MAINTENANCE/INSPECTION &
Objective •
Provi Provide de requi requireme rements nts for the the safe safe and and reliab reliable le opera operatio tion n of pipeline systems for the whole service life
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Requir Requiremen ements ts are given given for operat operation ion,, inspecti inspection, on, modifi modificat cation ionss and repair
Basic Requ Requirements irements Detailed procedures for operation, inspection, and repairs shall be establish. This procedures provide information about : • Orga Organi nisa sati tion on and and man manag agem emen ent; t; • Star Start-u t-up p and and shut shut-d -dow own n proc procedu edure res; s; • Oper Operat atio iona nall limi limita tati tion on;; • Cleanin Cleaning g and other other mainten maintenanc ance, e, e.g pigging pigging;; • Corros Corrosion ion contr control, ol, incl includin uding g inspec inspection tion and and monito monitorin ring; g; • Inspection; • Emer Emerge genc ncy y proc proced edur ures es;; • Repor eporti ting ng proc proced edur ures es..
In--Service In -Service file • An in-servic in-service e file of historic historical al data data shall shall be established established and maintained for the whole service life • The in-servic in-service e file file shall shall contain contain information information regarding regarding : - resu esu s an conc us on ro rom
e n-ser -serv v ce nspec ons; ns;
- accidental accidental events events and damages to the pipeline systems; systems; - repair and and modifications modifications;; and - operational data affecting corrosion and other deterioration • The in-service in-service file, together together with the design, fabrication, fabrication, installation installation DFI resume resume shall shall be the basis basis for future future ins ection ection lannin lannin
Operation The following parameters should be controlled or monitored to ensure that critical fluid parameters are kept within the specified design limits : • pressure and temperature along the pipeline; • • fluid composistion, flow rate, density and viscosity
All safety equipment in the pipeline system shall be tested and inspected at agreed intervals, including : • pressure control and over-pressure protection devices, • emergency shut down systems, and • automatic shut down valves
Inspection and monitoring philosophy • An inspection and monitoring philosophy shall be established, and this shall form the basis for the detailed inspection and monitoring program • The philosophy shall be evaluated every 5 to 10 years • Inspections and monitoring shall be carried out to ensure safe and reliable operation of the pipeline system • All inspection and monitoring requirements identified during the design phase as affecting safety and reliability during operation shall be covered in the inspection and monitoring program
Special inspection • A special investigation shall be performed in case of any event which impairs the safety, reliability, strength or stability of the pipeline system. This investigation may initiate further inspections • periodic inspection, a proper evaluation of the damage shall be performed, which may include additional inspections
PIPELINE CONFIGURATION SURVEY Periodic Survey • The Start-up inspections shall be completed within one year (1 year) from start of production • In case of significant increase in temperature or pressure after this first inspection, the need of additional inspections should be considered • The following should be considered for a long term inspection programme reflecting the overall safety objective for the pipeline : -
operation conditions of the pipeline,
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consequences of failure
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likelihood of failure
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inspection methods, and
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design and function of the pipeline
PIPELINE CONFIGURATION SURVEY Periodic Survey (cont’d) • The long term inspection program shall include the entire pipeline system. The following items, at minimum, should be considered : - pipeline, - risers, - Valves, - Tee and Y connections, - mechanical connectors, - flanges, - anchors, - clamp - protecting structures, - anodes, - coating.
PIPELINE CONFIGURATION SURVEY Periodic Survey (cont’d) • Inspection shall be carried out to ensure that the design requirements remain fulfilled and that no damage has occurred. The inspection program s ou a ress, suc as : -
Exposure and burial depth of buried or covered lines
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Free spans, including mapping of length, height, and support condition
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Identification of areas where upheaval buckling or excessive lateral buckling has taken place
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Sand wave movements affecting the pipeline integrity
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Mechanical damage to pipe, coating and anodes
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Leakage
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Etc.
PIPELINE CONFIGURATION SURVEY Periodic Survey (cont’d) • The risers shall be part of the long-term inspection programme for the pipeline system. Special attention shall be given to the following elements for riser inspections : -
Riser displacement due to pipeline expansion or foundation settlement
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Coating damage
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Technique for corrosion control of any risers in closed conduit of J-tubes
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Extent of marine growth
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Extent of any previous damage due to corrosion
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Integrity and functionality of riser supports and guides
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Integrity and functionality of protecting structure
PIPELINE CONFIGURATION SURVEY Periodic Survey (cont’d) • The frequency of future external inspections shall be determined based upon an assesment of : -
Degradation mechanisms and failure modes,
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Likelihood and consequences of failure,
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Results from previous inspections,
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Changes in the operational parameters,
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Repair and modifications, and
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Subsequent pipelay operation in the vicinity
PIPELINE CONFIGURATION SURVEY Periodic Survey (cont’d) • Critical sections of the pipeline system vulnerable to damage or subject to major changes in the seabed conditions i.e support and/or burial of the pipeline, shall be inspected at short intervals, normally on an annual basis • The remaining sections should also be inspected, ensuring a full coverage of the entire pipeline system within a 5 yo 10 years period
INSPECTION AND MONITORING OF EXTERNAL CORROSION General • In the splash zone and in the atmospheric zone, damaged and/or disbonded coatings can cause severe corrosion damage. Risers • In the submerged zone, coating malfunctions are not critical unless they are combined with deficiency in the cathodic protection system • For risers contained in J-tubes filled with non-corrosive fluid inspection of external corrosion may not be required if adequate properties of the fluid is verified by periodic testing corrosion of risers and pipelines in all three zones including risers conintained in J-tubes, if required
Severe corrosion damage In the splash zone
Damage due to corrosion In atmospheric zone
INSPECTION AND MONITORING OF EXTERNAL CORROSION Risers in the Splash zone and the Atmospheric zone • In the splash atmospheric zone, visual examination of the coating shall be performed in order to assess the needs for preventive • Besides visual indications of direct damage to the coating, effects such as rust discoloration and bulging or cracking of the coating are indicative of under-rusting • Coating systems which prevent close inspection of under-coating corrosion shall require special consideration shall be determined based on : - the fluid category, - the line pipe material, - coating properties and - any corrosion allowance
INSPECTION AND MONITORING OF EXTERNAL CORROSION Pipeline and Risers in the Submerged Zone • To a large extent, inspection of external corrosion protection of pipelines and risers with sacrificial anodes can be limited to • Excessive anode consumption is indicative of coating deficiencies, except close to platforms, templates and other structures where curent drain may lead to premature consumption of adjacent pipe anode • Potential measurements on anodes, and at any coating damage exposing bare pipe metal, may be carried out to verify adequate protection • For pipelines with impressed current cathodic protection systems, measurements of protection potential shall, at minimum, be carried out at locations closest to, and most remote from, the anode(s) • A survey of the external corrosion protection system, should be carried out within one year of installation
INSPECTION AND MONITORING OF INTERNAL CORROSION General • Inspection of internal corrosion is carried out in order to confirm the integrity of the pipeline system, primarily by means of in situ wall • The objective of monitoring internal corrosion : -
to confirm that the fluid remains non-corrosive or,
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to assess the efficiency of any corrosion preventive measures, and,
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to identify requirements for inspection of corrosion
(CRA) do not normally require inspection and monitoring of internal corrosion
Pipeline internal inspection
INSPECTION AND MONITORING OF INTERNAL CORROSION Corrosion Inspection • Internal corrosion inspection shall be carried out with a carrier tool (“inspection pig”) capable of inspecting the internal surface of the , thereof • The technique for detection of internal corrosion (e.g magnetif flux leakage or ultrasonic examination) shall be selected based on considerations : -
Linepipe material
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Diameter and wall thickness
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Expected form of damage
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requirements to detection limits and defect sizing capability
Pipeline Pig
INSPECTION AND MONITORING OF INTERNAL CORROSION Corrosion Inspection (cont’d) • The frequency of internal inspections shall be determined based on factors such as : -
r
ca
y o p pe ne
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Potential corrosivity of fluid
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Detection limits and accuracy of inspection system
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Results from previous surveys and monitoring
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Changes in pipeline operational parameters, etc.
INSPECTION AND MONITORING OF INTERNAL CORROSION Corrosion Monitoring • The following major principles of corrosion monitoring may be applied : -
Corrosion probes
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In-situ wall thickness measurements
• Techniques and equipment for corrosion monitoring shall be selected based upon : -
Monitoring objectives, including parameters for accuracy and sensitivity
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Fluid corrosivity and the corrosion preventive measures to be applied
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Potential corrosion mechanisms
DEFECTS AND REPAIR General • Repair and modification shall not impair the safety level of the pipeline system below the specified safety level • All repairs shall be carried out by qualified personnel in accordance with agreed specifications and procedures, and up to the standard defined for the pipeline • All repairs shall be tested and inspected by experienced and qualified personnel in accordance with agreed procedures • Pipeline systems with defects may be operated temporarily under defect has been removed or repair has been carried out
DEFECTS AND REPAIR General (cont’d) • When a defect is observed, a evaluation of the defect shall be performed and shall, as a minimum, include : -
Determined details of the defect
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Mechanisms causing the defect
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Accuracy and uncertainties in the inspection results
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Option for further operational conditions of the pipeline system
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Repair method
• Depending upon the condition of the damage, a temporary repair may be accepted until the permanent repair can be carried out • If temporary repair is carried out, it shall be documented that the pipeline integrity and safety level is maintained either by the temporary repair itself and/or in combination with other precautions
Selection of most effective Repair / Rehabilitation methods ) Welded sleeve •
Mechanical sleeve
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Hot tap fitting
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Hot tap and STOPPLE® procedure with bypass
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DEFECTS AND REPAIR Global buckling • Upheaval buckling or lateral deflection resulting in plastic bending strains, the pipeline may continue operating until the need of repair , kept within a range that prevent s the accumulation of low-cycle high strain fatigue failure in the buckled section
Grooves, gouges, cracks and notches • Sharp defects like grooves, gouges, and notches should preferably be removed by grinding or other agreed repair methods. •
or groun e ec s w ere a s arp e ges are con rme as remove , that defect can be regarded as a smooth metal loss defect
DEFECTS AND REPAIR Metal Loss Defects • Metal loss defects caused by e.g corrosion, erosion, or grind repair shall be checked for capacity.
Dents • A dent is defined as a depression which produces a gross disturbance in the curvature of the pipe wall, and which results in a diameter variations of more than 2% of the nominal diameter • A dent affecting the longitudinal or circumferential weld can result in cracks, and removal of the damaged portion of the pipe should be cons ere • The damaged part can be cut out as a cylinder, or repaired by installing a full encirclement welded split sleeve which is designed to take the full internal operating pressure
DEFECTS AND REPAIR Leaks • The most suitable method for repairing a leak in the pipe depends upon e.g : - Pipe dimensions - Location of leak - Load conditions - Pressure - temperature • The following repair methods may be used : -
The damaged portion is cut out of the pipe as a cylinder and a new pipe spool is installed either by welding or by an mechanical connector
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Clamps are installed, and tightness is obtained by either welding, filler material, friction or other qualified mechanical means
Leak on pipeline
DEFECTS AND REPAIR Leaks (cont’d) • Leaking flanges and couplings may be sealed by : -
Installing a seal clamp covering the leaking flange or coupling,
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Increasing the bolt pre-load, or
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Replacing gaskets and seals
• Prior to increasing the pre-load in bolts, it shall be documented by calculation that no over-stressing occurs in bolts, flange or gasket/seal , . gasket, new bolts shall be used for the flange connection • All repair clamps, sleeves, pipe spools, and mechanical connectors shall be qualified prior to installation and leak tested after installation
DEFECTS AND REPAIR Repair by Welding • A welding procedures specification shall contain following information, such as : , - Diameter and wall thickness, - Groove preparationg and design, including tolerances - Welding process, number and location of welders - Etc. • For underwater welding the welding procedure specification shall contain, in addition to the procedure above, such as : - Water depth (max/min) - Pressure inside the chamber - Gas composition inside the chamber - Humidity, maximum level - Etc.
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Underwater welding
DEFECTS AND REPAIR Repair by Welding (cont’d) • Repair welding may, in special cases, be carried out on pipelines while operating, depending on : -
pe ma er a ,
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Pipe wall thickness,
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Product tipe,
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Pressure and Temperature
• It shall be documented that safety for carrying out the repair is acceptable, and a safety procedure shall be established • All repair welds shall be subject to visual and non-destructive testing. Following the repair, pressure testing may be required for the repaired section.
Pipeline Welding Repair
REMAINING LIFE ASSESSMENT 9
A remaining life for the component should be determined once it has been established that the component containing flaw is acceptable at the current time,
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The remaining life is used to establish appropriate inspection interval and/or in-service monitoring plan, or the need for remediation
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The remaining life is not intended to provide a precise estimate of the actual time to failure.
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The remaining life can be estimated based on the quality of , assumptions to provide an adequate safety factor for operation until the next scheduled inspection
REMAINING LIFE ASSESSMENT Remaining life estimates will fall into one of the following three general categories : 1. The remaining life can be calculated with reasonable certainty Example : general uniform corrosion. The remaining life is the future corrosion allowance divided by the assumed corrosion rate from previous thickness data, corrosion design curves, or experience in similar services. 2. The remaining life cannot be calculated with reasonable certainty Example : stress corrosion cracking mechanism where there is no reliable crack growth rate data available or hydrogen blistering where a future damage rate cannot be estimated 3. There is little or no remaining life In this case remediation, such as repair of the damaged component, application of a lining or coating to isolate the environment, and/or frequent monitoring is necessary for future operation
REMAINING LIFE ASSESSMENT
Type of corrosion found in pipeline
REMAINING LIFE ASSESSMENT
Estimation of remaining life of pipe network using software
REQUALIFICATION General 9
Re-qualification is a re-assessment of the design under chan ed desi n condition.
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Re-qualification may be triggered by a changed in the original design basis, by not fulfilling, or by mistakes or shortcomings having been discovered during normal or abnormal operation.
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Possible causes may be: 1) preference to use this standard, e.g. due to requirement or g er u a on or ex s ng p pe nes pra ng ; 2) changed of the premises; • environmental loads, • Deformation, • Scour.
REQUALIFICATION General (cont’d) 3) Changed of operational parameter; • pressure or temperature, • Corrosivity of medium. 4) deteroration mechanism having exceeded the original assumption; • corrosion velocity, both internal and external ; • dynamic responses, contributing to fatigue, which may be caused by lacking supports etc 5) Extended design life; • dent, • damage to pipeline protection, • weld defect, • corrosion related defect. 7) damage anode.
REQUALIFICATION General (cont’d) 9
Within the original design life, and without essential changes in the manner of em lo ment re air etc. the standard under which the pipeline was built shall apply when considering incidents, minor modifications or rectification of design parameters exceeded during operation
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The same safety level shall apply for lifetime extension of an existing pipeline as would apply for the design of a new pipeline
REQUALIFICATION Design Criteria 9
A target safety level below shall apply for a re-qualification assesment Limit state
Probability Bases
SLS
Annual per Pipeline1)
ULS
Annual per Pipeline1)
FLS ALS
Annual per Pipeline2) Annual per Pipeline2)
1) 2)
3)
Safety Classes Low
Normal
High
10-2
10-3
10-3
10-3
10-4
10-5
Or the time period of the temporary phase The failure probability will effectively be governed by the last year in operation or prior to inspection depending on the adopted inspection philosophy Refers to the overall allowable probability of severe consequences
REQUALIFICATION Design Criteria (cont’d) System pressure test System pressure test may be required when •
The original mill pressure test or system pressure test does not satisfy requirement according to this standard at the new design pressure
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A significant part of the pipeline has not been system pressure tested e.g. new pipeline section
All Relevant deterioration mechanism shall be evaluated. Typical deterioration mechanism: -
corrosion
- accdental loads
- fatigue
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erosion
- development of free spans
- settlement
REQUALIFICATION Design Criteria (cont’d) 9
Sufficient reliability or safety measure shall be applied to account for the accuracy and uncertainities in the inspection results
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Accumulated damage experienced prior to the re-qualification shall be included in the evaluation
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Operation experience, e.g. change of operational condition, inspection records and modifications, shall be considered in a -
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