Reefer container pre-trip inspection: what shippers of perishables should check before loading

Refrigerated containers carry a large share of the world's perishable trade: fruit, vegetables, meat, seafood, dairy and pharmaceuticals. Before a reefer is released for loading, it should pass a pre-trip inspection, usually called a PTI. The PTI is carried out by the container owner, a depot or a contracted technician, but its quality directly affects the shipper's cargo. A unit that leaves the depot with a weak compressor, a damaged door seal or a blocked drain can turn a routine voyage into a claim. This overview explains what a PTI covers, what shippers can check themselves at loading, and the questions worth asking.

What a PTI is meant to do

A PTI confirms that the container is structurally sound, clean, and that its refrigeration machinery can hold the required temperature for the trip. Modern reefer controllers include an automated PTI routine that tests components in sequence: compressor, fans, heaters, sensors, valves and the controller itself. A full PTI usually also includes a manual inspection of the box and a temperature pull-down test.

Depots typically mark a passed unit with a PTI sticker or record showing the date and result. Many carriers treat a PTI as valid for a limited period, often around 30 days, after which it should be repeated before a new booking. Shippers should check that date when the box arrives.

The structural and hygiene checks

Door seals and gaskets. Damaged or flattened gaskets let warm, humid air in and cold air out. Inspect the full perimeter of both doors for tears, gaps and missing sections. A light test, with someone inside the closed box looking for daylight, is a simple check at the depot.

Floor and T-bar channels. Reefers deliver cold air from the bottom through T-shaped floor channels. Broken floor sections, debris or residue in the channels restrict airflow and create warm spots in the load.

Walls, roof and insulation. Dents and punctures can damage insulation and create condensation or warm zones. Look for repairs and patches, and ask about any significant damage history.

Drains. Floor drains and evaporator drain lines must be clear so that condensate and defrost water can escape. Blocked drains lead to ice buildup or standing water. At the same time, drain plugs or valves should be set according to the cargo; some cargoes need them closed for controlled-atmosphere or humidity reasons.

Cleanliness and odour. The box should be clean, dry and odour-free. Taint from a previous cargo, such as fish or chemicals, can ruin dairy, fruit or chocolate. Food-grade cleanliness is a reasonable expectation for food shipments.

The machinery checks

The automated PTI covers most of these, but shippers should know what is being tested:

• Compressor and refrigerant circuit: pressures, refrigerant charge and absence of leaks.
• Evaporator and condenser fans: correct operation and direction, including high and low speed where relevant.
• Heaters and defrost: heaters are needed both for defrosting and for holding chilled setpoints in cold weather.
• Sensors: supply and return air sensors should read accurately; a probe that drifts by a degree or two can be enough to damage sensitive fruit.
• Controller and data logger: correct software, clock, and the ability to record and download temperature history.
• Fresh air vent: the vent should open and close as set, and be calibrated for the cargo's ventilation requirement.
• Power cable and plug: no damage, correct plug, secure connection.

A pull-down test, running the unit to a low setpoint and confirming it reaches and holds temperature within an expected time, is the clearest practical proof that the system works.

Settings: where many problems really start

A perfectly healthy reefer can still damage cargo if it is set incorrectly. Common setting errors include:

• Setpoint entered in Fahrenheit instead of Celsius, or vice versa.
• Wrong sign on a frozen setpoint, such as +18 instead of −18.
• Fresh air vent closed for respiring produce that needs ventilation, or open for frozen cargo that does not.
• Humidity control or dehumidification set when the cargo does not need it.
• Controlled-atmosphere or cold treatment settings missing for cargo that requires them.

The setpoint, ventilation and humidity values on the booking should match the shipper's instructions, the carrier's records and the controller display. Photographing the controller after setting is an inexpensive habit that resolves many later disputes.

Pre-cooling: the box, not the cargo

Reefers are designed to maintain the temperature of cargo that is already at the correct temperature. They are not designed to remove large amounts of field heat. Produce and meat should be pre-cooled to the carrying temperature before loading.

Whether to pre-cool the container itself depends on the loading situation. With a sealed cold-dock connection, pre-cooling the box is useful. When loading at an open dock in warm, humid conditions, pre-cooling the box can draw in moist air that condenses on cold surfaces and cargo, so many guides advise switching the unit off while doors are open and restarting immediately after closing. Shippers should follow their carrier's guidance for the cargo type.

Loading practices that protect airflow

Even a perfect PTI cannot compensate for a load that blocks air circulation:

• Do not load beyond the red load line marked near the roof.
• Do not load past the end of the T-bar floor, and do not cover floor channels with slip sheets or loose cartons where air must pass.
• Use cartons with ventilation holes that align when stacked, for chilled produce.
• Leave no large gaps at the door end; fill them or use airbags so cold air is not short-circuited.
• Record pulp temperatures of the cargo at loading as evidence.

Documentation shippers should keep

1. The PTI record or sticker date for the container number.
2. Photos of the controller showing setpoint, vent and humidity settings.
3. Pulp temperature readings at loading, with time and location.
4. Photos of the loaded box before door closure and of the seal number.
5. Any independent temperature logger placed in the load, with its serial number.

If something goes wrong in transit, this record, combined with the controller's downloaded history, is what insurers and carriers will examine.

Questions worth asking

When booking or receiving a reefer, shippers can reasonably ask: when was the PTI completed and was it a full PTI? Does the unit's data logger cover the full voyage period? Is remote monitoring available, and who gets the alerts? What is the procedure if the unit alarms at the terminal or on the vessel?

A PTI is a technical routine, but it is also a shared responsibility. Carriers supply a sound box; shippers supply properly pre-cooled cargo, correct instructions and careful loading. When both sides do their part, most reefer claims never happen.

Key figures above are general reference points, not regulatory limits. Always follow carrier instructions and cargo-specific guidance.