Efficient Plant January 2018 - 36
Always use new, clean shims. Dirt, debris, bent shims, and inconsistent
thickness can lead to problems.
Always use new, clean shims. The cost of new stock is minimal
when compared to the cost of extra downtime caused by an
inefficient precision-alignment process.
Improper storage and re-use of old shim stock can contribute to
soft foot. Dirt, debris, bent shims, and inconsistent thickness of
cheap carbon-steel shims can drive up costs from lost time.
Shims for a given alignment should be of the correct size and
the same size. They should be made of stainless steel, a material
that can withstand the compression created by a machine's mass
and clamping force of hold-down bolts. Never combine multiple
shim sizes or materials in the same stack.
When selecting the shim size (A, B, C, or D, for example),
choose that which offers the most contact between the foot and
base and has the proper slot size for clearance around the holddown bolts of the movable machine.
Be mindful of the position of shim stacks in relation to holddown bolts. Maintain clearance between the shim and bolt to
prevent damage to the stack (bent shim) or bolt threads. A bent
shim can induce soft foot where soft foot doesn't actually exist.
Choose, Use, Store
SHIMS ARE CRUCIAL in efficiently achieving precision shaft alignment. Proper choice, use, and storage of these items are key. Tom Shelton
of VibrAlign (vibralign.com, Richmond, VA) provided some important
tips in a recent post on the company's blog.
- Jane Alexander, Managing Editor
Tom Shelton is a trainer for VibrAlign (vibralign.com, Richmond, VA). For
more insight from Shelton and other VibrAlign experts on a wide range of timely
topics, visit vibralign.com/blog.
ON A RELATED NOTE:
HANDLE ALIGNMENT TOOLS WITH CARE
Although precision measuring equipment is typically made for
industrial settings, it should be handled with care. Important rules to
keep in mind:
Keep precision tools in their original cases. Environmental
effects from improper long-term storage can be detrimental to
Don't overlook routine maintenance. Calibration should be
performed annually or, at a minimum, every other year.
Casually throwing dial indicator sets into a box or drawer can
damage mounting brackets and cause hysteresis (internal
friction) in the indicators.
Regarding laser shaft-alignment systems, remember that dirty
sensors (laser and detector lens) can lead to non-repeatable
measurement results. All system components should be stored
properly in the carrying case to protect them from damage. EP