Tests on electric cables under fire conditions - Part 3-24: Test for vertical flame spread of vertically-mounted bunched wires or cables - Category C

1 Scope
The series of International Standards covered by Parts 3-10, 3-21, 3-22, 3-23, 3-24 and 3-25 of IEC 60332 specifies methods of test for the assessment of vertical flame spread of verticallymounted bunched wires or cables, electrical or optical, under defined conditions. NOTE For the purpose of this standard, the term 'electric wire or cable' covers all insulated metallic conductor cables used for the conveyance of energy or signals.

The test is intended for type approval testing. The requirements for the selection of cables for testing are given in annex A. The flame spread is measured as the extent of damage of the cable sample. This procedure may be used to demonstrate the cable's ability to limit flame spread. This part of IEC 60332 covers category C and relates to cables installed on the test ladder to achieve a nominal total volume of non-metallic material of 1,5 l per metre of test sample. The
flame application time is 20 min. The method of mounting uses the front of the standard ladder. The category is intended for general use where low volumes of non-metallic material are required to be evaluated. A recommended performance requirement is given in annex B.

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1. Overview
This standard outlines the procedure for testing the **vertical flame spread** of bunched wires or cables under fire conditions. It is part of the series that evaluates cable performance in fire scenarios and ensures compliance with safety requirements.

Category C: This category applies to vertically-mounted bunched wires or cables exposed to a flame source under specified conditions.

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2. Purpose of the Test
The test assesses:

• Flame Spread Control: Measures how far the flame propagates along the cable bundle.
• Fire Performance of Cables: Evaluates the ability of cables to limit fire spread in vertical installations.
• Safety Assurance: Ensures compliance with fire safety standards for buildings and industrial facilities.

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3. Test Setup
The following elements are required for the test:

• Test Chamber:
  - A vertically enclosed test chamber with controlled ventilation to simulate real-world fire conditions.
  - Dimensions and airflow must meet the standard's specifications.
• Cable Mounting:
  - Wires or cables are bundled and mounted vertically on a ladder-type rack or tray.
  - The number and arrangement of cables depend on the cross-sectional area and design.
• Flame Source:
  - A **standardized burner** producing a flame with a heat output of **20.5 kW (±10%)**.
  - Flame application duration is **20 minutes**.
• Measurement Markings:
  - Mark the cables at specified intervals to measure flame spread.

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4. Test Procedure
The procedure involves the following steps:

• a. Preconditioning:
  - Condition the cables at room temperature for at least **24 hours** before the test.
• b. Flame Application:
  - Ignite the burner and apply the flame to the bottom of the cable bundle for **20 minutes**.
• c. Observations During the Test:
  - Record flame behavior, dripping, and the spread of combustion along the cable.
• d. Post-Test Evaluation:
  - Measure the distance of vertical flame spread from the point of ignition.
  - Inspect the cables for material degradation and damage.

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5. Performance Criteria
The cables pass the test if:

• The vertical flame spread does not exceed **2.5 meters** from the point of ignition.
• No sustained flaming occurs after the flame source is removed.
• Dripping or melting material does not contribute to further flame propagation.

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6. Applications
The test is critical for cables used in:

• Buildings: Ensures safe cable performance in commercial and residential structures.
• Industrial Facilities: Verifies cable performance in vertical trays in factories and plants.
• Transportation Systems: Used for evaluating fire safety in tunnels, rail systems, and ships.

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7. Key Highlights
Key Aspects of the Test:

• Simulates real-world fire conditions in vertical installations.
• Evaluates flame propagation, dripping, and cable integrity.

Importance of Compliance:

• Ensures fire safety and reduces fire risks in critical installations.
• Helps manufacturers certify cables for fire-resistance applications.

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8. Conclusion
The **vertical flame spread test (Category C)** evaluates the ability of bunched wires or cables to resist flame propagation under fire conditions. Compliance ensures that cables meet fire safety standards, protecting life and property in various applications.

Key Points:

• Vertical flame spread limit: ≤ **2.5 meters**.
• Flame source: **20.5 kW burner for 20 minutes**.
• Critical for building, industrial, and transportation fire safety.

References: IEC 60332-3-24, fire testing standards, and industry best practices.