Dangerous and exposed machinery

With the safety of its employees of paramount importance, Queensland manufacturer Neumann Steel has installed Telemecanique Preventa safety equipment from Schneider Electric to ensure any potential risk of hazards is further reduced by the use of Category 4 safety switches.

The Preventa magnetically coded read switches and Secu-twin safety circuits have been installed to monitor the gates that guard the wire-cutting machines. These powerful machines turn massive coils of steel wire into individual reinforcing wire lengths for steel mesh. The task of the Telemecanique Preventa equipment is to ensure the machines can only operate when the gates are securely closed.

Neumann Steel manufactures concrete reinforcing products, annealed wire and HDLC manufacturers' wire. Its products are widely used in buildings such as the Gold Coast's famous 80 storey Q1 building, which on completion will be the tallest self-supporting structure in Australia.

Peter Whelan, Neumann Steel's Safety Officer, said the company regularly carried out risk assessments to eliminate as completely as possible any risk of injury.

"However, we felt more was needed, and with such safeguarding now available in the marketplace, this gave us the impetus to even further increase our efforts to make our workplace as safe as possible," he said. "Although it was not compulsory, we chose to upgrade our plant to the highest level - Category 4 - which provides the monitors and checks to ensure a fail-safe system."

The three wire drawing machines in the bar shop area were of particular safety concern because of their moving and rotating parts. The steel wire is brought into the plant in huge coils, two tonnes in weight. In a continuous operation, these machines draw the steel wire off the coils and bend it into the required shape to produce concrete reinforcing bar.

To minimise potential danger the machines are fully fenced. However, it was vital to monitor the entry point to eliminate any risk that someone could make physical contact with the machines while they were in operation.

At the request of management, the plant's electrical contractor Mick Baker contacted several suppliers to find out what equipment was available to do the job.

"We decided on the Telemecanique Preventa safety equipment because it was robust enough for our heavy industrial application, it was cost-competitive and because our wholesaler always has spare switches and parts in stock, so we will have no service problems," he said.

Neumann Steel installed Preventa XCS-DM coded magnetic safety switches with XPS-MP Secu-twin safety modules, which guarantee machine operator protection in applications up to Category 4.

The Preventa XCS-DM coded magnetic safety switches are specifically designed to prevent access to danger zones in severe environments while the Preventa XPS-MP modules are microprocessor-controlled, have two independent safety outputs and can be configured to monitor a range of devices, so there is no need for a dedicated relay.

"The Preventa switches read whether the guard is open or closed and send signals back to a PLC which controls all motors," said Mr Baker. "Each machine guard has special latches with dedicated keys. To gain access to the machine, the operator has to insert the key into the outside control circuit, turn off the power, take the key out, and unlock the gate. If by any chance the gate is opened when the machine is not turned off, the Preventa module ensures the machine is automatically shut down to eliminate any danger. This meets the requirements of Category 4 and ensures our operators' safety."

Mr Whelan said the Preventa magnetic read switches are working perfectly.

"Being situated so close to the machines means they are constantly covered in metal dust but they just keep functioning. We're very pleased with them," he said.

As part of its ongoing safety program, Neumann Steel is investigating the possibility of installing further Telemecanique Preventa equipment, including light curtains.