Gaseous Fire Extinguishing Systems - IG 55 Extinguishing Systems

IS 15506: Key Formulas, Tables & Specifications for Scope

1. Enclosure Volume Calculations (Clause 7.3.1)

[ \begin{aligned} V_{\text{Max}} &= V_u - V_s \ V_{\text{Min}} &= V_{\text{Max}} - V_o \end{aligned} ]

• (V_u): Gross enclosure volume (m³)
• (V_s): Volume of permanent objects impermeable to gas (m³)
• (V_o): Volume of occupancy objects impermeable to gas (m³)
• (V_{\text{Max}}): Maximum net enclosure volume (m³)
• (V_{\text{Min}}): Minimum net enclosure volume (m³)

2. Total Flooding Quantity of IG 55 (Clause 7.2 & 2.303)

[ M = 2.303 \times S \times V \times \log_{10} \left(\frac{100}{100 - C}\right) ]

• (M): Total flooding quantity (kg)
• (C): Design concentration (% by volume)
• (V): Net volume of hazard (m³)
• (S = K_1 + K_2 \times T)
  • (K_1 = 0.6598), (K_2 = 0.00242) (IG 55 constants)
  • (T): Minimum enclosure temperature (°C)

Refer Table 8 for agent mass per unit volume vs temperature and concentration.

3. Pipe Sizes vs Flow Rate (Clause 11.3, Table 10)

IS 15506: General Information Key Formulas & Tables

1. Enclosure Volume Calculations (Clause 7.3.1)

• Maximum net volume: [ V_{Max} = V_u - V_s ]
• Minimum net volume: [ V_{Min} = V_{Max} - V_o ]

Where:

• (V_u) = Gross enclosure volume (m³)
• (V_s) = Volume of structural/permanent objects impermeable to gas (m³)
• (V_o) = Volume of occupancy-related objects impermeable to gas (m³)

2. Total Flooding Quantity for IG 55 (Table 8, Clause 7.2)

Use this table to find IG 55 mass required per unit enclosure volume based on temperature and design concentration.

3. Safety Precautions (Clause 5.4, Table 5 & 6)

4. Venting Area Calculation

[ A = Q \times \left(2 P_s\right)^{-0.5} ]

Where:

• (A) = Venting area (m²)
• (Q) = Max

IS 15506: Key Gas Characteristics & Properties for IG 55

1. IG 55 Gas Composition (Clause 4.2 & Table 1)

• Argon: 50 ± 5% by volume
• Nitrogen: 50 ± 5% by volume

2. Component Specifications (Clause 4.4 & Table 2)

3. Physical Properties of IG 55 Gas (Clause 4.5 & Table 3)

4. Operating Pressure & Temperature (Clause 1.4)

• Normal pressure: 15 MPa at 21°C or 20 MPa at 21°C

Additional Notes:

• IG 55 extinguishes fire by reducing oxygen concentration.
• Minimum concentration must be maintained until temperature falls below re-ignition point.
• Discharge time: ~60 seconds, consider fire type suitability.

flowchart TD
    A[IG 55 Gas] --> B[50% Argon]
    A --> C[50% Nitrogen]
    B --> D[Purity ≥ 99.9%]
    C --> E[Purity ≥ 99.9%]
    A --> F[Physical Properties]
    F --> G[Molecular Mass: 33.95]
    F --> H[Boiling Point

IS 15506 - Concentration Requirements for IG 55 (MA) Fire Extinguishing Agent

Key Formula for Total Flooding Quantity (Clause 2.303)

[ M = 2.303 \times C \times V \times \log_{10} \left(\frac{100 - C_S}{100 - C}\right) \times V_3 ]

Where:

• M = Total agent quantity required (kg)
• C = Design concentration (% by volume)
• V = Net volume of hazard (m³)
• C_S = Concentration after leakage allowance
• V₃ = Specific volume of superheated agent at 21°C (m³/kg)
• S = K₁ + K₂(T), with:
  • (K_1 = 0.6598)
  • (K_2 = 0.00242)
  • (T) = Minimum enclosure temperature (°C)

Table 8: Agent Requirement per Unit Volume vs Concentration & Temperature

(Example values for IG 55)

Note: Use exact values from IS 15506 Table 8 for design.

Atmospheric Correction (Clause 7.4)

[ N_1 = N \times \text{Atmospheric Correction Factor} ]

• N = Initial number of containers
• N₁ = Adjusted number of containers
• Correction factors per altitude (Table 9):

Important Notes:

• Oxygen concentration limits as per Clause 5.3 must be respected.
• Use the **

IS 15506: Protection of Occupants & Safety Precautions for IG 55 Systems

Key Safety Limits (Clause 5.4, Table 6)

• NOAEL: No Observed Adverse Effect Level
• LOAEL: Lowest Observed Adverse Effect Level

Minimum Safety Precautions (Clause 5.4, Table 5)

Note: Concentrations above LOAEL are prohibited in occupied areas.

Venting Area Calculation (Clause 6)

[ A = Q \times (2P)^{-0.5} ]

Where:

• ( A ) = Venting area required (m²)
• ( Q ) = Maximum IG 55 flow in enclosure (kg/s)
• ( P ) = Maximum allowed overpressure (500 Pa)

Enclosure Volume (Clause 7.3.1)

• ( V_{max} = V_u - V_s )
• ( V_{min} = V_{max} - V_o )

Where:

• ( V_u ) = Gross enclosure volume (m³)
• ( V_s ) = Volume of permanent objects impermeable to gas (m³)
• ( V_o ) = Volume of occupancy-related objects impermeable to gas (m³)

Total Flooding Quantity (Clause 7.2, Table 8)

• Mass of IG 55 per unit volume depends on temperature and design concentration.
• Refer to Table 8 for

IS 15506: Enclosure Strength and Venting Facilities

Key Formulas:

• Venting Area (A):

[ A = Q \times (2P)^{-0.5} ]

Where:

• (A) = venting area (m²)

• (Q) = max IG55 flow in enclosure (kg/s) = Total weight / discharge duration (s)

• (P) = max allowed overpressure = 500 Pa

• Specific Vapor Volume of IG55/Air Mixture (S3):

[ S_3 = C \times S + S_2 \times (100 - C)/100 ]

Where:

• (S_3) = specific vapor volume of IG55/air mixture at 20°C
• (C) = injected IG55 concentration (%)
• (S = 0.708 , m^3/kg) (IG55 vapor volume at 20°C)
• (S_2 = 0.830 , m^3/kg) (air vapor volume at 20°C)

Safety Concentration Limits (Table 6):

• NOAEL: No Observed Adverse Effect Level
• LOAEL: Lowest Observed Adverse Effect Level

Minimum Safety Precautions (Table 5 Summary):

Note: Concentrations above LOAEL are not permitted in occupied areas.

This ensures safe enclosure design with adequate venting to limit pressure and maintain safe IG55 concentrations.

IS 15506: Application Rate and Discharge Time

1. Application Rate (Clause 9.1)

• The minimum injected concentration for IG-55 agent for Class A combustible solids is ≥ 40% by volume.
• This ensures a residual oxygen concentration of 14% in the enclosure.
• Application rate depends on enclosure volume and agent concentration.

2. Pipe Sizes vs Flow Rate (Clause 11.3, Table 10)

3. Discharge Time (Clause 12.4)

• Predicted discharge time by flow calculations must match actual discharge time within ±5 seconds.
• Ensures reliability and accuracy of system performance.

Summary Formula for Application Rate:

[ \text{Application Rate} = \frac{\text{Agent Quantity (kg)}}{\text{Enclosure Volume (m}^3\text{)}} ]

• Adjust agent quantity to achieve ≥ 40% volume concentration IG-55.
• Use pipe size and flow rate table for system design.

Atmospheric Correction (Clause 7.4 Table 9)

• Use correction factor based on

IS 15506 Key Formulas & Specifications for IG 55 Storage Containers

1. Enclosure Volume Calculations (Clause 7.3.1)

• Maximum net volume:
  [ V_{Max} = V_u - V_s ]
• Minimum net volume:
  [ V_{Min} = V_{Max} - V_o ]

Where:

• (V_u) = Gross enclosure volume (m³)
• (V_s) = Volume of permanent objects impermeable to gas (m³)
• (V_o) = Volume of occupancy-related objects impermeable to gas (m³)

2. IG 55 Agent Quantity (Clause 7.3.2)

• Theoretical IG 55 quantity:
  [ M_{th} = V_{Max} \times C_1 ]
• Number of containers:
  [ N = \frac{M_{th}}{M_c} ]
• Actual agent quantity:
  [ M_A = N \times M_c ]
• Actual injected concentration:
  [ C_{AL} = \frac{M_A}{V_{Max}} ]

Where:

• (C_1) = Design injected concentration (volume %)
• (M_c) = Quantity per container (m³)
• (N) = Number of containers

3. Storage Container Specifications (Clause 10)

• Seamless cylinders conforming to IS 7285
• Design pressure suitable for max pressure at 65°C or max controlled temperature
• Must have reliable pressure indicators and pressure/temperature charts
• Must comply with Chief Controller of Explosives, Nagpur requirements

4. Mass Requirements per Enclosure Volume (Table 8, Clause 7.2)

IS 15506: Distribution System Key Points

1. Pipe Sizing (Clause 11.3)

• Proper pipe sizing balances pressure loss and flow velocity.
• Use Table 10 (Clause 11.3) as a guide for pipe sizes vs flow rates (kg/min):

• Verify sizing with hydraulic calculations or approved software.

2. Pressure Testing (Clause 11, Distribution System)

• Hydrostatic test at 1.5 × max storage pressure at 55℃.
• Purge system to remove moisture and ensure free passage.

3. Enclosure Integrity (Clause 11)

• Conduct enclosure integrity test as per IS 15493 to ensure retention of agent.

4. Retention Time (Clause 9.3)

• At least 80% of design concentration must remain after 10 minutes post-discharge.

Summary Diagram: Distribution System Flow

flowchart LR
    A[Storage Container] --> B[Pipe Network]
    B --> C[Nozzles]
    C --> D[Protected Enclosure]
    D --> E[Retention of Agent (≥80% after 10 min)]

IS 15506 Key Points for Piping Network (Clauses 11.1 - 11.3):

1. Piping Network (Clause 11.1)

• Pipes must withstand maximum pressure at max storage temperature.
• Follow IS 15493 for pipe material and pressure ratings.
• Carbon steel pipes: Galvanized inside & outside or corrosion-protected.
• Stainless steel pipes: Corrosion protection not required.

2. Piping Fittings (Clause 11.2)

• Must comply with IS 15493.
• Select fittings based on pipe schedule number (wall thickness).

3. Pipe Sizing (Clause 11.3 & Table 10)

• Proper sizing balances pressure loss and flow velocity.
• Use Table 10 for flow rate ranges (kg/min) vs pipe size (mm), Schedule 40 & 80:

• Verify sizing with approved flow calculation software.

Formula for Pressure Drop Estimation (General Reference)

[ \Delta P = f \frac{L}{D} \frac{\rho v^2}{2} ]

• (f) = friction factor,

IS 15506 Key Points on Nozzle Placement and Performance

1. Nozzle Placement (Clause 11.4)

• Height:
  • Max height for single row: 3.5 m above floor.
  • If ceiling > 3.5 m, add extra nozzle row for uniform agent distribution.
  • Min height: 0.2 m above hazard floor level.
• Location:
  • Nozzles on ceiling within 0.5 m to 5 m from walls (no false ceiling).
  • Use deflector shields if false ceiling exists; locate to avoid damage from discharge or ceiling material dislodgement.
  • Provide nozzles in concealed spaces: floor voids, ceiling voids, etc.
• Number & Distribution:
  • Consider enclosure shape, volume, obstructions, pressure limits, and architectural features.
  • For suspended ceilings and raised floors, install nozzles in voids for simultaneous discharge to equalize pressure.

2. Pipe Size vs Flow Rate (Clause 11.3, Table 10)

3. **Performance & Pressure (Clause

IS 15506: Flow Calculations & Discharge Verification

Key Specifications:

• Hydraulic Calculations (Clause 12.1): Use approved methods to predict:

  • Pipe sizes
  • Nozzle pressure
  • Agent flow rate
  • Discharge per nozzle
  • Discharge time

• Discharge Time Accuracy (Clause 12.4): Predicted discharge time must match actual nozzle discharge time within ±5 seconds.

Pipe Size vs Flow Rate (Table 10, Clause 11.3)

Typical Flow Calculation Formula:

[ Q = A \times V ]

• (Q) = Flow rate (m³/s)
• (A) = Cross-sectional area of pipe (m²)
• (V) = Flow velocity (m/s)

Pressure losses and flow velocities must be balanced to avoid excessive pressure drops or low flow.

Summary Flow Verification Steps:

1. Select pipe size from Table 10 based on required flow.
2. Calculate flow and pressure losses using hydraulic formulas or software.
3. Verify nozzle discharge time matches predicted time ±5 s.
4. Adjust pipe sizing or nozzle specs if discrepancies occur.

IS 15506: Commissioning & Acceptance Testing - Key Points

1. Commissioning Certification (Clause 13.2)

• Upon completion, the installation agency must issue a test certificate confirming system commissioning.

2. Nozzle Pressure (Clause 12.6)

• Nozzle pressure must be maintained within min and max limits to ensure uniform agent distribution.

3. Acceptance Criteria (Clause 13.1)

• Commission per IS 15493.
• Prove system performance by:
  • (a) Full-scale discharge test (if required by authorities, follow Clause 14).
  • (b) Otherwise, follow alternative procedures.

4. Reporting Requirements (Clause 14.3)

Summary Diagram: Commissioning & Acceptance Flow

flowchart TD
    A[System Installation Complete] --> B[Commissioning per IS 15493]
    B --> C{Authority Requires Full-Scale Test?}
    C -- Yes --> D[Conduct Full-Scale Discharge Test (Clause 14)]
    C -- No --> E[Follow Alternative Acceptance Procedure]
    D & E --> F[Measure & Record Parameters (Clause 14.3)]
    F --> G[Issue Commissioning Certificate (Clause 13.2)]

Note: Always ensure nozzle pressure is within specified limits for effective agent distribution and uniform protection. Use IS 15493 for detailed commissioning procedures and testing methods.

IS 15506: Recommissioning Key Points

1. Recommissioning (Clause 14.2)

• Restore all fire suppression and associated systems to fully operational status after testing or maintenance.

2. Commissioning Certification (Clause 13.2)

• Installation agency must issue a test certificate upon completion of commissioning.

3. Venting Area Calculation (Clause 5.4)

• Venting area ( A ) required for IG55 gas discharge:

  [ A = Q \times \left(2 P\right)^{-0.5} ]

  Where:

  • ( A ) = venting area (m²)
  • ( Q ) = max IG55 flow (kg/s) = total weight / discharge duration (s)
  • ( P ) = max allowed overpressure (500 Pa)

4. Safety Concentration Limits (Table 6)

• Concentrations above LOAEL not permitted in occupied areas.

5. Safety Precautions (Table 5)

6. Reporting Requirements (Clause 14.3)

• System ID, temperature, residual gases, sampling points, date/time, discharge time, concentration at 2 & 10 min, system deficiencies, and reference to IS 15493.

flowchart TD
    A[System Maintenance] --> B[Recommissioning]
    B --> C[Restore Full Operation]
    C --> D[Issuance of Test Certificate]