Bolt bound, Alignment in horizontal position


What methods or techniques do you use to resolve a horizontal bolt bound condition when performing a routine alignment task? Do you ever slot the foot bolt holes? Do you beg for more time from the powers-that-be to allow you to attempt to reposition the driven component? We have encountered what we believe to be situations where the OEM has not adequately aligned the component and modifications to the mounting base is required. Does slotting the holes of the feet have an adverse long or short term affect? Is there a maximum that a foot hole can be slotted? Your input is greatly appreciated.



Charlie RB

Original Post

Your use of "routine alignment task" makes me ask the question is this a first time alignment, or is it a machine that has been in extended service and for some reason is being realigned?  If it is a machine that has been in service, one has to ask a few questions:

1.  Was it ever aligned properly?

2.  Could there be some foundation issues that have caused a shift in machine position?  If so perhaps those issues need to be properly addressed first.

3.  Is there improper use or maintenance of pipe hangers that could be contributing to the problem?

Some alignment equipment offers an solution that is a compromise; perhaps the angular is good but the offset is out of spec.  I think Ludeca calls the feature "optimize" alignment or something similar. 

I prefer to neck down the hold down bolts over slotting the equipment. I worked at a chemical plant that had all of the pump base plates built at a local fab shop and nearly every pump was bolt bound to some extent. We necked down bolts on a ton of motors and never had an issue. On a few of the grossly bolt bound motors we used a tapered ream to oversize the motor holes and use belleville spring washers on the hold down bolts. If pipe stress wasn't an issue on many pumps we could move the drive end of the pump (angle the pump on the baseplate) .010-.020 to get us within spec on the motor alignment. Often have to be creative to solve those issues.

I have found that drilling out, or slotting the mounting base is more effective in the long run.  So the same problem does not occur when the motor is replaced.  If the mounting bolts are threaded into the base instead of through bolts, then as Big J said.  necking down the bolts, or buying shouldered bolts is what I often did.

If you modify the motor feet, then this needs to be done every time the motor is replaced.

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