Dust Collection Ducting - Bends and separator step down

[burn]

Hi,

I have finally finshed my lean-to next to my shed and now intend to move the 2HP DC (1700cfm supposedly from Carbatec - better impeller?) and the separator out to the lean-to. The separator is one of the Veritas cyclone lids.

I looked into 6" (150mm) metal pipeing, but since the elbows etc were around the $40+ mark, I think I will stick with 6" plastic, as it's fittings are around the $10 mark - and do the grounding with copper wire.

I need some advice.

1. When forking off a branch, I intend to use a wye fitting connected to an elbow before dropping straight down, at which point I'll put in a 6" to 4" reducer plus blast gate and then run a short 4" flexible hose to the machine. Should the elbow (up at the wye fitting) be plastic or perhaps a bit of 6" flexible hose? With plastic I figure the 'bend' to the 'down-pipe' will not be as 'round' as a flexible hose, but am I right? I believe the less 90 degree bends the better.

2. I have the separator outlet atteched to the DC with 4" flex (the second 4" port on the DC is closed). The inlet into the separator is also 4". What problems will I face if I fit a 6" to 4" fitting into the separator lid (aside from structural ones). IE will it be a serious issue if I run 4" from the DC to the separator but then 6" outwards to the machines (with 4" stepdowns actually onto the machines.

Thanks in advance

Burn

[Waldo]

G'day Burn,

I can't offer advice here as I am myself looking to hook my machines up to a C/T 2hp extractor myself and will be interested in the help you get.

[Jack E]

Burn,

I can't help either but I have a related question.
If you have a 4" pipe and a 6" pipe in the same run is not the whole run restricted to 4".
If you want 6" don't you have to run it the whole way?
The way I think of it is if you blocked/restricted your pipe at the DC end it would decrease air flow volume and increase velocity. This would also hold true for a restriction anywhere along the run which is what a reduction from 6" to 4" is doing.

Jack.

[gatiep]

I have done my shed in 150 mm PVC stormwater pipe and fittings. Do a Google or search on this BB for Bill Pentz. There you will get more info on dust collection than most anywhere else............it is worth a study, not just a read as Bill is an expert on the subject. In short use 2 x 45 deg bends with short piece of smooth pvc pipe inbetween to make a 90 deg bend, stay with the 150 mm to as close to the machine as absolutely possible and keep the flexible 100 mm or any other size to the absolute minimum as it creates toooooooooooo much resistance and kills the efficiency of the system. With the 2 hp system there really is no need to earth the pvc for other than static schocks as the chances of an explosion at the relatively low flow rate and volume is really unlikely. My ducting is attached to my colorbond shed with metal strips and I can't say that I can sense static in the system.

Its all there on the Pentz site!

[Harry72]

Although 150mm is the best size with a 2hp+ system, two runs of 100mm will still flow enough, my system runs a 150mm mains but branches 100mm take offs, but keeping that in mind my TS will have (not yet finished) 100mm to the saw base and 100mm to the overhead guard so the flow is still good. Imp using an aux take off with some 100mm flexi for the overhead draughting ATM.
The take off to the saw base is the last on the 150mm mains and is always open (has no blast gate) this way when running any other of my machines (5 of) there is always an airflow going along the whole length to keep up the velocity, this means there is always two offtakes open which should flow around 1000-1300cfm(my dusty is a 3hp 4 bag).
Going from 4" to 6" then back to 4" will flow like a 4", it would be best to mod your separator to accept 6"... but I think the contents of the separator will end up in the dusty anyway using 6". I reckon kill off the idea of a separator (unless its a cyclone) and put the dusty outside the shed in its own shelter this way you wont loose any efficiency that the separator presents, this way the fine dust is vented outside away from you... must be careful of wind direction and irate neibours.

[keith53]

Burn,

I've spent a bit of time the last couple of days looking at Bill Pentz's website:

http://billpentz.com//woodworking/cyclone/index.cfm

it really is worth spending some time on.

My DC is a 2hp unit with two 4" inlets. The two inlets form into a removable single inlet of 5" diameter. This is just a standard Taiwanese machine so maybe yours has something similar?

I'd decided to use 4" PVC to reticulate my system but after reading some of Mr Pentz's material, I've decided to go to 6". I know Bitingmidge has done a really good job of making some 6" blast gates for his system so when he returns from his overseas jaunt, maybe we can persuade him to post some pics?

Cheers,
Keith

[burn]

Thanks to all who have responded.

I kind of figured that the seperator would throttle the system, but confirmation is what I sought. I had visited Bill's site some time back, but it seems he has been busy since then. Well, it looks like I will go 6" everywhere.

Like Keith, my DC has a 5" port which has been split into 2 x 4" connectors. I will start by putting a stepdown connector from my 6" ducting into the port - eventually, I'll do a cyclone and see what I can do about this 5" port.

I will then do a main run into and down the length of the shed along the ceiling with wye connections every so often with a 6" drop to 'near' the machine then convert to 4" to go into the machines until I get the confidence to enlarge the machine's standard 4" ports.

As everything I have has 4" ports (or less) at present, I'll initially use some 4" blast gates I have here at the 6" to 4" stepdowns but will eventually follow Bill Pentz's advice and together with some advice from Bitingmidge put some 6" blast gates at the wye points to vertial drop connections.

Again thanks to all who have responded. It's now off to a plumbing store to see about pipes and connectors.

Burn

[bsrlee]

One advantage of the 6" pipe, even if it eventually runs into a 4" reduction, is that there should be less fritional loss to the air stream with the bigger pipe - I think that is what Bill P. is talking about - the bigger the pipe the better the air (and dust) flows thru' it.

If you can afford the 6" pipe, I'd run it for all the main runs & drops, then just put 4" at the ends to the machine/s. If/when you drop from 6" back to 4" or 5" just make sure that the connector is offset to the bottom - it is a common pipe plumbing part - so there is no buildup of junk against the bottm lip.

When you are going around corners, get the biggest corner curve you can - the blokes who put cabling in the street seem to have ones at least twice as smooth as the regular plumbing ones - having a chat with a beer to the blokes at the nearsest cabling depot may prove fruitful.

If you are going for ANY metal parts in the system then static should be a non-issue as you can just ground the metal parts - the zap problem only seems to occurr where the whole system is insulated.