What is a Bundle Wire and Cable Burning Tester?

In the modernization of power systems, telecommunications, and transportation infrastructure, electrical wires and cables function like the “blood vessels” and “nervous system” of the human body, carrying energy and information throughout complex networks. However, in fire incidents, the ignition and flame spread of cables often play a decisive role in the escalation of damage. The bunched cable flame propagation test apparatus, as a core device for evaluating the flame-retardant performance of cables, provides scientific evidence for material development, product certification, and safety standard formulation by simulating realistic fire scenarios. It has therefore become a critical line of defense in ensuring electrical safety.

Technical Principles

The primary function of a bunched cable flame propagation test apparatus is to evaluate the ability of vertically mounted cable bundles to inhibit upward flame spread under specified conditions. Its design strictly follows international standards (such as IEC 60332-3-10) and national standards (such as GB/T 18380.3). By precisely controlling flame intensity, burning duration, and ventilation conditions, the apparatus reproduces the combustion behavior of cables in real fire situations.

1. Combustion System: The “Heart” of a Stable Flame Source

The apparatus uses a ribbon-type propane burner torch. The burner nozzle consists of 242 micro-orifices with a diameter of 1.32 mm, arranged in three staggered rows to ensure uniform flame distribution. Combined with a Venturi-type gas mixer and high-precision mass flow controllers, the propane–air mixture ratio can be accurately adjusted, maintaining a stable flame temperature of 820 °C ±5 °C in accordance with standard requirements. Certain configurations employ dual burner systems capable of delivering a nominal heat output of 20.5 kW ±0.5 kW, simulating extreme fire conditions.

2. Combustion Chamber: Dual Protection of Insulation and Observation

The combustion chamber is constructed with a steel frame structure. Its inner walls are filled with mineral wool insulation, while the exterior is clad with stainless steel panels coated with black, corrosion-resistant paint to minimize heat loss. A fire-resistant tempered glass observation window is installed at the front, allowing operators to observe the combustion process in real time while protecting them from high-temperature radiation. Air inlet and exhaust outlets are positioned at the top and bottom, with airflow controlled by a variable-frequency fan at 5000 ± 500 L/min to ensure a stable test environment.

3. Ladder and Sample Rack: The “Skeleton” for Precise Fixation

The apparatus is equipped with standard-width (500 mm) and wide-type (800 mm) steel ladders to accommodate cables of different specifications. The sample rack uses an electric lifting mechanism with a load capacity exceeding one ton, enabling rapid installation and removal of test specimens. During installation, cables are arranged in a single layer with spacing equal to half the cable diameter (not exceeding 20 mm), ensuring uniform flame exposure.

Core Functions

1. Flame Spread Testing: Quantifying Flame-Retardant Performance

During testing, the burner is positioned horizontally at 75 ± 5 mm below the lower edge of the cable bundle, and the flame is applied continuously for 40 minutes or until complete combustion occurs. The flame-retardant classification is determined by measuring the vertical flame spread distance. For example, in tests of low-smoke, halogen-free cables, flame spread distances significantly below the standard limit of 2.5 m demonstrate successful compliance with higher flame-retardant classifications.

2. Heat Release and Smoke Generation Analysis: Revealing Fire Risks

Some advanced systems integrate heat release rate measurement modules. By analyzing the heat output and smoke generation during combustion, the apparatus helps evaluate the impact of cables on fire growth and evacuation safety. Studies have shown that certain flame-retardant formulations can significantly reduce heat release rates, providing valuable data for product optimization.

3. Multi-Parameter Coordinated Control: Simulating Complex Environments

The apparatus can simultaneously regulate temperature (from ambient to 80 °C), humidity (50%–95% RH), and spray cycles to simulate extreme conditions such as rainfall, high temperature, and high humidity. Such combined environmental simulations allow accelerated evaluation of cable performance under long-term service conditions, significantly reducing development and validation time.

Application Scenarios

1. Material Research and Development: Accelerating Cable Innovation

In polymer material research, the apparatus is used to evaluate the flame retardancy and ultraviolet resistance of new plastics and rubber compounds. By adjusting formulation parameters, researchers can identify material systems with improved resistance to thermal and photochemical degradation.

2. Quality Control: Enforcing Production Standards

Cable manufacturers conduct routine sampling tests in accordance with relevant standards. By automatically recording combustion duration and flame spread distance, the apparatus helps reduce defect rates, prevent quality-related complaints, and avoid costly recalls.

3. Certification Testing: Supporting Market Access

Testing laboratories use the apparatus to generate standardized reports that support compliance with international regulations and certification requirements. Successful testing enables products to enter global markets and meet the safety expectations of different regions.

4. Failure Analysis: Tracing Root Causes

When cables exhibit issues such as discoloration, insulation degradation, or short circuits during service, the apparatus can reproduce high-temperature and high-humidity conditions to identify underlying causes. This supports targeted formulation adjustments and verification of corrective measures.

Technological Evolution

1. Intelligent Control Systems: Improved Usability

Modern apparatuses adopt computer-based control systems with dedicated software, enabling guided operation and automatic parameter adjustment. Real-time display of flame temperature and airflow data, along with automatic generation of standardized test reports, significantly reduces human error.

2. Modular Design: Expanding Application Scope

By replacing burners, ladders, or accessories, some systems can be adapted for testing single cables, optical cables, or sheathed cables. This modularity allows multiple test standards to be conducted on a single platform, reducing equipment investment costs.

3. Environmental Protection and Safety: Supporting Sustainable Development

High-capacity exhaust fans and efficient filtration systems rapidly remove hazardous combustion gases, protecting operator health. Safety features such as automatic gas shut-off and reliable ignition systems further reduce operational risks.

With its precise simulation capabilities, flexible testing configurations, and strict compliance with standards, the bunched cable flame propagation test apparatus has become an indispensable quality control tool in the cable industry. From laboratory research to production-line inspection, and from national standards to international certification, it helps manufacturers shorten development cycles, reduce quality risks, and enhance product safety. As electrical safety continues to gain global importance, this equipment remains a vital safeguard for the “blood vessels” and “nervous systems” of modern energy transmission and information communication networks.