What is Thermal Testing?
Thermal Testing is the process of determining if a custom packaging configuration will be successful in holding the temperature of a temperature-sensitive product within its acceptable temperature criteria when it is exposed to ambient conditions. For those unfamiliar with cold chain jargon, we will approach these terms one at a time. First, a custom packaging configuration generally refers to a combination of insulated containers and refrigerants that are put together in a unique way. Developing this custom configuration can be a difficult process depending on other project factors. Second, this type of testing is used for temperature-sensitive products, which is essentially any material that, for any reason, must be kept from getting too warm or too cold. Third, the goal of the configuration is to keep a temperature-sensitive product within its acceptable temperature range. This may mean “refrigerated”, such as 2-8ºC, or “frozen” below -20ºC. Finally, the custom packaging configuration is tested against pre-specified ambient profiles, which are the temperature profiles programmed into the large environmental chambers that will simulate the temperature conditions a package may be exposed to during transport.
Why perform Thermal Testing?
Although there are many reasons not to perform testing, such as the cost, the time to test, and the time required to work on the project, there are many stronger reasons in favor of testing. First and foremost is the safety of the consumer. This is especially true for pharmaceuticals, but is also important in food delivery and other industries where temperature can create conditions that affect the safety and efficacy of the product. For example, insulin shots that arrive frozen will not be as effective and may cause harm to the end-user. Many companies lose sight of this as the ultimate reason for performing testing. Another primary reason to perform testing is the requirement by the FDA that thermal packaging is qualified under realistic conditions to prove that products arrive unadulterated to the patients. FDA audits are often dreaded events by regulated companies, especially if they result in a 483 warning letter detailing the processes within the company which are not done correctly. Finally, product quality and the cost of poor quality must be considered. If summertime chocolate shipments reach the consumer melted, the cost of processing complaints, of re-sent shipments, and of falling consumer confidence will pale in comparison to the cost of a validated summer packaging configuration.
Test Lab Certifications
Thermal test labs generally follow cGLP practices when it comes to creating and handling data. Many are “certified” as ISTA 5B locations, but this has less to do with their processes and more to do with the equipment they have on site. Test labs may also be ISO certified, depending on the parent company’s quality system. When in doubt, it is best to perform your own audit of the test lab to ensure their processes and documentation systems are in line with what your company expects from your vendors. Most test labs are accustomed to this type of audit and it will generally only take one day to complete.
The Costs of Thermal Testing
Fees for designing and qualifying a custom packaging configuration can vary greatly. Some manufacturers with engineering facilities may not charge for testing that uses their products. Other thermal test labs charge thousands of dollars for package testing, often regardless of which manufacturer’s components are being used. Determining which test facility to use should look at price, but should also consider the reputation of the lab; remember, the FDA is judging the shipper, not the lab, when it audits the final qualification reports for the custom packaging configuration. The price may be higher at some test labs, but even manufacturers who give away package design will recoup their costs somehow, most likely by increasing the packaging’s costs to you later.
In general, thermal testing facilities are honest about results and there is little bias towards certain products, even by manufacturing company’s labs. The industry is too small and reputation is too important to manipulate data or not follow appropriate procedures. Ask others in the industry or contact a member of the TPG (Temperature Control Pharmaceuticals Group) for laboratory recommendations.
Worst-Case Bracketing
The process of thermal testing for temperature-sensitive is designed to challenge the container under worst-case conditions. There are many factors in a testing project where worst-case bracketing is used to ensure the final configuration will be successful in the real-world of shipping. First, packaging engineers test the minimum and maximum amounts of product that would be allowed in the container. This confirms that the minimum amount of product mass, as well as the maximum amount of product mass, will both work in the configuration. This bracketing is used to allow companies to feel comfortable that any amount of mass between the minimum and maximum amount tested would be allowable and successful. Second, the ambient profiles chosen are designed to bracket the coldest and warmest temperatures that a shipping container would be reasonably exposed to. See the discussion about ambient profiles for more information. Finally, the locations within the product loads where temperatures are recorded are also chosen to be the worst-case location. This is done to ensure all of the product within the shipping container remains with the required temperature range, not just some of it. For example, a biotech company shipping 200 vials will need to prove to the FDA that all 200 vials, not just the center vial, is remaining within their required 2-8ºC range. They do this by showing the thermocouple probe locations used by the thermal testing lab, which include top and bottom corners of the product load, the most extreme locations.
The Process of Thermal Testing
Although many of the test labs listed in the ColdChainInfo.com testing directory have different methods and equipment to perform thermal testing, the general process is similar. First, the packaging engineer reviews the basic parameters of the customer’s project, including product loads, temperature criteria, ambient profiles, performance duration, and other customer requirements. Based on this information, the packaging engineer will design a custom packaging configuration using an insulated shipping container and refrigerants. The refrigerants may be frozen, refrigerated, ambient, or a combination of the three, depending on the temperature criteria. In order to collect real-time data during the test, the packaging engineer will insert thermocouple probes into the product loads at worst-case locations. The packaging engineer will precondition the product loads and the refrigerant at the appropriate temperatures well in advance of the beginning of the test. This will ensure all materials are at the correct temperature when the container is packed. When the materials are ready, the packaging engineer will assemble the configuration using the preconditioned container, product and refrigerant before placing the packed container into the test chamber. The ambient profile will be programmed into the test chamber and the data logger will be started. The test chamber simulates the temperature conditions (with or without humidity) the package will experience for the times and temperatures specified in the ambient profile. Later, when the test is complete, the packaging engineer can review the temperature data and redesign the packaging configuration if needed.
Cold Chain Packaging Science
The essence of thermal testing is controlling heat flow within the container. In general, the less heat transferring through the container walls, the better the container performance. It is important for packaging engineers to understand how heat is transferred and what materials and methods can prevent it. Computer simulations can help in predicting test outcomes, however there is currently no commercial software designed specifically for simulating cold chain testing. At best, programs using differential equations can be used after modeling the container and refrigerants, but most industries will require the proof of thermal testing.
Packaging engineers can increase the effectiveness of the refrigerant in the container by assuring that the air flow within the container is adequate. For example, a corrugate pad (which blocks airflow) sitting between a frozen gel pack and a carton of syringes will decrease the effectiveness (and overall cooling results) of the frozen gel pack as it becomes isolated from the syringes. The cold air surrounding the frozen gel pack will not be able to drop to the bottom of the container (remember that cold air is denser than warm air) and the syringes will get warm.
Outcomes and Timelines
Depending on the level of documentation required by the customer, the outcome of a thermal testing project can be any number of items. For example, if you are a food distributor, you may only need the packaging configuration from the test lab in the form of a packing diagram. On the other end of the spectrum, a pharmaceutical company conducting clinical trials in Africa may need a packing diagram, a full qualification report (including protocol) and a binder of data and graphs with calibration information to show the FDA when the drug is submitted for approval. In addition, the fact that the company is shipping to and from an international location (where different languages are prevalent), they may also want an animated packing diagram using software such as SolidWorks or AutoDesk’s Inventor in order to eliminate any translation errors.
The timelines for a thermal project depend heavily on the amount of documentation that will be required. In general, companies willing to go through the time and possible expense of a test project will want to conduct the full design and qualification in order to have a fully qualified shipper when the project completes. For a fully qualified shipper, a project may take anywhere from 3 months to 1 year. The length of time depends on the amount of test product available, the performance duration of the project, the size of the container (fewer large containers may fit within a test chamber), or the product’s temperature range. Also, extreme ambient profiles with hotter heat soaks or colder cold soaks could also extend the timeline of the project.
The main lesson to be learned from thermal testing is this: failing to allow enough time for the testing project to complete will often result in an over-engineered shipper. Accelerating a project’s timeline will reduce the engineers’ opportunities to optimize the performance of the configuration, thus reducing chances to simplify the configuration, reduce the cost of the components, or reduce the weight of the final design.
Education and Careers
There is a wide variety of educational paths that could lead to a career in thermal testing. Although many project engineers have degrees in Packaging Engineering from Michigan State, RIT or another of the handful of schools offering that degree, most come from another field. Some of the “best” backgrounds include Chemical Engineering, Mechanical Engineering, Materials Engineering, Chemistry, Physics, or Industrial Engineering. These disciplines offer education in key factors such as heat flow, material properties, thermodynamics, and design of experiments. Fields with a strong chemistry background also have the advantage of being comfortable with the compound names and chemicals the pharmaceutical and biotech companies use in their products.
Those without a bachelor’s degree in Packaging Engineering may look to get a Master’s degree in this field. An online program from Michigan State University is a convenient way to further your packaging education without leaving your current job. Check out http://www.packaging.msu.edu/online_ma.php for more details.