In many cases , we are handed over the equipment (driver and driven) by the erection agency in the condition that motor is high and there is no shim, below the motor. Shimming under the driven equipment causes suction and discharge flanges bolt holes to go out. We are grinding the motor base pads to bring the motor down but it is a lengthy and rough method. What you people do in such cases?
Regards
Irshad Akhtar

Generally one provides specifications on the frontend to have the driven setting 0.125" high as a minimum - some use 0.250"

Then during construction; use inspectors to ensure compliance.

After the fact: raise the driven as a normal correction factor due to future considerations of subsidence.

quote:

Shimming under the driven equipment causes suction and discharge flanges bolt holes to go out. We are grinding the motor base pads to bring the motor down but it is a lengthy and rough method. What you people do in such cases?

Grinding the base of the motor is only asking for trouble next time the motor has to be changed, which might be in the middle of the night on a Saturday and there you go, problems. Sam is correct, raise the driven.

Adjust the piping to match the new height of the driven and you are good to go.

Ahktar, Where the height is small, maybe a max of 0.5mm and conditions permit, I've raised the NDE of the driver to bring the parallel misalignment at the coupling to within limits. The remaining misalignment is then angular. If it is withing limits, it is acceptable but not ideal. If not, it is better to have the bedplate machined. We have also raised the driven. It boils down to the best compromise to suit the conditions.
Best regards,
Joe Mc Cormack

Hand grinding anything to do with alignment, expecially the base pads, are a terrible way to achieve alignment. Unless you are using a portable milling machine the pads will all be at different levels, and the angle on all of them will be different. . You'll have to build 4 wedges of shims, and will be a nightmare.
Raise the pump.

Dave

How many pumps are there?
Sounds like the outfit that did the installation are amateurs and should be held responsible for correcting their bad installation. I expect they have been thrown off the job for all their other mistakes, and litigation has begun, so the best you'll get is adding back charges for repairing their foul up. They will try to hide behind a lack on installation specification, but practically every pump manufacturer and many municipalities and codes amd MIL specs spell out (just as others have said) that the motor should be set with at least 1/8 inch shims under the feet.

Are the pump and motor on an inertia block on isolation mounts?
When you attempt to move pumps higher you may find that the piping strain is already excessive.

Dan said it well! If they screwed up and made major mistakes - why would you think they got the piping right? Pipe hangers and supports. Hey, anything to help!!

I see this fairly often. Usually the job is long finished before the problem is discovered, usually the first time the motor has to be replaced and realigned. In an ideal world, Dan & Sam would be right....make the installer correct the problem. But again, usually this is not going to happen.

As Joe Mc says, the problem might not be as bad as you think. If you are just using a laser and it gives you the 'ideal' moves (which you can't achieve), the problem might not be as bad as you think. Plot the actual shaft centerlines, and from the plot, determine the best achievable alignment, given the current conditions. It may actually be within limits, or the angular may be a little out of spec but might not be a problem depending on the type of coupling. Falk grid couplings will accommodate a lot of angular misalignment for example (but the grid will wear faster...you have to inspect the coupling on a regular schedule). The Woods-style "toothed" elastomer insert will also handle a fair amount of angular.

In general, if the coupling hubs are not "physically connected" they will accommodate a fair amount of angular misalignment. Examples of those which will NOT -- in spite of being elastomeric and considered "soft" -- are the Omega "orange peel" coupling and the black "donut" couplings. They are actually quite stiff axially, and often misapplied.

Rusty,

I cover one fan that goes through bearings at an alarming rate and I think it is due to the axial stiffness of the Omega coupling. They were going through bearings as fast as every 2 weeks, but I have been able to baby the latest set along for almost a year now. Wrong bearing, wrong lube, wrong coupling, imo.

Ahktar,

Unfortunately, there are no really good options here. Add it all up and pick the one that makes sense. Get the money back if you can, but don't let the inability to recoup your losses cause you further costs and inconvenience.

I agree with Dave that hand grinding anything will only make a mess of it.

Having said that there are companies that do in place machining that do a fine job and can machine down the motor mounts with extreme precision. Probably better than they were originally... and get you to an elevation that works for you...

Akhtar, this problem occurs when EPC contractor purchases motor seperately and pump testing carried out without using "job motor." API 610 has guidelines for minimum thickness, max. thickness and number of shims. As mentioned by fellow members hand grinding is very tedious job. for few ocasions (smaller motors) we had done that but it took more than a week and not very good result. In situ milling was performed for most of the cases with great success. This exercise is also required sometimes because base frame gets distorted during transportation or installation.

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