used centrifugal blower - looking for one in Australia

[Greg]

If anyone may know it would probably be someone on here. I'm thinking about replacing the 12 vacuum motors on my bench with a centrifugal blower, 3 phase motor and vfd.

Has anyone seen or know of a suitably sized blower in Australia for sale? I imagine there are plenty sitting in used machinery dealers but can't find anything with a google search.

[Tony]

Greg, you will need patience, but something suitable will definitely turn up. Try visiting some of the second hand machinery graveyards in your area, and keep an eye open on e-bay and the Trading Post too.

[Greg]

Tony, do you think this one would do the job? It looks to be a fair diameter by comparing it to the switch switch box and 3 phase motor.

[Tony]

Looking at it, that blower has all the attributes of Miss World.

Difficult to judge the size just from that picture , but probably at least 10Hp, and the proportions look very nice too.

Well worth putting in a bid I would say.

Let us know the result.

[blaktopr]

Maybe someone can use something like this. Can't find any specs on it though.
[url=http://cgi.ebay.com/PAXTON-CB95-CENTRIFUGAL-BLOWER-0_W0QQitemZ370255408366QQcmdZViewItemQQptZLH_DefaultDomain_
0?hash=item5634f12cee&_trksid=p3286.m20.l1116]http://cgi.ebay.com/PAXTON-....0.l1116[/url]

[riga team-1]

it is better..


[url=http://cgi.ebay.com/New-York-Blower-Pressure-2006-alum-J03874-105_W0QQitemZ350096396758QQcmdZViewItemQQptZLH_D
efaultDomain_0?hash=item51835f11d6&_trksid=p3286.m20.l1116]http://cgi.ebay.com/New-Yor....0.l1116[/url]

[Tony]

I would be a bit wary of that old Paxton.

The friction ball drive may be completely worn out, and the airflow is not going to be that high at the sort of rpm you will need to run it at.

The much larger industrial pressure blowers have far better flow and pressure characteristics because the internal passages are very large.
Even at low developed pressures they can move a lot of air.

Something really small can move a lot of air too, but only at ultra high operating rpm, and maybe fifteen pounds of boost pressure.
But when you slow them right down to get only one psi, the available flow drops away hugely.

Look at a turbo compressor flow map, they all lean to the right. Plenty of flow at high developed pressure, miserable flow right down at very low pressure.

The secret to judging flow is the size of the air inlet eye and scroll, and the discharge diameter.

Something like a turbo compressor with a two inch air inlet is not going to move anywhere near as much air at a very low pressure differential as a monster industrial blower with a four inch air inlet and three inch air discharge.

So I would avoid any antique centrifugal superchargers, and at least check that the modern ones develop sufficient flow for your needs at the very low pressure you will very likely want to run it at in a flow bench.

[blaktopr]

Thanks for the info Tony.

[Greg]

I just picked up that blower from the auction for $49 plus fees, you were right Tony, thanks for your help!

I'm hoping I can fit it inside my cabinet, it's pretty large but maybe..

I'm hoping I can plumb it up to the setup I'm currently using to change air direction, just need to wait and see what it looks like to plumb up.

Now just need to find a vfd to run it, I suppose I can use my bleed off setup until one turns up.

[Tony]

Wow Greg, what an absolute bargain, you have done very well indeed.

Can you give us the physical dimensions of your blower, especially rotor diameter, and the rating plate info off the motor ?

It may assist others to know the type of thing to be looking out for.

[Greg]

Will do as soon as it arrives, I just need to organise freight to get it here from SA. It cam from the Mitsubishi factory auctions, amazing amount of stuff has been for sale there. I imagine freight will cost twice what the blower did at least but still it's a bargain.

I'll pull it apart and clean/paint/check the motor bearings etc.. Just need to get some work out the door first. I'll snap some photos as I go. I made the blower box I'm currently using so it just slides out of the bench and I really hope there's room inside for this.

[Greg]

That blowe arrived this week. It's not in the greatest condition but for $49 I can complain. I just pulled one side of the housing off to see what it looks like, photos hopefully attached below. The motor is 3Kw but I'm wondering if I should fit a bigger one and maybe spin it faster. Tony, Given your knowledge, hopefully you'll have some answers! The fan is 680mm diameter, about 35mm across the vanes and 170mm hole in the centre. Any ideas how much air this may move?

Cheers,
Greg

[Greg]

another photo:

[Tony]

Ohhh... that is a LOVELY blower, you have really hit the jackpot.

The motor will almost certainly be two pole, about 2,850 rpm on 50 Hz.
That rotor diameter spun up to 2,850 rpm "should" produce around 35 inches of pressure over a very wide flow range.

A few extra rpm from a VFD, and the pressure capability will increase enormously !!!
For instance 60 Hz would be 20% rpm increase, and a 44% pressure increase (49 inches estimated).

It also has very large inlet and outlet flow paths, suggesting much higher potential flow than the 3Kw motor suggests.
That is also a pretty wide rotor. My blower is smaller, 2 Hp originally with a 12mm wide rotor. And that originally did 500 CFM. So I expect yours will have a fairly massive flow capability.

Make up some flat sheet metal plates with various sized round holes. These will stick to the suction air intake by themselves with air pressure. You can then measure the air pressure drop across each sized hole, and the motor current.

From that you can work out the flow, pressure, and motor current at several points over the full operating range of the blower

In other words get a feel for what the blower can do as it now is, and at what maximum airflow (largest hole) the motor overloads, as I expect it will.

Don't worry what it looks like. Some sand blasting and a lick of paint, and it will look brand new.

It may be better to do some testing before you rebuild the original motor. It will almost certainly benefit from a larger motor if you are fitting a VFD and plan some speed increase.

Basically flow increases proportional to rpm.
Pressure increases with rpm squared.
Horsepower is rpm increase cubed !

So a bit more speed will require significantly more drive horsepower.
But test it first and see what you have.
From that you can work out what is needed to get the flow and pressure you plan to run.

This is big blower going to make one really great flow bench.

[Greg]

Thanks again Tony, that's really good news! looking at the blower, it has a filter over the intake side which I can remove easily. I imagine because of the design of a centrifugal blower it will not be terribly efficient if I reverse it to change flow direction. My plan is to mount another pipe on the intake side and feed both pipes into a plenum where I can reverse the direction through the bench.

I'll take your advice and screw it all back together and try it out, I'm still not sure if the motor works. The cables were cut but they sometimes do that to save on OH&S hassles. I've seen some vfd's for sale that can be controlled by a pressure switch to maintain a constant pressure using voltage from the switch, that seems like the perfect setup. Apparently they can also connect to a card in a computer so maybe it could be software controlled, probably not necessary though.

P.S. I just measured inside my bench and I have 100mm to spare fitting it inside if I change the mounts a little. It should make quite a tidy setup!