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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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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