One-Stop Solution for Marine Cable Fire Testing

As China’s shipbuilding industry continues to lead the global market in order backlog, fire safety requirements for marine ancillary products have become a focal point of industry attention. Recently, Dongguan Zhongli Instrument Technology Co., Ltd. announced that its marine cable fire testing equipment portfolio has reached full maturity, offering comprehensive testing services for marine cables in accordance with major international standards including IEC, ISO, and BS — covering flame retardancy, smoke density, gas corrosivity/toxicity, and fire resistance.

The Safety Imperative Behind the Shipbuilding Boom

China currently ranks first globally in key shipbuilding metrics including completed tonnage, new orders, and order backlog. High-value-added vessels such as LNG carriers and large cruise ships have order books extending several years forward. Against this backdrop, fire safety has become a non-negotiable priority for both shipowners and classification societies.

Marine cables serve as the “nervous system” of a vessel, transmitting power and signals throughout the ship. In a fire scenario, their ability to inhibit flame propagation and maintain circuit integrity during a fire directly impacts crew safety and vessel survivability. The International Maritime Organization (IMO) and various classification societies have established stringent testing requirements for marine cables, covering flame retardancy, low-smoke zero-halogen (LSZH) characteristics, and fire resistance. Zhongli Instrument’s equipment lineup precisely addresses these core testing needs.

Four Testing Dimensions Covering Mainstream Standards

Zhongli Instrument has developed a complete testing protocol for marine cable fire performance, encompassing four critical dimensions:

Flame Retardancy Testing

Flame retardancy testing evaluates a cable’s ability to prevent flame propagation — the most fundamental fire safety requirement for marine cables.

The ZL-1028 Single Vertical Wire Burning Tester is designed in accordance with IEC 60332-1-1 and IEC 60332-1-2 standards. It is suitable for determining the vertical flame propagation performance of single insulated wires, control cables, cross-linked cables, and marine cables. The unit features a 1kW standard burner with a blue inner flame height of 50–60mm and a total flame height of 170–190mm, with an adjustable flame application time ranging from 0.1 to 999.9 seconds. During testing, the burner is positioned at a 45° angle to the vertical axis of the specimen, with the flame contact point located 475mm below the lower edge of the upper support — accurately simulating a cable’s behavior under flame attack in vertical installation conditions.

The ZL-1020 Standard Bundled Wire & Cable Burning Tester complies with IEC 60332-3-10 and IEC 60332-3-21 through 3-25 series standards, simulating flame spread suppression performance of bundled cables in actual installation conditions. A single cable passing the flame retardancy test does not guarantee the same performance when cables are bundled together — when multiple cables are installed in proximity, flames can propagate progressively through gaps between cables and along cable sheaths. The bundled burning test therefore represents a more rigorous assessment.

As a supplementary offering, the ZL-1021 UL1581 Wire & Cable Burning Tester meets UL 1581 standards, serving cable products destined for the North American market or specific shipowner requirements, thereby enhancing the international compatibility of the equipment portfolio.

Smoke Density Testing

Smoke generated during a fire is one of the primary causes of casualties — it not only obstructs evacuation and rescue efforts but also causes hypoxia and poisoning. Smoke density testing evaluates the volume of smoke produced when cables burn.

The ZL-1049 Cable Smoke Density Tester features a 3m × 3m × 3m (27 m³) large-scale combustion chamber and complies with IEC 61034-1/2 standards. This standard is a critical test method for the low-smoke zero-halogen flame-retardant characteristics of cables. Its principle is based on the Lambert-Beer law — smoke particles generated during cable combustion cause attenuation of light intensity through reflection and scattering, quantified as light transmittance. The system employs a 100W quartz halogen lamp as the light source and a silicon photocell as the receiver. A transmittance of 0% indicates complete light blockage, while 100% indicates full transmission. During testing, 1.0L of alcohol serves as the standard ignition source, contained in a stainless steel pan with bottom dimensions of 210mm × 110mm, top dimensions of 240mm × 140mm, and a height of 80mm. A bench-top fan ensures uniform smoke distribution within the combustion chamber to guarantee measurement accuracy.

It is worth noting that IEC 61034 includes normalization requirements for transmittance calculations based on cable outer diameter: for cables with an outer diameter exceeding 80mm, measured minimum transmittance values must be corrected. The 2019 edition introduced a new normalization formula for cables with an outer diameter greater than 20mm. This is particularly significant for high-voltage cables, which typically have outer diameters exceeding 80mm, as the allocation of performance targets directly impacts product qualification.

Complementing the ZL-1049 is the ZL-3078 Plastic Burning Smoke Density Tester, which complies with ISO 5659-2. It employs a single-chamber method to determine smoke production trends at the material level, making it suitable for smoke density analysis of cable insulation and sheathing materials.

Smoke Toxicity / Corrosivity Testing

Marine cables are required not only to be “low-smoke” but also “zero-halogen” — meaning that gases released during combustion should not be highly corrosive or toxic.

The ZL-1050 Halogen Acid Gas Release Measurement Apparatus is designed in accordance with IEC 60754-1 and IEC 60754-2 standards. It is specifically used to measure the total halogen acid gas released during cable material combustion, as well as the pH value and conductivity of the resulting gases. IEC 60754-1 specifies the determination method for halogen acid gas content: a tube furnace is preheated to 800°C, a quartz tube containing a 1.0g specimen is pushed into the furnace, and the combustion gases are carried by airflow into a sodium hydroxide solution for absorption, followed by measurement of the halogen acid content in the solution. IEC 60754-2 determines the acidity of combustion gases by measuring the pH value and conductivity of the aqueous solution to assess gas corrosivity.

According to these standards, cable materials with halogen acid gas release below 5mg/g are classified as zero-halogen (LSZH), while those between 5mg/g and 15mg/g fall into the low-halogen (LSF) category. For zero-halogen cables, the pH value of the aqueous solution must exceed 4.3 and conductivity must be below 10 μS/cm. The IEC 60754-1 method cannot reliably quantify halogen levels below 5mg/g; in such cases, IEC 60754-2 must be used as a complementary verification. This standard system forms the basis for the “low-smoke zero-halogen” requirement commonly applied to modern marine cables.

The ZL-1056 Material Smoke Toxicity Hazard Classification Tester complies with ISO 19700. It heats materials in a tube furnace and collects the resulting smoke, enabling toxicity classification of combustion products — essential for assessing the toxicity risk of combustion effluents in confined spaces such as ships.

Fire Resistance (Circuit Integrity) Testing

Fire resistance testing is the most critical component of the entire solution — it verifies whether a cable can maintain circuit integrity and continue power supply during a fire.

The ZL-1048 Cable Fire Resistance Integrity Tester is designed in accordance with IEC 60331-11, IEC 60331-21, IEC 60331-23, IEC 60331-25, as well as BS 6387 and BS 8491. IEC 60331-21 specifies the test procedures and requirements for maintaining circuit integrity of cables rated 0.6/1kV and below under fire conditions: flame temperature not less than 750°C, with a recommended fire exposure time of 90 minutes, during which no water spray or mechanical shock is applied. The specimen must be energized at its rated voltage during the test — for multi-core cables, voltage is applied between conductors; for single-core cables, voltage is applied between conductor and earth or between conductor and metallic screen. After the fire exposure period, power supply must be maintained for an additional 15 minutes. The cable passes the fire resistance test if no fuse or circuit breaker operates and no test lamp extinguishes.

For more demanding applications, IEC 60331-1 specifies fire resistance testing with mechanical shock: flame temperature not less than 830°C, applicable to cables rated 0.6/1kV and below with an outer diameter exceeding 20mm. The newly published IEC 60331-4:2024 extends this test method to medium-voltage cables rated above 1kV and up to 30kV, and introduces water spray or water jet impact testing as optional procedures, with a 1000°C flame temperature option available for special applications. The British standards BS 6387 and BS 8491 impose similar requirements, with some high-end fire-resistant cables required to maintain power supply at flame temperatures of 830°C or even 950°C while simultaneously subjected to water spray and mechanical shock.

Complete Equipment Matrix

Industry Significance and Outlook

Industry analysts note that, in the past, cable fire testing equipment in China was fragmented across individual standards or single test dimensions. To complete a full certification test suite for marine cables, manufacturers often had to submit samples to multiple laboratories. With its integrated equipment matrix — spanning single/bundled flame retardancy, smoke density and toxicity, and fire resistance — Zhongli Instrument enables testing to be conducted within a single technical framework, improving test efficiency and standard consistency.

Of particular note, as the SOLAS Convention continues to raise the bar for fire safety on ships, and as classification societies including China Classification Society (CCS), DNV, and ABS increasingly refine their requirements for marine cable type approval, the fire-resistant cable market is expanding rapidly. The newly released IEC 60331-4:2024 has extended fire resistance testing to medium-voltage cables up to 30kV and introduced water spray and 1000°C flame options, reflecting the industry’s drive toward higher safety levels. Zhongli Instrument’s completion of its equipment portfolio arrives at precisely the right moment to capture this growing market segment.

About Dongguan Zhongli Instrument Technology Co., Ltd.

Dongguan Zhongli Instrument is a technology company specializing in the R&D and manufacturing of fire retardancy and flame resistance testing instruments. Its products are widely used in quality inspection and certification testing for wire and cable, building materials, marine equipment, and other industrial sectors. Backed by a professional technical team and a comprehensive after-sales service system, the company is committed to providing one-stop fire testing solutions for its customers.