Lightning: What's the story - Simon

Lightning, “What’s the story?”September 2014

WealthUnearthed

Simon Tose – Global Mining Optimisation Manager

“Lightning, What’s the story?”

• Unusual number of incidents in Africa past 2 years

• Multiple hole events

• No major change in weather patterns

• Quoted research 10 to 20 years old

• Electric & Old technology

• Published articles conclude that a direct lightning strike on a single charged hole could cause an event

• Hence regulations/safety policies require evacuation of blast area when storm approaches

“Clouds, Lightning, Airlgow and Lights of Civilization in Africa” by NASA

Lightning…

• Lightning is a massive electrostatic discharge

• Within clouds

• Between a cloud and the earth

• Commonly referred to as a strike if it hits an object on the ground

• It is estimated that an average bolt of lightning carries:

• An electric current of 30000 amperes (30kA)

• Transfers 15 coulombs of electric charge

• 500 megajoules of energy

• Useless fact: enough energy to toast 100000 slices of bread…

Storm season approaching

• 250 people are killed by lightning in South Africa each year

• SA Weather Service

• In perspective 15000 are killed on our roads

• That’s 1 person in the half hour of this presentation

• Arrive Alive

Lightning Ground Flash Density Map- Southern Africa - CSIR

Commonly accepted risk to an individual being hit by a lightning strike

Around 1 in 10 million

Parts of South Africa

Around 1 in 650000

Risks to avoid…

• Open areas like soccer fields, golf courses, or parking lots

• You are the tallest thing around and the easiest target

Risks to avoid…

• Stay away from forms of metal

• Lightning is electricity and metal is a conductor of electricity

• Stop swimming and get away from water

• Water is a conductor

Risks to avoid…

• Don’t fly kites

• Don’t stand under tall objects like trees or towers

Risks to avoid

• Don’t carry an umbrella

• Better to get wet…

Review of recent mining papers…- Impact on people, equipment and infrastructure

International Society of Explosive Engineers, ISEE

“Mining world wide has been impacted by significant lightning-caused production delays and safety issues”

Mine-wide mobile radio communications fail following a lightning strike to a central radio tower

Surge protection is absent (Canada)

Five maintenance workers are injured when lightning strikes a stationary vehicle

The lightning early warning system is low cost and old technology (Peru)

A central computer system is damaged by a lightning strike, important geological data is lost

Grounding methods are in violation of codes and standards (Ghana)

More than $US one million is spent on some 350 unconventional-design lightning rods. The product is not approved by USA or international lightning protection codes and standards

Safety to all buildings is compromised (Peru)

Miners are killed when lightning explodes methane gas inside a subsurface mine. A comprehensive approach to lightning safety is absent

Many hundreds of deaths in coal mines in China, Russia, & historically USA

Tumbler Ridge, B.C.

• On July 15, 2012

• Driver of 777F haul truck was parked at the 1135 waste dump waiting out an electrical storm

• Truck was struck by lightning causing significant damage to the rear of the truck

No operator injury when this D-‐‐‐‐9 Cat took a

direct lightning strike, Peru

Review of recent papers…- Impact on people, equipment and infrastructure

Four of eight gas turbine generators suffer lightning-induced failures, production losses at the mine are $600,000/day

Power shortage lasts three months

Earthing is poor (Papua New Guinea)

Lightning causes failure of a primary water pumping system, underground flooding closes the mine for 45 days

Surge protection was absent (South Africa)

A smelter operation is “frozen” after lightning hits a substation

164 pots have to be dug out by hand, production is shut down for seven weeks

Earthing is poor (USA)

A large haul truck is struck by lightning with consequential tire explosion. Grenade like fragments kill two workers (Mexico)

A mine superintendent standing outside during a thunderstorm is killed by lightning, he ignored weather warnings (Australia)

A radio operator inside a building is killed by lightning

Grounding is poor (Indonesia)

Two workers are killed, with seven injured in two separate incidents

There is no employee lightning safety training (Laos)

Two exploration crew members struck by lightning are airlifted to hospital

The lightning detector fails to warn of threat in time for evasive action (Haiti)

NSW Department of primary industries

• Large rear dump truck (RDT) was struck by lightning while stationary and unattended. No employees or personnel were injured. September 2010

NSW Department of primary industries

US Mine Safety and Health Administration (MSHA)

• Statistics show average of ten recorded premature blasts per annum

• Two related to lightning

• Based on 4500 mines operating in the US

• Mining Journal online

• The chances of a blasthole being struck directly by lightning are less than that of a direct strike on a person

On an open bench in the mining area…

• Most exposed to a risk of being struck by lightning

• Aside from the equipment

• It is obvious that its people

Water

Lightning warning systems

• The rule of thumb, in the absence of such a system, is to withdraw when the interval between a lightning flash and the thunder is less than ten seconds. This represents about 3.5km

Campbell Scientific

Lightning Safety for Outdoor Worker recommendations

Detectors are to be monitored continuously

If thunder is heard, suspend operations

Notify all affected personnel via radio, texting, voice, sirens, etc.

Three stage Alert Program:

Yellow at 30-60 km radius

Orange at 16-30 km radius

Red at 0-16 km radius

Re-Assess threat

Sound All Clear

After one half hour of no thunder or lightning

Single blasthole

Unwise to state that a direct lightning strike could not initiate a single blasthole

Due to the energy contained within the lightning

The many sensitive explosive components particularly within the detonator and booster

However with the rapid decay and loss of energy from the ground strike

Difficult to explain the propagation by direct conduction through the rock to multiple blastholes

Typical burden and spacings make it very unlikely for sympathetic detonation

AELs experience – Shocktube

No detonations have been recorded

Experienced melted tubing

The only instance was an instantaneous electric detonator, IED

Fastened to the connected shock tube layout on a fully charged blast

Obvious cause was the high voltages and currents pushed through the ground by the lightning

Resulted in initiation of the whole blast

AELs experience – Electronics- No Initiation of blasts

A number of direct lightning strikes

Resulting in some instances in the failure of the units and melted cables on surface

• Operating and supplying explosive and initiating products to 1000’s of monthly blasts, mining types and countries

• We have not had a single lightning strike be implicated in the cause an unplanned initiation of explosives

AELs experience, since introduction of electronics

Lightning, “What’s the story?”September 2014

Thank You