Do you have conveyors?? Get them protected!
Have you ever thought of what damage a fire can do to a conveyor? It is very easy for a conveyor belt to start burning due to friction from misaligned belts, overheated motors, burning material on the belts and even arson.
This can have disastrous effects to a mine, not only the money and time that gets lost due to the shutdown to repair the conveyor, but more importantly, that people’s lives are at stake. The effects can be seen in the following picture:
Therefore we would like to share the perfect system with you…
The system entails a fire detection system which works together with a water suppression system a.k.a a deluge system in each protection zone. This zone normally extends to 40 metres and is situated at the head pulley and tail pulley of a conveyor.
Fire Detection System
The typical fire detection system per zone consists of the following devices:
• UV/IR Detector
• Linear Heat Detection Cable
• Conventional Fire Control Panel with batteries
• Combination Strobe/Sounder
• PH30 Fire Resistant Steal Wired Armored Cable
The UV/IR Detector and Linear Heat Detection Cable each represent a fire zone in a particular fire protection zone on the conveyor belt, hence Zone 1 is the UV/IR detector and Zone 2 is the Linear Heat Detection Cable. Both of these devices are connected to the fire control panel of which a 2 zone panel will be suitable. The devices are all joined with the fire panel through steal wired armored cable which has a fire resistance of 30 minutes. We then also install a Combination Strobe/Sounder near the panel that is installed at the specific zone, this device serves as a warning to personnel in the area should a fire break out. Each fire control panel has a potential free contact which activates on the detection of fire on Zone 1 or Zone 2. This is the contact that we use to trigger the water suppression system by converting the potential free contact into a 24VDC switch.
Water Suppression System
This system consists of the following:
• Fire Water Pumps
• Fire Water Tanks
• Galvanised or Red Painted Main Pipes
• Deluge Valve Station
• Range Pipes with Medium Velocity Nozzle
We install pumps with the correct capacity water tanks, for which the size and specification are calculated via specialised programs to meet the relevant standards. The deluge valve station is then connected to the main fire water line that is coming from the pump house. In this case the valve is triggered electrically from the detection system. When triggered, the water sprays through the nozzles onto the conveyor belt and thus extinguishes the fire.
It is very important that the UV/IR detector is installed before the fire protection zone and not behind. We have noticed before that a contractor had installed the detector behind the zone which would not enable the water to extinguish the fire. What is the purpose of having such a system installed? A total waste of money and the risk is still there! It is also important to trip the conveyor upon detecting the fire so that the affected area stops in the zone where the nozzles are and therefore will be extinguished speedily. This can be achieved by interfacing the PLC system of the mine with the fire control panel. That is why we recommend that the detector faces towards the oncoming direction of the conveyor belt so that the belt stops in the zone. The momentum of the belt when tripping it, will move the fire into the fire protection zone. The Linear Heat Detection Cable is mounted above the conveyor belt to ensure the effective detection of heat. The nozzles of the water system also need to face the conveyor belt to make sure the total area of the belt is covered.
If you have the above system with a maintenance plan in place you do not need to have sleepless nights about insurance claims and fire related deaths or injuries. Please note that we normally recommend Ember detectors at Coal Mines instead of the UV/IR detectors.
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Arno van den Berg