Cable Testing Fire Resistant Cable

Cable Testing & Fire Resistant Cable

If you need in-depth information regarding cable testing standards and fire-resistant cables, the National Fire Protection Association (NFPA) highlights the importance of using cables that maintain integrity during fire conditions. Proper testing ensures that cables can effectively resist flames, limit smoke development, and reduce toxicity in emergency situations.

Fire Performance Testing

Currently, in the cable industry, Fire Retardant, Low Smoke Halogen Free (LSOH) or Low Smoke Fume (LSF), and Fire Resistant cables are commonly referred to as Fire Retardant & Resistant Cables.

In the cable sector, the most common standards include:

1. IEC Flame Retardant Grade
2. UL Fire Standard
3. IEC Fire Resistance Testing

IEC Flame Retardant Grade

The European Electrical Committee has categorized the fire performance of cables into three classes:

IEC-1, IEC-2 & IEC-3. IEC-1 and IEC-2 assess the flame propagation characteristics of single wires, while IEC-3 evaluates the same characteristics for bundled cables. It's important to note that IEC-3 has stricter requirements compared to IEC-1.

IEC -1/BS -1 (Flame Test On Single Vertical Insulated Wires/Cables)

This test offers a method for assessing the flame propagation characteristics of a single wire or cable, where a 60 cm cable sample is vertically placed inside a metallic container, with a flame applied at a specific angle and distance. The specimen must not exhibit burning within a certain proximity after the flame application. This standard may not be suitable for thin wires due to conductor melting during the flame application period.

IEC -3/BS -3 (Flame Test On Bunched Wires/Cables)

IEC-3 describes a method for type approval testing to assess the capacity of bundled cables to resist fire. Here, multiple cable samples are vertically tested with a flame applied for specific durations under controlled airflow conditions. Four classification categories (A, B, C & D) are established based on test duration and sample material quantity. If the extent of charred or damaged cable does not exceed 2.5m after flame exposure, the sample meets the standard requirements.

UL Fire Standard

When a cable satisfies a specified UL fire standard, a UL performance verification mark is applied to the cable jacket, indicating both the UL classification and number. The primary fire testing standards encompass:

CMP (Plenum Flame Test/ Steiner Tunnel Test)

Plenum rated cables comply with the NFPA-262 standard, which is the most rigorous of all tests. The samples are subjected to a controlled flame exposure in a horizontal tunnel for a period. To be eligible for a plenum rating, the cables must demonstrate limited flame spread and smoke density during the exposure period.
CMP cables are usually utilized in air ventilation systems and air returns and have superior flame-resistant properties compared to LSOH cables compliant with IEC standards.

CMR (Riser Flame Test)

Riser-rated cables must meet UL's stringent testing requirements, specifically designed for applications in vertical shafts where the cable is exposed to flame for extended durations. The criteria here specify that the flame spread must remain contained within specified limits.

CM (Vertical Tray Flame Test)

General purpose cables meet UL standards, where samples are tested along a vertical tray for a specified duration. The test ascertains that flame propagation does not reach the upper segment of the cable.

CMG (Vertical Tray Flame Test)

CMG cables also adhere to UL standards and are recognized in both Canada and the USA under similar conditions as CM cables.

CMX(Vertical Wire Flame Test)

The restricted category cable meets UL criteria, outlining strict testing protocols to control flame exposure while ensuring that certain burning limitations are not exceeded for safe operational capacity. This type of cable is appropriate for residential and raceway applications but must be adequately protected from bundling.

       IEC Fire Resistance Testing

Fire-resistant cables are designed to maintain circuit integrity during fire incidents. Standards established by both IEC and BEC dictate rigorous requirements, with BS offering even higher benchmarks for performance.
IEC Fire Performance Standard

A sample cable is placed above a gas flame and connected to its rated voltage. Fire exposure lasts for three hours, reaching high temperatures. Post-exposure, the cable is reenergized after a 12-hour cooling period; it must continue to perform as required.

BS Fire Performance Standard
The BS standard categorizes cables based on their maintenance of circuit integrity and outlines several exposure conditions. Under these protocols, various survival categories are instituted based on exposure durations and tests.