Fire Safety in Petroleum Refineries and Fertilizer Plants - Code of Practice

IS 15394: Scope - Key Specifications & Tables

Scope Overview: IS 15394 covers fixed fire protection installations, focusing on safe spacing between hazardous units like storage vessels, plants, and utilities to prevent fire hazards.

Key Spacing Distances (Clause 2.1)

Additional Notes:

• Distances are measured between outermost points of nearest equipment.
• For plants inside buildings, measure from external wall to nearest equipment or external wall of adjoining plant.
• Nitrogen use for purging and blanketing is emphasized in design to prevent fires (Clause 15.10).

References Incorporated:

• IS 1239 (Part 1): Mild steel tubes
• IS 2190: Fire extinguishers
• IS 5572: Hazardous area classification
• IS 10221: Coating of underground pipelines
• IS 15325: Water spray system design

flowchart LR
    A[Plant] -- 20m --> B[Inter Plant]
    A -- 25m --> C[Tankage]
    A -- 50m --> D[Hydrocarbon Spheres/Bullets]
    A -- 15m --> E[Utilities/Buildings]
    C -- 25m --> D
    C -- 15m or diameter --> F[Other Tank]

This summary ensures safe layout planning per IS 15394 to minimize fire risks in industrial setups.

IS 15394: Spacing of Equipment Within a Unit

Key Points from Clause 3.2 & Annex A:

• No fixed formula for minimum spacing; depends on technological requirements and equipment type.
• Hydrogen processing units require greater spacing due to higher fire temperatures (up to 1400°C), compared to oil units (650°C–1100°C).
• Fire hazard considerations and use of nitrogen blanketing/purging (Clause 15.10) must be integrated early in design.
• Measurement basis for spacing (Annex A):
  • Distance = between outermost points of nearest equipment in adjoining plants.
  • Pipe racks are ignored.
  • For buildings, measure from external wall to nearest equipment or external wall of adjoining plant.

General Recommendations for Spacing

Design Considerations

• Use risk analysis to determine spacing.
• Incorporate fireproofing, nitrogen purging, and emergency access.
• Factor in equipment maintenance and operational safety.

flowchart LR
    A[Technological Requirements] --> B{Type of Process}
    B -->|Oil| C[Spacing for 650-1100°C fire temp]
    B -->|Hydrogen| D[Spacing for >1400°C fire temp]
    C --> E[Measure outermost equipment points]
    D --> E
    E --> F[Ignore pipe racks]
    F --> G{Plant Location}
    G -->|Open Yard| H[Distance between equipment]
    G -->|Building| I[Distance from external walls]

This approach ensures safety and operational efficiency per IS 15394 guidelines.

IS 15394: Plant Layout and Pipe Racks - Key Specifications & Formulas

1. Pipe Rack Location & Height (Clauses 4.1 & 4.2)

• Pipe racks for individual units run centrally, dividing equipment areas.
• Minimum pipe rack height from ground: 3 m.
• Major pipe racks must be:
  • At least 5 m away from hydrocarbon process equipment.
  • At least 6 m high when crossing roads.
• Protection against mechanical damage (cranes, fire appliances) is mandatory.

2. Fire Resistance (Clause 4.1, 7.5)

• Pipe supports (vertical & horizontal) require fire resistance:
  • 2 hours fire exposure minimum (50 mm concrete or equivalent).
• Near major equipment (heaters, pumps, vessels):
  • Within 7.5 m: 3 h fire resistance.
  • Between 7.5 m to 15 m: 2 h fire resistance.
  • Beyond 15 m: Fire resistance generally not required unless special conditions.
• No cantilever pipe racks allowed.
• Fin fan cooler supports above pipe racks need 2 h fire resistance.
• Vessels with large liquid hold-up above pipe racks require 3 h fire resistance.

3. Spacing Between Plants (Annex A)

• Distance measured between outermost equipment points, ignoring pipe racks.
• For plants in buildings, measure from external walls.

4. Additional Considerations

• Nitrogen purging and blanketing to prevent fires must be considered early (Clause 15.10).

Summary Table: Fire Resistance Requirements for Pipe Rack Supports

flowchart TD
    A[Pipe Rack] --> B{Distance from Major Equipment}
    B -->|≤ 7.5 m| C[3 h Fire Resistance]
    B -->|7.5 m < d ≤ 15 m| D

IS 15394: Tankage Location and Restrictions – Key Points

Minimum Spacing (Clause 12.2 & Annex A)

• LPG bullets/spheres and flammable/combustible liquid tanks must be detached from other properties by minimum spacing per Annex A.
• Spacing depends on tank size, type, and hazard level (refer Annex A for exact distances).

Layout Orientation (Clause 12.3)

• Horizontal tanks' longitudinal axis must NOT point towards vital process areas or critical structures.
• Reason: Tanks can rupture and move along their axis (rocket effect), causing severe damage.

Diking & Drainage for Spherical Tanks (Clause 12.15)

• Follow atmospheric tank diking capacity limits.
• Ground beneath spheres must be graded to drain leaks to a collection basin within the dyke.
• Basin location: As far as possible from the sphere to minimize risk.

Process Unit Restrictions (Clause 5.1)

• Only day tanks allowed within battery limits of process units.
• No other tankage permitted inside this boundary.

Example: Minimum Spacing Table (from Annex A)

(Note: Refer to IS 15394 Annex A for detailed and exact values)

flowchart LR
    A[Horizontal Tank] -->|Rocket Effect| B[Potential Movement]
    B --> C{Is Axis Pointing to Vital Area?}
    C -- Yes --> D[High Risk of Damage]
    C -- No --> E[Reduced Risk]

Summary: Maintain prescribed spacing, orient tanks away from vital areas, ensure proper diking and drainage, and restrict tankage within process boundaries per IS 15394.

IS 15394: Control Rooms & Blast Resistant Construction Key Points

Control Room Location & Design (Clause 6.1, 6.4)

• Minimum distance from process units:
  • 15 m for single units
  • 30 m for multiple units (preferred)
• Blast resistant control rooms required:
  • Within 120 m of light hydrocarbon/hydrogen units
• Control room features:
  • Single storey, no rooftop equipment
  • Located on plant periphery, adjacent to road/parking
  • Plinth elevated above surrounding plant level
  • Minimum two exits with separate unobstructed escape routes
  • Blast resistant baffle walls at opposite doors with 45°/90° overlap

Blast Resistant Construction (Clause 7.1)

• Design for static overpressure of 3 MPa
• Peak overpressure depends on explosion energy & distance
• Blast wave assumed perpendicular to building face
• Risk evaluation to decide construction type

Blast Pressure Estimation (Conceptual)

• Calculate explosion energy (based on vessel contents)
• Use distance to estimate peak overpressure on control room
• Match overpressure to structural resistance

Typical Blast Resistant Construction Parameters

Simplified Blast Overpressure Conceptual Diagram

flowchart LR
    A[Explosion at Process Unit] --> B[Blast Wave Propagation]
    B --> C[Peak Overpressure at Control Room]
    C --> D[Blast Resistant Control Room Design]
    D --> E[Structural Integrity & Safety]

Note: For detailed blast load calculations, refer to IS 15394 Annexures or specialized blast load standards (e.g., API 752, UFC 3-340-02).

IS 15394: Blast Resistant Construction Key Points

1. Minimum Distances (Clause 6.1 & 6.4)

• Control building to process unit: ≥ 15 m (single unit), ≥ 30 m (two or more units).
• Preferably maintain 30 m to reduce fire & shrapnel risk.
• Control rooms within 120 m of hydrocarbon/hydrogen units must be blast resistant.

2. Blast Loading & Design Pressure (Clause 7.1 & 6.1)

• Calculate peak overpressure (P₀) at control building based on distance and explosion energy.
• Design control room for a static overpressure of 3 MPa.
• Blast resistant construction type depends on risk evaluation.

3. Control Room Specifications

• Single-storey, no rooftop equipment.
• Located on plant periphery, not surrounded by equipment.
• Plinth elevated above surrounding plant level.
• At least one side adjacent to road/parking.
• Minimum two exits with separate escape routes.
• Blast resistant baffle walls at opposite doors with 45°/90° overlap.

4. Blast Overpressure Estimation (Conceptual)

• Estimate explosion energy (e.g., TNT equivalent).
• Use empirical charts or formulas (not in IS 15394 but common practice):

[ P = \frac{A}{R^3} ]

Where:

• (P) = peak overpressure,
• (R) = distance from blast center,
• (A) = explosion energy constant.

5. Additional Notes

• Toxic gas analyser exhausts must be outside control rooms.
• Hydrocracker/hydrotreaters require special blast protection due to higher explosion potential.

flowchart LR
    A[Process Unit Explosion] --> B[Calculate Explosion Energy]
    B --> C[Determine Peak Overpressure at Control Room]
    C --> D{Is P > 3 MPa?}
    D -- Yes --> E[Design Blast Resistant Control Room]
    D -- No --> F[Standard Construction]
    E --> G[Implement Specified Construction & Safety Features]

Summary: Maintain minimum distances, design control rooms for 3 MPa static overpressure, ensure proper layout and exits, and use

IS 15394: Ventilation and Vapor Control - Key Points

1. Ventilation Design (Clause 8.2 & 8.1)

• Hydrocarbon vapors are heavier than air → ventilation must include floor-level fresh air inlets.
• For basements or below-ground floors, forced ventilation is necessary.
• Gas compressor shelters should be open-sided or have abundant fresh air ventilation.
• Pumps and compressors must be in free-ventilated areas with ventilation openings at floor level in all directions.

2. Vapor Conservation & PV Vents (Clause 12.6)

• Use Pressure Vacuum (PV) vents for tank breathing and filling vapors.
• Flame propagation through PV vents is negligible → flame arresters are unnecessary.
• Use no-freeze PV vents in freezing climates to avoid tank damage.
• Provide one standby PV vent valve at 100% capacity.

Summary Table: Ventilation & Vapor Control

Ventilation Flow Concept (Mermaid Diagram)

flowchart LR
    A[Fresh Air Inlet - Floor Level] --> B[Hydrocarbon Vapor Zone]
    B --> C[Exhaust Ventilation - Higher Level]
    D[Basement/Below Ground] --> E[Forced Ventilation System]
    E --> B

For detailed design, refer to IS 5572 for hazardous area classification and IS 15325 for fire protection systems related to vapor hazards.

IS 15394 Key Points on Drainage and Sewer Systems

1. Sewer System Design (Clause 11.3)

• Capacity: Size for normal runoff + additional capacity for fire-fighting water disposal.
• Separation: Avoid combining storm water and process drains.
• Slope: Provide adequate slope both longitudinally and latitudinally from center to perimeter.
• Chemical Drainage: Separate localized drains for incompatible chemicals.
• Emergency Draining: Control valves with instrument air/nitrogen supply must be available during power failure.

2. Vapor Control (Clause 11.2)

• Fire Stops/Water Seals: To prevent vapor spread in sewer/drainage ditches.
• Sealing & Venting: Sealed sections must be vented to avoid pressure build-up and seal failure.

3. Underground Mains (Clause 14.4.13)

• Layout: Prefer closed circuit mains over dead ends.
• Distance: Maintain minimum 5 m clearance from process/storm water channels to avoid seepage effects.

Typical Sewer Slope Recommendations

Schematic of Drainage System Layout

flowchart LR
    A[Center of Unit] -->|Slope| B[Perimeter Drain]
    B --> C[Industrial Sewer System]
    C --> D[Fire Stops/Water Seals]
    D --> E[Vented Sections]
    subgraph Chemical Drain
        F[Localized Drain for Incompatible Chemicals]
    end
    A --> F

Summary: Design drainage with adequate slope, separate incompatible chemical drains, size for fire water, use fire stops/water seals, vent sealed sections, and maintain underground mains away from seepage zones.

IS 15394: Storage Tank Safety - Key Points & Specifications

Construction & Material (Clauses 12.4, 12.5)

• Welding is the preferred construction method; bolted/riveted tanks are discouraged.
• Bolted tanks must never be used for products with flash point < 65°C due to gas-tightness issues.
• For low flash point products, use:
  • Standard cone top (weak roof seam)
  • Floating roof tanks
  • Standard pressure tanks

Safety & Layout (Clause 12.15)

• For spherical pressure tanks:
  • Follow diking and capacity limits as per atmospheric tanks.
  • Ground must be graded to drain any spillage to a collection basin outside the dyke and away from the tank.

Fire & Ignition Protection (Clause 12.7)

• Prevent static ignition by:
  • Proper grounding and bonding.
  • Lightning protection systems.
  • Filling pipe must be above suction pipe; suction pipe submerged in liquid.
  • Filling vapor space velocity ≤ 1 m/s.
• Refer to API RP 2003 for detailed static ignition prevention.

Summary Table for Tank Types & Use

flowchart LR
    A[Storage Tank Safety] --> B[Construction]
    B --> C[Welding Preferred]
    B --> D[No Bolted Tanks for Flash Point < 65°C]
    A --> E[Tank Types]
    E --> F[Cone Top / Floating Roof / Pressure Tank for Low Flash Point]
    E --> G[Atmospheric Tanks for Others]
    A --> H[Safety Measures]
    H --> I[Static Ignition Prevention]
    H --> J[Lightning Protection]
    H --> K[Proper Filling Pipe Position]
    H --> L[Diking & Drainage for Spherical Tanks]

For detailed design and safety compliance, always refer to IS 15394 and related API standards.

IS 15394: Electrical Equipment Key Points

• Hazardous Areas (Clause 13.1 & 13.2):

  • No sparking/arcing electrical equipment allowed unless flame-proof or building is pressurized with clean air (per IS 5572).
  • Generators must be ≥ 30 m away from gas hazardous zones.
  • Substation switching equipment within 15 m of hazardous areas must be in pressurized buildings.
  • Prefer placing substations away from hazardous zones to reduce costs.

• Electrical Installations (Clause 3.2 & 13.2):

  • Electrical circuits in process areas should be installed in underground conduits.
  • Overhead conduits on pipe racks are vulnerable to fire damage.
  • Power distribution cables must be buried underground except final motor/lighting connections.
  • Underground cable trenches should be:
    • Filled with sand, or
    • Provided with concrete baffles every 45 m.

Summary Table: Minimum Distances & Installation Practices

Flame-proof Equipment Requirement (IS 5572 Reference)

• Equipment must prevent ignition of flammable gases.
• Typical flame-proof types: motors, switches, lighting fixtures.

flowchart LR
    A[Hazardous Area] -->|No sparking equipment| B[Flame-proof Electrical Equipment]
    A -->|Pressurized building| C[Clean Air Pressurization]
    D[Generator] -->|≥30 m distance| A
    E[Substation] -->|≤15 m distance| F[Pressurized Building]
    G[Electrical Circuits] -->|Underground conduits| A
    H[Cables] -->|Buried underground| A

For detailed flame-proof specifications, consult IS 5572 and

IS 15394: Fire Protection Arrangements – Key Points

Fixed Water Spray/Deluge System (Clause 15.7)

• Automatic operation: Essential, especially in critical hazard zones.
• Actuation delay: ≤ 30 seconds.
• Valve types: Avoid lever-operated gate valves & quarter-turn plug valves.
• Nozzle distance: ≤ 0.6 m from surface.
• Area drains: Capacity = max water discharge rate.
• Water demand: ≤ 50% of fire water pumping capacity.
• Hydraulic calculations: As per relevant IS standards (e.g., IS 15325).
• Maintenance: Inspection & cleaning every 6 months.

Application Rate for Critical Equipment (Clause 15.6)

• Water spray rate: 0.61 m³/h/m³ for pipe racks, valve manifolds, control equipment.

Access in Multi-storied Buildings (Clause 14.4.22)

• Staircases per compartment:
  • Area < 500 m²: 1 staircase.
  • Area 500–2000 m²: 2 staircases.
  • Above 2000 m²: +1 staircase per additional 1500 m².
• Max distance to staircase: 30 m.
• External staircases: Must be open to sky.

Reference Standards

flowchart LR
    A[Fire Hazard Area] --> B{Critical?}
    B -- Yes --> C[Automatic Water Spray System]
    B -- No --> D[Manual or Other Protection]
    C --> E[Actuation ≤ 30s]
    C --> F[Nozzle ≤ 0.6 m from surface]
    C --> G[Water Demand ≤ 50% Pump Capacity]
    C --> H[Inspect & Clean every 6 months]

For detailed hydraulic design, refer IS 15325 and IS 15394 clauses above.

IS 15394: Fixed Water Spray and Deluge Systems - Key Points

Design Specifications (Clause 15.7)

• Automatic operation preferred, especially for critical hazards.
• Max actuation delay: 30 seconds.
• Valve restrictions: No lever-operated gate or quarter-turn plug valves.
• Nozzle distance: ≤ 0.6 m from protected surface.
• Area drains: Capacity = max discharge rate of system.
• Water demand limit: ≤ 50% of fire water pump capacity.
• Hydraulic calculations: Follow relevant Indian Standards.
• Maintenance: Inspection, testing, and cleaning every 6 months.

Application Rates

Additional Notes

• Design area should be individually considered based on equipment criticality.
• Ensure system capacity matches hydraulic calculations for reliable performance.

flowchart TD
    A[Fire Hazard] --> B{Critical?}
    B -- Yes --> C[Automatic Spray System]
    B -- No --> D[Manual or Semi-Automatic]
    C --> E[Max 30s Delay]
    E --> F[Nozzle ≤ 0.6m from Surface]
    F --> G[Valve Restrictions]
    G --> H[Hydraulic Calculations]
    H --> I[Maintenance - 6 Monthly]

This summary aligns with IS 15394 clauses 15.5 to 15.7 for effective fixed water spray/deluge system design.