Agni Raksha Niti Engineering Consultancy Services Pvt. Ltd.

Industrial Process Safety: Systems, Hazards, and Incidents

1. Instrumented Safety System (ISS) vs. Manual System

The fundamental difference lies in reliability, response time, and independence. ISS is designed to be "passive" (acting only when things go wrong), whereas manual/control systems are "active" (constantly managing the process).

Feature	Manual / Basic Process Control System (BPCS)	Instrumented Safety System (ISS / SIS)
Role	Active: Controls normal production (e.g., maintains temp at 100°C).	Passive: Dormant until a hazard occurs (e.g., trips reactor if temp hits 120°C).
Response Time	Slow: Relies on human reaction (minutes) or basic loops.	Instantaneous: Milliseconds to seconds (automated trip).
Human Error	High: Prone to fatigue, misinterpretation, or hesitation.	Low: Pre-programmed logic prevents unauthorized bypass/error.
Fail-Safe	No: Failure often goes undetected until an accident.	Yes: Designed to fail safely (e.g., valve closes on air failure).
Architecture	Single layer (Sensor → HMI → Operator).	Redundant layers (2oo3 voting, separate sensors/logic solvers).
Standard	Good Engineering Practice.	IEC 61511 / IEC 61508 (SIL Rated 1-4).

2. Equipment-Specific Hazards & PSSR Checkpoints

A. Chemical Reactor (CSTR / Batch)

Hazards: Runaway exothermic reactions, agitator mechanical failure, seal leaks (toxic release), static electricity ignition (in glass-lined vessels), thermal shock.
PSSR Checkpoints (Pre-Startup):
- Verify Agitator rotation direction and RPM interlocks.
- Check Rupture Disc/Safety Valve calibration and pass-through logic.
- Confirm Jacket/Coil pressure test certificates (hydro-test).
- Static Dissipation: Ensure earthing continuity (resistance < 10 ohms) and use of anti-static hoses.
- Compatibility: Verify MOC (Material of Construction) vs. chemicals (e.g., no Fluorine in glass-lined).
- Emergency Dump: Test bottom outlet valve (BOV) remote actuation.

B. Autoclave (High Pressure)

Hazards: Steam explosion, door opening under pressure (projectile hazard), superheated liquid boil-over, seal failure leading to toxic release.
PSSR Checkpoints:
- Door Interlock: Confirm door cannot open if internal pressure > 0.1 bar.
- Hydro-test: Verification of vessel integrity at 1.5x design pressure.
- Safety Valve: Pop-test certificate availability.
- Gasket: Inspect specific "lip seal" or O-ring condition; ensure no cuts.

C. Rotary Vacuum Dryer (RVD / RCVD)

Hazards: Dust explosion (during discharge), vacuum implosion, seal leakage (solvent vapor release), mechanical fatigue on rotating joint.
PSSR Checkpoints:
- Vacuum Tightness: Drop test (should hold vacuum for 1 hour with defined drop limit).
- Earthing: Rotary contact earthing (carbon brushes) must be intact to prevent static buildup in dry powder.
- Jacket Media: Confirm temp control loop to prevent product thermal decomposition.
- Lump Breaker: Check blade clearance to prevent metal-to-metal sparking.

D. Distillation Column

Hazards: Flooding (pressure spike), dumping (tray damage), "Jet Fire" from flange leaks, accumulation of unstable peroxides in reboiler.
PSSR Checkpoints:
- Verticality: Check alignment (plumbness).
- Tray Installation: Verify weir height and downcomer clearance.
- Relief System: Flare header connection and N2 purging (to prevent explosive mixture).
- Leak Test: N2 pressure hold test for all flange joints.

E. Centrifuge

Hazards: Mechanical bursting (basket failure), vibration-induced rupture, friction fire (static + solvent), operator injury (lid opening while running).
PSSR Checkpoints:
- Zero Speed Interlock: Lid must not unlock until RPM is 0.
- Vibration Switch: Trip test (simulate high vibration).
- N2 Blanketing: Oxygen analyzer interlock (machine won't start if O2 > 5-8%).
- Mother Liquor Line: Ensure no blockage (back-pressure can lift the lid).

3. Integrity Tests During Operation (Online)

These tests verify the equipment is safe while it is running, without shutting down.

Equipment	Operational Integrity Test / Monitoring	Purpose
Reactor	Acoustic Emission Testing	Detects micro-cracks or glass-lining damage by "listening" to stress waves.
	Thermography	Scans jacket/body for hot spots indicating insulation failure or lining damage.
	pH Monitoring (Jacket)	Sudden pH change in jacket water indicates a reactor leak (acid entering utility).
Autoclave	Online Seal Leak Detection	Monitoring pressure between double mechanical seals.
RVD	Vacuum Hold Check (Daily)	Monitor rate of vacuum loss during idle operational periods.
	Earthing Brush Monitor	Continuous monitoring of resistance on the rotating drum earthing.
Column	Gamma Scanning	Isotopes scan the column density profile to detect flooding, foaming, or damaged trays.
	Corrosion Monitoring	ER (Electrical Resistance) probes installed in lines to measure thinning rates online.
Centrifuge	Vibration Analysis	Continuous spectrum analysis to detect bearing wear or unbalance before failure.
	Oxygen Analysis	Continuous sampling of headspace to ensure inert N2 atmosphere (<5% O2).

4. Major Industrial Incidents in India (2024-2025)

Based on the current timeline (Nov 2025), the following recent major incidents highlight the risks of this equipment.

Incident & Date	Location	Equipment	Root Cause	Fatalities / Impact
Sigachi Industries (June 30, 2025)	Sangareddy, Telangana	Spray Dryer / Drying Unit	Dust Explosion: Pressure buildup in Microcrystalline Cellulose (MCC) drying unit. Reactive dust + heat + inadequate venting.	~46 Dead, 30+ Injured Total structural collapse of 3-story building.
Escientia Advanced Sciences (August 21, 2024)	Anakapalli, Andhra Pradesh	Reactor & Electrical Layout	Design Fault: Solvent leak from reactor on upper floor dripped onto Electrical MCC Panel on ground floor. "Fire under fuel tank" scenario.	17 Dead, 35+ Injured Chemical burns, vapor cloud explosion.
Sahithi Pharma (June 2023)	Anakapalli, Andhra Pradesh	Solvent Reactor	Solvent Handling: Fire broke out during solvent transfer/charging into the reactor involving static electricity/human error.	2 Dead, 5 Injured Escalated to major fire involving storage tanks.
Yashashvi Rasayan (June 2020)	Dahej, Gujarat	Storage Tank / Reactor	Runaway Reaction: Failure to control temp in a storage vessel/reactor reacting uncontrollably.	5 Dead, 50+ Injured Blast heard 20km away; massive toxic smoke.

5. Escalation Potential & Loss Analysis

Domino Effect: In congested Indian chemical parks (like Dahej, Hyderabad, Anakapalli), a reactor blast often ruptures nearby solvent tanks (as seen in Sahithi and Escientia), turning a localized equipment failure into a site-wide inferno.
Toxic Release: Failure of seal integrity in reactors/autoclaves often releases toxic clouds (e.g., Chlorine, Bromine), causing casualties far beyond the factory fence line (community impact).
Financial Loss: Beyond equipment replacement (Cr. INR), losses include:
- Business Interruption: 3-6 months closure by Pollution Control Board (PCB) / Inspector of Factories.
- Legal Liability: Compensation (approx. 15-25 Lakhs INR per deceased family + legal penalties).
- Reputation: Blacklisting by global pharma clients.

Industrial Process Safety: Systems, Hazards, and Incidents

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