Throughout the years, a number of process safety incidents have involved simultaneous operations, or SIMOPs for short.
When two or more operations are undertaken in the same vicinity at the same time, there is a risk that they may interfere with one another, either introducing new risks or exacerbating existing ones. Unfortunately as with many such issues it takes a major incident to highlight the need for action to be taken.
In 2022 one fatality and three serious injuries resulted from a hydrogen chloride discharge at Wacker Polysilicon facility in Charleston, Tennessee.
A heat exchanger outlet pipe containing hydrogen chloride was accidentally cracked due to over tightening of fasteners, resulting in an uncontrolled release which impacted workers engaged in another task nearby – no coordination had taken place between the two tasks and therefore no controls had been put in place to mitigate potential issues. While the workers involved in the fastener tightening wore full protective suits the workers on the other task wore only flame retardant suits which did not protect them from the release.
Recommendations made after the incident by the U.S Chemical Safety and Hazard Investigation Board ( CSB) included measures to identify SIMOPS , spot potentially dangerous interactions and to coordinate activities to mitigate risks.
Permit to work has a big part to play in the early management of SIMOPS. When a permit is being issued the PTW system should identify other nearby tasks so that a decision can be made on whether to progress. Integration of a robust risk assessment process should also ensure that all the data required for decision making is immediately available.