Risk Analysis (PHA techniques)
PHA means “Preliminary Hazard Analysis” or risk analysis. PHA techniques were created by the armed forces of the United States of America, although they were later assimilated by various chemical industries, which gave them different names. In Spanish, we talk about PHA techniques or APR techniques.
The legislation requires studies of risk analysis, or PHA techniques, although it does not provide a method or an orientation protocol. Therefore, companies, such as Tandem HSE, offer the possibility of carrying out these studies prior to the construction of a chemical plant according to the main variants adopted by this industry: HAZOP, WHAT-IF and FMEA.
All PHA techniques are applied during the design and development phases of industrial facilities or plants, as well as during their exploitation.
- Raw materials, intermediate products and products of a process according to the reactivity of each one of them.
- All equipment of a plant or a production line, whatever applies.
- Facilities and security equipment.
- Individual operations parts of a process, maintenance operations, start-ups and stops.
- Process environment and limits between each of the components of a system.
In order to apply the PHA techniques, one or more qualified professionals are required to be provided with the basic design criteria of the plant, what equipment will be used even without specifying the finest details, and what materials are going to be involved in the process, from raw materials to final products, by-products and emissions.
This attempts to detect the weak points of the production chain: where a hypothetical accident would be most likely to occur, and if this accident could be avoided with different sizes or varying the distribution of some equipment in the plant or improving security measures in those scenarios.
The second part of a PHA technique is to propose solutions that reinforce safety at points that have been detected as potentially weak or more prone to accidents, in case of exceeding the operating conditions due to the failure of a digital controller or an unforeseen natural disaster.
Since these estimates are made on data that are not yet definitive, computer models are not usually used for preliminary risk assessment. Despite this, this stage, mandatory by law, requires little economic investment.
Now let us do a quick review of the specific PHA techniques and the ones derived from them mostly used in the chemical industry.
It is a fairly intuitive method, used to detect possible risks in the pharmaceutical industry, in those that work with oil and those that mostly handle gases. The method is based on asking questions—almost in brainstorming mode—about what would happen if such a thing happened, and then make schematic drawings of the situation.
For example, what would happen if a wire gets stripped because a corrosive substance falls on it? And if the operator in charge of a certain non-mechanizable stage suffers a sudden fainting? How does it influence in which position that operator falls, for the safety of that person, the safety of other workers and the safety of the plant?
It is a qualitative risk assessment technique, but it is a viable alternative to HAZOP.
It is the preferred technique in risk analysis in chemical industry plants. It has the particularity that it is applied throughout the life of an industrial plant, from its design to its closure, and is carried out with a team of several professionals, each of them specialized in a specific area.
HAZOP allows the identification of more dangers, and to propose corrective measures, since the control is constant. It does not require much economic investment if you take into account the good results it offers, although it does involve an investment in time by the multidisciplinary team responsible for the study, to implement improvements when any possible danger is detected (causes, consequences and control measures if any).
It is based on the methodical analysis of the failures that can take place in individual pieces. It does not consider human errors as such, but as the consequence of a problem in a machine or in an operation.
The FMEA method alone can be incomplete, although it is an excellent measure of support in the prevention of risks during prototype tests, during the construction stage and to detect specific failures, in a specific operation unit.
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