Tristan Pulford, Principal Consultant at Finch Consulting, delves into the core elements of how to identify and manage potentially explosive substances, emphasising how employers can recognise and mitigate hazards associated with explosive substances and atmospheres, with a primary focus on safeguarding the health and safety of workers. You can catch up on parts one and two at the bottom of this article.
Posted
31.01.2024
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Ignition Sources
When working within a potentially explosive atmosphere, identification and control of ignition sources is a vital step in ensuring the safety of workers and preventing potential explosions. Equipment that is designed for use within potentially explosive atmospheres is typically referred to as ATEX equipment named after the European directives which define their protection methodology and testing requirements.
There are various types of ignition source, such as:
Electrical Equipment:
One of the primary sources of ignition in hazardous areas is electrical equipment. DSEAR and ATEX provide strict requirements for the selection and installation of electrical equipment within potentially explosive atmospheres. Equipment designed for use in explosive atmospheres is labelled with appropriate markings, indicating its suitability for specific zones (Zone 0, Zone 1, or Zone 2 for gases and vapours, and Zone 20, Zone 21, or Zone 22 for dust atmospheres).
Hot Surfaces:
Hot surfaces, such as furnaces, heaters, or exhaust systems, can act as potential ignition sources in areas where flammable substances are present. Even equipment such as motors and conveyors can overheat and become an ignition source, so it is important that these are specified correctly. In some scenarios (such as furnaces and ovens) an ignition source is part of the process so other controls such as ventilation or detection systems are required.
Mechanical Sparks:
Mechanical equipment, including machinery with moving parts, can generate sparks through friction or mechanical impact. Similarly, to electrical equipment, mechanical equipment has a label showing the equipment has protections built in for the specific zone. Equipment predating ATEX requires an ignition risk assessment to ensure it is safe to use within an explosive atmosphere or additional controls are required.
Open Flames:
Activities involving open flames, such as welding, cutting, or brazing, pose a significant ignition risk in hazardous areas. As such hot work permits are required which, ensure the activity is properly risk assessed and control such as increased ventilation and monitoring of any explosive substances, are put in place before work is carried out.
Static Electricity:
The build-up and discharge of static electricity can be a potential ignition source and require the use of anti-static equipment, bonding and grounding procedures, and measures to minimize the risk of static discharge. This is especially the case during dust conveying through plastic pipework if the resistance is not suitably selected.
Chemical Reactions:
Uncontrolled chemical reactions within processes can lead to the release of energy and heat, potentially causing ignition. To identify the potential for this a HAZOP study is usually carried out, and suitable engineering controls are put in place to prevent a chemical reaction creating an ignition source.
Sparks from Tools:
Tools used during maintenance can generate sparks, especially if they are not properly designed or maintained. This is because certain metals when hit with enough energy can cause sparks. Control of equipment such as spades, hammers, and screw drivers are important to ensure they are used correctly and suitably specified for use within a potentially explosive atmosphere.
Compliance with DSEAR requires a holistic approach to managing ignition sources, encompassing the selection of equipment, engineering controls, safe work practices, and ongoing risk assessments. This includes the understanding of any person working in an area to ensure that they do not unintentionally introduce an ignition source into the area such as a vacuum cleaner or mobile phone.
Emergency Plans
The controls that are put in place are there to prevent any explosions or incidents, it is however an important aspect of DSEAR that emergency plans are put into place. Emergency plans should follow from the DSEAR Risk Assessment to ensure that all the hazards are included. The plan should include.
- Locations of any potentially explosive substances when in storage, or being used as part of the process
- Location of any Hazardous Areas
- A summary of the potential people affected
- Details of those responsible such as a crisis management team
- A communication plan both internally and externally
- Details of coordination between emergency services and neighbours
- Evacuation plans
- Management of emergency equipment such as firefighting or breathing apparatus required
Depending on the complexity and risk profile of site either a desktop drill or complete drill should be carried out on a periodic basis to ensure that those affected are aware of what to do.
Conclusion
This has been a summary of how to manage explosive substances and is by no means exhaustive but covers the main areas to be considered. As with all controls, there is a hierarchy associated with DSEAR which starts with the removal of the hazard and ends with safe working procedures and PPE. It is always more effective to implement engineering controls than rely on procedure.
