Dust Control Ducting


(Joshua Hogendorn) #1

I’ve been getting quotes for dust control/extraction ducting.

The plan, hopefully, is to do a large bus that does an L shape in the shop, and then that will split off at points into a second smaller size which will be the majority of the system, which will end in flexible hose and a reduction to the particular tool size at the very end. We have 11 or so tools that could be ducted in, and 5 or so that absolutely must be ducted in, and we may have a few more on the way. There’s also a few things we could do with a system in place, such as a sweep port on the floor, a general air filter port in the top and perhaps even a downdraft table.

Something else to consider is that anything we build we will have to move, so that means it either has to be cheap enough that anything ‘made for purpose’ can be redone, or modular enough to move.

I believe our extractor is 250mm at the port, and we should be doing drops at 150mm (6") or so. Tools vary at their final size, 100mm, 120mm, 140mm etc. Some of them, like the felder tools, you can buy quick disconnects for that final adapter.

Some rules regarding dust control ducting design:

  • Keep it as wide as possible as long as possible
  • Have a long final straight run to the extractor if possible
  • No 90º bends, make 90º bends by making 2 45º bends. (this is more of a rule for pvc, for purpose ducting just does this). This also means no T joints, always use junctions that come in at an angle.
  • Minimise flexible ducting as its a) expensive and b) very inefficient
  • No hard stepdowns in size, use reducers that have a conical section. (reduces turbulence?)

This isn’t a rule, but the other factor to consider is that extraction systems build up static charge, so ducting should be grounded. Static charge is an issue in two ways. 1) fire hazard as an ignition source, 2) static charge reduces dust flow.

I have quotes for ducting parts from 5 different suppliers and am waiting on one more, as well as an equivalent build in pvc. I originally had them in this post but then realised its probably not ok to put them on the open internet. If you would like to help me put all the quotes in a big spreadsheet for comparison, that would be super helpful and I can give you access to everything.

So, having said all that, it really comes down to pvc vs a whichever metal system is cheapest, and its a given that pvc will be the cheaper option. I’ve done some really approximate costings based on a 225mm main bus with 150mm drops, and it comes to about $1300-1500. I think we have some pipe in that size already which may bring down the cost a touch, but most of the value is in the fittings. This pricing is based on using stormwater grade pvc (as opposed to dwv and pressure pvc), and my pricing was based on http://www.pipeonline.com.au/subcatDisplay/STORMWATER+FITTINGS

I’m 85% certain we will go with pvc, purely based on cost, however there is one big drawback and two minor drawbacks.

The big drawback is that it may be difficult/impossible to buy off the shelf blast gates that will fit pvc, and if that is the case, we will have to make gates ourselves. they’re not particularly complex to make but its something that someone has to do. However, if we did make them ourselves we could get exactly what we want, since we would like to eventually automate them, and they would likely come out much cheaper than buying any form of metal gates. (one steel gate from a local supplier is like $120 - $200, we could buy a full sheet of aluminium for $170ish).

The minor drawbacks are that pvc is not sold in exactly the right size, so some custom fitting would have to happen at each end, and that for purpose systems have a lot of custom or fit for purpose attachments (like floor sweeps) that would have to be made.

So, where to from here. If you want to help, this is how:

  • Find more suppliers to get quotes from
  • Help me put the quotes into the comparison spreadsheet
  • Help us finalise a design so we know what we need to order and hence a budget
  • Figure out how we can solve the blast gate issue (maybe we should just buy a cheap ($12?) 6" plastic blastgate from carbatec and go to bunnings and see what it fits.).