Process Safety Data: Is Your Data Valid?

It is not uncommon to find companies that fail to properly assess and correctly interpret the hazardous potential of chemical reactions performed in their organisations. But unfortunately it is not alone. Newsfeeds are replete with industrial accidents, some of them catastrophic, that could have been prevented had the right process safety data been available.

Following a major incident, many organisations attempt to preclude a recurrence by implementing data acquisition procedures and programs, and sometimes even invest in their own process safety labs. Their efforts are understandable and well-meaning, but are often not enough. In our experience, many of these companies overlook to actualise, update, and review the data they collect.

Process safety information should not be seen as a collection of static documents grouped in a binder but as a live ecosystem of knowledge that evolves during the lifecycle of the process.

It is usually necessary to perform new experimental data acquisition following process or parameter modification to answer questions such as:

• Is the fluid more corrosive when temperature increases?
• Is the mixture less stable thermally if the recipe is changed even slightly?
• Is the safety valve still able to evacuate the flow rate of gases?

When process safety data collection and testing is done properly, this shall maximise safety and direct resources where they are truly needed. To get there, it is essential that the entire organisation develop competency around process safety data: which data to collect, when and how to get and produce data, and how to interpret them.

Different strategies for the collection of process safety data are discussed in an available publication by DEKRA Insight entitled “Process Safety Data: A Critical Ingredient in Process Safety Excellence”.

Starting the process

Management of flash fires, explosions, and runaway reactions resulting from the use, handling, and processing of flammable liquids, explosible powders, and reactive/unstable materials often involves taking the following steps:

Establishing a sound process safety management system and competency within the organisation that is based on appropriate data, information, expertise, and experience in all related process safety areas, including:

• Having appropriate data for the understanding of the flammability, electrostatic properties, reactivity, and explosion characteristics of the fuel(s)
• Understanding of all operations and processes
• Identification of locations where flammable atmospheres are, or could be, present during normal and foreseeable abnormal operating conditions
• Identification of potential ignition sources
• Defining the “Basis of Safety” including proper process and facility design to prevent and/or minimise the occurrence of flash fires, explosions, and uncontrolled reactions

Establishing a safety culture that starts at the top but pervades consistently through the whole organisation

Regular review and maintenance of data, information, behaviours, systems, facilities, and equipment

Process safety data – Flash fires & explosions

The First Step – Formation of a flammable/explosible Atmosphere

A flammable atmosphere is formed when a sufficient amount of a fuel (gas, vapour, or/and dust) is mixed (suspended) with an oxidant. As is highlighted above, in order to assess flash fire and explosion hazards in a facility and to select the most appropriate basis of safety, fire and explosion characteristics of the fuel(s) that could be present must be determined for handling and processing conditions.

The first step in the assessment of flash fire and explosion hazards is to establish whether a gas, vapour, and/or dust cloud atmosphere, if formed, is flammable/explosible under the process/operating conditions.

Determining ignition sensitivity

Once the flammability/explosibility of a material or an atmosphere is confirmed, then testing normally falls into two groups, “Ignition Sensitivity” and “Explosion Severity”.

Ignition Sensitivity – There are a number of tests that are designed to determine the sensitivity of a flammable atmosphere to ignition by the type of ignition source(s) that could be present during normal and also foreseeable abnormal operating conditions.

So, the selection of appropriate “ignition sensitivity” test(s) requires a good understanding of the type of ignition source(s) that could be associated with specific unit operations and activities in a facility.

Determining explosion severity

The severity of an explosion that is caused by the ignition of a flammable gas, vapour, and/or dust cloud atmosphere in a confined space/enclosure is defined by the (maximum) rate of pressure rise resulting from the expanding fire ball and the maximum explosion pressure.

The maximum explosion pressure and maximum rate of pressure rise are typically measured in a 20-litre or a 1m3 spherical vessel. These values are used to calculate the Deflagration Index for a gas/vapour atmosphere (Kg) or a dust cloud atmosphere (Kst) to classify the atmosphere’s explosion severity.

Process safety data – Chemical reactivity

Chemical reactions are frequently associated with considerable heat exchange. Large amounts of energy can be released when decomposition reactions are initiated unintentionally through inappropriate operations such as loss of power, loss of cooling, loss of agitation, and/or unintentional mixing (e.g. waste/disposal) of incompatible chemicals.

This can cause a destructive force resulting in the rapid release of the reaction products, including toxic gases and vapours. Hence, the identification, assessment, and characterisation of both intended and, more importantly, unintended exothermic reactions are critical for ensuring the safe scale-up and operation of a chemical process (Ref 10, 11, 12, & 13).

Chemical reactivity hazards can be grouped into a number of general categories including:

• Self-reactive materials (e.g., polymerising; decomposing; rearranging),
• Intentional mixing of two or more chemicals in a chemical process.
• Reactive with other materials (e.g., oxygen; water), and

Safety and environmental regulations require systematic risk analysis to be carried out on potentially-hazardous processes in production plants, pilot plants, and auxiliary installations.

The risk-assessment strategy would generally include determining heats of reaction/decomposition, exotherm initiation (onset) temperature, pressure generation, water reactivity, sensitivity to light and air, and spontaneous combustion.

“Design of Runaway Scenario” is a powerful method that can be employed for conducting thermal process safety analysis of a batch, semi-batch, or continuous process, taking into account the thermal characteristics of both the desired and unwanted reactions.

Concluding remarks

In our work, we see too often situations where large risk goes unnoticed, process hazard analysis efforts are invalid or flawed, or vital process safety data are entirely absent. These breakdowns create major risks and ruin the well-intended efforts of the organisation.

Process safety data should be managed in an active knowledge management system that is sustainable for the organisation. Failing to do so means you aren’t getting valid information—leaving you at risk of severe consequences as processes could be in an intrinsically hazardous state without anyone being aware.

Invalid data can also cost the organisation when unnecessary safeguards are implemented or preventative measures are inadequately designed.

Valid process safety data is critical if leaders are to make sound judgements. Without them no PSM can work. Testing Guide for Management of Flash Fires, Explosions, and Runaway Reactions provides a starting point for this basis of safety and helps leaders get ahead of the risks created by the use or presence of flammable gases and liquids, explosible powders and dusts, and unstable or reactive materials.