IRI-Corrology®: Crude Corrosivity User Manual
A framework for screening failure likelihood, interpreting findings, and determining remediation paths for assets subject to crude-corrosivity mechanisms.
| Manual Focus | Description |
|---|---|
| Primary objective | Support integrity prioritization and inspection planning in hot crude service |
| Decision style | Comparative risk signal with engineering judgment |
| Recommended workflow | Baseline -> driver diagnosis -> pathway evaluation -> documented action |
Use this page as the standard runbook during live analysis.
Designed for fast, reliable execution in operational workflows. Keep one baseline pinned, test one lever at a time, and document every decision with residual uncertainty.
Quick Navigation
Purpose
This manual explains how to use IRI-Corrology®: Crude Corrosivity for practical integrity screening and how to interpret outputs with confidence.
It is written for day-to-day engineering use: run setup, result interpretation, remediation-path usage, and reporting.
At a Glance
- Primary purpose: Prioritize crude-corrosivity risk and support inspection planning decisions in naphthenic-acid and sulfidation-sensitive service.
- Output: A comparative risk indicator that supports engineering judgment. It is not a standalone fitness-for-service (FFS) assessment.
- Recommended workflow: Establish a baseline case, then evaluate the impact of controlled what-if scenarios to understand how potential changes influence the predicted risk.
Quick Start
Run Flow
- Open all expandable input cards in IRI-Corrology®: Crude Corrosivity.
- Choose Predictive or Inspection mode.
- Enter required inputs.
- Click Analyze to run the assessment.
- Review the Susceptibility Score, Corrosion Rate Context, and Susceptibility Drivers.
- Pin the baseline case before evaluating multiple what-if scenarios.
- Export a PDF report. NOTE: The report includes the last two cases: Baseline/Prior and Active/Current.
Recommended Operating Practice
- Define a single objective for each analysis set.
- Change only one variable or variable group in each what-if scenario.
- Record one clear engineering conclusion for each analysis set.
Critical Mode Warning
Predictive and Inspection modes are not directly comparable without context translation.
When switching modes, treat the next run as a new analytical context and re-establish baseline before drawing conclusions.
Before You Run
Complete the following checks to ensure reliable results and meaningful comparisons.
✔ Confirm that the intended analysis mode (Predictive or Inspection) is selected.
✔ Confirm that crude chemistry inputs match the intended operating window.
✔ Verify whether the corrosion rate is measured or model-derived, and interpret the results accordingly.
✔ Verify that PTA SCC and morphology settings reflect available inspection evidence.
✔ Ensure that all units, operating ranges, and process data are consistent with site records.
Interpretation Guidance
Treat the Susceptibility Score as a decision-support indicator rather than a standalone acceptance criterion.
Use the Susceptibility Drivers to determine whether improvement is best achieved through chemistry/process control, improved inspection confidence, inspection quality, or a combination of these elements.
Reading the Results
- Review the overall trend before focusing on the absolute score.
- Identify the dominant driver family.
- Determine whether the dominant contribution is operational (Severity) or related to data quality (Uncertainty or Detection).
- Select the most appropriate response:
- operational changes,
- inspection improvements, or
- a combination of both approaches.
Decision Ladder
- Is the risk increasing compared with the baseline?
- Which driver family contributes most to the result?
- Is the available evidence sufficient to support a decision?
- Select the appropriate response:
- operational adjustment,
- improved inspection or data quality,
- or a combined mitigation strategy.
Decision Flowchart
Decision intent: Move from diagnostic output to one explicit action path, then verify its impact against the baseline.
Short Interpretation Examples
Example A: Severity Dominant
Pattern: severity drivers dominate and corrosion map highlights sulfur, TAN, temperature, or WSS effects.
Interpretation: the operating envelope is likely the primary risk lever.
Action focus: chemistry/process-window control, then re-check score shift.
Example B: Uncertainty Dominant
Pattern: uncertainty and detection contributions exceed severity.
Interpretation: confidence in the assessment is limited; the risk may be either overestimated or underestimated.
Action focus: inspection evidence quality, coverage, and recency improvements.
Decision Guidance by Driver Dominance
Driver-to-Action Matrix
| Dominant Driver Pattern | Typical Meaning | First Recommended Move | Expected Direction |
|---|---|---|---|
| Severity > Uncertainty/Detection | Actual operating conditions likely drive the likelihood | Stabilize chemistry/process window and reassess | Score reduction |
| Uncertainty high | Data quality or age limits confidence | Improve inspection evidence and data quality | Confidence increase |
| Detection high | Detectability limitation risk | Adjust inspection method, interval, or coverage | Detectability improvement |
| Mixed profile | Multiple coupled mechanisms | Stage actions and validate after each step | Controlled convergence |
Remediation Paths (Advanced Users)
What Remediation Paths Do
Remediation Paths mode converts risk-driver outputs into actionable pathways and projects scenario impact.
Typical pathway families:
- Defend Asset Life: operational change pathways (for example temperature, sulfur, TAN, or flow-window changes).
- Inspection Evidence Refresh: inspection-evidence pathways (for example inspection effectiveness upgrades).
- Monitoring and Inspection Upgrade: controls and monitoring pathways (for trend protection and conservative tracking).
Remediation Quick Reference (Example)
Pathway Families
| Pathway Family | Typical Trigger | Typical Action | Expected Direction |
|---|---|---|---|
| Defend Asset Life | Severity-dominant risk, harsh chemistry/flow window | Adjust the operating envelope (temperature, sulfur, TAN, WSS) | Score reduction |
| Eliminate Uncertainty | Uncertainty or detection drivers dominate | Upgrade the inspection campaign and improve evidence quality | Confidence increase |
| Strengthen Monitoring | Trend instability or hidden acceleration concern | Enable monitoring and apply conservative control posture | Variability reduction |
How to Use Remediation Paths
- Run Analyze first and review the baseline score.
- Ensure exactly one material is selected. Multi-material comparison remains available for normal analysis, but remediation must be evaluated and applied one material at a time because process-condition targets are shared across the active case.
- Click Activate Remediation Paths.
- Wait until the status changes to Remediation Paths Mode Active.
- Review the Problem detected statement and the grouped pathway cards.
- Select one or more pathway checkboxes.
- Compare projected scenario status and score to baseline.
- Click Apply Selected Actions to commit the selected pathways. The tool applies the targets, reruns all calculations automatically in the background, adds the committed pathways to the report basket, and keeps Remediation Paths mode active.
- Keep only practical pathways, then include justification in your report.
What to Read in Each Pathway Card
- Action: what operational or inspection step is proposed.
- Result: expected outcome and projected score direction.
- Engineering recommendation: API-aligned inspection/coverage guidance when relevant.
- Top matrix scenarios: best candidate operating combinations for Defend Asset Life pathways.
Report Integration
Applied pathways are already added to the report basket. Use Append Engineering Justification to Report separately when engineering rationale, assumptions, or implementation constraints should be included in the generated report.
Practical Selection Guidance
- Pick pathways that are implementable within your outage, access, and budget constraints.
- Prefer pathways that reduce score and improve evidence quality together.
- Do not select conflicting pathways only because each looks good in isolation.
- Re-run Analyze after implementing real field changes to verify actual effect.
What Good Looks Like
- Selected actions are technically feasible and operationally acceptable.
- The projected reduction is meaningful and not achieved through unrealistic assumptions.
- Data confidence improves, not only the score.
- Follow-up inspection and monitoring steps are explicitly scheduled.
Important Limitations
- Pathway projection is a decision-support estimate, not a guaranteed field outcome.
- If no prior analysis exists, remediation evaluation cannot run.
- PTA SCC hard-stop states remain FFS-gated and should be resolved before claiming PTA-driven reduction.
- Pathway logic is based on configured rule sets and model assumptions; engineering review is still mandatory.
Best practice: apply one practical pathway set at a time, then re-run and validate the real effect against baseline.
Common Mistakes to Avoid
- Assuming direct equivalence when comparing results between Predictive and Inspection modes.
- Changing multiple inputs simultaneously, then over-interpreting the resulting rank order.
- Treating a single score as pass/fail without considering the operational context.
- Ignoring data quality warnings when uncertainty is the dominant driver.
Troubleshooting
Open Troubleshooting Checklist
- No result: verify required fields and date/year validity.
- Unexpected ranking: verify mode, baseline, and PTA/morphology toggles.
- Counter-intuitive trend: verify corrosion-rate source, inspection context, chemistry envelope, and PTA branch flags.
Reporting Template (Short)
When documenting an analysis, include:
- Analysis mode and context (asset, unit, operating window).
- Baseline score and dominant drivers.
- Selected remediation pathway(s) and why.
- Expected outcome and residual uncertainty.
- Planned validation step (next inspection/monitoring check).
Report Quality Gate
- What changed is explicitly identified.
- Why it changed is technically justified.
- Residual uncertainty is stated.
- Verification step and timing are scheduled.
Status rule: mark Ready for Approval only when all items are checked.
Key Terms
Open Key Terms
Severity
How damaging current degradation behavior is expected to be.
Uncertainty
How much confidence is limited by data quality and time context.
Detection Limitation
Limitations in identifying damage due to inspection method, coverage, or morphology effects.
Localized Damage Morphology
When localized damage is present, the screening calculation applies a morphology amplification to the Bayesian thinning damage factor. This can materially increase the risk score even when the modeled or measured corrosion rate is unchanged. The ranking is a relative decision-support signal, not a localized-pitting fitness-for-service assessment. The displayed remaining life remains based on uniform thinning: (thickness - t_min) / CR_eff.
Low Confidence in Historical Data
Data quality issue (trustworthiness/completeness).
Outdated Inspection Data
Data age issue (staleness over time).
CR Map
A heuristic, model-informed explanation layer that highlights the dominant current corrosion-rate drivers. It does not replace the base corrosion calculation or engineering review.
PTA SCC Present (PASCC Overlay)
Enables the PTA SCC PASCC overlay branch. If thinning DF and PTA SCC DF are both active, the backend combines them through an API 581-style multi-damage-mechanism DF path before Pf/logPf/score are derived. Unresolved crack states trigger FFS gating and keep the run thinning-governed for that calculation.
Need Deeper Technical Detail?
For more details on IRI functionality, please contact Corrology Engineering Team.