Page 199 - Reciprocating Compressors Operation Maintenance

Operation and Maintenance of Reciprocating Compressors 185

packing, break-in time could be between six and eight hours with no
load. Frequently, a load is applied to the machine as soon as it is
warmed up. This is extremely harmful to the new packing and could
result in catastrophic or premature failure.
5. Prelube. The packing box should be properly lubricated prior to
starting. Refer to the instructions for maintenance and servicing of
packing.
6. Packing box lubrication. Lubrication is extremely important for
some types of packing. Metallic packing and Micarta packing
require lubrication. However, engineered plastics, such as Teflon
and Ryton have natural lubricity. Depending on the packing, the rate
of oil flow must be adjusted accordingly. Adjustment procedures
vary depending on the lubricator. Again, too much oil can be as bad
as not enough oil.
7. Paniculate matter. Trapped matter may be carried with the gas into
the cylinder. It could settle on the piston rod and be carried back
into the packing rings where it could mix with the oil to form an
abrasive slurry.
TAPERED PISTON RODS

Because lubricating oil films may tend to fill up some small passages,
packing can usually function in the presence of slight piston rod taper.
Generally, tapered conditions are found at either end of the stroke, while
the in-between portion of the rod may remain unaffected. Excessive
amounts of taper will destroy the seal in the following manner.
When the rings are riding on the tapered part (see Figure 3-45), one
edge of the ring bore is in contact, while the other edge is away from the

PASSAGE

FIGURE 3-45. Effect of tapered rod contours on packing ring sealing function
(Source: C. Lee Cook, Louisville, Kentucky}.