Process safety is an integral part of the overall safety management of chemical plants. It draws on both engineering and leadership competence and focuses, in particular, on preventing chemical spills and minimising their consequences. 
Weaknesses in process safety can at their worst lead to serious personal injury or substantial environmental or property damage. There are various ways to improve safety, including technological solutions, the correct
positioning of machinery, effective change management as well as procedural development and staff training.

The definition of process safety is not clear-cut, but in this article the concept is understood to mean the management of risks relating to the handling and storing of chemicals in industrial contexts. 
Process safety can be improved by investing in the entire plant, individual processes and people. The way in which buildings and stores are located on the property, how machinery is positioned inside the buildings, what chemical spill containment systems are in place and what fire-fighting equipment is available, all affect the level of process safety. Critical elements within the production process itself include hazardous chemicals and the way they can react with each other, various process parameters (such as pressure, temperature, pH and flow rate) and the degree of process automation. 

These systems are designed and operated by people, which is why people also play a key role in determining the level of process safety. The organisation running the plant and its decision-making and executive bodies are also made up of people. All of the aforementioned components of process safety are in a constant state of flux while the plant is in operation, and the risks presented by changing circumstances need to be carefully managed.
All efforts to improve process safety should start with risk assessment. The consequences of process failures (explosions, large fires, clouds of toxic gases) can be too catastrophic to contain afterwards. This is why the focus must be on prevention, and accidents can only be prevented if the risks are known.

Risk assessment in a fundamental role

A systematic approach is crucial in the assessment of process safety risks. It is essential that the chosen method is comprehensive enough to factor in the root causes of human error as well as not just the risks that are inherent in the process but also those related to storage (including loading and unloading) and other handling. If the information provided by one method is not enough for a comprehensive assessment, a second method can be pursued to complement the data. While it is essential that the person performing the risk assessment has experience of the chosen method or methods,
it is the operator (workers) who ultimately provide the data about the process itself.

Process safety can be improved by investing in the entire plant, individual processes and people.

The objective of risk assessment is to identify risks – such as spills, unwanted chemical reactions and events such as overheating – and the specific root causes of the risks (e.g. in the case of pipe failure, the reasons for the failure) as well as the consequences of the risks materialising (such as the damage caused by a fire resulting from a gas leak). The probability of the event is then determined taking into account all the known mechanisms of exposure to the identified risks (e.g. a gas leak can be attributable to pipe failure resulting from corrosion, clamp failure or physical impact, or to valve failure resulting from worn or cracked seals). 

The final step is to assess the severity of the event by factoring in all the known consequences of the event. A gas leak, for example, can lead to death by asphyxiation or a devastating fire.

The results of the risk assessment give the operator information based on which they can evaluate the adequacy of the precautions they have in place. This includes both safeguards designed to prevent accidents and measures that will help to limit the consequences if an accident does happen.

In the context of process safety, it is important that the risk assessment covers the entire plant, including outdoor areas and any separate buildings or spaces in which chemicals or explosives are stored, handled or used. This promotes the principles of continuous improvement by allowing the operator to establish the baseline for process safety at the plant, set targets and monitor progress against relevant indicators.

Human factors

Many accidents are either directly or indirectly attributable to human factors. People design and build the plants and processes, carry out risk assessments, choose the techniques and procedures to be applied, operate the processes, and service and maintain the equipment. 

The actions of people therefore influence many safety-critical aspects of the operation at several different stages of a plant’s life. Human factors can be examined in various contexts, such as the operating environment and the organisation, relationships with other people, the choice of tools and equipment, and the competence required for the work. 
While the focus is usually on the risk of human error, human factors can also have a positive impact through, for example, the ability to deal with unexpected situations more flexibly than an automated system. There are two types of human failure: errors and violations. 

A human error is an action that later turns out to be a mistake. Some errors are slips or lapses, and others are errors of judgement or decision-making. Violations, on the other hand, are intentional deviations from the rules or agreed procedures.

Continuous servicing and process maintenance are essential for ensuring the safe operation of any plant.

Regular maintenance

Continuous servicing and process maintenance are essential for ensuring the safe operation of any plant. This is why all chemical plants need a maintenance system that sets out both preventive and corrective procedures. In most cases the system is computerised and consists of a preventive maintenance plan and lists of pending and completed actions.

Safety-critical equipment includes all those components that can, if they malfunction, cause a dangerous situation or that the plant relies on to prevent accidents – alarms, for example. Safety-critical components must be identified and incorporated into the preventive maintenance plan. What this means in practice is servicing, testing and replacing safety-critical components often enough to stop them from ever failing. 

The data held in the maintenance system can be used, for example, to check whether scheduled servicing or repairs have been carried out, to provide feedback to workers who report issues, to monitor the relationship between preventive and corrective actions, and to measure process safety. Indicators of process safety include, among others, the timeliness of scheduled servicing and repairs as well as fault statistics.

With so much emphasis put on occupational safety, process safety can end up being seen as a secondary priority. Understanding of the importance of process safety is nevertheless growing all the time, and the Finnish Safety and Chemicals Agency is working hard to give it enough attention in its enforcement and communications policy. Despite the several interfaces where process safety and occupational safety overlap, the two are not the same. Process safety deserves – and needs – its own spotlight.

Sanna Pietikäinen, Senior Officer, Process Safety,
Finnish Safety and Chemicals Agency