Gaseous Fire Extinguishing Systems - HFC 227ea (Hepta Fluoro Propane) Extinguishing Systems

IS 15517: Scope - Key Formulas, Tables & Specifications

1. Enclosure Volume Calculations (Clause 7.3)

• Net Maximum Volume: [ V_{Max} = V - V_s ]
• Net Minimum Volume: [ V_{Min} = V_{Max} - V_o ] Where:
  • (V) = Gross enclosure volume (m³)
  • (V_s) = Volume of permanent structural objects impermeable to gas (m³)
  • (V_o) = Volume of occupancy-related objects impermeable to gas (m³) (ignored if < 25% of (V_{Max}))

2. Design Concentration of HFC 227ea (Clause 8 & Table 10)

• Minimum design concentration depends on fire type, e.g.,
  • Class A surface fires: minimum 7.0% by volume
  • Flammable liquids/gases vary (e.g., Ethanol 7.6%, Methane 8.0%)
• Safety factor of 1.2 applied to extinguishing concentration
• Design concentration must not be less than 7.5% by volume

3. Pipe Sizing Guide (Clause 12.3 & Table 14)

• Proper pipe diameter balances pressure loss and flow velocity
• Example sizes vs. flow rates:

Key Formulas and Tables from IS 15517 for HFC 227ea Fire Suppression Systems

1. Enclosure Volume Calculations (Clause 7.3)

• Maximum Net Volume: [ V_{Max} = V - V_s ]
• Minimum Net Volume: [ V_{Min} = V_{Max} - V_o ]

Where:

• (V) = 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 (ignore if < 25% of (V_{Max}))

2. Design Concentration of HFC 227ea (Clause 8 & Table 10)

• Minimum design concentration includes a 20% safety factor and must not be less than 7.5%.

3. HFC 227ea Specific Vapor Volume & Total Flooding Quantity (Table 9)

• Specific vapor volume varies with temperature (m³/kg).
• Total flooding quantity depends on design concentration (%) and temperature.

4. Pipe Sizing Guide (Clause 12.3, Table 14)

IS 15517: Key Formulas, Tables & Specifications for Application of HFC 227ea Fire Suppression System

1. Design Concentration (Clause 8)

• Minimum design concentration depends on fuel type and hazard class.
• For Class A surface fires, use extinguishing concentration + 20% safety factor.

2. Enclosure Volume Calculation (Clause 7.3)

[ \begin{align*} V_{Max} &= V - V_s \ V_{Min} &= V_{Max} - V_o \end{align*} ]

• (V) = 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)

3. Agent Quantity (Clause 7.2 & Table 9)

• Use specific vapor volume and design concentration to find total agent kg/m³.

Example from Table 9 (at 20°C):

4. Atmospheric Correction Factor (Clause 8f & g)

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

• (N_1): Adjusted number of containers
• (N): Initial number of containers
• Correction factor depends on

IS 15517: Gas Characteristics and Properties of HFC 227ea

1. Chemical Composition (Clause 4.3, Table 1)

• Chemical Name: Hepta Fluoro Propane
• Chemical Formula: HFC 227ea (C3HF7)

2. Physical Properties (Clause 4.6, Table 3)

3. Gas Purity Specifications (Clause 4.5, Table 2)

4. Nitrogen Pre-Pressurization (Clause 2.5, Table 6)

• Used to increase flow pressure in pipelines.
• Common pressures: 2.5 MPa and 4.2 MPa at 20°C.
• Nitrogen dissolves partially in HFC 227ea, increasing total pressure.

| Fill Density (kg/m³) | Final Pressure @ 4.2 MPa System (bar

Safety of Personnel - IS 15517 (Clause 5)

Key Points & Specifications:

• Hazards considered:

  • Extinguishant (HFC 227ea) itself
  • Fire combustion products
  • Breakdown products of extinguishant

• Specific Vapour Volume (S) of superheated HFC 227ea vapour at 100 kPa absolute:

  [ S = 0.12632 + 0.000514 \times t \quad (m^3/kg) ]

  where t = temperature in °C

Safety Concentration Limits (Table 8):

• Design Note:
  • Concentrations above LOAEL (10.5%) allowed only in normally unoccupied areas.
  • Concentrations below NOAEL (9%) are safe for occupied areas.

Minimum Safety Precautions (Table 7):

Summary:

• Ensure maximum concentration ≤ NOAEL (9%) in occupied areas.
• For total flooding in unoccupied areas, concentrations can exceed LOAEL but with strict safety interlocks and no requirement for egress.
• Use inhibit switches and time delays to prevent accidental discharge.
• Design system volume carefully to avoid exceeding safe concentrations.

flowchart TD
    A[Start: Design System] --> B{Occupied Area?}
    B -- Yes --> C[Max Conc. ≤ 9% (NOAEL)]
    C --> D[Inhibit Switch & Time Delay Required]
    D --> E[No Egress or Lock

IS 15517: Enclosure Strength & Venting Facilities - Key Points

1. Enclosure Strength & Venting (Clause 6)

• Venting should be provided at the highest possible levels.
• Enclosure strength and allowable pressure must follow guidelines ensuring structural safety under gas discharge pressure.
• Free venting requirements depend on enclosure type and can be calculated per relevant specs.

2. Enclosure Volume Calculation (Clause 7.3)

• Net enclosure volume: [ V_{Max} = V - V_s ] [ V_{Min} = V_{Max} - V_o ] where:
  • (V) = gross enclosure volume (m³)
  • (V_s) = volume of permanent objects impermeable to gas (m³)
  • (V_o) = volume of occupancy-related objects impermeable to gas (ignored if < 25% of (V_{Max}))

3. Design Concentration of HFC 227ea (Clause 8)

• Minimum design concentration for Class A surface fires: 7.5% by volume (with safety factors).
• Concentration must be uniform throughout the enclosure.
• Adjust agent quantity for altitude using atmospheric correction factors (Table 13):

4. Discharge Time (Clause 10.3)

• Time to discharge 90% of agent mass at 21°C to reach design concentration should be ≤ 10 seconds.

Summary Table: Minimum Design Concentrations for Common Materials (Vol %)

Key Formulas and Tables for Extinguishing Agent Supply (IS 15517)

1. Total Flooding Quantity (Clause 7.2a)

Calculate the HFC 227ea agent mass ( M ) as:

[ M = \frac{S \times V \times (100 - C)}{100} ]

Where:

• ( M ) = total flooding quantity (kg)
• ( C ) = design concentration (% by volume)
• ( V ) = net volume of hazard (m³)
• ( S = K_1 + K_2 \times T ) (temperature-dependent factor)
• ( K_1 = 0.1269 ), ( K_2 = 0.0005 ) (constants for HFC 227ea)
• ( T ) = minimum enclosure temperature (°C)

2. Design Concentration (Table 10) for Flame Extinguishment

• Minimum design concentration shall not be less than 7.5% in any case.
• Apply a 30% safety factor on extinguishing concentration for Class B fuels.

3. Atmospheric Correction Factor (Clause 7.5f & 7.5g)

Adjust agent quantity for altitude:

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

Where:

• ( N_1 ) = adjusted number of containers
• ( N ) = initial number of containers

Correction factor is ratio of average ambient pressure at site to standard sea level pressure (from Table 13).

4. Retention Time (Clause 9)

• Concentration at 1 m above floor or top of enclosure must be

IS 15517: Design Concentration Key Points & Formulas

1. Design Concentration (Clause 7.5 & 8)

• Minimum design concentration for HFC 227ea agent depends on hazard type:

• For mixed fuels, use the highest required concentration from Table 10 or 11.

2. Total Flooding Quantity (Clause 7.2)

[ M = \frac{S \times V \times 100}{100 - C} ]

Where:

• (M) = total agent quantity (kg)
• (C) = design concentration (% vol)
• (V) = net enclosure volume (m³)
• (S = K_1 + K_2 \times T) (temperature correction)
• Constants for HFC 227ea: (K_1 = 0.1269), (K_2 = 0.0005)
• (T) = minimum enclosure temperature (°C)

3. Agent Quantity per Volume (Table 9 excerpt)

Use the table for exact agent mass per volume based on temperature and concentration.

4. Atmospheric Correction (Clause 7.5(f), (g))

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

• Adjust agent quantity for altitude using Table 13 atmospheric correction factors.
• (N_1) = adjusted number of containers
• (N\

IS 15517: Post Discharge Scenario - Key Formulas, Tables & Specs

1. Post Discharge Concentration Requirements (Clause 9)

• Within 1 min of discharge:
  Concentration at 1 m above floor or top of highest hazard must be within ±1% of design concentration.

• At 10 min (Retention time):
  Concentration ≥ 80% of design concentration.

2. Minimum Design Concentration for HFC 227ea (Table 10)

3. Adjustment for Altitude (Clause 8f & 8g)

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

• (N_1): Adjusted number of HFC 227ea containers
• (N): Initial number of containers
• Correction factor from Table 13 based on altitude (ratio of ambient pressure to sea level pressure).

4. Enclosure Volume Calculation (Clause 7.3)

[ V_{Max} = V - V_s ]

[ V_{Min} = V_{Max} - V_o ]

• (V): Gross enclosure volume (m³)
• (V_s): Volume of structural/permanent objects (non-permeable) (m³)
• (V_o): Volume of occupancy-related objects (non-permeable) (m³)

5. Total Flooding Quantity (Table 9)

• Gives kg/m³ of HFC 227ea required for various temperatures and design concentrations (6% to 12%).

Summary Diagram: Post Discharge Concentration Timeline

IS 15517 Key Points on Application Rate, Duration & Discharge Time

1. Design Application Rate (Clause 10.1)

• Based on the quantity of HFC 227ea agent (M) and required discharge duration.

• Agent quantity adjusted for elevation using:

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

  where:

  • (N_1) = adjusted number of containers
  • (N) = initial number of containers

• Atmospheric correction factors per Table 13 adjust for altitude effects.

2. Duration of Discharge & Retention Time (Clause 9)

• Within 1 min of discharge start, concentration at 1 m above floor/top must be within ±1% of design concentration.
• At 10 min (or as required), concentration must be ≥ 80% of design concentration (retention time).

3. Discharge Time & Flow Rate (Clause 12.3 & 13.1)

• Use approved hydraulic calculation methods to predict:

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

• Pipe sizing guide (Table 14):

IS 15517: Distribution System Key Specifications & Formulas

1. Pipe Sizing (Clause 12.3, Table 14)

• Pipe size selection balances pressure loss and flow velocity in two-phase flow.
• Use Table 14 for nominal pipe size vs. design flow rate (kg):

• Verify sizing with flow calculation software.

2. Percent in Distribution System (Clause 13.10)

• Percent-in-pipe = ratio of pipe volume to expanded HFC 227ea volume during flow.
• Typical percent-in-pipe = 45% of total pipe volume.
• Ensures average container pressure during discharge is maintained.

3. Container Pressure (Clause 2.5)

• Containers superpressurized with nitrogen to:
  • 2.5 MPa ± 5% or 4.2 MPa ± 5% at 21 ± 1ºC.
• Pressure/temperature chart attached for monitoring.

4. Enclosure Volume Calculation (Clause 7.3)

• ( V_{Max} = V - V_s )
• ( V_{Min} = V_{Max} - V_o )

Where:

• ( V ) =

IS 15517: Hydraulic Calculations & Flow Characteristics Key Points

1. Pipe Sizing (Clause 12.3 & Table 14)

• Pipe sizing balances pressure loss and flow velocity in two-phase flow.
• Use Table 14 as a guide for nominal pipe size vs. design flow rate (kg/min):

• Final sizing should be verified by approved hydraulic calculation software.

2. Hydraulic Calculation Accuracy (Clause 13.1)

• Predicted agent weight discharge: within -5% to +10% of actual.
• Discharge time prediction must match actual.
• Nozzle pressure must stay within specified min/max for uniform agent distribution.

3. Enclosure Volume Calculations (Clause 7.3)

• Net volume for agent calculation:

[ V_{Max} = V - V_s ]

[ V_{Min} = V_{Max} - V_o ]

Where:

• (V) = gross enclosure volume (m³)
• (V_s) = volume of permanent objects impermeable to gas (m³)
• (V_o) = volume of occupancy-related objects impermeable to gas (ignore if <25% of (V_{Max}))

4. Design Concentration of HFC 227ea (Clause 8 & Table 9)

• Design concentration depends on combustibles and enclosure.
• Minimum design concentration for Class A fires = extinguishing concentration × 1.2 safety factor.
• Use Table 9 for specific vapor volume and concentration at different temperatures.

Summary Diagram: Hydraulic Calculation Flow

flowchart TD
    A[Determine Enclosure Volume] --> B[Calculate Net Volume Vmax & Vmin]
    B --> C[Select Nominal Pipe Size from Table 14]
    C --> D[Perform Hydraulic Calcul

IS 15517: System Testing and Recommissioning - Key Points

1. System Testing Reporting (Clause 14.4)

Report must include:

• System Identification:

  • Installation, designer, contractor
  • Enclosure IDs
  • Enclosure temperature before discharge
  • Oxygen & CO₂ residual concentrations
  • Sampling point positions

• Test Details:

  • Date & time
  • Discharge time
  • Concentration levels at each sampling point at 1 and 10 minutes after discharge start
  • System deficiencies noted

2. Purity of HFC 227ea (Annex A, Table 2)

• Determined by Gas Chromatograph with Thermal Conductivity Detector (TCD).
• Use standard chromatograph graph (Fig. 4) for purity percentage.
• Purity affects system performance and safety.

3. Discharge Test Procedure (Annex B, Clause 9)

• Discharge test performed only if legally required; otherwise, do enclosure integrity test.
• Measure:
  • Discharge time (must meet design criteria)
  • Concentration at specified heights and times (1 min, 10 min)
• Ensures compliance with total flooding system requirements.

4. Recommissioning (Clause 14.3)

• Restore system to fully operational status after testing or maintenance.

5. Additional Notes on System Types (Clause 13.11)

Summary Table: Key Parameters for Testing

flowchart TD

IS 15517: Determination of Purity of HFC 227ea

Key Specifications (Table 2)

Physical Properties (Table 3)

• Molecular weight: 170
• Boiling point: -16.4°C
• Vapour pressure at 20°C: 0.391 MPa
• Liquid density at 20°C: 1407 kg/m³

Purity Calculation (Clause 5.1)

Purity is determined by gas chromatography (GC):

[ \text{Percent HFC 227ea} = \frac{\sum \text{area of all peaks excluding nitrogen peak}}{\text{total area}} \times 100 ]

This means summing the chromatogram peak areas of all HFC 227ea components except nitrogen, then expressing as a percentage.

Summary Diagram (Purity Determination Process)

flowchart LR
    A[Sample Injection] --> B[Gas Chromatograph]
    B --> C[Chromatogram Peaks]
    C --> D[Exclude Nitrogen Peak]
    D --> E[Sum Remaining Peak Areas]
    E --> F[Calculate % Purity]

This ensures compliance with IS 15517 purity criteria for HFC 227ea gas.

IS 15517: Test Procedures - Key Formulas, Tables & Specifications

1. Test Reporting Requirements (Clause 14.4)

• Identify system: installation, designer, contractor, enclosure ID
• Enclosure temperature before discharge
• Oxygen & CO₂ residual concentrations
• Sampling points location
• Date/time of test, discharge time
• Concentration at sampling points at 1 & 10 min after discharge start
• Note system deficiencies

2. Purity Determination of HFC 227ea (Annex A)

• Use Gas Chromatograph with Thermal Conductivity Detector (TCD)
• Purity % determined by comparing chromatograph output with standard graph (Fig. 4)

3. Discharge Test Procedure (Annex B)

• Discharge time measured; concentration readings taken at specified heights and times
• Concentration at 1 min: within ±1% of design concentration
• At 10 min: ≥ 80% of design concentration (retention time)

4. Design Concentration (Table 10)

5. Adjustment for Altitude (Clause 8(g))

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

• (N_1) = adjusted number of containers
• (N) = initial number of containers
• Correction factor from Table 13 based on altitude (ratio of actual pressure to sea level pressure)

6. Summary Flow of Test Procedure

flowchart TD
    A[Start Test] --> B[Record system info & enclosure temp]
    B --> C[Measure O₂ & CO₂ residuals]
    C --> D[Discharge system & record discharge time]
    D --> E[Measure concentration at