Is it assumed by default that there are no safety measures in the preliminary HAZOP for chemical process design?

HAZOP (Hazard and Operability Study) analysis is a risk management tool commonly used in the engineering design process to identify potential hazards and operational issues within a process system, and to recommend appropriate improvements to reduce those risks. HAZOP is typically applied at various stages of chemical engineering design, including the conceptual design, preliminary design, and detailed design phases. When conducting a HAZOP analysis in the early stages of chemical engineering design, two aspects are generally taken into consideration: 1. Safety measures already considered in the design: During the preliminary design phase, the design team may have proposed certain safety measures, based on previous experience, standards, and regulations, to ensure the safety of the processes. These preliminary safety measures are the design team’s predictions and preventive actions against potential problems; they typically include things such as safety valves, rupture disks, and emergency shutdown systems. 2. “Recommended actions” in HAZOP analysis: HAZOP analysis may identify additional potential risks that were not detected or were underestimated during the initial design phase. At this point, the HAZOP team will propose new or additional measures to further enhance the safety of the system; these suggestions include improving the design, adding control systems or safety devices, etc. In other words, the correct approach to conducting a HAZOP analysis should be: – To acknowledge and document the safety measures that have already been incorporated during the design phase. These are the preventive measures taken by designers based on current best practices and safety standards. - On this basis, a systematic risk analysis is conducted to identify any factors that might be overlooked and lead to accidents, or safety measures that could fail under specific circumstances. - For the additional risks identified through HAZOP analysis, new “recommended measures” are proposed, and these risks are rated based on severity and likelihood. The design team needs to clearly list these “existing safety measures” and “recommended measures” in the HAZOP report, so that they can be taken into consideration and integrated in subsequent design stages. In short, during the design phase, HAZOP should not assume that there are no safety measures shown on the process flow diagram. Instead, all safety measures that have already been incorporated into the design should be identified and documented, and on this basis, a risk assessment should be conducted along with recommendations for additional improvement measures. This approach ensures that the design ultimately meets the established safety standards, and enables effective management and reduction of potential risks. .

By default, it’s not included, I’ve dealt with cases like this before

The question raised by the original poster concerns HAZOP during the design phase; its purpose is to identify and assess risks that could potentially cause harm to people or property losses, not to satisfy certain opinions! A paper published in the Chinese Journal of Safety Science suggests that excessive reliance on management experience and repeated analysis processes objectively lead to a decline in the marginal effectiveness of the (HAZOP) tool itself. The correct approach is to restore HAZOP to its role as a tool, and to use HAZOP as a systematic and structured hazard identification method for dynamically identifying risks. Once it becomes procedural, it’s not far from becoming institutionalized. (This document link)

There’s no construction going on at all; there’s nothing here, so where could any risks come from? During a HAZOP analysis, it is possible to examine the risks associated with construction as well, but the HAZOP analyst leading the analysis usually lacks construction experience and may not be able to identify many risks. HAZOP analysis is conducted to identify problems in existing process flows, and the recommended measures focus only on additional safety measures that are needed.

For a new project, the general consensus regarding HAZOP analysis during the design phase is as follows: 1. Conduct a HAZOP analysis during the basic design stage; 2. The measures already indicated on the PID diagram are considered “existing measures,” while the “suggested measures” discussed in meetings are added to the PID diagram after its “HAZOP Review version” is created. Additionally: The hazard analysis during the construction phase can employ the JHA analysis method, while the HAZOP method is less suitable.