AS 2885.1 2007

Pipeline design in high consequence areas

Compliance with AS 2885 in an area subject to encroachment

PIPELINE DESIGN IN HIGH CONSEQUENCE AREAS

• General principles

• Specific requirements

• Application of principles & requirements

GENERAL PRINCIPLES

0.2 BASIS OF THE AS 2885 SERIES OF STANDARDS

The fundamental principles …are as follows:

(a) … ensure the safety of the community, protection of the environment and security of supply.

(b) … designed and constructed to have sufficient strength, ductility and toughness to withstand all planned and accidental loads … during … operation.

etc.

GENERAL PRINCIPLES

Appendix G ALARP

• Costs disproportionate to benefits

• What else can I do?

• Why haven’t I done it?

DESIGN Specific requirements

• 4.7 SPECIAL PROVISIONS FOR HIGH CONSEQUENCE AREAS• 4.7.1 General

• Locations …where special provisions are necessary to limit the consequence of pipeline failure on the community or the environment.

• For gas pipelines, the consequence is likely to result from ignition of the fluid released.

• For oil pipelines the environmental consequence may be dominant.

DESIGN Specific requirements

4.7.2 No rupture

Residential (T1), High Density (T2) Industrial (I), Heavy Industry (HI) and Special (S)

Design such that rupture is not a credible failure mode.

Either:(a) The hoop stress does not exceed 30% of SMYS or;

(b) Critical defect length at MAOP is not less than 150% of the axial length of the largest equivalent defect produced by the threats identified in that location.

Definitions of T1 etc are in 4.3 CLASSIFICATION OF LOCATIONS

DESIGN Specific requirements

4.7.3 Maximum discharge rate

All LocationsConsideration shall be given to … limiting the maximum discharge

rate..

High Consequence Locations .. jet fires or vapour cloud fires … maximum allowable discharge rate

shall be determined and shall be approved.

Flammable gases, HVPLs & liquids with flash point < 20°C… maximum allowable discharge rate shall not exceed • 10 GJ.s-1 in Residential, Industrial and Sensitive locations or • 1 GJ.s-1 in High Density locations. .

DESIGN Application of principles & requirements X80 pipe with 0.8 design factorCity gate with 15.3 MPa upstream and 10.2 MPa downstream

Minimum pressure thickness, 10.2 MPa 4.7 mmMinimum pressure thickness, 15.3 MPa 7.1 mm

Reasonable penetration resistance (B=1) 8.4 mmAbsolute penetration resistance (B=1.3) 11.0 mm

No rupture, 10.2 MPa 8.4 mmNo rupture, 15.3 MPa 11.0 mm

Rural areas upstream of city gate 7.1 mmRural areas downstream of city gate (if any) 4.7 mm Elsewhere downstream of city gate 8.4 mmT2 or sensitive areas 11.0 mm

DESIGN Application of principles & requirements

T1 DOWNSTREAM OF CITY GATE (10.2 MPa, 8.4 mm)

• No Rupture– OK ?

• Energy Release Rate– Maximum credible hole size?

• Excavator (B=1) ?• Borer?????

– Release rate?• < 10 GJ.s-1?

Energy Release Rates (GJ.s-1)

1 MPa 2 MPa 3 MPa 5 MPa 7 MPa 10 MPa

25 mm 0.05 0.09 0.14 0.23 0.32 0.46

50 mm 0.18 0.37 0.55 0.92 1.29 1.85

100 mm 0.74 1.48 2.22 3.69 5.17 7.39

150 mm 1.66 3.32 4.99 8.31 11.63 16.62

250 mm 4.62 9.23 13.85 23.08 32.31 46.16

DESIGN Application of principles & requirements

T2 DOWNSTREAM OF CITY GATE (10.2 MPa, 11.0 mm)

• No Rupture– OK

• Energy Release Rate– Maximum credible hole size?

• Excavator (B=1.3) – N/A• Borer?????

– Release rate?• < 1 GJ.s-1?

Compliance with AS 2885 in an area subject to encroachment

• General principles - unchanged

• Specific requirements

• Application of principles & requirements

ENCROACHMENT Specific requirements

4.7.4 Change of Location Class

If location becomes Residential, High Density, Industrial, Heavy Industry or Sensitive , must

• Do safety assessment• Implement additional measures• Demonstrate risk of rupture is ALARP.

Must consider• MAOP reduction• Pipe replacement • Pipeline relocation• Modification of land use • Extra physical and procedural measures

Must demonstrate • Cost of alternative is grossly disproportionate to the benefit.

ENCROACHMENT Application of principles & requirementsR2 DOWNSTREAM OF CITY GATE CHANGES TO T1

• No Rupture ?– NOT OK (Wall is 4.7 mm, need 8.4mm for no rupture

at 10.2 MPa)

• Risk of Rupture ALARP?– (a) Reduce MAOP?– (b) Replace pipe?– (c) Relocate Pipe?– (d) Modify land use?– (e) Improve protection measures?

ENCROACHMENT Application of principles & requirements

Highett Gasworks

• 2.8 MPa assets below ground

• Courthouse under construction

• Land adjacent to regulator pits to be used for medium rise residential development

ENCROACHMENT Application of principles & requirements

Melbourne Docklands

• Former West Melbourne Gasworks

• 2.8 MPa assets above and below ground– MAOP maintained– Some assets relocated – Remaining assets buried – Notification zone around regulator pits– Restrictions on building and other uses

QUESTIONS?