Leeson Blower - I'm on the way

[RACEPUMPER]

Hey Guys, I picked this up the other week, it's a three horsepower, three phase motor with a blower at each end. The housings are about 2.5 feet in diameter, the inlets pipes 5 inches, the outlets 3.5 inches. Also bought a variable frequency drive - LG 10 horsepower capable\

Any thoughts?

[Tony]

That looks like a mighty interesting piece of gear you have there.

Are you sure the motor is only three horsepower ?
If the blower casings are 2.5 feet in diameter, that motor looks absolutely enormous for only three horsepower.
Could it actually be 30 horsepower ?
What does the rating plate say ?

[RACEPUMPER]

Just what I thought Tony, when I saw it in photos, but in real life it's a bit smaller, tommorrow I'll take some better pics for you and check those measurements and HP rating

I thought you'd like it Tony, you haven't seen one before?

Jim

[RACEPUMPER]

This the LG VFD I bought to work it.

[Tony]

The VFD looks really good too.
Did you get the instruction manual with it ?
Even with the user manual, initial programming to get it to do what you want it to do can be rather complicated. It took me a whole day to set up all the various options and features in my own VFD.

With that blower and VFD, you have everything you need.

[RACEPUMPER]

Yeah I did get the instructions, your right though, quite hard to follow, but time, I have.

[quote]With that blower and VFD, you have everything you need.

Yeah Tony! except a flowbench!! But I'm on the way. I'll try to draw you guys a picture so I can get some feedback before I start up the saw.

Jim

[RACEPUMPER]

Sorry everyone I was really excited about my new toy and got a BIT carried away with estimated measurements, here are the real details

Housing 16.5" outside
Impeller/fan 10.25"
Inlet port 5.5"
Outlet port 4.25"

All of these measurements are repeated on the other end in another mirrored blower housing

Motor
3 phase
3 horsepower
3470 rpm

What do you think now?

[RACEPUMPER]

Impeller/fan

[Tony]

Hmmm....

O/k 10.25" rotor 3,470 rpm. My guess would be about 8" of pressure.
That should be pretty easy to verify. I will be interested to see what it actually is.

[RACEPUMPER]

So Tony, if you think 8" test pressure can you estimate how high I can flow in cfm?

[Tony]

Flow is difficult to estimate, because there is no real way of knowing how heavily the blowers load the motor. But a wild guess might be 800 CFM per side. There is quite a large flow area in there.

You could always plumb both blowers in series and get 16"
Or even run your VFD faster than 60Hz , but keep an eye on motor current, and don't exceed the rating plate full load current for any length of time.

[RACEPUMPER]

Tony, Mate sorry if I sound stupid but if you think it may be able to pump great cfm like that, are you saying that the blower design isn't effecient enough to get up to 28" test pressure?

Jim

[Tony]

Just not high enough tip speed Jim to generate any higher pressure.

If the rotor was 20" instead of 10" it would develop four times the pressure.

You could get the same effective tip speed by doubling rpm, but doubling the rpm to 7,000 is getting rather fast.

It is not the efficiency that is the problem, it is just the blades in the rotor are not going fast enough.

[RACEPUMPER]

As you can see in the pics I could fit bigger rotors, there's room. Not easy to make / balance though.

Thanks for the info Tony, I'll keep thinking

Jim

[Tony]

If you run just one blower, and run it up to 7,000 rpm with a 2:1 pulley you would get maybe 1,600 CFM at 32 inches
Power would go up eight times (pressure x4 and flow x2)
Motor power would be roughly 1.5 HP x 8 = 12Hp

That might be your best bet. Use a 10 Hp motor with your VFD, and a 2:1 toothed automotive cam drive belt to drive the blower.