Crane Accident – Contact with 11KV power line

Introduction

The crane contractor was requested to come to the construction site to dismantle and transport  their 4600 and 4100 Manitowoc cranes offsite.

  • Three personnel came to site – A leading hand, crane driver and fitter.
  • The fitter and leading hand had received a full Construction Orientation together with contractor site specific inductions.
  • The crane driver was new to site and received a short-term induction conducted by the security personnel at the security gatehouse. This type of induction only allows the person to work under direct supervision until the next available site induction.

Precursors to the Incident

  • The 4100 Manitowoc Crane was travelled by the crane driver via a back road to the old lay down area just inside the security gate.
  • The crane was required was to load broken down boom sections of the 4600 Manitowoc crane onto a semi trailer for transport off site.
  • The lay-down area had been in use for over twelve months as a construction lay down area by another contractor. During this period, an 11 KV power line was erected on the main road access (eastern) side of the lay down area.
  • On the morning of the incident; the crane was used to load two boom sections onto a semi trailer.
  • There was no crane contractor site specific induction or pre-start meeting conducted on the day of the incident.
  • A Job Safety Analysis was not conducted by crane contractor.
  • The crane contractor had standard operating procedures for dismantling the 4100 Manitowoc crane.
  • After the boom sections were loaded, the crane driver decided to locate the crane in a position ready for dismantling.
  • There had been no discussion with the Crane Contractor Leading Hand on the setup area for the crane dismantling.
  • The crane driver travelled the crane in an east north-easterly direction towards the main access road.
  • Rigging slung off the main hook consisted of an 8 tonne synthetic sling, two lifting chains and another 8 tonne synthetic sling – in that order.

The Incident

  • As the 4100 Manitowoc crane was travelled forward, the lifting chains contacted the two closest power lines creating an electrical fault which tripped the 11KV circuit breaker.
  • At the time of the incident the sun was in the north easterly aspect and interfered with the driver’s vision when looking upwards out of the cabin in the direction of the power lines.
  • The crane operators cabin front window was in a clean condition.
  • The power lines are small objects to view and there were no power poles or other indicators to assist the driver in locating them.
  • A rigger was not in attendance at the time.

Damage and Injuries

  • The crane driver did not suffer any injuries and the 4100 crane was not damaged.
  • The 4100 Manitowoc crane rigging suffered damage with the lifting chains being welded together and the lower synthetic sling suffering some heat damage due to the contact with the heated lifting chains.
  • The synthetic sling attached to the main hook did not suffer any heat damage and acted as an electrical insulator, preventing current passing through the crane to earth.

Facts and Discussion

The crane driver has a valid NSW crane license.

  • One of his primary responsibilities is to be familiar with his work area including the location of obstacles such as over head power lines.
  • A prior inspection of the area was not done by the crane driver.
  • The crane driver moved the crane without consulting with his supervisor regarding the most appropriate location for dismantling the 4100 crane

The area where the incident occurred was the original site lay down area for a major contractor.

  • The power line was erected on the eastern boundary of this area when there was active use of the area with offloading and loading of materials using cranes.
  • To encourage construction personnel to use the access correct roads, temporary barricading was erected along the power line corridor to prevent traffic cutting into the lay down area at any convenient spot along the eastern boundary. The barricading was removed during final road works.
  • Safe use of this lay-down area next to a power line relied on people remembering that the power line was adjacent, especially regarding crane operations and was subject to human error as the power line is difficult to see from an operating crane cabin.

Project orientation sessions, site specific inductions and prestart talks were a project requirement for all contractors.

  • Two of the crane contractor employees had a project orientation and site specific inductions They had not been on the site for several months prior to the incident and had forgotten site safety system requirements
  • The other contractor (crane driver) had a short-term induction which enabled him to work under direct supervision of an inducted person