Risk Assessment techniques in the Process Industry

Risk Assessment is defined as the qualitative or quantitative determination of the degree of hazard (or threat) posed by a system, process, or any other entity. While risk assessment is a generic term which may apply to almost anything like the risk of an individual dying immediately after being insured to the probability of a car meeting with an accident while going on a highway, it means different things in the process industry. In the process industry, which can mean a wide variety of industrial sectors right from oil and gas, chemical processing to mining, risk assessment is the quantification or subjective assessment of the degree of hazards that could turn into accidents such as explosions, fire, leakages & spills and so on.
As you can imagine there are several different ways and methods of risk assessment in these industries and there are both quantitative as well as qualitative methods. Quantitative methods of risk assessments are known as QRA or Quantitative Risk Analysis. The subjective ways are many and they comprise of techniques such as HAZOP, HAZID, what if analysis and LOPA (which is also known as semi quantitative). Thus HAZOP is a kind of subjective risk assessment technique used mainly in the process industry (although reportedly some variants are also used in the software and allied sectors).
Among all these techniques, the most popular one today is HAZOP.

For example, consider the gas storage tanks (spheres) above. There is obviously a risk associated with this storage which is the risk of explosion and or fire or gas leak. Now to assess this risk we can use a variety of risk assessment techniques, the main one being HAZOP. We will break down the unit into logical nodes and each node will then be analyzed using the HAZOP technique to provide an estimate of the risk associated with the storage.

PHA-Process Hazard Analysis

Today, we will examine in brief what is referred to in industry parlance as PHA or Process Hazard Analysis. PHA refers to any technique that is used to identify hazards that may exist in any industrial, manufacturing or any such similar activity. More specifically it refers to the hazards that are to be identified in the process industry. As you know the "process industry" is a generic term that covers a wide range of industries such as chemicals, oil and gas, power generation, mining and the like. These industries have several hazards present due to the nature of their operations and they need to be identified, reduced to a safe enough level to minimize the risk of accidents and thus mitigate them. PHA thus refers to any technique that can reliably do so. There are several PHA techniques that are used in the process industry and they are HAZOP (Hazard and Operability Study), What-if analysis, HAZID, LOPA (Layer of Protection analysis) to name a few. Out of these HAZOP and LOPA are growing in popularity worldwide.LOPA as a PHA technique is also used as a SIL determination technique. SIL is an acronym for Safety Integrity Level and we will cover that in a separate post.

HAZOP-Hazard and Operability Study

Sep 19, 2013- HAZOP is an acronym for the popular Hazard and Operability Study. However the focus of most HAZOP studies seems to be more on the "Hazard" part rather than the "Operability" part. Did you notice it? The operability refers to how easy or how difficult would it be to operate the plant in its current form. For example, it is easy to say (and record) that in case of an upset the plant operator will close the Hand Valve HV101. However where is it located? Is it easy to close it? Is it accessible? What if it requires an effort just to reach it? Would the handle get jammed? These operability questions are very relevant in HAZOP studies and must be addressed. In recent years, almost nothing is discussed in HAZOP studies about the plant's operability. On hopes that in the coming years the operability factors will also play an important role. After all, a plant that is easy to operate and run should cause less stress amongst operating staff and thereby cause lesser dangerous incidents or accidents, is it not? One good move in recent years has been though that "human factors" are seen to be as important as the plant design factors and these would be given weightage in the new HAZOP studies. For an in-depth course on the Hazard and Operability technique, you can refer to the Abhisam training course on HAZOP.