A LOCAL man was tragically killed because a hydrogen gas build-up under the roof became "like a bomb," and a spark from an angle grinder he was using acted as the detonator, an inquest heard this week.
William Andrew (Drew) Stevenson, 51, from Main Street in Killen, was killed instantly from the injuries he sustained in the explosion at Carmoney Waterworks at Eglington on June 2, 2005, the coroner's court sitting in Derry on Monday was told.
A series of witnesses was called in the case, including co-workers of Mr Stevenson, representatives from the Water Service, Health and Safety Executive, and a forensic expert who examined the scene. Mr Stevenson's widow Jean, his brother and his six children were present in court throughout the proceedings.
The jury heard that Mr Stevenson and a colleague, Peter Thompson, went to the water treatment works to carry out the task of installing new vents on the roof of a building which housed two tanks used in the production of hydrogen chloride.
Hydrogen gas is a by-product of the process, and it was found that, because the production plant had not been shut down, the gas had accumulated under the roof. When Mr Stevenson used an angle grinder to cut a hole in the roof, a spark from the tool ignited the gas, causing an explosion which propelled one of the cylinders up through the roof and it was found some 60 metres away.
Mr Stevenson was killed instantly; his body was found around 40 metres from the site of the blast. His colleague Mr Thompson fell through the hole left by the cylinder and miraculously suffered only a broken leg.
Mr Thompson explained that the pair had gone to Carmoney from another job, and that they expected to be there for no more than an hour.
He also said in his evidence that he was unaware of the existence of hydrogen gas or the hazards involved, and said that he could not recall seeing any health and safety or danger signs on the building.
The plant operator at Carmoney, in his evidence, explained that if any work was scheduled to take place in the vicinity of any of the machinery or processing equipment, then he would be directed to shut it down in advance and not to turn it back on until work was completed.
He said that this was the common practice at the plant. He also said that it would have been up to whoever was on duty at the plant to sign the workers in, and inform the manager of what was to take place.
When asked by the coroner, Mr Leckey, whether the sight of someone carrying an angle-grinder would have set alarm bells ringing with him, he replied, "Yes, definitely." He also said that a week prior to the accident, he had informed workers of the risks of operating in the area and the need to isolate it.
The original installers of the plant system explained that they had installed an open-air facility, which was self-venting. However, due to exposure to the elements, the Water Service had decided to create a building around it, and that once it was roofed it created a danger.
He said, "We would never have installed that type of system underneath a roof."
Dennis McCauley, a forensic scientist who examined the scene, said in his report that the explosion occurred because of a build-up of hydrogen in the ducting beneath the roof, and that it was likely that a spark from the angle grinder caused the explosion. He said in court that Mr Stevenson "was working on top of an explosive atmosphere".
The jury found that a spark from the angle-grinder caused the explosion which led to Mr Stevenson's death as it ignited the hydrogen gas trapped below the roof.
When asked if there were any reasonable precautions whereby the accident could have been avoided, they concluded that the plant should have been shut down, that no permit had been given for the work being carried out, a proper risk assessment should have been carried out, and that the area should have been verified safe, for example through the use of Gas Metering equipment. They also said there could have been better safety and hazard warning signs, as none were present on the actual roof of the building, and that there were very poor communication channels.
When asked to identify the defects in the system of working which contributed to the accident resulting in the death, the jury concluded that the type of tanks involved should not have been enclosed, gas detectors should have been provided, and that the workers should have been supervised by the plant operator. They also concluded overall that Health and Safety regulations should have been a priority.
Mr Stevenson's widow, Jean, is taking civil proceedings against both the Department of Regional Development and Lowry Brothers Ltd under the Fatal Accidents (NI) Order 1977 and the Law Reform (Misc Provisions) Act NI 1937.
