A thermal cover is insulation that delays heat transfer around a pallet; it does not produce cold. If the product starts above its target temperature the cover will not chill it, and with no cold source the pallet drifts slowly towards ambient.
Time is set less by the number of layers than by how full the pallet is, the product's starting temperature and the base. A cover usually closes the top and sides, while an open base stays as a path for heat. An insulated base under the pallet, or a cover brought down beneath it, lengthens the time the same cover gives.
If a supplier quotes only a total number of hours, two offers cannot be compared. Ask in writing for the test product, starting and ambient temperature, base closure, sun or shade and sensor position.
You measure the time it buys on your own load like this:
- Take two pallets from the same batch, one covered and one uncovered.
- Put a sensor at a representative product point and hold both under conditions close to the real route.
- Compare the hours until each reaches the product limit, repeat the trial and keep the raw record.
- If it approaches the limit, put a plate under the cover or add active cooling.
If you choose a returnable cover, plan collection, washing, drying and damage checks from the start; without that routine the covers go missing.
