screw compressor & motor bases should they be machined?

[RANGER1]

Question about compressor & motor feet, should their mounting pads on base be machined, or as long as they are reasonably flat.
This would be a direct drive application with open drive coupling, no bell housing.
What would be a minimum acceptable standard, remembering alignment has to be carried out to a high standard.

[PaulZ]

Hi Ranger
We always get the bases machined it saves a lot of time when aligning.
We have done this for many years now, adds to the cost a bit but saved on commissioning time for line up.
We use the tolerance in the laser aligner which is pretty tight.
Old standard was 0.001" / 1" coupling diameter for both facial and radial.
Regards
Paul

[NH3LVR]

I have done hundreds of alignments without laser equipment. Field and production environments both. the only place I have seen bases ground is in a shipyard.
Of course if the bases are not well constructed, issues like soft foot can be a problem.
the .001 to .002 TIR standard I always used is more than close enough. Remember these are called flexible couplings for a reason.
I have no experience with the laser equipment, but am not against it. It may be faster and require less experience, but in reality is not going to give better results.
Also remember that your careful alignment can change quickly due to temperature, even if you do a hot check.

[RANGER1]

Have seen a package from a major screw compressor manufacturer without machined feet.
Of course with some difficulty aligned it as motor feet were only touching on four points, not full contact.
Seems pretty ordinary to save a few $.
What next?

[NH3LVR]

It has been a long time since I installed a screw package.
The last was an FES. It came with Shimless Motor Mounts.
Problem solved. No soft foot or other issues.
Fully adjustable-no shimming needed.

[RANGER1]

It has been a long time since I installed a screw package.
The last was an FES. It came with Shimless Motor Mounts.
Problem solved. No soft foot or other issues.
Fully adjustable-no shimming needed.

Yes have worked with them & good to work with.
If purpose built with them only way to go.

[weagle]

It has been a long time since I installed a screw package.
The last was an FES. It came with Shimless Motor Mounts.
Problem solved. No soft foot or other issues.
Fully adjustable-no shimming needed.

These are a God send.. Almost criminal on how easy this makes alignment procedures.

[Magoo]

open drives on a horizontal oil separator are a right pain in the butt, machined pads or not. Cold alignment then check hot alignment and average final set up, never perfect.