Construction and Working of Ships
Refrigeration plant
Main Components of
Refrigeration plants
Any
refrigeration unit works with different components inline to each other in series.
The main components are:
1. Compressor:
Reciprocating single or two stage compressor is
commonly used for compressing and supplying the refrigerant to the system.
2. Condenser: Shell and tube type
condenser is used
to cool down the refrigerant in the system.
3. Receiver: The
cooled refrigerant is
supplied to the receiver, which is also used to drain out the refrigerant from
the system for maintenance purpose.
4. Drier: The drier
connected in the system consists of silica gel to remove any moisture from the
refrigerant
5. Solenoids:
Different solenoid valves are used to control the flow of refrigerant into the
hold or room. Master solenoid is provided in the main line and other solenoid
is present in all individual cargo hold or rooms.
6. Expansion valve: An
Expansion valve regulates the refrigerants to maintain the correct hold or room
temperature.
7. Evaporator unit: The
evaporator unit act as a heat exchanger to cool
down the hold or room area by transferring heat to the refrigerant.
8. Control unit: The
control unit consist of different safety and operating circuits for safe operation
of the refer plant
.
Working of Ship’s Refrigeration Plant
The compressor acting
as a circulation pump for refrigerant has two safety cut-outs- Low pressure
(LP) and High Pressure (HP) cut outs. When the pressure on the suction side
drops below the set valve, the control unit stops the compressor and when the
pressure on the discharge side shoots up, the compressor trips.
LP or
low pressure cut out is controlled automatically i.e. when the suction pressure
drops, the compressor stops and when the suction pressure rises again, the
control system starts the compressor. HP or high pressure cut out is provided
with manually re-set
The hot
compressed liquid is passed to a receiver through a condenser to cool it down.
The receiver can be used to collect the refrigerant when any major repair work
has to be performed.
The
master solenoid is fitted after the receiver, which is controlled by the
control unit. In case of sudden stoppage of compressor, the master solenoid
also closes, avoiding the flooding of evaporator with refrigerant liquid.
The room
or hold solenoid and thermostatic valve regulate the flow of the refrigerant in
to the room to maintain the temperature of the room. For this, the expansion
valve is controlled by a diaphragm movement due to the pressure variation which
is operated by the bulb sensor filled with expandable fluid fitted at the
evaporator outlet.
The thermostatic expansion valve supplies the correct amount of
refrigerants to evaporators where
the refrigerants takes up the heat from the room and boils off into vapours
resulting in temperature drop for that room.
This is
how temperature is maintained in the refrigeration plant of the ship.
he temperature of
different provision rooms carrying food stuffs for crew members.
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