Hi

In trying to balance the size of mesh guarding to prevent hand / arm access to conveyor movng parts and allowing fall-off from the conveyor to drop into a bin at the tail end, is there a methodology without going to the hideous expense of British Standards?

Basically, what would be the largest mesh size through which an adult would not get their hand to pass through. Please cite sources if any

Regards, David

Hi David

I can't remember how I got it by I once had a length of metal shaped to indicate acceptable distances from a dangerous part of machinery depending on the size of the gap between part of the body and the danger point.

According to the internet such a thing is called a Gotcha stick, though I don't think I have any reason for it being so named!

When I started off the British Standard had replaced been replaced with BS5304:1975 after it had been recognised that the previous standard wasn't adequately protecting those with slim arms and fingers e.g. women of Asian descent.

So the new BS 5304 standard had sets of tables setting out what minimum dimensions were needed for a guard depending on the size of any opening in the guard - in your scenario probably a tunnel guard.

The BS got replaced by EN ISO 13857 with similar tables and I think the one you are looking for has been reproduced at Machinery Guarding Openings & Safety Distances - Occupli

For the avoidance of doubt and any thought that I might be breaching the Rules of these Forums, this is NOT any sort of recommendation for Occupli which I had never heard of before tapping in a few word into Google!

That particular standard comes with quite a few caveats regarding its tables:

- establishes values for safety distances in both industrial and non-industrial environments to prevent machinery hazard zones from being reached. The safety distances are appropriate for protective structures.

- also provides for distances to impede free access by the lower limbs (see Annex B).

- covers people 14 years and older. In addition, for upper limbs only, it provides information for children older than 3 years where reaching through openings needs to be addressed.

- It is not practical to specify safety distances for all persons. Therefore, the values presented cover the 95th percentile of the population.

- is not intended to provide measures against reaching a hazard zone by climbing over (ISO 14120:2015).

- does not provide the required risk reduction for every hazard.

- clauses covering lower limbs apply on their own only when access by the upper limbs to the same hazard zone is not foreseeable according to the risk assessment.