System Layout - Emerson Copeland Screw SCH2 Applications Manual

4.2 System layout

4.2 System layout
4.2 System layout 4.2 System layout 4.2 System layout
The compressor is installed in the refrigerating circuit
similar to semi-hermetic reciprocating compressors.
Plant design and pipe layout Plant design and pipe layout Plant design and pipe layout Plant design and pipe layout Plant design and pipe layout
The pipelines and the system layout must be arranged
so that the compressor cannot be flooded with oil or
liquid refrigerant during shutdown.
Suitable measures are (also as a simple protection
against liquid slugging during start)
• either to raise the suction line after the evaporator
(goose neck)
• or to install the compressor above the evaporator.
Additional safety is provided by a solenoid valve
installed directly before the expansion valve. In addition
the discharge line should first be angled downwards
after the shut-off valve.
Due to the low level of vibration and discharge gas
pulsation the suction and discharge lines can be made
without the use of flexible elements or mufflers.
However, pipelines must be sufficiently flexible and
supported to not exert any strain on the compressor.
The most favorable pipe runs are designed parallel to
the compressor axis and the discharge line first
leading downwards. The distance to the axis should be
as short as possible and the parallel pipe section
should be at least half the compressor's length.
Finally, long radius elbows should be used.
Due to gas pulsations there can be vibrations espe-
cially in discharge and economizer lines. Therefore
critical pipe lengths (+/- 15%) with their natural fre-
quencies being in resonance with the compressor
pulsations must be avoided.
Among other things the operating conditions and the
refrigerant (sonic speed) as well as the compressor's
pulsation frequency must be considered in the calcula-
tion.
The base frequency of the compressor is approx.
250Hz (50Hz network) or 300 Hz (60 Hz network).
Frequencies of higher orders (500 / 1000 Hz or 600 /
1200 Hz) should also reviewed at in the final layout.
© 2002 Copeland Corporation
Issued 4-2002
Printed in U.S.A.
Oil heater Oil heater Oil heater Oil heater Oil heater
An oil heater is provided to prevent too high a concen-
tration of refrigerant in the oil during shutdown. It is
mounted in a heater sleeve and can be replaced if
necessary without accessing the refrigerating circuit.
For electrical connection see section 6.4.
Typical system design
Additional insulation of the oil separator Additional insulation of the oil separator Additional insulation of the oil separator Additional insulation of the oil separator Additional insulation of the oil separator
Operation at low ambient temperatures or at high
temperatures on the discharge side during standstill
(such as heat pumps) requires additional insulation of
the oil separator.
Filter drier Filter drier Filter drier Filter drier Filter drier
Generously sized filter driers of suitable quality should
be used to ensure a high degree of dehydration and to
maintain the chemical stability of the system.
Suction side cleaning filter Suction side cleaning filter Suction side cleaning filter Suction side cleaning filter Suction side cleaning filter
The use of a suction side filter (filter mesh 25 m) will
protect the compressor from damage due to dirt from
the system and is strongly recommended for site built
systems.
8
AE4-1322
Figure 6