PowerPoint Presentation Tuft - AS2885 PIPE... · • Hydrotest. Peter Tuft - Wall Thickness AS 2885.1 Launch, February 2007 34 Allowances • Clean dry sales gas ... • Station piping

Peter TuftAS 2885.1 Launch, February 2007 1

AS 2885.1-2007

PIPE WALL THICKNESS

Peter Tuft - Wall Thickness AS 2885.1 Launch, February 2007 2

The Design Problem

• Roma - Brisbane duplication• DN 400, 450 km• Land use ranging from rural to suburban• 15.3 MPa, 10.2 MPa from city gate station• Assume X80 pipe

• Select wall thickness for:• Remote rural areas• Pipeline parallel to rural roads & highways• Road crossings• Suburban areas• Stations


Definition: Nominal WT, tN

• The “actual” thickness• As nominated on purchase order (design)• As per mill certificates (operation)• Not less than:

• Required WT plus allowances & tolerances• WT for constructability (including rounding to

standard sizes)• WT for hydrotest

• From Clause 5.4.1


Definition: Required WT, tW

• Minimum WT required for pipe in service• Greatest of WT necessary for:

• Penetration resistance• Minimum critical defect length• Stress & strain (including vehicle loads)• Fracture control• Special construction• Maintainability (eg. hot tapping)• SCC mitigation• Fatigue life• External pressure• Internal pressure • From Clause 5.4.2


• Barlow’s rule, unchanged: • Design factor FD ≤ 0.8• Lower values of FD at some locations:

• Road & rail crossings0.72• Pipeline assemblies 0.67• Bridges etc 0.67• Telescoped lines 0.60

• From Clause 5.4.3 & Table 5.4.3

WT for Internal Pressure, tP

tP =PDD

2FDσY

P

σH


Design Factor

• Design factor applies ONLY to WT for internal pressure

• Meaningless to talk about design factor in any other context


Allowances, G

• Allowances make provision for loss of thickness• Corrosion or erosion• Threading, grooving or machining

• Not commonly required, except corrosion allowance for lines carrying raw well fluids



Manufacturing Tolerance, H

• Does NOT need to be added to Required WT for pipe made from strip or plate (almost all linepipe)• Manufacturing tolerances for strip or plate are very small

• May need to be added for seamless pipe• Hole may not be concentric (up to 12.5% WT)

• Still need to specify tolerance in pipe order• Covered by API 5L for almost all cases• Special limits on manufacturing tolerance for design factors

greater than 0.72 (Clause 3.2.2 (a)(v))



Putting them all together

• Figure 5.4


Don’t …

• Calculate WT based on design factor only• Order pipe based on design pressure and

worry about the rest later• Add manufacturing tolerance (unless pipe is

seamless)• Be over-precise about penetration resistance,

critical defect size, etc• Calculations for decision support, not hard

deterministic outcomes


The Design Problem

• Roma - Brisbane duplication• DN 400, 450 km• Land use ranging from rural to suburban• 15.3 & 10.2 MPa• Assume X80 pipe

• Select wall thickness for:• Remote rural areas• Pipeline parallel to rural roads & highways• Road crossings• Suburban areas• Stations


Elements of Nominal WT

• Internal pressure• Penetration resistance• Minimum critical defect length• Stress & strain (including vehicle loads)• Fracture control• Special construction• Maintainability (eg. hot tapping)• SCC mitigation• Fatigue life• External pressure• Allowances• Manufacturing tolerance• Constructability• Hydrotest


Internal pressure

Location Design Factor

WT, 15.3 MPa

WT, 10.2 MPa

General (R1 to T2)

Road & rail crossings

Pipeline assemblies (MLVs etc)


Internal pressure


WT, 15.3 MPa

WT, 10.2 MPa

General (R1 to T2) 0.8

Road & rail crossings 0.72

Pipeline assemblies (MLVs etc) 0.67


Internal pressure


WT, 15.3 MPa

WT, 10.2 MPa

General (R1 to T2) 0.8 7.1 4.7

5.2

5.6

Road & rail crossings 0.72 7.8

Pipeline assemblies (MLVs etc) 0.67 8.4


Penetration Resistance - Rural

• Identified threat • 20 t excavator with general

purpose teeth• Min tP = 7.1 mm

• Previously showed even 4.8 mm WT is OK for the identified threat

• No need to increase WT above tP


Penetration Resistance - Urban

• Identified threat• 30 t excavator with tiger teeth

• Min tP = 4.7 mm• Backhoe with tiger teeth could

penetrate• To resist penetration:

• Require 8.4 mm for reasonable assurance

• Require 11.0 mm for complete assurance





No Rupture(Critical Defect Length)

• Require “No Rupture” in high consequence areas (urban etc) (Clause 4.7.2)

• Hoop stress ≤ 30% SMYS, or• Critical defect length (CDL) ≥ 150% max hole

• Hole size from identified threat• Data in Table M3• 95 mm hole size for both points of a tiger tooth on

30 t excavator• Required CDL ≥ 150% of maximum hole

• Must select WT so that CDL ≥ 145 mm


WT for No Rupture - 10.2 MPa

• CDL varies with WT, steel grade and MAOP• Calculate from Clause 4.8.5

• CDL for 10.2 MPa urban line:• 4.7 mm WT CDL = 55 mm• 8.4 mm WT CDL = 150 mm• 11.0 mm WT CDL = 210 mm

• 8.4 mm WT adequate for “No Rupture”• CDL ≥ 145 mm as required


WT for No Rupture - 15.3 MPa

• CDL for 15.3 MPa rural line:• 7.1 mm WT CDL = 65 mm• 8.4 mm WT CDL = 95 mm• 11.0 mm WT CDL = 145 mm

• Require 11.0 mm WT for “No Rupture”• CDL ≥ 145 mm as required• Only needed if line upstream of city gate passes

through T1 or sensitive locations






Stress & Strain

• Combined stress due to thermal & pressure effects at bends, stations, etc• Not relevant to this design problem• Covered later in the seminar

• External loads at road and rail crossings• Use API RP 1102 to calculate stresses due to

vehicle loads


Road & Rail Crossings

• Maximum design factor for API 1102• Includes internal pressure plus vehicle stress• 0.72 at designated crossings• 0.9 elsewhere (eg. farm vehicles in paddocks)

• More information on load sources & calculations in Appendix V

• For the sample design problem:• Pipe with tP based on 0.72 design factor adequate


Fracture Control

• WT affects fracture initiation• Critical defect length• Penetration resistance

• Also affects toughness required for fracture arrest• Details covered later in this seminar

• For the sample design problem:• Assume no special requirements• But check back after review of fracture control


Special Construction

• Covers almost anything where there may be special requirements, such as• Above ground or reduced cover• Road, rail & water crossings• HDDs• Tunnels• Bridges• etc

• For the sample design problem:• No special requirements





Maintainability

• Usual example is provision for future hot tapping



Stress Corrosion Cracking

• SCC influenced by hoop stress• Increased WT reduces hoop stress, may reduce

susceptibility to SCC• Heavy wall pipe sometimes specified for this

reason downstream of compressor stations (elevated temperature also promotes SCC)



Fatigue

• Fatigue influenced by stress range• Discussed in Appendix N• Increased WT reduces hoop stress, hence also

reduces absolute range of stress due to pressure cycling

• Fatigue life is long for most ordinary pipelines (>> 100 years)



External Pressure

• May be an issue for certain deep water crossings or deep HDDs

• Formulae provided in Clause 5.4.5• For the sample design problem:

• No special requirements





Allowances

• Clean dry sales gas• No internal corrosion• No erosion

• Good quality external coating plus cathodicprotection• No external corrosion allowance required



Manufacturing Tolerance

• ERW pipe, manufactured from strip• No manufacturing tolerance required

• For the sample design problem:• No special requirements for WT• But note, X80 pipe and 0.8 DF will require tighter

than standard tolerance in linepipe specification


Constructability

• May consider extra WT for HDDs etc• Outside scope of design problem scenarios

• No need to round linepipe WT to “standard”sizes• ERW pipe ordered in project quantities can be

rolled to any desired thickness• Station piping ordered in small quantities may

need to be rounded up to next standard size• For the sample design problem:

• No special requirements (except at stations)


Hydrostatic Test

• May reduce number of test sections by adding short length of heavy wall at bottom of long steep descent






Remote Rural

7.1In

tern

al

pre

ssu

re

tPtWNo other applicable

componentstN

Nil allowances & tolerance


Parallel Rural Road

7.1In

tern

al

pre

ssu

re


componentstN


Pen

etr

ati

on

re

sist

an

ce

<4.8


Rural Road Crossing

7.8In

tern

al

pre

ssu

re


componentstN


Pen

etr

ati

on

re

sist

an

ce

<4.8


Suburban General (T1)

tWNo other applicable

componentstN


Pen

etr

ati

on

re

sist

an

ce

8.4

No

Ru

ptu

re

8.4

4.7In

tern

al

pre

ssu

retP


Suburban Sensitive (S)

tW

No other applicable components

tN


Pen

etr

ati

on

re

sist

an

ce

11.0

No

Ru

ptu

re

8.4

4.7

Inte

rnal

pre

ssu

re

tP


Station Piping

tWNo other applicable

components

tN


19.2

Inte

rnal

pre

ssu

retP

Grade B, DF = 0.67

21.4

Co

nst

ruct

ab

ilit

y

Sch. 80 stock pipe

Peter TuftAS 2885.1 Launch, February 2007 45

Questions?

Documents

PowerPoint Presentation Tuft - AS2885 PIPE... · • Hydrotest. Peter Tuft - Wall Thickness AS 2885.1 Launch, February 2007 34 Allowances • Clean dry sales gas ... • Station piping