the engineering world of thermoplastic piping
DESCRIPTION
Design of Piping Systems Using Thermoplastic MaterialsTRANSCRIPT
Presented By Geoffrey D Stone C.Eng FIMechE; CP Eng FIEAust RPEQ
Design Detail & Development
http://waterhammer.hopout.com.au/ Skype address [email protected]
Thermoplastic Pipe Design Material Properties Waterhammer Analysis Issues arising in design, fabrication,
installation & testing
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
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
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
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
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
Fittings do NOT meet all pipe classes Injection moulded fittings Manufactured fittings
Tees Bends
Flanges- Composite Metallic and Plastic Gaskets Expansion Bellows Saddles
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
Coefficient of thermal expansion Modulus affects loading Friction Use of elbows and bends Stress intensification factors Elastic follow up/strain concentration Ratcheting
To reduce loads Impact on stress cannot be included Installed versus Service Temperature Supports Signage
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
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
Modulus Hoop stress Ring bending strain Creep Stiffness Temperature
variation
Design life Toxicity & taint Abrasion resistance Chemical
resistance Ultraviolet
resistance Comparison with
other materials
Data is published at 20ºC 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
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%
Variation of properties in time Long term loading/stress relaxation Reverse loading/stress magnitude Repetitive loading/fatigue
The design temperature may vary due to:-
• Ambient diurnal temperature• Flow rate• Fluid temperature range•Installation ambient temperature•Exothermic chemical reaction
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
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 dm2.15 . U 3.7
Where :- E = wear rate (at bottom of
pipe, mm/yeardm = mean particle size, U = mean slurry velocity, m/s
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
Coefficient of Thermal Expansion
Design Fabrication Installation Testing Product quality
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
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
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
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
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