PVC/Plastic rigid duct..fume extraction..sizes??

[steviec_lj]

Right, acquired quite a while ago, probably 8 years to be honest, are three lengths of what I had assumed were 100mm plastic duct.

Roll forward to today, and a shift around in the workshop, I’m now looking at a fume extraction system utilising one of the many bouncy castle blowers I picked up cheap, again probably 8 years ago!

150mm “inlet” on the side of the blower, so automatically I’ll need a 150mm flanged spigot and a 150-100mm reducer. Not a problem me thinks, and trundle off to browse eBay, Amazon, etc..

Brain fart moment, I go measure the duct that’s sat in the roof of the garage and bugger me those aren’t the measurements I was expecting. Now I did this with a tape measure..

98mm internal dia
102mm external dia

I had a rummage in the ventilation bits box I’ve accumulated, and I have an end fan that fits snugly in the pipe, and an external vent so it must be somewhere in the ball park of rightness..

Do these measurements sound about right for “100mm/4”” duct, or is this some special brew that I’ve acquired? I don’t fancy having to spend a bundle of cash on bits to find the right combination to be honest.

This will solely be for fume extraction above the welding bench, through a filter of some sort, to the outside world.

I have a dust and chip extractor for anything/everything else!

 

[Paul.]

4" is 101.6mm, I made one exactly as you describe from a bouncy castle blower and a piece of plastic 4" spiral wound ducting, it worked a treat if a bit noisy, ducting is normally measured on the inside dia.

 

[500e]

I have spiral duct as well & a hydroponic fan as welding extraction in home workshop

The fan plugs into the wall outlet with cap on to keep WS toasty other pic is where it lives when not in use