Savings . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Motors & Variable Speed Drives . . . . . . . . . . . . . . . . . . . . . 19
This booklet is part of Blackmer’s Smart Energy
Flow Solutions initiative. It is not intended to be a
comprehensive pump selection guide. The purpose of
this booklet is to educate readers on positive displacement
sliding vane pumps; how they work and why. By virtue
of their design, they offer best-in-class energy-efficiency,
productivity improvement, and total life cycle cost
advantages over other pump technologies. For more
information on Blackmer Smart Energy Flow Solutions,
visit www.BlackmerSmartEnergy.com
NOTE: Much of the following information is presented
in U.S. Standard units of measure, due, primarily, to the
source materials utilized. However, the data is globally
applicable.
2
Blackmer Smart Energy™ Flow Solutions Mission
Enable pump users to a gain a competitive business advantage through the deployment of energy-saving positive
displacement sliding vane pump technology.
Blackmer will accomplish this mission by providing end-users, engineering consultants, OEMs and distributors with
education, tools and knowledge on the energy-saving value and performance-enhancing advantages of positive
displacement sliding vane pumps.
Overview
and overall energy-efficiency are measured and affected
by the pumps and overall system configuration is vital to
developing successful energy-efficient pumping systems.
In addition, knowing the fundamental differences,
advantages and disadvantages between the various pump
technologies, relative to performance and energy-saving
design characteristics, is also necessary in order to select
the pump capable of producing optimum results.
In today’s competitive marketplace, all companies,
regardless of their business, are concerned about the
bottom line. Around the world, energy costs continue to
rise as demand increases for greater profitability through
cost control. In other words, the reduction of energy
consumption is a key component in controlling costs.
Higher energy costs impact the bottom line of every
company, particularly processing operations where,
according to the Hydraulic Institute, pumps represent
27% of the electricity used by industrial systems.
Reduce Energy Costs And Improve System
Performance
Any company that uses industrial pump systems can
realize both energy and non-energy benefits by applying
energy-saving improvements to their operations. Relative
to pumping systems, energy-saving improvement
opportunities fall into two categories: 1) existing
systems (which far exceed new systems), and 2) new
systems. For new systems, begin by selecting the best
pump technology, properly sized for the application.
For retrofit applications, identifying, re-engineering and
correcting improperly sized or poorly designed pumping
systems can result in a company achieving multiple goals
simultaneously:
Pumping systems are a major energy consumer and are
mission critical to every plant’s operation. A wealth of
energy-saving advice is available from a wide variety of
sources, such as the United States Department of Energy’s
Industrial Technologies Program (ITP) and the Hydraulic
Institute’s Pump Systems Matter initiative, among others.
Central to their energy-saving advice is the need for
companies to take a systems approach in order
to significantly improve their energy-efficiency.
This approach will enable operations to improve
reliability, performance and efficiency of their overall
pumping systems, which in turn will result in not only
greater energy savings but also higher productivity,
performance and profitability.
n Reduced energy consumption
n Reduced operations, production and maintenance costs
This means utilizing the best pumping technology
(centrifugal or positive displacement), properly sized
with the appropriate piping design, control valve
configurations and motors to ensure the highest
efficiency for particular applications.
n Improved productivity
n Improved product quality
n Improved capacity utilization
Although the operating principles of positive
displacement and centrifugal pumps differ widely, in
many cases both types can be used to serve the same
applications. In areas where centrifugals cannot be used,
and, more importantly, in the “overlap” applications
where centrifugals and PD pumps may both be used,
positive displacement pumps can likely offer substantial
opportunities to improve processes, uptime,
and energy savings.
n Improved system reliability
n Improved worker safety
Northwest Energy Efficiency Alliance states that: “A dollar
saved on energy, maintenance or production is equivalent
to $17 in sales income (assuming a 6% gross margin).” 1­­­
Energy is the single largest cost of ownership of an
industrial pump system, representing between 50-90%
of total life cycle costs, depending on the technology. There is a specific “best-use” for all pump technologies.
Understanding how pump efficiency, system efficiency
1
SOURCE: Northwest Energy Efficiency Alliance / Industrial Efficiency Alliance – How Continuous Energy Improvements Reduce Costs and Improve System Performance
3
with >10 employees (50,000 plants) have adopted basic
energy management principles.2 According to statistics
published by the Hydraulic Institute, energy-saving pump
system opportunities abound for all pump size ranges.
With so many opportunities for companies to
immediately improve bottom line performance through
energy-efficient pump system improvement, it is easy to
understand why today 25% of the 200,000 U.S. plants
Energy Savings – Efficiency Opportunities by Pump Size
6000
5000
GWhr / Year
4000
3000
2000
1000
0
1-5
HP
6-20
HP
21-50
HP
51-100
HP
101-200
HP
201-500
HP
501-1000
HP
1000+
HP
Source: Pump Systems Matter – U.S. Industrial Motor Systems Market Opportunities Assessment, U.S. Department of Energy
A report published by the U.S. Department of Energy3 revealed energy-saving opportunities by making changes
to pump systems. These suggestions included:
Efficiency Measures
1) Reduce pump speed
2) Match pump size to the load
3) Reduce overall system requirements
2
SOURCE: Pump Systems Matter
3
An Assessment of the U.S. Industrial Motor System 1998
4
Range Of Savings % Of System Energy
1) Reduce Overall System
Requirements
5 – 20%
2) Match Pump Size To Load
10 – 30%
3) Reduce Or Control Pump Speed
5 – 50%
4) Component Purchase
1 – 3%
5) Operations & Maintenance
1 – 5%
Measuring & Managing Energy
Consumption
According to the U.S. Department of Energy, the U.S.
has more than 2.4 million pumps that will consume
142 billion kWh annually in industrial manufacturing
processes. At 5 to 10 cents per kWh, this adds up to
a rather substantial amount of money. It is easy to
understand how improving the energy efficiency of
even one pump could produce substantial financial
savings for any operation. For illustrative purposes,
the table below summarizes the electrical costs of a
continuously operated centrifugal pump driven by
a 100 HP motor. It is easy to see what a 10% reduction
in energy consumption would mean:
The most common unit of measurement on an electric
meter is the kilowatt-hour.
n A kilowatt-hour (kWh) is a unit of energy equivalent
to one kilowatt (1 kW) of power expended for one
hour of time.
Pumping Energy Costs for Pump Driven by 100-HP Motor (assumes 90% motor efficiency)
Operating Time
Energy Costs for Various Electricity Costs
2 cents per kWh
4 cents per kWh
6 cents per kWh
8 cents per kWh
10 cents per kWh
$1.60
$3.30
$4.90
$6.60
$8.20
24 hours
$39
$79
$119
$159
$198
1 month
$1,208
$2,416
$3,625
$4,833
$6,042
$14,500
$29,000
$43,600
$58,000
$72,600
1 hour
1 year
Source: U.S. Department of Energy – Energy Efficiency and Renewable Energy; Pump Systems Matter Energy Tip Bulletin #4
2) Wire-to-Water Efficiency – takes into consideration
the efficiency of the electric motor driver and the
efficiency of the pump. Overall efficiency is a product
of both a pump’s and the power unit’s efficiency. Pumps are wasting energy when they fail to convert the
electric power they consume into the fluid motion that
they were designed to provide.
There are several critical equations with which you will
want to be familiar when considering selection of
a new pump or when analyzing a pump system
for energy-efficiency.
• For electric motors, efficiency ranges are generally
85% to 92%.
• Pumps operating at efficiencies between 60-70%
can be improved.
1) Pump Efficiency – the rate at which a pump imparts
energy (output energy) to the pumpage divided by
the rate at which the pump requires energy (input
energy). The efficiency of a pump is related to its
hydraulic, mechanical and volumetric losses. • Pumps operating at efficiencies less than 50% need
major repairs, system changes or replacement.
3) Specific Energy – the actual power required to pump
a given volume of fluid (kWh/Q)
Efficiency
=
Imparted Energy
Inputted Energy
Specific Energy =
EXAMPLE: If 1.25 HP must be applied to the input
shaft when the pump is doing the work equivalent
to 1 HP, the pump efficiency will be 80% (1 divided
by 1.25)
Energy Used
Pumped Volume
4) Power – a measure of the rate at which work is done or
energy is converted
Power =
5
Energy Converted
Time Taken
The most common prime mover for a pump is a fixed
speed, alternating current (ac) electric motor. Motors
are measured in horsepower delivered. Since pumps
serve such a wide range of needs, pump sizes range from
fractions of a horsepower to several thousand horsepower,
depending on the application. As the horsepower
increases so too does the energy cost to operate the pump.
5) Pump Output (Hydraulic or Water Horsepower ­–
WHP) is the liquid horsepower delivered by the pump.
POSITIVE DISPLACEMENT
Flow Rate (GPM) x
Pressure (PSI)
Hydraulic
Horsepower =
(Water HP)
1714
The combined efficiency of the motor and pump
determines the wire-to-water efficiency of the system. Achieving high wire-to-water efficiency is desired, and
choosing pumps and motors with high wire-to-water
efficiency is needed to ensure long-term efficiency – but
managing energy efficiency of a pumping system is more
complicated than just choosing high efficiency pumps
and motors. There are a variety of sources within a
pumping system that can waste energy including control
valves and throttling, pipe size and configuration and
pump wear, to name a few.
CENTRIFUGAL
Flow Rate (GPM) x
Hydraulic
Head
(FT) x Specific Gravity
Horsepower =
(Water HP)
3960
6) Pump Input (Brake Horsepower – BHP) is the actual
horsepower delivered to the pump shaft.
Flow Rate (GPM) x
Brake
Horsepower = Head (FT) x Specific Gravity
(BHP)
3960 x Pump Efficiency
A pump’s efficiency can degrade as much as 10-25%
before it is replaced.4 Efficiencies of 50-60% or lower
are common. However, because these inefficiencies are
not readily apparent, opportunities for energy savings
by repair or replacement of components are often
overlooked.
NOTE:The constant 3960 is obtained by dividing the
number of foot-pounds for one horsepower (33,000) by the
weight of one gallon of water (8.33 pounds).
When pumps are improperly sized (over or under sized),
when long-term operating costs are not considered, or
when a lack of expertise results in the use of pumps being
improperly matched to applications, energy is wasted.
And, as a result, for every kilowatt of power “input” to
the pump, less is being transferred to the fluid.
OR
Water HP (WHP)
Brake Horsepower =
(BHP)
Not only is the company paying more for additional
energy input, but wear on the pump is also accelerated
reducing component life. Maintenance costs are increased
as are unexpected and premature failures, resulting in
additional productivity losses.
Pump Efficiency
7) Fluid Energy = Fluid Power x Operating Time
8) Horsepower – is defined as the power required to
raise a weight of 33,000 lbs. a vertical distance of 1
foot in 1 minute. The rate of work performed by a
pump (in horsepower) is proportional to the weight
of the liquid it delivers per minute, multiplied by
the total equivalent vertical distance in feet through
which is moved.
Horsepower
(alternating current)
4
=
Pumps are selected based on the maximum demand
of the system. However, the maximum demand may
only actually be required a small percentage of the total
run time. Therefore, the greater the separation between
pump capacity and real-time demand, the greater the
inefficiency and energy waste of the system.
kW x Efficiency
746
U.S. Department of Energy Pump Systems Matter Tip Sheet #4
6
Calculating Potential Energy Savings
n A power reduction of 135 horsepower (100 kW)
in a process running 24/7 reduces energy cost
$40,000 per year (based on an energy price of
$0.05/kWh).
When pumps operate at optimum levels they use less
energy and increase reliability, saving both energy and
maintenance costs. n The maintenance and productivity benefits of
improving a pump system’s performance are
generally one to two times the value of the
energy savings.
Calculating Potential Energy Savings
Savings = kW (in input electric energy) x Annual Operating Hours x
(1 – Actual System Efficiency)
Optimal System Efficiency
EXAMPLE:
1) Operating Efficiency (300 HP pump = 55% Efficiency)
2) Optimal Operating Efficiency (300 HP = 78% Efficiency)
3) Pump draws 235 kW x 6,000 hours of service per year
Savings = 235 kW x 6,000 Hrs/Yr x
(1 – 0.55)
0.78
= 415,769 kWh per year @ 0.05 per kWh = $20,788 Savings
Reducing Energy Waste Through Proper
Pump Selection & Application
n Ensure proper motor alignment (poor alignment of
motor and load increases motor power consumption)
n­­ Reducing pumping system flow rates (lower flow
equates to lower energy losses)
The best way to deal with poorly performing pumping
systems is to specify them correctly in the first place. The best systems meet the real-time requirements of the
process while using the least amount of energy. Industrial
facilities can reduce energy consumption, increase the life
of components and reduce maintenance budgets by:
n Lowering operating pressures
n Operating the system for a shorter period of time
during each day
n Selecting the pump technology best suited for the
application
n Maintaining pumps and all system components
in virtually new condition to avoid efficiency loss
(wear is a significant cause of decreased pump efficiency;
corrosion in pipes increases friction)
n Properly sizing pumps, control valves and piping
systems to real-time requirements (avoid excessive
margin of error capacity and/or total pressure or head)
n Improve inlet/outlet conditions to reduce restrictions,
turbulence and frictional losses
7
Barriers To Proper Pump Selection & Pump
System Optimization
Planning for a satisfactory, economical and energy-saving
pump installation involves two basic items:
1) Selecting the proper type, size and speed of pumping
equipment
Many pumps users do not know how to properly select
and apply pumps to a system, so pump system operating
costs are inadvertently increased as a result. Using pump
selection software programs can help to optimize pump selection.
2) Making a careful study of the suction and discharge
conditions, including details of the piping layout
The proper selection of the pumping equipment must
also consider all of the application conditions:
While manufacturers, such as Blackmer, can help
influence pump specification and proper selection for a
particular application, they are generally not involved
in the engineering of the overall system. In an effort to
reduce costs, end-users have trimmed engineering staffs,
slowly losing their in-house pump expertise. Greater
responsibility is being placed on manufacturers to assist
with the efforts to increase equipment reliability and
operational efficiencies. Industry leading manufacturers,
such as Blackmer, are providing applications and
engineering expertise, pre- and post-sales support, such
as pump specification and selection programs, technical
training and counseling, start-up assistance, maintenance
and troubleshooting advice and technological
innovations for the purpose of helping end-users to
optimize their pumping systems.
1) HOW MUCH FLOW?
Approximate DELIVERY required in
gallons per minute
2) HOW MUCH PUSH?
Differential PRESSURE required in
pounds per square inch (PSI)
3) WHAT LIQUID?
Type of LIQUID to be handled
4) HOW HEAVY?
Specific GRAVITY of the liquid
5) HOW THICK?
Maximum VISCOSITY of the liquid in
Seconds Saybolt Universal (SSU)
6) HOW HOT?
blackOPS® – Blackmer Optimum Pump Solutions
Pumping TEMPERATURE of the liquid in
degrees of Fahrenheit
allows users to select pump data and pump curves so
they can select the proper positive displacement or
centrifugal pumps for their application.
7) HOW MUCH PULL?
SUCTION conditions when pumping in
inches of mercury for vacuum, or psi for
pressure
End-users are beginning to rely more heavily on outside
contractors to provide engineering, procurement and
construction (EPC) for projects. This practice removes the
pump user from the decision-making process beyond the
basic requirements developed by the pump user.
8) HOW LONG?
Type of SERVICE, i.e. intermittent duty,
semi-continuous duty, or continuous
duty
EPCs are typically first-cost driven and have little or no
incentive to optimize a pump system for reduced life
cycle costs (LCC). In fact, since the primary motivation is
to first reduce costs, risks and time to project completion,
energy-efficiency is often not a consideration, which
ultimately has a negative impact on long-term operating
performance and profitability.
Reducing first costs – improves EPC competitive
positions but frequently results in pump systems which
are not energy efficient.
8
Minimizing time to project completion – eliminate the
time necessary to analyze alternative equipment options.
The trade-off is first-cost vs. LCC.
operate with increased maintenance and energy
consumption. Excessive safety factors also reduce system
reliability. Industry sources claim that a 10-15% safety
margin is routinely applied to pumps and motors to
accommodate anticipated capacity increases, and that
overall 70% of pumps are not properly sized resulting
in wasted energy, reduced reliability and higher than
necessary maintenance costs.
Reducing risks – is generally accomplished by adding
safety margins to each step of the design/construction
process. This results in oversized equipment, contributing
to mismatched pumps and system components that
Oversized Pumps
Undersized Pumps
Often paired with oversized control valves and piping. Oversized
control valves consume wasted energy with excessive pressure
drops which shortens valve life
Create cavitation which causes vibration, premature wear that
leads to energy-wasting slip, seal problems and possibly loose bolts,
misalignment and pipe leakage
Want to deliver a higher GPM than the system requires in centrifugal
systems, the head is raised to unneeded pressures:
EXCESS HEAD x FLOW = ENERGY WASTE
Cause motor over-amps resulting in increased electric consumption
Create excessive pressure, velocity, noise, vibration, heat and energy
waste
Cause re-circulation in centrifugal pumps
Create unstable hydraulics that cause excessive pump vibration, wear
and failure
Rarely a problem in PD pumps because the slower the pump runs the
better
Undersized Piping Leads to:
Restricted flow
Requires larger pumps that waste energy
Large pressure losses
Big pipes cost more than smaller diameter pipes
Contractors can save initial costs by bidding smaller pipes that
consume more energy
Bad suction at inlet
Potential pump repairs, downtime and lost production
Too small on discharge side
PD pump will push the fluid though but at higher pressures and energy
costs
Using LCC (Life Cycle Costs) for Proper
Pump Selection
LCC - Relative Comparison
Centrifugal vs. Positive Displacements (PD) Pumps
1.0
Improper pump selection can cost money in
downtime, lost production, maintenance costs and
energy consumption. When purchasing pumps, it is
recommended that pump users pay close attention to
total cost of ownership or life cycle costs (LCC) analysis
to compare operations, maintenance and energy
consumption costs between pump technologies that could
be used for the same application. An analysis of LCC, as
a management tool, can dramatically reduce waste and
maximize efficiency. The NET cost savings based on LCC
will often justify a higher initial price for a more energyefficient pump. Life-cycle costing helps identify the lowest
total cost of ownership:
Total Life Cycle Cost (LCC)
0.8
0.6
0.4
0.2
n Initial equipment cost
n Installation & Commissions
n Energy costs
0.0
n Maintenance & Repairs
n Downtime costs
Centrifugals
n Initial Pump Cost
n Energy Cost
n Decommissioning costs
9
PD Pumps
n Installation, maintenance, operating, environmental & downtime costs
Pump Technology Matrix
SELF-PRIMING
Volute
Radial
Flow
Centrifugal
Kinetic
(Dynamic)
NON-SELF-PRIMING
Single
Suction
DIFFUSER
REGENERATIVE TURBINE
VERTICAL TURBINE
Single
Stage
DOUBLE SUCTION
MIXED FLOW
SEMI-OPEN IMPELLER
CLOSED IMPELLER
MULTI-STAGE
SINGLE-STAGE
AXIAL FLOW
OTHER
Open
Impeller
MULTI-STAGE
JET (EDUCTOR/EJECTOR
OPEN IMPELLER
SEMI-OPEN IMPELLER
SPECIAL ACTION
Pumps
RECIPROCATING
Positive
Displacement
PISTON
SINGLE-ACTING
PLUNGER
DOUBLE-ACTING
SIMPLEX
DUPLEX
TRIPLEX
MULTIPLEX
DIAPHRAGM
BELLOWS
FLUID OPERATED (Air/Hydraulic)
MECHANICALLY OPERATED
Blade
Vane
Single Rotor
Rotary
MULTIPLE ROTOR
OTHER
PISTON
FLEXIBLE IMPELLER
PERISTALTIC
SINGLE SCREW
PROGRESSIVE CAVITY
ROLLER
AXIAL
RADIAL
TUBE & ROLLER
LINER
LIQUID RING
EXTERNAL
GEAR
INTERNAL
LOBE
CIRCUMFERENTIAL PISTON
MULTIPLE SCREW
SPECIAL ACTION
SPUR
HELICAL
HERRINGBONE
TIMED
UNTIMED
CRESCENT
NO CRESCENT
SINGLE/MULTIPLE
SINGLE/MULTIPLE
TIMED
SINGLE/MULTIPLE
UNTIMED
Source: Schematic courtesy of Chemical Processing Magazine
Proper Pump Selection
standard centrifugal pump the greater efficiency it has
at its best efficiency point (BEP). Therefore, the potential
efficiency advantage afforded by positive displacement
pumps should be reviewed in high flow applications.
Although the operating principles of positive
displacement and centrifugal pumps differ widely,
both types of pumps can be used to serve many of
the same applications. In these instances, certain
positive displacement pumps may offer substantial
opportunities to improve processes and productivity as
well as maintenance and energy cost savings. Positive
displacement pumps generally require less NPSHA than
centrifugal pumps, and they offer more flexibility relative
to dealing with varying changes in pressure and flow
requirements of continuous-type processes.
However, since centrifugal pumps operate dependent of
the system curve they rarely operate at their BEP, even
if they are sized/selected appropriately. This is due to
the routine practice of building in a safety margin for
anticipated capacity increases. Changes in the system
curve, due to factors such as suction/discharge height
variations, blockage, etc. will also shift the centrifugal
pumps’ operating point. Positive displacement
pumps, specifically sliding vane pumps, do not have
this limitation as their output is, to a large extent,
independent of the system curve. Further, as with positive
displacement gear and lobe pumps, centrifugal pumps’
internal clearances increase over time resulting in a
decrease in efficiency. Positive displacement sliding vane
pumps utilize self-adjusting vanes that eliminate clearance
increase problems to maintain near original hydraulic
efficiency over time. This feature offers substantial energy
savings benefits.
Also, positive displacement pumps maintain higher
efficiencies throughout the viscosity range. Therefore, in
the overlap where both types of pumps can operate, a
positive displacement pump’s high mechanical efficiency
can offer improved energy efficiency.
The delta in wire-to-water efficiencies of positive
displacement pumps as compared to centrifugal pumps
decreases as flow rates increase. That is, the larger the
10
Selecting the proper pump begins by knowing:
Differential pressure is critical to energy-savings and
pump life. Smaller pipe size and large pipe runs may
reduce initial cost, but they can cause higher differential
pressure for pumps. This results in higher energy
consumption and higher operating costs.
1) Total head or pressure against which it must operate
2) Desired flow rate
Once system conditions and liquid properties are known,
the next step is to determine whether a centrifugal of PD
pump is the better choice.
3) Suction lift
4) Fluid characteristics (Temperature, corrosiveness, etc.)
The piping system and pump interact to determine the
operating point of pumps: flow rate and pressure.
Basic Comparison – Centrifugal Pumps Vs. Positive Displacement Pumps
Centrifugal
Positive Displacement
Mechanics
Imparts velocity to the liquid resulting in a pressure at the
outlet (pressure is created and flow results).
Captures confined amounts of liquid and transfers it from
the suction to the discharge port (flow is created and
pressure results).
Performance
Flow varies with changing pressure.
Flow is constant with changing pressure.
Viscosity
Efficiency decreases with increasing viscosity due to
frictional losses inside the pump (typically not used on
viscosities above 850 cSt).
Efficiency increases with increasing viscosity.
Efficiency
Efficiency peaks at best-efficiency-point. At higher or
lower pressures, efficiency decreases.
Efficiency increases with increasing pressure.
Inlet Conditions
Liquid must be in the pump to create a pressure
differential. A dry pump will not prime on its own.
Negative pressure is created at the inlet port. A dry pump will
prime on its own.
Source: Chemical Engineering – Facts At Your Fingertips; Department Editor: Kate Torzewski
Flow versus Pressure
Efficiency versus Viscosity
250
100
80
EFFICIENCY %
HEAD FEET
200
Positive
150
100
Centrifugal
50
0
Positive
60
40
Centrifugal
20
0
50
100
0
150
0
250
CAPACITY (gal/min)
Efficiency versus Pressure
750
1000
Flow versus Viscosity
110
80
Positive
100
Positive
70
FLOWRATE %
EFFICIENCY %
500
VISCOSITY (cSt)
60
Centrifugal
50
90
80
70
Centrifugal
60
50
40
55
80
40
105
FEET OF HEAD
0
100
200
300
VISCOSITY (cSt)
11
400
500
Comparing Centrifugal Pumps To Positive Displacement Pumps
If The System Calls For:
The Best Pump To Use Is:
Pressurized network of piping with a constant pressure requiring constant flow rate
Centrifugal
Constant flow at various pressures
Positive Displacement
Constant flow at various viscosities
Positive Displacement
Constant flow at high viscosities (particularly above 850 cSt)
Positive Displacement
Line stripping
Positive Displacement
Dry running – short duration
Positive Displacement
Priming
Positive Displacement
Shear sensitive
Positive Displacement
Entrained gases
Positive Displacement
High flow / low head
Centrifugal
Low flow / high head
Positive Displacement
Summary
Consider Positive Displacement Pumps over
4) System requires high-pressure, low-flow
Centrifugals when:
5) Line stripping is required (some PD technologies)
1) Working fluid is highly viscous (over 850 cSt)
6) Suction lift or self-priming is required
2) Flow rate must be predictable over a wide
7) Working fluid is shear-sensitive
flow range (flow must be metered or
8) Energy-savings/efficiency is a primary concern
precisely controlled)
3) Flow rate must remain constant under varying
system pressures
“Though engineers may be first inclined to install centrifugal pumps, many applications dictate the need for PD pumps.
Because of their mechanical design and ability to create flow from pressure input, PD pumps provide a high efficiency under
most conditions, thus reducing energy use and operation costs.”
Chemical Engineering – Facts at Your Fingertips (Department Editor: Kate Torzewski)
12
Centrifugal Pump Highlights
n Good for applications requiring high flow/low
head in which viscosity is not prohibitively high
n Roto-dynamic principle: accelerates fluid and
converts this kinetic energy into pressure
n If part of a process changes often or
continuously, some method of altering the
pump characteristics is necessary. Common
practices include:
• Centrifugal pumps are subject to the Affinity Laws:
- Flow is directly proportional to changes in
speed
- Pressure increases by the square of changes
in speed
• Throttling valves
- Obstruct flow – increase head pressure
(increases energy consumption)
- Horsepower increases by the cube of changes
in speed
- Producing 70% flow requires up to 90% of the
energy used at full speed
• Higher flow rates create higher flow velocities
which leads to friction loss and higher energy
consumption
• On/Off Control
- Used in cases where step-less control is not
necessary (keeping pressure in the tank
between preset limits)
• Pressure is expensive. Pressure through a pipe is
proportional to the square of the fluid velocity;
given the same size pipe, a flow rate that is
2x higher endures 4x more friction loss. This
means that it costs more to pump a higher than
necessary flow rate.
- Pump is either running or stopped
- Average energy consumption is the same as
average run time (70% energy consumption
for 70% average flow)
• Horsepower is expensive – BHP increases greatly
as speed increases
• Variable speed drives (VSD)
n Make up 75% of the industrial process
pump industry
- Changes pump speed and flow generated
(consumes less energy than throttling)
n Complex to select the right pump resulting in
the tendency to over-size the pump
- The greater the static head, the lower the
possible energy savings between a VSD
and Throttling
• Increases the cost of operating and maintaining
• Creates operating problems such as excessive flow
noise, inefficient operation and pipe vibration
n The larger the centrifugal pump, generally,
the greater its efficiency at its BEP
• Creates performance degrading and pump
damaging cavitation and recirculation
• Consumes more energy than necessary for the duty
n Variable flow/pressure relationship
• The amount of fluid a centrifugal pump moves
depends on the differential pressure
• As pump differential pressure increases the flow
rate decreases
• Low flow in centrifugal pumps consume
more energy
• Excess pressure is expensive
13
Positive Displacement Pumps Highlights
■ Positive displacement pumps pressurize fluid
■ Lower overall cost of ownership than centrifugal
utilizing a collapsing volume action
pumps (based on LCC)
• Have a fixed displacement volume
• Possibly higher initial (purchase) cost
• Flow rates are directly proportional to their speed
• Typically lower energy costs – many times
significantly lower
• The pressures they generate are determined by
the system’s resistance to flow
■ Rotary PD designs minimize pulsation as
compared to reciprocating technologies
■ Make up approximately 15% of industrial
process pump industry
• Sliding vane and gear technologies exhibit little
to no pulsation
■ Effective at generating high pressure in
low-flow applications
■ Dry Run, self-priming and superior suction
lift capabilities
■ Simple to operate and maintain
• Can operate with entrained gases in the pumpage
■ Handle a wide viscosity range (Low and High
• Pumps or suction piping can be placed above the
viscosity fluids)
fluid level to simplify layout
• Advantage over centrifugal pump when pumpage
■ Well suited for metered-flow applications
is highly viscous (by directly pressurizing fluids,
■ Sealless options available – (eliminate leaks
PD pumps use less energy)
when handling high-value chemicals, hazardous
• Sliding vane technology is exceptional on thin
or corrosive liquids to yield substantial cost
and low-lubricity fluids (LPG, Refrigerants,
savings and safety)
Solvents, Fuel Oils, Gasoline, Liquid Carbon Dioxide)
• Magnetically coupled/drive pumps
• Sliding vane technology is exceptional on
• Eccentric disc pumps
non-lubricating liquids (thick and thin)
• Peristaltic hose pumps
• Sliding vane technology is better in shear-
• Air diaphragm pumps
sensitive applications than many other PD
designs and centrifugal pump technologies
■ Designed for high efficiency that results in
high reliability and energy savings
■ Typically more efficient than centrifugal
pumps... in some cases significantly
• High volumetric efficiency
more efficient
- Self-adjusting vanes on sliding vane pumps
eliminate the energy-robbing slip caused
by wear; maintain near original efficiency
throughout the pump’s operating life
• High mechanical efficiency
14
Proper Pump Selection For Energy Efficiency:
Positive Displacement Pumps Are Not Created Equal
lost production, maintenance costs and energy consumption.
Following is an overview of several types of leading positive
displacement pumps:
Positive displacement pumps are not created equal.
There are significant differences between PD pump types.
Improper pump selection can cost money in downtime,
PD Pump
Sliding
Vane
Features
Viscosity Range Flow Rates
n Exceptional for thin liquids due to direct contact of vanes to casing and minimal
n
n
n
n
n
n
n
n
n
n
internal clearances
Excellent on thick liquids at slow speeds
Exceptional efficiency at low flow rates
Excellent suction lift and line stripping capabilities
Self-adjusting vanes eliminate energy-robbing slip and capacity loss to provide
substantial energy savings
High mechanical efficiency = energy savings
Differential pressure to 200 psi
Speed to 3,600 RPM
Hydrodynamic journal bearing models significantly reduce friction, excessive heat
build-up and energy loss
Motor speed models are specifically designed for continuous duty operation for low and
medium viscosity applications
Low energy consumption
Very thin (LPG,
1 to > 2,000
Refrigerants,
GPM
Solvents, Fuel
Oils, Gasoline,
Liquid Carbon
Dioxide,
Ammonia, etc.) to
High viscosities
up to 50,000 cSt
n Differential pressure to 200 psi (higher pressures are attainable)
n Speed to 3,600 RPM
n Metal-to-metal gear results in wear and slip, resulting in efficiency degradation and
High viscosities
up to 1,000,000 cSt
0.5 - 1,500
GPM
External
Gear
n
n
n
n
n
n
n
Do not perform well under critical suction conditions, especially with volatile liquids
Good for high pressure applications such as hydraulics
Differential pressure to 3,000 psi +
Speed to 3,600 RPM
Metal-to-metal gear design subject to efficiency degradation
Must be rebuilt or replaced
No clearance adjustments for wear which results in slip, efficiency degradation and
higher energy consumption
High Viscosity up
to 1,000,000 cSt
Drops per
minute to
1,500 GPM
Lobe
n
n
n
n
Used frequently for food-type products due to sanitary nature and ease of cleaning
Vertical drain port reduces efficiency by 15-20%
Sanitary Models: Differential pressure to 200 psi
Non-Sanitary Models: Differential pressure to 400 psi
Low Viscosity
with diminished
performance up
to 1,000,000 cSt
5 - 3,000
GPM
Air
Diaphragm
(AODD)
n No bearings or rotating shaft
n Can handle a wide range of shear-sensitive, abrasive and non-abrasive liquids as well
Internal
Gear
higher energy consumption over time
as solids
n High pressure operation can cause excessive wear around valve seats as the check
valve closes
n Variable speed flow operation
n Requires air compression system. Electricity is used to run compressors.
n Energy accounts for 70% of compressed air life cycle cost – air is not free.
High energy costs.
15
Medium viscosity 1 - 500
to 26,000 cSt
GPM
Energy Costs Comparison – Vane/Lobe/Gear
robbing slip and promotes high volumetric efficiency
even after substantial time in service. Both gear and
lobe pumps are subject to wear that increases internal
clearances within the pump housing that result in slip
and efficiency degradation. Following is a Mechanical
Efficiency Comparison between three leading positive
displacement technologies. From the lowest to the highest
viscosity, sliding vane technology provides the highest
level of mechanical efficiency which equates to the lowest
overall energy consumption.
Of the leading positive displacement technologies,
sliding vane pumps are generally the most energy
efficient. Significant design advancements have given
sliding vane technology a decisive advantage over lobe
and gear pumps, specifically with regards to optimized
performance, low-shear capability, lowest life cycle cost
and best energy efficiency. This is due in part to the
self-adjusting vane design-feature that eliminates energy-
Energy Costs – Mechanical Efficiency Comparison, PD Pumps: Vane / Lobe / Gear
50-100 GPM; 50-100 PSI;
4-1,620 cSt viscosity;
same model on all viscosities
Sliding Vane Pumps Vs. Gear Pumps
Comparison of Sliding Vane Pumps Vs. Internal Gear Pumps
Sliding Vane Pumps
Internal Gear Pumps
n Superior mechanical performance
n Provides greater energy savings
n 24% More efficient than gear pumps
n Less mechanically efficient
n Consume more energy than vane pumps
n Sliding vane pumps have a number of non-metallic vanes that
n Internal gear pumps utilize an outer gear called a rotor that is
n
n The gears create a void as they come out of mesh - the volumes
n
n
n
n
n
slide into and out of slots in the pump rotor.
When the pump driver turns the rotor, centrifugal force, rods and/
or pressurized fluid causes the vanes to move outward in their
slots and bear against the inner bore of the pump casing, forming
pumping chambers
This fluid is passed around the pump casing to the discharge port
Each revolution displaces a constant volume of fluid
Variances in pressure have minimal effect
The sliding vanes automatically adjust to maintain near perfect
clearances throughout operating life
Energy-wasting turbulence and slippage are minimized and high
volumetric efficiency and low energy consumption are maintained
used to drive an inner gear called the idler
are reduced and liquid is forced out the discharge port
n Each revolution displaces a constant volume of fluid
n Variances in pressure has minimal effect
n The metallic gears wear over time resulting in wider clearances;
this increases energy-robbing slippage and significantly
decreases volumetric efficiency
n In order to compensate for performance degradation, pump speed
is increased which requires greater energy consumption
16
By eliminating the need to increase the pump speed
over time, sliding vane pumps save additional energy
when compared to gear pumps. Sliding vane pumps are
inherent energy savers by virtue of their design. This
technology not only reduces energy costs but helps
to create an overall more efficient pumping system,
providing solutions for seals, suction, product shear, and
volumetric efficiency problems to offering unique benefits
such as leak-free assurance, line stripping, metering, and
non-pulsating flow – all while saving energy.
Sliding Vane Pump vs. Internal Gear Pump
ME
Mechanical Efficiency Comparison at 160 cSt and 100 PSI
Sliding Vane Pump vs. Internal Gear Pump
Sliding Vane Pump vs. Internal Gear Pump
Mechanical Efficiency Comparison at 5,250 cSt and 100 PSI
ME
ME
Mechanical Efficiency Comparison at 1 cSt and 75 PSI
Annual Energy Cost Savings: Sliding Vane vs. Internal Gear Pumps
Liquid
Viscosity
Pump
GPM
PSI
310
75
180
75
BHP
WHP
(Water)
Efficiency
Pump
Motor (1)
KW
Input
Annual Power
Cost (2)
68%
88%
17.0
$3,828
59%
88%
19.5
$4,380
65%
88%
10.3
$2,323
39%
88%
17.0
$3,809
68%
88%
17.0
$3,828
50%
88%
23.0
$5,161
65%
88%
10.3
$2,323
37%
88%
18.2
$4,094
Annual Savings with
Sliding Vane Pumps
Pump Sized for Stated Flow
Thin
1 cSt
Viscous
5,250 cSt
Sliding Vane
Internal Gear
Sliding Vane
Internal Gear
20.1
23.0
12.2
20.0
13.6
7.9
$552
$1,485
Pump Sized for Wear Factor Allowance
Thin
1 cSt
Viscous
5,250 cSt
Sliding Vane
Internal Gear
Sliding Vane
Internal Gear
310
75
180
75
20.1
27.1
12.2
21.5
13.6
7.9
$1,333
$1,771
1) Typical
2) Assumes 8 hours/day, 6 days/week, 52 weeks/year Duty Cycle and $0.09 KWh. Power Cost may be directly ratioed for other electric rates or duty cycles
17
Advanced Sliding Vane Pump Technology
Provides Energy Savings
125 psi
Minimum Film Thicknes Ratio
Non-Hydrodynamic
For even greater flexibility, efficiency and productivity,
advanced vane pump designs include motor speed
technology, unique “designed-in” features such as a
hydrodynamic journal bearing and one mechanical seal.
These innovative features serve to further improve the
fundamental pumping process and improve energy
efficiency. Additionally, motor speed vane pumps do not
require a gear reducer, so they offer upfront equipment,
installation and energy cost savings.
Hydrodynamic
1
Internal
Gear Pump
0.9
0.8
L/D = 1.5
L/D =
1
560 ssu
0.7
0.6
0.5
0.4
40 ssu
0.3
PV30
0.2
0.1
0
0.000
0.001
0.010
0.100
1.000
10.000
Bearing Characteristic Number (S)
1 cSt @ 125 psi
Minimum Film Thicknes Ratio
Non-Hydrodynamic
Hydrodynamic Journal Bearing
The Hydrodynamic Journal Bearing is a performanceenhancing design feature that significantly improves
overall pump efficiency, reliability and extends bearing
life. With this design, the pump shaft rides on a fluid
boundary during load conditions to eliminate shaft-tobearing contact, friction and wear.
Hydrodynamic
1
0.9
L/D = 1.5
0.8
L/D =
1
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0.000
PV30
Internal
Gear Pump
0.001
0.010
0.100
1.000
10.000
Bearing Characteristic Number (S)
1 cSt @ 60 psi
Non-Hydrodynamic
Minimum Film Thicknes Ratio
Since there is no metal-to-metal contact or wear in this
hydrodynamic condition, bearing life can be indefinite.
Motor speed vane pumps are engineered to achieve
hydrodynamic mode (full film operation – the point
offering the lowest bearing friction and the least wear)
faster than any other pump in its class to preserve
bearing life. These pumps also maintain optimum
bearing characteristics even under a wide range of
operating conditions.
Hydrodynamic
1
0.9
L/D = 1.5
0.8
L/D =
1
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0.000
PV30
Internal
Gear Pump
0.001
0.010
0.100
1.000
10.000
Bearing Characteristic Number (S)
Cavitation Suppression Liner
Reduced shaft-to-bearing contact minimizes friction,
lowers power loss, and improves reliability and bearing
life, resulting in higher mechanical efficiency and smart
energy cost savings.
Cavitation is a physical barrier to efficiency that can severely
impact a pump’s performance as the liquid changes to a
vapor inside the pump chamber. This effect decreases flow
through the pump and can cause substantial damage to the
pump as the vapor bubbles collapse back to the liquid state.
Cracking and popping noises indicate cavitation, which can
lead to expensive repairs if left uncorrected.
ProVane® Motor Speed Sliding Vane Pump
With Hydrodynamic Journal Bearing Advantage
According to the Department of
Energy Industrial Technologies
Program’s Sourcebook for Industry,
the effects of cavitation include
increased maintenance costs,
slip, capacity loss as well as poor
system performance. Centrifugal
pumps are susceptible to these factors as well as “internal
recirculation,” a performance-degrading-effect that occurs at
low flow rates, which can damage the impeller and rotor.
Unique to vane technology, a Cavitation Suppression Liner
minimizes the pump’s wear effects associated with cavitation.
This patented solution helps to reduce the potential for slip
and capacity loss, ensuring the highest level of efficiency and
energy savings.
18
Relief Valve
High Efficiency Motors
Blackmer® relief valves are designed to protect your pump
in a high pressure build-up situation. Ideal for variable
flow and pressure conditions, the relief valve offers:
The efficiency of a motor is the ratio of mechanical power
output to electrical power input.
Output Power
Efficiency =
n Superior ability over other PD pumps to hold pressure
under variable flow/pressure conditions
Input Power
=
Input Power - Losses
n Maintains motor horsepower requirement to help
control energy consumption
Input Power
n Highly engineered to
provide better control
over set points and
operating conditions
x 100%
x 100%
High efficiency motors can help to minimize losses within a motor. Operations where the motor is running at less than 60% of its rated load should be reviewed and replaced.
n Lowers heat generation
In general, correctly sizing the motor to the load offers
the greatest improvement opportunity. A high-efficiency
motor (partly loaded) may use more energy than a
smaller, less efficient motor in the same application.
Gear Pump
Vane Pump
Typical Motor Efficiency at
60
Typical Motor Efficiency
at Different Loads
different loads
50
100
Flow
40
30
0.75kW
Efficiency %
70
10
20
7.5kW
80
20
0
75kW
90
40
60
80
100
120
140
160
Differential Pressure
60
50
40
30
20
10
Motors & Variable Speed Drives
0
0
25
50
75
100
125
150
175
% Rated Load
Most pumps are driven by electric motors. According to
the Hydraulics Institute, up to 90% of prime movers in
process applications are driven by motors. Fixed speed
alternating current (AC) motors are the most common
type of motors. Variable frequency controls for AC
motors allow for speed ranges between 25% and 110%
of synchronous speed.
Variable Speed Drives
VSDs regulate the speed of the motor, reducing fluid flow.
However, energy can be wasted when using VSDs. It is
best to avoid:
High efficiency motors may not be required for sliding
vane pumps – and can actually decrease productivity and
cost more if misapplied. In high-run-time applications,
improved motor efficiencies can reduce operating costs.
However, it is often more effective to take a systems
approach that uses proper pumps, measurements and
sizing, coupled with effective maintenance practices to
avoid unnecessary energy consumption.
1. Creation of excess pressure
2. More flow through system than is necessary
3. High frictional losses created from high average flows
4. Multiple pipes or ducts carrying fluid that is not being used
19
Every Blackmer Product Comes With A Value-Added Extra:
Applications Engineering/Technical Support/Customer Care
When it comes to flow solutions, uptime, output, reliability and profitability are critical to every operation’s mission. To this
end, Blackmer knows that reliable, proven flow technologies are critically important, but we also know that this represents
only one part of the overall equation. The other, equally important part involves having trained, knowledgeable and
customer-focused staff, which is why we make substantial investments in our people. It is through their collaborative effort
with customers that the greatest achievements are realized.
n Applications Engineers – experts in peace-of-mind assurance,
making sure your equipment is always right for the job
n Market & Product Specialists – unparalleled technical knowledge,
on-site product training, troubleshooting, installation and
product-selection consultation, and total life cycle attention
n Regional Sales Management – proven technicians with an
“above and beyond” commitment to every customer’s mission
n Customer Care Specialists – action-oriented specialists
committed to making sure every order receives immediate attention, is accurately processed and followed up, and to helping keep your process flowing smoothly
When you put it all together, for mission critical flow solutions,
it’s easy to see why leading companies around the world have
one common demand … Better Get Blackmer.
Total Life Cycle Support
From the moment of initial contact and equipment selection through
every point of the product and application life cycle, Blackmer
specializes in helping customers get the maximum value from their
flow technology assets by providing total life cycle support.
Customer Care
Regional Sales
Manager
Market & Product
Specialist
Manufacturing
Application
Engineer
Design
Engineering
www.blackmer.com
Brochure ATK-0200-003 03/10
Copyright © 2010, Blackmer
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|
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|
Military & Marine
World Headquarters
1809 Century Avenue SW, Grand Rapids, MI 49503-1530 USA
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SLIDING VANE PUMPS
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