Tuthill KINNEY KC Series, Operator'S Manual, Page: 9 / 48

3
01
Introduction
Manual 1807 Rev B p/n 001807 0000
Figure 1-1 – Pump Operating Cycle
Sealing and Lubrication
The cylinder walls, pistons, and slide pins are
lubricated and sealed against the backflow of
gas by a film of oil, which fills the close running
clearances. When operating, the cylindrical part
of the piston almost touches the pump cylinder
at a line along the length of the piston. At this
moving line, an effective wave of oil is pushed
ahead of the piston. The oil forms a vacuum tight
seal between the piston and the cylinder, as well
as between all other working components. The
same oil also supplies all required lubrication.
The oil flows through the pump by means of
differential pressure. Because of high pressure at
the discharge and low pressure at the inlet of each
stage, the oil is forced from both oil reservoirs (one
at the discharge of each stage), through internal
cored passageways leading to each pumping
stage. The oil from the backing stage reservoir
lubricates and seals the backing stage, whereas
the oil from the high vacuum stage reservoir
lubricates and seals the high vacuum stage. At the
end of the compression stroke, the oil is forced
out with the discharged gas and returns to the
respective oil reservoir.
Oil Types
The ability of each KC pump to obtain and hold
pressures in the low micron range depends partly
on the use of the proper sealing and lubricating
oil. The AX Vacuum Oil recommended for use with
these pumps is a dry, low-vapor pressure fluid with
suitable viscosity. Such oil is necessary for a high
pumping speed at low pressure.
It may be necessary to use other fluids for special
applications. If varnishing is a concern, high-
detergent oils may be used. If low-temperature
starting is required, other more suitable fluid may
be used. Tuthill Vacuum & Blower Systems can
recommend fluids to fit most special applications.