The temperature data streams captured by a chilled discharge are somehow too much and not enough at the same time.
All of this data can make it difficult to obtain meaningful information from the report. It seems fair to ask: do we really need to go through 30 pages of data (in tenths of a degree Fahrenheit) to assess temperatures during a 4-day trip?
And yet that is not all, there is 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 chilled discharge.
In this article, we will review some of the ways Blue Book Services uses refrigerated discharges to help mediate claims related to fresh produce.
It’s a long trailer
Although refrigerated discharges now accompany most of the temperature-related claims that we see, portable temperature recorders are still widely used in the fresh produce industry.
Not only are portable readings immediately accessible at the receiving dock (if not earlier with in-transit monitoring), but these devices can be placed on the outside of shipping boxes to measure the temperature of the surrounding air. perishable product.
In contrast, the temperature sensors in the chilled dumps reside on the chilled side of the bulkhead wall at the nose of a 53-foot trailer where no cargo is stored.
Imagine, for example, a scenario where an air duct is detached from the refrigerated unit. Without the duct to channel cool air to the rear of the trailer, it will travel only a short distance before circling back to the refrigerated unit at the front of the trailer.
When the air is short-circuited in this manner, the product at the front of the trailer enjoys temperature-controlled air, while the product at the rear of the trailer suffers.
Consequently, a portable recorder placed at the rear of the trailer will reveal a problem, while the refrigerated discharge may not.
Similarly, when the insulation and / or seals around the rear doors are in poor condition, the products in the rear of the trailer are likely to be exposed to warmer air. Therefore, a portable device placed at the rear of the trailer is more likely to register a temperature problem than cooled sensors in the nose.
Evaluation of a refrigerated discharge
In many cases, the information provided by refrigerated discharges helps to resolve disputes and resolve claims.
To this end, our approach to evaluating cold discharges, in which warm temperatures are claimed, generally follows three steps.
FirstWe like to use defrost cycles as a way to divide data streams into smaller chunks. A 6 hour defrost cycle is a manageable period of time; After numbering the cycles (DFC # 1, DFC # 2, etc.) we can review a 4-day trip in 16 segments.
SecondFor 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 narrow margin of error, we typically do not expect to see prolonged return air readings more than 1 ° F above the set point. Refrigerated units are capable of making the precise adjustments necessary (for example, supplying cooler air) to keep these readings within tenths of a degree of the set point.
This is in sharp contrast to the general rule of thumb we use when reviewing readings from portable loggers that are not used for temperature regulation and that, again, reside in a different location within the trailer.
Section (6.2) of the Blue Book Transport Guidelines (where relevant) states:
(6.2) Refrigeration (or “reefer”) systems should be configured to run continuously and not cycle or start-stop. Slight deviations in transit temperature based, among other things, on the location and accuracy of the temperature recorder, are unavoidable and permissible. What constitutes a “slight deviation” will vary, but as a general rule, temperatures inside the trailer should not deviate more than four (4) or five (5) degrees Fahrenheit from the agreed-upon traffic temperature. If a temperature range is specified, any deviation will be evaluated from the midpoint of the specified range. A temperature variation lasting less than twelve (12) hours may also be classified as a slight deviation, depending on the extent of the variation, the relative perishability of the product, and other circumstances.
Note (s) to section (6.2)
The rule of thumb referenced in this Section applies to air temperatures recorded by portable devices attached to the exterior of the pallet or package containing the product. The return air temperature sensors in the refrigerated units are separated from the product (cargo) by a bulkhead wall and are in close proximity to the refrigeration coils of the refrigerated unit. Consequently, refrigerated units tend to register somewhat cooler temperatures than logging devices fitted with the load.
If this rule of thumb (for portable recorders) were applied to refrigerated discharges, virtually all refrigerated discharges would show normal shipping conditions. Carriers can and do maintain much more precise temperature control at the front of the trailer where reefer readings are taken.
And thirdWhen reviewing the cooled discharges, 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 monitor the return air readings, this may suggest that there was a temperature problem somewhere in the trailer, even if the return air readings were within the expected range of 1 ° F described in the second step. about.
In many cases, a larger than normal difference between the supply and return air readings will help reconcile an apparent difference between the refrigerated discharge and the warm readings from a portable recorder.
So what is a larger than normal difference between the supply and return air readings? How is this defined? According to Section (6.2) of our guidelines, we normally do not expect to see a variation of more than 4-5 ° F.
A larger difference, over an extended period, rather than a temporary flash, may suggest that temperature control was missing in at least one location within the trailer. A difference of 6 to 7 ° F, for example, would be much 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 adequately pre-cool the product before loading.
This can surely be true in some cases, but if the product was not adequately pre-cooled at the point of shipment, we would generally expect to see the difference between the supply and return air temperatures decrease over time as the heat from the field dissipates and respiration rates decline in the first 24 years. hours after harvest.
Additionally, shippers claiming the product was hot during loading can generally expect the shipper to step up with first-hand statements and / or internal records indicating that the product was, in fact, properly pre-cooled prior to shipment. load.
And while this type of evidence can be considered self-interested, it is generally stronger than the carrier’s speculation, without direct first-hand knowledge, that the product was hot when loaded.
Still, for mediation purposes, these angles should be explored and the temperature claims should be viewed on a case-by-case basis.
Details matter and all stakeholders must have a say before a fully informed resolution can be reached. Guidelines or benchmarks, like the ones we’ve suggested here, help shape expectations and facilitate a more constructive discussion of temperature claims.
As always, we welcome your comments and insights.