Mitigation of hazards caused by process chemicals during shutdowns
The EU's Seveso II Directive requires that process plants manage the risks of major accidents associated with the process chemicals they handle. Safety management procedures should not only cover the normal operation period of the plant, but also special cases such as shutdown periods. Shutdowns need to be addressed as – in the vast majority of cases – hazardous process chemicals are still present at the installation in storage tanks, warehouses, silos and pipelines, even when the production process is not running.
The consequences of a chemical accident during such a shutdown may be severe as the number of persons working at the plant during that time is typically quite high – some Finnish companies report from 100 to 500 external maintenance workers at the plant during the busiest periods of a shutdown. The overall risk of a chemical accident during a shutdown might therefore be higher than expected at first glance.
Persons present at the plant during shutdowns might be affected by the process chemicals in various ways:
- Inhalation of the chemical (e.g. gases such as CO, H2S, SO2, and various fumes and vapours. Also lack of oxygen, i.e. typically an excess of N2 or CO2).
- Direct exposure through the skin (caused by splashes, contaminated surfaces, etc.)
- Physical effects (burns due to chemical fires or hot substances, frostbite due to cold substances, injuries caused by pressure waves (as a consequence of explosions, failing containment or opening (safety) valves), impact by fragments caused by explosions, etc.)
- Radiation (from unprotected sensors containing radioactive substances).
The aim of the Finnish SEISOKKI study aimed to investigate how six Finnish companies – all covered by the Seveso II Directive – deal with issues related to process chemicals during shutdowns of their installations.
The study revealed some shortcomings in the companies' risk management procedures in relation to process chemicals during shutdowns. The research team identified, for instance, the following possibilities for improvements:
- More time and resources need to be allocated for risk assessments prior to a major shutdown.
- The plant's EHS and rescue teams should take a bigger role in the planning process.
- By better scheduling of the maintenance work, bottlenecks in connection to the writing of work permits may be removed, thus allowing for a proper check of the safety of the workplace before maintenance work commences – much of the work need not to be started the first morning!
- A management procedure should be implemented to ensure that the operators (and indeed the foremen) are fully aware of how to make the plant – or a part of it – safe for maintenance work, and how to maintain this level of safety throughout the entire shutdown and start-up periods.
- The local fire brigade and the police should be informed about the shutdown and the risks in connection to this. The fire brigade and the police should have an external rescue plan in place also for this exceptional situation.
During the SEISOKKI project, several tools were developed to help Finnish companies mitigate chemical hazards during shutdowns at process plants. The tools are published in Finnish on this website, and include the following:
- A Guidebook describing the topic from various perspectives.
- An Auditing Method, by which various management issues related to chemical safety can be addressed by key persons at the plant.
- A Hazard Analysis Method, which is developed especially for the purpose of identifying hazards associated with process chemicals during shutdowns.
- A set of Safety Checklists for quick reference.
- A set of Work Permits.