1. Introduction
The requirements below summarize the most important design and approved specifications for vessels and equipment already in use. These do not alter or change any specifications stipulated by other national or international authorities.
2. Basic Requirements
- All vessels, refrigeration equipment, containers, control, and recording systems must comply with the specifications of a recognized international classification society such as Lloyds.
3. Requirements for Vessels
3.1 Air Distribution Systems
- Temperature Maintenance:
Cold air must be delivered at the specified temperature to each container containing perishable cargo or requiring temperature control. A maximum of ±0.5°C deviation from the specified temperature is permissible in delivery air at the entry port hole of each container. - Air Circulation Rate:
- Chilled produce: 60 complete air changes/hr
- Frozen produce: 30 complete air changes/hr
- Fresh Air Supply:
Must be adjustable from 0% (no intake) to 100% (one complete air renewal every two hours). Fresh air inlet and outlet must not allow any cross-tainting. - Taint Barriers:
Must be in sound condition to avoid cross-tainting between compartments. - Relative Humidity:
Cooling air RH to be maintained at 85 ±5% unless otherwise specified.
3.2 Refrigeration System
- Under tropical conditions (ambient air +40°C, RH 55%, sea water 32°C), the refrigeration plant must maintain all air delivery temperatures within ±0.5°C of the specified temperature in all chilled containers at all times. It must also maintain air return temperatures within ±0.5°C of the specified temperature in all deep freeze containers.
3.2.1 With the whole plant operating, it must:
- Maintain a return air temperature of -20°C in deep freeze containers.
- Cool down the return air from 27°C to -0.5°C in fruit containers shipped at a pulp temperature of -0.5°C within 12 hours after shipment.
3.2.2 With one refrigeration unit as standby:
- Maintain -0.5°C in all fruit containers and -25°C in deep freeze containers.
3.3 Electrical Power Supply
- All vessels carrying integral containers must have sufficient power supply to plug points when carrying integral containers.
- Sufficient spares must also be available onboard, if required.
3.4 Automatic Control System
Control systems must include:
- Brine temperature control
- Liquid expansion to evaporators
- Thermostatic control of delivery air temperature for air coolers and hold conditioners
Brine temperature in the four delivery brine mains is controlled by electronic controllers, which also control compressor capacity. Controllers must cover the range from +20°C to -40°C.
3.5 Instrumentation
- A datalogger must monitor, measure, and record each individual container return air temperature, each air cooler delivery air temperature, temperatures from the refrigerating machinery, and alarms for high/low temperatures, gas pressures, and failures of running compressors and pumps.
- Two typewriters and two alarm print-outs are included.
- A manually operated monitor is required with a sensor in each return air duct to analyze and indicate the CO₂ content.
- Electronic data loggers must be installed on each container vessel. Information must be supplied promptly to the Board.
- All temperatures must be recorded at least every 4 hours until conditions have settled, and every 8 hours thereafter for the remaining duration of the voyage.
- All temperature logs must be returned as soon as possible after being requested by the PPECB.
3.6 Calibration
- All temperature control and recording equipment must be calibrated at 0.0°C at least once every 6 months unless the system is self-calibrating.
3.7 Hold Insulation
- All insulation must be kept clean, dry, and intact at all times. This includes insulation in bulkheads, air ducts, and hatch covers.
3.8 Cleanliness
- All equipment and materials such as cooling coils, ducting, and air intake pipes must be kept clean at all times to avoid micro cross-contamination.
4. Design Requirements for Containers
4.1 Uniformity of Shape
- The internal and external uniform shape of the container must remain as new, without bulges.
4.2 Construction
4.2.1 Floor
- Floor must be T-section construction, minimum height 40mm, able to withstand forklift stresses.
- Space between T-sections not to exceed 50mm at any place.
- Original form and designed load-bearing strength must be maintained at all times.
4.2.2 Door Battens
- 12mm deep battens must be provided on the doors, vertically disposed, pitched at 200mm, stopped not more than 75mm from the top and bottom door seals. Top surface width not less than 25mm.
4.2.3 Door Seals
- Door seals must be intact and provide an airtight seal at all times.
4.2.4 Air Delivery Opening
- Must be 70mm deep for the full internal width of the container. The top edge of the slot must be not more than 100mm above the top surface of the floor, allowing unobstructed airflow.
4.2.5 Air Return Opening
- Should not be less than 70mm deep for the full internal width of the container, allowing unobstructed airflow.
4.2.6 Cargo Loading Protection
- Adequate protection must be provided to the side walls for the full internal length of the container. This protection must not reduce the internal width specified in section 4.1.
4.3 Heat Leakage
- The maximum heat leakage values must not be exceeded at any time. The heat leakage of the roof must be equivalent to 75mm of material with a thermal conductivity not exceeding 0.024 Kcal/m²/h/°C.
| Container Type | Max Heat Leakage (Kcal·h/°C) |
|---|---|
| 20’ fruit container | 40 |
| 20’ reefer container | 23 |
| 20’ “combi” container | 23 |
4.4 Air Leakage
- Maximum air leakage must not exceed 8.5 m³/hr at 25mm swg internal pressure.
4.5 Insulation Integrity
- Insulation must always be dry (no moisture), intact (no separation), and without any holes or cracks. When insulation is bonded to the walls, roof, or floor, such bonding must always retain its integrity.
5. Refrigeration Requirements for Integral Containers
5.1 Refrigeration
- Refrigeration requirements for integral refrigerated containers also apply to the requirements for container vessels as specified in section 3.
5.2 Relative Humidity
- The evaporator surface must give a maximum temperature difference of 5°C between the mean container temperature and the mean evaporating temperature when the cargo is in equilibrium at 0°C and the ambient temperature plus 38°C, to retain a relative humidity between 85% to 95%.
5.3 Defrosting
- Defrosting must be automatic and may be initiated by a differential air pressure switch or a timer switch and must include a manual override switch.
5.4 Minimum Air Circulation Rate
- Minimum rate of air circulation with frost-free coils must be 60 changes per hour of the empty volume of the container against a static pressure difference across the empty container of 30mm swg at sea level and 15°C.
- The fan must circulate at least 75% of the specified rate of air circulation at the point where defrosting is initiated.
- Extreme uniformity in temperature is required within each container. The temperature variation within the container when cooled to carrying temperature should not exceed ±0.5°C.
5.5 Air Temperature Control
- Air delivery temperatures to the container must be controlled within the range -25°C to +20°C when operating in any ambient temperatures between -10°C and 38°C.
- The temperature of the air entering the container is to be controlled to ±0.5°C in the range -5°C to +20°C for chilled cargo.
- To meet delivery air temperature control in chill mode, the compressor must run continuously and capacity control must be fitted (e.g., hot gas by-pass, suction throttling, or cylinder unloading).
- Provision must be made to prevent air delivery temperature falling below 1°C of the specified optimum carrying temperature for the specific product in the event of electronic controller failure.
- For deep frozen cargo, the temperature is controlled on return air at a maximum of -25 ±1°C.
- If the delivery air controller is used for frozen temperatures, an upper limit safety device is required.
- Electronic control equipment must maintain the stated accuracy when located in the machinery compartment. Resistance thermometers must ensure minimum errors in the range -2°C to +2°C.
5.6 Fresh Air Ventilation
- The rate of fresh air introduction is to be a minimum of one change every two hours based on the empty volume of the container.
- Fresh air must be introduced before the cooler to ensure cooled air is introduced into the container.
- The air inlet must be adjustable (completely shut-off type).
- The CO₂ sampling point must be fitted to the return duct.
5.7 Temperature Recording
- Requirements as per section 3.4 also apply.
5.7.1 Chilled Cargo
- Sensing elements of the temperature recorder and control must be positioned in the air delivery.
- An external test facility must be provided.
- Temperature recording equipment must monitor the temperature of the air entering the container and be accurate to ±0.5°C over the range -5°C to +20°C.
- A facility must be provided for remote monitoring of temperatures at a control point.
5.7.2 Deep Frozen Cargo
- Sensing elements of the temperature recorder and control should preferably be positioned in the air return.
- Temperature recording equipment must monitor the air return with an accuracy of +1°C in the range -5°C to -30°C.
6. Sanitary Aspects
- All containers must be designed and built to allow easy internal cleaning.
- All containers must be taint-free and tested according to BS 3755 or equivalent national standard.
7. Certification
- A certificate of approval of performance and safety is required for both the container and the refrigeration plant from a recognized classification society.