Motor size for dust blower

Hello there,


I am just wondering if you can help me with a problem I have.



I bought a blower at a second hand yard without a motor and am trying to determine what speed the motor needs to run at to extract dust from my small woodworking shed, (just a few machines) and what size motor will be needed and what pulleys sizes etc.


Make = Richardson

Size = 2D
Job No on plate = 7265

Inlet/Outlet = 10"
Body of blower (round part) 24 "
Fan width = 15 "

Shaft for pulley = 20 mm approx
Size of pulley on blower at the moment = about 7 1/2 "




Thanks in anticipation if you can help.



Gerald

You will need at least a modern 4HP motor, spun at least at 2800 to 3600 RPM if you wish to draw enough air to clear wood dust from machinery.
Running it with a lesser HP motor at that speed will be too great a load and it almost certainly burn out the motor

BUT. . . . .
BEWARE - the impeller may not be designed to run at these speeds and could fly apart in trying to do so.
It also may only be balanced for slow speed use so may rapidly make the blower vibrate or jump around leading to long term destruction/damage.

I can't tell if the impeller cover is cast iron or not, if it is it would provide some protection but it could still explode like a bomb and destroy your shed.
Does the impeller or housing have any cracks or small chips?
What does the impeller look like? Is it a radial or curved vane impeller?
I would take the whole thing apart and examine it carefully - maybe take some photos and post them here to see if we can see anything.
Also I would replace any bearings while you are at it.

A few years back there is a story of a large impeller coming loose and going straight through the impeller housing, a shed wall, then through a fence and into a neighbours yard many meters away.
Loose impellers can easily kill someone if they are hit.
Most blowers I have seen run from pulleys like that one run at less than 2800 rpm.
The twin pulley design suggests it was run with a 5HP 1400 rpm motor with the same size pulley or a 2800 rpm motor with a smaller (ie 4") pulley.
Radial vane impellers also make a lot of noise.

Are there any specs stamped somewhere on the impeller housing?

Assuming its OK to spin the impeller at 2800 rpm, a 4HP single phase will require a dedicated 20A GPO to be installed in your shed. A smarter way would be using a 3Phase motor a VFD. A carefully programmed VFD would enable the motor to start slowly and it could then probably be run on a 15A GPO.

If you were concerned about safety it could perhaps be spun at 1400 RPM but then it would draw only half the amount of air.
You'd have to perform some static pressure measurements to determine its likelihood of pulling sufficient air at that speed.

To test it out running at higher speeds a strong wooden box from say 50 mm thick timber enclosing the impeller would be advisable - its not perfect but it may just prevent the shed from being destroyed.
I built a similar box to test an upgrade to my DC (see pic below).

The box is made of 50 mm thick pine and has a 6mm steel cover plate I the initial tests remotely with me standing just outside the shed and with one hand on the power switch just in case.
Bear in mind I already knew my impeller could spin at 3600 rpm, what I wanted to determine was if it would safely spin at ~4000 rpm but the high air flow at that speed made a hell of a screeeeech that I never use it at those speeds.

The iPad on top of the steel plate was to monitor overall vibration using a pro Vibe App called "Vibration".
The WIP for that project is here https://www.woodworkforums.com/f200/...=BobL+impeller
Attachment 469083

The metal working side of this project is in the MW forums here; Boring out an impeller collar
You need to be a member of the MW forums to see the pics.

The Cincinnati Fan Catalog has a wealth of information. Here's a table on a very similar fan to yours that, with a little study, can give you some insight into your issue. Look it over and then ask if you have questions.

Attachment 469102

I searched the name a little and found this ad. Used richardson Flakt Woods no 2 dust extractor fan and 3 phase m Industrial Exhaust Fans in OTTOWAY, SA

In case the link doesn't work the description is below. Looks like you can use it but will want a 5hp motor. Should you have any concerns about the integrity of it you could disassemble and take it to a non destructive company for magnetic particle inspection and or dye penetrant inspection to crack check it. You might want to remove any rust on it. Flakt Woods was located in Melbourne but seem to be out of business. You live there so might be able to find them to get the information about it.

Pete

PS. Welcome to the forum.

PSS or is it PPS?. I just remembered you can buy small inspection kits of dye penetrant that come in spray cans. With them you could do a crack check yourself. Look for Magnaflux Spotcheck as a brand or Dye Penetrant Test Kits. Basically you clean the area, spray on the dye, clean off the surfaces, then apply a developer that pulls the dye from any cracks.

Richardson Flakt Woods no 2 dust extractor fan and 3 phase motor on stand

Richardson are now known as Flakt Woods Australia, the same fan is still built today and known no 2 dust fan
This is a heavy duty material handling fan suitable for a very wide range of applications.
Port diameter in and out is 267mm
Mid curve power requirements at 2 pole speed 2900 RPM aprox 9KW
Mid curve power requirement at 4 pole speed 1450 RPM aprox 2 KW
I cannot read the plate on the motor but I would guess from its size its around 10HP 7.5KW

how much did you pay for it?

One difference between Dave's Cinncinati chart and Pete's motor specs are due to the indifference in inlet//outlet diameters. You could alway reduce the diameter from the 267 down to 200 mm and not restrict the flow that much then you could run a smaller motor along the lines of the Cinncinati chart. I suspect the impeller is a weighty beast so it will benefit from aslow start motor using a Vfd.

Based on the chart I would target a 10" SP and 1600 CFM. This requies about a 3100 rpm 5HP motor - doable with a 240V VFD. This SP would allow for fitting a cyclone although you'd need a serious stand to support the blower and motor on its side AND this assumes it will work on its side as not all impellers can do this. If you don't used a cyclone you will need to set up filters of some kind. Then you could work in the 8" SP, 1800 cfm, 3000 rpm range with the same motor/VFD combo.

i don't see any of this as a guaranteed "turn on and forget" but I'd recommend careful trials with your hand on the VFD off switch. Provided it is well programmed a VFD will protect itself and the motor.

was this the one that was jury-rigged with a motor and running, shown on a video on FB with a basketball suspended in the outlet stream?

Well, when Bob suggested an operating RPM I couldn't resist taking another look at the table I posted. I wanted to get an idea of the fan curve at 3100 RPM. After a couple of interpolations I thought it would be fun to try a curve fit to the whole table.:oo: Once I realized how long that might take I should have just stopped, but it's like taking a spoon to a carton of ice cream with the intention of only eating a small portion.

Anyway, after wasting several hours on a completely unnecessary project I now have the data arranged the way I like to look at it. Here's a plot of both static pressure and power consumption versus flowrate with RPM as a parameter. Maybe you'll find it as much fun to stare at as I do.:p

https://www.woodworkforums.com/attac...0&d=1582657167

Attachment 469150