Chapter 3: General Requirements for Refrigerated Road Transport Vehicles

Contents

1. Introduction
2. Basic Requirements for Refrigerated Vehicles
   • 2.1 Insulation
   • 2.2 Construction Criteria
   • 2.3 Cooling Unit Capacity
   • 2.4 Temperature Requirements
     • 2.4.1 Temperature Control Thermostat
     • 2.4.2 Delivery Air Temperature
     • 2.4.3 Return Air Temperature
     • 2.4.4 Integrating Temperature Control
     • 2.4.5 Temperature Measurement and Recording
   • 2.5 Air Circulation and Distribution
     • 2.5.1 Air Circulation Requirements
     • 2.5.2 Fresh Air Ventilation
3. Preload Checks of Refrigerated Vehicle
   • 3.1 Overall Condition
   • 3.2 The Insulation
   • 3.3 The Vehicle
   • 3.4 Precooling and Temperature Checks
     • 3.4.1 Precooling of the Vehicle
     • 3.4.2 Temperature Checks
4. Preparation of Refrigerated Cargo
   • 4.1 Packaging and Palletisation
   • 4.2 Precooling of the Product
   • 4.3 Selection of Product According to Consignment
   • 4.4 Product Temperature Recording
5. Loading Equipment and Procedures
   • 5.1 Loading Equipment
     • 5.1.1 Forklifts and Pallet Jacks
     • 5.1.2 Air Locks and Loading Bays
   • 5.2 Loading Procedure
   • 5.3 Confirmation of Transport Temperature
   • 5.4 Maximum Axle Weight
6. Transport Temperature Maintenance
   • 6.1 Checks During and on Completion of Loading
   • 6.2 During Transport
   • 6.3 During Off-loading

1. Introduction

A refrigerated road transport vehicle is designed to move refrigerated produce from one point to another under cooling. It is not a precooling unit, but is built to move the maximum payload at a specified temperature. Perishable products must be precooled to the transport temperature and loaded with minimal temperature increase. Understanding product temperature dynamics, cooling system characteristics, and cold air management is essential. Common terms include Refrigerated Motor Transport (RMT) and refrigerated trailers.

2. Basic Requirements for Refrigerated Vehicles

2.1 Insulation

• Polyurethane foam between glass reinforced plastic (GRP) inner and outer skins.
• Minimum insulation thickness:
  • Sidewalls: 55mm (recommended 65mm)
  • Roof, door, bulkhead: 70mm (recommended 100mm)
  • Floor: 100mm (recommended 115mm)
• Heat transfer: 0.4 Watts/m³°C maximum

2.2 Construction Criteria

• Floor: 50mm deep T-bar construction for better return air flow.
• Sidewalls: Grooved or fluted for air space between cargo and inner skin.
• Bulkhead: False bulkhead with open bottom entry for unobstructed return air.
• Doors: Double doors with positive pressure locking for airtight seal.

2.3 Cooling Unit Capacity

• Common brands: ThermoKing and Carrier (ATP certified).
• Minimum cooling unit capacity depends on vehicle length/load capacity.

2.4 Temperature Requirements

2.4.1 Temperature Control Thermostat

• Must control and measure temperature in the delivery air stream.

2.4.2 Delivery Air Temperature (DAT)

• Temperature of air just before it contacts the product.
• DAT increases with distance from the cooling coil (up to 1°C difference).

2.4.3 Return Air Temperature (RAT)

• Temperature of air before it enters the return air opening at the bulkhead bottom.
• RAT reflects all heat removed by circulating air.
• DAT and RAT difference should not exceed 1.5°C.
• For deep-frozen produce, control must be in the RAT before the evaporator.

2.4.4 Integrating Temperature Control

• Modern units measure both DAT and RAT, adjusting air delivery accordingly.
• If product is not uniformly precooled, cold air may cause chilling/freezing injury.

2.4.5 Temperature Measurement and Recording

• Temperature recorder: Accurate, calibrated, sensor in delivery air near thermostat.
• Dial temperature indicator: For driver reference, sensor in delivery air.
• DAT and RAT thermocouples: As above.

2.5 Air Circulation and Distribution

• Ceiling-mounted cold air supply for top-to-bottom circulation.
• Return air flows via T-bar floor/pallet openings.

2.5.1 Air Circulation Requirements

• Minimum air speed: 1 m/s at 50mm water gauge static pressure.
• Air delivery/return plenums must be clean and unobstructed.
• Use tested air distribution systems.
• Ensure correct cargo loading configuration.

2.5.2 Fresh Air Ventilation

• Fresh produce needs oxygen; some produce is sensitive to ethylene.
• Guidelines for a 12m vehicle:
  • Minimum air change: 30 m³/hour
  • Maximum air change: 250 m³/hour (0.5 to 4.5 air changes/hour)
• Too much fresh air increases heat load and reduces relative humidity.

3. Preload Checks of Refrigerated Vehicle

• 3.1 Overall Condition: Good repair, no cracks, intact door seals.
• 3.2 Insulation: No damage, all joints sealed.
• 3.3 Cleanliness: Clean outside and inside, especially T-bar floor and air return ducts.
• 3.4 Precooling and Temperature Checks:
  • 3.4.1 Precooling: Strongly recommended to cool body structure and check cooling unit operation.
  • 3.4.2 Temperature Checks: After precooling (min 3 hours), check and record:
    • Temperature set point
    • DAT (within ±0.5°C of set point)
    • RAT (stable and within tolerance)
    • Ice calibration if DAT deviates by more than 0.5°C from set point.

4. Preparation of Refrigerated Cargo

• 4.1 Packaging and Palletisation: Ensure air space at top, unobstructed airflow, align carton ventilation with pallet base openings.
• 4.2 Precooling of Product: Product must be precooled to required transport temperature.
• 4.3 Selection of Product: Consignment must meet buyer’s specs before loading; traceability applies (cold store/pallet/vehicle identification).
• 4.4 Product Temperature Recording: Record pallet ID, fruit temperature (center and outer carton), checked and countersigned by driver, sent to PPECB port office.

5. Loading Equipment and Procedures

• 5.1 Loading Equipment:
  • 5.1.1 Forklifts and Pallet Jacks: Only battery-operated forklifts; hand pallet jacks for small operations.
  • 5.1.2 Air Locks and Loading Bays: Use insulated, temperature-controlled air locks; loading bays for efficient handling.
• 5.2 Loading Procedure:
  • No openings between pallets/cartons or open floor spaces.
  • Do not load above horizontal load line (80mm from ceiling) or beyond vertical load line.
  • Maintain at least 20mm air space at sides.
  • Allow unobstructed vertical airflow channels.
  • Complete loading within 30 minutes; close doors and apply cooling during breaks.
  • Ensure doors are properly closed and sealed.
• 5.3 Confirmation of Transport Temperature: Thermostat set to required temperature; transport document completed and signed by consignee and driver.
• 5.4 Maximum Axle Weight: Do not overload; cover open floor spaces if fewer pallets are loaded.

6. Transport Temperature Maintenance

• 6.1 Checks During and on Completion of Loading:
  • Product uniformly precooled.
  • Cooling unit operates within specifications.
  • Compartment precooled.
  • Minimize temperature increases during loading.
  • Thermostat set to specified temperature.
  • At least one pulp temperature reading per pallet recorded.
• 6.2 During Transport:
  • Refrigeration unit runs continuously.
  • Driver checks dial thermometer every two hours.
  • Cooling unit checked every four hours.
  • Report malfunctions, temperature deviations, and delays.
• 6.3 During Off-loading: Vehicle and product temperatures checked at off-loading.