Hello,

I have these blowers to align and take vibration reading for. They have a plate on them that tells me how to set the alignment up for thermal growth. I also have read the PDF manual and it has a calculation in it as well for thermal growth. Is this what I'm supposed to do each time? I see some of the blowers don't have shims under the blowers like the plate says. Why? I'm thinking that they have been aligned with keyed in targets in the alignment tools and it compensates for that. If that is the case though, and you don't have that tool, how do you calculate the differences so you don't have to shim the blower? Hopefully you can view and read the numbers on the plate. These machines are 150 HP and are running at 3600 RPM so the alignment tolerance is quite close. Any help here would be appreciated. Are there any vibration signatures in the spectrum that are commonly high for these things? I don't know the # of vanes in these either. Thanks.

A picture of the plate on the blower.

A page from the PDF Hoffman Manual about alignment.

The hot shaft position should be 'level' or square with the earth, not the cold. Generally a Thomas shim pack coupling is used which may not be the best depending on application. Thermals can be calculated via expansion constant x D x delta T (6.3 x 10 E-6 for steel). In addition axial location or position or air gap is critical.

A good portion of time Hoffman gives thermal growth information.

Have you taken vibration readings on these blowers yet and what are you getting?

When you say each time, what do you mean? If you change the blower for rebuilding then I would say yes. If you rebuild the motor then the blowers become your stationary unit (growth already compensated by shimming) and align motor to blower allowing growth per manufacture instructions.

Outlet of these blowers can get pretty hot (depends on process) compared to the inlet that is sucking in ambient air. So the outlet will grow allot more than the inlet. Hot alignment a must.

Softfoot, as with any alignment, is a big concern. I have seen a field technician from Hoffman loosen the blower shell housing bolts (new blower) and using a dead blow hammer rap the housing. This allowed the housing to level itself (housing twisted into place) to the fabricated base and help to limit the softfoot. On one of our Hoffman blowers the technician did pull down on one corner more than the other to better level the base for the blower. After that he did not touch it again and completed the alignment.
I would recommend only doing this after talking to Hoffman and with field technician present.

The fabricated base has more flexibility than you would think and the foundation can distort the motor and blower base. The isolation pads under the fabricated base help to compensate for the foundation irregularities and by not bolting down the base hard to foundation the bolts just hold unit in place.

After saying all the above, I will say the blowers had a very long and reliable life.
As always, consult with the manufacturer, after all it is their design.

Just my 2 cents. We had 2 at our plant that looked just like yours but were 125 HP.

This message has been edited. Last edited by: Don Jones,