13
Instruction Manual
2.5 AIR FLOW (SEE FIG. 2.3)
Air drawn through the air filters (AF) into the LP compressor
element (CEL) is compressed. The air then enters the HP compressor
element (CEH) where it is further compressed. At the element outlet,
compressed air and oil pass into the air receiver/oil separator (AR/
OS).
The check valve (CV) prevents blow-back of compressed air when
the compressor is stopped. In the air receiver/oil separator (AR/OS),
most of the oil is removed from the air/oil mixture; the remaining oil
is removed by the separator element.
The oil collects in the receiver and on the bottom of the separator
element.
The air leaves the receiver via a minimum pressure valve (MPV)
which prevents the receiver pressure from dropping below the
minimum working pressure (specified in section 8.3), even when the
air outlet valve is open. This ensures adequate oil injection and
prevents oil consumption.
Two temperature switches (TS
1
and TS
2
) are comprised in the
system.
A blow-down valve (BDV) automatically depressurizes the air
receiver (AR) when the compressor is stopped.
2.6 OIL SYSTEM (SEE FIG. 2.3)
The lower part of the air receiver (AR) serves as oil tank.
Air pressure forces the oil from the air receiver/oil separator (AR/
OS) through the oil filters (OF) and oil stop valve (OSV) to the
compressor element.
The thermostatic by-pass valve (TBV) opens when the oil
temperature is above 70 °C. Then the oil flows through the oil cooler
(OC) before it is filtered.
Each compressor element has an oil gallery in the bottom of its
casing. The oil for rotor lubrication, cooling and sealing is injected
through holes in the gallery.
Lubrication of the bearings is ensured by oil injected into the bearing
housings.
The injected oil, mixed with the compressed air, leaves the
compressor element and re-enters the air receiver, where it is
separated from the air as described in section 2.6. The oil that
collects in the bottom of the oil separator element is returned to the
system through scavenging line (SL), which is provided with a flow
restrictor (FR).
The oil filter by-pass valve opens when the pressure drop over the
filter is above normal because of a clogged filter. The oil then by-
passes the filter without being filtered. For this reason, the oil filter
must be replaced at regular intervals (see section 4.1).
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