Pages From 117011580 Pipeline Maintenance

AS 2885.3—2001 20 S E C T IO N 5 PIP E LINE ST R UC T UR AL INT E GR IT Y 5.1 GENERAL The operating authority shall ensure that appropriate systems are identified, implemented and maintained to ensure pipeline structural integrity for the design life of the pipeline. 5.2 OPERATING AND DESIGN CONDITIONS The operating authority shall— (a) operate a pipeline only when it conveys the fluid or fluids under the conditions (including subsequent changes) for which it was designed, constructed, tested, and approved; ensure that during normal operation, the operating pressure at any point in the pipeline does not exceed the MAOP, and that transient pressure does not exceed 110% of the MAOP; ensure that the operating temperature is such that the coating temperature rating and the thermal stress limits used in the pipeline design are not exceeded; and ensure that operating conditions are such that the likelihood of stress corrosion cracking initiation or growth is minimized. (b) (c) (d) 5.3 PIPELINE INSPECTION AND ASSESSMENT 5.3.1 General Periodic inspections shall be carried out to identify actual or potential problems that could affect the integrity of the pipeline. The operating authority shall plan and perform any maintenance required to rectify and manage any such problems. Inspections shall be carried out by approved and appropriately trained and experienced personnel. The inspection and assessment of a pipeline shall include the following: (a) (b) A full visual survey of all above-ground sections of the pipeline, including supports and associated equipment, to locate and assess any defects. An audit of corrosion control facilities to assess their effectiveness in accordance with the corrosion-monitoring program required by this Standard. This includes cathodic protection systems, pipeline coatings, surge protection systems, static earth systems, and inhibitor dosing facilities. Inspections of actual or potential problems identified in the ongoing risk assessment such as river or creek crossings, areas prone to ground instability and pipe supports at bridge crossings. NOTE: Where available, intelligent pigging results should also be considered when assessing pipeline integrity. (c) (d) Inspections of any sections on the pipeline identified in the ongoing risk assessment as being of higher propensity for development of stress corrosion cracking. 5.3.2 Frequency of inspection assessment The frequency of inspection and assessment should be documented and approved and based on the past reliability of the pipeline, historical records, current knowledge of its condition, the rate of deterioration (both internal and external corrosion, coating degradation and the like), and statutory requirements. © Standards Australia www.standards.com.au The Standard is downloaded from www.bzfxw.com Standard Sharing 21 AS 2885.3—2001 5.3.3 Leakage survey and detection The operating authority shall provide for leakage detection systems or periodic leakage surveys of the pipeline in its operating and maintenance plan. The types of surveys selected shall be effective for determining whether a potentially hazardous leakage exists. The extent and frequency of the leakage surveys shall be determined by the operating pressure, piping age, class location, whether the pipeline transports gas without an odorant and the ability to detect or observe product leakage. 5.3.4 Assessment of results and appropriate action Where the integrity of a pipeline, or a section of a pipeline, is assessed as being inadequate or at immediate risk, the operator shall immediately take steps to prevent failure of the pipeline until the integrity of the pipeline is restored. Measures shall be taken to mitigate the risk of a leak or failure to the minimum. This may be by a reduction in pressure, by passing, or by carrying out temporary repairs and appropriately adjusted surveillance. 5.3.5 Internal surfaces Notwithstanding the requirements of Clause 5.3.2 where a part of any pipeline is removed for any reason, the internal surface shall be inspected to confirm the suitability of, or the requirement for, an internal corrosion control program. Suitable measures shall be implemented to address any observed problems. 5.3.6 External surfaces 5.3.6.1 Above-ground pipelines Above-ground pipelines shall be inspected for evidence of corrosion or damage to or deterioration of any anti-corrosion coatings at intervals defined in the safety and operating plan, and the rate of corrosion shall be assessed. Where the rate of corrosion will reduce the design life, remedial action shall be taken. NOTE: Suitable action may include a reduction of the design life. 5.3.6.2 Buried and submerged uncoated pipelines Buried or submerged uncoated pipelines shall be surveyed using approved techniques at intervals as specified in the safety and operating plan. Pipelines shall be inspected at positions that are not more than 1 km apart and wherever the most corrosion is expected to occur. 5.3.6.3 Buried and submerged anti-corrosion-coated pipelines Whenever any part of a buried or submerged anti-corrosion coated pipeline is exposed, it shall be inspected for corrosion and evidence of damage to, or deterioration of, any anticorrosion coatings (see Clause 5.5.2). 5.4 PIPE WALL DEFECT ASSESSMENT 5.4.1 Damaged pipework Gouges, grooves and notches less than 0.25 mm are considered harmless. Gouges, grooves and notches above 0.25 mm and up to 10% of wall thickness may be removed by grinding. The requirements for non-destructive testing (NDT) for microcracking should be assessed. Wall thickness loss due to grinding may be assessed in the same manner as corroded pipework. www.standards.com.au © Standards Australia AS 2885.3—2001 22 Unless detailed analysis has been carried out to confirm the acceptability of an anomaly, anomalies in excess of the following shall be removed, replaced or otherwise repaired: (a) (b) Dents, as described in AS 2885.1 except that the maximum depth specified may be increased to 6% of the pipe diameter. Gouges grooves and notches that are outside the criteria set out in AS 2885.1. Combined pipe wall anomalies shall be subjected to detailed assessment. NOTE: Detailed analysis may be undertaken using CSA–Z662 Oil and Gas Pipeline Systems. This allows, subject to stated conditions, repair of dents containing stress concentrators by grinding, by pipe replacement, by pressure containment sleeve, or by reinforcement sleeve. 5.4.2 Corroded pipework 5.4.2.1 General Where corrosion is detected, it shall be investigated to determine its nature, extent, depth and cause. The corrosion shall be evaluated and the current MAOP shall be confirmed. In the event that the MAOP is determined to have been compromised, a safe operating pressure shall be determined by assessment in accordance with Clause 5.4.3 and, if necessary, either a new MAOP shall be established or the corroded portion of the pipeline shall be repaired or replaced. Corroded pipelines shall be protected against further corrosion in accordance with AS 2885.1. NOTE: Figure 5.1 provides a flow chart for assessing corrosion features. 5.4.2.2 Safety precautions Great care shall be taken when work is carried out on a corroded portion of pipeline. The operating pressure shall either not exceed the pressure at which the corroded portion was subjected to at the time of identification, or it should be reduced to a safe level (initially 80% of normal operating pressure). This pressure should not be exceeded until such time as the corroded area has been cleaned and inspected, the extent and depth of corrosion has been determined and an assessment has been made of the corroded portion of the pipeline. Prior to the commencement of any activity, an approved plan shall be prepared. Where the contents of the pipeline are liquid and locked in between valves, consideration shall be given to any increase in pressure that may be caused by changes in temperature. 5.4.3 Assessment of corroded pipework 5.4.3.1 General The assessment required by Clause 5.4.2.1 shall be made by any one of the following methods: (a) (b) Calculation, in accordance with Appendix D, Paragraph D3. AGA Project PR3-805. NOTE: This program is based on the calculation method given in Appendix D, Paragraph D3 but is less conservative. (c) (d) Pressure testing, in accordance with Clause 5.4.3.2. Other approved method. © Standards Australia www.standards.com.au The Standard is downloaded from www.bzfxw.com Standard Sharing 23 AS 2885.3—2001 NOTES: 1 The design pressure (Pd) shall be calculated as follows: 2F   Pd  where Pd Fd dp d dp y D design pressure, in megapascals design factor wall thickness for design internal pressure, in millimetres yield stress, in megapascals nominal outside diameter = = = = = y 0 D 2 Test pressure = 1.25  d P FIGURE 5.1 FLOW CHART FOR ASSESSING CORROSION DEFECTS www.standards.com.au © Standards Australia AS 2885.3—2001 24 5.4.3.2 Assessment by pressure testing Where an assessment is to be made by pressure testing, the pipeline shall be tested in accordance with AS 2885.1 and its MAOP determined in accordance with Appendix D, Paragraph D2. The normal maximum pressure, recorded or determined for the corroded section over the six months prior to the discovery of the corrosion, may be deemed to be a test pressure for the purposes of recalculating the MAOP in accordance with this Clause. Where the original design included an allowance (G) (see AS 2885.1) and it can be shown that the original allowance is not required for the corroded section of pipe, a revised value for G may be used in the re calculation of MAOP. The revised value shall be approved. 5.5 COATINGS 5.5.1 Above-ground pipework Where, after inspection (see Clause 5.3.6.1), external corrosion that will compromise the integrity of the pipework before the next integrity assessment is identified, the operating authority shall take appropriate remedial action. This could include repair or renewal of the coating. Specific assessment of the coating should be made at crevice areas such as pipe supports and on the underside of the pipework. The pipe wall should also be inspected for corrosion at areas of blistered or disbonded coating. Where installed insulation shall be maintained in a condition such that— (a) (b) water cannot reach and collect next to the pipe surface; and the requisite thermal insulation performance is maintained. NOTES: 1 Corrosion under thermal or acoustic insulation can be a severe problem, especially if the pipeline is in intermittent service (i.e., subject to fluctuating temperatures encompassing the water vapour dewpoint). Inspection for corrosion under the insulation should be a regular feature of assessment surveys. 2 3 4 The coating system under insulation needs to be adequate to prevent corrosion under the conditions it will be subjected to. Corrosion within crevices between surfaces, such as at pipe support saddles, can be a severe problem, which can be difficult to identify by simple visual inspection. Coating inspection of ground entry locations should be in accordance with Clause 5.9.4. Records of the coating condition shall be kept. 5.5.2 Below-ground pipework Assessment of the coating condition on below-ground pipework shall be achieved by evaluation of some or all of the following: (a) (b) (c) Cathodic protection data. Special coating defect surveys (eg. Pearson or DC-pulsed method surveys). Visual inspection at selected locations in bellhole excavations and where the pipeline is exposed for other reasons. The coating and/or the cathodic protection system shall be maintained to a standard such that— (i) (ii) the cathodic protection system effectively maintains protection at all coating defects; and coating disbondment is minimized. Records of the coating condition shall be kept. © Standards Australia www.standards.com.au The Standard is downloaded from www.bzfxw.com Standard Sharing 25 AS 2885.3—2001 5.5.3 Coating repairs Where a repair is made to a pipeline coating, the material used shall be compatible with the original coating and shall have been demonstrated by test, investigation or experience to be suitable for the method of installation, the service conditions and the environment. Procedures for application of the repair shall be developed so that the desired physical and chemical qualities are obtained. The application thereafter shall be in strict accordance with the procedures. Surface preparation, application and testing of the coating shall be subject to an approved quality control program. 5.6 CATHODIC PROTECTION 5.6.1 Criteria Criteria for pipeline cathodic protection shall be as specified in AS/NZS 2832.1 5.6.2 Personnel The parties responsible for the monitoring, survey, inspection, testing and maintenance of the cathodic protection system shall have the requisite experience and qualifications in cathodic protection as approved by the operating authority. NOTE: The Australasian Corrosion Association provides training for personnel in the Corrosion Prevention Industry. 5.6.3 Commissioning of cathodic protection systems Commissioning of cathodic protection systems shall be carried out in accordance with the requirements of AS/NZS 2832.1. 5.6.4 Operation, maintenance and monitoring of cathodic protection systems Operation, maintenance and monitoring of cathodic protection systems shall be carried out in accordance with the requirements of AS/NZS 2832.1 AS/NZS 2832.1 contains information in the following areas: (a) (b) (c) Criteria for cathodic protection. Measuring techniques and equipment. Operation of cathodic protection systems. Where any inspection indicates that satisfactory protection is not fully achieved on the pipeline, timely and appropriate action shall be taken to restore full protection or to instigate other measures that monitor corrosion 5.6.5 Measuring equipment Only approved measuring equipment and techniques in accordance with the requirements of AS/NZS 2832.1 shall be used. 5.6.6 Interference Interference testing shall be conducted in accordance with AS/NZS 2832.1 5.6.7 Records Records in accordance with the requirements of AS/NZS 2832.1 shall be retained for the life of the pipeline. www.standards.com.au © Standards Australia AS 2885.3—2001 26 5.7 INTERNAL SURFACES 5.7.1 Mitigation audits Where the design of the pipeline in accordance with AS 2885.1 includes the use of inhibitors and biocides as the method of corrosion mitigation, the operating authority shall confirm the suitability of the design on a regular basis. Where the mitigation method is found to be unsatisfactory, the method shall be revised to achieve the required level of corrosion control in accordance with AS 2885.1. 5.7.2 Personnel The parties responsible for the monitoring, testing and maintenance of the internal corrosion mitigation system shall have the requisite experience and qualifications as approved by the operating authority. 5.8 STATIONS 5.8.1 General The following requirements apply to stations for pumps, compressors, meters, mainline valves, pressure-regulators, odorizers, and the like. (a) (b) (c) (d) The area around stations shall be maintained in a clean and safe condition. Entries, exits, and escapes routes shall be kept free from obstruction at all times. Fences and gates shall be maintained to ensure the protection of the public and the equipment. Start up, operating, and shutdown procedures for all equipment shall be established and followed. The procedures shall include details of the measures required to ensure that all equipment, including any shutdown control or alarm circuits, functions correctly. Warning signs shall be maintained to ensure their accuracy, legibility and adequacy. When deviations from the normal operating conditions that affect the safety of the pipeline occur, corrective action shall be initiated immediately. Where determined necessary, firefighting equipment shall be kept on site and maintained in good condition. When the site is attended, sufficient personnel trained in the use of the firefighting equipment should also be in attendance. AS 3788 should be considered for pressure vessel inspections. The relevant sections of AS/NZS 3000 should be considered. (e) (f) (g) NOTES: 1 2 3 5.8.2 Pressure control and protective equipment inspection All pressure control and protective equipment, including regulators, controllers, relief valves and safety devices, shall be subjected to systematic inspection and testing in accordance with the maintenance plan to determine if they are — (a) (b) (c) (d) (e) (f) in good electrical, mechanical or hydraulic condition; set to function at the correct level; properly installed and protected from foreign material or other conditions that might prevent proper operation; installed in a manner so as to prevent unauthorized operation or alteration; operating correctly; and adequate from the standpoint of capacity and reliability of operation. Safety valves shall be maintained and tested in accordance with AS 1271. © Standards Australia www.standards.com.au The Standard is downloaded from www.bzfxw.com Standard Sharing 27 AS 2885.3—2001 5.8.3 Site security When a station is unattended, the site shall be appropriately secured. 5.8.4 Structure Structures housing equipment containing hydrocarbons, such as compressors, pumps, valve/regulator/meter pits or buildings, instrument rooms and laboratories, shall be inspected at approved intervals and shall be maintained in a safe condition. The inspection shall include the following: (a) (b) (c) (d) Testing of the atmosphere in the structure for toxic and combustible vapour. Operation of ventilating equipment. Structural integrity of pit covers. Testing of any alarms. 5.8.5 Structures housing equipment A structure that houses equipment shall be inspected at intervals determined by experience with the equipment and the risk assessment carried in accordance with the requirements of AS 2885.1. It shall be maintained in good condition. The inspection shall include the testing of the atmosphere in the structure for toxic and combustible vapour. Leaks of these types shall be located and repaired. Ventilating equipment shall be maintained in a satisfactory operating condition. Ventilation ducts shall be cleared of any obstruction. A pit cover shall be examined to determine that it does not constitute a risk to the public, and that no damage to the equipment will result from unexpected loads on the cover. 5.9 ANCILLIARY EQUIPMENT 5.9.1 General In addition to the pipeline itself, equipment ancillary to the pipeline, and in particular the items listed in Clause 5.8, shall be regularly maintained. 5.9.2 Valves Valves and actuators require regular usage and maintenance to ensure they are functioning correctly. They should be inspected at approved intervals to ensure that— (a) (b) (c) (d) (e) each valve is properly supported and that corrosion problems at support points are not occurring; valves are secured to prevent unauthorized access and usage; valve pits are structurally sound and that corrosion on fittings is not occurring; valves are not leaking; and valves and actuators are fully operable. Valves including mainline valves and the emergency hand-operated equipment of remotely controlled valves shall be tested or operated at approved intervals to confirm operability. 5.9.3 Pipe supports All pipe supports, for above-ground portions of lines, shall be inspected at approved intervals. The inspections shall establish the physical condition of each support, and verify that they are providing the required support for the pipe at that point. Where applicable, the interface between the carrier pipe and the pipe support shall be inspected for corrosion. www.standards.com.au © Standards Australia AS 2885.3—2001 28 5.9.4 Ground entry locations Severe corrosion can occur at the point where pipelines enter and leave the ground. Such points shall be inspected, in accordance with the maintenance plan, for coating deterioration and associated corrosion. NOTE: The inspection intervals are dependent on the coating type applied to the line. 5.9.5 Pig trap inspection and maintenance Maintenance of all components of pig traps (including end closure seals, bleed locks, electrical bonds, locking rings, pig signallers and fasteners) should be undertaken just prior to use, after painting or at approved intervals. In addition, temporary or removable pig traps should be inspected before use for mechanical damage (due to handling) and for evidence of corrosion. NOTE: Quick opening closures shall be operated and maintained strictly in accordance with the manufacturer’s instructions, particularly with regard to the yoke adjustments and pressurewarning devices. 5.9.6 Underwater pipelines The operating authority shall have measures in place so as to remain reasonably assured that, for underwater crossings — (a) (b) (c) the depth of cover, if the pipeline is buried, remains adequate; that scouring has not caused any part of the pipeline to be unsupported beyond allowable freespan length; and that there is no accumulation of debris or silt that could affect the stability and safety of the pipeline. In the event that the operation is not so assured, further inspections are to be undertaken. Additional inspections shall be made following severe floods, storms or earthquakes which could have affected the integrity of the crossing. Corrective action should be initiated immediately when inspection reveals an unsafe condition. 5.9.7 Tunnels, shafts and valve pits Tunnels and shafts shall be inspected at approved intervals to confirm— (a) (b) the structural integrity of the tunnel or shaft; and the absence of leaks in the pipeline. Corrective action shall be initiated immediately where the necessity for such action is revealed. A tunnel shaft or valve pit accessible by people may be a confined space. Such entry shall be controlled by the confined space entry procedure and permit in accordance with AS 2865. Valve pits shall be kept free of all matter that in any way could interfere with the operation of the valve. 5.9.8 Casings (sleeve) maintenance Schedules for pipeline maintenance should include appropriate checks on casings and attachments (e.g., checks for pipe to casing contacts or resistive bonds and gas detection of annulus vents for hydrocarbon). © Standards Australia www.standards.com.au The Standard is downloaded from www.bzfxw.com Standard Sharing