Kayem,

Conveyor Dynamics, Inc. has been involved with a number of tunnel conveyors for iron ore, copper ore, coal, platinum, gold, ....

THere are a number of alternatives to fire resitant belts. Usually, the belt is a key artery for plant production. THe transport tarrif justifies appropriate detection and correction as I noted in your request on fire protection on overlands.

Usually, the client ops for water deluge (correction) based on fire detection by sensor. THis can be smoke detectors or thermal.

THe thinking is that idler bearing seizure and grease fire is the most likey cause. Thus, detect the bearing by the local heat sensor and trigger local water spray. CDI aided in the design of such a system for BHP Australia for a under-the-sea iron ore conveyor.

IN South Africa, Rio TInto and Anglo-American have installed localized water deluge with overhead heat and smoke sensors.

Lawrence Nordell

Conveyor Dynamics, INc.

www.conveyor-dynamics.com ■

Another Point:

Fire retardant belts usually have a much shorter life expectancy due to the natural degradation of the rubber compound. Eight to ten years as opposed to 15-20 years or more for tunnels with little ozone. Thus, the economics of belt life is a deterent to their use in hard rock.

Lawrence Nordell ■

Dear Mr. Kayem,

The fire resistant belts wear resistance is remarkably less compared to usual belts. This difference could be as high as 25% to 35%. Therefore, fire resistant belts should be used where application really demands for the same, because it amounts to higher operating / replacement cost of belt. Firstly, the belt is costlier and it also needs the replacement faster, so the effect is cumulative.

The fire hazard or possibility of fire is subjective issue and should be always seen with reference to the context. If the plant is maintained / run properly, strictly as per the engineering needs, then chances of fire will be less. However, if the quality of components and operating people is poor or careless, then possibility of fire and accident increases.

In application like coal mine where inflammable cases are likely to be present, there fire resistant belt is a must. If the belt conveyor is conveying inert material like iron ore and if there is no presence of inflammable gas then need for fire resistant belt will to some extent depend upon length of tunnel etc. In case, the fire occurs in such enclosed location then it will create suffocating atmosphere. One has to also see the options available for the escape. Generally, for conveyors dealing with non-inflammable material and where inflammable gases are not present, then genuinely there is no reason to use a fire resistant belt in such situations. However as said before this is a subject issue and if the buyer is very sensitive to this matter, then he may spend money and opt for fire resistant belts.

One has to also see the statutory regulations as applicable to the specific installation and insurance terms conditions while making the decision.

Fire hazard is also like a present day word “perceived threat of fire”.

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyors.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■

Kayem,

Mr. Mulani indicates the fire resistant belts suffer from higher wear rates. This is only true if the chute design produces undesirable shear work of ore on belt at the point of loading.

Modern chutes can most often vertually eliminate abrasive wear and impact puncture damage at the ore loading point. If this is true, then wear is not an issue. Rubber strength does degrade and splice strength does dropl with time.

Another fire correction action is to use zoned fire retardant foam. Similar to water spray, foam is discharged into the region where significant heat and smoke are detected. THe foam is applied in a local region, like a gate, that inhibits oxygen. The fire will extinguish when starved of oxygen. It is not applied over the full length of each conveyor region that is zoned for detection.

Lawrence Nordell

Conveyor Dynamics, Inc.

www.conveyor-dynamics.com ■

kAYEM,

Having been on many HAZOP team assessments, I concur, that standard natural grade rubber will prevail over flame redardant belt for iron ore transport in a tunnel.

There are risks in all conveyor belt systems. Fire is just one such risk.

Operators, for the most part are given the choice during the design stage to implement a fire retardant belt or not. HAZOP program studies show that having a belt last +15 years made with flamable material is superior to having multiple replacements using non-flamable rubber belt and their risk factors. Fire prevention, detection and correction is delt with in alternative ways to using fire retardant belt as have been noted.

Other factors in HAZOP assessment becomes issues, as the fire retardant belt wears thin, it may lead to premature splice failures.

Note, fire retardant belt produces a carcogenic product when burnt and fires do ocurr independent of the belt type.

Lawrence Nordell

Conveyor Dynamics, Inc.

www.conveyor-dynamics.com ■