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FIRE SERVICE AND GENERAL FIRE SAFETY TOPICS => Fire Safety => Topic started by: 2010regs on February 28, 2012, 02:24:45 PM
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Hello All
Just been discussing this topic and i have been informed that some foam extinguishers are safe to use on electrical equipment. If this is the case i must have had a brain storm as i was sure that it was a definite No no. can anyone point me to the information that confirms or disproves this.
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Some are tested and safe for use in the vicinity of electrical equipment and carry the electrical graphic symbol along with the class A and B graphics on the label
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Standard advice is foam fire extinguisher shouldn’t be used on electrical fires. However, most foam extinguishers have passed the 35kv conductivity test,indicating the extinguisher user has added operator safety if it were to be unintentionally used on electrical risks. The extinguisher user may still on the other hand obtain an electric shock if positioned in a residual puddle if the live electrical equipment did not short circuit, which is why foam fire extinguishers are not deemed as suitable for electrical fires.
This is backed up by BS 5306 pt 8 2000 section five which says.
Water and foam extinguishers that meet the requirements of the dielectric test of BS EN 3-2 should nor be installed for direct use on live electrical equipment except after specific consultation with the manufacturer of the extinguishers, the manufacturer of the electrical equipment and the fire authority.
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Foam has water added and water and electrics don't mix very well even in small amounts. Why would anyone take the litigation risk?
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Whilst all the above is correct it should be noted that three Manufacturers, Britannia Fire, TOTAL & Execelsius have put the UK 'Electrically safe' symbol on water and foam spray extinguishers (all of which have BEN3 Kite-marks and in some cases 'ships wheel' approval)
In Europe, where this symbol isn't used it is not uncommon to see foam spray extinguishers marked as 'suitable for fires in electrical equipment up to 1000V'
British Rail in the early 90's installed AFFF spray in place of Halon and water, including locations where direct electrical use was likely, CO2 being reserved for high voltage installations in buildings and the original marking on Thomas Glover AFFF and Britannia Triclass (both pioneers in the use of AFFF Spray) indicated suitability for direct electrical use.
Therefore it isn't technically correct to say you must not use water spray, water mist or foam spray extinguishers on electrical equipment (after all they don't have to have the 'do not use on' warning), but I would think very carefully before saying it is suitable in a risk assessment - the BR example was in an organisation with a lot of training & fire safety management frameworks in place so staff could use AFFF on electrical equipment more readily as they would be aware of the residual hazards from pooling, etc
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thanks anthony. i must admit i always thought that those extinguishers shouldnt be used specifically to tackle electrical fire but just gave some protection incase the user accidentally hit electrics. one question though why is there a 1000 volt limitation specified?
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It is my understanding that the AFFF extinguishers are safe for accidental contact on to live electrics up to 35kv but not to be used directly on live electrical equipment.
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Thank you all for your excellent advice,as usual with all things fire safety it's never just yes or no is it ;)
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That depends
:)
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Thank you all for your excellent advice,as usual with all things fire safety it's never just yes or no is it ;)
No prob.
Can you send your address for the invoices please. Failure to pay will result in you being turned upside down and whatever hits the deck going into the Banter Bar Big Barsteward's Free Xmas drinks all around tin. Washers and all. ;)
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It is my understanding that the AFFF extinguishers are safe for accidental contact on to live electrics up to 35kv but not to be used directly on live electrical equipment.
I would agree that for roughly 25 years of the 32ish years of existence of the non aspirated foam extinguisher the convention (for most) was as you say, but in the last few years we have gone full circle and several people are saying direct use is OK again.
The 1000V limit in mainland Europe also states the minimum distance from the fire must be 1m.
In 1963 the JOINT FIRE RESEARCH ORGANIZATION did tests on extinguishing electrical fires and also referenced Nu Swifts studies on the same (Nu Swift said their water extinguishers were safe up to 400V unless fitted with a wetting agent charge or anti freeze) and concluded the risk from a plain water jet was very low as close as one foot and virtually nil with sprays, exceptions being soda acid, loaded stream and antifreeze models
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We used to put a 1 inch jet onto a 35kv grid at Moreton but I wouldn't recommend it for Joe public, my rule would be isolate the supply then use the extinguisher. For advice I would stick to the BS just in case things go pear shaped, there is an exception if required.
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I'd agree with that & in general do not accept them for direct use in the typical premises we deal with.
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We used to put a 1 inch jet onto a 35kv grid at Moreton but I wouldn't recommend it for Joe public, my rule would be isolate the supply then use the extinguisher. For advice I would stick to the BS just in case things go pear shaped, there is an exception if required.
Be interesting to know if they still do that Tom. It was on the 6 week JO course if I recall. Those were the days. That drill was enough to make your hair stand on end and as for the bugs......
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We used to put a 1 inch jet onto a 35kv grid at Moreton but I wouldn't recommend it for Joe public, my rule would be isolate the supply then use the extinguisher. For advice I would stick to the BS just in case things go pear shaped, there is an exception if required.
Be interesting to know if they still do that Tom. It was on the 6 week JO course if I recall. Those were the days. That drill was enough to make your hair stand on end and as for the bugs......
The Bugs? That made your hair stand on end also.
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The training may have changed but I bet the bugs is the same as ever.
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The Bugs? That made your hair stand on end also.
He hasnt got any hair apparently but plenty of bugs
Anthony B you are singing my tune. Based on my earlier comments who measures the acceptable voltage that these things can be used on. Take it that is the BS committees but why select that particular voltage?
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Just to clarify EN 3-7 allows Water-based extinguishers to be marked as being suitable for use on live electrical equipment up to 1 000 V a.c. at a distance of 1 m, but The British Standards Technical Committee FSH/2 have stated that the national practice is ”not marking the extinguisher if it passes the test
in BS EN 3-7:2004+A1:2007, Annex C, but marking a warning if the extinguisher failed the test or was not submitted”
It's therefore only UK traditions that mean water based extinguishers are not normally marked for electrical fires - a tradition that the new draft BS5306-8 for the selection & placing of extinguishers will continue (unless there is an overwhelming response to the draft to take up the mainland European approach)
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The draft for part 8 is out for comment in some quarters.
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Yes, some big changes afoot to if it goes through.