Badly fitted disc blamed for leak

Press, 18 June 1986, Page 9

Badly fitted disc blamed for leak

PA New Plymouth A D.S.I.R. report released yesterday blames a badly fitted safety disc for a chemical leak at the plant of Ivon WatkinsDow, Ltd in New Plymouth in April. The report by two Wellington scientists, Dr Donald Smith and Dr Ross Nicol, expressed concern about a five-minute delay in working the drenching deluge system designed to contain leaking vapour in the plant.

The scientists said a cloud of vapour was carried from the trichlorophenol plant, part of the 2,4,5-T manufacturing process, and a small quantity of highly toxic dioxin escaped. dis' ''oti id ale

The . sc ruptured along its side when a reactor making sodium trichlorophenate was working under normal pressure.

The disc had been installed a month earlier and incorrectly given an extra gasket and placed 3.6 mm off-centre, the report said. At a press conference yesterday the I.W.D. manufacturing manager, Mr David Hedge, said the fitter might have tried to duplicate a previously used style of disc, which

had two gaskets. The second gasket allowed no tolerance for the off-centre placement, he said. The report said about 1415 kg of material was released from the reactor, including between 70mg and 735 mg of dioxin. Mr Hedge said this was consistent with I.W.D.’s estimate of 150 mg of dioxin released. No traces of escaped dioxin were found in or around the plant. The report found that a significant amount of released material was not contained in the building housing the reactor. Some material containing dioxin. was carried from the plant as a finely divided mist. More than half the material was probably

vented in the first five minutes before the deluge was turned on, the report said.

Mr Hedge said all equipment in the plant was ignition or explosion proof. Standard safety procedures were activated.

When the disc ruptured four men on duty tried three times to enter the building and vent the reactor. They were driven back by the odour and poor visibility.

After five minutes the plant supervisor was telephoned and he ordered the use of the deluge system, which automatically summoned the New Plymouth fire brigade. The report has ordered seven steps by I.W.D. before the trichlorophenol plant can restart.