The mine operator was concerned about the reliability of the safety systems at their coal mine, which was operating in care and maintenance mode. Their key concern was the risk of gas explosion and the threat posed to a crew that would enter the mine after periods of inactivity.
Rather than relying on various opinions about a target Safety Integrity Level, Advitech combined actual fatality data published by the Resources Regulator with the professional judgement of the mine operator, to estimate just how likely such a serious event would be at their site.
Advitech’s TÜV accredited Functional Safety Engineer helped the mine operator determine the extent of risk reduction necessary to bring the frequency of serious undesired events to tolerable levels. This is the first step in specifying a SIL for any proposed safety system.
This still left the question of “What is tolerable?” Advitech used published guidelines from the NSW Department of Planning and the UK Health and Safety Executive to help the mine operator establish a benchmark. In this way, the required amount of risk reduction was estimated, thus providing a rational basis for a SIL specification.
As it happened, this turned out to be a lower amount of risk reduction than first thought, and thus avoided unecessary expense. Of course, the mine operator still has a general obligation under WHS regulations to reduce risks “so far as is reasonably practicable”.