AASHTO’S NTPEP HDPE Thermoplastic Pipe and Rebar Auditing Program
Thermoplastic Pipe Design Material Properties Waterhammer ...
Transcript of Thermoplastic Pipe Design Material Properties Waterhammer ...
Design of Thermoplastic PipingDesign of Thermoplastic Piping
� Thermoplastic Pipe Design � Material Properties� Waterhammer Analysis� Issues arising in design, fabrication,
installation & testing
Thermoplastic Piping DesignThermoplastic Piping Design
Codes & Standards� Hydraulic Analysis� Selection of Pipe
Class� Fittings Class� Piping Layout
� Thermal: Expansion/Contraction
� Cold Cut & Pull� Unsustained Loads
– Wind
– Earthquake
– Ship Pitch & Roll
– Vibration
Role of the Thermoplastic Pipe Role of the Thermoplastic Pipe Customer & SupplierCustomer & SupplierWhat Customer Expects
� Material Properties� Design Criteria� Design Guidance� Material take off (MTO)� Applicable Standards� Final Inspection� Supplier to take the
design risk!!!
What Supplier avoids
� Taking the design risk� Taking the MTO risk
Thermoplastic Piping DesignThermoplastic Piping Design
� International and national standards do not define the design requirements adequately for thermoplastic pipe systems
� Hoop stress is the primary design parameter� Manufacturers heavily relied upon to provide design
assistance� Material properties vary between manufacturers and resin
used but are generally consistent to meet standards� Properties isotropic� Thermal strain significant for applications� NDE technology is not available� Testing is defined in material standards
Thermoplastic Piping DesignThermoplastic Piping DesignCodes and StandardsCodes and Standards� Australian standards are material specific for
products and cover above ground installation� ISO 15493 Plastics piping systems for industrial
applications — Acrylonitrile-butadienestyrene (ABS), unplasticized poly(vinyl chloride) (PVC-U) and chlorinated poly(vinyl chloride) (PVC-C) — Specifications for components and the system ―Metric series
� AS 4041 Pressure Piping Code� ASME B31.3 Chemical & Refinery Piping Code
The Selection of Pipe ClassThe Selection of Pipe Class
� Design Pressure Steady State
� Design Pressure Unsteady State
� Vacuum Conditions� Industry Application
& Environment
� Support distances for deflection
� Wear from abrasive slurries
� Standardization of classes on site
� Risk– Likelihood– Consequences– Responsibility
FittingsFittings
� Fittings do NOT meet all pipe classes� Injection moulded fittings� Manufactured fittings
– Tees– Bends
� Flanges- Composite Metallic and Plastic� Gaskets� Expansion Bellows� Saddles
Piping LayoutPiping Layout
� Piping connecting equipment
� Flexibility� Physical damage� Number and type
Fittings� Loads on nozzles� Horizontal or vertical� Straight lengths
– Flow metering– Pump suctions
� Supports– Use existing steelwork– Saddles-Local Stresses– Springs– Hangars– Concentrated weights
� Maintenance – Pipework– Equipment
� Erection� Access� Cost
ThermalThermal-- Expansion/ContractionExpansion/Contraction
� Coefficient of thermal expansion� Modulus affects loading� Friction� Use of elbows and bends� Stress intensification factors� Elastic follow up/strain concentration� Ratcheting
Cold Cut & PullCold Cut & Pull
� To reduce loads� Impact on stress cannot be included� Installed versus Service Temperature� Supports
Unsustained LoadsUnsustained Loads
� Specialist Engineering� National Codes � Local Conditions� Risk
- Likelihood
- Consequences
- Responsibility
- Safeguarding
� Earthquake– Building Influence
� Wind– Height of external
piping– Shading from buildings– Supports
� Vibration� Shock� Ship Pitch & Roll
– Ship’s Data
Waterhammer Analysis & DesignWaterhammer Analysis & Design
Benefits of Thermoplastic Pipe
� Low modulus hence low wavespeed (celerity) and hence low increased pressure
� Instantaneous stress property values
� Vacuum Resistance� Fatigue Resistance
Disadvantages of Thermoplastic Pipe
� Low pressure rating� Low surface
roughness delays pressure decay
� Longer valve closure times because reflection times increased
Material PropertiesMaterial Properties
� Modulus� Hoop Stress� Ring Bending Strain� Creep� Stiffness� Temperature
Variation
� Design Life� Toxicity & Taint� Abrasion Resistance� Chemical Resistance� Ultraviolet
Resistance� Comparison with
Other Materials
ModulusModulus
� Published at 20ºC only� Value determined by ASTM test
– Standard dog bone test specimen
– Fixed strain rate� Values at other temperatures required for design� Strain rate changes values � Resin properties changes values� Property affects wavespeed in surge events� Property needed to determine deflection and loads
Ring Bending StrainRing Bending Strain
� Importance of Strain� Comparison to other materials
– ABS 1%– Steel & DICL Not relevant– FRP 0.2 to 0.6 %– PE 4.0%– PVC-U 1% – PVC-O 1.3%
CreepCreep
� Variation of properties in time� Long term loading/stress relaxation� Reverse loading/stress magnitude� Repetitive loading/fatigue
TemperatureTemperatureThe design temperature may vary due to:-
• Ambient diurnal temperature• Flow rate• Fluid temperature range•Installation ambient temperature
Design LifeDesign Life
� Design life criteria 50 years� 50 year does not mean the pipe has a 50
year life� 50 Years is an arbitrary period to provide
comparative data� No matter how old it is the pipe will still
exhibit instantaneous properties similar to when it was made when subjected to high rates of strain
Abrasion ResistanceAbrasion Resistance
� Size distribution of particles
� Concentration of solids by volume
� Relative density of solids� Shape of particles� Sharpness of particles� Flow regime affecting
angle of impingement, sliding bed etc
� Temperature of fluid� Velocity of slurry� Chemical resistance
Some relationships predicting wear in pipelines:
Wear αααα Velocity (2.5-4.5)
E=6.1 dm^2.15*U^3.7
Where :-E= wear rate (at bottom of pipe,
mm/yeardm = mean particle size, U= mean slurry velocity, m/s
Chemical ResistanceChemical Resistance
� Offer high chemical resistance� Preferred materials for particular processes� Chemical resistance charts are a guide only� Contaminated fluids can be highly corrosive� Stress test recommended� No pickle & passivation as in stainless steel� No cathodic protection needed� No corrosion inhibitors
Comparison of MaterialsComparison of Materials
� Coefficient of Thermal Expansion
Tips Tricks & TrapsTips Tricks & Traps
� Design� Fabrication� Installation� Testing� Product quality
Design IssuesDesign Issues
� Design pressure does not include surge� Temperature profile not defined� Design layout not adequately drawn� Supplier has to provide more than
guidance in design� Consultant expects sub contractor to do
detail design� Lower class than necessary specified to
save costs
Fabrication IssuesFabrication Issues
� Inadequate detail drawings� Insufficient joints for erection� Incomplete insertion in solvent welded or electro
fusion joints� Inadequate time for butt fusion welds� Contaminated electro-fusion welds� Belief that all pipe can be site run rather than
designed
Installation IssuesInstallation Issues
� Spools forced to fit� Designed supports
missing or modified� Insufficient clearance
in clamps & guides� Variations from
design not engineered
� Surfaces not cleaned
� Physical damage� Other services
supported from pipes� Incorrect slings� Insufficient weld
time
Testing IssuesTesting Issues
� Excessive hydrotest pressures
� Lack of planning & procedure
� Standard provisions not understood
� Inexperienced testers� Test pressure unknown� Equipment not isolated
� Records of test not prepared
� Person to witness test not available
� Equipment not available– Water supply
– Pump
– Gauges
– Data logger
– Temperature instrument
Product QualityProduct Quality
� Virgin material or % regrind� Standard compliance� QA documents� Inspection at works or on site� If the price is low then you may not get
what you expect
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