Hazardous Area Classifications (HAC) – how to avoid over-zoning
In most organisations, risk assessments err on the side of safety. Whilst this should not be deemed to be an issue, it may be over cautious as it can result in large hazardous areas being designated and, in some cases, a higher than necessary classification of zoning (i.e. Zone 1/21 instead of Zone 2/22) or by blanket zoning an entire area.
This can cause a large amount of financial expense in terms of purchasing and maintaining ATEX certified equipment. We have worked with many companies to help them save money by correctly zoning their factories & production facilities.
“…Zone 0 or Zone 1 areas should be minimised in number and extent by design or suitable operating procedures. In other words, plants and installations should be mainly Zone 2 or non-hazardous.
Where release of flammable materials is unavoidable, process equipment items should be limited to those which give secondary grade releases or, failing this (that is where primary or continuous grade releases are unavoidable), the releases should be of very limited quantity and rate. In carrying out area classification, these principles should receive prime consideration.
Where necessary, the design, operation and location of process equipment should ensure that, even when it is operating abnormally, the amount of flammable material released into the atmosphere is minimised, so as to reduce the extent of the hazardous area.”
Therefore, when preparing a risk assessment report, you should seek to identify the possible sources of release and their bearing on the hazardous area classification. You should also ensure that any Zones identified are a realistic interpretation of the actual situation and not an over-specification.
The general report format for assessing Unit Operations should include sections as follows;
- Overview: The Unit Operation is defined and the presence of a flammable atmosphere in normal, or foreseeable abnormal, an operation is considered. If a flammable atmosphere can’t occur, then the assessment stops there.
- Presence of an Ignition Source: It is not the intention, at this stage, to determine all potential ignition sources, but just to confirm that there is at least one. This should also take into consideration the possibility of an unintentional ignition source being brought into the hazardous area (i.e. maintenance or measuring equipment).
- Discussion of Risk: If there is a potential for a flammable atmosphere and an ignition source, then there is a discussion to determine the risk to people and whether actions are required.
- Basis of Safety: The chosen basis of safety for the unit operation is considered along with its implications on adjacent units. You should also include the basis of safety and its physical location in the site.
- Hazardous Area Classification (HAC): If there is a requirement in the Basis of Safety to control ignition sources, then the next section, Hazardous Area Classification (HAC), gives the relevant zones.
- Recommendations: Finally, there are recommendations. Once the recommendations have been implemented, as far as reasonably practicable, then the Basis of Safety should be ‘sound’.
Auditing of the Implementation of the Recommendations
The correct application of Hazardous Area Classification (HAC) results in an appropriate budgetary spend on safety in the workplace. Minimising the use of expensive ‘Ex’ rated equipment, if it is required, helps to reduce the level of equipment down from potential Category 2 to Category 3. This can aid in reducing installation costs and replacement component stock levels.