Gaseous Fire Extinguishing Systems - Carbon Dioxide Total Flooding and Local Application ( Sub-Floor and In-Cabinet), High and Low Pressure (Refrigerated) Systems
2004 Edition

Overview of IS 15528 Scope

• Encompasses design, installation, and commissioning of CO2 fire suppression systems.
• Addresses both total flooding and local application configurations.
• Emphasizes enclosure integrity to retain CO2 gas effectively.
• Accounts for ambient pressure variations with necessary adjustments.

Critical Tables and Equations

Orifice Discharge Rates (Clauses 9.6, 9.7.5)

Utilized for determining CO2 flow through orifices.

Orifice Dimensions (Clause 9.7.4)

Select orifice size based on required flow parameters.

Altitude Pressure Corrections (Clause 6.3.4)

[ N_{adj} = N \times \frac{P_{ambient}}{760} ] Where:

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

Carbon Dioxide Uses (Clause 4.2)

CO2 is effective in extinguishing:

• Class A fires: Fires involving carbon-based solids with glowing embers.
• Class B fires: Fires involving flammable and combustible liquids.
• Class C fires: Fires involving combustible gases, except where explosive atmospheres might develop after suppression.
• Electrical fires: Live electrical equipment.

Design Concentration for Flammable Substances (Clause 6.4.2)

• The design CO2 concentration equals the theoretical minimum plus an additional 30% margin.
• Minimum CO2 concentration must not fall below 34% by volume.

Theoretical Minimum Concentration Calculation

For materials not listed in the standard table: [ % CO_2 = \frac{2 \times 100}{21 - O_2} \times 21 ] Where (O_2) is the residual oxygen percentage post CO2 application.

Sample Theoretical Minimum Concentrations

Refer to IS 15528 Table 3 for complete data.

Note: Deep-seated fires (Clause 6.5) may require increased CO2 amounts and specialized application techniques.

Safety Devices (Clause 9.5)

• Installation of interlocks, protective relays, and emergency shutoffs is mandatory.
• Devices must function reliably under fault conditions to prevent hazards.

Electrical Clearance (Clause 5.2.2)

• Maintain prescribed minimum distances between energized components and grounded or other live parts.

Additional Safety Measures (Clause 5.2)

• Use clear signage and physical barriers.
• Implement lockout/tagout procedures.
• Ensure personal protective equipment (PPE) usage.

Personnel Safety (Clause 5.1)

• Design systems to avoid accidental contact.
• Provide safe access and egress.
• Conduct training and awareness programs.

Rate by Area Method (Clause 6.14)

• CO2 quantity is based on the floor area of the protected enclosure.
• Suitable for well-defined spaces ensuring adequate suppression concentration.

Rate by Volume Method (Clause 6.15)

• CO2 quantity depends on the total volume of the enclosure.
• More accurate for irregular or larger spaces, considering leakage.

Total Flooding System Requirements (Clause 6.2)

• Enclosure must be gas-tight to prevent CO2 escape.
• Ventilation and openings should close automatically upon discharge initiation.
• Additional CO2 is necessary if openings cannot be sealed.
• Applicable to spaces such as rooms, ducts, ovens, and containers.

Electrical Clearance from CO2 Equipment (Clause 5.2.2)

Design Essentials (Clauses 6.2 & 6.4.5)

• Enclosures must be sealed tightly to retain CO2.
• Automatic closure of openings and ventilation is required during discharge.
• Additional CO2 quantities must be added if openings remain unsealed.
• Wind-exposed openings need special consideration.

Flooding Factors and Design Concentrations

Volume Factor Adjustments

High-Temperature Adjustments

• Increase CO2 quantity by 1% for every 5°F (2.8°C) above 200°F (93°C) to prevent reignition.

Key Calculation Principles

1. Minimum Design Concentration (Clause 6.4.2):

   • No less than 34% CO2 by volume.
   • For flammable substances: Design concentration = Theoretical minimum + 30% of theoretical minimum.

2. Theoretical Minimum Calculation (if absent in Table 3): [ % CO_2 = \frac{2 \times 100}{21 - O_2} \times 21 ] Where (O_2) = residual oxygen percentage.

3. Basic Quantity (Clauses 6.3 & 6.4.4):

   • Use volume factor from Table 4 to compute base CO2 volume.
   • Multiply by material conversion factor if concentration >34% (Fig. 2).

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

• (X): CO2 quantity in kg
• (Q): Protected space volume (m³)
• (KVP): Correction factor for pressure and temperature.

Volume Factor Usage (Clauses 6.4.3 & Table 4)

• Determines base CO2 quantity for 34% design concentration.

• For connected volumes, sum quantities using factors.
• Use higher concentration if any section requires >34%.

Material Conversion Factor (Clause 6.4.4)

• Multiply base quantity by factor for materials needing >34% concentration.

Adjustments for Special Conditions

• Account for unclosable openings, forced ventilation, air receivers, and altitude.
• For temperatures above 93°C, add 1% CO2 per 5°F (2.8°C) increment.

Design Basis (Clause 6.5)

• CO2 concentration depends on combustible material mass due to heat insulation.
• Flooding factors derived from empirical testing (see Table 5).

Requirements

• Maintain minimum design concentration for at least 20 minutes after reaching target.
• Enclosure must be airtight; no leakage allowance is made.
• Flooding factors vary by material and mass; refer to Table 5 or seek approval for non-standard cases.

Calculation

[ \text{CO}_2 \text{ needed (kg)} = \text{Flooding Factor} \times \text{Enclosure Volume (m}^3)]

Sample Flooding Factors (Table 5)

Purpose

• To sustain minimum CO2 concentration over time in the presence of leakage, by applying CO2 at a reduced continuous rate after initial flooding.

Key Details

1. Extended discharge rate must maintain the design concentration considering leakage.
2. Design concentration and flooding factors are provided in Table 5 (Clause 6.5.2).

3. Rate of application varies with fire type:

Calculation

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

• (Q) = CO2 quantity (kg)
• (V) = Hazard volume (m³)
• (F) = Flooding factor (m³/kg CO2)

Extended rate must compensate for leakage to maintain minimum concentration.

Hazard Isolation (Clause 6.10)

• Entire hazard including areas with combustible coatings from spills, leaks, drips, splashes, or condensation must be protected.
• Include related equipment and materials such as freshly coated stock, drain boards, hoods, and ducts.
• Prevent fire propagation beyond protected zones.
• Large hazards may be sectioned into smaller zones upon regulatory approval.
• Systems must provide immediate, independent protection to adjacent hazard sections.

Enclosure Considerations (Clauses 1.2 & 6.15.2)

• Minimum enclosure dimension assumed as 1.2 m for volume calculations.
• Volume adjustments made for wind or forced air drafts.
• Walls and ceilings should be at least 0.6 m from hazards.
• Enclose all leakage or spillage zones.
• No volume deductions for solid objects inside the protected space.

Flooding Factors and Concentrations (Table 5, Clause 6.5.2)

Extended Application Rate (Clause 6.7.3)

• Discharge must sustain minimal design concentration to secure hazard protection.

Storage Container Requirements (Clauses 8.2.1 & 8.3.1)

• Containers conform to IS 8198 (Parts 1 & 3).
• Filled with dry CO2; filling ratio is 0.667 ± 25% (liquefiable gas mass to water capacity at 15°C).
• Internal surfaces must be dry.
• Safety relief devices must be fitted unless integrated within container design.
• Refrigerated low-pressure containers adhere to similar standards.

Container Arrangement (Clause 8.2.2)

• One cylinder bank per hazard, or combined for separate hazards.
• Total bank capacity equals the largest CO2 requirement among hazards.
• Zones in flooding systems are flooded independently.
• Operating temperature ranges:
  • Total flooding: -18°C to 55°C
  • Local application: 0°C to 49°C
• Employ external heating/cooling when outside temperature limits.
• Pilot and slave cylinders arranged to manage discharge pressures; minimum one extra pilot cylinder beyond requirements.
• Maximum 20 cylinders per discharge system using nitrogen pilot pressure.

Discharge Rate Tables (Clause 64.5)

Pressure Ratings (Clauses 8.2 & Table 7)

Discharge Rates for High-Pressure Storage (Clause 9.6 & Table 10)

Manifold Relief Valve Settings (Clause 3.1)

• Relief valve set at 3.1 MPa for low-pressure systems.
• High-pressure systems must ensure valves and piping withstand up to 15.5 MPa.

Distribution Piping Design

• Sized per Clause 6 based on maximum storage pressure.

System Pressure Parameters (Clause 9.1 & Table 7)

Discharge Rate Data for Low-Pressure Storage (2.07 MPa)

Notes

• Piping must withstand maximum developed pressure (3.1 MPa).
• Discharge rate calculated as: [ \text{Discharge Rate} = \text{Orifice Area} \times \text{Discharge Rate per mm}^2 ]
• Use corresponding orifice pressure values for calculations.

Electrical Clearance Requirements (Clause 5.2.2 & Table 1)

• Maintain minimum air gap between CO2 system parts and live uninsulated electrical components.

Total Flooding System Setup (Clause 6.2)

• Enclosures must prevent CO2 leakage.
• Automatic closure of openings and ventilation prior to or concurrent with discharge.
• Additional CO2 needed if enclosure cannot be sealed.
• Applicable to rooms, vaults, ducts, ovens, containers.

Discharge Rate Tables for Low-Pressure Storage (Clause 64.5)

Piping System (Clause 6.16.2)

• Must supply the required discharge rate at each nozzle.
• Designed according to Clause 9.
• Operating temperature range: 0°C to 49°C without special measures.

Example Calculation

For 50% enclosed perimeter: [ F = (0.5 \times 12) + 4 = 10 ] Discharge rate = 10 × E kg

Nozzle Marking (Clause 9.7.8)

• Nozzle must carry a permanent mark indicating its equivalent single orifice diameter.
• For diameters ≥ 2.38 mm, include code number from Table 8.

Cross-Sectional Area Criteria

• Use Table 8 for pipe areas in surface fire setups.
• Use Table 9 for deep-seated fire systems.

Pipe and Orifice Sizing (Clause 9.6)

Flow rate formula: [ 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): Internal pipe diameter (mm)
• (L): Equivalent pipeline length (m)
• (Y, Z): Factors based on storage and line pressure.

Summary

• Mark nozzles with diameter and code number (if ≥ 2.38 mm).
• Adhere to cross-sectional area limits based on fire type.
• Apply sizing formula for pipe and orifice selection.