Reefer Container Pre-Trip Inspection (PTI): What Gets Checked Before Your Frozen Cargo Loads

A reefer container that carries a passing PTI sticker on its door has cleared a mechanical test — it has not promised that your cargo survives four weeks between a Ningbo cold store and a Chattogram warehouse. Pre-Trip Inspection, or PTI, is the check a reefer unit goes through before it is ever loaded, and understanding what it actually covers (and what it does not) matters the first time a shipment arrives with a temperature excursion nobody can explain.

What a Pre-Trip Inspection Actually Tests

A PTI is run on the refrigeration unit itself, not the cargo or the box structure. A technician plugs the reefer into a test stand or genset and runs it through a fixed sequence: compressor start-up, defrost cycle activation, evaporator and condenser fan operation, and a check that the controller can actually pull the box down to a target set point and hold it. Most modern units (Carrier, Thermo King, Daikin) run this as an automated self-test that takes 30–45 minutes and prints or logs a pass/fail result with individual sub-test codes. What it does not test is door seal integrity under a full load stack, insulation panel condition after years of forklift dings, or how the unit performs once it is stacked in the middle of a vessel bay with reduced airflow around the condenser — all of which affect real-world performance far more than a clean PTI printout suggests.

Where PTI Fits Before Your Cargo Ever Loads

PTI happens at the depot, before the empty container is even trucked to the factory or cold store for stuffing. It is a depot or carrier responsibility, not something your supplier or forwarder witnesses, which is exactly why importers rarely see the paperwork unless they ask for it specifically. A container that fails PTI is pulled from the available pool and either repaired on the spot (a common fix is replacing a faulty defrost sensor or topping up refrigerant) or tagged out of service. The importer never sees the failed unit — they only see the one that eventually shows up at the factory gate, already passed. This is different from the visual door-and-genset check a trucker or CFS staff might do at gate-in, which confirms the unit is running and set correctly, not that it passed a full diagnostic cycle.

Reading the Controller: Set Point, Return Air and Supply Air

Once cargo is loaded and the door closed, the numbers that matter shift from the PTI result to three live readings on the controller display: set point (what you told the unit to hold), return air temperature (air coming back from inside the box, closest to what the cargo itself feels), and supply air or discharge air temperature (air just after it leaves the evaporator, always colder than set point because it has not picked up heat from the cargo yet). A unit sitting exactly on set point for return air with a wide gap to supply air usually means the box is working correctly against a real heat load. A return air reading that will not come down no matter how the compressor runs is a sign of an airflow problem — often overpacked cargo blocking the return air path at the back of the container, not a mechanical fault at all. This is why a technically perfect PTI can still end with a warm shipment: the fault was introduced during stuffing, well after the machine itself was cleared.

Common PTI Fault Codes and What They Are Telling You

Reefer controllers log fault codes in fairly consistent categories across brands, even though the exact alarm numbers differ. A defrost sensor fault means the unit cannot reliably tell when ice has built up on the evaporator coil, which left unresolved leads to reduced airflow and slow temperature recovery mid-voyage. A high discharge pressure alarm points to a dirty or blocked condenser coil, or airflow obstruction around the unit’s intake — a real risk if the reefer is stowed too close to another box or a vessel structure with no clearance. A low refrigerant charge alarm is exactly what it sounds like, and if not corrected before loading it shows up later as the unit running constantly without ever reaching set point. None of these faults are visible from outside the box, and none of them are things a Bangladeshi importer receiving the cargo at the other end can influence — which is precisely why catching them at PTI, before stuffing, matters so much more than catching them on arrival.

What Happens When a Reefer Fails PTI at Origin

A failed unit at the depot is simply swapped for another from the pool before it ever reaches your supplier’s factory, so in the ordinary case a PTI failure costs the carrier time, not you money. The exception is a tight loading schedule during a demand spike (pre-Chinese New Year shipping, for instance), when reefer equipment itself becomes scarce and a string of failed units can genuinely delay when a working box reaches the factory gate. In that scenario the practical fix is the same one that applies to backup power more broadly: knowing whether your forwarder’s depot keeps spare units on standby, or whether a failure means waiting for the next available box in the queue.

Why Bangladeshi Importers Should Ask for the PTI Report

If a shipment arrives with visible signs the cold chain broke somewhere — a topic covered in detail in our guide to detecting thawed and refrozen cargo — the PTI report is one of the first documents an insurer or the shipping line will ask for, because it establishes whether the unit was mechanically sound at the start of the journey. Without it, any claim becomes a dispute over whether the fault was equipment failure (the carrier’s liability) or a break in the chain caused by loading, transshipment delay, or destination handling (which may fall back on the importer or the insurer’s general exclusions). Asking your forwarder to request the PTI printout as a standard part of the shipping document set costs nothing and gives you a paper trail before you need one.

Mistakes That Undo a Clean PTI Result

The most common failure pattern has nothing to do with the machine at all. Overpacking a reefer to save on freight cost blocks the T-bar floor channels and rear return-air path the unit depends on to circulate cold air evenly, so even a unit that passed PTI perfectly cannot maintain uniform temperature front to back. Loading warm product straight from a factory line without pre-cooling forces the reefer to remove heat it was never sized to handle quickly, which is a cargo-side problem, not a PTI failure. And setting the wrong set point for the actual commodity — treating a chilled product like a frozen one, or vice versa — produces exactly the kind of temperature excursion that looks, on paper, like equipment trouble but is really a specification mismatch made at the loading dock. A passing PTI is the starting point for a reefer shipment holding its temperature, not a guarantee of it, and treating it as the latter is where most importers get caught out.

If you are shipping temperature-sensitive cargo from China and want the loading, documentation and monitoring handled end to end, DE International arranges door-to-door cold chain logistics with reefer equipment sourced from carriers who provide PTI documentation as standard. Contact us to discuss your next shipment, or browse our sourcing and buying agent service if you are still finalising your supplier.