It is an unfortunate reality that, due to geographical location, not all operators have access to the same in-line inspection (ILI) vendors. For example, operators in South America may only have access to 50% of the crack-detection ILI service providers, which is already a short list. This means that operators have a reduced supply and the ‘best’ tool for the job may not be available.
Ref: GONCALVES et al, “A FRAMEWORK TO DEVELOP EFFECTIVE CRACK MANAGEMENT STRAREGIES FOR GAS TRANSMISSION PIPELINES – IBP2064_17, Rio Pipeline 2017.
Serving all markets and achieving global reach is a tough ask for an ILI vendor. When considering a new market, ILI vendors would typically review:
- Market size – is there a demand for my tool? How many pipelines could I inspect per year?
- Competition – who will I be competing with? Can we compete commercially?
- Accessibility – can we move through customs efficiently? Are the pipelines accessible or do we need to hire helicopters to navigate through jungles and access certain locations?
- Geopolitics – A real talking point these days.
- Commercials – considering competition, accessibility, and market size. Will we make any money?
- Business risk - reputation, safety etc.
When presented with an ILI menu (extensive or reduced), it is important to make an informed selection. Frontline Integrity recommend breaking the process up into 5 simple steps to support any tool selection:
Step 1: Identify the Target Pipeline Threat
Define the target integrity threat(s) – what type of cracking is suspected – axial, circumferential, weld, pipe body, associated with corrosion, why? Are there certain locations along your pipelines where you feel cracking is most credible due to the pipeline materials, the environment or the stress state?
- The answers can typically come from a desk-based threat assessment, a field dig report or a laboratory analysis of a cut out.
- The decision may be taken not to go hunting with ILI crack detection technology at all if the threat can be adequately managed through other means, or enough evidence is available to demonstrate that the threat is negligible.
Step 2: Preparation Of Information
Planning an ILI should be no different from any significant personal purchase, from a television to a car; do your homework upfront to understand the market and review consumer feedback.
Having a clear picture of the vendors and the latest technology is key:
- Is EMAT (which requires no liquid medium) the only option for gas lines or can you consider a standard ultrasonic inspection?
- What are the key advantages and disadvantages of the options available from an operational, data quality, performance or cost perspective?
- What will be the likely inspection conditions in the pipeline, noting the sensitivity of crack detection tool performance to these parameters – pressure, temperature, debris type/quantity flow velocity? What are my boundaries for modifying these (e.g. pigging offline) to improve the tool performance if the vendor requires (e.g. reducing flow)?
- Can I define the minimum sub-critical cracks size that the tool must find in order to give a safe margin against failure? This will vary along the pipeline depending on a number of factors: the range of material properties (especially fracture toughness), estimated crack growth rates, the pipeline stress state local to the cracking and other ‘risk’ factors, such as consequence of failure.
Frontline Integrity can support at this stage to prepare for vendor engagement by reviewing existing pipeline and threat-knowledge, identifying gaps and managing the process of closing the gaps. It is also beneficial to obtain feedback from other customers who have used the technology (both good and bad experiences). Considering our extensive experience working in the crack detection market with operators, and detailed knowledge of tool performance sensitivities, Frontline Integrity have been the link between operators and have helped facilitate technical exchanges where valuable feedback was provided.
Step 3: Engage with vendors
Once you have completed your market research, it’s time to engage with the vendors. Standard ILI vendor discussions surrounding the mechanical piggability of the pipeline, logistics and campaign timescales should be followed up with some crack-detection specific considerations.
Outline your integrity objective – this is the threat you are looking for and this is where you expect to find it. Let them present their solutions for you to review and challenge these if you think other combinations may be more suitable.
It’s always good to discuss tool availability and reporting delivery times upfront, as this could be a deal breaker if you need an ILI with a quick turnaround time. However, if you have identified the ‘best’ tool for the job, it might be worth waiting for.
Remembering that ILI crack detection technology performance is highly sensitive to the pipeline construction; the inspection environment and the target cracking morphology, providing confidence in the likely tool performance should be your priority challenge to the vendor:
- How has the tool performance specification been derived specifically for the proposed tool (diameter) being used? Can the vendor supply evidence of the validation process and/or certification? This could also be in the form of a knowledge share of a previous analogous inspection or pull-test (the same tool targeting the same target threat morphology).
- What are the limitations within the specification regarding detection, identification and sizing – specifically against the target threat? Some complex cracking morphologies (step-wise cracking for example) may only be detectable with significant sizing uncertainties. Other cracking threats may also occur co-incident with other anomaly types such as pitting with steep edges (e.g. Stress Corrosion Cracking). This may significantly impact on the ability to differentiate cracks from corrosion and potentially lead to many misclassified features.
- Combined with the above, is the specification suitable for the likely inspection conditions in my pipeline, i.e. wall thickness / diameter / pressure / flow velocity etc.? What modifications can be made to the tool and/or the pipeline to optimize the inspection tool performance (e.g. speed control units)?
- Given the above, does more work need to be done prior to the inspection to gain confidence in tool performance (e.g. lab-based sensor testing, pull/pump testing etc.)?
- Where, or under which operational circumstances, might the specification not be valid on your system (e.g. heavy-wall crossings? Is your calculated critical defect size along the pipeline compatible with the specification? From a risk-management perspective, you don’t want to limit your capability to only detecting cracks close to or at their failure dimensions.
- Do you understand what the vendor’s reporting terminology means: Crack-like, linear-anomaly, notch-like etc? What does it tell us regarding the data-analyst’s interpretation of signal characteristic?
- Have I adequately defined any pipeline-specific reporting criteria over and above the vendor’s standard criteria? Firstly any ‘immediate’ call criteria along the pipeline driven by critical crack dimensions. Secondly, any other susceptibility-related information that may be visible in the ILI data that, if reported, could help us to prioritize features that are more likely to be integrity threats – e.g. crack-like anomalies associated with low-level geometrical deformations, field bends, association with external metal loss.
- Can the vendor provide evidence of successful runs where the system correctly detected, identified and sized similar target morphologies in analogous pipelines?
- How do you propose to validate tool performance against the target threat? How will the vendor use this information and any other information provided to improve the output of this inspection or future inspection campaigns?
- Which other ILI technologies may be able to complement the crack detection technology in locating the threat? This is especially relevant in areas where its performance may be sub-optimal, or the cracking is known to be co-incident with other anomaly types. For example, if some cracking may be associated with geometric deformations (a common challenge for crack-detection ILI due to sensor lift-off), a geometry inspection may provide valuable information regarding threat ‘hot-spots’. This isn’t ideal but it’s better than having no information at all.
- Are the results from any previous ILI (crack detection or otherwise) and field verification results being appropriately considered when evaluating the new crack dataset? This can rapidly accelerate the process of drawing out the true integrity threats from the overall ‘crack-like’ population.
Relating threat knowledge to ILI system performance before selecting an ILI tool is also central to the verification process contained in API Standard 1163 which is associated with ensuring an ILI system has been selected, prepared and run in a manner that is capable of achieving the stated vendor performance specification.
Once you have all of the information above, sit down with your team (or an independent advisor) and compile a vendor comparison report.
Step 4: Analyze the big picture
Leaning on your comparison report and market knowledge, identify any risks (technical / operational and financial) and feed them into your tender process to make an informed decision.
No integrity response to a cracking threat should be solely reliant on ILI due to its inherent uncertainties and a combination of complementary techniques is always recommended to appraise the threat criticality. However, if there are significant red flags surrounding tool performance, consider drafting an alternative strategy aside from ILI.
Alternative strategies could be in the form of:
- Refining your current threat analysis through the collection of additional data.
- Validating the threat analysis through targeted field investigations in susceptible locations to review risk (Direct Assessment).
- Sectional hydrotesting.
- The implementation of risk reduction measures, e.g., operational changes which could extend remaining life – e.g. pressure reduction, or reduction of pressure cycles where a fatigue cracking threat is present.
- The implementation of permanent mitigation, e.g., pipe replacement.
Step 5: If you are happy to proceed with a crack detection ILI, select your ILI vendor and start planning your pigging!
Note: think about reaching out for that independent support to help you with the next steps. Data quality, data evaluation, reporting and tool validation can be a minefield…
Summary of where Frontline regularly adds value to pipeline operators:
How can we help Operators and what value do the Frontline Integrity team add?
Frontline Integrity Support Options
Added Value
Understanding your threat
Deliverable: Technical Report
An independent review of the cracking threat susceptibility and the overall risk level. This can support justification with management that the threat needs to be actively managed.
Market Evaluation of Technology
Deliverable: Market Summary Report, detailed technical summary report
We work across the globe and have a good insight regarding the technology options, performance capabilities and limitations as well as access to multiple operators who can provide first hand feedback.
Detailed ILI system technology appraisal (post selection)
This can be quite time consuming and technical. We have extensive experience in this area (many of our team have worked for ILI service providers before in both design, testing and integrity management roles) and can assist with the upfront appraisal of what a crack detection ILI tool is likely to offer in your pipeline, where performance issues are likely to occur, and where additional supporting integrity management techniques (including other ILI technologies) will significantly support risk management activities.
Production of Technical Tender Specifications
Specification of tool performance and data evaluation requirements against the target threat to ensure the proposed vendor solutions will actually add value to the pipeline integrity management process.
Tender support
Deliverable: Vendor comparison Report
It is important to document commercial decisions and their associated justification. Drafting a vendor comparison report will enable the company to demonstrate a fair process whilst justifying that the best tool has been selected for the job.
Alternative Strategic Planning
Deliverable: Summary report on options
If ILI performance is expected to be severely limited with respect to the target cracking morphology, alternative options need to be identified. We have experience planning and executing bespoke risk-based integrity management plans to support operators in this scenario so they can feed the data into a cost benefit analysis.
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