A reefer container is an enclosed unit used for transporting temperature sensitive cargo. The container requires external power supply for its operation. The article describes everything you ever wanted to know about container refrigeration units.
When reefer containers are loaded in ships, the power supply is provided from the power generated from the D.G sets of the vessel. Some important points about container refrigeration are:
- Container Refrigeration unit is fitted in front of the container and it serves as container front wall.
- Some units are dual voltage, designed to operate on 190/230 or 380/460 volts A.C, 3 phase, 50-60 hertz power.
- Operating control power is provided by single phase transformer which steps down the A.C supply power source to 24 volts, 1 phase control power.
Understanding the Basic Sections of Refer Unit
1. Compressor Section
- Consist of compressor (with H.P switch) and power cable storage compartment. Power transformer may be an option where the ship supply differs.
- It also contain modulating and suction solenoid valve (for controlling the quantity of gas flow).
- Safety fittings in the section are- moisture liquid indicator, pressure relief valve, filter drier etc.
- Safety of the system is further enhanced by electronic monitoring with the help of following sensors- Compressor suction and discharge sensor, supply air temperature sensor, supply recorder sensor, ambient sensor.
2. Condenser Section
- The condenser section contains condenser fan and its motor, an air cooled condenser coil and condenser saturation sensor.
- For air cooled condenser air is normally pulled from bottom and discharged horizontally through centre of the unit.
- Some units consists of water cooled condenser /receiver. This unit is expensive.
- This section contains temperature sensing bulb, return recorder bulb sensor and a thermostatic expansion valve (for flow of refrigerant and maintenance of inside temperature).
- Assembly consist of evaporator coil and heater, drain pan and heater, defrost and heat transmission switches.
- The evaporator fan circulates air throughout the container by pulling air in top of refrigeration unit and directing air through evaporator coil where it’s either heated or cooled and is then discharged out at the bottom of refrigeration unit into the container.
4. Fresh air Make up Vent
- Purpose of this vent is to provide ventilation for commodities that requires fresh air circulation and must be closed when transporting frozen foods.
- Air exchange depends upon static pressure differential which will vary depending upon how container is loaded.
Safety and Operating Precaution
An injury, no matter how small, should never go unattended. Always obtain first aid or medical attention immediately.
a) Always wear safety gloves and glasses while working on any unit and also when charging refrigerant.
b) Keep hand, tools, and clothing clear from evaporator and condenser fan.
c) No work should be performed on any unit until all circuit breaker and start stop switches are turned off and power supply disconnected.
d) Do not bypass any electrical safety device.
e) When performing arc welding on unit or condenser, disconnect all wire harness connection from the module in control box. Do Not remove wire harness from the module unless you are grounded to unit frame with a static safe wrist strap.
f) In case of electrical fire, open circuit switch and extinguish it with CO2 extinguisher.