Wearing pleats in the workshop

As a general rule, wearing pleats in the workshop is not the best idea. Other than being just a little too frilly to be shed-like, you’d get a lot of really weird looks from visitors!

Catherine-Malandrino--Gray-pleated-jesery-bubble-dress-785730

Of course, there is a place for pleats in the workshop, and that is in the cartridge of the dust extractor. So why would something frilly be a practical accessory in the workshop?

Many dust extractors use a cloth bag. Cloth bags are great. They are cheap, which is great. They are easy to clean, which is great. And they are great at spreading as much fine dust as you’d ever not want to see around the workshop. Sure, the large stuff gets captured, but that is stuff you can sweep up with a broom and shovel, so one way or the other it is easy to dispose of. The fine stuff will get you every time. In Australia, all wood dust is regarded as carcinogenic.

Many cheap dust extractors would have a cloth bag at the top and bottom. Awesome – two cloth bags to let the dust fly!

sealey-dust-extractor-2hp-240vIt is probably not fair to badmouth cloth bags too much – reasonable ones are running 5 micron, which isn’t much worse than what a pleated filter can achieve anyway.

So what is the advantage of a pleated filter?

A dust extractor pushes through a certain quantity of air. And what goes in, must come out. If you have a cloth bag, the air that leaks through the holes in the cloth to equal the amount of air that is sucked in the hose. As the holes clog, the total amount of air that will flow will decrease. So a filter that is easy to clean is an important consideration. Cloth bags can be banged out, blown out with compressed air, even washed in the washing machine. The limiting factor though, is the total surface area of the filter (the bag).

If you increase the surface area, the total amount of air that will need to pass through doesn’t change, so as the surface area is bigger, the holes can be smaller and still achieve the same through-put of air.

Where it comes to cleaning, pleated filters have a system where you wind or move a handle, that causes the internal baffles to be impacted, dislodging dust and allowing it to fall into the lower half (collection) for the extractor.

Pleated filters used to be only available on expensive dust extractors, but these days you can pick one up to retro-fit to your machine for under $180.

Considering a cloth bag replacement is around the $80 mark, this is a viable, and a superior option.

Even so, in saying that, any dust extractor that is allowing particles back into the workshop environment is not ideally placed. I get a bit of flack on here about my preference in not having the dust extractor in the main shed, but then I’m not breathing air that has been filtered to allow the lightest particles to remain. Once the dust-ladened air is removed, it doesn’t matter how fine the filter is.

However, when used in combination with a good air filter you can get the dust collection, and the air quality you are looking for, or at least closer to achieving the ideal.

So if you have a cloth-bagged dust collector, consider the pleat as a desirable fashion accessory, that is also a desirable feature improvement!

Trupro 2HP Dust Collector

I’ve referred to my new dust collector (or dust extractor, depending on your terminology) in a number of posts, but noticed I have been rather lax in not discussing the machine itself.

Where it comes to dust collection, bigger is definitely better. Oh, and while we are on the topic of bigger, let’s quickly touch on what we are trying to collect.  In a workshop, sawdust takes all sorts of forms – and even the term sawdust is misleading – the saw is only one of a phenomenal range of machines and tools that can turn wood into a waste product that we want to collect, store and dispose of.

The waste can be fine dust through to heavy wood shavings from a handplane, and everything in between.  Some are easier to collect than others!  Fine dust is nasty for the lungs, and relatively easy to collect, so long as it is actively done as the dust is generated.  It is very light, and is picked up by pretty much any type of extractor.

The heaviest stuff (shavings from turning, or from handplanes), is almost easier to get with a broom……or a shovel.

In between, we have the jointer/planer and planer/thicknessers.  These produce a wide range of results, at the same time, and huge quantities of it so that is what is really desirable to pull away with an extractor.  It can be quite long and thin, and can easily block a pipe when air flow is insufficient.

So onto the dust collector itself.  Sourced from the Woodworking Warehouse, value is $A1175.

Trupro Dust Collector

Trupro Dust Collector

(yes, it is a photo I’ve used a couple of times already, if it looks rather familiar).

The collector has 2 main components – the motor and extraction fan, and the collector itself. The motor, as mentioned is 2HP, but boy does it draw a current on startup!  It tripped out the breaker on a powerboard every attempt to start it, so have had to dedicate a primary power point to the machine (still 10A), and that has solved any startup issues.

The motor drives a rudimentary centrifugal fan.  This is not uncommon in dust extractors, the clearances cannot afford to be too tight, or the parts too fine due to the bulk of the particulate that the fan is expected to cope with.  Also, given that it is sucking from a workshop there are all sorts of other bits and pieces that can also be picked up and fly through the tubes into the fan blades.

The motor is not particularly noisy in its own right (it is an induction motor), the noise is certainly from the air flow.  I’m not sure if the design could be improved to smooth out the airflow to reduce the generated noise.  However, it can’t be a particular criticism of this unit, because it is a very common design. The overall quality of the unit is apparent in the build of the 60kg unit.

Airflow rates: The machine is rated at 1200 cfm (2040 m3/hr).  This is around the median for a 2HP machine.  If you put it in a different vein, the total shed volume is 80 m3, so in theory this machine could empty the shed 25 times in an hour.

In practice, using an airflow meter, I’ve estimated the actual performance of the machine in 3 orientations:

As supplied with the twin 4″ connection points, both open.  Flow rate 28 m/s

As supplied, with one 4″ connection point covered with the supplied cover. Flow rate 45 m/s

With the twin connector points removed revealing the 6″ entrance. Flow rate 33 m/s

These figures are much higher than they should be, so our guess is that my assumption that the measure of flow speed being the average across the range of speeds experienced (between the edge of the pipe and the centre) doesn’t hold true, and it is really picking up the peak speed only.  I’ve removed my conversions, because the ones in the comments make a lot more sense than what I came up with!!

The other side of the DC is the collection aspect.  A basic form of collector uses a dust bag top and bottom.  These need to be air permeable, as the air being pumped in has to have somewhere to go – through the sides of the bags filtering out the entrained dust.

This unit uses a tough plastic dust collection bag on the bottom, and a spun-bound polyester pleated filter on the top.  This is where the air escapes the system.  This pleated filter can filter out particles as small as 1 micron.

You’d (correctly) imagine that a pleated filter would fill with fine dust, and the filters are not particularly cheap.  There is a way to clean them, or at least knock a lot of the dust loose so it falls into the lower bag.  Built into the pleated filter is a 3 paddle cleaner, and by rotating the top handle through 120 degrees results in the paddles beating every pleat, releasing the trapped dust.

Pleated Filter Cleaning Paddles

Pleated Filter Cleaning Paddles

This is a photo up into the top filter.  You can see about 1/2 the pleats, and 2 of the rubber tipped cleaning paddles.

So an effective dust collector / dust extractor and one that you can use in your main shop because of the 1 micron filtering of the air being exhausted.  There is quite a bit of noise generated by the unit, so either you wouldn’t want it running until needed, or some form of noise block wall shielding it from the rest of the shop.

Overall, this is a solid machine that performs.  I have some problem with the intakes getting blocked with large particles, such as planing shavings, and the long fibres formed with the thicknesser, but this can be addressed with either an added 1st stage cyclonic collection, or perhaps by removing the coarse grate the is across each port (to protect the blades). Otherwise, it has plenty of suck, and that is what counts in the end!

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