How many times have you said, “You can’t smoke here, it’s a hazardous area!”? The most memorable reply that I’ve heard was “This area isn’t dangerous and there are no video cameras”.
Many people, even in industry, don’t understand what a hazardous area is. Read on, this blog post will go through some of the basic compliance requirements of hazardous areas.
A hazardous area is a place where an explosive atmosphere may exist due to concentrations of gases or dusts. Obvious examples include anything to do with petrol, solvents and light hydrocarbons or handling of sugar, flour and grain. For an example, have a look at the 2008 Georgia Sugar Refinery Explosion.
This post isn’t going to get into the stoichiometry of explosions, there is heaps of that information on the internet. The concept of air and flammable material leading to combustion is easy, the harder bit is what to do to prevent it, avoid loss of life and equipment damage, and stay out of jail.
In Queensland, the Work Health and Safety Regulation tries to avoid ignition of hazardous atmospheres by controlling the ignition sources that are inside (refer to sections 52 and 355). Note that the Regulation considers hazardous atmospheres to start at 5% of the lower explosive limit of the gas (section 51).
Although the Regulation tells you that you “must”, it doesn’t tell you how. The ‘how’ starts in AS/NZS 3000 Wiring Rules which references the AS/NZS 60079 Explosive atmospheres set of standards. The Wiring Rules are called under the Electrical Safety Regulation, which means they and subsequent “you shall” statements are a requirement.
Hazardous Area Design and Classification
The Wiring Rules tell us that the responsibility for classification of the hazardous area rests with the parties in control of the installation. So, if you are running a plant/process/factory, you need to know what chemicals you are using, whether they can chemically give rise to a flammable atmosphere, whether they can be released in enough quantity to form a flammable atmosphere and how far this atmosphere will extend. This is not a common skill set and Black Square Engineering can assist (no, we aren’t ashamed of that plug).
The classification of a hazardous area is to the AS/NZS 60079.10 Explosive atmospheres - Classification of areas pair of standards (part 1 for gases and part 2 for dusts). As always, the ‘hierarchy of control’ is required to be considered. It isn’t often that elimination of the chemical producing the hazardous atmosphere can be performed (what’s a sugar mill without the sugar?). However, there are some basic measures that can nearly always be performed but usually aren’t. One measure is putting a lid on open tanks. This will decrease approximately 113m2 of floor area around the tank from zone 1 to zone 2. In addition to lower explosion risk, this allows the use of less expensive equipment in the zone and can have significant cost savings.
We did a job at this fibreglass factory with a big open resin tank inside a shed. The staff were getting a bit high off the resin fumes – also not ideal. Control your vapours, there really are lots of reasons.
After classifying the hazardous area (and minimising the hazard as far as reasonably practicable), a good classifier (like Black Square Engineering and we aren’t ashamed of that plug either) will provide you with drawings of the zone extents around plant and equipment. The next step is to select equipment that is suitable for use in that zone. This is where AS/NZS 60079.14 Explosive atmospheres - Design selection, erection and initial inspection is used, this sets out the default methods of protection to be used in which zone.
Hazardous Area Installation and Maintenance
Usually zone classification and equipment selection are done well. The installation and maintenance of the plant is sometimes overlooked. Australia has nationally recognised competencies to AS/NZS 60079.14 Explosive atmospheres - Design selection, erection and initial inspection and AS/NZS 4761.1 Competencies for working with electrical equipment for hazardous areas (EEHA) for installation and maintenance of equipment in hazardous areas. These usually include specific modules for each method of explosion protection. Your usual Sparky will probably give the installation a fair crack, but if they don’t know what they are doing they’ll leave half of the bolts out of your ex ‘d’ j-box (yes, we’ve seen this happen and no you can’t).
There is one last compliance requirement that is nearly always overlooked. The pre-energisation audit of the electrical equipment is the final barrier to an unsafe installation being entered into service. The audit needs to be done by an accredited hazardous area installation auditor under the Electrical Safety Regulation (section 221). Black Square Engineering don’t have any accredited auditors, but we can help you out from the start to the finish of your hazardous area project (still not sorry for the plugs).