Quick Answer
A pipeline integrity assessment is a step-by-step method that turns inspection data and operating history into clear decisions:
- Repair/Mitigation → when damage or wall thinning is too severe.
- Re-rate → when the pipeline can still run safely at lower pressure.
- Continue Service (with monitoring) → when fitness-for-service checks confirm it’s safe.
This process reduces guesswork, makes decisions transparent, and leaves a clear record for audits.
Introduction — What This Guide Covers
This guide explains how to assess the condition of a pipeline in a simple, structured way.
It helps you:
- Understand what an integrity assessment really means.
- Know when to repair, re-rate, or continue operation.
- Learn what data to collect and how to use it.
- Follow a clear workflow that anyone in operations, maintenance, or management can understand.
What “Integrity Assessment” Really Means
In simple words, a pipeline integrity assessment is about checking if a pipeline is still safe to use.
It involves:
- Looking at inspection data (thickness, damage, anomalies).
- Reviewing operating history (pressures, temperatures, duty changes).
- Deciding if the pipeline needs repair, a pressure change, or if it can keep running safely.
- Documenting decisions so they can be explained and audited later.
When Do You Need an Assessment?
You typically perform an assessment when:
- New inspection results show thinning or defects.
- Operating limits (pressure/temperature) have been exceeded.
- Duty or product changes (e.g., different fluid).
- After incidents, near misses, or regulatory checks.
- As part of routine life-extension studies.
If the risk or uncertainty is high, a more detailed study is needed.
What Data Do You Need?
An integrity assessment is only as good as the data you collect. Before making any decision, make sure you have:
1. Inspection & Condition Data
- Visual checks → coating, supports, leaks.
- Wall thickness → ultrasonic (UT), mapping, or in-line inspection (ILI).
- Damage detection → screening for cracks, dents, or corrosion.
- Geometry & supports → alignment, vibration, soil cover (if buried).
- Anomaly register → a simple log with ID, location, size, and photos.
💡 Tip: Use the same measurement points (CML/TML) each time to spot real trends.
2. Operating History
- Pressures and temperatures (normal and upset conditions).
- Flow regime (composition, water/sand content, corrosive gases like CO₂/H₂S).
- Events like startups, shutdowns, pigging, or inhibitor outages.
- Any safety limit (IOW) excursions.
💡 Tip: Always connect inspection results with what was happening in the pipeline at that time.
3. Documentation & Records
- Original drawings and material specs.
- Previous inspection and repair history.
- Certificates, calibration reports, and approvals.
- Reasons behind earlier inspection intervals.
Validating Data & Spotting Trends
Not all data is reliable. Before using it:
- Check coverage (enough points, right locations).
- Confirm method and operator quality.
- Remove obvious outliers, but explain why.
- Align data with operating history (don’t compare apples to oranges).
Once validated, look for trends:
- Is the wall thickness reducing steadily?
- Is the corrosion general (everywhere) or localized (pitting, cracks)?
- Do multiple points show the same pattern?
💡 Tip: Use at least three data points over time for a reliable trend.
Deciding What to Do
After data is validated and trends are clear, decisions fall into three main paths:
Repair/Mitigation
- When the wall thickness is too low.
- When cracks or severe local damage exist.
- When the location is high-risk (e.g., near people or critical assets).
- FFS determines if immediate repair is mandatory or if temporary mitigation is acceptable.
Actions: sleeve, clamp, spool replacement, or temporary mitigation.
Re-rate
- When the pipe is safe at a lower pressure or temperature.
- Useful if the remaining life is acceptable under reduced duty.
- FFS can also lead to a safe re-rating decision instead of full repair.
Actions: adjust operating limits, update documents, and add alarms.
Continue Service (with monitoring)
- When the pipeline is still safe, but needs closer monitoring.
- Always confirmed through a Fitness-for-Service (FFS) study.
Actions: set shorter inspection intervals, define a monitoring plan.
Setting Inspection Intervals
How often should you check again? It depends on:
- Corrosion rate (CR) → how fast the wall is thinning.
- Remaining life (RL) → years left before minimum safe thickness.
- Risk level (PoF/CoF) → higher risk = shorter intervals.
- Operating conditions → stable vs. upset history.
💡 Tip: Fast corrosion or high-consequence areas need shorter inspection cycles.
Governance & Documentation
To keep decisions traceable:
- Defect register → keep it updated with IDs, photos, thickness, and actions.
- Approvals → engineers, operations, and management should review decisions.
- Official records (MDR/CMMS) → store updated drawings, reports, and repair documents.
- Change management → log any new procedures, setpoints, or training.
Deliverables (What to Include in the Report)
Every integrity assessment should have:
- A short executive summary (objectives, scope, key decisions).
- Main findings (thickness, corrosion rate, remaining life).
- Decision path (repair, re-rate, or continue service).
- Next inspection plan with timing and responsibilities.
- Supporting documents (photos, registers, assumptions, standards referenced).
Common Pitfalls to Avoid
- Using inspection data without checking quality.
- Relying only on two measurements to calculate the corrosion rate.
- Treating average thickness as safe instead of checking the weakest spot.
- Ignoring localized thinning or cracks.
- Re-using last year’s interval without new calculations.
- Missing proper Fitness-for-Service (FFS) when uncertainty is high.
FAQ — Short Answers
Q: What is a pipeline integrity assessment?
A structured process that converts inspection and operating data into a safe decision: repair, re-rate, or continue service.
Q: What data do I need?
Inspection findings, operating history, and documentation (drawings, repair records).
Q: How do you calculate corrosion rate and remaining life?
CR = (thickness drop) ÷ (time)
RL = (margin left) ÷ CR
Q: When do you re-rate instead of repair?
When the pipe is still code-compliant at lower limits and remaining life is acceptable.
Q: When is Fitness-for-Service (FFS) needed?
When localized thinning, cracks, or high uncertainty exist.
Q: How do you set inspection intervals?
Based on corrosion rate, remaining life, risk level, and RBI methodology.
Pipeline Integrity Assessment: Conclusion & Next Steps
Recap
- Use validated inspection and operating data.
- Apply a clear workflow: Repair, Re-rate, or Justify Continued Service (JCS).
- Keep everything audit-ready with traceable assumptions and approvals.
Next Steps
- Focus first on high-risk pipeline segments.
- Close data gaps before trending or re-rating.
- Maintain a defect register and inspection interval rationale.
- Escalate to FFS (API 579) or RBI (API 580/581) when uncertainty or high risk exists.
- Engage NWE for Structural Integrity Assessment aligned with API/ASME.
