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HDPE Pressure Pipe Occasional and Recurring Surge Design Considerations Mark Knight PhD, P. Eng. University of Waterloo
Camille George Rubeiz, P.E. Plastics Pipe Institute
Larry Petroff, P.E. Plastic Pipe Consultant
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Developers of Industry Leading Design Tools • BOREAID –
• Full commercial licenced HDD design tool – Fall 2013 a Vermeer Product
• free web based HDD PE pipe design tool – limited version of BOREAID
• free web based HDPE and PVC pressure pipe calculator that follows ASTM and AWWA standards
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Disclaimers • I am a product independent academic and researcher • I am not paid to represent any pipe manufacturers or suppliers
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Confused Plastic Pipe Industry Different terminology for HDPE and PVC Pressure Class (PC) vs Pressure Rating (PR) DIOD, CIOD, IPS, DIPS
HDPE vs PVC marketing Lack of industry understanding of ASTM and AWWA design methods
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HDPE and PVC Pressure Pipe Design Standards ASTM F714
AWWA C901
AWWA C906
AWWA C900/C905
PE3608 PE 4710 @ 1000 psi
PE3608 PE 4710 @1000 psi
PE3608 PE4710 @800 psi
PVC12454 PVC12454 @ 2000 psi PVC12454
HDPE Pipe Resin = PE3608 and PE4710 PVC Pipe Resin = PVC12454
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Plastic Pressure Pipe Design PIPE Design Input Properties Velocity
Min ID
Flow
Pressure
Disinfectant
Complete Operational Design Working and Surge Pressure Analysis
Complete Life Cycle Design Analysis Fatigue – Determine No. of cycles to failure over design life
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Working Pressure Design
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Hydrostatic Design Stress (HDS) HDPE ASTM F714 PE4710 PE3608 PVC12454
AWWA C901
1000psi
PVC AWWA C906
AWWA C900/C905
800psi
800psi 2000psi
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Pressure Class (PC) @ 73oF PC = 2 HDS/(DR-1) HDS = Hydrostatic Design Stress DR = Dimension Ratio = OD/tmin
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Allowable Pressure Design PVC AWWA C900/C905
HDPE AWWA M55 WPR
PC x FT
WPR + Pos
2.0 x PC x FT
1.6 x PC x FT
WPR + PRS
1.5 x PC x FT
PC x FT
WPR = Working Pressure Rating POS = Occasional Surge PRS = Recurring Surge
Temperature Factors (FT)
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Temperature Factors (FT) HDPE AWWA M55 FT 1.0 0.9 0.8
PVC AWWA C900/C905
Continuous Long-Term Temperature
< 81oF 81 – 90oF 91-100oF
80oF 90oF 100oF
FT 0.88 0.75 0.62
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Allowable Design Pressure Example PC = 2 HDS/(DR-1) HDPE DR-17 ASTM F714 PE 4710 PE 3608 PVC 12454
AWWA C901
125 psi
AWWA C906
PVC DR-18 AWWA C900 C905
100 psi
100 psi 235 psi
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Surge Design (Wing Flex Design)
What are the major design Issues for Wing design?
Typical Pressure Fluctuation from Sudden Valve Closure in DR 11 Pipe Pressure (bar)
Load Rate ~ 120 psig/sec
Time (seconds) G.P. Marshall, S. Brogden, M.A. Shepherd (1998) “Evaluation of the Surge and Fatigue Resistance of PVC and PE Pipeline Materials for use in the U.K. Water Industry”, Plastics Pipe X, Goteburg, Sweden 14
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Surge Design Design system such that it can withstand the highest expected surge load event over its design life While a full transient analysis is recommended, a full flow stoppage at the max. flow velocity provides a good basis for considering surge events.
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Surge - Analysis Joukowsky Equation: Ps = a(ΔV/2.31g) Ps = surge (psi) a = wave velocity (ft/s) ΔV = change in velocity (fps) g = acceleration due to gravity (32 ft/sec2)
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What are Typical Network Water Velocities? Jana Lab survey of 51 water utilities determined: Average Maximum Design Velocities for Normal Flow Average Maximum Design Velocities for Fire Flow
Jana Lab Water Velocity Survey http://plasticpipe.org/pdf/mid-fatigue-plastic-water-pipe-01-12-12
Maximum Design Velocity for Normal Flow (fps) 25
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Average = 6.7 fps
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0 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51
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Fatigue Design Recurring surges: frequently occurring surges caused by normal pipe operations like opening and closing of pumps and valves, … AWWA PE M55 “may occur up to millions of times in a piping system’s lifetime” AWWA PVC C905-10
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Fatigue Design Occasional surges: Caused by emergency operations Often “the result of a malfunction, such as a power failure or system component AWWA PE M55 failure …”
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PVC Fatigue Design PVC design fatigue life is determined using AWWA C900 and C905 Appendix B. Well established method but not well understood in the industry. Often not performed due to analysis complexity and lack of industry understanding
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PVC Fatigue Design
HDPE Fatigue Design Fatigue surge pressure analysis in AWWA M55 Fatigue life method is not in current AWWA M55 (typically, not a limiting factor) Fatigue life method will be implemented in revised AWWA M55 PE 3608 / PE 4710 design fatigue life can be determined using fatigue curves provided in Marshall, G.P., Brogden, S: Final report of Pipeline Innovation Contract to UKWIR, 1997.
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HDPE Fatigue Design PPI-PACE methodology implemented from: • AWWA M55-2005, “PE Pipe – Design and Installation” • Jana Lab, 2012, “Fatigue of Plastic Water Pipe: A Technical Review with Recommendations for PE4710 Pipe Design Fatigue” PE4710 fatigue S-N curves data from: • Resistance of PE4710 Piping to Pressure Surge Events in Force Main Applications, PP XVI, Barcelona, 2012 • UK Water Industry IGN 4-37-02 “Design Against Surge and Fatigue Conditions for Thermoplastic Pipes”
PE4710 Recurring Surge Pipe Tests ( cycles 0 to 1.5 x PC) Test Specimens
Cycles at 1.5 x PC (Recurring Surge)
Status
11,213,023 Straight Pipe
10,038,073 6,754,833
Pipe with buttfused joint
10,952,363
No Failures
11,017,153
Tests conducted by Jana Labs See Crabtree et al., PPXVI, 2012 After completion pipes cycled from 0 to 2 x PC for 2739 to 6665 cycles no failures – Shows lots of life remaining
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Number of Cycles to Failure Stress for PE4710 at 1.5 x PC = 1500 psi (10.34 MPa) Jana 4 tests 4th Generation PE at 1500 psi
1450 psi
1st Generation PE
G.P. Marshall, S. Brogden, M.A. Shepherd (1998) “Evaluation of the Surge and Fatigue Resistance of PVC and PE Pipeline Materials for use in the U.K. Water Industry”, 26 Plastics Pipe X, Goteburg, Sweden
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http://ppipace.com/
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PPI-PACE: Purpose 1. Develop a user friendly, free & online pipe software 2. Provide prelim. calculations for operating pressure, surge pressure and fatigue design life. 3. Assist designers and owners in the evaluation of plastic pipe for water distribution, transmission and forcemains 4. Implement existing standards and methods: AWWA C900/C901/C905/C906,M55 and ASTM F714/D2241.
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PPI-PACE Defaults Recurring Surge Velocity Occasional Surge velocity Working Pressure Anticipated Surges per day Temperature Min. Design Life
Default 5 fps
Allowable Range 4 – 8 fps
8 fps
5 - 15 fps
70 psi
40 psi (min.)
55 cycles 57 oF 100 years
40-100 oF 50 (min.)
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UNI-BELL and PPI-PACE
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Design Example 18 inch DIPS/CIOD 160 psi Operating Pressures 4.0 fps Recurring Flow Velocity 7 fps Occasional Flow Velocity 57oF Temperature 100 Year Design Life 55 cycles/day = approx. 2 million cycles/100 yrs
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Uni-Bell Design Example
1. Why HDPE DR 7.3? DR 13.5 (PC 160) is OK
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• PE 4710 DR 13.5 (PC 160) OK • PE 3608 DR 13.5 (PC 128) NG • PVC DR 14 (PC 305) NG
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• PE 4710 DR 13.5 (PC 160) OK • PE 3608 DR 13.5 (PC 128) NG • PVC DR 14 (PC 305) NG
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Summary • HDPE and PVC are both good materials • According to existing approved design standards HDPE has much fatigue life than PVC • PPI-PACE provides a simple, easy to use plastic pipe design tool that follows existing design standard methodologies
