Standard
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AS/NZS 4645.2:2018
[Current]Gas distribution networks, Part 2: Steel pipe systems
Specifies materials, design, construction, installation, testing and maintenance requirements for steel piping systems and is to be used in conjunction with AS/NZS 4645.1, for the distribution of fuel gas suitable for domestic, commercial or industrial uses.
Published: 28/02/2018
Pages: 67
Table of contents
Cited references
Content history
Table of contents
Header
About this publication
Preface
Foreword
1 Scope and general
1.1 Scope
1.2 Normative references
1.3 Application
1.4 Definitions
2 Materials and components
2.1 New materials and new components
2.2 Materials and components identification
2.3 Pipe threads, threaded pipe fittings, flanged pipe joints and welded pipe joints
2.4 Valves, fittings and accessories
2.4.1 General
2.4.2 Flanges and flanged fittings
2.4.3 Gaskets and ring joints
2.4.4 Valves
2.5 Coating for buried metal mains or services
3 Design
3.1 General
3.2 Maximum allowable operating pressure (MAOP)
3.3 Hoop stress
3.4 Mains and services
3.4.1 Wall thickness
3.4.1.1 Nominal wall thickness (tN)
3.4.1.2 Required wall thickness (tW)
3.4.1.3 Allowances (G)
3.4.1.4 Resistance to penetration
3.4.1.5 Pipe manufacturing tolerance (H)
3.5 Steel casing
3.6 Warning markers for mains and services
3.7 Offset distances
3.8 Depth of cover
3.9 Separation from other utility assets
3.10 Corrosion mitigation
3.11 Electrical hazards
3.12 Expansion and flexibility
3.12.1 General
3.12.2 Supports
3.12.2.1 Anchoring
3.12.2.2 Flexibility
3.12.2.3 Vibration
3.12.2.4 Material for supports
3.12.2.5 Forces on pipe joints
3.12.2.6 Attachment of supports or anchors
3.12.2.7 Interference
3.12.2.8 Electrical insulation
3.13 Bends, elbows and mitres
3.14 Components and fabricated assemblies
4 Welding
4.1 General
4.2 Safety
4.2.1 General
4.2.2 Welding safety
4.3 Welding consumables and gases
4.3.1 Welding consumables
4.3.2 Storage and handling of consumables
4.3.3 Gases or gas mixtures
4.4 Welding requirements
4.4.1 General
4.4.2 Environmental conditions
4.4.3 Alignment of parts for welding
4.4.3.1 Accuracy of alignment
4.4.3.2 Use of line-up clamps
4.4.3.3 Use of tack welds
4.4.3.4 Misalignment and root gap
4.4.4 Preheating
4.4.4.1 Need for preheating
4.4.4.2 Extent of preheating
4.4.4.3 Inter-run temperature
4.4.4.4 Verification of preheating temperature
4.4.4.5 Condensation
4.4.4.6 Dissimilar materials
4.4.5 Inter-run cleaning
4.5 Types of welding
4.5.1 Butt welds
4.5.1.1 Butt welds between parts of equal thickness
4.5.1.2 Butt welds between parts of unequal thickness
4.5.1.3 Welding passes
4.5.1.4 Post weld heat treatment (PWHT)
4.5.2 Fillet welds
4.5.2.1 Dimensions of a fillet weld
4.5.2.2 Fillet welding a lug, boss, pig bar or pad
4.5.2.3 Sleeve fillet welds
4.5.2.4 Welding passes
4.5.2.5 Post weld heat treatment (PWHT)
4.5.3 Attachment of electrical connections
4.5.3.1 Aluminothermic welding
4.5.3.1.1 Aluminothermic welding without qualification
4.5.3.1.2 Aluminothermic welding with qualification
4.5.3.2 Pin brazing
4.5.3.3 Production testing of electrical connections
4.5.3.4 Fillet welding lug, boss or pad
4.6 Qualification of welding procedure
4.6.1 General requirements
4.6.2 Essential variables
4.7 Qualification testing of welded joints
4.7.1 Non-destructive testing
4.7.2 Destructive testing
4.7.2.1 Tensile strength
4.7.2.2 Macro test
4.7.2.3 Charpy V-notch test
4.7.2.4 Transverse side-bend test
4.7.2.5 Hardness test
4.8 Welder qualification
4.8.1 General
4.8.2 Methods of qualification
4.8.3 Extent of approval of welder qualification
4.8.4 Records of welder qualification
4.8.5 Retesting
4.8.6 Essential variables for the qualification of welders
4.9 Inspection and testing of production welds
4.9.1 General
4.9.2 Non-destructive testing
4.9.3 Identification of production welds
4.10 Visual examination
4.10.1 Purpose
4.10.2 Criteria of acceptance
4.10.2.1 All-welds
4.10.2.2 Alignment (high/low)
4.10.2.3 Undercut depth measurements
4.11 Rectification of welds
4.11.1 General
4.11.2 Methods of removal
4.11.3 Authority for repairs
4.11.4 Repair procedure
4.11.5 Re-welding
4.12 In-service welding
4.12.1 General
4.12.2 Risk assessment
4.12.3 Welding
4.12.3.1 General
4.12.3.2 Preparation for welding
4.12.3.3 Inspection prior to welding
4.12.3.4 Prohibited during welding
4.12.3.5 Electrodes
4.12.3.6 Preheating
4.12.3.7 Fit-up prior to welding
4.12.3.8 Welding sequence
5 Construction and installation
5.1 Handling and storage
5.1.1 Storage
5.1.2 Transportation
5.1.3 Lifting
5.2 Protection
5.2.1 Covering ends
5.2.2 Insulated joints
5.2.3 Valves
5.3 Burial
5.3.1 Alignment
5.3.2 Stresses induced during laying
5.3.3 Width of trenches
5.3.4 Grading
5.3.5 Support and lowering of mains or services
5.3.6 Protection of coatings
5.3.7 Padding
5.3.8 Backfilling
5.3.9 Cleaning internally
5.3.10 Reinstatement
5.4 Trenchless installation
5.4.1 General
5.4.2 Trenchless procedures
5.4.3 Insertion
5.5 Positioning of valves
5.6 Identification of valves
5.7 Electrical hazards during construction
6 Pressure testing
6.1 General
6.2 Safety
6.3 Testing program
6.4 Strength test
6.4.1 Minimum test pressure
6.4.2 Maximum test pressure
6.4.3 Testing at operating pressure
6.5 Leak testing
6.5.1 General
6.5.2 Preparation of the test section
6.5.3 Preparation of the testing equipment
6.5.4 Pressurization
6.5.5 Test procedure
6.5.6 Hold period
6.5.7 Assessment of pressure test
6.6 Disposal of test fluid
6.7 Reports and records
7 Commissioning
7.1 General
7.2 Planning
7.3 Purging (Introduction of combustible gas)
8 Maintenance
8.1 General
8.2 Corrosion mitigation
8.3 Electrical hazards
Appendix A
A1 General
A2 Direct purging
A2.1 Overview
A2.2 Staged approach
A3 Gradual approach—Constant orifice pressure method
A4 Branch purging—Gradual approach—Constant pressure method
A5 Orifice sizing calculations
A5.1 General
A5.2 Calculation assumptions
A6 Alternative method—Gradual approach—Varying pressure method
Appendix B
B1 General
B2 Volumetric displacement methods
B2.1 Metering method
B2.2 Bubble leak detector method
B3 Pressure loss methods
B3.1 Direct method
B3.2 Differential method
Bibliography
Cited references in this standard
API 623
Steel Globe Valves—Flanged and Butt-welding Ends, Bolted Bonnets
[Current]
Welding consumables — Covered electrodes for manual metal arc welding of high-strength steels — Classification
API 609
Butterfly Valves: Double flanged, Lug and Wafer-type
API 599
Metal Plug Valves—Flanged, Threaded, and Welding Ends
API 598
Valve Inspection and Testing
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