The streams of temperature data captured by a reefer download is somehow too much and not enough at the same time.
All this data can make it difficult to pull meaningful information from the report. It seems fair to ask: do we really need to review 30 pages of data (in tenths of degrees Fahrenheit) to assess temperatures during a 4-day trip?
And yet, that’s not all—there’s also the temperature information provided by the portable recording device to consider—and this is often difficult to reconcile with the data provided by the reefer download.
In this article we’ll review some of the ways Blue Book Services uses reefer downloads to help mediate claims involving fresh produce.
It’s A Long Trailer
Although reefer downloads now accompany most of the temperature related claims we see, portable temperature recorders remain heavily used in the fresh produce industry.
Not only are portable readings immediately accessible at the receiving dock (if not before with in-transit monitoring), but these devices can be attached to the outside of shipping cartons to measure the temperature of the air surrounding perishable product.
Conversely, the temperature sensors on reefer downloads reside on the reefer-side of the bulkhead wall in the nose of a 53-foot trailer where no cargo is stored.
Imagine, for instance, a scenario where an air chute becomes detached from the reefer unit. Without the chute to channel cool air to the rear of the trailer, it will travel only a short distance before circling back to the reefer unit in the front of the trailer.
When air short-circuits in this manner, the produce in the front of the trailer enjoys temperature-controlled air, while the produce in rear of the trailer suffers.
Consequently, a portable recorder placed in the rear of the trailer will reveal a problem, while the reefer download may not.
Similarly, when the insulation and/or seals around the rear doors are in poor condition, the produce in the rear of the trailer is likely to be exposed to warmer air. So, a portable device placed in the rear of the trailer is more likely to record a temperature problem than reefer sensors in the nose.
Evaluating A Reefer Download
In many cases, the information provided by reefer downloads helps resolve disputes and settle claims.
Toward this end, our approach to assessing reefer downloads, where warm temperatures are alleged, generally follows three steps.
First, we like to use the defrost cycles as a way of breaking the streams of data into smaller chunks. A defrost cycle of 6 hours is a manageable timeframe; after numbering the cycles (DFC #1, DFC #2, etc.) we can then review a 4-day trip in 16 segments.
Second, for each of these segments, we look to see if the return air readings are generally within 1°F of the set point temperatures.
While this may seem like a very tight margin for error, we don’t normally expect to see prolonged return air readings of more than 1°F above the set point. Reefer units are capable of making the fine adjustments needed (e.g., supplying cooler air) to keep these readings within tenths of degrees of the set point.
This contrasts rather sharply with the rule of thumb we use when reviewing readings from portable recorders that are not used to regulate temperature, and which, again, reside in a different location within the trailer.
Section (6.2) of Blue Book’s Transportation Guidelines (in relevant part) provides—
(6.2) Refrigeration (or “reefer”) systems should be set to run continuously, and not on a start-stop or cycle basis. Slight deviations in transit temperature based on, among other things, the location and accuracy of the temperature recorder, are inevitable and permissible. What constitutes a “slight deviation” will vary, but as a rule of thumb temperatures within the trailer should not deviate more than four (4) or five (5) degrees Fahrenheit from the agreed-upon transit temperature. If a temperature range is specified, any deviation will be assessed from the midpoint of the specified range. A temperature variance lasting less than twelve (12) hours may also be categorized as a slight deviation, depending on the extent of the variance, the relative perishability of the commodity, and other circumstances.
Note(s) to Section (6.2)
The rule of thumb referred to in this Section applies to air temperatures recorded by portable devices attached to the outside of the pallet or packaging containing the produce. Return air temperature sensors on reefer units are separated from the produce (the cargo) by a bulkhead wall and reside in close proximity to the reefer unit’s refrigeration coils. Consequently, reefer units tend to record somewhat cooler temperatures than recording devices placed with the cargo.
If this rule of thumb (for portable recorders) were applied to reefer downloads, virtually every reefer download would show normal transportation conditions. Carriers can and do maintain much finer temperature control in the nose of the trailer where the reefer readings are taken.
And third, when reviewing reefer downloads, we look at the difference between the supply air readings and the return air readings.
When data shows that the unit needed to supply exceptionally cool air to control return air readings, this may suggest there was a temperature issue somewhere in the trailer, even if the return air readings were within the expected 1°F range described in the second step above.
In many cases, a larger-than-normal difference between the supply and return air readings will help reconcile an apparent difference between the reefer download and warm readings from a portable recorder.
So, what’s a larger-than-normal difference between supply and return air readings? How is this defined? Consistent with Section (6.2) from our guidelines, we don’t typically expect to see a variance of more than 4 to 5°F.
A greater difference, for an extended period—more than a temporary blip—may suggest the temperature control was lacking in at least one location within the trailer. A difference of 6 to 7°F, for instance, would be far warmer than we would expect to see.
Of course, carriers will sometimes point out that the difference between the supply and return air readings may have been caused by the shipper’s failure to properly precool the product prior to loading.
This may surely be true in some cases, but if product was not properly precooled at shipping point, we would usually expect to see the difference between the return and supply air temperatures diminish over time as field heat dissipates and respiration rates slow in the first 24 hours after harvest.
In addition, carriers alleging that product was warm at loading can typically expect the shipper to step forward with first-hand statements and/or internal records stating the product was, in fact, properly precooled prior to loading.
And while this type of evidence may be considered self-serving, it is usually stronger than the carrier’s speculation, without direct first-hand knowledge, that the product was warm when loaded.
Still, for mediation purposes these angles should be explored and temperature claims must be viewed on a case-by-case basis.
Details matter and all interested parties need to weigh in before a fully informed resolution can reached. Guidelines or benchmarks, such as we’ve suggested here, help shape expectations and facilitate a more constructive discussion of temperature claims.
As always, we welcome your feedback and perspective.
