PT Notes
Issues With Human Safeguards
PT Notes is a series of topical technical notes on process safety provided periodically by Primatech for your benefit. Please feel free to provide feedback.
A key focus in process safety studies, such as process hazard analysis (PHA) and bow tie analysis (BTA), is the identification of safeguards, also called barriers, that protect against hazard scenarios and hazardous events.
Barriers may be human or automated. Human barriers rely on people to perform actions, such as emergency response in the event of a hazardous material release. Even automated barriers rely on humans, e.g. for inspection, testing, and maintenance. Thus, barriers depend on how well humans perform tasks. Human barriers must provide a minimally acceptable standard of human performance and be robust against performance below that standard. There are various factors that can act to impair human performance and they must be properly managed. They include:
Systemic failures. Failure of a single organizational control often will degrade or defeat multiple different barriers. For example, if there are cutbacks in refresher training of personnel, barriers that depend on those personnel may be impaired. A systems view is needed to address underlying human and organizational factors that influence the reliability of human barriers.
Management decisions and actions. Management can create attitudes and incentives that undermine the performance of front-line personnel. For example, reward and incentive schemes may be implemented that focus on meeting production goals. In such cases, personnel may well perceive production to be more important than safety and incidents will eventually result.
Cross-checking. Cross-checking of human actions is used as a means of assuring work is carried out properly and human performance standards are met. However, its reliability is questionable. When someone knows their work will be checked, they may not be as concerned about accuracy and avoiding errors. Also, checkers may trust the person who did the work, believe their work is reliable, assume the work was done correctly, and not be as diligent in their checks. Thus, there is no real independence between those performing and those checking the work.
Reliance on mitigation safeguards. A scarcity of prevention safeguards allows hazard scenarios to occur and the avoidance of adverse consequences then depends on the correct functioning of mitigation safeguards. Situations where process safety depends mostly on human mitigation safeguards creates pressure on people to perform at a very high standard and in situations of both stress and time pressure. Furthermore, mitigation safeguards usually must operate quickly to be successful. Therefore, the people involved must act quickly. This situation decreases the reliability of human performance. A balance is needed between prevention and mitigation safeguards to manage this issue.
Views of human performance. Organizations frequently hold unrealistic expectations of how well people will perform tasks. Also, organizations often have an idealized, desk-based view of how tasks are performed (“work as imagined”) rather than an understanding of how tasks actually are performed under real-world constraints that require compromises and adaptation (“work as done”). Task analysis can be used to set appropriate expectations and establish approved ways of working.
Communication of expectations. Expectations for human performance as part of a barrier are rarely made explicit. Consequently, they are not communicated to those who need to implement, perform, support, or maintain barriers. People need to know the significance of their tasks, their assigned role, and the importance of reporting when they are unable to perform in the expected way or to the expected standard.
Competency. Personnel who are responsible for tasks required by human mitigation systems should be certified to meet a defined standard of competency through education, experience, practice, training and knowledge in specific technical areas.
Recertification. Most barriers are activated infrequently. Thus, the people responsible for human barriers may experience degradation of their competency over time as they are not called upon to perform their required tasks frequently. Consequently, periodic recertification of competency is important, including refresher training.
Many barriers in process safety depend on human performance. A number of factors may impair human performance. They must be managed and controlled if reliance is to be placed on human barriers.
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