Fire resistant rubber conveyor belts: what they are, which tests they are submitted to and their application

At the end of this period, the flame is removed and the necessary time for flame extinction is measured. The test can show a positive result and then the conveyor belt is classified as self-extinguishing when:

• the flame extinction time for six samples results in no more than 45 seconds;
• the time needed to extinguish a single sample flame cannot exceed 15 seconds;
• subjected to the air stream, the samples must not show any new flame formation.

After completing a test like the one just described above, if all results are positive as required, a belt can be considered 100% self-extinguish.

To summarise, AG cover rubber provides superior resistances to vegetable oils and animal fats meanwhile being self-extinguished and antistatic according to ISO 340 and ISO 284 to guarantee high safety to the conveyor plant.

Grain storage silos and port terminals for ship loading and unloading operations are the industrial fields where the AG rubber compound is mainly used.

SIG's Case Studies for AG & BS rubber compounds in 2022-2023

Up to this moment, you have been given many technical details about SIG BS and AG rubber compound, also having the chance to learn useful information about the test through which it is possible to check the self-extinguish feature.

Now, SIG's reference list will be a valid ally to make you learn about some iconic accomplished supplies of AG and BS rubber compound belts to give you concrete evidence of what claimed up to this moment.

Fertilizers port terminal Project: EP belt with fire-resistant rubber covers

In 2022, a French engineering company was in charge of completing fertilizers terminal for ship loading and unloading operations for an Asian seaport authority.

Since one of the handled material’s features was its flammable dust, from the very beginning it was clear that supplied goods would necessarily be self-extinguish and antistatic to minimize any safety risk for workers connected to a potential fire ignition and propagation.

Consequently, when the OEM company contacted SIG for this project, the choice over which type of rubber conveyor belt to be supplied immediately went on EP carcass rubber conveyor belt, equipped with BS rubber compound.

Thanks to SIG technical department's useful suggestions, the following constructions were agreed upon: more than 3km of EP belt, 1200mm wide, with 6mm on the top cover and 2mm on the bottom one, equipped with self-extinguish and antistatic rubber covers (matching with K degree) and with a breaking load of 630 N/mm, composed of 4 plies.

Plant installation and commissioning ended in December 2023.

Nowadays, both the French engineering company that delivered the whole conveyor system and the ending customer (seaport authority) are fully satisfied with the rubber conveyor belt performances, loading and unloading fertilizers from January 2024.

Are there any other specific flame-resistant rubber compounds inside SIG range of products?

At the moment, you have had the chance to deal with self-extinguish rubber compounds for above ground applications, nevertheless, in the rubber conveyor belts industry it may happen that some activities have to be carried out inside underground areas or tunnels as well.

Specific standards norming industrial activities with risk of a potential fire propagation mention that for any undeground installation rubber conveyor belts must be equipped with a special rubber compound that prevents the item from being a source of fire. In this case, the main principle is not only smothering the flame in a very short time, but to avoid fire propagation.

When facing such an application, standard self-extinguish rubber belts at the ones recently described cannot be used since they could not match the strict safety requirements that are required and necessary for undeground applications.

As a matter of fact, any belt that may be installed inside an underground application must not be an active fire spreader, so a different concept if compared to self-extinguish as in the first mentioned cases, as in this case the belt must avoid any potential fire propagation.

TS RUBBER QUALITY

TS is produced with a specific rubber compound that has been designed to service both underground and above ground applications. It is highly recommended for the belt conveyors located in the back areas of the tunnels. TS is designed according to DIN 22102 S grade, ISO 340 and ISO 284 or equivalent.

This is a special option as in this case, not only belt external covers, but also inner rubber, the one used to guarantee a better adhesion between plies and belt structure, must be self-extinguish. Therefore, the test to check the actual and real main feature is not only carried out on an external covers sample, but also on a piece of inner carcass.

TV RUBBER QUALITY

This technologically advanced option has been designed to work in underground applications where it is necessary that the belt does not trigger centres of fire. It is recommended for the belt conveyors located close to the permanent workstations in underground applications or tunnels. TV is designed according to ISO 340, ISO 284, EN 14973 or equivalent.

Dealing with TV rubber compound means that it is necessary to cope with two new different tests:

• friction test
• gallery test

The two just-mentioned tests can be carried out with different parameters and regulations to be matched, according to the level you are referring to.

To give you some more information about gallery test, a rubber conveyor belt sample (not only a small piece in the case of self-extinguish belts) is exposed to an active source of flame and placed inside a gallery (tunnel) where it subjected to a continuous air flow increasing fire action.

A positive result is shown when once this the heat source is removed and the flame becomes extinct, there is still a belt region completely undamaged. This experiment has to prove that when the flame source is withdrawn, the belt will not be an active fire spreader, preventing its propagation clearly leaving undamaged belt regions (that can have different sizes according to the test level you are referring to.)

Do not waste precious time and get in touch at sig@sig.it to ask for a quotation or to simply get SIG technical department support to study the most suitable rubber conveyor belt for your needs.