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How to develop a process safety strategy for thermal runaway

If you want to learn about how a chemical process safety strategy is developed for potential thermal runaway or if you’re curious to learn more about how the process safety industry operates, then you’ve come to the right place.

This blog will review the key stages for developing a chemical process safety strategy for thermal runaway.

Before we take a look at how a chemical safety strategy is developed, here’s a quick overview of what chemical process safety is and what lessons have been learned from previous major runaway incidents such as Flixborough, UK and Bhopal, India.

Thermal Runaway Cycle - Current, Temperature, Pressure and Reaction Rate

What is chemical process safety?

Chemical process safety aims to prevent potential accidents and inadvertent incidents caused by an industrial related chemical reaction.

As a comprehensive assessment, chemical process safety aims to restrict any dangerous materials or energy that may be caused because of human error, overheating and cooling capacity failures, technical faults, or a series of unfortunate coincidences.

As a thorough HSE assessment, chemical process safety uses a framework consisting of multiple techniques, technologies, and models to identify, quantify and understand potential chemical hazards, risks, and dangers to a working environment.

Analysis indicates that previous thermal runaway incidents occurred as a result of:

  • Inadequate understanding of thermochemistry and chemistry.

  • Insufficient engineering design for reactor heat transfer systems.

  • Inadequate control and safety backup systems. This includes emergency relief systems, process vents and other engineering controls.

  • Poorly written batch procedures and insufficient operator training.

  • Ineffective internal process safety leadership and management practices.

The first stage in developing a chemical process safety strategy is to identify any potential chemical reactivity hazards. This is sometimes known as a screening or a preliminary hazard analysis (PHA).

As a high-level screening process, this stage is not only used to identify hazards but to also describe, rank and understand possible consequences and probabilities of hazard occurrence.

To complete the screening stage when developing a chemical process safety, a solid theoretical understanding of chemistry is required. This is because a detailed review of the molecular structures of known reactive groups alongside the balancing of chemical equations should be conducted. This is especially true if you must consider multiple chemical materials, chemical interactions, or energy flow.

Case studies, data reports and literature reviews should also be undertaken in the screening phase. There are multiple accident databases, statistics, government reports and expert papers that can all be accessed and linked back to the chemicals and equipment present in the workplace when creating a process safety strategy. The same goes for the creation of SDSs, Heat of Reaction Theoretical Calculations and CHETAH calculations.

Small-scale thermal stability tests, such as the Differential Scanning Calorimetry (DSC) are also conducted to identify potential hazards such as component decomposition or secondary reaction initiation should thermal runaway occur. At Sigma-HSE, we are able to undertake a range of small scale thermal screening tests including DSC, ARC, Carius Tube and VSP.

Identifying Chemical Reactivity Hazards (Screening)

The first stage in developing a chemical process safety strategy is to identify potential chemical reactivity. This is known as a screening or a preliminary hazard analysis (PHA).

As a high-level screening process, this stage is used to identify hazards and describe, rank and understand possible consequences and probabilities of hazard occurrence.

To complete the screening stage when developing a chemical process safety, a solid theoretical understanding of chemistry is required. This is because a detailed review of the molecular structures of known reactive groups alongside the balancing of chemical equations should be conducted. This is especially true if you must consider multiple chemical materials, chemical interactions, or energy flow.

Case studies, data reports and literature reviews should also be undertaken in the screening phase. There are multiple accident databases, statistics, government reports and expert papers that can all be accessed and linked back to the chemicals and equipment present in the workplace when creating a process safety strategy.

The same goes for the creation of SDSs, Heat of Reaction Theoretical Calculations and CHETAH calculations.

Small-scale thermal stability tests, such as Differential Scanning Calorimetry (DSC) are also conducted to identify potential hazards such as component decomposition or secondary reaction initiation should thermal runaway occur. At Sigma-HSE, we are able to undertake a range small scale thermal screening tests including DSC, ARC, Carius Tube and VSP.

Assessing Desired Reactions

There are rigorous scientific frameworks in place that aid in the creation of a chemical process safety strategy. One of these processes is an assessment of desired and potentially undesired reactions. This can include the investigation of thermal events, heat transfer, mixing, mass transfer, gas evolution, the stability of starting material, reaction mass, and other resulting products.

To assess the desired reaction, a Reaction Calorimetry test on the reaction of interest and quench is conducted. The questions asked at this stage are how much heat or gas has been generated and is there adequate cooling?

The Reaction Calorimeter is designed for measuring heat profiles, chemical conversion, and heat transfer under process-like conditions. This test allows chemical and safety engineers to optimize processes under safe conditions while determining critical process parameters which can ultimately reduce the risk of failures on a large scale.

Assessing Undesired Reactions

When assessing the undesired or decomposition reaction, an Adiabatic Calorimetry test for temperature, pressure and time is conducted. This test aims to measure the speed at which heat or gas is generated. This will determine whether a pressure relief system is adequate.

Adiabatic calorimeter testing provides data for relief system design, safe scale-up of chemical processes, and changes to ingredients. Safe process design requires knowledge of chemical reaction rates, character, and energy release.

Review Batch Directions and Operator Training

The creation of operator training programmes and other continual observation and adjustment review procedures is another important step in developing a chemical process safety strategy.

Batch review meetings are designed to ensure that all quality and safety related functions are consistently reviewed and updated to the highest possible standards.  All levels from management to operators should be made aware of changes, updates, revisions, verification activities and policies resulting from batch direction review meetings.

Well informed accessible documentation will aid in the constant monitoring of systems, products, and potential reactions. Furthermore, this information can provide reference guides to the consequences of inadvertent activities such as temperature, time or chemical mixing can be great tools for operators. This operating documentation/report is important for areas that have the highest chemical hazard potential and should be updated and/or produced regularly.

Process Safety Strategy for Thermal Runaway Summary

When developing a chemical process safety strategy for potential thermal runaway, the below key stages should always be remembered.

  • Identifying Chemical Reactivity Hazards (Screening)

  • Assessing the Desired and Undesired Reaction

  • Review Batch Directions and Operator Training

This strategy aids in outlining and formalising the processes for identifying hazards and allows companies to establish safety measures that mitigate potential hazards and risks for thermal runaway.

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