Change in Location Classifications
During a periodic operational SMS review, there are times when the primary location class that was originally assigned, might change during the life of the pipeline.
Sometimes, a change from R2 - T1 or T1 - T2 requires little or no physical change to the system, provided that risk is ALARP, as per AS 2885.6 Cl 4.2 (ii) and (iii). However, the process of reviewing the SMS and addressing the various changed or new threats and the likely increased consequences can often result in additional controls. This is because the original pipeline may not meet the design requirements for the new location class, e.g. wall thickness (penetration resistance), etc.
Licensees have to consider a range of additional controls for the new HCAs, such as previously rural areas that are subdivided and become urban (R1/R2 to T1). Typical outcomes may involve additional physical protection by slabbing; reduction in operating pressure; and increased procedural controls such as signage, patrolling and liaison. In some circumstances pipeline replacement or relocation may be considered.
This is not a replacement for reading the applicable clauses in the AS2885 suite; however here is summary of differences when location class changes from R2 - T1 or from T1 - T2.
|Item||Reference||Description||Change in location class for operating pipelines: Design Requirements R2 to T1||Change in location class for operating pipelines: Design Requirements T1 to T2 (see Note)|
|Material Characteristics (Wall thickness, toughness, penetration resistance)||AS2885.1 Various Sections||Not easily changed for operating pipelines.||Generally N/A – pipe is already installed||Generally N/A – pipe is already installed|
|Isolation plan requirements for unplanned loss of containment with ignition||AS2885.1 Clause 4.8.2||An Isolation Plan is required for all pipelines; S 4.8.2 specifies additional requirements for T1/T2.||R2: Loss of containment event not required to be addressed in isolation plan ; T1: Loss of containment event is required to be addressed in isolation plan||Isolation Plan is required for both T1 and T2; T1 and T2 same requirements|
|Spacing of Mainline Valves (Guidance only)||AS2885.1 Table 4.8.3||Guidance only + not easily changed for operating pipelines||Gas/HVPL, R2 = 30km; T1 = 15km Liquid Petroleum; R2 = As required, T1 = 15km||T1 and T2 same requirements at 15km spacing.|
|Signage Spacing and inter-visibility||AS2885.1 Table 4.10.1||Not mandatory, guidance in AS2885.1 Table 4.10.1||R2 = 250m; T1 = 100m||T1 = 100m; T2 and S = 50m|
|Fracture arrest length||AS2885.1 Table 5.3.2||R1/R2 are similar; T1/T2 are same requirements. See AS 2885.6 Cl 4.2(iii) if fracture control does not meet AS 2885.1 requirements.||R2 = 5 pipes; T1 = within initiating pipe||T1 and T2 same requirements|
|Minimum depth of cover, gas pipelines||AS2885.1 Table 5.4.2||Not easily changed for operating pipelines. Slabbing may be acceptable alternative, subject to the SMS process.||R2 = 750mm; T1 = 900mm||T1 and T2 are same at 900mm|
|External interference protection||AS2885.1 Clause 5.4.4||This section should be read in entirety, this summary does not provide enough guidance.||R2: either separation or resistance to penetration (RTP) is sufficient; T1: physical controls should include both separation and RTP||T1 and T2 requirements are the same.|
|Penetration resistance requirements||AS2885.1 Clause 5.5.2||Not easily changed for existing pipelines, other than by reducing MAOP to reduce critical defect length if "No Rupture" is required (ie, from R2 to an HCA).||R2 = no mandatory requirement ; T1 = shall meet requirements of Cl4.9 (High consequence areas)||T1 and T2 same requirements.|
|Pre-qualified design allowable||AS2885.1 Clause 5.6.5||Not allowed in T2||N/A||Not allowed in T2|
|If shallow cover allowable||AS2885.1 Clause 5.8.3||Allowed in R1 only.||Not allowed in R2 or T1||Not allowed in T1 or T2|
|As-built survey accuracy requirements||AS2885.1 Clause 10.4.3||Relaxed for R1; Not applicable to operating pipelines||N/A||N/A|
|Pressure testing with air or gas||AS2885.1 Clause 184.108.40.206||Not applicable for SMS||N/A||N/A|
|High consequence areas (HCA)||AS2885.1 Clause 4.9.1 ; AS2885.0 Clause 1.5.24||HCA includes T1, T2, I, S and E||R2 is not an HCA; T1 is an HCA.||HCA requirements already apply.|
|High Consequence Recognition (HCR)||AS2885.6 Clause 1.5.6||T1 and T2 requirements are the same||R2 is not an HCA; T1 is an HCA.||HCR requirements already apply and should be in place|
|No Rupture||AS2885.1 Clause 4.9.2 Applies to T1, T2, I, S, E and sometimes HI.||T1 and T2 requirements are the same||R2 is not an HCA; T1 is an HCA.||No Rupture requirements already apply and should be in place|
|Maximum Energy Release Rate||AS2885.1 Clause 4.9.3||Maximum allowable ERR is lower in T2||R2 is not an HCA; T1 is an HCA.||10 GJ/s in T1; <1 GJ/s in T2|
Note: A change to an “S” classification is equivalent to applying T2 (AS2885.6 C.2.4(a): “The design requirements for High Density (T2) shall apply.”). The “Sensitive Use” secondary location class recognises, in a note, that the societal risk associated with loss of containment is a dominant consideration.