Page 192 - Machinery Component Maintenance

174 Machinery Component Maintenance and Repair

piece dimensions, measure flange gap around circumfer-
ence, then calculate as follows:
I Flange O.D. I=
Gasket 0. D .
l/8 in. + (Max. Gap - Min. Gap)

Maximum Thickness of
Tapered Filler Piece

1/8 in. = Dutchman Minimum Thickness (180’ from
Maximum Thickness). Dutchman OD and ID same as gas-
ket OD and ID.
Spiral wound gaskets may be helpful, in addition to or in-
stead of a tapered filler piece. Excessive parallel offset at
the machine flange connection cannot be cured with a
filler piece. It may be possible to absorb it by offsetting
several successive joints slightly, taking advantage of
clearance between flange bolts and their holes. If exces-
sive offset remains, the piping should be bent to achieve
better fit. For the “stationary” machine element, the pip-
ing may be connected either before or after the alignment
is done-provided the foregoing precautions are taken,
and final alignment remains within acceptable tolerances.
In some cases, pipe expansion or movement may cause
machine movement leading to misalignment and increased
vibration. Better pipe supports or stabilizers may be
needed in such situations. At times it may be necessary to
adjust these components with the machine running, thus
aligning the machine to get minimum vibration. Some-
times, changing to a more tolerant type of coupling, such
as elastomeric, may help.

Coupling Some authorities recommend installation on typical pumps
Installation and drivers with an interference fit, up to .OW5 in. per in.
of shaft diameter. In our experience, this can give prob-
lems in subsequent removal or axial adjustment. If an in-
terference fit is to be used, we prefer a light one-say
.OOO3 in. to .OOO5 in. overall, regardless of diameter. For
the majority of machines operating at 3600 RPM and be-
low, you can install couplings with .0005 in. overall
diametral clearance, using a setscrew over the keyway. For
hydraulic dilation couplings and other nonpump or special
categories, see manufacturers’ recommendations or appro-