The solid woven conveyor belt alcohol burner test is a fundamental flame retardancy evaluation for PVC and PVG solid woven conveyor belts used in underground coal mines and other hazardous environments. This article explains the test principle, specimen requirements, procedure, and pass criteria based on the relevant Chinese coal industry standards (MT 113 and MT 914) and how it compares with international burner test methods such as ISO 340.
Technical Overview
Solid woven conveyor belts—typically PVC-type or PVG-type constructions with a single-layer, impregnated solid woven carcass—are the dominant belting solution for underground coal mine conveyance. Because they operate in an environment where methane gas and coal dust create a serious fire and explosion risk, these belts must demonstrate reliable self-extinguishing behavior. The alcohol burner test is the primary laboratory method used to verify this property.
In the test, full-thickness belt specimens are exposed to a standardized flame produced by an alcohol blast burner. After the ignition source is removed, the laboratory records how long the specimen continues to burn with flame (afterflame time) and how long it continues to glow without flame (afterglow time). A belt that self-extinguishes quickly after the ignition source is withdrawn is considered to have acceptable flame retardancy.
- Test method basis: Chinese coal industry standard MT 113 (general test methods and judgment rules for flame-retardant and antistatic polymer products used in coal mines).
- Product requirement basis: Chinese coal industry standard MT 914 (flame-retardant solid woven conveyor belts for coal mines).
- International comparison: ISO 340 (conveyor belts—flame retardation—specification and test method), which uses a propane burner as the ignition source.
- Complementary safety tests: drum friction test and surface electrical resistance test, which together with the alcohol burner test form the complete safety assessment for coal mine belts.
Testing Samples
Solid Woven Belt Specimens
Specimens are cut from the finished belt at a distance of no less than 50 mm from the belt edge to avoid edge effects. Full-thickness specimens are taken in both the longitudinal (along the belt length) and transverse (across the belt width) directions, because flame propagation behavior differs along and across the solid woven carcass. Typical specimen dimensions per MT 113 are approximately 360 mm in length and 50 mm in width, and the covers and carcass must be tested together without separation.
Specimen Conditioning and Quantity
Prior to testing, specimens are conditioned in a controlled laboratory atmosphere so that temperature and humidity do not distort the combustion results. Specimens must be free of visible defects such as cracks, blisters, or cover damage. A complete test set normally requires at least six valid specimens, with spare specimens retained for repeat testing if any individual result is disputed or a retest is permitted under the standard.
Testing Items
The alcohol burner test quantifies the flame retardancy of the belt through the following measured and observed items:
- Afterflame time (flaming combustion time after removal of the burner)—individual values and arithmetic mean.
- Afterglow time (flameless, glowing combustion time after flaming ceases)—individual values and arithmetic mean.
- Qualitative observations, including whether the flame reaches reference marks on the specimen, whether flaming drips occur, and the general burning behavior of the belt.
For a complete coal mine safety evaluation, the alcohol burner test is usually performed alongside the surface resistance test (antistatic performance) and the drum friction test, which together define the flame-retardant and antistatic requirements of solid woven conveyor belts.
Testing Methods
Apparatus and Test Conditions
The test is conducted in a draft-protected enclosure using a dedicated alcohol blast burner fueled by ethanol of not less than 95% purity. Before each test, the burner flame is adjusted and verified to the specified configuration—typically an outer flame length in the range of approximately 150 mm to 180 mm with a stable blue flame—so that every specimen receives an equivalent ignition source. A specimen holder fixes the specimen at a defined inclination of 45 degrees with respect to the vertical.
Test Procedure
- Condition and mark each specimen, then mount it on the specimen holder at the specified 45-degree angle.
- Ignite the alcohol burner, verify the flame length and stability, and bring the flame into contact with the lower portion of the specimen.
- Apply the flame to the specimen for the specified exposure time of 45 seconds.
- Withdraw or extinguish the burner and immediately start timing: record the afterflame time until visible flaming ceases, then record the afterglow time until all glowing combustion stops.
- Repeat the procedure for all specimens in each direction, then calculate the arithmetic mean values of afterflame and afterglow times.
Acceptance Criteria
For flame-retardant solid woven conveyor belts for underground coal mines, the results are judged against the limits specified in the MT standard series, commonly expressed as follows:
- Afterflame time: no single specimen may exceed 10 seconds, and the arithmetic mean of the six tested specimens must not exceed 3 seconds.
- Afterglow time: no single specimen may exceed 30 seconds, and the arithmetic mean must not exceed 10 seconds.
These limits ensure that even if the belt is ignited by a short-duration flame, it will self-extinguish rapidly and will not propagate fire along the conveyor line. Users should always confirm the requirements of the current edition of the applicable standard, as limit values and retest rules may be revised.
Applications
The alcohol burner test is applied wherever solid woven flame-retardant conveyor belts must be qualified for safety-critical service:
- Underground coal mine conveyance, where PVC and PVG solid woven belts are mandatory for flame-retardant and antistatic performance and are subject to mining product safety mark certification requirements in China.
- Factory quality control and batch release testing by belt manufacturers, verifying that PVC paste formulations and antimony-based or other flame-retardant additive systems remain effective in production.
- Research and development of flame-retardant compounds, carcass impregnation processes, and cover compounds, where burner test data guide formulation optimization.
- Procurement acceptance and periodic verification by mine operators and engineering contractors who need documented evidence of belt fire safety.
- Adjacent industries with combustible atmospheres—such as coking plants, power stations, ports, and tunnel construction—where self-extinguishing belt performance is specified in technical requirements.
FAQ
What does the alcohol burner test evaluate for solid woven conveyor belts?
It evaluates the self-extinguishing capability of the belt. The test measures how quickly flaming and glowing combustion stop after a standardized alcohol burner flame is removed, which indicates whether the belt can prevent fire propagation along the conveyor in the event of brief ignition.
What fuel and flame source are used?
The test uses a specially designed alcohol blast burner fueled by ethanol of at least 95% purity. The flame is adjusted to a standardized length and configuration before each test to guarantee reproducibility of the ignition conditions between specimens and between laboratories.
How is the alcohol burner test different from the ISO 340 propane burner test?
ISO 340, the international conveyor belt flame retardation standard, uses a propane gas burner as the ignition source with its own specimen size, exposure conditions, and limit values. The alcohol burner test under the MT standard series uses an alcohol blast burner and is the basis for coal mine belt acceptance in China. The two methods are related in principle but not directly interchangeable, so belts should be tested according to the standard required by the target market or purchaser.
When is the test required?
It is required for product type approval and mining safety certification, for routine batch testing during production, after any change in formulation or manufacturing process, and whenever customers or regulators request documented flame retardancy evidence for solid woven conveyor belts.
Can the test be performed on belts already in service?
Yes, full-thickness specimens can be taken from in-service belts to verify that flame retardancy has not degraded due to aging, wear, or contamination. However, sampling should be performed by qualified personnel, and results should be interpreted with reference to the original type-test data.