Thread: Source of long radius 90 deg bends.

Depending on size, unless you go specifically for dust extraction ducting, you are out of luck. There are PVC fume cupboard manufacturers who will custom make them however they are very expensive.
I would suggest using 2x45 bends with a straight length between


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Go to an electrical wholesaler and they will have long bends in larger sizes

Are we talking about dust extraction or conduits? For some reason I’m thinking dust extraction lol


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2R bends are relatively common but as far as I know they are not available in stormwater fittings - you have to ask for DWV fittings.
They will fit each other without any problems

2R bends can be expensive eg I have seem the 150 mm size going for more than $30 but pipe-on-line has them for <$20
see
DWV FITTINGS - DWV PLAIN BEND - Pipe Online - Retic Fittings , Plumbing Fittings, Reticulation Supplies supplied Australia wide

As for the 2 x 45º bends idea, I used to think they would be at least as good as a 2R, but maybe have a look at this.
T1, T2, T3 . . . . refs to trial 1, trial 2 trial 3 etc
150mmbends2.jpg

With the 150 mm 2R bend averaging ~1% flow loss, even if you have the $$ required to purchase and the space to accomodate the very large radius electrical conduit bends there's no real benefit in using them.

so your saying, where ever possible use 2 x 45* rather than 1 x 90* or am I not reading right. ie 90 degree 2R is 2 pieces and 90 degree 1R is 1 piece.

No, use DWV 90 degree elbows - they are 2R. Stormwater 90 degree elbows are 1R.

all good have a box of DWV ones from pipesonline waiting to be fitted, read that and thought.....nah wont say what I thought..........

Originally Posted by Tonto

so your saying, where ever possible use 2 x 45* rather than 1 x 90* or am I not reading right. ie 90 degree 2R is 2 pieces and 90 degree 1R is 1 piece.

On the graph, the taller/higher the colour bars the greater the flow loss.
The 2R bends (Blue) have the same restriction (~1%) as one 45º bend (Red) and about half of 2 x 45º (green)separated by a short section of pipe.
The 1R bends (purple) have a 7% loss.

BTW I should add that this is for ~1000CFM if your DC is not up for this or your machines are constricting the flow the effect won't be quite as large as this.
Lower air flows tend to reduce the differences.

Originally Posted by Runningman

Are we talking about dust extraction or conduits? For some reason I’m thinking dust extraction lol

Yes, dust extraction (as it was posted in the "dust extraction" forum ). I should have been more specific as several people were confused.

Originally Posted by BobL

2R bends are relatively common but as far as I know they are not available in stormwater fittings - you have to ask for DWV fittings.

Ooohhhhhh, so what you're saying is that I don't need to find a long radius DWV fitting, as they are inherently a long radius relative to stormwater fittings! No wonder I couldn't find them .

For anyone else with the same confusion, below are images of standard stormwater and DWV 90 fittings, and can observe that the DWV is indeed a long radius.



Thanks a lot Bob.

Lance

If the sewer fittings don’t suit you the electrical ones are a much bigger sweeping bend again

They might be a bigger sweeping bend but will they fit the 100mm pipe? Asking as I believe they are different, 110mm OD DWV V 114mm OD Conduit.
Kryn

I just looked and here in the Great White North Schedule 40, 6"dia x 24", 36" & 48" sweeps start at $50 running upwards of $160+ with shipping on top of that. I would be surprised if Australia was cheaper. So unless you are in the electrical trade and can snag them dirt cheap (if you can tell the members where) or must have one or two long radius sweeps for a special part of the system they are just too expensive for most. Once in that range the pressed steel systems like Norfab become a consideration.

Pete

As well as cost, long sweeping bends just take up too much space.
Unless you have a lot of space which can accomodate the wide sweeps they are generally a PITA for DIY situation.

If my radius bend was 1.5 times the diameter where would that put me on the chart for percentage of air flow loss ?