The standard "EN ISO 340 Conveyor belts - Laboratory scale flammability characteristics - Requirements and test method", which is based on a European standard and subsequently published by the International Organization for Standardization (ISO), describes a method for assessing the response of a conveyor belt to an ignition flame source on a small scale. This method is valid for conveyor belts with textile carcasses and conveyor belts with steel cords.
For the purposes of this standard, the following terms and definitions apply:
The requirements in this standard are explained as follows:
Ignition and combustion of polymer materials during testing may cause the release of smoke and toxic gases that may affect the health of operators. Therefore, it is of great importance to provide appropriate means to clean the test area from smoke and fumes.
It is important to be aware of all relevant local safety regulations for the handling and storage of liquefied petroleum gas (LPG) and the disposal of used LPG containers. If local safety regulations require LPG cylinders to be stored in an environment cooler than the test area or at a certain distance from the test platform, a sufficient length of tubing is required within the controlled environment to allow the gas to equilibrate to the required temperature prior to flow measurement. One way to facilitate this is to pass the gas through a metal tube immersed in water held at 25 degrees (prior to flow measurement).
In principle, a test piece cut from a conveyor belt is suspended vertically over a gas flame for a specified time, after which the gas flame is removed. The post-flame time is measured. Any re-ignition is noted when the test piece is then exposed to a stream of air.
The test pieces should be taken at a distance of at least 50 mm from the belt edges. When testing textile carcass conveyor belts, 200 test pieces, each 5 mm plus/minus 25 mm × 1 mm plus/minus 12 mm, are prepared for tests on conveyor belts with and without covers as follows:
The covers may be removed by peeling, cutting or polishing. If the covers are removed by polishing, care should be taken not to overheat the test piece or damage any threads of the textile carcass. The covers of textile conveyor belts should be removed from both sides. This is usually achieved when the top of the fabric joints is continuously visible for the majority of the sample area, exposing only the non-greasy material. The joints should not be damaged or frayed.
For tests on conveyor belts with covers intact, if the product specification requires that the tests be performed on conveyor belts with covers intact, only six test pieces shall be performed as described herein. For tests on conveyor belts designed for use without covers, if the product specification requires that the tests be performed on conveyor belts developed for use without covers, only six test specimens (three longitudinal test specimens and three transverse test specimens) shall be taken and tested from the conveyor belt (measuring 200 mm plus/minus 5 mm × 25 mm plus/minus 1 mm). Since these conveyor belts are designed without covers, no material shall be removed from the conveyor belts.
For tests on steel cord conveyor belts with covers intact, if the product specification requires that the test be carried out on conveyor belts with covers intact, six test pieces, each 200 mm plus/minus 5 mm long and as wide as possible from 3 to 25 mm depending on the cord diameter and pitch, are cut in the longitudinal direction of the belt. Each test piece shall be at least 20 mm wide and contain at least two cords; the cut edges shall represent the centre line between adjacent cords.
For tests on conveyor belts with covers removed, if the product specification requires testing on conveyor belts without covers, cut six test pieces as described herein and remove the covers by stripping, cutting or polishing. The covers of steel cord conveyor belt specimens shall be removed from both sides, leaving the surface of the steel cords of the conveyor belt specimen exposed.
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