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Guru
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Lower Explosive Limits

01/12/2007 11:07 AM

I need to find a piece of kit to measure the Lower Explosive Limit of the powder concentration in our powder coating booth. Can anyone point me in the right direction?

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Anonymous Poster
#1

Re: Lower Explosive Limits

01/12/2007 12:11 PM

Most gas detectors have a replaceable sensors. When you order the detector you have to specify the chemicals you are detecting.

There are continuous unmanned monitors and portable monitors.

Try these links

http://www.nordson.it/Businesses/Powder/Products/Accessories/Firedetand+supp.htm

http://www.powersourcing.com/se/detectionequipmentsupplies.htm

http://www.auburnsys.com/safe_ap.html

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Guru
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#2
In reply to #1

Re: Lower Explosive Limits

01/12/2007 6:03 PM

The questioner was asking about a much more serious hazard.... dust in the atmosphere...

If you don't think that's hazardous look at th engineering websites regarding hazardous environments, it s surprising just what dust particles can do in the right mixtures....

John.

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#3
In reply to #2

Re: Lower Explosive Limits

01/12/2007 10:50 PM

this search generates 50,000 hits one of which may be of use.

http://www.google.ca/search?hl=en&q=%22explosive+limits%22+%2Bdust&btnG=Google+Search

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Guru

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#4
In reply to #2

Re: Lower Explosive Limits

01/13/2007 2:54 AM

Yeah, just ask someone in charge of a grain storage operation. There have been huge explosions in grain elevators but I believe they now have pretty effective means of control.

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Anonymous Poster
#11
In reply to #2

Re: Lower Explosive Limits

01/16/2007 11:53 AM

Sorry for the confusion. but

The links above are for Dust detectors!

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Guru
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#5
In reply to #1

Re: Lower Explosive Limits

01/13/2007 8:36 AM

Dear Guest. The man is not talking about a gas, he is talking about a plastic powder. Powders of many materials when mixed with air are very explosive in the right concentration. I have seen many explosions in flour silos, this why the flexable rubber hosing filling the silos have to be grounded by an earth cable. The reason for this is that the friction of dry flour as it rubs against the dry rubber hosing creates a build up of a large static charge and any resultant discharge or spark ignites the flour-air mixture, creating a huge explosion. I would have thought that a plastic powder would have the same effect.

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Anonymous Poster
#6

Re: Lower Explosive Limits

01/13/2007 12:29 PM

I suggest you start by discussing the issue with experts at Underwriters Laboratory. Determining the LEL for 'dusts in air' is not straight-forward. Some laboratory experimentation may be essential. If you are lucky, UL will already have the data you need and an accepted mathod of measurement and continuous monitoring. Particle size is a critical factor as is particle count and size distribution. Not all 'dusts' are explosive or even combustible.

Until you get this sorted out, I strongly suggest you take precautions by ensuring everything is electrically grounded--the sprayer, sprayer tip, so far as possible. With the inherent high voltage potential between the paint particle and object being coated, it may not be possible to prevent spark discharge as a source of ignition. Then particle size, size distribution, and concentration are the variables that must be controlled to avoid any dangerous situation.

Several years ago, a large computer disk manufacturing facility (over 200' x100') located 100' away was destroyed by a 'dust explosion' from less than 1 # of aluminum 'dust' on a loading platform that was ignited by a welding torch during repairs to the platform metal edge.

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Guru
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#7
In reply to #6

Re: Lower Explosive Limits

01/16/2007 3:48 AM

Just a clarification, I know what the LEL and UEL of the materials are, I just need to measure the concentrations we have in our booth. I can get any number of devices to measure gas concentrations in air, but not, it appears, dust or particle concentrations in air.

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#8
In reply to #7

Re: Lower Explosive Limits

01/16/2007 8:17 AM

Plbmak, if you can't find anything suitable let me know... I'm sure I can come up with something ....

I would have thought using light scattering techniques or maybe a sampling technique would do the job nicely...

Depends on whether you are wanting a fast reponse or not...

John.

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Guru
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#9
In reply to #8

Re: Lower Explosive Limits

01/16/2007 8:23 AM

Cheers mate, I can work it out mathamatically, but I'd rather take at least one series of samples.

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#10
In reply to #9

Re: Lower Explosive Limits

01/16/2007 11:21 AM

Ooowww look at what I've just found.... this email flooded into my inbox just now from..... Globelspec!!

Test Particle Size for Powder Safety

Discovering a new use for an old routine is exciting. It seems particle size is one important criterion for ascertaining the flammability of certain materials.

Through rapid and accurate particle size analysis, whether in liquid or solid suspension, the Malvern Mastersizer 2000 is a unique way to test for powder safety.

Any use Plbmak?? John.

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Guru
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#12
In reply to #10

Re: Lower Explosive Limits

01/17/2007 2:43 AM

Cheers mate, that looks good, I'll check it out.

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