Health & Safety including Dust Control

is safe for such use or made safe by some means. This applies to both mechanical and electrical equipment. In order to keep this cost effective, whichever path is taken depends to a large extent on the equipment. If it is for example an electric motor it may be more cost effective to replace it with an ATEX approved version, reduce the zone by containment of the dust or remove the motor out of the area. However, if it is a large item of mechanical equipment for example, it may be very expensive to replace and may not be manufactured in an ATEX approved version, in which case assessment/modification may be the only solution.

more expensive option. The regulations call for you to consider if the material which is creating the hazardous zone can be substituted, if this is not possible then all steps must be taken to reduce the extent of the hazardous are, hence a zone reduction exercise should be the next step one takes. When designing new plant or assessing current installation careful consideration should be made to the containment of dust, ie keep it inside the process equipment. Remove it at source, ie use effective local exhaust ventilation. And another quite often overlooked technique can be to consider handling the bulk material with more care, limit the amount of turnover points from conveyors and reduce the heights which bulk solids will fall within the process, mitigating additional attrition and reducing fines liberation.

When designing new plant or assessing current installation careful consideration should be made to the containment of dust

Some processes I have seen often just move dust around, extract it from the location only to deliver it back into the process very close to where it was removed or even upstream so the dust is circling around. The less fines you continue to move throughout the process the lower probability you will have for potential primary and secondary releases, therefore less hazardous zones and lower risk.

The techniques and methodology used to reduce zone size and classification in a cost effective way varies and in some cases is unique to the plant or process being considered. Having a good understanding of explosion science is important to this process so that solutions are based on scientific fact and not on such criteria as (an often seen phrase) “anecdotal evidence”. It is important that all safety systems are fully designed and justified and the same applies for changes to zone classification and extent.

Equipment used within a hazardous area must be suitable for the zone in which it is located and must not represent a viable ignition source to the flammable materials being used in the area. This can be achieved by selecting new equipment according to the areas ATEX specification, but what about existing equipment? If non ATEX certified equipment is in place it can remain providing it can be justified by assessment, that it

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In this example such assessments would follow the guidance given in the European standards for Non electrical equipment for potentially explosive atmospheres, EN 13463-1, an ignition hazard assessment can be performed and recorded to justify why the equipment can remain in place. Risk is a product of probability and consequence, ATEX certified equipment only reduces the probability of an effective ignition source being present, other factors such as reducing the likelihood of a flammable atmosphere or reducing the consequence of an event by some form of mitigation may prove to reduce the risk to an acceptable level without the replacement of existing equipment.

It is very important to understand that an appreciation of DSEAR / ATEX 137 and the science involved via a short course is not the same as gaining an in depth knowledge of the subject. Assessments and therefore risks will vary according to the level of knowledge, training, experience and hence competency possessed by the individual completing the tasks. In many large plants and complex cases it may be wise and often prove cost effective to seek advice and assistance from experienced professionals.

This then raises two further questions.

Who is a competent person?

What is a suitable and sufficient risk assessment? Both questions seem easy to answer but difficult to defend We will leave that debate for another time.

For more information contact GexCon UK on tel: +44 (0)1695 726565 or visit: www.gexcon.co.uk

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