📋 Case Study

Ammonia Refrigeration System PHA & LOPA Integration at Midwest Food Plant

Outdated PHA documentation; no SIL verification for emergency shutdown valves

🏗️ Project Overview

Retrofit of legacy ammonia refrigeration system serving 300k sq ft food processing facility

🎯 Challenge

Outdated PHA documentation; no SIL verification for emergency shutdown valves

🔧 Design Approach

Integrated HAZOP + LOPA workshop with cross-functional team; redefined IPLs and validated SIS architecture against IEC 61511

📐 Design Diagram

AI-generated project design illustration

📐 Key Calculations

LOPA IPL Verification

PFD = ∏(1 − PFD_ipl)

Result: PFD = 0.0023 → SIL 2 confirmed

Confirmed adequacy of existing SIS without costly hardware upgrade

📊 Results

PHA revalidation completed in 8 weeks; 100% IPL verification achieved; $420k avoided SIS replacement cost

💡 Lessons Learned

• •LOPA must be performed *after* PHA, not concurrently
• •Operator input is critical for credible initiating event identification

✅ Key Takeaways

• 1LOPA must be performed *after* PHA, not concurrently
• 2Operator input is critical for credible initiating event identification