Serious injury - hydraulic torque wrench

Mine type

All mine types

Incident

During assembly of a 55t excavator, a fitter was struck on the head by a hydraulic torque wrench (torque multiplier) whilst it was under pressure. Two fitters were applying the final torque to the lower track frame bolts when the impact socket dislodged from a bolt and the hydraulic torque wrench ricocheted and struck one of the fitters on the head. The hydraulic torque wrench weighs approximately 20kg.

Equipment

Hydraulic torque wrench—95mm socket, 38mm (1 ½") drive. Hydraulic pump @ 64.8MPa (9,400psi).

Hazard

Uncontrolled movement of hydraulic torque wrench.

Cause

The hydraulic torque wrench reaction arm did not have a secure footing (reaction point). It is also probable that the socket walked off the head of the bolt. A person was within striking distance of high energy powered tool.

Comments

The hydraulic torque wrench, operating at 64.8MPa, was not secured to prevent uncontrolled movement. The reaction arm did not have a secure footing (as at the corner of excavator body), and a packer was used between the side of the excavator (car) body and the reaction arm. On previous bolts, the reaction arm firmly abutted the underside of the excavator body.

The original equipment manufacturer excavator manual does not state how to tension the bolts at the corners of the excavator body, due to different torque wrenches and reaction arms available.

Manufacturer's safety instructions for the hydraulic torque wrench were not available to the fitters and the fitter had not received specific training in the use of the hydraulic torque multiplier, only buddy training.

The following hydraulic torque wrench manufacturer's safety recommendation were not followed:

• Stay clear during operation.
• Use an alternative means of securing the hydraulic torque wrench to the application if it must be held or steadied during operation.
• Single person operation (for both hydraulic torque wrench and hydraulic pump) to avoid premature operation of hydraulic torque wrench.

The fitter was holding on to the hydraulic torque wrench during operation.

The job safety analysis did not identify any hazards associated with tensioning these bolts. The workers informal risk assessment identified the hazard, however the controls were inappropriate and low in the hierarchy of controls.

A visual inspection indicated that both the bolt and the hydraulic torque wrench are in good condition. The wrench is undergoing further examination.

Recommendations

• A comprehensive job safety analysis must be completed prior to commencing assembly or disassembly of equipment, incorporating information from tool manufacturer's operating instructions and warnings. The JSA should include use of engineering controls:
  • To enable operator to be clear of hydraulic torque wrench during operation (e.g. an external means to secure the hydraulic torque wrench against a stationary object—electromagnetic support).
  • To prevent hydraulic torque wrench from coming into contact with operator (e.g. secure line attaching wrench to car body/track).
• Persons should be clear of unsecured equipment subject to high energy.
• The hydraulic torque wrench reaction arm should be appropriate for the task and have a secure footing (firmly abutted against a stationary object).
• Maintenance personnel should be fully trained in any equipment used.

Authorised by Gavin Taylor - Chief Inspector of Mines

Contact: minesafetyandhealth@dnrm.qld.gov.au

Issued by Queensland Department of Natural Resources and Mines