Hazard Identification techniques

These typically include:
HAZOP (probably the best and most detailed)
Preliminary Hazards Analysis (widely used)
Failure Modes Effects and Criticality Analysis or FMECA (specific for equipment such as fired heaters etc.)
What if? (not so common as it depends upon the correct questions being asked).
Hazard Indices (Dows Index, Mond Index etc.) - (used mainly by Insurance companies)
Hazard Studies (a powerful technique, invented by ICI that addresses hazard issues right from inception to commissioning and stabilisation phase of a project).
Others

Discussion is on PHA and HAZOP.

 

Preliminary Hazard Analysis

This examines a facility from the point of view of identifying areas, processes, locations and chemicals which pose a hazard potential. It is carried out as a first activity as it affects the balance work of a hazard study. Techniques used for hazard identification during a Preliminary Hazard Analysis include ranking through screening consequence analysis programmes (to find which chemical is "worse"), through the use of preset checklist based rankings, through experience, through past incidents and others. PHA would identify the areas with their rough hazard potential. For example, the PHA would identify that the reaction section of a chemical unit has a potential to cause widespread devastation compared to the raw material storage which may cause damage only locally. Also, the PHA could identify that the Reactor, on failure of brine circulation for reactor cooling, could result in a runaway reaction, with potential for major damage.

 

HAZOP study

A HAZOP study or HAZOP analysis is a structured technique that attempts to identify hazard and operability concerns through a formal design scrutiny using certain key "Guidewords" (such as NONE, MORE OF, AS WELL AS , OTHER THAN etc.) and deviation "Parameters" (flow, temperature, pressure etc.) . The study is conducted by a Team and discussion is focused on predetermined "Nodes" or sections of manageable dimension. Any identified and significant deviation is studied in detail for causes, protections provided and consequences. When consequence is not acceptable. the HAZOP Team suggests remedial measures where possible. HAZOP studies have become an integral part of any new design, any plant modification and increasingly used to evaluate existing plant designs for ensuring maximum compliance to latest safety norms. In addition, as the name suggests, HAZ- "OP" studies are also important from the "operations" angle, usually synonymous with plant availability and smooth, trouble free operation. Despite the early introduction of HAZOP as a formal technique by ICI in the 1960s, it still remains the most powerful hazard identification technique for process plants. It usually also forms the basis for formal Quantitative Risk Assessment or QRA studies by identifying failure cases for detailed quantitative examination in a QRA.
The HAZOP would identify scenarios that need to be evaluated during detailed risk analysis. For example one of the HAZOP recommendations could be " Evaluate through QRA whether there is a need for an additional SDV(Shut Down Valve) on the line. Similarly, there would be others that are evaluated during Risk Analysis.
"Risk" is a function of consequence effect as well as frequency of occurrence. For example, an incident could occur once a year but kill 365 people and another could occur once a day and kill 1 person each time. Clearly, both incidents kill 365 people in a year, but their characteristics are totally different. Risk analysis consists of identifying the events that contribute to the discrete risk at different locations away from the facility and summarising them. For example, an "Individual " located a kilometer away from Factory Z could be exposed to a "Risk" R, which consists 20% due to an incident (say a rupture of a Reactor in the plant, 22.5% due to failure and fire of a storage tank etc. Risk analysis analyses these contributions to understand the components contributing to the risk (contribution by frequency or consequence).

 

Risk Assessment

Having analysed the risk contributors at different locations, the next step is to identify recommendations that result in Risk reduction where it is unacceptable. This activity could involve a decision as to whether to build a 6 lakh Rs. bund wall around a vessel resulting in a 14% risk reduction or whether buying a SDV for 4 lakh Rs. giving a risk reduction benefit of 12%. Cost benefit analysis is carried out (after of course putting a value to human life) and the optimum recommendations worked out. This subject is highly structured and if used properly, could be used to great benefit, as only meaningful recommendations (which actually result in benefit to society) are implemented as part of the safety program of a chemical industry.