Zoning Systems: Controlling the Risks of Operating Tower Cranes Near Powerlines

by | Aug 18, 2021 | Featured Posts, Tower Crane Hire Safety in QLD | 0 comments

Zoning Systems Controlling the Risks of Operating Tower Cranes Near Powerlines
Zoning Systems: Controlling the Risks of Operating Tower Cranes Near Powerlines

This post was originally written by Ryan Graham from Work Safety QLD and posted on Falcon Cranes website. 

In this post we will outline the main risks when operating a tower crane near overhead power lines, and how we mitigate or eliminate these risks at Falcon Cranes.

What are the risks of Operating Tower Cranes Near Powerlines?

Contact with overhead electric lines can be fatal regardless of how high the line voltage is. In addition, making physical contact with overhead electric lines is not necessary for an electric shock to occur. A close approach to the line conductors may allow a ‘flashover’ or arc to take place. The risk of flashover increases as the line voltage increases.

Managing the risks

Exclusion Zone Distances for Untrained Persons Without Consultation

Following guidance from the Tower Crane Code of Practice 2017, Falcon Cranes must ensure that workers, the tower crane and the load stay at least three metres away from overhead power lines, for voltages up to 132kV.

Greater distances apply for power lines with voltages above that. These distances apply to any part of the crane including the load it is lifting.

The chart to the right highlights the unsafe approach distances for Untrained Persons without consulation (e.g. without permits or Electrical Spotters).

To ensure that we maintain these safe distances, Falcon Cranes has introduced various safety controls to eliminate or reduce the risks of overhead power lines, following the Hierarchy of Controls. 

In the first instance we try to eliminate the risks altogether. This can be achieved by de-energising the electrical lines during work, isolating and earthing the lines, re-routing the electric lines away from the work area or replacing existing overhead electrical lines with underground cables. 

If elimination is not possible, we implement a combination of other safety controls to mitigate the risks as much as possible including physical barriers, exclusion zones, implementing electrical spotters, training staff members, implementing safety procedures & signage and more.

Zoning System

One of these safety controls is to limit movement of the crane by installing programmable zone limiting devices, which can physically prevent the crane from slewing into certain areas. 

Pictured below is an example of the control panel for a zoning system installed on our Potain MC85 Tower Crane at Upper Mount Gravatt for our client Opalyn.

It is imperative to note however that whilst these systems are very reliable, they should never be used as a primary means of risk mitigation, and should be used only as a back up / failsafe method. 

Zoning-System-Example

Unsafe Distances

The below chart was taken from the Electrical Safety Regulation 2013, it outlines the unsafe distances in mm. 

Unsafe Distances in mm from Electrical Safety Regulation 2013

Safety Observers

A safety observer is used to warn people and plant operators when they are likely to come closer within an unsafe distance of an electric line. 

As shown in the graphic below, a safety observer is required if the crane COULD enter any part of the power line exclusion zones. 

Crane of Load could enter exclusion zone

Zoning System Installation

Check out the drone footage below captured by Ryan Graham from Work Safety QLD of a Falcon Cranes project requiring a Zoning System Installation. 

You can view the original post written by Ryan Graham from Work Safety QLD posted on Falcon Cranes website here

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