fan for dust extractor

[radicalwood]

Hi All,

I have just been given a new centrifugal fan, single phase but it has an air flow of 1540 m^3 per hour.
Question are

1) do you think it may be too powerful. I am thinking either 4" or 6" ducting in the workshop.

2) I can get away with a baffled box and a paper filter for collection or do I start thinking about a cyclone.

3) Use of plastic down pipe, contentious I know

4) earthing down the inside of the pipe.

Any advice would be useful.

I can fit it with an inverter if needed to slow it down to give a lower air flow.

Cheers Neil

 

[Scrit]

Hi Niel

That's approximetely 910 cfm in old money, so a good size for a small shop. Personally I'd start thinking cyclone - take a look at Bill Pentz's Site - best resource on the net. There are some plans there, too (you can actually size your cyclone to fit the fan) as well as first rate on designing a system, pipework, etc. Bill's site will also give you extraction requirements for many common machines - for example my 16in planer/ thicknesser needs around 850 to 1000cfm, whereas the rip saw works well at around 500cfm. If at the end you then need sheet metalwork, ductwork, filters please post as a number of people here can advise. You say it's a centrifugal fan; could you elucidate (or better post a photo). Not all fans are designed to run in a "dirty" airstream (i.e. get hit by waste) - do that to an aerofoil fan, for example, and it will go out of balance and eventually explode or wreck the motor bearings, so this is an important question to answer....

Don't think of running it slower "to reduce airflow" - you need a minimum velocity to shift waste materials and whilst some of the latest industrial systems feature variable speed fans they do require special computer control systems. Most fans have a performance curve which means that they only operate efficiently in a relatively narrow speed range, so I wouldn't worry about that.

Regards

Scrit

 

[ProShop]

Hi Neil,

I certainly don't think it's overpowered, in fact depending on the machines you use I would say it's on the money for a small shop. Don't forget that when you plumb it in that 1540cmh is going to drop quite a bit with the various bends etc. and depending on how that figure was measured in relation to what level of filtration was fitted etc.
I think maybe 6" is a bit big for that power. I would be tempted at 5" (sorry 120mm), if your machines have 100mm outlets you can drop down from 120mm to 100mm at the blast gates or closeup to your machines extraction port.
IMHO Forget 4" for that size output. I used some metal Spirolux tubing & bends, cheaper than plastic & lighter and again IMHO easier to install.

As Scrit mentioned don't even think of slowing it down.

There are somewhere on the forum some threads from members who have made or making cyclones.

Hope this helps

 

[radicalwood]

Cheers guys, will start laying it out in the shop and making a motor housing. Sounds like a cyclone is the way to go, will have to have a quiet work with the fabrication shop at work.

Neil