Gaseous Fire Extinguishing Systems - Carbon Dioxide Total Flooding and Local Application ( Sub-Floor and In-Cabinet), High and Low Pressure (Refrigerated) Systems

IS 15528: Scope - Key Specifications & Tables

Scope Summary:

• Covers design and commissioning of CO₂ fire suppression systems.
• Includes total flooding and local application systems.
• Requires enclosure tightness to retain CO₂ gas.
• Specifies adjustments for ambient pressure variations.

Key Tables & Formulas

1. Orifice Discharge Rate (Clause 9.6, 9.7.5)

Used to calculate CO₂ discharge through orifice areas.

2. Orifice Sizes (Clause 9.7.4)

Select orifice size based on required flow.

3. Pressure Adjustment for Altitude (Clause 6.3.4)

[ N_{adj} = N \times \frac{P_{ambient}}{P_{sea-level}} ]

• (N_{adj}): Adjusted number of CO₂ containers
• (N): Number at sea level
• (P_{ambient}): Ambient enclosure pressure (mm Hg)
• (P_{sea-level} = 760) mm Hg

4.

IS 15528: Uses and Specifications of Carbon Dioxide (CO2) for Fire Extinguishing

1. Uses of Carbon Dioxide (Clause 4.2)

CO2 is effective for extinguishing:

• Class A fires: Carbonaceous solids with glowing embers (organic materials).
• Class B fires: Flammable and combustible liquids.
• Class C fires: Combustible gases (except where post-extinguishment explosive atmospheres may form).
• Electrical fires: Live electrical apparatus.

2. Design Concentration for Flammable Materials (Clause 6.4.2)

• The design concentration of CO2 = Theoretical minimum concentration + 30% factor.
• Minimum CO2 concentration shall not be less than 34% by volume.

3. Theoretical Minimum CO2 Concentration Calculation

For materials not listed in Table 3, use:

[ \text{Percent CO}_2 = \frac{2 \times 100}{21 - O_2} \times 21 ]

Where:

• ( O_2 ) = residual oxygen percentage in the atmosphere after CO2 application.

4. Table 3 (Excerpt: Theoretical Minimum CO2 Concentrations for Common Materials)

(Refer to IS 15528 Table 3 for full list)

Summary Diagram: CO2 Fire Extinguishing Applications

graph LR
A[Carbon Dioxide Uses] --> B[Class A Fires]
A --> C[Class B Fires]
A --> D[Class C Fires]
A --> E[Electrical Fires]

Note: For deep-seated fires (Clause 6.5), higher CO2 quantities and special application methods may be required. Always consult the latest edition of IS 15528 and referenced standards for detailed design.

IS 15528 Safety Requirements Summary

1. Safety Devices (Clause 9.5)

• Must be installed to prevent hazardous conditions.
• Include interlocks, protective relays, and emergency stops.
• Devices should operate reliably under fault conditions.

2. Electrical Clearance (Clause 5.2.2)

• Minimum clearance between live parts and grounded parts or other live parts is mandatory.
• Table 1 (Typical values):

Clearance must consider insulation, environmental conditions, and maintenance access.

3. Safety Precautions (Clause 5.2)

• Proper signage and barriers.
• Lockout/tagout procedures.
• Use of PPE for personnel.

4. Safety of Personnel (Clause 5.1)

• Design to prevent accidental contact.
• Safe access and egress.
• Training and awareness.

flowchart TD
    A[System Components] --> B[Maintain Electrical Clearance]
    B --> C[Install Safety Devices]
    C --> D[Ensure Personnel Safety]
    D --> E[Follow Safety Precautions]

Key takeaway: Maintain clearances per Table 1, install reliable safety devices, and prioritize personnel safety through design and procedures.

IS 15528: System Design Key Points

1. Rate by Area Method (Clause 6.14)

• Design CO₂ quantity based on area of enclosure.
• Suitable for well-defined enclosed spaces.
• Ensures sufficient CO₂ concentration to suppress fire.

2. Rate by Volume Method (Clause 6.15)

• CO₂ quantity calculated based on volume of enclosure.
• More precise for irregular or large spaces.
• Requires knowledge of enclosure volume and leakage rates.

3. Total Flooding Systems Design (Clause 6.2)

• Enclosure must prevent gas escape.
• Openings/ventilation must close automatically with discharge.
• Additional CO₂ required if openings cannot be sealed or no walls/ceilings exist.
• Applicable to rooms, vaults, ducts, ovens, containers.

4. Clearance from CO₂ Equipment to Live Electrical Components (Table 1, Clause 5.2.2)

IS 15528: Total Flooding Systems Basis for Design

Key Design Principles (Clause 6.2 & 6.4.5)

• Enclosures must be gas-tight to prevent CO₂ escape.
• Openings/ventilation must close automatically before or simultaneously with CO₂ discharge.
• If openings cannot be sealed, additional CO₂ quantity per Clause 6.7 is required.
• Special consideration for openings exposed to wind.

Flooding Factors & Design Concentrations (Tables 5 & 6.4.3)

Volume Factor for Space Size (Table 6.4.3)

Additional CO₂ for High Temperature (Above 93°C)

• Add 1% more CO₂ for every 5°F (≈2.8°C) above 200°F (93°C) to prevent reignition.

Clearance from CO₂ Equipment to Live Electrical Components (Table 1, Clause 5.2.2)

| Nominal Voltage (kV

IS 15528: Design Quantity of Carbon Dioxide

Key Points & Formulas

1. Design Concentration (Clause 6.4.2):

   • Minimum CO₂ concentration = 34%
   • For flammable materials, use:
     [ \text{Design Concentration} = \text{Theoretical Minimum} + 30% \text{ of Theoretical Minimum} ]
   • Theoretical minimum values are in Table 3 (common liquids/gases).

2. Theoretical Minimum CO₂ Concentration (if not in Table 3):
   [ % CO_2 = \frac{2 \times 100}{21 - O_2} \times 21 ] where (O_2) = residual oxygen percentage.

3. Basic Quantity Calculation (Clause 6.3 & 6.4.4):

   • Use volume factor from Table 4 to find basic CO₂ volume.
   • For concentrations > 34%, multiply by Material Conversion Factor from Fig. 2.

4. CO₂ Supply Quantity (Clause 247.3):
   [ X = 247.3 \times Q \times KVP ] where:

   • (X) = quantity of CO₂ (kg)
   • (Q) = volume of protected space (m³)
   • (KVP) = correction factor for pressure and temperature.

Summary Table Example (Excerpt from Table 3)

flowchart TD
    A[Determine Hazard Material] --> B{Is material in Table 3?}
    B -- Yes --> C[Use Theoretical Minimum from Table 3]
    B -- No --> D[Calculate Theoretical Minimum using O2 formula]
    C & D --> E[Calculate Design Concentration = Theoretical + 30%]
    E --> F{Is Design Concentration > 34%?}
    F -- Yes --> G[Calculate Basic Quantity × Conversion Factor (Fig. 2)]

IS 15528: Volume Factor & Special Conditions Summary

1. Volume Factor (Clause 6.4.3 & Table 4)

Used to determine the basic CO₂ quantity for 34% design concentration:

• For interconnected volumes, sum quantities using respective volume factors.
• Use higher concentration if any volume requires more than 34%.

2. Material Conversion Factor (Clause 6.4.4)

For materials needing >34% CO₂, multiply basic quantity by conversion factor (see Fig. 2 in code).

3. Special Conditions Adjustments

• Account for unclosable openings, forced ventilation, air receivers, altitude, etc.
• For high temperature (>93°C), increase CO₂ quantity by 1% for every 5°F (2.8°C) above 200°F (93°C) to prevent reignition.

Formula for Total CO₂ Quantity:

[ Q = V_f \times V + Q_{special} ]

Where:

• (Q) = total CO₂ quantity (kg)
• (V_f) = volume factor (kg CO₂/m³) from Table 4
• (V) = volume of space (m³)
• (Q_{special}) = additional CO₂ for special conditions (e.g., ventilation, temperature)

flowchart LR
    A[Calculate Volume of Space

IS 15528: Carbon Dioxide Requirements for Deep-Seated Fires (Clause 6.5)

• Design Concentration Basis:

  • CO₂ concentration depends on mass of combustible material due to thermal insulation.
  • Flooding factors are empirically derived from practical tests (Table 5).

• Key Specifications:

  • Design CO₂ concentration must be maintained for minimum 20 minutes after reaching the required level.
  • Enclosure must be tight; leakage is critical as no allowance is made in flooding factors.
  • Flooding factors vary with material type and mass; use Table 5 for standard hazards.
  • For non-standard materials, justify flooding factor to the authority considering thermal insulation.

Typical Table 5 Format (Example):

Important Formula:

[ \text{CO}_2 \text{ required (kg)} = \text{Flooding Factor (kg/m}^3) \times \text{Volume of enclosure (m}^3) ]

flowchart TD
    A[Start: Identify combustible material] --> B{Is it deep-seated fire?}
    B -- Yes --> C[Refer Table 5 for flooding factor]
    C --> D[Calculate CO₂ quantity]
    D --> E[Ensure tight enclosure]
    E --> F[Maintain CO₂ concentration ≥ design value for ≥ 20 min]
    B -- No --> G[Refer surface fire requirements (Clause 6.4)]

Summary: For deep-seated fires, use Table 5 flooding factors, maintain CO₂ for ≥20 min in tight enclosures, and consider thermal insulation effects on mass of material.

IS 15528 - Extended Rate of Application (Clause 6.7)

• Purpose: To maintain the minimum CO₂ concentration over an extended period when leakage is appreciable, by applying CO₂ at a reduced (extended) rate after initial flooding.

Key Points & Formulas:

1. Extended Rate of Discharge:

   • Must be sufficient to maintain the minimum design concentration after initial flooding.
   • Used for leakage compensation over time.

2. Design Concentration & Flooding Factor (Table 5, Clause 6.5.2):

3. Rate of Application (Clause 6.6):

Calculation Outline:

• Quantity of CO₂ required (Q):

[ Q = \frac{V}{F} ]

Where:

• (V) = volume of hazard (m³)

• (F) = Flooding factor (m³/kg CO₂)

• Extended Rate (R_ext):
  Maintain minimum concentration considering leakage rate (L):

[ R_{ext} \geq L \times C_{min} ]

Where:

• (L) = leakage volume/time
• (C_{min}) = minimum design concentration

Diagram: CO

IS 15528: Hazard Specification Key Points

1. Hazard Isolation (Clause 6.10)

• Entire hazard area must be protected including:
  • Areas with combustible liquid/solid coatings (spillage, leakage, dripping, splashing, condensation).
  • Associated equipment/materials (freshly coated stock, drain boards, hoods, ducts).
• Fire spread outside the protected zone must be prevented.
• Large hazards can be subdivided into smaller sections with regulatory approval.
• Systems must provide immediate independent protection to adjacent groups.

2. Assumed Enclosure (Clause 1.2 & 6.15.2)

• Minimum dimension: 1.2 m for volume calculation.
• Increase volume for wind/forced drafts.
• Enclosure walls/ceiling at least 0.6 m from hazard.
• Enclose all leakage/spillage areas.
• No volume deductions for solid objects inside.

3. Flooding Factors & Design Concentrations (Table 5, Clause 6.5.2)

4. Extended Rate of Application (Clause 6.7.3)

• Discharge rate must maintain minimum design concentration for hazard protection.

flowchart TD
    A[Hazard Area] --> B[Assumed Enclosure]
    B --> C{Walls & Ceiling}
    C -->|≥ 0.6 m from hazard| D[Enclose leakage/spillage]
    D --> E[Calculate Volume (min 1.2 m dimension)]
    E --> F[Apply Flooding Factor from Table 5]
    F --> G[

IS 15528: Storage Containers & System Types - Key Points

1. Storage Containers (Clause 8.2.1 & 8.3.1)

• Must comply with IS 8198 (Part 1 & 3).
• Filled with dry CO₂, max filling ratio 0.667 ± 25% (mass of liquefiable gas to water capacity at 15°C).
• Containers must be internally dry.
• Safety pressure relief device mandatory if not in container design, fitted on valve.
• Low-pressure refrigerated containers follow same standards.

2. Storage Container Arrangement (Clause 8.2.2)

• One bank per hazard or combined if hazards are separate.
• Total bank quantity = largest CO₂ quantity needed for any single hazard.
• Flooding system zones flooded individually.
• Temperature range:
  • Total flooding: -18°C to 55°C
  • Local application: 0°C to 49°C
• Use external heating/cooling if outside these ranges.
• Pilot cylinders and slave cylinders arranged for pressure release; minimum one pilot cylinder more than needed.
• Max 20 cylinders per discharge system using N₂ pilot pressure.

3. Discharge Rate Tables (Clause 64.5)

Summary

IS 15528: High-Pressure Systems Key Points

1. Pressure Specifications (Clause 8.2 & Table 7)

2. Discharge Rate for High-Pressure Storage (Table 10, Clause 9.6)

Discharge rate per 64.5 mm² or equivalent orifice area at ~5.17 MPa:

3. Manifold Relief Valve Setting (Clause 3.1)

• Relief valve set to 3.1 MPa for low-pressure systems.
• For high-pressure systems, ensure valves and piping withstand up to 15.5 MPa.

4. Sizing Distribution Systems

• Refer Clause 6 for sizing high-pressure distribution piping based on max developed storage pressure.

Summary Diagram: Pressure Levels in High-Pressure Systems

graph LR
A[Nominal Storage

IS 15528: Key Data for Low-Pressure Systems (Clause 8.3)

1. System Pressure (Clause 9.1 & Table 7)

2. Discharge Rate for Low-Pressure Storage (2.07 MPa)

(From Table 9, Clause 64.5)

3. Important Notes

• Piping Design: Must withstand max developed storage pressure (3.1 MPa for low-pressure systems).
• Discharge Rate Calculation:
  [ \text{Discharge Rate (kg/min)} = \text{Orifice Area (mm}^2) \times \text{Discharge Rate (kg/min/mm}^2) ]
• Use appropriate orifice pressure from the table depending on system conditions.

flowchart LR
    A[Low-Pressure System] --> B[Nominal Storage Pressure: 2.1 MPa]
   

IS 15528 Installation Requirements Summary

1. Electrical Clearance (Clause 5.2.2 & Table 1)

Minimum clearance between CO₂ system components and live uninsulated electrical parts is critical:

Clearance is air distance between equipment and live parts.

2. Total Flooding System Design (Clause 6.2)

• Enclosure must prevent CO₂ escape.
• Openings/ventilation must close automatically before or with discharge.
• Additional CO₂ quantity required if openings cannot be sealed.
• Applicable to rooms, vaults, ducts, ovens, containers, etc.

3. Discharge Rate Tables (Clause 64.5)

Low-Pressure Storage (2.07 MPa):

Use these for sizing nozzles and piping.

4. Piping System (Clause 6.16.2)

• Must deliver required discharge rate at each nozzle.
• Design per Clause 9.
• Temperature range: 0° to 49°C without special compensation.

5. Discharge Rate Calculation Example

For 50% enclosed perimeter:

[ F = (0.5 \times 12) + 4 = 10 ]

Discharge rate = (10 \times E) kg

IS 15528: Nozzle Design and Installation Key Points

1. Nozzle Marking (Clause 9.7.8)

• Nozzle must be marked permanently with its equivalent single orifice diameter.
• For diameters ≥ 2.38 mm, a code number from Table 8 must also be marked.

2. Cross-Sectional Area Limits

• Use Table 8 for pipe cross-sectional areas in surface fire protection.
• Use Table 9 for pipe cross-sectional areas in deep seated protection.

3. Pipe and Orifice Size Calculation (Clause 9.6)

The pressure drop and flow rate relationship is given by:

[ Q_y = 10^{-5} \times 0.8725 \times D^{5.25} \times Y \times L^{0.04319} \times D^{1.25} \times Z ]

Where:

• ( Q_y ) = flow rate (kg/min)
• ( D ) = inside pipe diameter (mm)
• ( L ) = equivalent pipeline length (m)
• ( Y, Z ) = factors depending on storage and line pressure

Summary:

• Mark nozzles with equivalent diameter + code (if ≥ 2.38 mm).
• Respect cross-sectional area limits depending on fire protection type.
• Use the formula above to size pipe and orifice for required flow and pressure.

flowchart LR
    A[Determine Fire Protection Type] --> B{Surface or Deep Seated?}
    B -->|Surface| C[Use 35%-85% area limits (Table 8)]
    B -->|Deep Seated| D[Use 3%-85% area limits (Table 9)]
    C --> E[Calculate pipe & orifice size using formula]
    D --> E
    E --> F[Mark nozzle with equivalent