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Mersey  
#1 Posted : 12 July 2018 07:17:29(UTC)
Rank: Forum user
Mersey

I visited a pallet manufacturing company yesterday, they cut timber to size and make a variety of bespoke sized pallets. The housekeeping (when it comes to dust fines) is poor and when they attempt to brush up creates more breathable dusts so I suggested to them to purchase a vacuum cleaner / hepa filter etc...

Due to DSEAR and Fire risks they quite simply need to stay on top of the dust spillages / they already have LEV but when emptying the LEV this creates a real mess.

What I'm unsure is whether the vacuum need to be ATEX rated? The difference in cost between a normal vacuum cleaner and an ATEX one is astronomincal.

Trying to find infomation about ignition energy for wood dust. Wood dust is such a generic term though, what type of wood ? The moisture content is variable etc...

Using a standard hepa filtered vacuum cleaner - ignition sources static discharge only would this be powerful enough to ignite a dust cloud? Electrical arcing from shoddy electrical connection? 

I have seen standard HENRY's vacuuming up wood dust before but the murky world of DSEAR and ATEX rated kit has raised its head and has planted the seed of doubt

I was quoted £1750 for an industrial atex rated vacuum cleaner. The site will not shell out that amount of money if its not necessary, hence the enquiry

Elfin Davy 09  
#2 Posted : 12 July 2018 08:11:08(UTC)
Rank: Super forum user
Elfin Davy 09

As wood dust (along with many other dusts) is combustible, I assume a DSEAR assessment has already been undertaken ?  If so, the airborne concentrations associated with these tasks should be known, and that should determine whether or not an ATEX rated vacuum cleaner is required.

However, from what you've said already (ie that the housekeeping for dust fines is poor, dry brushing takes place and "making a mess when emptying LEV" leads me to believe it would be a good idea.

Maybe suggest to them that they consider the cost of an ATEX rated vacuum against the potential total loss of the building (and possibly lives) if they choose to buy a Henry and it DOES ignite a dust cloud ?

There again, their luck might just continue to hold...

thanks 1 user thanked Elfin Davy 09 for this useful post.
Mersey on 12/07/2018(UTC)
Mersey  
#3 Posted : 12 July 2018 08:17:04(UTC)
Rank: Forum user
Mersey

There are no explosive atmosphere in the workshop and never likely to be either.

 

I am just confused as to whether vacuuming wood dust up using a standard vacuum cleaner could create a explosive atmosphere within the vacuum cleaner, or maybe I’m over thinking this

 

Hsquared14  
#4 Posted : 12 July 2018 08:37:23(UTC)
Rank: Super forum user
Hsquared14

I don't think you can be sure that there won't be an explosive atmosphere in the workshop.  Check out the website below.

https://www.nilfisk.com/en-gb/products/Pages/Vacuum-cleaners/Industrial-vacuum-cleaners/group.aspx

Elfin Davy 09  
#5 Posted : 12 July 2018 10:00:18(UTC)
Rank: Super forum user
Elfin Davy 09

Mersey

You obviously have the advantage over us as you know the premises concerned, whereas we're simply generalising

However - and as HS14 has suggested above - I personally wouldn't take it for granted that there isn't an explosive atmosphere in the workshop (..unless testing has proven otherwise of course).

The HSE's take on wood dust (Reference: http://www.hse.gov.uk/pubns/wis32.pdf) is as follows: 

"You should assume that all wood waste is potentially explosive, unless a dust explosion test demonstrates it is not. Wood waste usually has a dust explosion risk where the mean particle size is less than 200 microns, and where as little as 10% of the mixture contains dust less than 80 microns in size. Only weak explosions are likely where the mean particle size exceeds 200 microns".

Worth another look to be sure perhaps ?

thanks 2 users thanked Elfin Davy 09 for this useful post.
Swygart25604 on 17/07/2018(UTC), A Kurdziel on 03/05/2019(UTC)
Mersey  
#6 Posted : 12 July 2018 10:25:00(UTC)
Rank: Forum user
Mersey

Thanks for the input.

There is LEV in the area which is subject to insurance inspections etc.. Within the enclosed area of the LEV system such as the flexible ducts /bag filters and manifold this would be a Zone 20 and the basis for safety is within the design of the LEV.

The only reason a dust cloud could occur is when the operators are changing the full dust bags from the LEV system and an open bag was accidentally knocked over, this creating a potential dust cloud.

Or if the LEV had a catastrophic failure/ ducts blew off and started pumping wood dust into the workshop etc.. ( inspected 6 monthly by a well-known insurance firm)

Under normal circumstances there can be no reason for an explosive atmosphere to exist within the workshop.

All I am trying to get me head around is whether we can vacuum up housekeeping to stay on top of  wood dust without using a ATEX rated vacuum cleaner. Loads of products on line for vacuuming up timber dust that are not ATEX rated.

I guess what I am confused with is the following;

Is it the product that you are vacuuming up (wood dust) that determines whether you need an ATEX vacuum, or is it the atmosphere that you are vacuuming in that dictates whether it is an atex rated vacuum.

 Thanks

Ian Bell2  
#7 Posted : 12 July 2018 13:02:11(UTC)
Rank: Super forum user
Ian Bell2

What is the particle size?

If the particles are 'chips' from sawing etc not as much as risk or is it dust from sanding etc?

Still a significant fire risk if chips though.

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Mersey on 12/07/2018(UTC)
Ian Bell2  
#8 Posted : 12 July 2018 13:06:29(UTC)
Rank: Super forum user
Ian Bell2

Some guidance here, if correct - 420microns & less than 33% moisture content

http://www.coastforest.org/wp-content/uploads/2013/12/dust_literature_review.pdf

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Mersey on 12/07/2018(UTC)
Ian Bell2  
#9 Posted : 12 July 2018 13:11:06(UTC)
Rank: Super forum user
Ian Bell2

Uk guidance http://www.hse.gov.uk/pubns/wis32.pdf

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Mersey on 12/07/2018(UTC)
paul.skyrme  
#10 Posted : 13 July 2018 17:51:13(UTC)
Rank: Super forum user
paul.skyrme

Firstly there should not be a problem with wood dust, if there is the LEV is inadequate, regardless of whether it is tested or not bye anyone.

Remember inadequate can also mean not used correctly.

There should never be a risk of explosion in a wood working workshop as the LEV should be adequate to control any dust, also the LEV is machinery under the SMSR, and thus must be designed, manufactured and installed such that it cannot pose an explosion hazard.

Absolute requirement from the EHSR's of the SMSR.

If you are collecting wood dust after spillages use the LEV system, get pick up points fitted smaller diameter flexible lines with blast gates that can be opened to allow the waste to be sucked into the LEV.

As far as the changing of bags goes, then that is a discipline thing and they shouldn't really be allowed into a scenario where they can be knocked over?

Do a Risk Assessment, bag being knocked over creating a dust cloud which can reach an ignition source which is present at that point in time, and has sufficient energy to ignite the dust could.  For a start EAWR pretty much requires compliance with BS 7671 which requires a 300mA RCD on pretty much all circuits in a woodworking facility.  Then there is the I&T and maintenance requirements of BS 7671, PUWER & EAWR to consider.

What is the likelihood of occurrence in the workshop?

If you do the cleaning up with the LEV then you eliminate the vacuum.

Solved.

Edited by user 13 July 2018 17:53:05(UTC)  | Reason: Spelling

thanks 1 user thanked paul.skyrme for this useful post.
Mersey on 16/07/2018(UTC)
firesafety101  
#11 Posted : 16 July 2018 14:04:43(UTC)
Rank: Super forum user
firesafety101

Has a fire risk assessment been carried out and what is the chances of a Dust Expolsion where fire can run along dusty surfaces.

I imagine if the housekeeping is poor there must be a chance of dust explosion.

peterL  
#12 Posted : 20 July 2018 08:31:22(UTC)
Rank: Forum user
peterL

Is damping down the spilled dust and simply brushing up not a simpler option - and ultimately less expensive, even if a bit more labour intensive?

Ian Bell2  
#13 Posted : 20 July 2018 08:57:30(UTC)
Rank: Super forum user
Ian Bell2

An informative document here.

http://www.wolfsonelectrostatics.com/01_hazards/pdfs/guidanceforplantengineers-staticelectricity.pdf

Page 2, right hand column particulary discusses dust clouds.

Steve e ashton  
#14 Posted : 24 July 2018 11:19:10(UTC)
Rank: Super forum user
Steve e ashton

Not all woodwork is the same... The OP is not talking about fine joinery / furniture work on kiln dried hardwoods being finished to a fine surface.... Pallets are generally made from softwood that has NOT been kiln dried... (may have been air dried - so maybe not green timber at 35% moisture, but generally 25% or thereabouts depending on local weather...). Slats are cut with a saw with reasonably coarse pitch... and not finished with a thicknesser/planer or sanding belt ... It is EXTREMELY unlikely that the initial operation will produce an explosible dust. The wood waste is not explosible dust since it is not in the particle size range that will explode (witness how close to the machine the vast majority settles for some indication of aerodynamic diameter).  The (very small proportion of) material produced that IS fine enough to spread any distance will normally be high moisture content - and hence even it will not readily explode (when it is produced).  There's ample literature available on this subject but many (in HSE and elsewhere) still seem to believe that expensive lab tests are necessary for every specific case... Please, do not assume that all wood waste is explosible fine dust.  It isn't.  There have been several major sawmill explosions over the years but these have generally been attributed to secondary explosions when accumulated waste on rafters and other elevated horizontal surfaces has been disturbed by an initial turbulent event (fire/small explosion)  It is very important to keep horizontal surfaces clear of significant accumulations, since these will dry further over time, and the risk of ignition / explosion increases from the material initially produced.  Provided your housekeeping is good, there should be little (if any) chance of explosion in this type of facility.  I have seen lab test results reporting that a sample sent for testing was explosible - closer reading suggested they had oven dried the sample for three days before testing, been unable to get it to explode, so sieved it to remove the coarse particles that were preventing the explosion.  So a tiny proportion of the sample - after removal of a large amount of water - could (with difficulty) be made to explode.... Therefore the sample was reported as explosible dust... And the sampling itself had already skewed the process by only taking bulk sweepings from horizontal surfaces some distance from the saw.....  This kind of quasi 'science' helps no-one. Sorry for the rant folks!

Bazzer  
#15 Posted : 02 May 2019 16:45:42(UTC)
Rank: Forum user
Bazzer

Mersey

Did you resolve your problem. I have the same problem now, a client has been instructed to use a M-class vacuum unit to clean floors and work surfaces of wood dust. Dry sweeping must not occur. I now have the prpoblem, does the vacuum need to be ATEX rated; it is not being used in an explosive atmosphere, as the dust is settled on work surfaces, but the dust being vacuumed could create an explosive atmosphere inside the vacuum chamber. A well knowm industrial vacuum unit manufacturer says it has to be ATEX, but cannot tell me why. As you have saud the price difference is astronomical.

When you see adverts on manufacturers sites, it shows standard equipment being used to vacuum up wood dust and recommends a standard type, but mentions nothing about explosivity. I have searched everywhere for clarification. Several years ago I had a sample of wood dust tested and it came back as flammability classitication group A, which suggests it is explosive in the right conditions.

Ian Bell2  
#16 Posted : 03 May 2019 08:49:47(UTC)
Rank: Super forum user
Ian Bell2

I would question whether you have a significant risk of an explosion.

Key parameters are particle size and moisture contents.

Remember the risk of an explosion theory modifies the traditional fire triangle of

1. Ignition source

2. Oxygen

3. Fuel present to burn

to

1-3 as above

4 Confinement of the dust

5 Dispersion of the dust in air

ttxela  
#17 Posted : 03 May 2019 10:21:55(UTC)
Rank: Forum user
ttxela

If I understand correctly the concern is about explosions within the vacuum itself rather than the atmosphere of the workshop.

I can't offer any specific advice on this but having worked in a number of small woodworking shops myself I've always used extractors similar to this; 

https://www.toolstation.com/scheppach-ha1000-1100w-50l-dust-extractor/p44573?utm_source=googleshopping&utm_medium=feed&utm_campaign=googleshoppingfeed&gclid=EAIaIQobChMIi76syY__4QIVFf5kCh22xQvqEAQYAiABEgJPhvD_BwE

Sawdust on the floor was cleaned by by removing the hose from the machine and vacuuming the floor with it.

These units are designed specifically for wood dust and shavings and do not appear to be ATEX rated?

chris42  
#18 Posted : 03 May 2019 15:30:49(UTC)
Rank: Super forum user
chris42

In a recent thread on weld fume a kind poster (Alan.J I think) at #24 has a link to a HSe doc and in the section before weld fume it also talks about wood dust. perhaps worth a read. there isw an expection of the HSE shown in the little chart.

link to thread

http://forum.iosh.co.uk/posts/t127992-HSE-changes-to-welding-risks

Chris

Robert I  
#19 Posted : 08 May 2019 11:17:11(UTC)
Rank: Forum user
Robert I

With a lot of valuable comments already made, there is also one important factor to consider, and that is the COSHH element of the wood dust.

Given that the explosion risk is to be resolved, there is no substitute for good industrial housekeeping, IMHO

John Elder  
#20 Posted : 01 July 2019 15:34:38(UTC)
Rank: Forum user
John Elder

Sometimes the easiest solution is to have a flexible duct fitted to a specific low level section of ducting on the LEV system controlled by a manual damper. The LEV system then is effectively used to vacuum up the spilt dust upon completion of the emptying operation. I have these installed as a standard when fitting out woodworking shops

John Elder  
#21 Posted : 02 August 2019 12:38:23(UTC)
Rank: Forum user
John Elder

A solution used in quite a few workshops is to have a flexible duct attached to the LEV ducting via a damper for isolation and the spillage and suck it back into the LEV system using that as a vacuum cleaner this is quit a common practice.

A vacuum cleaner can be used if it is a Class M vacuum these are suitable for wood dust.

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