Dust extraction

[Davedog]

Hi I want to install a dust extraction system for my workshop I am thinking of 40 gallon drum with cyclone 68mm pipe around shop and a rutland dk7109 vac . I was looking at the record cam vac with twin motor as well but very pricey, does any one know if I can use 2 rutland vacs together instead of the twin cam vac . Twin cam vac is 2x1000w motor the rutland is 1x 1000w motor each.

 

[sunnybob]

trying to balance 2 motors on the same system is almost impossible. one will work against the other and drive you insane trying to get two work as well as one.

 

[Davedog]

Thanks Bob if I buy the cam vac that has got 2 motors which you can run at the same time is this not the same as 2 vacs on the same system

 

[Deadeye]

You don't say what machines you'll be running, or your budget.
However, if your base comparator is a double camvac plus 68mm tubing, then perhaps consider going straight to 100mm?
100mm is cheaper to pipe (as monrose 6' sections; even cheaper as 110mm drainpipe). It gives you just over twice the capacity.
For the low pressure-high volume extractor, look for a 2-3 horse power extractore second hand.
Then put a cyclone (homemade or Axminster now have a 100mm version) ahead of it, and a HEPA cartridge as the exit (with poly bag below).

Two cam vacs will set you back £250 (or more depending on make); you can get a great second hand 2HP extractor with 1200mm^3/hour in 100mm for that.
A 100mm cyclone is £100 (or £50 home made); a 1um filter cartridge is £130.
Offset some saving on piping.

So for perhaps £100 more you can have a waaaay better system.

 

[sunnybob]

The two motor camvac has been designed from the start to allow their two motors to work together. If you read the blurbs it is a "two stage extractor" which is not a "side by side" system at all. Trying to achieve that at home with two separate machines joined by ducting is a whole different game, and will cost you more in time and parts than the result will be worth.

you dont say how big your workshop is or how many machines you have.
I had a SIP 50 litre drum extractor that cost barely a 100 quid, and it worked extremely well , even though it was so noisy I had to build a sound deadening box for it.

There are many options on dust extraction, but for gods sake dont cheapskate yourself. wood dust is a killer that sneaks up on you. get something that will do the job properly.

 

[Keith 66]

Last week i was assisting an Occupational Hygenist conduct a dust monitoring exercise at work. So two 15 minute sessions cutting 10mm mdf on a circular saw, a 15 minute session on a bandfacer & a 15 minute session on a union graduate turning a bowl. All the machines are fitted with numatic nvd 750 vac extractors.
I was fitted with a dust sampling machine with its collection unit clipped onto my shirt collar. I wore a dust mask. The hygenist also used an interesting machine a laser inferometer, this pumps air through a chamber & measures particle size of dust in the air. This ran continuously for several hours & it logs all the data recorded.
I wasnt surprised that the dust levels were high when i was machining as i suspected our extraction was crap anyway. What i hadnt realised was how high levels were later on. 20 minutes after stopping the machine was still recording high levels of respirable dust in the air. This is the dust that will do you in.

If you look at a Numatic extractor it can suck a volume of 144cu/m per hour. That is the manufacturers requirement for a Hegner scroll saw.
Even two of these coupled to a circ saw will provide about a 5th of the volume required to do any good.
I look forward to seeing the Hygenists report in a short while!

I usually wear a Racal Airstream helmet respirator but will be wearing the thing more from now on. I bought my first one back in 1984 & wore it out, i bought another & wore that one out too, bought three other second hand ones & reconditoned them. Out of all the guys working in the boat trade at the time in our area i think i was the only one with a powered respirator, all the rest used nuisance dust masks. Now i thank my lucky stars i did.

 

[worn thumbs]

I hope you will be able to give us an outline of that report,subject to confidentiality of course.I was aware of the Airstream helmets but found them a bit bulky so I bought the lighter Airlite and used it quite a lot.Only a few of us ever seemed to be concerned and what really used to irritate me was the way that extractors were switched off the instant a machining job was finished.So we could get back to giving our full attention to Simon Bates on Radio 1.

 

[Keith 66]

Well it depends on if the management see fit to share it with me. I wont be working there much longer if they dont!

 

[Sideways]

For info, the camvacs aren't anything clever.
Just one two or three motors, hanging in the tub, each totally independent and running in parallel.
The "two stage" description just refers to the fact that they just use overlapping paper and cloth filters around each vacuum cleaner motor.

Bob's warning above did lead me to some interesting reading about instability of industrial fans / blowers working in parallel
https://engineering.stackexchange.com/questions/8505/why-do-parallel-fans-blowers-show-an-oscillatory-behavior
so beware of trying to parallel up HVLP bag type extractors but I'm not convinced that this applies to the very different type of turbines used in vacuum cleaners.