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3.2.2 Refrigerant circuit
The reciprocating compressor sucks the refrigerant vapours from the evaporator
through the suction filter. The heat is removed from the compressed gas, con-
densed and chilled in the condenser by emitting the heat absorbed in both the
evaporator and compressor. The liquid coolant now being under condensing
pressure is relieved to evaporating pressure and is injected into the evaporator.
Evaporation and a slight overheating of the refrigerant occur in the evaporator,
and also heat absorption from the secondary refrigerant so that the latter is
cooled down to setpoint temperature. The small quantities of oil supplied to the
coolant circuit by the low oil dip from the reciprocating compressor is collected in
the evaporator and returned to the compressor by means of an oil return system.
3.2.3 Oil circuit
During the compressing process, the compressor is supplied with refrigerating
machine oil for lubrication and control.
3.2.3.1 Oil heater
The oil heater in the compressor housing is to be started when the plant is shut
down in order to ensure a minimum oil temperature and sufficient oil viscosity
required for restarting the chiller. The oil heating is not regulated. The maximum
oil temperature is restricted.
3.2.3.2 Oil cooling
Before it is returned to the compressor for use, the oil heated up in the compres-
sor has to be cooled down to a temperature at which it has sufficient viscosity.
3.2.3.3 Oil filter
After cooling, the oil passes into the oil filter which holds back solid particles from
the full oil flow.
Due to its large surface, the oil filter has a high absorbing capacity and thus a
long operating lifetime. The filter has a relative filter fineness of 25 µm.
3.2.3.4 Oil return from the low pressure side
In spite of the low oil carry over of the Grasso reciprocating compressor, oil will
always reach other parts of the plant. For returning the oil from the liquid separa-
tor, the product is equipped with a special automatic oil return system. The auto-
matic oil return system works with a draining vessel and five solenoid valves as
standard.
1.
Filling the draining vessel (2300)
A refrigerant/oil mixture is drained from the evaporator and led to the draining
tank. To this end, a solenoid valve (2305) is opened.
2. Evaporation of refrigerant
The solenoid valve (2305) is closing. Perhaps existing liquid refrigerant can
evaporate in the drainer by heating with pressurized gas. The evaporation
time is restricted by the control and the temperature monitored.
Description
Functional description
L_151511_2
52 19.12.2019