Thread: Dust while milling timber.

I occasionally mill timber at a tree loppers yard and up until now we have been milling outside and being located near the coast there are often stiff breezes around to blow the dust away.

The yard is just 2 acres of an 11 acre multi-use site with the site owners living on a 1/4 acre at the front of the site.

As well as the tree loppers yard (machines, logs, wood chip depot, fire wood etc) there's a native nursery, a landscapers depot, but the largest proportion is taken up by a building materials reprocessing centre (bricks, concrete, rock, sand etc) fed by a very regular procession of multi wheeler trucks carrying building rubble in, and stuff out. These trucks trundling down the common unsealed access road which runs through the middle of the site generating lots of dust from their wheels and loads. Sprinklers on the sides of the road run for about 10 minutes every 2 hours to keep the dust down but it's a losing battle, especially on hot days with hot easterlies when the dust annoyingly blows towards the tree loppers section of the yard. In the afternoon the Freo doctor blows the truck dust away from us - NICE!

Before I got my dust detectors I used a chainsaw mill for many years which makes a lot of large chips and provided the chain is kept sharp not that much fine dust so I was not that concerned. I was probably more likely to be affected by chainsaws exhaust fumes from the sometimes 20 minute long cuts involved.

In 2016 we got a large bandsaw mill and again this was set up outside. It generates MASSIVE amounts of sawdust but also uses a lot of water to cool the blade which also reduces the fine dust generation by clumping the sawdust.. Anyway it was not really my job to do the bulk of the milling, and while I did use it for a bunch of purposes, my main job is to maintain the mill, so my dust exposure was something like about day a month. Occasionally the wind might swirl around and blow some sawdust back at me and I would then notice this later when I got itchy eyes. The couple of small Silky Oaks I milled a few weeks back also gave me a slightly itchy skin.

Recently we got a small Bandsaw mill and this is located under a 3 sided large vehicle parking/garage .
It's an amazing little beast but as you can see it also generates a lot of sawdust.
It also uses water cooling (the cylindrical Al tank on the top front of the mill) but it uses much less water - the sawdust still clumps but you can see the typical sawdust coming off during a cut (red arrow).
Millducts1.jpg

The boss loves this little machine and has been using it for many days running and I though I should do fine dust check.

Despite the large amount of sawdust the typical PM2.5 dust levels ~ 3-4 m from the mill are about 10-20 µg/m^3.
This is close to the same as the dust levels outside the garage although I did not measure any dust levels with trucks coming past - I think the building materials reprocessing facility is closed for Xmas.

At the operator position which is opposite the mills saw dust outlet, its very similar - 15-25 µg/m^3.
This is probably because there's a big pedestal fan oriented to blow the dust away from the operator.

I then decided to put the particle detector within 1m of the sawdust ejection chute (normally I would not recommend this but I'll explain below.)
You can see the sawdust coming our of the bandsaw mill as shown by the red arrow.
You can also see how the sawdust tends to clump due to the water cooling.
Milldust2.jpg

So selector shows 35 µg/m^3 for PM2.5 and 41 µg/m^3.for PM10 which is not that bad and nowhere near as much as I expected.

I think this may reflect the effect of
- wood still has quite a bit of moisture in it
- a sharp blade (BTW this is hard wood - Lemon Scented Gum)
- water cooling the blade clumping some of the fine sawdust - this is why I was game to place the detector that close to teh saw outlet.

Anyway I will do some more measurements and report back.
The site proprietors are mad about the trucks constantly making dust and like to come out and berate the truck drivers for driving above the speed limit and making more dust than necessary.
This morning they saw me using the dust detector and asked me to measure the truck dust when they start up again next year.
They just love telling the truck drives WHAT FOR about the dust and said they said they will use professor bob's results to give them an extra serve or two.
There's also a limestone processing site next door they want some dirt on as they occasionally emit large volumes of dust.