Seals must be designed to withstand overpressure of 345 kilopascals under existing regulations.
“As it is impossible to test these seals in place, their reliability is being determined by checking the properties of the construction materials and by digital modelling through 3D stress analysis,” the state’s Mines Inspectorate said in a safety bulletin.
Measures taken, such as the installations of pipes, tubes and doors, had increased the complexity of seal design.
“For example, a recently used seal included three hatches to control the flow of goaf gases into the return as part of the inertisation process,” the inspectorate said.
“While the seal structure and the hatches were separately rated at 345 kilopascals, there were concerns that the overall construction did not achieve that rating.”
Chief inspector of coal mines Gavin Taylor consequently authorised an independent engineering study of the seal arrangement in this case.
“This study showed that, while the seal arrangement was capable of withstanding the 345 kilopascal overpressure, it could sustain damage that would render it unfit for further use as a seal,” the inspectorate said.
As contractors typically construct seals, the inspectorate recommended that underground mine managers and ventilation officers undertake a quality control review of installed seals.
The integrity of the seal should be validated by an engineering review and minesites should also review relevant safety documentation.
