IIAR 6-2025: What's New in the Updated Inspection, Testing & Maintenance Standard

The International Institute of Ammonia Refrigeration released IIAR 6-2025 — the updated edition of Standard for Inspection, Testing, and Maintenance of Open-Circuit Ammonia Refrigerating Systems — bringing a revised framework for mechanical integrity programs that PSM- and RMP-covered facilities need to understand before their next compliance audit.

If your facility operates under OSHA 29 CFR 1910.119 or EPA 40 CFR Part 68, IIAR 6 is the industry-recognized standard for satisfying the Mechanical Integrity (MI) element. OSHA and EPA both accept IIAR standards as recognized and generally accepted good engineering practices (RAGAGEP). An outdated MI program that doesn't reflect the current edition is a finding waiting to happen.

What Changed From IIAR 6-2019

1. Expanded Equipment Scope

IIAR 6-2025 clarifies and expands the list of equipment categories subject to inspection and testing requirements. The 2025 edition adds explicit guidance for:

• Recirculator/accumulator vessels with expanded internal inspection intervals tied to corrosion allowance and material of construction
• Evaporative condensers and fluid coolers with new coil-integrity testing criteria separate from condenser shell inspection
• Variable frequency drives (VFDs) and electronic expansion valves (EEVs) — previously handled only informally — now have defined functional test intervals
• Ammonia detectors and control-system interlocks with tightened documentation requirements for calibration records and alarm setpoint verification

2. Revised Inspection Intervals

One of the most operationally significant changes is the restructuring of inspection intervals based on system operating conditions rather than calendar time alone.

| Component | IIAR 6-2019 Interval | IIAR 6-2025 Interval | |---|---|---| | Pressure vessels (external visual) | Annual | Annual (unchanged) | | Pressure vessels (internal inspection) | 5 years or per API 510 | Risk-based per API 581 criteria or 10 years max | | PRVs (in-service test or replacement) | 5 years | 5 years (unchanged), but dual-valve arrangements get extended interval up to 10 years with documentation | | Relief device discharge piping | At PRV service | Separate annual visual inspection added | | Mechanical seals (compressors) | Condition-based | Condition-based + maximum 3-year documented inspection | | Control system interlocks | Annual functional test | Annual + documented setpoint verification with as-found/as-left recording |

The risk-based internal inspection pathway for pressure vessels is a meaningful change. Facilities with well-documented corrosion monitoring, operating history, and low-corrosivity service conditions can now justify extended internal inspection intervals up to 10 years — reducing operational burden without reducing safety — provided the risk assessment is documented and reviewed by a qualified inspector.

3. Relief Device Discharge Piping — Standalone Requirement

IIAR 6-2019 addressed discharge piping as part of the PRV inspection task. IIAR 6-2025 separates this into a distinct annual inspection requirement. Inspectors must document:

• Visual condition of all atmospheric discharge piping including rain caps, bird screens, and vent terminations
• Pipe support condition and evidence of vibration-induced fatigue at connections
• Any evidence of liquid carryover or oil accumulation in the discharge line

This matters in practice: discharge piping deficiencies are among the most commonly cited MI findings in PSM audits, and they're frequently missed when bundled into the PRV task. The standalone requirement puts them on their own inspection record.

4. Documentation and Record-Keeping Tightened

The 2025 edition is significantly more prescriptive about what inspection records must contain. Each inspection record must now capture:

• As-found condition before any corrective action, not just the post-repair status
• Inspector qualifications — either third-party credentials (API 510, NB-23) or documented in-house qualification basis
• Acceptance criteria used — the specific standard, table, or engineering basis against which the finding was evaluated
• Deficiency disposition — whether the deficiency was repaired immediately, tracked as a follow-up item, or accepted with an engineering basis for continued operation

This aligns IIAR 6 more closely with API 510 and OSHA's expectation that MI records demonstrate a complete audit trail, not just a pass/fail result.

5. Pressure Relief Valve — Dual-Valve Arrangements

IIAR 6-2025 formalizes the extended inspection interval for parallel (dual-valve) PRV arrangements. When two PRVs are installed in parallel with an isolation valve arrangement meeting IIAR 2 requirements, and when the isolation valve position is documented and locked, facilities may extend the individual valve service interval to 10 years rather than 5 — provided:

Each valve is individually tracked with its own service record

The isolation valve changeover procedure is documented and trained

The in-service valve is confirmed in the open position by periodic documented inspection

This is a substantial operational benefit for large systems with many PRVs. A 10-year service interval on properly arranged dual-valve installations cuts PRV service labor and downtime in half.

What This Means for Your PSM/RMP Program

Update Your RAGAGEP Reference

If your PSM/RMP program documents reference IIAR 6-2019 as the applicable standard, you should update that reference to IIAR 6-2025 following your Management of Change (MOC) procedure. The change affects:

• Your MI program description
• Inspection frequency tables
• Any procedure documents that cite edition-specific section numbers

Review Inspection Intervals Against the New Edition

Walk through your current inspection schedule and compare it against the IIAR 6-2025 intervals. In most cases facilities will find:

• PRV dual-valve arrangements — opportunity to extend intervals with proper documentation
• Pressure vessel internal inspections — potential to shift to risk-based schedule with API 581 evaluation
• Discharge piping — may need a standalone inspection task added to the program

Update Inspection Record Templates

If your MI records don't currently capture as-found condition, inspector qualifications, and acceptance criteria, those fields need to be added. An OSHA PSM audit that pulls MI records and finds no as-found documentation is a likely citation.

Control System Interlocks

If your current program only records annual functional test results without capturing as-found and as-left setpoint values, IIAR 6-2025 now requires that level of documentation. This is especially relevant for high-pressure cutout (HPCO), oil pressure differential, and ammonia detector alarm/shutdown interlocks.

What NH3Edge Can Do for Your Facility

NH3Edge provides mechanical integrity program development and gap assessments against current IIAR standards. If your program was written against IIAR 6-2019 or an earlier edition, a structured gap assessment will identify every departure from the current standard before an auditor does.

Our services include:

• IIAR 6-2025 gap assessment against your existing MI program documentation
• Inspection record template development meeting the 2025 as-found/as-left and acceptance criteria requirements
• Risk-based inspection (RBI) evaluation for pressure vessels seeking extended internal inspection intervals under the API 581 pathway
• PRV dual-valve interval analysis — confirming whether your existing valve arrangements qualify for the 10-year interval and documenting the basis

Contact us at info@nh3edge.com or use the contact form to schedule a consultation.

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This post reflects NH3Edge's interpretation of IIAR 6-2025 for informational purposes. Facilities should obtain and review the standard directly from IIAR and consult with a qualified engineer before making changes to their mechanical integrity program.