Atlas Copco GA 55+, Instruction Book

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92
Instruction book
9096 3313 00
The oil cooler bypass valve (BV1) starts closing the bypass line and opening the oil supply line from the main oil
cooler (Co) at the lower limit of its temperature range. At the upper limit of its temperature range, the
bypass line is completely closed and all the oil flows through the main oil cooler.
BV1 must have a higher opening temperature (set point) than BV2 in order to prevent the heat from being
dissipated in the compressor oil cooler (Co) before the warm oil is fed to the oil/water heat exchanger when using
the compression heat as source for energy recovery. Thermostat BV1 starts to open at 75 °C and is completely
open at 90 °C.
Energy recovery system in use (see drawing)
The handle (V1) of BV2 (bypass valve of the HE) is totally turned in clockwise.
•
Compressor start-up
When the compressor is started up from cold, the oil temperature will be low. Bypass valve (BV2) shuts off the
oil supply from the heat exchanger (HE) and bypass valve (BV1) shuts off the oil supply from the oil cooler
(Co) to prevent the compressor oil from being cooled. The oil flows from the oil separator vessel (AR) through
the oil filter(s) (OF) back to compressor element (E).
All energy input is used to rapidly warm up the compressor oil. No energy is recovered.
•
Maximum energy recovery
As soon the oil temperature reaches the set point (opening temperature) of bypass valve (BV2), the valve
starts closing off the bypass over the heat exchanger (HE) oil line, while gradually allowing the oil to flow
through the heat exchanger (HE). As the oil temperature rises to approx. 15 °C above the set point, all the oil
passes through the heat exchanger. The exchange of heat between the compressor oil and the heat
recovery water is maximum. The oil from the heat exchanger outlet flows via oil filter (OF), oil stop valve
(Vs - if present), compressor element (E) and separator (AR) back to the inlet of heat exchanger (HE). Bypass
valve (BV1) bypasses the oil cooler (Co) as long as the oil temperature remains below its set point.
Operation principle at different loads:
•
Low consumption of recovered energy
Attention: It is only allowed to turn the handle completely in or out. No in-between position
is allowed!