Posted By Pat Hannaway
Hi Gary,
we looked into this some time ago. Short answer is no. There are numerous compressed air drills but the main problem is that whatever the drill (whether used for concrete or steel)will generate substantial amounts of heat will be generated, which may be sufficient to ignite any explosive gases present.
I would respectfully suggest that the area to be drilled is purged of any explosive atmospheres prior to drilling and if possible replaced with "normal" air.

Posted By Eric Taylor
Try some of the manufacturers and see if they do Beryllium Bronze tooling for the drills. Guarenteed no sparks but there is a risk from metal dust from the tools.

A water feed to the tooling may be another solution, either a trickle or mist would extinguish most sparks.

Posted By Mark Gough
the power requirements for a system to be certified as intrinsically safe precludes the use as a power tool also enhanced safety such as for lights would not easily transfer to power tools. Other than pneumatic tools have you considered designating areas for drilling under a permit to work scheme ?i.e checking for gas while the work continues under controlled conditions. Obviously this would not be acceptable for routine work but is used in mines, refinaries etc in designated situations.

Posted By John Murgatroyd
Since the air tools are supposed to be used with silencing attached, we can assume that isn't a problem.
Since you insist on the drill itself being I/S, we can assume that sparks are the problem.
Since the drill bit will easily get to a temperature that will ignite flammable atmospheres, I fail to see what you do want ?

Posted By Gary L
I apologise if I’ve caused some confusion by using the term “intrinsically safe”. I appreciate there are other approaches to making electrical equipment suitable for use in the presence of hazardous atmospheres such as increase safety “e” & Type N protection etc. etc.

I suppose I should have asked whether there are any drills, other than those that are compressed air driven, that are safe by design so they can be used in live sewers, ie Zone 1 hazardous atmospheres.

My problem is this, the compressors we use have noise levels between 94 & 98 decibels which make communication between the top man on the surface and the person working in the sewer difficult. Therefore we try to position the compressor as far away from the sewer entrance as possible (it also prevents exhaust fumes entering the sewer) The problem with having the compressor a long way from the entrance is that the compressed air hose now introduces a large trip hazard. The other problem we encounter with compressors is that some of the manholes are not in easily accessible places in the middle of the road; in some cases we have to cross fields etc and even though the compressor has wheels, it is still difficult to manoeuvre.

As previously stated, gas detection is completed before and continually throughout the man entry. Ventilation is either natural, mechanical, or both. The problem with sewers is that you don’t know what chemicals etc people upstream of your work area are throwing into their drains.

I appreciate a number of you have mentioned the heat from the drill bit, but that is another issue for me.

Once again, sorry for any confusion.

Gary