SOFT FOOT

Soft foot condition when one or more foot is short or is in angular. Simply stated, soft foot is when one or more feet do not rest in a common plane.

If soft foot is not corrected, as hold down bolts are tightened, the motor can move in unintended ways, changing the shaft alignment, and possibly causing distortion of the motor frame. Ignoring soft foot can make alignments less accurate, less repeatable, and take more time than needed. Soft foot can also be a contributor to electrical and mechanical problems in machines. In most cases, soft foot is thought of as an alignment problem. But soft foot issues in stationary machines can cause some serious problems as well.

• Pumps – A soft foot condition in a pump can cause the pump casing to distort as the pump hold down bolts are being tightened. Many mechanics have witness this occur when a pump turns freely on a work bench, but binds when bolted down. It can cause a rub in the impellor, and can internally misalign the bearings and seal(s).
• Gearboxes – Case distortion caused by soft foot can change the gear tooth clearances, internally misaligning shaft bearings.
• Reciprocating compressors – If the crankcases are not flat, the bearings can bind, connecting rods can drag, and valves can stick.

Common types of soft foot problems 

Rocking Soft foot: When diagonally opposite soft values are on higher side and one of the foot is short and if the technician keep tightening it start bending and after a while this will lead to distortion of the base.

Angled Soft foot: Bent feet or angled feet can be due to the deflected base. Feet that are not parallel to the surface will stress the machine when tightened down.To correct, re-machine the feet, base or both. Step-shimming is also an acceptable solution when pressed for time.

Squishy: Dirt and grease can cause as squishy feet,  shims more than five can be considered too many shims, rusted shims etc..

Induced Soft Foot: Occurs when stress-induced external forces such as pipe strain, electrical connections, or severe misalignment combined with a stiff coupling pull or push on the machine creating a distortion of the frame.

The precise alignment of rotating machinery is affected by many factors and components. From the very foundation the equipment is mounted upon to the equipment itself and extending to anything connected to the machine. Because of the tightness of the tolerances that are aimed for during these alignments, it takes little to put stress on a machine.

ROTOR Scope 

Laser alignment Services and soft foot correction

Product sales and services

Training.