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Hazardex 2019 Conference Presentations - Using Equipment Protection Levels (EPLs) to break the chain.

Author : Keith Plumb, Process and Equipment Consultant at BPE Design and Support Ltd.

20 November 2018

It is clear that a hazardous area classification plus equipment selection does not constitute a complete risk assessment because an assessment of the consequences is not included. EN IEC 60079-10-1 reflects this and states,” Subsequent to the completion of the area classification, a risk assessment may be carried out….”. It then goes on to suggest that as a result of the risk assessment the required EPL may be higher or lower than normal.

In the UK the requirements are mandatory because the Dangerous Substances and Explosive Atmospheres Regulations require a risk assessment to be carried out and that risk assessment needs to include “the scale of the anticipated effects of a ?re or an explosion”.

Carrying out such a risk assessment allows the chain: grade of release leading directly to a hazardous zone directly leading to an EPL to be broken. Which means that a number of scenarios can be considered e.g. unusually high consequences or unusually low consequences (resulting from a small scale, for example), which in turn can result in changes to the EPLs selected for equipment to be used in the designated hazardous zones.

Another area where breaking the chain can be advantageous is in respect of blanket zoning which is frequently used to allow future proofing and potentially a simpler operating and maintenance regime.

This paper presents practical examples of breaking the chain when the consequences of an explosion would be high or low and when blanket zoning is advantageous.

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Keith Plumb is Process and Equipment Consultant at BPE Design and Support Ltd. He is on the Pharma Special Interest Group and Board of Trustees at IChemE and Visiting Lecturer at the University of Chester covering Food and Pharmaceutical Engineering.

He has more than 40 years’ experience in the pharmaceutical, biopharmaceutical, fine chemical and allied process industries. His experience covers multinational manufacturing companies, engineering design companies and consultancies.

Keith’s specialties are: Dust explosion risk reduction; Dust hazardous area classification; ATEX and non-electrical equipment; Safety of machinery in the process industries and Process mechanical design for pressure equipment.


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