The Process Safety Information (PSI) element within PSM has three different categories that include: Information pertaining to the hazards of the highly hazardous chemicals, Information pertaining to technology, and Information pertaining to the equipment in the process. PSI, in this person’s opinion next to employee participation, is the most important element in process safety management, and in many cases has the most gaps in compliance and understanding.
It is important to understand the three distinct process safety information requirements. To help understand these categories better, it is best to think of the steps that are typically taken in the development of a new or a major process revision. Every new process design starts with some very simple basic concepts to achieve a specific objective. The first item that is normally considered in the design, no matter what the process, is what chemical or material will be involved. Even a simple process, such as a closed loop refrigeration system, will use some type of chemical (refrigerant). The decision on which chemical is to be used, will inevitably include a discussion of chemical hazards including toxicity and flammability. The next important category in PSI is the “information pertaining to the technology of the process”. One item in this category is a simple process or block flow diagram or a heat and material balance. The process flow diagram and heat and material balance is used to determine “how much” chemical(s) will be needed or intended to be onsite at any point in time. For the most part, these are the first two parts of process safety information except for one, the “Safe Upper and Lower Limits of the process and the consequence of deviation from those limits” (pressures, temperatures, flows, and compositions). It is important to understand that the safe limits required here have nothing to do with equipment limitations, and everything to do with process knowledge and limitations period. If we stop with just these two elements of PSI alone, we have enough critical information to communicate to stake holders and perhaps the public, and gain buy-in prior to going forward with more detailed design. Conducting detailed design is a very costly process and making sure all stakeholders are on-board is important. The block flow diagram, toxicity information, the safe limits, and the consequence of deviation from the safe limits is simple information that is used by engineers to communicate or explain a new process or process improvement from a very high level.
Very little cost is involved in developing these two categories of process safety information, but more often than not, “go or no go” decisions are made based on this information alone. On the other hand, failure to address these first two elements completely will inevitably lead to much higher design costs and process safety events and incidents. If the proposed process design is a “go”, then the detail design (technology of the equipment) should be based on the first two elements of process safety information. For example, knowing the maximum intended chemical inventory helps the design engineer to size the equipment, and knowing the safe upper and lower limits of pressure, temperature, and composition will help with design of equipment, controls, relief systems, ventilation, and the rest of the technology including the materials of construction. Notice, you do not want to design “process to the equipment”, rather you want to design the equipment to address process requirements. In summary, we need to not only have the Process Safety Information on the equipment as listed in 1910.119(d)(3), but also the design intent information included in (d)(1) and (d)(2). Without all these elements of PSI, your Process Hazard Analysis (PHA), will miss a number of potential hazards. Remember, trash in trash out. Bad or missing PSI WILL result in missed potential or real hazards, and eventually lead to process safety events.