Fire in the hole

[BobL]

Extracted from the WA Design Tech E-journal (July 2017)
Sorry its not too clear - its the best I could do.

I suspect the the risk could have been reduced by using 6" ducting right up to the machine..



417702

[ian]

do you have a copy of the implemented "remedial" measures?

[BobL]

yes

[BobL]

http://i8.createsend1.com/ei/j/16/9F4/8ED/csimport/FireinWWEquip1.194606.jpg






Recommendations
• All operators are instructed to avoid (as far as practicable) the entry of large debris into the dust extraction system and to take immediate action to clear debris if it does enter the system.
• Ensure regular maintenance and cleaning is undertaken. Follow the isolation procedure.
• Cleaning should be performed using a brush and vacuum cleaner, rather than using compressed air. Never use bare hands.
• Ensure dust masks and safety glasses are used where appropriate.
• Regularly check to ensure dust extraction system is operating effectively.
• Ensure blade is appropriate for the cutting task, sharp and correctly adjusted as per manufacturer’s instructions.
• Check timber stock for nails and avoid cutting damp glued wood.
• Do not operate any equipment without all guards in place (combination machines have multiple guards).
• Ensure fire extinguishers of the correct type are readily available & positioned near exits.
• If a fire does occur, ensure dust extraction and power is turned off and isolated.
• If a fire is suppressed using an extinguisher, ensure it is completely extinguished and not left smouldering.

[woodPixel]

Bloody OH&S is the direct cause of this... Some bureaucrat didn't include "check for buildup" in their one-a-decade tick sheet procedure on page 367.

Or the mung-beans users ignored the billowing dust and incredible stink.... Seriously, this would have stunk to high heaven for ages before it occurred.

If the idiots using the machine were physically and financially responsible for it, it would have been averted.

Instead, the responsibility was passed off to a committee, who can now hold a dozen meetings to validate their existence and add in page 368.

Makes me wonder BobL, do DC rooms have smoke detectors in them? Bit tricky isn't it!

[Fuzzie]

Every time I use the table saw at the mens shed I wonder why it doesn't seem to be cutting smoothly. I also see people forcing work into the blade because it's not sliding through smoothly. I just wonder about their thought process, why not check the machine if its not performing properly instead of pushing on regardless?

Last time I used the saw to rip I couldn't work out why the blade was stalling. I checked the fence alignment, I checked a thin kerf blade wasn't on with the thick splitter. I then took the skins off the cabinet and a found a number of thin strips jambed in the dust shroud pushing against the blade. :shrug:

[ian]

Why am I not surprised by this bit











Recommendations
• All operators are instructed to avoid (as far as practicable) the entry of large debris into the dust extraction system and to take immediate action to clear debris if it does enter the system.







so in effect operators are "instructed" to remove "large debris" -- however that is defined -- from beside the blade before the off-cut falls through the gap between the blade and table.

I can see it now, the next safety alert will be because an "operator" has lost a finger or two (or worse) removing the "debris" partway through a cutting task.

It would have been far better to require a check for (and clearance of) debris build up before and after each "shift".

[MandJ]

I know it's not particle in a lot of situations for various reasons, but a $15 adjustable vacuum sensor tripping the NVR may? also stop this, I wouldn't be without mine on both the BS and RT, stopped me getting a puff of dust in the face on many occasions like: another blast gate open or even half open, dirty filter bags from to much sanding, wrong blast gate open, seniors moments. Like everyone? I have a fire extinguisher in the shed.

[BobL]

Institutional gear is often treated like this and it doesn't surprise me. I suggested a system at the mens shed that made a pair of members responsible for an individual machine but this got deemed too complicated. As a result general machine maintenance in the wood work area is patchy. The metal work area is much better with several individuals taking it upon themselves to be responsible for servicing various machines

The other day, one of the techo's where I used to work told me about two research students he found in the Department workshop cutting a slot in a brick with a carbide cutter using a Swedish precision mill. There was grit everywhere and they were straining the machine t the point of breaking something.

RE: Fire in the hole incident
The really stupid thing is they probably have a 20HP DC but are extracting dust from their machines with 4" ducting and the throttled dust ports. You can tell that from the melted piece of 4" flexy shown in the last picture.

If they had 6" extraction it would pick up most of the larger debris that causes choking.

The other contributor to the problem is the use of non-zero clearance throat plates.
A simple way to significantly reduce the amount of large debris that gets into dust extraction is to use zero clearance plates at standard and only switch to non-zero when needed. Because of this there is never ANY build up of large debris inside my TS cabinet.

RE: Makes me wonder BobL, do DC rooms have smoke detectors in them? Bit tricky isn't it!
By rooms I assume you mean enclosures?
This would a very smart place to place a smoke detector BUT they are affected by fine wood dust so the detector would need to be be able to discriminate between the two.
Given that enclosures get warm and extraction of dust warms the air a temperature based fire detector may be too slow.
Particle counters that can discriminate on particle size may be a better option.
Sounds like it could be another project for me to look at.

Talking about fires, and and particle and smoke detectors. in a very large ultra clean labs we set up at work we installed a super sensitive $50k particle detection system and a standard set of smoke detectors as per building code. There were about dozen particle particle detectors feeding back to a central PC which was on line and also sent out an SMS to staff when the particle counts went above a certain level.

The labs were built in such a way that when no one was working inside them the particle counters showed zero counts/m^3. With one person inside the labs, amount of dust registered was zero except for the detectors near where the person was working because the dust capture at source kept the human dust from migrating elsewhere in the facility. Around the lab user (attired in approbate lab wear) the dust ranged from 100 to 300 "particles of 0.3 microns and greater per cubic meter" (CF, Hospital operating theatre grade air [with no people inside] is 3500 particles per cubic meter).

Someone entering the ultra clean labs in street wear would push the particle counts to over 1500/m^3 in their immediate vicinity but it was still zero everywhere else in the labs. The system was set up so a tradie could enter the facility and perform work and the labs would recover in quick time (~20 minutes). If we had to shut down the lab for a few days the would recover in about 24 hours.

All particle count data was logged - the counts were always zero or near zero so when something showed up it was clear something was happening. The system could detect lab users entering, working and leaving the various labs and matching that data to entry logs we could tell who were the clean and dirty operators.

One professor was constantly showing up as creating dust inside the air lock to the labs when he was leaving so changing back out of lab coat, snood (cap) and lab shoes into street wear. Eventually we found out he was combing his hair after taking off his snood and the particle counter in the air lockwas literally about half a metre from his head.

Another time the particle counters picked up a steadily increasing amount of dust in one of the cold (-18ºC) clean rooms used to study polar ice. On investigation we found a smouldering freezer door seal. The doors have Viton rubber seals but to keep the seals from freezing and shrinking and losing sealing capability they have low wattage heater wires running down the inside that keeps them pliable. A heater wire had shorted and over heated rubber - it was not that hot, it had just started to started to crumble. The fix was easy, turn of the seal heater powersupply and rip/cut the seal out (it was siliconed in place) and put it into a plastic bag and remove from the lab)

The particle counters picked the smoke up immediately and because normal dust levels were always near zero we knew something was not right. It took another 20 minutes for the smoke detectors to pick up the smoke and that of course called the fire brigade and we had to do some fast talking to stop them from stomping through the facility. We took a suitably dressed firefighter into the facility to show them what was what, and the firie said it was the first time he had entered a fire scene in clean room gear. Some of this problem was because the air handling system was so efficient at removing dust/smoke at source, and one outcome of this event was doubling the number of smoke detectors in the facility.

I could go on and on about stories about this lab but that is enough.

[Lappa]

http://i8.createsend1.com/ei/j/16/9F4/8ED/csimport/FireinWWEquip1.194606.jpg






Recommendations
• All operators are instructed to avoid (as far as practicable) the entry of large debris into the dust extraction system and to take immediate action to clear debris if it does enter the system.
• Ensure regular maintenance and cleaning is undertaken. Follow the isolation procedure.
• Cleaning should be performed using a brush and vacuum cleaner, rather than using compressed air. Never use bare hands.
• Ensure dust masks and safety glasses are used where appropriate.
• Regularly check to ensure dust extraction system is operating effectively.
• Ensure blade is appropriate for the cutting task, sharp and correctly adjusted as per manufacturer’s instructions.
• Check timber stock for nails and avoid cutting damp glued wood.
• Do not operate any equipment without all guards in place (combination machines have multiple guards).
• Ensure fire extinguishers of the correct type are readily available & positioned near exits.
• If a fire does occur, ensure dust extraction and power is turned off and isolated.
• If a fire is suppressed using an extinguisher, ensure it is completely extinguished and not left smouldering.








Hmmm?

[Bohdan]

Every time I use the table saw at the mens shed I wonder why it doesn't seem to be cutting smoothly. I also see people forcing work into the blade because it's not sliding through smoothly. I just wonder about their thought process, why not check the machine if its not performing properly instead of pushing on regardless?



Some people just don't recognise that there is a problem and push on regardless.

I had a worker replace a blade in a panel saw in the morning, at the coffee break he commented that the new saw blade was not much good as he had to push real hard. We checked the saw and the blade was on backwards. He had just spent 2 hours forcing 3/4" chipboard thru the machine without bothering to check or complain. :o

The cut quality that he achieved with the blade backwards was surprisingly very good.

[BobL]

I know it's not particle in a lot of situations for various reasons, but a $15 adjustable vacuum sensor tripping the NVR may? also stop this, I wouldn't be without mine on both the BS and RT, stopped me getting a puff of dust in the face on many occasions like: another blast gate open or even half open, dirty filter bags from to much sanding, wrong blast gate open, seniors moments. Like everyone? I have a fire extinguisher in the shed.

I have been thinking about this for a while, especially for the mens shed where members are constantly forgetting to open the blast gates.

As far as DIYers are concerned I realise that (rightfully) few DIY'ers are up for modifying their machine switches to install such a sensor especially in an industrial type electromagnetic contactor is involved.

As an alternative to modifying machinery how about a short extension cord or box that places a simple relay (also connected to the sensor inside the cabinet) in between the GPO and the machines power plug?

Something like this?
417718
I might make a bit of a prototype and see how it goes.

[QC Inspector]

Backwards blade mounting isn't just on stationary saws. I had the guys that hung the drywall in the house put the OSB on the shop ceiling rather than struggling with it by myself. I showed up near the end and watched one of the guys cut a sheet with his circular saw. When the blade stopped turning I said the blade was in backwards. His boss said the arrow on the blade pointed forward. I pointed out that that was true for normal saws with the blade to the right but this saw had the blade on the left side. The reason it cut somewhat was the chip limiters behind the teeth were doing the work.

Bob and other electonical fiddlers. :) As far ask know some of the fire suppression systems used in commercial ducts use optical detectors that see sparks to activate the fire suppression downstream. Are there inexpensive optical sensors available that could be made to open a water spray in a cyclone's collection bin for sparks that get in there? The optical sensor being mounted in the ducts just before the cyclone inlet.

[Kuffy]

I'll fess up. I have put a blade on backwards on a panelsaw and attempted to make a cut, which just happened to be a 130mm high rip cut 4.5meters long. I made it all of 5mm before I stopped due to the Bzzzzzz sound of the cutting action rather than the normal sound which I can't think of a way to describe in text.

I've also put a cutter head on backwards in a 5 head moulder. OH MY GOD the noise that comes out of that machine with a backwards head is insane. It truly provokes the instant emergency stop SMASH! I thought I had one of the spring loaded side pressure plates shift back onto the cutterhead, because naturally I don't assume I would be silly enough to put a head on backwards :doh:

Those two examples I can't for the life me think of a way that the operator couldn't notice it after attempting first cut/pass.

Bandsaw blades on backwards I could understand if you are inexperienced because it still does everything it should without changing the common noises much, but it does cut much much much slower. it's like watching paint dry :D

I do wonder about the cause of the fire in the OP. I did a similar thing last year or the year before because I had cut through some steel screws which tossed a bunch of sparks which had then started to smolder the small pile of dust in the under table saw enclosure. The dust shroud would have had to be jam packed full of dust, and when that happens (yes I know what happens from experience...:doh:), the saw constantly spits up dust while it isn't cutting anything. You can place your hand over where the dust is coming out and it feels like you are being peppered with bullets.

[BobL]

Bob and other electonical fiddlers. :) As far ask know some of the fire suppression systems used in commercial ducts use optical detectors that see sparks to activate the fire suppression downstream. Are there inexpensive optical sensors available that could be made to open a water spray in a cyclone's collection bin for sparks that get in there? The optical sensor being mounted in the ducts just before the cyclone inlet.

Unfortunately most DC and DC related fires don't start from sparks but something hot that gets into the collection bags. The sawdust then tends to smoulder until it catches. Although it would be better than nothing by the time there is something glowing visible like sparks the fire will be well advanced and ideally you want to catch it earlier that this. Optical methods can be interfered with by the sawdust as all tend to register as signals by a smoke detector. IR detectors may also be interfered with by warm/hot dust.

[BobL]

I decided to follow up on M&Js pressure sensor idea.

4 of my WW machines (DP, BeltS, Lathe and BandS) are on VFDs so wiring a pressure sensor in line with the the remote switches (which are only 10V) is going to be a doddle.

I already have one of these low pressure sensors on my forge and I just checked I paid US$14 for it in 2013.
Just checked eBay/Banggood/Aliexpress, and see that a budget versions that would be suitable are available for ~$4

The blurb says the switch is only rated for 125V - i.e. appealing to north american market.
BUT
Magnifying the microswitch up from one of the supplied photos says the microswitch is rated to 2.5A @ 250V
417781

I have ordered one and will test it out.

It could be used direct for machines up to ~3/4HP.
Above that you'd still need to use a relay, but relays are not expensive so even in a rated enclosure the whole switch should only cost about $25.

[richmond68]

Extracted from the WA Design Tech E-journal (July 2017)
Sorry its not too clear - its the best I could do.
I suspect the the risk could have been reduced by using 6" ducting right up to the machine.
To the best of my knowledge the casadei c30 and c41 are rebadged minimax, from what I've seen online they appear identical. I've outlined the problems that exist with my C300 before - http://www.woodworkforums.com/f200/minimax-token-dust-collection-fix-207209-post1965416#post1965416 - I suspect that the Casadei of similar age may suffer the same flaws. That a fire could occur in the blade shroud and flexible duct below the table comes as no surprise to me.

Addressing those fundamental design flaws is needed, 6 inch ducting to the machine won't fix a blade shroud lucky to flow 80cfm. That burnt piece of duct is from inside the machine, it is 120mm and runs from the shroud to the port on the rear of the machine. It's garbage, probably costs a quarter of the flow itself.

[safari]

Ensure fire extinguishers of the correct type

Could someone please advise what the correct size and type of extinguishers should be in a wood shop/

Thanks

[BobL]

Ensure fire extinguishers of the correct type

Could someone please advise what the correct size and type of extinguishers should be in a wood shop/

Thanks

workplace or DIY?
For a Workplace you should get a professional assessment done.
For DIY wood work shops an ABE type is usually sufficient.
Size wise you should be looking at around a 1kg for a single car garage and increase the size accordingly.
I have a 1kg ABE next to the back door and a 2kg and a fire blanket next to the front door

I also have a CO2 specifically for electrical fires. Letting off an ABE will fill your shed with powder and may damage electrical devices like VFDs on machines that are not on fire.

[safari]

Thanks for your reply BobL