The integrity of the pipeline shall be established through an inspection testing program undertaken concurrently with construction. The pipeline Licensee shall ensure that inspection and testing are undertaken as necessary during manufacture, transport, handling, welding, pipeline construction and commissioning, to ensure that the completed pipeline complies with the engineering design and relevant Standards and has the intended quality and integrity.
11.2 INSPECTION AND TEST PLAN AND PROCEDURES
The pipeline Licensee shall prepare and document a plan and procedures covering all inspections and tests required by this Standard and the engineering design. Inspections and tests shall be made in accordance with the documentation.
Corrective action shall be taken where an inspection or test reveals that specified requirements are not satisfied.
11.3 PERSONNEL
Inspectors shall have appropriate training and experience.
Inspectors shall be qualified in accordance with the relevant requirements of this Standard and as determined by the pipeline Licensee.
Each aspect of construction shall be inspected by a competent inspector to assure compliance with the engineering design.
11.4 PRESSURE TESTING 11.4.1 Application
Except for components that are exempted from field pressure testing, pipelines shall pass a strength test and a leak test.
11.4.2 Exemptions from a field pressure test
The following items may be exempted from field pressure tests:
(a) Pipes and other pressure-containing components that have been pre tested to a pressure that is not less than that specified for the strength test.
(b) Components that have not been pre tested, but have an adequate design pressure or an appropriate pressure rating complying with the Standard used for their manufacture.
(c) Tie-in welds made between hydrostatic test sections after they have been hydrostatically tested.
(d) Small bore controls, instruments and sampling piping.
11.4.3 Preliminary test
Where access for repair of any potential field pressure test failure is difficult or impracticable, or where there is an unacceptable threat to an adjacent facility or the public, pipe should be subjected to a preliminary test in accordance with this Standard, prior to installation. Locations that should be considered include—
(a) submerged crossings (permanent waterways);
(b) rail and major road crossings;
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(c) directionally drilled crossings; and (d) high consequences areas.
11.4.4 Test procedure
Strength and leak tests for the pipeline shall comply with AS 2885.5.
Strength and leak tests for stations shall comply with the design Standard as selected in accordance with Clause 6.3.
Where the use of a liquid is impracticable and subject to the requirements of Clause 11.4.6, air or a gas may be used as a test fluid.
The test procedure shall include—
(a) the maximum and minimum strength test pressures (see Clause 11.4.5);
(b) the methods for monitoring and controlling the tests;
(c) the precautions necessary to ensure the safety of the public and testing personnel; and (d) the criteria for assessment of leak tightness.
11.4.5 Strength test pressures
The minimum target pressure for strength tests of pipelines shall be determined in accordance with Clause 4.5.5.
The maximum value of the strength test pressure shall not exceed an end point selected in accordance with Clause 5.12.
The maximum value of hydrostatic test pressure in a test section shall take into account the pressure arising from the elevation difference. Requirements for the design of test sections, including the choice of maximum elevation difference, are given in Clause 5.12.
11.4.6 Testing with air or gas 11.4.6.1 General
Whenever possible, pipelines should be pressure tested using liquid as the test fluid, for safety reasons; however, it is recognized that under certain circumstances, air or gas may have to be used where it is not possible to use a liquid. The use of air or gas can be hazardous.
11.4.6.2 Safety
Where the test fluid for pressure testing is air or some other gas, a safety management study in accordance with Section 2 shall be carried out to demonstrate that risk associated with the activity is acceptable.
The failure analysis shall consider the effect of the following on the fracture control plan:
(a) The test pressure being higher than the MAOP of the pipeline.
(b) The decompression performance of air and other gases being different from that of natural gas.
Where the test fluid is air or a flammable gas, the potential for an explosion or for a fire shall be considered, including the risk of explosion from a mixture of air and hydrocarbon that may be in the pipeline or from other sources such as compressor or lubricating oil.
To ensure public safety, the test procedure shall include the following precautions:
(i) A preliminary test at a pressure within the range of 10% to 30% of the design pressure.
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(ii) Locating and eliminating leaks occurring during the preliminary test and, if necessary, repeating the preliminary test.
(iii) Controlling the test fluid temperature so as not to damage the coating.
(iv) Keeping people who are not involved in making the test at a safe distance from the test section, from when pressure is first applied until it is either reduced to atmospheric pressure or, following a successful test, to the MAOP.
(v) Choosing a test pressure appropriate to the volume and location of the test section.
The safety management study and the procedures to be implemented to ensure safety shall be approved.
NOTE: AS/NZS 3788, Appendix D, provides guidance on application, control and exclusion zones for pneumatic testing of pressure equipment.
11.4.6.3 Limitation
Testing with air or gas may be used within the limits of Table 11.4.6.3 in location Class R1 and R2.
Testing with air or gas in location Classes T1 and T2 is restricted to the testing of instrument piping, except that in T1 locations testing with air or gas is permitted when the volume of the test section is less than 2 m3 and the maximum hoop stress is less than 30%
of SMYS.
The limits in Table 11.4.6.3 may be extended in Location Class R1 where the safety management study demonstrates that the risk class is negligible and the facture resistance of the pipe is determined to be sufficient to prevent fracture propagation at the proposed test pressure.
TABLE 11.4.6.3
MAXIMUM HOOP STRESS WHEN PRESSURE TESTING WITH AIR OR GAS
Location class
Maximum hoop stress allowed as a percentage of SMYS Natural gas Inert gas or air
R1 80 80 R2 30 75
11.4.7 Pressure testing loads
AS 2885.5 specifies that where yielding is likely to occur during the strength test, the test shall be analysed using engineering software or other approved method. For a pipe acting as a beam, superimposed bending stresses require consideration.
11.4.8 Acceptance criteria
The criteria for the acceptance of strength tests and leak tests may be summarized as follows:
(a) A strength test in which the pipe withstands a specific pressure period to demonstrate the required pressure strength.
(b) A leak test consisting of one of the following:
(i) Visual assessment in which no leakage of fluid can be observed with the naked eye at the end of the hold period.
(ii) Small volume test section in which change in pressure during the hold period does not indicate leakage.
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(iii) Large volume tests for which the unaccountable pressure change is less than that nominated in the test procedure. (Determination of the acceptable unaccountable change is included in the development of the test procedure as specified in AS 2885.5.)
11.5 COMMENCEMENT OF PATROLLING
Operational patrolling of the pipeline in accordance with AS 2885.3 shall commence immediately the leak and strength tests of the pipeline are completed.
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