Coal Inspectorate | Bulletin | No.205 V 1 | 07 October 2022

Risk management during lightning events

Operational risk during lightning events

Lightning conditions during storms create hazards that need to be managed by operators to ensure that risk to workers remains at an acceptable level. RSHQ’s resources safety acts require that risk from operations must remain at an acceptable level at all times and that steps should be taken to eliminate hazards where it is reasonable to do so.

The safest way to eliminate hazards related to lightning conditions is to cease activities when lightning is detected within close proximity to a work site.

RSHQ recently commissioned an expert review to consider the hazards arising from conducting operation during lightning activity and their relative risk to the safety of resources workers.

Hazards arising when using vehicles during lightning conditions

The report identified 10 hazards relating to the use of vehicles during lightning conditions. Each hazard has been assessed to establish the qualitative change in risk from the standard situation where work ceases and workers remain in a safe shelter until the lightning activity has passed.

Each of the below hazards should be considered by operators when conducting risk assessments for carrying out surface activities during lightning activity.

Considerations for high and moderate increase hazards

The information below should be considered by operators in relation to assessing hazards identified as having a high / substantial or moderate risk increase when operations continue during lightning activity.

In each case, the best control to ensure risk to workers remains at an acceptable level is to cease work, park vehicles up in a safe location away from workers and ensure workers remain in a safe shelter that has been designed with lightning protection systems to industrial standards, such as AS1768:2021, until lightning has ceased.

1) Exposure to high voltage while in close quarters to - but outside of - vehicles

Remaining outside a vehicle cabin, but in close proximity to the vehicle, creates additional hazards, including:

• touch potential: can occur when a worker touches an electrified object, including the ground
• step potential: can occur when a worker is standing or walking on ground that carries electrical current
• side flash: can occur if lightning strikes a vehicle when a worker is in close proximity

2) Exposure to high voltage while in an open area

Workers who remain in open areas during lightning activity are exposed to a significant risk of a direct lightning strike. They may also be exposed to step potential and flash injuries if they seek unsuitable shelter (such as under a tree).

3) Tyre rupture or explosion via pyrolysis 

Lightning strikes can cause pyrolysis-related tyre explosions. Tyres inflated with nitrogen have a similar risk profile to air-inflated tyres and the use of nitrogen fill in haul truck tyres is not considered to be a reliable means of reducing the risk of tyre pyrolysis and explosions due to:

• chemical degradation which can occur in a deoxygenated or low oxygen atmosphere, meaning that flammable gases can still occur
• the control measure of ensuring oxygen is maintained below 5% is effective, but requires strict implementation measures, including purging tyres prior to filling, filling with high purity nitrogen, not topping up with air in the field, and quality testing oxygen levels in tyres
• delayed explosion risks which can be present in tyres that have been ruptured (resulting in them becoming unseated) due to a lightning strike. Unsealed tyres continue to represent a risk of explosion.

4) Risks to workers whilst inside cabs of vehicles

Vehicle cabins are not perfect Faraday cages, meaning that a worker is still at risk of serious injury or death if they remain within a vehicle during an active lightning event. This is because:

• window openings (non-conductive areas) on worksite vehicles are usually large which increases the risk of direct lightning strikes
• contact with window openings or devices containing metal that are connected to, or near, the outer shell of the cabin (such as the steering wheel, brake pedals, gear handles and actuating levers) poses additional risk of touch potential
• operating vehicles with open windows can increase the risk of injury from touch potential and side flash.

Risk to emergency response personnel

Emergency response personnel are exposed to additional hazards when responding to incidents and accidents at mine sites as they are more likely to be required to leave their vehicles to carry out their duties. This increases their risk of exposure to being struck by projectiles or exposed to high voltage from direct strike, flashover injury, touch potential and step potential.

Recommendations

Assessment of the risk of conducting operations during lightning events is site dependent. However, at a minimum, the following controls should be considered as part of a risk assessment process and implemented unless alternative controls can be demonstrated to ensure risk to workers is managed to an equivalent level:

• operations should cease when lightning is detected within an appropriately determined distance from the worksite
• vehicles should be driven to a designated safe lay-down area
• operators of vehicles should be transported to a safe shelter away from the equipment
• workers should not return to work until an "all clear' has been given.

Site Senior Executives should review all components of the site’s Safety and Health Management Systems that relate to conducting operations during lightning activity to ensure that risks to workers can be managed to an acceptable level at all times.

The review should consider each of the hazards identified in this safety bulletin. Risk assessment processes should be conducted with a cross-section of the workforce responsible for performing the tasks that are being assessed and participating workers should be fully informed about the hazards and resulting risks to workers arising during lighting events.

RSHQ inspectors will be conducting audits during storm season to ensure that all sites have identified and implemented appropriate controls to manage risk to resources workers to an acceptable level during lightning events.

Authorised by

• Shaun Dobson, Chief Inspector of Mines - Coal
• Hermann Fasching, Chief Inspector - Mineral Mines and Quarries and Explosives
• Bill Date, Chief Inspector - Petroleum & Gas