The Engineering World Of Thermoplastic Piping

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Design of Piping Systems Using Thermoplastic Materials

Design of Piping Systems Using Thermoplastic Materials

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  • 1.
    • Presented By
    • Geoffrey D Stone C.Eng FIMechE; CP Eng FIEAust RPEQ
    • Design Detail & Development
    • http://waterhammer.hopout.com.au/                  Skype address geoffrey.stone@yahoo.co.uk
  • 2.
    • Thermoplastic Pipe Design
    • Material Properties
    • Waterhammer Analysis
    • Issues arising in design, fabrication, installation & testing
  • 3.
    • 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
  • 4.
    • What 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
  • 5.
    • 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
  • 6.
    • 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
  • 7.
    • 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
  • 8.
    • Fittings do NOT meet all pipe classes
    • Injection moulded fittings
    • Manufactured fittings
      • Tees
      • Bends
    • Flanges- Composite Metallic and Plastic
    • Gaskets
    • Expansion Bellows
    • Saddles
  • 9.
    • 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
  • 10.
    • Coefficient of thermal expansion
    • Modulus affects loading
    • Friction
    • Use of elbows and bends
    • Stress intensification factors
    • Elastic follow up/strain concentration
    • Ratcheting
  • 11.
    • To reduce loads
    • Impact on stress cannot be included
    • Installed versus Service Temperature
    • Supports
    • Signage
  • 12.
    • Specialist engineering required
    • National codes apply
    • 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
  • 13.
    • Benefits of Thermoplastic Pipe
    • Low modulus hence low wave speed (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
  • 14.
    • Modulus
    • Hoop stress
    • Ring bending strain
    • Creep
    • Stiffness
    • Temperature variation
    • Design life
    • Toxicity & taint
    • Abrasion resistance
    • Chemical resistance
    • Ultraviolet resistance
    • Comparison with other materials
  • 15.
    • Data is published at 20 ºC only
    • Values determined by ASTM test
      • Standard dog bone test specimen
      • Fixed strain rate
    • Values at other temperatures required for design
    • Strain rate changes modulus value
    • Resin properties changes values
    • Short term property needed to determine maximum loads and transient pressures
    • Long term property used to determine maximum deflection
  • 16.
    • Importance of Strain
    • Comparison thermoplastic materials
      • ABS 1%
      • FRP 0.2 to 0.6 %
      • PE 4.0%
      • PVC-U 1%
      • PVC-O & PVC-M1.3%
  • 17.
    • Variation of properties in time
    • Long term loading/stress relaxation
    • Reverse loading/stress magnitude
    • Repetitive loading/fatigue
  • 18.
    • The design temperature may vary due to:-
      • Ambient diurnal temperature
      • Flow rate
      • Fluid temperature range
      • Installation ambient temperature
      • Exothermic chemical reaction
  • 19.
    • Design life criteria is 50 years
    • 50 year does not mean the pipe has a 50 year life span
    • 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
  • 20.
    • 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  Velocity (2.5-4.5)
    • E = 6.1 dm 2.15 . U 3.7
    • Where :-
    • E = wear rate (at bottom of pipe, mm/year
    • dm = mean particle size,
    • U = mean slurry velocity, m/s
  • 21.
    • 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
  • 22.
    • Coefficient of Thermal Expansion
  • 23.
    • Design
    • Fabrication
    • Installation
    • Testing
    • Product quality
  • 24.
    • 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 pipe class than necessary specified to save costs
  • 25.
    • 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
    • Lack of training or supervision
  • 26.
    • Spools forced to fit
    • Designed supports missing or modified
    • Insufficient clearance in clamps & guides
    • Variations from design not engineered
    • Surfaces contaminated
    • Physical damage
    • Other services supported from pipes
    • Incorrect slings
    • Insufficient weld time
    • Lack of training or supervision
  • 27.
    • Excessive hydrotest pressures
    • Lack of planning & procedure
    • Standard provisions not understood
    • Inexperienced testers
    • Test pressure unknown
    • Equipment not isolated
    • Premature testing
    • Records of test not prepared
    • Person to witness test not available
    • Equipment not available
      • Water supply
      • Pump
      • Gauges
      • Data logger
      • Temperature instrument
  • 28.
    • 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
  • 29.