Winning business
Table 1
Example of mobile text warning messages based on a South African Weather Service cell covering a mining operation in Mpumalanga. Clearing of the blasts that were being prepared was necessary between 14:17 and 15:54.
+ 2 BME: 20120309 15:54 Lightning 31 minutes clear. Date sent: 09 / 03 / 2012 15:54:00
+ 1 BME: 20120309 15:39 Lightning 16 minutes clear.-25.0KA Direction: 11km North West. Date sent: 09 / 03 / 2012 15:39:00
+ 0 BME: 20120309 15:23 Lightning Current Danger-25.0KA Direction: 11km North West. Date sent: 09 / 03 / 2012 15:24:00
+ 1 BME: 20120309 15:21 Lightning 16 minutes clear.-11.0KA Direction: 15km West North West. Date sent: 09 / 03 / 2012 15:22:00
+ 0 BME: 20120309 15:05 Lightning Current Danger-11.0KA Direction: 15km West North West. Date sent: 09 / 03 / 2012 15:06:00
+ 1 BME: 20120309 15:05 Lightning 16 minutes clear.-20.0KA Direction: 15km West. Date sent: 09 / 03 / 2012 15:05:00
+ 0 BME: 20120309 14:17 Lightning Current Danger-17.0 KA Direction: 14km West South West. Date sent: 09 / 03 / 2012 14:18:00.
Lightning is a phenomenon that almost daily affects drill and blast operations globally during the summer rainfall months.
This system works on a statistical detection base and does not predict the dangerous positive strikes that usually occur ahead of a storm or at the trailing end. This and most other systems function on the basis of detecting actual strikes, but cannot predict a nearby strike. This results in over-conservative reaction and a large negative impact on productivity, or, warnings are ignored because so many of them are issued.
Detection technology is based on electromagnetic( EMF) disruptions in our atmosphere. This is what generates the static noise that is picked up by AM radios. This technology can only determine the distance between your location and the location of a lightning strike that has happened. Detection systems show where lightning is happening and estimate where it is likely to go. Detection systems will give an all clear after a certain amount of time. So a significant amount of time is wasted when the pit is cleared and most often, the alarm is a false one.
Technology that provides a more reliable prediction of an impending strike— rather than detecting what has already happened— is used in many mining operations, golf tournaments, and other lightning sensitive businesses. An example is the system presented by Quinn( 2011).
The electrostatic potential that builds up in an area of a strike is a good determinant of a likely strike. An effective prediction system, using an array of sensors around a pit, can
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BME
The author Tony Rorke, technical director of BME.
measure this potential to provide reliable prediction of an impending strike.
Storm direction trends and strike patterns are useful to know and they provide some measure of warning that is useful for raising the alert level, but prediction technology should also be used when deciding when to clear people to safety. The two work well hand-in-hand and can provide real safety against lightning strikes while lost time is minimised. n
References
1. Quinn, G. 2011. Lightning warning technologies for the mining industry. Understanding the hazard, managing the risk. 2011 Annual BME Conference, Johannesburg.
2. Santis, L. D. 1998. The calculated risk of experiencing a lightning-caused unplanned detonation. 14th annual symposium on explosives and blasting research, ISEE, New Orleans, US.
3. Lownds, C. M. and Lindenhau, J. 2008. Electronic detonators and lightning. International Society of Explosives, vol. 2, Dallas, US.
4. Steiner, U. and Lownds, C. M. 2009. Electronic detonators and lightning. International Society of Explosives, vol. 2. New Orleans, US.
5. Gill, T. 2008. Initial steps in the development of a comprehensive lightning climatology of South Africa. Submission for MSc thesis. University of the Witwatersrand.
6. South African Weather Services, www. weathersa. co. za( 2012).
About the author
Tony Rorke is director of blasting science at BME.
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