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#1 Posted : 11 September 2000 11:15:00(UTC)
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Posted By Ciaran McAleenan
Dear All

I am trying to establish the probability of the following scenario;

"Worker inspecting a manhole chamber from the outside shines a torch into the opening to illuminate the chamber. The torch is not explosion proof."

Are there any documented cases where a spark from the torch has come into contact with a flammable atmosphere and caused an explosion.

Obviously the following must combine;

1. The atmosphere must be flammable,
2. The torch must spark when switched on,
3. The two must come into contact.

It has been put to me that providing the torch is switched on and off outside the confined space that there is no risk of a spark.

Any thoughts on that?
Any documented case studies?

Ciaran

P.S The closest I have come to this scenario was documented by US NIOSH as follows;

"The victim entered a tank to spray paint. He was wearing a supplied air respirator (without an auxiliary escape Self Contained Breathing Apparatus (SCBA), welder's cap, coveralls, rubber gloves, and steel toe boots. To provide lighting for the victim, the co-worker positioned a 500-watt, non-explosion-proof halogen lamp over the manway opening. The co-worker then set on top of the tank next to the manway to observe the victim. He (the co-worker) was wearing a dust/mist respirator. Using an airless spray gun, the victim began spray painting the inside of the tank with an epoxy-base paint. The victim had completed painting the bottom and sides of the tank, and he was painting the top when the spray gun nozzel hit the lamp, breaking the sealed beam. This ignited the epoxy vapor which caused a flash fire explosion."

Note: The worker died and his co-worker was badly injured.
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#2 Posted : 11 September 2000 11:47:00(UTC)
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Posted By John Webster
I think you have made the point yourself.
The hazardous area must be properly defined. In oil and gas installations, a radius beyond the potential source of flammable gas is specified (I think it is 70ft, but would need to check - David Shearer are you there?)
Within this zone, potential sources of ignition, including non explosion-proof electrical equipment, can only be used under hot-work permit conditions.
In the case of the torch (flashlight for our overseas readers), the obvious spark risk is when the torch is switched OFF, not ON (anyone smelling gas please note). But the risk of somebody dropping the torch, or of it developing a fault - eg. loose connection - causing internal sparking must be considered very high. How often have you seen somebody banging a torch to make it work?
Hope this helps
John
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#3 Posted : 11 September 2000 12:38:00(UTC)
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Posted By Ciaran McAleenan
Thanks John

Your response does help. Also I have just found some useful information from NIOSH entitled;

"Exploding Flashlights: Are they a Serious Threat to Worker Safety". Its available at

http://www.cdc.gov/niosh/fact0002.html

Ciaran
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#4 Posted : 11 September 2000 13:54:00(UTC)
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Posted By peter gotch
Dear Ciaran,

You can get Zone 1 torches. What you can't get is a compact Zone 1 camera (as opposed to flameproof CCTV).

Our engineers and surveyors have the problem of needing to get a photographic record of defects in various confined spaces structures.

Following discussions with HSE etc, we concluded that there is no history of incidents during such work, and that the risk was very very low.

We developed a safe system of work wherein monitoring of the atmosphere in the immediate vicinity of where the camera would be operated would be undertaken immediately before a picture is taken.

Regards, Peter.

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#5 Posted : 11 September 2000 22:03:00(UTC)
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Posted By Stuart Nagle
This question is not so much one of why do I need an intrinsically safe torch, as one of what may happen without the use of such equipment.

The Confined Spaces Regulations state that electrical equipment used ‘in confined space working’ should be intrinsically safe. It does not state that this only applies to areas within the actual space.
Obviously, there is a potential risk that gases, fumes or vapours escaping or venting from the space may ignite or explode, if they are in contact with a source of ignition. This could include turning a non-intrinsically safe torch on or off outside the space.

As we know, many gases, methane included, are lighter than air and will rise if given the opportunity, Other gases, such as Hydrogen Sulphide, whilst generally considered a toxic gas, is flammable/explosive at sufficient concentrations. Whilst Hydrogen Sulphide is heavier than air and normally will seek the lowest area of a space, there are records where the gas, when heated, and as all gases will do, expanded and escaped out from an open manhole (within a concrete open topped waterway) killing employees who where outside the identified confined space.

Whilst this was not due to fire or explosion, it demonstrates graphically the potential for harm in such circumstances. This is true for most gases and obviously, those that offer the risk of fire or explosion, may be ignited where an unprotected source is used such as non-intrinsically safe equipment.

Further to the above, in respect of other legislation such as PUWER and HSAWA and MHSWR, the employer has a legal duty to ensure, so far as is reasonably practicable, that safe systems of work, and the correct suitably tested and calibrated tools and equipment are used. The employer must train his employees and provide instruction and supervision.

In this case, as the work is confined spaces working, I believe the argument that an intrinsically safe torch was not necessary, would not stand up to the test of these legal duties in the event of an incident. Clearly, those involved are aware of the risks and are not doing everything, so far as is reasonably practicable, to ensure the risks are adequately controlled.

Where there is a reasonably foreseeable potential danger involved, and it is reasonably practicable to provide simple and inexpensive equipment, e.g. an intrinsically safe torch(s), to guard against the risks posed, this must be done. This is what the term ‘reasonably practicable’ defines.

As a further example of the potential risks, one may also quote Regina – V – Associated Octel. In this instance a non-intrinsically safe lighting source, namely a lead-light within a protective cage, was smashed within a chemical storage tank undergoing repair and maintenance. Whilst the space was inert prior to the works, the substances introduced to the space gave off flammable vapours that were ignited by the breaking light-bulb with almost fatal effect, and seriously injuring the occupant of the space.

Whilst this incident was within a space, the potential for an ignition source to ignite the atmosphere immediately adjacent to the opening of the space is obvious. Is a person using a torch that is not intrinsically safe going to remember that switching it off, as well as on, could kill, and leave the vicinity of the space before doing so?

Where confined space work is undertaken, all sources of ignition should be excluded. This also includes smoking within the vicinity of open access and egress points of confined spaces, as well as those sources that may give rise to a static discharge, such as water jetting etc. These rules have not been established to be tested by persons trying to avoid compliance, they have been put in place so that employers can ‘ensure’ ‘so far as reasonably practicable’, that all actions to safeguard the health, safety and welfare or employees and others who may be affected by their actions or within their undertaking are carried out.

To ignore such simple rules is not only dangerous, but could lead to prosecution, fines and/or imprisonment, and of course death.... It is worth it !!

Hope this helps your argument Ciaran.

Regards...

Stuart Nagle
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#6 Posted : 12 September 2000 00:31:00(UTC)
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Posted By Edward
From what I remember to be intrinsically safe a torch has to:

a]Exclude vapour from any source of ignition arising out of the normal operation of the controls [ sparks from switching on/off ]

b] Exclude vapour from any surface above a certain temp. [ halogen bulbs run hot enough to ignite some vapours ]

c] Exclude vapour from any source of ignition as the result of a foreseeable failure of any part [ a bulb burning out is electrically the same as switching the torch off except that the risk of sparking is less controlled ]

The standards for intrinsically safe come from a long sad history of shortcuts don't chance it!
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#7 Posted : 13 September 2000 19:50:00(UTC)
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Posted By Stuart Nagle
PS

For those wishing to establish what equipment is 'intrinsically safe' the BASEFFA List carried details of all equipment currently approved to the Standard.

BASEEFA = British Approvals Service for Elecrtical Equipment used in Flammable Atmospheres (Price last time £70.00)

Stuart Nagle
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#8 Posted : 14 September 2000 00:48:00(UTC)
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Posted By Philip McAleenan
Ciaran,

reading between the lines of your inquiry, it appears to be about the principal of "foreseeability" , e.g. if it has happened before, it can happen again, but with a very particular focus on torches (flashlights). Whilst the principals of risk assessment require employers to consider the wider experience in their or similar industries, it would be taking the matter too literal to seek identical scenarios before deciding that there is a risk.

The hazard to be considered here in the first instance is flammable atmospheres, not torches. Risk analysis looks at the universal situation of flammable atmospheres in contact with electricity from whatever source. Electricity is a source of ignition and therefore must be isolated from the atmosphere. To assess the particular e.g. torches and find no specific incident relating to that particular causing an explosion is to ignore the very real possibility that the next time will be it.

The principal of foreseeability uses past history as a guide to what will happen if experience is ignored. But it is also based on our ability to apply past experience to different circumstances so that we can make a judgement about the probability of something happening, even though that something may not have happened before.

In your scenario the hazard is the atmosphere. The principal requires, amongst other things, that no source of ignition be introduced. Any electrical equipment, (not just torches) that are necessary for the inspection must ensure no possibility, however remote, of sparking.

Philip
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#9 Posted : 14 September 2000 09:20:00(UTC)
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Posted By Stuart Nagle
Philip

I thought I said this, already !!

Stuart
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#10 Posted : 15 September 2000 11:53:00(UTC)
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Posted By Ciaran McAleenan
Thanks you all.

Your responses have been very helpful.

Regards

Ciaran
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