Page 253 - Reciprocating Compressors Operation Maintenance

238 Reciprocating Compressors: Operation and Maintenance

within a system. In addition, maintenance procedures and repair meth-
ods, such as grouting, can be evaluated.

In order to interpret the readings, some experience and sound thinking
are required, but the effort will be worth it. Because problems with the
lower end of the machine are never the same, the best way to deal with
instructions on analyzing the data is to examine several hypothetical
cases. The reader can better follow the examples and subsequent prob-
lems by using a model crankshaft made from wire or a paper clip.
The readings listed in the table of Figure 4-7 will be used as Case 1
and were obtained from a machine with a 22-in. stroke. The compressor
builder assigned a maximum deflection figure of .004 in. The -.005 at
the 180° position for No. 3 throw is above the specified limit, indicating
that something is wrong. The 90° and 270° positions are normally used
to determine whether the main bearings are out of alignment in a hori-

Throw
Crank
Position
1 2 3 4 5 6

"Down Position"
0° 000 000 000 000 000 000

90° 000 .00025 -.001 000 000 -.0005

180° 000 -.001 -.005 -.002 -.00025 -.001

270° 000 000 -.001 -.00025 000 -.00025

FIGURE 4-7. Example web deflection readings. (Source: Block, H. P. and
Geitner, F. K. Major Process Equipment Maintenance and Repair, Houston, TX,
Gulf Publishing Company, 1985)