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DESIGN STANDARDS
FOR PUMPING FACILITIES“READING THE TEXT BOOKS”
February 12, 2013
Ernest C Sturtz, P.E., BCEE
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Ernest Sturtz, P.E., BCEEPump Station Design
• More than 35 years hydraulic systems and
pump station design and construction experience
• CDM’s Senior technical leader for pump
station design
• Member of several Hydraulic Institute Standards
Committees Including Intake, Vibration, NPSH/AOR
and Pump Piping. Co-Chair of Pump Application
Guidelines for Water and Wastewater
• Technical oversight for hundreds of pump stations
around the globe during career, many in Texas
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Today’s Topics
The “Textbooks” – “Pumping Station Design” Jones, Sanks, et al
– “Pump Handbook” Karassik, Krutzsch, Fraser & Messina
– Hydraulic Institute Design Standards
• Intake Design Standard ANSI/HI 9.8-2012 – Inlet/Wet Well Configuration Design
• Pump Piping Standard ANSI/HI 9.6.6-2009
• Vibration Standards ANSI/HI 9.6.4-2009 & “Dynamics”
• NPSH/AOR Standards ANSI/HI 9.6.3 & 9.6.1
– Hydraulic Institute “Textbooks”
• “Pump Life Cycle Costs”
• “Variable Speed Pumping”
• “Optimizing Pumping Systems”
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What is the Hydraulic Institute and what is a
“Standards Partner”?
• US organization founded in 1917 to create pump
related standards and solve pump related issues
• Members are Pump Manufacturers
• The Hydraulic Institute prepares design standards for
all aspects of pumping (issued under ANSI)
• Associate Members are manufacturers of related
equipment such as motors, VFDs and controls
• Standards Partners are consultants and end users
that contribute to preparation of design standards
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Pump Intake Design Standard
• HI has released an updated
Pump Intake Design Standard
(ANSI/HI 9.8-2012)
• Design Requirements – Avoid:
– Submerged vortices
– Free-surface vortices
– Excessive swirl
– Non-uniform velocity
distribution at impeller eye
– Excessive variations in velocityand swirl
– Entrained air
Image used with permission of Hydraulic Institute
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Wet Well Design
• Perhaps one of the most common sources of pump
and wastewater pumping station maintenance
problems
• Challenges – the Designer must select a type that:
– Minimizes dynamic energy and large scale water
circulation
– Avoids solids deposition
– Provides a mechanism to create turbulence in wet well
to re-entrain solids and to pump floating grease and
debris (Wastewater Pumping Stations)
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Inlet/Wetwell Configuration Design
• Applicable Hydraulic Institute Standard
– Pump Intake Design ANSI/HI 9.8-2012
• Debris Management/Removal (WW & RW)
• Wetwell Configuration Selection
• Wetwell Inlet/Pump Approach
• Redundancy/Split Wetwells
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Self-Cleaning
Trench Style
Wet Well
• Design Guidance
available from
ANSI/HI 9.8-2012 &“Pumping Station
Design” 3rd Edition
plus web resources
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Compact Rectangular Wet Well
for Solids Bearing Liquids
• In HI Intake Standard
Appendix
• Design has undergone
extensive hydraulic
modeling by HydroTec(Leeds, England) and Flygt
• Proven by extensive field
testing
• Works effectively for both
variable and constantspeed applications
Image used with permission of Hydraulic Institute and Xylem Corp.
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Example: Sugar Creek Influent Pump Station
– Physical Hydraulic Modeling
• Physical Modeling Verifies Hydraulic Design
• Modeling Required for Stations Exceeding100,000 gpm (144 mgd)
• Allows Optimization of the Design
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Pump Piping Design Standard
• HI released a new Pump Piping
Standard (ANSI/HI 9.6.6-2009)
• Valves and fittings can generatehydraulic conditions that can
adversely affect pump
performance
• Standard identifiesrecommended length of straight
pipe upstream of pump inlet
Image used with permission of Hydraulic Institute
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Pump Suction Piping
Image used with permission of Hydraulic Institute
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Pump Suction Piping
Images used with permission of Hydraulic Institute
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Vertically Mounted End-Suction Pumps
• Non-reducing elbow design
has been common practice
• Results in uneven flow
distribution to the pump
inlet• Introduces uneven loading
on impeller
• Reducing elbow has been
shown to be effective at
delivering uniformhydraulics to the pump
inlet
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Recommended Pump Suction Elbow Design
for Delivery of Uniform Flow to the Pump
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Design Guidance Recommendations
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Pump NPSH and AOR Standards
• HI has released the updated Allowable
Operating Region (AOR) standard in
2012 and Pump NPSH (Net Positive
Suction Head) will be released in 2013
• These two standards cover how toselect pumps to prevent cavitation and
apply pumps to particular operating
ranges
• For instance – why do we add margin to
NPSH3 and what is NPSH3? What isNPSH?
• AOR & POR will be discussed in the
following slides
Image used with permission of Hydraulic Institute
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Pump NPSH Margin
Image used with permission of Hydraulic Institute
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Pump Selection and Operating Ranges
• Low static head systems generally facilitate a wider range
of operating conditions
• Reduced speed pumping can cause pump clogging
– Suction recirculation – Low suction velocities
• Focus on maximizing efficiency in the most common
operating conditions, while maintaining capacity
requirements for unusual operating conditions
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Pump Selection Example for Low Static Head System
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Pump Selection Example for High Static Head System
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Common Pump Selection Mistakes – Pump Run-out
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Pump Vibration Standard
• HI released updated Pump
Vibration Standard (ANSI/HI
9.6.4-2009)
• Depicts maximum allowable
vibration levels for different
pump designs
• Specifies how field and factory
vibration tests are to be
determined
•Will have a companion tutorial
entitled “Vibration Dynamics” to
be released in 2013
Image used with permission of Hydraulic Institute
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Pump Vibration Standard
Image used with permission of Hydraulic Institute
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Pump Vibration Standard
Image used with permission of Hydraulic Institute
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Pump/Mechanical/Piping Design
How do we put this all together?
• Pump Types
• Applicable Hydraulic Institute Standards
– Pump Piping
– Vibration
• Suction Piping
• Discharge Piping/Pump Supports/Shafting
• Pump Selection
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Suction Piping & Inlet Design – Intake Design
Combine Intake & Pump Piping
Image used with permission of Hydraulic Institute and Xylem Corp.
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Discharge Piping/
Pump Supports/Shafting
Hydraulics
– Pump suction elbows
and reducers can be
problematic
– Air entrainment,pre-swirl, non-uniform
flow distribution, vortices
– Poor piping design can
contribute to ragging &vibration
– Proper pump selection
– NPSH - cavitation
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Discharge Piping/
Pump Supports/Shafting
Flexible Couplings
& Pipe Supports
– Reduce rigidity
of system
– Introduce lateralload opposite the
pump discharge
– HI requires that
loads on suctionand discharge
nozzle be
minimized
h /
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Discharge Piping/
Pump Supports/Shafting
Pump Supports – Major contributor to pump vibration
– Steel frames provided bymany manufacturers lack
adequate stiffness – Addition of steel cross
members is effective forvibration control, but limitsaccess
– Construction of base iscritical to minimizingvibration - proper grouting,securing anchor bolts, etc.
/
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Discharge Piping/
Pump Supports/Shafting
• Use of concrete pump
supports preferred
• Provide concrete pedestal
type pipe supports
•Avoid use of flexible
expansion joints unless
seismic considerations
require use
• Pipe restraint must be
designed to reduce thrust
loading and other forces on
pump nozzles below
manufacturers limits
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Vertically Mounted WW Pump Base
• Use concrete pedestals
instead of steel frames
whenever practical
• Designer must provide
space for suction elbow
and maintenance
access
Di h Pi i /
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Discharge Piping/
Pump Supports/Shafting
What is a “Critical Speed”• System natural frequency is equal to a resonance
generated by the pump i.e., pump speed, vane-pass
frequency, etc.
– Variable speed systemsare especially vulnerable
to this problem
– Often system is
modified to move
natural frequency
out of operating range
– Can also speed limit
or exclude speeds
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Vibration and Critical Speed Limitations
• Finite Element Analysis
– What is a Finite Element Analysis (FEA)?
• Computer model of mechanical equipment to predict natural
frequencies and equipment or structure behavior when excited
– FEA should normally be performed for pumps greater than 100HPand of a critical nature
– FEA should only be performed by qualified firms
– Investment in FEA is a proactive approach similar in philosophy to
Physical Intake Model
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Life Cycle Cost Analysis
• Secure Financial Information
on Facility
• Use Appropriate Software or
Spreadsheet to Analyze PumpFacility
• Use Hydraulic Institute Text as
Guide
Image used with permission of
Hydraulic Institute
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Comparison of facilities
over 20 years
• Cost of Money
• Lowest First Cost
• Not the most Efficient
Pump/MotorCombination
• Fiberglass Wet Well
and Valve Vault
• Lowest Cost Valves
• Thin Wall PVC Pipe
• Cost of Money–Same?
• Higher Equipment Cost
• Most Efficient
Pump/Motor/VFDEquipment Available?
• Concrete Wet Well & Vault
with Coatings
• First Quality Accessories
• Ductile Iron Pipe
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Questions?