Thread: Blast gates

I'm about to undertake a similar set-up and very interested in people's replies as well. I've seen seen 100mm pipe used in permanent set-ups and the benefits would seem to be:

-Cheaper

-Smoother (less internal friction)

-Rigidity (less supporting points needed)

A possible downside would be static build-up?

As for blast gates, it might be cheaper to use PVC T-pieces with threaded ends and caps wherever you need an access point. Just unscrew the cap as required and connect the flexible hose from the machine to the access point.

Purpose made DE fittings do have the advantage of making a larger hole in your wallet ... wait a minute....

I do like the PVC T-pieces idea, never thought of that one.

As for blast gates, keep the ones you don't need closed and the difference in suction is negligible.

I've got my new pipes scheduled to arrive in early November. This will be the second system I've built. I spent the time to read up on the theory along with a pile of studies and learned that I needed to use 150mm pipe as a minimum for as much of the length as possible.

The basic premise is that a dust collection system relies on moving a volume of air and that the 150mm plus piping performs a hell of a lot better at this than 100mm pipe can.

In answer to your questions:

You shouldn't lose too much efficiency with multiple closed blast gates provided that the gates are properly designed and manufactured. The trick with gates is to keep them as close to your main line as possible. There will be some loses due to the turbulance created by a branch line coming off your main.

I minimise the number of branches and make them as smooth-running as possible. The only 90 degree bend I have is where the system exits the building and that is through a big radius, all other branches come off at 45 degrees.

The first system I built used PVC plumbing fittings, I had a bit more time on my hands then and I built my own blast gates. I've since found that if you shop around the cost of the purpose-designed ducting isn't that much greater than 150mm PVC pipe and fittings. The runs of pipe are a little more expensive but the fittings can be cheaper. I certainly couldn't be bothered making blast gates again.

The purpose designed stuff fits together with clamps that can be unbolted if you get a blockage and is easily rejigged if you buy additional equipment or rearrange your workshop. It also has a variety of off-the-shelf mounting hardware that makes fitting it up less frustrating. It's designed and made to move dust and chips from workshop equipment so everything just fits together smoothly right up to machines. There is no need to make special fittings, muck about with toxic glues or file and machine PVC as everything is available from the suppliers.

It is a bit more expensive but it came down to the fact that I'd much rather be spending my time woodworking than manufacturing bits of a dust collection system.

Don't glue the PVC, use duct tape instead.

Tape you can pull off. Glue and you'll curse things when you revise your plumbing set-up a second, third or even fourth time - as you most likely will.

Thanks very much for your suggestions especially you Horaldic for such a detailed answer. I think for the time being I will set up a fairly simple system in mostly 100 mm plumbing fittings and pipe with 3 blast gate outlets, minimising the length of the run and also right angle bends. I wasn't planning to glue it Waldo - I was thinking even pushed together it should be pretty air tight, maybe with some Vaseline and/or (as you say) duct tape. This should do until I really know where I want things to go.

Will the blast gate fittings and flexible hose (sold by Carbatec etc) fit 100 mm plumbing pipe, or is that where you need to make some adaptations?

Carbatec blast gates are ALMOST a good fit into 100mm pipe. They are a bit loose, ie wont stay attached with a 'push fit', but this is easily rectified by using a small self tapping screw or two through the pipe into the flange of the gate, then just go around the edge with the caulking gun.

As for the flexi pipe, that is about the same diameter as the plumbing pipe. The way around this is when you need to go from the hard to the flexi pipe, use a pipe joiner fitting on the end of the pipe, with the extra diameter of the joiner, the flexi pipe sits inside of it nicely. Add a bit of duct tape around the join and you're good to go.