Specialist fire detection.

[Tom Sutton]

We?ve just acquired new Laser (class 4) cutting cell with Calcium Hydroxide filtration system. As a matter of fact, the system does prove to produce fire from the cutting tables and history suggests that it?s also likely with the dust collector in the filter chamber. Hence, we would like to have some sort of smart fire detector that will sense and alarm or address the incident by stopping the process- and where applicable we can respond efficiently. With the process set-up suggesting that Laser will produce smoke and flame, but ?how much is too much? or could possibly be a danger is still yet to be understood/known.

I received the above question recently any idea's.

[John Webb]

I recall mention of the use of optical spark detection in the extract ducting in connection with cotton mills? Or was it shredding rags or something? Regarding the filtration system, detection would be needed after the filters; optical detection of smoke, perhaps? (It might be worth speaking with BRE Ltd., as the Burn Hall has a filtration system on its extract system which suffered a fire from spark carry-over a couple of years after I retired. They may have put some form of detection in thereafter to detect such fires.)

[Fishy]

DEASAR risk assessment required?

[Tom Sutton]

Please enlighten me Fishy.

[Fishy]

Sorry - DSEAR: http://www.hse.gov.uk/fireandexplosion/dsear.htm

Not sure what by-products this process produces but in some cases dusty atmospheres can come within the reg's.

[Tom Sutton]

Thanks Fishy I agree it may need a DSEAR risk assessment but how do you detect an accidental fire and shut the laser down, in the guidance, fire is one of the possible dangers, the others eyes,skin,limbs are discussed but not fire?

[kurnal]

Tom I think we will need more info on the materials being cut, the nature of any fumes, vapours, residues or dusts given off, how they are moved from the workplace, where and how they are stored, details of any ducting just to have a handle on this. The interface between the detection system and the laser is easy, the detection system can provide a volt free closed or open pair but remember if part of life safety provision the interface should be fully monitored for fault conditions

[Owen66]

Heat detection via thermal link in the extract duct downstream of the filter ?

Could be something like a sprinkler head using inert gas or electro thermal type

If the extract duct is seeing say 80C temperature then for sure something has gone adrift - that could be either cutting table fire or filter fire

Owen66

[JT]

Have you considered linear heat cables? Linked to the system as mentioned above.

[Tom Sutton]

Thanks Guys I thought heat detection, set above the operating temperature of the equipment would be an answer but my solution would have been old fashion technology.

I now know there is a solution to his problem and what he requires is a fire engineer to do a survey, to provide an effective system which would detect an unwanted fires, isolate the equipment and give a warning, all I need now is a company that can do the job.

[kurnal]

Thanks Guys I thought heat detection, set above the operating temperature of the equipment would be an answer but my solution would have been old fashion technology.

I now know there is a solution to his problem and what he requires is a fire engineer to do a survey, to provide an effective system which would detect an unwanted fires, isolate the equipment and give a warning, all I need now is a company that can do the job.

Thats exactly the right answer, Tom, there are too many unanswered questions to enable informed comment on the basis of the information given, including the rate of fire growth, risk of explosion, extent of containment, objectives for the system, interaction with  and need for any  suppression systems, other methods of controlling, containing or inhibiting  rate of fire spread. Heat detection may be too slow for some of these considerations, even some of the latest linear detection cables but a survey by a competent assessor, with consideration of potential DSEAR implications as well, would be the essential first step.

[David Rooney]

Thanks Guys I thought heat detection, set above the operating temperature of the equipment would be an answer but my solution would have been old fashion technology.

I now know there is a solution to his problem and what he requires is a fire engineer to do a survey, to provide an effective system which would detect an unwanted fires, isolate the equipment and give a warning, all I need now is a company that can do the job.

Everything you want to happen is pretty standard stuff ... but the question still remains what is the best form of detection ??

We do install a few weird things like conveyor belt fire detection and flame detection to stop belts and shut down plant / operate drenchers etc but what are they worried about catching fire.... the material they are cutting or the exhaust duct ??