Buffer Air System, Functional Description - Sullair DR13 125H Operator's Manual And Parts List

Section 4
COMPRESSOR SYSTEMS
equal to approximately 45 psig (3.1 bar). An inte-
gral bypass valve maintains the set flow, while pro-
tecting the pump against undesirable overpressur-
es. A thermal mixing valve, set to open at 85˚F
(30˚C) ensures fast oil warm---up by bypassing oil
around the heat exchanger.
The lube oil is sequentially pumped through a heat
exchanger, the first and second stage compressor
cooling jackets, a high efficiency, replaceable ele-
ment filter, and a multiport manifold, where the fil-
tered outflow is distributed to bearing and gear lu-
brication points on the compressor and the gear
box. Filtered oil is also used to actuate the hydro
actuator linked to the inlet control valve.
The Supervisor II senses and displays the filter out-
let pressure and temperature. As a safety mea-
sure, unless oil pressure builds up to 25 psig (1.7
bar) within 10 seconds after startup, the Supervisor
II shuts down the unit. In addition, if the pressure
drop across the filter ports exceeds 10 psig (6.9
bar), the Supervisor II displays a maintenance re-
quirement message.
14
All lubed points return the oil to the sump by gravity.
Vents on the compressor timing gear covers and
the gear box are also piped into the sump, to avoid
releasing oil vapor. The sump is vented to atmo-
sphere via a breather which includes an oil vapor
trap.
4.8 BUFFER AIR SYSTEM, FUNCTIONAL DE-
SCRIPTION
A small supply of cooled, compressed air is taken
at the aftercooler moisture separator, and used to
feed the buffer air system. This compressed air
goes through a control air filter, and then through a
pressure regulator, where the pressure is reduced
from the compressor operating pressure to 12 psig
(0.08 bar) (read from locally---mounted pressure
gauge). This clean, compressed air supply is fed to
both first and second compression stages. This air
provides a positive pressure buffer to the seals be-
tween the compression air and oil sides of the
stages, assuring oil---free air. The buffer air is then
drained from the stages, manifolded together, and
piped to the exterior of the package.