EN 12882 Conveyor Belts for General Purpose Use - Electrical and Flammability Safety Requirements

A European standard, “EN 12882 Conveyor belts for general purpose use - Electrical and flammability safety requirements”, describes the electrical and flammability safety requirements for general purpose conveyor belts not intended for use in underground installations and provides a means of categorizing conveyor belts in terms of the level of safety required in end-use applications.

This standard does not provide electrical safety requirements for volume resistance, which can be measured by the methods in EN ISO 21178 Lightweight conveyor belts - Determination of electrical resistances and is applicable to certain lightweight conveyor belts. This standard is not applicable to conveyor belts manufactured before the publication date of this standard.

Directive 94/9/EC, which relates to equipment and protective systems designed for use in potentially explosive atmospheres, is applicable to the type of machinery or equipment covered by this European standard. The present standard does not intend to provide means of complying with the essential health and safety requirements of directive 94/9/EC (this is covered in standard EN 14973).

The EN 12882 standard is not a product standard, but is intended to assist users of conveyor belts in selecting the necessary electrical and flammability safety features they require after an appropriate risk assessment. Therefore, no requirements are included for marking and information to be provided. These issues are addressed in the relevant product standards EN ISO 14890 and EN ISO 15236 1.

For the purposes of this standard, the following terms and definitions apply:

• Afterflame refers to the flame that continues even after the ignition source is removed.
• Afterglow is the continuation of a glow after the ignition has ceased or, if no ignition occurs, even after the ignition source has been removed.
• Flame refers to the combustion zone in the gaseous phase, usually with light emission.
• To ignite means to undergo combustion with the emission of light in the gaseous phase.
• It refers to light that glows and is illuminated by heat (without flame).
• Intact is that part of a conveyor belt which remains after termination of the propane gallery fire test, as defined in accordance with EN 12881-1, and which shows no evidence of brittleness, cracking, swelling or other defects not originally present.

In this standard, the security requirements are described as follows:

• General: Conveyor belts in each category must meet the test requirements given in the standard and specified in the specific subclauses below.
• Electrical conductivity:
  • When tested in accordance with EN ISO 284, the electrical surface resistance of all general purpose conveyor belts must not be greater than 300 MΩ.
  • Lightweight conveyor belts described in EN ISO 21183-1 must not have an electrical surface resistance greater than 21178 MΩ when tested in accordance with EN ISO 300 unless the conditions described in this standard are met.
  • Lightweight conveyor belts with an internal conductive layer must not generate an electrostatic charge resulting in a surface potential greater than 21179 V when tested in accordance with standard EN ISO 1000.

Under special service conditions, higher electrostatic charges can be generated, resulting in surface potentials in excess of 1000 V, due to friction between the belt surface and the goods being conveyed or due to friction within the goods being conveyed, such as non-conductive bulk goods such as sugar, flour or plastic granules. The safety requirements in this standard do not take into account such critical service conditions, but only the operation of the empty light conveyor belt and the electrostatic charges it generates.

In certain cases (e.g. in the transport of electronic components), it may be necessary to dissipate electrical charges through the belt. This requirement can be specified in terms of volume resistance measured by the method described in EN ISO 21178. However, the safety requirements in this standard do not take into account the volume resistance of light conveyor belts for the assignment to different safety categories.

• Flame retardancy:
  • When conveyor belts in category 2A or 3A are tested in accordance with EN ISO 340 with their covers intact, the sum of the final flame duration for all six tests must be less than 45 seconds and no individual result must exceed 15 seconds.
  • Conveyor belts in categories 2B, 3B, 4A, 4B, 5A, 5B and 5C, when tested in accordance with EN ISO 340 with covers intact and covers removed, shall have the sum of the afterflame duration times for each of the six test groups (i.e. six tests with covers closed).
• Fire simulation:
  • When tested in accordance with method A, C or D of standard EN 12881-1, conveyor belts in categories 4A and 4B, 5A, 5B and 5C must maintain the undamaged conveyor belt length specified in the table.
  • The test methods in accordance with EN 12881-1 are not applicable to lightweight conveyor belts as described in EN ISO 21183-1. Therefore, lightweight conveyor belts can only be assigned to categories 1, 2A and 2B.
• Drum friction:
  • Conveyor belts in categories 1554A, 1B and 3B, when tested in accordance with method B3 of EN 4 standard, shall exhibit no flames during the test lasting 60 minutes or until the belt breaks, whichever is shorter.
  • Conveyor belts in category 1554A, when tested in accordance with method B2 of EN 5 standard, shall not exhibit any flames during the test lasting 150 minutes or until the belt breaks, whichever is shorter.
  • When tested in accordance with method B1554 of EN 2 standard, conveyor belts in category 5B shall not exhibit any flame or glow throughout the test lasting 150 minutes or until the belt breaks, whichever is shorter.
  • When tested in accordance with method B1554 of EN 2 standard, category 5C conveyor belts shall not exhibit any flames or glows throughout the test lasting 150 minutes or until the belt breaks, whichever is shorter, and the drum temperature shall not exceed 400 degrees at any time during the test.
  • The test methods in accordance with the EN 1554 standard are not applicable to lightweight conveyor belts as described in the EN ISO 21183-1 standard. Therefore, lightweight conveyor belts can only be assigned to categories 1, 2A and 2B.

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