Thread: Source for 150mm pvc fittings

Yeah, acc to US authorities wood dust is a carcinogen on par with asbestos.

As a turner I do a lot of sanding and the dust is all over. I wear a filtered visor while sanding, always have a box type air scrubber running in the shed and as well have the dusty picking up most of the stream of sanding dust as it comes off the piece.

I'm also guilty ... of smoking. Bit dumb I know, and I don't smoke much but I know the risks.

Originally Posted by Mini

Well that would work out about the same. I have used 2 x 45 bends throughout instead of one 90 to keep the flow rate up. I have never priced 90 deg bends.

G'day Chris. This depends on the type of 90 (88) deg fitting you use - they are available in 150 mm with a short or long inside radius. ( Can anyone elaborate here with correct terminology?)

A pair of 45s would be better than a 90 with a short inside radius, but not the flowing curve found in a long IR bend. The 90 deg bends in the 100 mm inlet to my cyclone (See second pic here) would flow much better the a pair of the short radius 45s you can see on the side branch.

It's a bit hard to see, but the 90 (88) deg elbows where the exhaust (green arrow) and where the 150 mm inlet penetrate the wall have a long inside rad to keep flow up. They were a bit dearer (forget by how much) than the tighter bends, but are a better choice.

Yes, both are available in long and short versions as you rightly point out. I wouldn't categorically say any one thing was better than the other until someone can front up with flow testing proof of air laden with shavings and dust. Flow testing air only is no proof of anything as far as I am concerned. I can flow test any pipe, it is easy with a manometer and that only takes a few minutes to make and has all been done before so is not worth repeating. I would think adding wood dust and shavings like what comes off a planer working flat out would have a drastic effect on what is happening through the bends. A bend carrying only dust laden air might not be so affected though there will still be some difference to clean air. Worth pursuing? most probably not but then it might be, who knows.

I am always curious when everyone accepts what is not proven and have been down this path before in other avenues, someone has to prove it to me and that hasn't been done.

Chris, haven't you finished the dust collection, yet?

I haven't done a thing more to it since you were here. If you don't tell anyone I won't tell about the screwdriver. I am dependent on No 1 son as the doctors have banned me from doing overhead work since my shoulder op. Besides that the Table saw/router table is giving me migraines as it requires four ducts and I am trying to figure out the best way to achieve that without it all becoming one big mess. A work in progress bit not much of the latter. BTW how's the shed going

Chris, In a world apparently full of people more than willing to take information from the internet as gospel, it's refreshing to find someone applying critical thinking. Nice one.

However, while technically I shouldn't have stated one is better than the other in the absence of direct evidence, I am quite happy to confidently suggest that a large radius bend will create less turbulence and thus flow better than the abrupt step often found in short radius elbows. I wouldn't necessarily stake my first born son on it, but I was happy to build a system on such an hypothesis. Had it not worked, I would then have moved onto testing the validity of my assumptions on fluid dynamics and particulate flow in bends.

While there is probably too much "a red paint job is fully sick and makes it go faster - trust me" going on in forums, I don't think it's practical to test every idea or design. I just assume the carbide tips on my blades are soundly attached - I haven't performed destructive testing to be sure a blade is safe, and I just assume Bernoulli wasn't on drugs every time I get on a plane because I haven't actually measured the lift of a comparable aerofoil .

Cheers
Mick

Mick, I think you have summed it up fairly well. I actually think for the average user whose DC is not capable of pushing 150mm pipe to its limits the difference between 2 x 45 and a 90 elbow is not going to be mind blowing either way. I like you took the pragmatic approach and just built it but it has yet to run as the build is not finished due to external circumstances. One of those is that I have had to extend my credit card limit to pay for it.

All I got to say the 150mm 90° bend in my system works good enough

Another option is keep an eye out in demolition yards, I managed to buy about 15 fittings inc. 150mm 45deg wyes, 150/100mm 45 deg wye etc for $8 each. I was lucky but it saved me a packet. I built my own blast gates and the short runs of flex are stuffed in the female ends of the PVC and held in with zip ties between hose clamps on each run of pipe. I'm extremely pleased with it, I now have to build another 150mm to 125mm transition out of sheet aluminium and sort out the bandsaw dust ports and I'll be happy.
I spent a lot of time doing research on the web and here before starting and it was well worth it.

Regards Ben Shepherd

Originally Posted by rsser

I've just sealed my joins with duct tape cos I just know that the setup will change as the workshop does.

I agree that is cheap or silicone sealant as well, easy to remove once you have to

Guys, on the topic of 1500mm pipe pricings, what one are you getting quoted on?!?

There are 2 different types available... stormwater pipe and sewerage pipe. From memory (pre coffee, correct me if I'm wrong!) stormwater pipe is about 1.6(ish)mm wall thickness and sewer pipe is about double that. Same goes for the price, I've been quoted $17/fitting for stormwater fittings at mitre 10 and $36/fitting for sewer fittings at reece plumbing.

Basically the extra wall thickness is there to prevent blowouts under pressure and litterally causing a $hit storm, lol. Seeing as we are working in reverse ordere here, ie sucking air through, not pumping water out, I think the wall thickness is of little consiquence. I got hold of a piece of 150mm stormwater pipe and gave it a good squeeze to test its deflection. Now I am far from being built like a gorilla, but I don't think that pulling air though the pipe would cause it to collapse any more than me giving it a good puck against a brick wall.

When I eventually get around to fixing up my new (ie peulled froma scrap metal pile) dusty, I will use the 150mm stormwater pipe and keep you posted performance.