Have you considered developing Integrity Operating Windows (IOWs)?

An IOW program will promote operation within controlled ranges, which leads to predictable damage rates.

Q: The damage mechanisms in API 571 sometimes fit my processes and equipment, but mostly they don’t. What can I do to get more appropriate damage mechanisms descriptions?

A: Develop Corrosion Control Documents (CCDs) with damage mechanism descriptions written and developed for your processes and equipment.

Q: My site has a robust inspection program. We follow the API inspection code requirements. Why are we still having leaks?

A: Analysis of many fixed equipment failures has shown that prolonged operation outside of recommended ranges is a key root cause.

CCD Key Elements:

  • Corrosion Material Drawings link damage mechanisms to equipment and show material of construction (see example below).
  • Optional: Corrosion Loop Drawings. These are better suited for processes with more damage mechanisms.
  • Damage mechanism descriptions written specifically for the unit’s operation, stream chemistry, and metallurgy.
  • Utility damage mechanism descriptions can also be included.
  • Inspection, repair, and replacement highlights.
  • Detailed assessment of existing metallurgy for anticipated future operation.
  • Recommendations for effective inspection and replacement (in needed).
  • IOWs = Recommendations (for Operations) to obtain predictable damage rates that will, in time, minimize leaks and unplanned outages.
Corrosion Material Drawings link damage mechanisms to equipment

CCDs and IOWs are reliability tools that help move a plant organization from reactive to proactive.

IOW Key Goals

Operation within IOW limits is intended to result in predictable and reasonably low rates of equipment degradation.

IOWs ensure good communication of equipment limits and exceedances between key Process, Operation, and Mechanical Integrity personnel such that equipment can be safely managed and operated without loss of containment.

Operating Window

Relationship between IOW limits and potential damage rates

IOW Key Elements

  • A list of the recommended IOWs.
  • Recommended test or sampled location and frequency for the IOW.
  • Recommended limits (Max/Min/Target) for the IOW.
  • Recommended API 584 IOW type (Informational/Standard/Critical).
  • Possible consequences of IOW exceedances/deviations.
  • Corrosion loop or loops impacted by the IOW
  • Recommended Operations/Process responses to IOW deviations.
  • Recommended Inspection/SME responses to IOW deviations.

Development of CCDs & IOWs

  • Road map for developing CCDs is given in API 970 and for IOWs in API 584.
  • E2G follows a streamlined process to provide a concise and easy-to-use product.
  • Best results are obtained when all key stakeholders are fully involved.

Benefits of CCDs with IOWs

A CCD with IOWs is a proactive tool that can support and improve plant organizations:


  • Where to inspect
  • How to inspect (what type of damage to look for)
  • Supports RBI
  • Supports root cause analysis for fixed equipment failures
  • Supports new designs



  • Set limits
  • Establish integrity monitoring
  • Define action steps when outside limits


Operations practices to avoid/minimize damage during:

  • Shutdowns
  • Downtimes
  • Start-ups


  • Engineers, Operators, Inspectors
  • Understand how a process change or IOW impacts damage mechanisms
  • Understand impact when operating outside of desired limit

Download CCD-IOW – Petrochemical Brochure

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