Method of test for non-combustibility of building materials

IS 3808: Scope & Key Specifications

Scope (Clause 2.1)

• Covers test methods for assessing combustibility or non-combustibility of materials.
• Used by regulating authorities to classify materials based on fire performance.

Test Specimens (Clause 4.2)

• Five cylindrical specimens are prepared for testing.

Criteria for Evaluation (Clause 2.6.3)

• Average max furnace temperature rise ≤ 50°C above initial.
• Average max surface temperature rise ≤ 50°C above initial.
• Average max center temperature rise ≤ 50°C above initial.
• Average sustained flaming duration ≤ 20 seconds.
• Average mass loss ≤ 50% of original mass.

Units (SI)

flowchart TD
    A[Material Sample] --> B[Test Specimens]
    B --> C{Test Criteria}
    C -->|Temp Rise ≤ 50°C| D[Furnace, Surface, Center]
    C -->|Flaming ≤ 20s| E[Flaming Duration]
    C -->|Mass Loss ≤ 50%| F[Mass Measurement]
    D & E & F --> G[Classification: Combustible/Non-combustible]

This concise scope and criteria help standardize material fire safety evaluation as per IS 3808.

IS 3808: Apparatus Key Specifications & Formulas

Apparatus Components (Clause 2.1.1)

• Refractory tube surrounded by heating coils & insulation (the furnace)
• Air flow stabilizer at tube base
• Draught shield at tube top
  • Internal diameter: 75 mm
  • Height: 50 mm
  • Insulation thickness: 25 ± 2 mm (fibrous or suitable material) (Clause 2.4.2)
• Specimen holder with insertion device (Fig. 2)
• Three thermocouples (Fig. 3):
  1. Furnace thermocouple
  2. Specimen center thermocouple
  3. Specimen surface thermocouple
• Temperature recorder
• Stand for furnace
• Air flow shields

Calibration (Clause 3.1)

• Perform with specimen holder removed.
• Ensure uniform furnace wall temperature.
• Establish power input for tests.

Evaluation Criteria (Clause 2.6.3)

Thermocouple Type

• NiCr-Ni for specimen and furnace thermocouples.

Summary Diagram of Apparatus

graph TD
    A[Heating Coils + Insulation] --> B[Refractory Tube]
    B --> C[Air Flow Stabilizer (Base)]
    B --> D[Draught Shield (Top)]
    B --> E[Specimen Holder (Center)]
    E --> F[Specimen]
    B --> G[Thermocouples]
    G --> G1[Furnace TC]
    G --> G2[Center TC]
    G --> G3[Surface TC]
    B --> H[Air Flow Shields]

This setup ensures accurate, repeatable non-combustibility testing per IS

IS 3808: Furnace and Temperature Control - Key Points

Furnace Design & Temperature Control (Clauses 2.2, 3.3, 3.4)

• Furnace Construction:

  • Use closer winding or separate windings at tube ends for controlled temperature zones (Clause 3.3).
  • Voltage stabilizer is essential to maintain power input within ±1% of calibration power for test accuracy.
  • Avoid automatic thermostatic control during tests (Clause 3.4).

• Temperature Stability:

  • Furnace wall temperature must return to steady state before next test.
  • Minimize ambient condition fluctuations near apparatus.

Temperature Measurement (Clause 2.7.1)

• Use continuous recorder for furnace and surface thermocouples.
• Measuring range must cover temperature changes during tests.
• Record center thermocouple readings at intervals ≤ 5 seconds.

Summary Table: Temperature Control Requirements

Conceptual Diagram: Furnace Temperature Control Setup

flowchart LR
    A[Furnace with Separate Windings] --> B[Voltage Stabilizer]
    B --> C[Furnace Power Input ±1% Stability]
    C --> D[Temperature Sensors (Thermocouples)]
    D --> E[Continuous Recorder (≤5s interval)]
    F[Ambient Conditions] -.->|Minimize Variations| A

This ensures precise thermal conditions for accurate testing as per IS 3808.

IS 3808: Test Specimens - Key Specifications & Formulas

1. Specimen Dimensions (Clause 4.2)

• Number of specimens: 5 cylindrical specimens per test.
• Specimens must represent the average properties of the sample (Clause 4.1).

2. Preparation (Clause 4.1)

• If material thickness < 50 mm, stack layers horizontally with fine wire to minimize air gaps.
• For composites with insufficient layers, adjust component thicknesses to achieve 50 mm height.
• Top and bottom faces must be finished faces of the material.
• Specimen density must represent the material density.

3. Conditioning (Clause 4.3)

• Condition specimens in a ventilated oven at 60 ± 5°C for ≥ 20 hours.
• Cool in a desiccator with drying agent before testing.
• Record specimen mass before furnace test.

Volume Check Formula for Cylinder

[ V = \pi \times \left(\frac{d}{2}\right)^2 \times h ]

Where:

• (d =) diameter (mm)
• (h =) height (mm)
• (V =) volume (mm³ or convert to cm³ by dividing by 1000)

flowchart LR
    A[Material Sample] --> B[Prepare 5 Cylindrical Specimens]
    B --> C{Thickness < 50 mm?}
    C -- Yes --> D[Stack layers horizontally with wire]
    C -- No --> E[Use single piece]
    D & E --> F[Condition at 60 ± 5°C for ≥ 20h]
    F --> G[Cool in desiccator]
    G --> H[Measure mass]
    H --> I[Test specimens]

This ensures uniformity and representativeness of test specimens per IS 3808.

IS 3808: Test Procedure Key Points

1. Test Specimens (Clause 4.2)

• Number: 5 cylindrical specimens
• Dimensions:

2. Conditioning (Clause 4.3)

• Oven temperature: 60 ± 5℃
• Duration: ≥ 20 hours
• Cooling: In desiccator with drying agent
• Mass measured before test

3. Test Setup (Clause 3.4)

• No automatic thermostatic control of furnace during test

4. Temperature Measurements (Clause 6.1.1)

Record the following:

• Initial furnace temperature: T₀
• Maximum furnace thermocouple temperature: Tᵣ
• Maximum surface thermocouple temperature: Tₛ
• Maximum centre thermocouple temperature: T𝚌
• Duration of sustained flaming

Summary Diagram

flowchart TD
    A[Test Specimen Preparation] --> B[Conditioning at 60±5℃ for 20h]
    B --> C[Cooling in Desiccator]
    C --> D[Mass Measurement]
    D --> E[Test in Furnace (No auto control)]
    E --> F[Record Temperatures: T₀, Tᵣ, Tₛ, T𝚌]
    F --> G[Measure Flaming Duration]

This procedure ensures repeatability and reliability in testing thermal properties per IS 3808.

IS 3808: Expression of Test Results - Key Points

• Rounding Off:
  Final test values must be rounded as per IS 2:1960 (Rules for rounding off numerical values).

• Reported Results (Clause 6.1):
  Essential results to note and report include:

  • Physical and mechanical properties tested
  • Observations on specimen behavior (Clause 5.4.3)
  • Any other relevant data as per Appendix A (criteria for evaluation)

• Test Report Contents (Clause 7.1):
  The report must include:

  • Manufacturer/supplier name
  • Product identification
  • Material description
  • Material density
  • Supply and test dates
  • Specimen description
  • Test method used
  • Test results (as per Clause 6)
  • Testing laboratory name

Rounding Off Example (IS 2:1960)

flowchart TD
    A[Test Specimen] --> B[Conduct Test]
    B --> C[Record Observations]
    C --> D[Calculate Results]
    D --> E[Round off (IS 2:1960)]
    E --> F[Prepare Test Report]
    F --> G[Include Details per Clause 7.1]

This ensures clarity, traceability, and standardization in reporting test outcomes.

IS 3808: Key Formulas, Tables & Specifications (Appendices & Guidance)

1. Criteria for Evaluation of Performance (Clause 2.6.3 & Appendix A)

Note: Regulating authority decides applicable criteria.

2. Test Specimen Dimensions (Clause 4.2)

3. SI Units Relevant to Testing

4. Reporting Requirements (Clause 6.1 & 5.4.3)

• Record all thermocouple readings, flaming duration, and mass loss.
• Note any additional specimen behavior observations.
• Evaluate results per Appendix A criteria.

flowchart TD
    A[Test Specimen Preparation] --> B[Conduct Test]
    B --> C[Record Thermocouple Readings]
    B --> D[Measure Flaming Duration]
    B --> E[Calculate Mass Loss]
    C & D & E --> F[Evaluate Criteria A1 to A5]
    F --> G[Report Results]