Page 133 - Reciprocating Compressors Operation Maintenance

1 2O Reciprocating Compressors: Operation and Maintenance

from time to time and examining them and all accessible parts of the
cylinder, valve passages, and discharge pipe. All surfaces should have a
wet appearance and should feel oily to the touch.
If they are dry or show signs of rusting, the rate of oil feed should be
increased. On the other hand, if the parts have excessive oil on them, or
if oil is lying in pools in the cylinders, the rate of oil feed should be
reduced.
In the operation of air compressors, over lubrication of the cylinders
and the subsequent carryover of the excess oil to the downstream piping
system causes excessive deposits and the real possibility of explosion or
fire.
The biggest problem with box lubricator pumps is that they either
pump too much oil, or no oil at all. They are difficult to adjust and main-
tain; they often are driven too fast to deliver the required amount of oil;
and they cannot provide protected delivery. Any pump can stop without
being noticed, causing serious damage to compressor cylinders, packing,
or other components. If very old or subject to dirty oil, the pump piston
can be so badly worn in the pump body that it can no longer reliably
deliver oil. If the rocker arm or cam is badly worn, the pump will not
operate at its maximum stroke. If the adjusting stem is worn, missing, or
not assembled or not located correctly on the rocker arm, the pump will
pump at maximum stroke and its discharge cannot be cut back.
Remember—all pumps need a clean, air-free oil supply.

DIVIDER BLOCK OR FEEDER SYSTEM

Recently, a great many improvements in lube system design have
occurred, primarily in the areas of automatic operation, accuracy of
delivery, and fail-safe protection. The more current type of lube system is
the divider block system.
This system employs one central pump feeding a network of one or
more divider blocks or feeders, which "divide" and "distribute" the
required volumes of oil down the various lube lines. Although some ear-
lier systems still use the "vacuum type" pumps to feed the dividers, most
pumps have what is called "pressurized inlet."
In the divider block system, the drive box of the pump does not con-
tain the oil supply. That drive box oil serves only to lubricate the drive
mechanism. The system oil is supplied directly to the inlet of the pump