SINHA ROY, P. (2017). The importance of chemical and operational safety and hazard assessment. PHILICA.COM Article number 1154.
The importance of chemical and operational safety and hazard assessment

PARTHA SINHA ROYunconfirmed user (Pharmaceutical Science and Engineering (Process Chemistry & Chemical Technology), University of Leeds)

Published in

During early stages of plant design and development chemical process route selection demands a high consideration over the factors such as inherent safety, health and environment related to the plant along with the economic aspects. These factors are to be evaluated by looking at the worst feasible impacts that can cause catastrophic emission. Thus, an integrated index called Inherent Chemical Process Route Index can be proposed that considers the potential toxicological impacts on the environment and as well as on the occupational health and the potential chemical and process safety impacts within the plants.

1. Introduction: “To know is to survive and to ignore fundamentals is to court disaster” [H.H. Fawcett and W.S. Wood, Safety and Accident Prevention in Chemical Operations, 2nd ed., New York: Wiley, 1982, p. 1]. Hence, the basic fundamental aspects related to chemical and operational process safety and hazards are important issues since the technology governing the chemical and operational process have become quite intricate. Safety in today’s date lays its impact on productions and adds various technical and intricate practices, concepts and theories in a highly scientific discipline.[1]

2. Studies:

2.1 Accidents and Loss Statistics:

Ø  Useful tool for measuring the efficiency of safety programs

Ø  Statistics influence on determination of process safety

Ø  Two main statistical methods that help report the total number of fatalities and/or accidents for a constant number of workers under a certain period of time

2.1.1 Occupational Safety and Health Administration (OSHA) incidence rate:

Actually, OSHA incidence rate typically covers cases/100 workers years. By assumption, one worker contains 2000 hours [50 work weeks/year  40 hours/week = 200,000 hours of worker being exposed to hazards]. The OSHA incidence rate supplies necessary information of injuries, illness and even fatalities associated with the work along with a relatively better and standard result of accidents of the employees compared to the single system of fatalities. [1]

2.1.2 Fatal Accident Rate (FAR):

This statistical method is extensively used by the UK chemical Industries. The method is based on the number of fatalities reporting on 1000 workers during their whole life work. Assumption is made for an employee to be working for 50 years [hence, 108 working hours]. [1] 

2.2     HAZOP Study:

The Hazard and Operability (HAZOP) study is the one which has been widely accepted by the chemical process industries as well as by the Regulatory Authorities. The study is based on P&IFDS (Piping and Instrumental Flow Diagrams) to account how the plant can be affected when the general parameters associated with the pipes and vessels are deviated. This is known as Chemical Process HAZOP. Besides, another critical HAZOP study which encounters the effect caused due to the changes in design-layout specifies the HAZOPed diagrams or Mechanical Handling Diagrams (MHDs). HAZOP is a stringent multi-disciplinary and systematic method and ensures and analyses all the changes in temperature, pressure and flow in the system thoroughly. Complete identifications of the hazards are taken into account which is solely dependent on perfection and efficiency of the team involved in the study. [2]

2.3     SCHAZOP Study:

“The adapted HAZOP approach for safety management assessment is called the SCHAZOP methodology” [Kennedy and Kirwan, 1996]. This methodology is typically useful for estimating the parameter related to the “safety culture” which influences the system of the safety management. [2]

2.4     Fault Tree Analysis:

This is another study-tool for the assessment of safety related to intricate systems of Engineering. The first step in this analysis is qualitative study which deduces the expression to describe the top-event logically with the minimum cut-sets and the second step is quantitative study that estimates the probabilities with which the top-event is likely to take place. This quantitative analysis to calculate the probabilities is based on the failure events associated with the basic components. [3]

2.5     Event Tree Analysis:

This method of analysis complements the Fault Tree Analysis. Event tree analysis begins with the top events thereby following the series of probable results that can take place which mainly depend on whether particular conditions are met along the series or not. The basic safety orientation of this analysis is specifically appropriate for the analysis of these systems in which time plays a significantly vital role. Example: when further rise of an accident can be avoided by human interruption within a certain range of time, like water-valve is opened for quenching a reaction being exothermic in nature. An operation thus is considered to be successful or individual safety function is considered to have been failed based on the work done ahead within the time starting from the event of top-failure. This, however, decides the course of the initiating event for controlling hazards in the protective layers. [4]

2.6     Failure modes and Effective Analysis (FMEA):

This systematic method of analysis is a tool for estimating each component to assess the impact of the failure due to system behavior. A failure mode which can be a symptom or a condition in which failure of hardware happens is marked as a function devoid of any demand or beyond the stage of tolerance or just a physical parameter like leakage being observed in the time of inspection. [5] 

2.7 Substance, Reactivity, Equipment and Safety-Technology (SREST) layers assessment:

This assessment method is very useful in collecting data related to physical, environmental, chemical and toxicity properties , assessing the materials for health and safety related issues taking help from the collected data, assuming reaction incompatibilities from the charts where all the incompatibilities are listed, identification of probable worst accidental cases and using principles of health and safety for choosing the most favorable chemical design-process, synthesis-routes and reaction-conditions. [6]

3. Equipments: The personal protective equipments are as follows:



Body protection

Sealer zippers and double zippers, storm flaps, zipper placements, seam closures: type I – sewn seams, type II – sewn and bound seams, type III – no sewing required (NSR) seams, type IV – sewn and strapped seams (highest protection).

Hand and Finger protection

Gloves, mitts, cots.


Hard hats, welding helmets.


Goggles, safety glasses.


Face shields.


Ear plugs.


Respirators, SCBAs.

Ankle & foot

Boots & metatarsal shields.


Large scale-reactors:

v  Glass bonded with steel [Pfaudler ] type

v  Steel alloy vessels [Hastalloy, 316SS] type

v  PTFE lined vessel [to check HF corrosion] type

v  Rubber lined vessel [for acidic reactions: Acetic acid attacks stainless steel of Grade 316] type [8]

4. Experiments:

4.1 Experiments for assessing “Domino Effect” in chemical industries:

Domino effect is a factor which initiates hazard associated with the spillage of hazardous materials that can give rise to accidents like fire caused due to flame leading to detriments of vessels or lines linked up with pipes. [9]

4.2 Systems Thinking Experimental Theory:

This experimental theory represents a system in which operational safety is an outcome of the cross-connection between the analysis of initial safety, preventive analysis or feed-forward and the operating experience. [10]

Systems theory provides a chance for improving the operational safety in chemical process plants in a cyclical pattern. In this system the feedback loops help to control the efficiency of the entire cyclical process along with the system’s validity. The general framework of this system acts like: [10]

The operational safety index “PROCESO” evaluates the innovative method related to the self-assessment in chemical industries.

 5. Conclusion:

Thus, hazard identification is the utmost crucial step in any sort of assessment of risk. In the area of process safety HAZOP studies and FMEA methods have been successful in that they have acquired a world-wide acceptance. However, they remain a significant challenge to apply these methodologies. And these in turn link with the quality of the human imagination in case of eliciting the failure events and subsequent casual pathways, the depth of resultants, application over the operational modes, the repetitive characteristic of the methods and the substantial effort expended in performing this vital step within risk management practice. 

6. References:

1. Crowl, D. A., Louvar, J. F. (2002). Chemical Process Safety, Fundamentals with Applications, Second Edition, by Prentice Hall PTR, Prentice-Hall, Inc. , Upper Saddle River, New Jersey 07458. Chapter-1, 1-1 Safety Programs, 1-2 Engineering Ethics, 1-3 Accident and Loss Statistics, p. 1-17.

2. Kennedy, R., Kirwan, B. (1998).Development of a Hazard and Operability-based method for identifying safety management vulnerabilities in high risk systems. Safety Science, 30 (3), p. 249-274.

3. Rao, K. D et al. (2009). Dynamic Fault Tree Analysis using Monte Carlo Simulation in Probabilistic Safety Assessment. Reliability Engineering & System Safety, 94 (4), p. 872-883.

 4. Cameron, I. T., Raman, R. (2005). Process Systems Risk Management, Process Systems Engineering Volume 6, Estimating the likelihood of incident, p. 320.

5. Santamaria Ramiro, J.M., Brana Aisa, P.A. Risk Analysis & Reduction in the Chemical Process Industry, chap: 2, Hazard Identification Techniques, p. 54-55, Blackie Academic & Professional, An Imprint of Chapman & Hall, London-Weinheim-New York-Tokyo-Melbourne-Madras.

6. Shah, S. et al. (2005). Assessment of Chemical process hazards in early design stages. Journal of Loss Prevention in the Process Industries, 18 (4-6), p. 335-352.

7. Covan J. Safety Engineering, chap: 4, Safety Skills: Personal protective Equipments, p. 123. A Wiley Interscience Publication, John Wiley 7 Sons, Inc., New York-Chichester-Brisbane-Toronto-Singapore.

8. Abbasi, T. et al. (2010). A New Method for assessing Domino-Effect in Chemical Process Industry. Journal of Hazardous Materials, 182 (1-3), p. 416-426.

9. Marono, M. et al. (2006). The “PROCESO” index: a new methodology for the evaluation of operational safety in the chemical industry. Reliability Engineering & System Safety, 91 (3), p. 349-361.




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SINHA ROY, P. (2017). The importance of chemical and operational safety and hazard assessment. PHILICA.COM Article number 1154.

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