Research and Testing on the Burning Rate of Oxygen-Acetylene Lines

Research and Testing on the Burning Rate of Oxygen-Acetylene Lines – Accredited ISO/IEC 17025 Fire Performance Assessment for the Croatian Market

Oxygen‑acetylene lines are essential components in welding, cutting, and thermal processing applications across the manufacturing, shipbuilding, construction, and metalworking industries. The burning rate of these flexible hoses and pipelines is a critical fire safety parameter that determines their resistance to flame propagation, heat release, and sustained combustion when exposed to fire or high‑temperature environments. In the Croatian market, where the Hrvatski zavod za norme (HZN), the Ministarstvo gospodarstva i održivog razvoja, the Državni inspektorat, the Agencija za zaštitu okoliša (AZO), and the Carinska uprava enforce strict quality, fire safety, and environmental standards aligned with EU directives and HRN EN (Croatian standards based on European norms), the accurate evaluation of the burning rate of oxygen‑acetylene lines is essential for product certification, supplier qualification, quality control in manufacturing, and import‑export processes. Our laboratory offers a comprehensive research and testing service for the burning rate of oxygen‑acetylene lines, applying standardized methods such as ISO 6940, ISO 6941, ASTM D635, and EN 13485 to measure flame spread rate, burn length, self‑extinguishing behavior, and heat release characteristics under controlled laboratory conditions. All tests are performed under our ISO/IEC 17025 (CNAS) accreditation, and the resulting reports are fully accepted by Croatian authorities and notified bodies, making them indispensable for regulatory compliance, product validation, and market access in Croatia and the European Union.

Oxygen‑Acetylene Line Samples We Regularly Test

Our laboratory receives a wide variety of oxygen‑acetylene hoses and pipeline assemblies for burning rate testing. Typical samples include:

• Single‑layer and multi‑layer rubber hoses – for welding and cutting torches, with and without textile or wire reinforcement.
• Thermoplastic hoses – made of PVC, polyurethane, or other polymers for special applications.
• Reinforced and braided hoses – with steel wire braiding or textile reinforcement for high‑pressure service.
• Composite hoses – with multiple layers of different materials for specific chemical and thermal resistance.
• Hose assemblies with end fittings – including crimped, swaged, or threaded connections, to evaluate the burning rate at joints.
• Prototype and new hose formulations – submitted by manufacturers for validation of fire performance before series production.
• Field‑retrieved hoses – for failure analysis and remaining life assessment.

Burning Rate and Flame Spread Testing – Standard Methods for Flexible Lines

The burning rate of oxygen‑acetylene lines is typically evaluated by measuring the flame spread rate, the burn length, and the self‑extinguishing behavior of the material when exposed to a specified ignition source. Our tests follow international standards and the requirements of the Croatian fire safety and industrial sectors.

• Flame spread rate test for horizontal specimens (ASTM D635 / ISO 1210 / HRN EN ISO 1210 – for plastics and rubber hoses) – we mount a horizontal specimen of the hose (or a flat section of the hose material) in a test chamber. A specified flame is applied to one end for a specified time (e.g., 15 seconds). The time to reach a specified burn mark (e.g., 25 mm) and the total burn length are recorded. The burning rate (in mm/min) is calculated. We report the burning rate, the total burn length, and the self‑extinguishing behavior (whether the specimen stops burning after the flame is removed).
• Vertical flame spread test for cables and hoses (IEC 60332‑1‑2 / EN 50265‑2‑1 / HRN EN 50265‑2‑1 – for vertical specimens) – we mount a vertical specimen of the hose in a test chamber and apply a specified flame to the bottom of the specimen for a specified time (e.g., 60 seconds). The damage length (the length of the specimen that has been burned or charred) is measured. The burn rate and the after‑flame time are recorded. We report the damage length, the after‑flame time, and the burn rate.
• Oxygen index test (ASTM D2863 / ISO 4589‑2 / HRN EN ISO 4589‑2 – for measuring the minimum oxygen concentration to support combustion) – we measure the minimum oxygen concentration (in %) that will just support the combustion of the hose material in a flowing mixture of oxygen and nitrogen. A higher oxygen index indicates a lower flammability. We report the oxygen index (LOI) in %.
• Heat release rate test (ISO 5660‑1 / HRN EN ISO 5660‑1 – cone calorimeter method) – we expose a flat specimen of the hose material to a controlled heat flux (e.g., 50 kW/m²) in a cone calorimeter. The heat release rate (HRR, in kW/m²), the total heat released (THR, in MJ/m²), and the time to ignition (in seconds) are measured. We report the HRR, THR, and the time to ignition.
• Smoke production and toxicity (ASTM E662 / ISO 5659‑2 / HRN EN ISO 5659‑2 – for smoke density) – we measure the specific optical density (Ds) of the smoke produced during combustion, and we analyze the composition of the combustion gases for toxic compounds (CO, CO₂, HCl, HCN, etc.). We report the smoke density and the gas concentrations.

Testing of Hose Assemblies and End Fittings – Evaluating the Burning Rate of Complete Systems

In many applications, the burning rate of the complete hose assembly (including the end fittings and the connections) is more relevant than the burning rate of the bare hose material. Our tests evaluate the fire performance of complete hose assemblies, including the effect of the fittings on the flame spread and the potential for leakage.

• Assembly burn test (NTC 5600 – for complete hose assemblies with fittings) – we mount a complete hose assembly (with fittings on both ends) in a horizontal or vertical test fixture and apply a flame to the middle of the assembly (or to the fittings) to simulate a fire exposure. The burn rate, the flame spread, and the integrity of the fittings are monitored. We report the burn rate, the damage length, and the condition of the fittings.
• Fitting and coupling fire resistance test (NTC 5601 – for the effect of fittings on fire spread) – we test the hose assembly with the flame applied directly to the fitting, to evaluate the resistance of the fitting to fire‑induced failure (e.g., leakage, melting, or separation). We report the time to failure and the failure mode.
• Pressure decay after fire exposure (NTC 5602 – for evaluating the integrity of the assembly after burning) – after the burn test, we pressurize the hose assembly (with nitrogen or air) and measure the pressure decay to detect any leaks caused by the fire damage. We report the pressure decay rate and the leak rate.
• Burning rate at different orientations (NTC 5603 – for horizontal, vertical, and inclined orientations) – we perform the burn test with the hose assembly in different orientations (horizontal, vertical, and at a 45° angle) to evaluate the effect of the orientation on the flame spread. We report the burn rate for each orientation.
• Effect of internal pressure on the burning rate (NTC 5604 – for pressurized hoses) – we perform the burn test with the hose pressurized (e.g., with air or nitrogen at the working pressure) to simulate the actual service condition, which can affect the flame spread and the rate of combustion. We report the burn rate and the effect of the pressure.

Environmental and Aging Effects on the Burning Rate – Evaluating Durability and Fire Performance

The burning rate of oxygen‑acetylene lines can change over time due to thermal aging, UV exposure, chemical attack, and mechanical stress. Our environmental and aging tests evaluate the long‑term stability of the fire performance, which is essential for ensuring the safety of the equipment over its service life.

• Thermal aging and subsequent burn test (ASTM D573 / ISO 188 / NTC 5610 – for the effect of heat on fire performance) – we age the hose material in an oven at a specified temperature (e.g., 70 °C) for a specified duration (e.g., 7, 14, or 28 days). After aging, we perform the burn test to evaluate the change in the burning rate. We report the burning rate before and after aging and the percentage change.
• UV aging and burn test (ASTM G154 / NTC 5611 – for outdoor‑exposed hoses) – we expose the hose material to UV radiation (UVA‑340) and condensation cycles for a specified duration (e.g., 500 hours). After the UV exposure, we perform the burn test to evaluate the effect of UV degradation on the fire performance. We report the burning rate after UV exposure and the change.
• Chemical immersion and burn test (ASTM D471 / NTC 5612 – for hoses exposed to oils and solvents) – we immerse the hose material in various chemicals (e.g., mineral oil, hydraulic fluid, or a solvent) for a specified duration (e.g., 7 days) and then perform the burn test. We report the burning rate after chemical immersion and the compatibility with the chemicals.
• Ozone aging and burn test (ASTM D1149 / ISO 1431‑1 / NTC 5613 – for the effect of ozone) – we expose the hose material to an ozone atmosphere (e.g., 50 ppb) at 40 °C for 48 hours, and then we perform the burn test. We report the burning rate after ozone exposure and the condition of the surface.
• Wear and abrasion effect (NTC 5614 – for the effect of mechanical damage on the burning rate) – we subject the hose material to a specified number of abrasion cycles (e.g., using a Taber abraser) and then we perform the burn test to evaluate the effect of the surface wear on the flame spread. We report the burning rate after abrasion and the surface condition.

Material Characterization and Chemical Composition – Correlating Properties with Fire Performance

To fully understand the factors that control the burning rate and to optimize the formulation of the hose material, we perform material characterization and chemical composition analysis. These tests are essential for the development of fire‑resistant hose materials and for the troubleshooting of fire performance issues.

• Thermogravimetric analysis (TGA) – ASTM E1131 / NTC 5620 – for measuring the thermal stability and the decomposition temperature – we measure the mass loss of the hose material as a function of the temperature (up to 800 °C) in air and in nitrogen. The decomposition temperature and the char yield are determined. We report the decomposition temperature, the char yield, and the mass loss.
• Differential scanning calorimetry (DSC) – ASTM D3418 / NTC 5621 – for measuring the glass transition temperature (Tg) and the melting temperature – we measure the thermal transitions of the hose material. The Tg and the melting point are reported, which are related to the thermal stability and the fire performance.
• Fourier‑transform infrared spectroscopy (FTIR) – ASTM E168 / NTC 5622 – for the polymer identification and the analysis of additives – we use FTIR to identify the polymer type (e.g., EPDM, NBR, PVC, or PU) and to detect the presence of flame retardants, plasticizers, or other additives that affect the burning rate. We report the polymer type and the additive composition.
• Elemental analysis (XRF or EDS – NTC 5623 – for the detection of inorganic flame retardants) – we use X‑ray fluorescence (XRF) or energy‑dispersive spectroscopy (EDS) to detect the presence of halogenated flame retardants, antimony oxide, or other inorganic additives that influence the combustion behavior. We report the elemental composition and the flame‑retardant content.
• Scanning electron microscopy (SEM) of the burned residue – NTC 5624 – for the char morphology analysis – we examine the char layer formed after the burn test using SEM. The morphology of the char (e.g., porous, dense, or cracked) is related to the fire performance and the flame‑retardant effectiveness. We report the SEM images and the char morphology.

Test Report and Recognition in the Croatian Safety and Industrial Sector

All procedures described are within the scope of our ISO/IEC 17025 accreditation, with equipment calibrated periodically (burn test chambers, oxygen index testers, cone calorimeters, TGA, DSC, etc.) and traceability to international standards (NIST, PTB). Our test reports are issued in English (with a Croatian summary available on request) and include:

• Full identification of the hose sample (manufacturer, hose type, dimensions, material composition, and intended application).
• Detailed description of the test methods applied (ASTM/ISO/IEC/HRN EN/NTC standards, test conditions, and measurement parameters).
• Numerical results: burning rate (mm/min), burn length (mm), after‑flame time (s), oxygen index (%), heat release rate (kW/m²), total heat released (MJ/m²), smoke density (Ds), and decomposition temperature (°C).
• Graphical data: burning rate vs. time curves, heat release rate vs. time curves, and TGA/DSC thermograms.
• Comparative tables against the values specified by the client or against the limits of the relevant standards (ISO 6940, ISO 6941, ASTM D635, HRN EN ISO 11654, and the requirements of the HZN, Ministarstvo gospodarstva, and Državni inspektorat for fire safety).
• Photographs and micrographs of the test specimens before and after the burn test, and the char morphology (SEM).
• Recommendations for material selection, formulation improvement, and the use of flame retardants to reduce the burning rate and to enhance the fire safety.
• Expanded uncertainty (k=2) for all key measurements, calculated according to the ISO/IEC 98‑3 Guide.

These reports are fully accepted by the Hrvatski zavod za norme (HZN) for the verification of product conformity, by the Ministarstvo gospodarstva i održivog razvoja for industrial safety compliance, by the Državni inspektorat for market surveillance, by the Agencija za zaštitu okoliša (AZO) for environmental protection, and by the Carinska uprava (Croatian Customs) for tariff classification and quality verification in the import of oxygen‑acetylene lines and related components. Additionally, we offer consulting services for the selection of fire‑resistant hose materials, the design of flame‑retardant formulations, and the implementation of fire safety programs, contributing to the safety, reliability, and compliance of welding and cutting operations in the diverse Croatian manufacturing, shipbuilding, and construction sectors.