Gaseous Fire Extinguishing Systems - HCFC Blend A Extinguishing Systems

IS 15505 Key Specifications & Tables for Scope

1. Atmospheric Correction Factors (Clause 7.3, Table 8)

Use correction factor to adjust gas quantities for altitude.

2. Total Flooding Quantity of HCFC Blend A (Clause 7.3, Table 6)

• Mass requirement per m³ depends on temperature (°C) and design concentration (%).
• Specific vapor volume (m³/kg) varies with temperature.
• Example: At 25°C and 10% concentration, mass = 0.376 kg/m³.

3. Pipe Sizing for HCFC Blend A (Clause 4.2, Table 9)

4. Composition of HCFC Blend A (Clause 4.3, Table 1)

IS 15505 Key References:

1. Atmospheric Correction Factors (Clause 7.3, Table 8)

Adjust gas quantities for elevation using:

2. Total Flooding Quantity (Clause 7.3, Table 6)

Mass of HCFC Blend A required per m³ depends on temperature and design concentration (% volume):

3. Composition of HCFC Blend A (Clause 4.3, Table 1)

Formula to adjust quantity for altitude:

[ Q_{alt} = Q_{sea} \times \text{Atmospheric Correction

IS 15505: General Information Key Tables & Formulas

1. Atmospheric Correction Factors (Clause 7.3, Table 8)

Use correction factor to adjust gas quantities for altitude.

2. Total Flooding Quantity for HCFC Blend A (Clause 7.3, Table 6)

• Mass requirement (kg/m³) depends on temperature (°C) and design concentration (%).
• Example at 25°C and 10% concentration: 0.376 kg/m³.
• Specific vapor volume (m³/kg) also tabulated.

3. Pipe Sizing vs Flow Rate (Clause 4.2, Table 9)

Select pipe size based on flow and pipe length.

4. HCFC Blend A Composition (Clause 4.3, Table 1)

IS 15505: Key Gas Characteristics & Properties for HCFC Blend A

Physical Properties (Table 3, Clause 4.6)

Important Specifications (Clause 99.6)

• Purity: ≥ 99.6% by mass
• Non-volatile residue: ≤ 0.01% by mass
• Suspended matter or sediment: ≤ 3 x 10⁻⁶ by mass

Total Flooding Quantity (Clause 7.3, Table 6)

• Mass of HCFC Blend A per m³ of protected space varies with temperature and design concentration.
• Specific vapor volume (S) decreases with temperature rise.
• Example: At 20 °C and 10% concentration, mass = 0.429 kg/m³.

Pipe Sizing (Clause 4.2, Table 9)

• Flow rates (kg/s) for nominal bore sizes (mm) depend on pipe length.
• Example: For 25 mm pipe, flow rate up to 5 m = 4.0 kg/s.

Formula for Mass Requirement:

[ m = \frac{C \times \rho_{air}}{(1 - C)} ] Where:

• (m) = mass of HCFC blend per m³ (kg/m³)
• (C) = design concentration by volume (decimal)
• (\rho_{air}) = density of air (~1.2 kg/m³)

IS 15505: Safety of Personnel - Key Points

1. Safety Considerations (Clause 5.1)

• Any hazard to personnel from HCFC blend A discharge must be considered during design.
• Toxicological limits (Table 4) guide safe exposure:
  • NOAEL (No Observed Adverse Effect Level): 10% volume
  • LOAEL (Lowest Observed Adverse Effect Level): >10% volume
  • 4-hour LC50 (Lethal Concentration): 64% volume

2. Atmospheric Correction Factors (Clause 7.3, Table 8)

Adjust design concentration for altitude using:

Formula:

[ C_{corrected} = C_{design} \times A ]

Where:

• (C_{design}) = Design concentration at sea level
• (A) = Atmospheric correction factor from Table 8

3. Total Flooding Quantity (Clause 7.3, Table 6)

Mass of HCFC Blend A required per m³ depends on temperature and design concentration:

Summary:

• Use toxicological limits to ensure personnel safety.
• Adjust design concentration for altitude using atmospheric correction factors.
• Calculate total mass of HCFC Blend A using temperature-dependent tables.

flowchart LR
   

IS 15505: Key Formulas, Tables & Specifications for System Components

1. Enclosure Volume Calculation (Clause 7.3.1)

• Maximum Net Volume: [ V_{\text{Max}} = V - V_s ]

  • (V) = Gross enclosure volume (m³)
  • (V_s) = Volume of permanent objects impermeable to gas (m³)

• Minimum Net Volume: [ V_{\text{Min}} = V_{\text{Max}} - V_o ]

  • (V_o) = Volume of occupancy-related objects impermeable to gas (ignore if < 25% of (V_{\text{Max}}))

2. Atmospheric Correction Factors (Table 8, Clause 7.3 & 8(g))

Use these factors to adjust gas quantities for elevation.

3. Total Flooding Quantity for HCFC Blend A (Table 6, Clause 7.3)

• Mass requirement per unit volume (kg/m³) depends on temperature and design concentration (%).
• Example at 0°C:

4. Pipe Sizing vs Flow Rate (Table 9, Clause 11.3)

Key Formulas & Tables for Design Concentration and Quantity Requirements (IS 15505)

1. Total Flooding Quantity Calculation (Clause 7.2)

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

Where:

• M = Total HCFC Blend A quantity (kg)
• V = Net volume of hazard (m³)
• C = Design concentration (% by volume)
• S = Specific vapour volume (m³/kg) = (K_1 + K_2 \times T)
• (K_1 = 0.2413), (K_2 = 0.00088) (Constants for HCFC Blend A)
• T = Minimum temperature inside enclosure (°C)

2. Atmospheric Correction Factor (Clause 7.3 & Table 8)

Adjust agent quantity for altitude:

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

• (N_1) = Adjusted number of containers
• (N) = Initial number of containers

3. Design Concentration for Inerting (Table 7, Clause 8.6)

IS 15505 Key Points: Application Rate & Discharge Time

1. Design Application Rate (Clause 9.1)

• Based on the quantity of HCFC blend A (MA) required.
• Depends on the duration of discharge (Clause 9.2).

2. Discharge Time (Clause 9.3)

• Time from valve actuation or liquid appearance at nozzle until mostly gaseous discharge.
• Defined as time to discharge 90% of agent mass at 21°C to achieve minimum design concentration + 20% safety factor.
• Must not exceed 10 seconds to reach 95% of minimum design concentration.
• Use flow calculations (Clause 12) or approved pre-engineered systems to verify.

3. Flow Calculation Parameters (Clause 12.1)

• Predict pipe sizes, nozzle pressure, agent flow rate, discharge per nozzle, and discharge time.
• Accuracy limits:
  • Agent weight discharged: within -5% to +10% of predicted.
  • Discharge time: predicted vs actual must agree.
  • Nozzle pressure must stay within min/max limits for uniform agent distribution.

4. Atmospheric Correction Factor (Table 8, Clause 7.3)

Use correction factor to adjust agent quantity and discharge parameters for altitude.

Summary Formula for Discharge Time:

[ t_{discharge} \leq 10 \text{ s for } 95% \text{ design concentration} ]

flowchart LR
    A[Start Valve Actuation] --> B[Liquid Discharge at Nozzle]
    B --> C{Discharge Time}
    C -->|90% Agent Mass| D[Minimum

IS 15505: Key Specifications and Tables for HCFC Blend A Storage Containers

1. Pressure-Temperature Indication (Clause 10.1.6)

• Storage containers must have reliable means to indicate pressure variation with temperature.
• Acceptable: Attach a Pressure/Temperature chart (see Fig. 3 in IS 15505).

2. Storage Container Characteristics (Clause 2.5, Table 4.9)

3. Total Flooding Quantity (Clause 7.3, Table 7.2)

• Mass of HCFC Blend A required per m³ of protected space depends on temperature and design concentration.
• Example values at 20°C:

• Use specific vapor volume (S) and design concentration (C) to calculate mass:

[ \text{Mass} = \frac{C \times 1}{S} ]

Where:

• (C) = design concentration (volume %)
• (S) = specific vapor volume (m³/kg) from table at given temperature

Summary

• Containers must display a pressure/temperature chart.
• Design pressures and fill densities are standardized.
• Use Table 7.2 for mass requirements based on temperature and concentration.
• Refer to IS 15493 for additional container requirements.

flowchart LR
  A[Temperature] --> B[Pressure in Container]
  B --> C[Pressure/Temperature Chart]
  C --> D[Safe Storage Container Design]
  A --> E[Specific Vapor Volume (S)]
  E --> F[Calculate Mass Required

IS 15505 - Distribution System Key Data

1. Atmospheric Correction Factors (Clause 7.3, Table 8)

Used to adjust design concentration based on altitude and pressure.

2. Pipe Sizing for HCFC Blend A (Clause 11.3, Table 9)

Select pipe diameter based on flow rate and pipeline length to balance pressure loss and flow velocity.

3. Important Notes

• Distribution system must comply with IS 15493 alongside IS 15505.
• Authorities' regulations may override IS 15505 if more stringent (Clause 10.1.7).
• Two-phase flow complicates sizing; use approved flow calculation software for accuracy.

Summary Diagram: Pipe Sizing Decision Flow

flowchart TD
    A[Determine Flow Rate & Distance] --> B{Distance}
    B -->|>10 m| C

Hydraulics of the System — IS 15505 Key Points

1. Atmospheric Correction Factor (Clause 7.3, Table 8)

Used to adjust for altitude effects on pressure and concentration:

2. Pipe Sizing (Clause 11.3, Table 9)

Guidance for pipe diameter vs flow rate (kg/s) depending on pipe length:

3. Hydraulic Calculation Accuracy (Clause 12.1)

• Predicted agent weight discharge: within -5% to +10% of actual.
• Discharge time prediction matches actual.
• Nozzle pressure within acceptable operating range.
• Nozzle pressure must ensure uniform agent distribution.

Summary Formula for Flow Rate Estimation

• Use pipe diameter and length with flow rate tables.
• Adjust flow rates by atmospheric correction factor for altitude.
• Validate with hydraulic flow calculation software.

flowchart TD
    A[Agent Storage] --> B[Pipe Sizing]
    B --> C{Pipe Diameter}
    C -->|Small| D[High Pressure Loss]
    C -->|Large| E[Low Velocity, Pressure Drop]
   

IS 15505: Engineered & Pre-engineered Systems Key Points

1. System Types (Clause 12.3)

• Engineered Systems:

  • Central large storage containers manifolded together.
  • Single pipe feeds nozzles inside hazard area.
  • Requires complex flow calculations for HCFC blend A & nitrogen phases considering enclosure volume and pressure losses.

• Pre-engineered Systems:

  • Single container with max two nozzles and small piping.
  • Modular units multiplied for larger areas.

2. Total Flooding Quantity (Clause 7.2, Table 6)

• Mass of HCFC Blend A per m³ depends on temperature and design concentration (7%-16%).
• Use Specific Vapour Volume (S) and design concentration (C%) to find mass:

[ \text{Mass} = \frac{C \times \text{Enclosure Volume}}{S} ]

• Example: At 25°C and 10% concentration, mass = 0.376 kg/m³.

3. Atmospheric Correction Factor (Clause 7.3, Table 8)

• Adjust mass quantity based on altitude:
  [ \text{Adjusted Mass} = \text{Mass} \times \text{Correction Factor} ]

4. Pipe Sizing (Clause 11.3, Table 9)

• Select pipe size based on flow rate and length to minimize pressure loss.

5. Post Discharge Requirements (Clause 13)

• Concentration

Post Discharge Scenario - IS 15505 Key Points (Clause 13)

• Concentration Stability:

  • Within 1 minute of discharge start, concentration at 1 m above floor or top of hazard must be within ±1% of design concentration.

• Retention Time:

  • At 10 minutes post-discharge (or as required), concentration at the same levels must be at least 80% of the design concentration.

Relevant Tables & Formulas

Atmospheric Correction Factor (Table 8):

Used to adjust gas quantity for elevation.

Total Flooding Quantity (Table 6 excerpt):

Summary Formula for Required Mass (m):

[ m = V \times C \times \frac{1}{S} \times \text{Atmospheric Correction Factor} ]

Where:

• (V) = Enclosure volume (m³)
• (C) = Design concentration (volume %)
• (S) = Specific vapour volume (m³/kg) from Table 6
• Atmospheric Correction Factor from Table 8

This ensures correct gas quantity and retention after discharge for effective hazard suppression.

IS 15505: Commissioning & Acceptance Testing Key Points

1. Acceptance Criteria (Clause 14.1)

• Commission HCFC blend A total flooding system per IS 15493.
• System performance must be proven.

2. Atmospheric Correction Factor (Table 8, Clause 7.3 & 8(g))

Formula for container adjustment:

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

• (N_1): Adjusted number of containers
• (N): Initial number of containers

3. Design Concentration for Inerting (Table 7, Clause 8(e))

• Use 30% safety factor for flame extinguishment concentration.
• Use 10% safety factor for inerting concentration.
• Minimum design concentration shall not be less than 8.6%.

4. Post Discharge Requirements (Clause 13)

• Within 1 min, concentration variation ≤ ±1% of design concentration at 1m above floor.
• At 10 min, concentration ≥ 80% of design concentration (retention time).

flowchart TD
    A[Start Commissioning] --> B[Verify Design Concentration]
    B