Asset Integrity Management (AIM)

Pipeline Integrity Management
The purpose of pipeline integrity management includes:
  • to ensure ability of the pipeline to perform its required function effectively and efficiently over its life cycle from conceptual to decommissioning of the pipeline by preventing failure/damage caused by degradation of its physical condition;
  • meeting all legislative and statutory requirements including HSE requirements;
  • Development and management of operation, inspection, monitoring maintenance and repair (IMMR) philosophies, strategies and plan.
Threat to pipeline integrity includes:
  • Manufacturing defects;
  • Operating condition  i.e. operating pressure and temperature;
  • Environment condition;
  • Third Party Damage;
  • Corrosion;
  • Fatigue.

The potential threats to the pipeline integrity for the operation have been considered during the engineering design phase. The concerns about HSE issues due to pipeline integrity arise when:

  • There is a need to extend pipeline service beyond its design life;
  • Uprating of pipeline operation;
  • New threats to the pipeline are being identify i.e metal loss is greater than the allocated corrosion allowance, crack, fracture, corrosion, fatigue etc.

The methods of pipeline integrity assessment:

  • Hydrotesting – to demonstrate that the pipeline is able to withstand the design pressure;
  • Direct Assessment;
  • In-line inspection – pigging (a mechanical device installed into the pipeline to check wall thickness and find damaged sections).

Risk Based Inspection (RBI)
Risk = Probability of failure x Consequences of failure.
Risk Based Inspection (RBI) is related to risk based asset integrity management. RBI is used to assess the risk levels to develop a prioritised inspection plan, as same flaw at different location of the pipeline will have different consequences. The purpose of RBI is to determine what inspection to perform and how often to inspect

Common elements of RBI:
  • Asset identification;
  • Segmentation;
  • Hazard identification;
  • Probability of failure;
  • Consequence of failure;
  • Risk assessment.

Codes and Standards:
  • DNV-RP-F116;
  • API 1160;
  • ASME B31.8S;
  • API 580/581(for other asset but not applicable for pipeline)

Fitness for Purpose (FFP)
The Fitness for Purpose (FFP) is also commonly known as Fitness for Service (FFS). It is a key part of Asset Integrity Management. The purpose for fitness for purpose assessment is to demonstrate the structural integrity of the pipeline. The FFP assessment is carried out for corroded or damaged pipeline to assess the potential for lifetime extension of the pipeline.

Codes and Standards:
  • Corrosion assessment – DNV-RP-F101, ASME B31G and RSTRENG;
  • Crack assessment – API RP 579 and BS 7910.


The types of flanges can be divided into:
1.    Codes and Standards flange:

·         ASME flange;
o   ASME weld neck flange;
o   ASME Swivel ring flange.
·         API flange.
2.    Compact flange:

·         Misalignment flange (Taper-Lok);
·         Norsok L-005 SPO.

S-N Fatigue Assessment

The S-N high cycle fatigue assessment is conducted to determine the pipeline fatigue life under the high cyclic temperature and pressure fluctuations. A fatigue assessment of response that is associated with number of cycles more than 10000 is denoted high cycle fatigue, where the assessment is performed based on calculation of elastic stresses.

The S-N fatigue assessment is based on Palmgren-Miner rule, which does not take into account of mean stress, frequency and loading sequence. The fatigue assessment is carried out for the following locations:
•    Girth weld cap;
•    Girth weld root;
•    Longitudinal seam weld (except seamless pipe).
Accounting for:
•    axial stress;
•    hoop stress;
•    Bending stress.
•    Stress concentration factor (SCF) at the girth weld including the effect of misalignment;
•    Type of S-N curve i.e. D, E, F, F1 or F3;
•    Condition of weld i.e. seawater cathodic protection (CP), in air or free corrosion.

The longitudinal stress range at each single location along the pipeline route can be obtained from Finite element analysis (FEA) model or calculated in accordance with DNV-OS-F101 Section 4.1.1 conservatively assuming the pipeline is fully restrained.

1.    DNVGL-RP-0005:2014-06 (supercedes DNV-RP-C203);
2.    DNV-OS-F101

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