Jeremy Procter, Convenor of the European Standards Committee responsible for Machine Guards, and Managing Director of Procter Machine Guarding, explains how the international standard ISO 13857 relates to the two well known reach distance standards EN 294 and EN 811.
Machine designers in the UK and Europe are familiar with designing guarding in accordance with the requirements of EN 294 Safety of machinery - Safety distances to prevent danger zones being reached by the upper limbs, but this standard has now been superseded and replaced by a European/International standard EN ISO 13857:2008 Safety of machinery - Safety distances to prevent hazard zones being reached by upper and lower limbs. Furthermore, this standard also supersedes and replaces EN 811, Safety of machinery - Safety distances to prevent danger zones being reached by the lower limbs. Of course, the British Standard equivalents of these three are BS EN ISO 13857:2008, BS EN 294:1992 and BS EN 811:1997.
Fortunately the new standard is, in essence, an amalgamation of the two previous standards, with all of the principles, tabulated data and safety distance unchanged. There has been some minor redrafting and renumbering of clauses, but this is little more than a tidying-up exercise.
There is no doubting that the new standard is essential when designing machine guards, but the standard's limitations must be borne in mind. For example, sub-clause 4.1.1 lists a number of assumptions, including:
In reality, a worker who makes the unwise decision to try clearing a jam without stopping a machine could well also decide to stand on something or use an improvised tool to do so. The standard is also based on anthropometric data and therefore it states: 'Because safety distances depend on size, there will be some people of extreme dimensions who will be able to reach hazard zones even when the requirements of this International Standard are complied with.' It is therefore crucial that guards are designed in the light of a formal risk assessment as well as the data contained in the standard.
Following the publication of BS EN ISO 13857 in April 2008, Procter Machine Guarding revised its popular Safety Distance Calculator for establishing the required safety distances and heights of machine guards. To download a copy of the BS EN ISO 13857 Safety Distance Calculator, go to the Free Downloads section of the Procter Machine Guarding website.