Center of Gravity of an equipment 1

[StrP88]

I am in need of any non destructive way to find CG of a heavy equipment/machine (23 kips weight labeled on).

It is an old machine (pump) foot print 20' by 5.5 '
No drawings are available

What do we do typically in these cases?
Need to know CG for lifting purposes

 

[SLTA]

For lifting purposes, I'd attach straps all over the sucker and not worry about calculating anything. Create a sling for it.

Please remember: we're not all guys!

 

[MotorCity]

My first thought would be to contact the manufacturer, but because its an old pump the manufacturer may or may not still be in business. Unfortunately, even if you could contact the manufacturer, most of my requests for such information has been met with the "deer in headlights" look by the equipment rep.

Next I would probably guess where the heaviest end is based on the diagram or parts list. For example, the motor end is probably heavier than the shaft end....and adjust my guess conservatively.

Worst case, you could assume that the entire load is concentrated in the worst possible location for lifting (such as all at one end, all at the top, etc). But I would avoid doing this if possible because unless its a really small lift you are probably penalizing the rigging/lifting system.

Another solution may be trial and error. Work with the lifting contractor and maybe try lifting the pump 2" off the ground to see how it wants to react, how the weight shifts.....obviously observing from a safe distance and lifting slowly

 

[Lomarandil]

MotorCity is on the right track... come up with a reasonable first guess, then do some trial and error lifts with an adjustable spreader beam and a bunch of extra capacity in your rigging and chart.

Presuming you need to be able to control the orientation of the part when lifted.

If not, rig to it in several places with rolling blocks (again, with a bunch of extra capacity in the rigging), and let the CG find itself.

 

[JStephen]

If you will keep it vertical in lifting, can you pick it up or jack it up slightly, put a round pipe or bar under it, then roll it this way and that to determine the balance point? This assumes you don't need the vertical COG, just lateral. Do it in two different directions for X and Y.

 

[robyengIT]

You can also lift the equipment with four adjustable chains and adjust them one by one

 

[dhengr]

StrP88:
Where are the lifting points on the pump system? I would hope you are not having to guess or arbitrarily pick these points, without knowing their strength. About 23k, you say, and 20' x 5.5' in plan; is this entire pump system on a skid which supports the whole thing? Or, does it come apart to be lifted in several smaller pieces. Look at the lifting points, lifting lugs, lifting eyes, for size and location. They should give some hint of their cap’y. by back calculating, and the center of their plan locations might indicate an approx. c.g. in plan. I think MotorCity and Jstephen have about the right ideas of going about this lift. However many slings are needed, based on number of lifting points, make sure that half the slings will carry the full load. Depending upon existing conditions, you don’t always have to lift right above the c.g., the piece will tilt a bit and align the c.g. with the hook above, as long as this doesn’t become a stability problem.

 

[racookpe1978]

"If" this is actually a simple pump + motor + baseplate assembly - and that is a big "if" assumptions, then get the physical size and onstruction of the baseplate. How is made, what thickness plates, what dimensions (length + height + web and flange thickness) of the C-channels underneath, how long are any ribs or reinforcements or tie-down plates.

Find out the size of the motor and designation of the motor, then look at a comparable modern motor + pump combination from the Gould catalog: 1000 HP TEFC for example. or 200 HP TEFC. Or what ever.

Pump weight: Same thing, get an approximate modern weight and CG from the comparable pump.

Skip seals and coupling, they won't be much if the piping is removed. If the pipes are still attached, estimate their weight by length, fitting type, and wall thickness.

Then combine the four CG's. Compare to the location of the rigging mounts as mentioned above. I don't recommend anything with motion on an uncontrolled, unknown weight assembly such as rolling the assembly. Sling with 4x over-sized chainfalls and an oversized crane capacity and conservative reach. Once the crane has the load suspended a few inches up, it's operator will give you the total rigging + pump weight.