Prosecution Details

Being an employer, failed, so far as practicable, to provide and maintain a working environment in which employees of the employer were not exposed to hazards, and by that failure caused the death of an employee; contrary to sections 19(1) and 19A(2) of the Occupational Safety and Health Act 1984.

Summary of the Incident

On 9 May 2019, an employee of the Offender (Victim), was operating a column and boom welding manipulator (Welding Manipulator). The boom of the Welding Manipulator fell suddenly, crushing the Victim who was working underneath the boom. The Victim died as a result of the crush injuries.

The Incident occurred at the Offender’s main workshop in Bassendean (Workplace) where the Offender designs, manufactures and repairs equipment for a variety of industries, such as mining, oil and gas, food, car, aerospace and defence.

The cause of the sudden fall of the boom was the failure of the top and bottom acme nuts on the screw drive mechanism of the Welding Manipulator. The threads on the nuts were worn to such an extent that they were unable to maintain the load placed on them.

Workplace and Employment

The Offender is an engineering firm with approximately 600 employees worldwide.

In May 2019, the Offender was in operation at the workplace and had various types of manufacturing equipment in use, such as welders, welding manipulators, CNC milling machines, gear cutting machines, vertical borers, and a 5000 tonne press.

The Offender manufactures a variety of items at the workplace in the “fabrication workshop” (Fabrication Workshop). One of the tasks carried out by employees working in the Fabrication Workshop includes the manufacture of girth gears. Welding manipulators are used in some of the welding processes.

A welding manipulator allows for the welding head to be positioned adjacent to the work piece to weld. When welding, the operator stands on a platform positioned under the welding manipulator boom and adjacent to the work piece.

The Welding Manipulator Involved in the Incident

The offender had 5 different welding manipulators in use at the Workplace. One type is a “column and boom welding manipulator”, where the boom is raised and lowered using an electric motor.

The Welding Manipulator involved in the incident was approximately 40 years old and was the only “screw drive” welding manipulator at the Workplace. The “screw drive” mechanism is a threaded rod, which rotates on two stationary bronze acme nuts (acme nuts).

Several years before the incident, the Offender had added a platform and railing onto the boom of the Welding Manipulator for ease of access to the boom. The addition of the weight of this platform added further load to the boom.

There was no manufacturers operation manual, or maintenance logbook kept for the welding manipulator. It was unclear whether it had been fixed, parts had been replaced, or grease had been added to the screw, other than through word of mouth between operators.

Leading up to the Incident

The Welding Manipulator had been unused for several years and kept in a storage in the “High Bay” at the Workplace until February 2019 when it was put back into service. While in storage it had not been fully covered, and some parts of the Welding Manipulator had been exposed to foreign material. 

On being put back into service, it was subject to a general “clean down”. This involved a wipe down of the machine, and a visual inspection to check it was operating correctly. No full internal and external service or mechanical inspection of critical parts was conducted. No preventative maintenance was undertaken.

The only checks that were done on the Welding Manipulator were visual pre-operation checks conducted by operators. This was limited to checking items such as operating buttons, making sure the machine went “up and down”, and that there weren’t any unusual noises.

If an operator noticed the machine needed grease, the operator would ask maintenance for grease to add to the screw.

Apart from the visual checks conducted by operators as part of their pre-start set up, there was no other scheduled maintenance or inspection carried out, or recorded, by a suitably qualified fitter.

Other machines at the Workplace which had a similar screw drive mechanism were on a routine maintenance schedule which included a check from a qualified fitter every year of wear components of the machine. They also had safety nuts, or wear indicators installed, that indicate when wear in a nut is beyond a safe point and the nut needs replacing.

In the weeks leading up to the Incident, the Welding Manipulator had been used by other employees to weld segment gears. 

Incident on 9 May 2019

On 9 May 2019, the Victim was tasked with welding the clamp plate on the end of a girth segment using the Welding Manipulator. The Victim was the only person using the Welding Manipulator at the time of the Incident.

The Victim was underneath the Welding Manipulator boom on a work platform to access and operate the control of the Welding Manipulator and welding head.

The Welding Manipulator was in operation as the welding head moved across the weld, when the boom dropped suddenly onto the Victim crushing him between the boom and the work platform.

Immediately after the Incident, the Offender’s employees used a crane to lift the boom up. The Victim was then moved from the work area and administered first aid until an ambulance arrived. The Victim died as a result of the crush injuries.

The hazard and contravention

The sudden fall of the boom was caused by a failure of the top and bottom acme nuts on the screw drive mechanism of the Welding Manipulator.

Independent experts confirmed the threads on the bronze acme nuts were worn to such an extent that they were unable to maintain the load placed on them. The grease on the screw was grossly contaminated with foreign fine solid material, such as flux, to a point where it was having a negative effect on the screw (abrasive rather than lubricating).

The Offender did not keep a maintenance log book for the Welding Manipulator, or require a qualified fitter to check the wear on the components unlike other items with the screw drive mechanism.

The Welding Manipulator was not subject to a full internal and external service or mechanical inspection of critical parts before it was put back into service after being unused for several years.

Offender’s actions following the Incident

Following the incident, the Offender:

• developed a written guide of how to visually inspect the lead screw on the screw drive mechanism for damage and inspecting safety nuts (wear indicators), and developed and trained operators in a new Safe Operating Procedure – Use and Inspection of Column and Boom Type Welding Manipulators;
• designed and installed an “acrow prop” or emergency fall break support system on its welding manipulators, to prevent the boom falling past a safe point;
• uploads and tracks the servicing and maintenance history of the eight machines at the Workplace that have screw drive mechanisms, on its online asset register.

A weekly audit is now be conducted of the pre-starts and maintenance logs to ensure they are being filled out correctly.

Hofmann Engineering Pty Ltd was sentenced in the Perth Magistrates Court on 25 November 2024 following a guilty plea entered to a charge for a breach of s. 19A(2) of the Occupational Health and Safety Act 1984 (WA) entered on 9 October 2024. The Magistrate issued a fine of $567,000 and ordered costs of $28,695.21.