Banda,

You have asked a broad range of questions.

1) Selecting a fire resistant belt to DIN K specification will reduce the risk, not eliminate the risk. You can by being careful how you specify your belt, ensure that the K covers have similar wear characteristics to an Y or X cover providing the material size is under say 50MM. The penalty therefore only becomes price.

2) In a tunnel application you need to identify your sources of any fire risk and think through the appropriate solution. For instance is it at the transfer due to say friction between the belt and the skirt or due to build up. Can this be modified by design and can safety be enhanced by using fire resistant rubber on the idler discs and skirts.

3) Detectors alone are not the answer as they are usually only activated after belt and potential fire damage are advanced.

Colin Benjamin ■

Dear Banda,

This topic has been commented on before in this forum. I can recall discussing our support to BHP Port Hedland for the under-the-sea tunnel conveyor.

We designed a sensing and deluge system for the principle fire initiation points, the idler bearings. We referenced the use of Protect-O-Wire, as the annuciator of bearing overheating, and a zone controlled water manifold/valve system to apply a spray to each bearing point (4 spray heads/carry idler and 3 for Vee-return).

Protect-O-Wire is used on many power plants, and in particular, in the tunnel reclaim facilities. THe principle is to use a twisted wire pair separated by an insulator. When the wire is subjected to heat that can melt the insulator, a contact is made, and the system can define the specific location to initiate spray or foam. The concept can also be used at drive and transfers along with other sensors. The concept provides its own power within the sensor/annunciator so that it is reasonably efficient and cost effective. ■

Assume that personnel in overalls & safety footwear can possible run at 6m/sec in an emergency, over a short distance; then assume that even the best systems can & do fail. If you have wet coal you might also have methane: get your ventialtion direction right & then consider how far apart your exits & stiles must be. Protecting equipment is always secondary to safe plant layout. ■

Dear Banda,

The question should also relate to the fumes emitted during a fire.

It is common knowledge that the fumes emitted from a belt having fire retardant properties are more damaging than those for non-fire resistant belting. Thus the 'deluge' system as per Mr Nordell and efforts on prevention are probably the best preventitive measures. Note that we had a fire in an underground tunnel of a platinum mine recently in South Africa. Fatalities resulted. The apparent cause of the fire was a jammed pulley due to bearing collapse.

Regards,

Adi Frittella

AFRIPP PROJECTS CC ■

Banga Hi,

I see that others have given you ideas how to prevent a fire along a conveyor belt.

From my job experience as a fire engineer working on mine sites in Australia and having done numerous risk assessments on this subject finding the possible ignition souces and then an appropriate solution to prevent the fire from growing is youe top priority.

Firstly Id like to offer my services for this if you think it is required. you can contact me and we can discuss this issue in greater depth.

Secondly I am looking for information and statistics of coal conveyor belt fires over the last 20 years, world wide can somebody point me to web site where i can find this info

thanks

Daniel ■

House keeping is number one as I have mentioned on previous posts.

Most conveyor belts manufactured have a fire resistance rating,

this entails a flame resistance time rating, conveyor belts will smoulder go to smoke create huge amounts of smoke and then melt apart from fire.

As mr. Nordell has mentioned a deluge system is also best in my opinion.

As has been mentioned by Mr. Gately egress and system design is the major concern and maintaining same. In the event of a belt fire or any other fire under ground one must worry about a fire of any type mushrooming with a flash over and reignition from air entering the tunnel.

My question to you is how is the tunnel constructed?

are personell required to operate ore passes?

Is this tunnel of cut and cover construction under stock piles?

No matter the construction of the tunnel whether it is underground in a mine or under stock pile a fire if uncontrolled or unstopped will cause a roof failure from heat damage.

Is a storage tank or lagoon for fire control water in your design or

available?

Testing the fire control system on a regular basis is a necessity!

A deluge gun or sprinkler system will continue to deliver water until it is turned off or runs out of water.

A conveyor belt fire will happen anywhere on the belt line. for a number of reasons such as frozen idlers, ripped belt, frozen tail pulleys, defective speed switches, worn lagging, uncleaned belt spills and belt overload to name a few.

If tail pulleys are not kept clean by shoveling or vacuuming they are a huge cause of fires due to friction. ■