Page 129 - Reciprocating Compressors Operation Maintenance

116 Reciprocating Compressors: Operation and Maintenance

DISCHARGE o
CHECK VALVE
PRESSURIZED
SUPPLY ADJUSTMENT

-RESERVOIR
riSlirap^
PISTON
wmm it
c^or,,,^-— -TMC-I^ u ROCKER ARM
SPRING-^ Ifeiytf*——ASSEMBLY

CAM

Pumps WHh Pressurized Supplies
FIGURE 3-4. Force-feed box lubricator with pressurized pumps (Source:
Lubriquip, Inc., Cleveland, Ohio).

Pumps With Pressurized Supplies

Rotation of the lubricator cam actuates the pump rocker arm assembly
to operate the pump piston. On the piston downstroke, spring pressure is
exerted on the piston causing it to follow the cam. As it moves down, a
pressure reduction (vacuum) is created between the piston and the dis-
charge check valve, and the valve closes. This allows the pressurized
supply to unseat the supply inlet shutoff ball and pressurize the piston
bore with lubricant. On the piston upstroke, the piston forces the supply
inlet shutoff ball to seat and shut off the pressurized supply. Lubricant in
the piston cylinder is forced out through the discharge check valve to the
machine injection point. Each pump can be adjusted by means of an
external screw. This changes the length of the pump stroke, which
changes the pump discharge volume.