Allowable ANSI pump foundation tilt

[icmvgd]

Hello, I have a somewhat unusual situation with a centrifugal pump and was looking for advice or best practices on allowable base tilt. I have a pump/motor foundation that has been subsiding on the pump end and causing the whole foundation/baseplate to tilt. Due to the constricted area, excavating the area and re-leveling the foundation would be difficult. The measured tilt is 2.65 degrees, is this enough to cause problems with the long-term reliability of the pump?

 

[TenPenny]

I think the issue would be the pipe strain on the casing.
Obviously, if the tilt is enough that it causes issues with getting the bearings lubricated, that would be bad as well, but I would not expect 2.6 deg to cause any problems other than the pipe strain.

 

[LittleInch]

Can't you just pack up the base plate with a LOT of grout?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[mk3223]

Need to verify the root cause of the sunk foundation either caused by the soil condition or the construction error. It can be a real problem if it's an issue caused by the "soft" soil condition.

 

[pumpingtips]

Running the pump at this slight angle will not cause any problems. Pumps are designed to handle axial forces. And guessing that the subsidence should cease after a while.

 

[electricpete]

looking for advice or best practices on allowable base tilt

Here's one reference:

The equipment baseplate mounting surfaces are to be leveled longitudinally and transversely to within 200 micrometers per meter (0.002 inches per foot) for API 610 pumps and to within 400 micrometers per meter (0.005 inches per foot) for general purpose equipment and ASME pumps

...at least that's what shows up in the 1996 edition, which is the latest that I have.
Of course you can do the conversion on the higher number:
400um/m = 0.0004 radians.
0.0004 radians * 180degrees/(pi*radians) = 0.02 degrees (!)
You asked for a best practice. This qualifies as a best practice. Beyond that may be ok, but it's tougher to know.

if the tilt is enough that it causes issues with getting the bearings lubricated...

I agree this is an important issue to look at. Oil ring behavior may be affected. Oiler level control may be affected. I wouldn't accept it lightly.


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(2B)+(2B)' ?

 

[nondimensional]

If piping does not move because of good harnessing, then the pump nozzle will see excessive moments. This will cause shaft deflection in excess of 0.002 in and potentially destroy mechanical seals - repeatedly. Based on pump size and type, it can cause high stresses in casing/discharge head and potential stress cracks in casing.

I second the idea of 2 mils per foot leveling or better.