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September 21, 2008

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Failure to isolate machine power supply costs two lives

Two men died inside an animal-feed mixer that started up unexpectedly because its power supply had not been properly isolated.

Hamilton Sheriff Court heard on 9 September that Peter Brown and Charles Hinshelwood had been cleaning the paddles of the mixer at the Stonehouse, Lanarkshire, factory of agricultural supplier Galloway and MacLeod on 26 November 2005.

The large bulk mixer contained two contra-rotating paddles, which were driven by an electric motor that could be controlled either manually or by computer. The machine started up unexpectedly, drawing the men between the rotating mixing paddles. “They suffered horrendous shearing injuries from which they died,” HSE principal specialist inspector John Madden, who investigated the incident, told SHP.

The court was told that the men had switched the machine off and pressed the emergency stop button before entering it. They had also removed a key switch from the control panel, and so believed that power to the machine had been isolated. “In fact, the key they removed controlled interlocking rather than isolation,” the inspector explained.

While the two men were inside the machine a plant operator started an animal-feed production run in a different area of the plant. By mistake, he directed the feed via his computer to the mixer in which the men were working. It was able to start up because of a wiring error inside the machine’s control system, which enabled the emergency stop and interlocking switch to be bypassed. The operator was not held to blame in any way for the incident.

“If the electrical power supply to the machine had been isolated, it would not have been possible for it to have started while the men were working inside it, even with the wiring error in the control system,” inspector Madden said.

Galloway and MacLeod was fined £18,750 after pleading guilty to breaching reg.16 of PUWER 1998 by not having an adequate emergency-stop system on the machine. No costs are awarded in Scotland.

Barr Electrical Contractors was fined £45,000 after pleading guilty to breaching s3(1) HSWA 1974 by failing to ensure the safety of those not in its employment, as it was responsible for the wiring error into the control panel that had existed for four years.

Galloway and MacLeod said in mitigation that it had believed that the procedures being adopted by the men meant the machine was isolated. It had been told by the machine-supplier that the procedure for isolating the machine was correct.

Barr Electrical said it took health and safety very seriously and had since improved its safety procedures. It said it had worked in cooperation with Promtek, the computer control-system supplier, who, it felt, ought to bear joint responsibility for the wiring error, but this was not accepted by the court.

Janet Cameron, area procurator fiscal for Lanarkshire, commented: “This tragic case has highlighted the critical importance of employers meticulously adhering to their legal requirements in terms of health and safety legislation. As prosecutors, we are absolutely committed to continuing to work closely with colleagues in the HSE to thoroughly investigate and prosecute these complex and often distressing cases, to ensure that a strong message is sent out to those companies who fail to comply with their legal duties.”

Concluded inspector Madden: “If anyone had tested the emergency stop on the plant the wiring error would have come to light, and the machine would not have been able to start, but it was never tested.”

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