Shipping Containers

There are many options regarding the container you choose to use transport your temperature controlled products. This decision will affect the cost and performance of your cold chain packaging system. While these are generally the primary concerns in making decisions about packaging, it is also important to consider things such as supply flexibility and redundancy, recyclability and reusability, as well as esthetics and overall presentation. This paper will briefly examine these issues while looking at some of the more common types of cold chain shipping containers. You will find a brief description of these common cold chain container options as well as a general summary of the advantages and disadvantages of each option.  This is in no way meant to be comprehensive.  The intent of this paper is to provide a brief overview so that individuals who are looking into developing cold chain solutions will have a general perspective of their options with regard to the containers available on the market.

EPS Containers

EPS (Expanded Polystyrene) is a cost-effective solution for many temperature-sensitive shipments. EPS is often referred to as “styrofoam”, but Styrofoam® is a trade name for an extruded building material made by Dow Chemical. EPS containers are generally considered the workhorse of the industry and account for the bulk of containers used in temperature-controlled shipments.  R-value claims for EPS can range between 3.5 and 5, depending on the density and size of the EPS bead used, but it is a little known fact that the R-value of EPS is slightly higher at colder temperatures than at room temperature. There are many companies offer a variety of stock EPS coolers to choose from.  Using a stock item is a popular option due to the high cost of creating custom molds. Additionally, some companies offer 6-panel or ‘knock-down” EPS coolers providing some dimensional flexibility and cost advantages. The following section will provide some more detail about these options.

Molded and 6-panel EPS Containers

If you choose to use an EPS container you have some options; custom molded, stock molded or 6-panel.  Your choice between stock and custom molds will likely be dependant on the volume of your shipments and the availability of stock containers that will best match your payload and budget.  The choice between molded and 6-panel containers is in many cases based on the need for flexibility, cost concerns, space considerations and performance. A note on 6-panel performance; some will debate on whether a 6-panel EPS container and a molded EPS container of the same size and density will perform equally.  In most cases a static test of these two containers will not reveal a significant performance difference.  However, it is important to consider the dynamic nature of the distribution environment and how those dynamics can affect the integrity and therefore performance of these containers.  Rigorous vibration and multiple impacts may create gaps (thermal shorts) in between the panels and therefore affect performance.

Advantages

• Lower Cost – EPS can provide a lower cost alternative to many other materials. However, there are many variables to the cost of an EPS container such as mold costs, density, complexity of design and overall size. Note that reducing the density may also reduce the thermal and protective properties of the container. Be sure to set density specifications for each container and ask for a certificate of compliance for each shipment to assure the correct density has been used.
• Less Weight – EPS as a material can weigh less than many other options. For example, a 1” wall EPS container with outer dimensions of 12” x 12” x 14” with a 1.5 pounds per square inch density would weigh approximately 3.5 pounds. A comparable PUR container could weigh as much as 9 pounds. (Be careful to understand the balance of insulation material weight and any additional need for refrigerant due to lower R-value).
• Mass Production – EPS containers can be produced in mass quantities using multi-cavity tools. This ability to manufacture large numbers of containers helps keep the cost of EPS containers low and availability high.
• Recyclable – In some cases, used EPS containers can be ground down and reused to make EPS containers.
• Re-usable – Molded EPS containers are often shipped in an external corrugate RSC, protecting them from the potential damages of the distribution environment. If there is no damage to the EPS container, it could be reused simply by replacing the outer corrugate.

Disadvantages

• Low R-value – EPS has a lower R-value than PUR and vacuum insulated containers and will be less effective in preventing outside temperatures from affecting the temperature-sensitive product. The R-value of EPS is between 3.5 and 5.0 and varies based on density.   The lack of insulating property could require more refrigerant or a need for express shipping methods which creates the possibility of increasing the total cost of shipments. 
• Higher Fragility – EPS containers can crack and separate during shipment if overloaded with weight from product and refrigerants. This is a problem rarely encountered in molded PUR or Vacuum insulated boxes. For this reason, many avoid using EPS in larger and longer range shipments.
• High Mold Cost – If a custom container is required, the cost associated with building a new tool can be substantial.  Depending on the complexity of the design, an EPS tool could cost anywhere from $15,000 to $60,000.

PUR Containers

 

PUR (Polyurethane) can be a highly effective solution for many temperature-sensitive shipments. PUR containers are less frequently utilized because of their cost, but the insulation value of PUR is higher than that of EPS. As with EPS containers you have the choice of molded and 6-panel custom and stock varieties.   As noted in the section on EPS with regard to 6-panel performance versus molded performance; some will debate on whether a 6-panel container and a molded container of the same size and density will perform equally.  In most cases a static test of these two containers will not reveal a significant performance difference.  However, it is important to consider the dynamic nature of the distribution environment and how those dynamics can affect the integrity and therefore performance of these containers.  Rigorous vibration and multiple impacts may create gaps (thermal shorts) in between the panels and therefore affect performance.  With that stated, there are some unique advantages and disadvantages associated with PUR that are described below.

Advantages

• High R-Value – The R-value of PUR is greater than that of EPS and can be used to hold tighter temperature ranges for longer periods of time. This increase in insulation value can effectively reduce the amount of refrigerant weight required and/or allow for longer shipments under more rigorous temperatures.
• Rigidity –PUR containers can withstand thousands of pounds of static pressure without any noticeable deflection. The strength of the containers allow them to be stacked high without worry about product damage and allows for heavier and larger containers to remain intact through out the shipment.
• Smaller Size – In many cases, the increased R-value allows for less refrigerant to be used to thermally protect the product, therefore potentially reducing the overall size of the insulated container needed.
• Inexpensive Tooling Cost – PUR tools are relatively inexpensive and are single-container tools. Each tool may cost only $2,000 to $6,000, much less than tooling for EPS containers.
• Reusability – Due to the rigidity of PUR, certain distribution settings may allow for some re-use.

Disadvantages

• Non-recyclable – PUR manufacturing is a permanent chemical reaction and cannot be broken down for recycling like EPS.
• High Cost – The cost of a PUR container is significantly higher than that of a comparable EPS container. This can make PUR containers cost prohibitive for many applications.  
• Slow Production Speed – Unlike EPS containers, PUR containers are not mass-produced. Individual tools create one container at a time. For larger, thicker-walled PUR containers, a single container may “cure” in the mold for over 30 minutes. Obviously, multiple tools are utilized at once in order to produce in higher quantities.
• Weight – PUR, as a material weighs, more than EPS.  Balancing the possible weight savings due to a reduction in refrigerant is key in comparing with EPS.   

Vacuum Insulated Containers

Vacuum insulated containers have the highest insulation value of all containers available on the market for small shipments. Depending on the manufacturer the range is between 23 and 45 per inch.  This advantage can come at a price; vacuum insulation is in nearly all cases the most expensive material when compared to EPS or PUR. The elevated material cost may make sense if it results in added performance and/or a possible reduction in total cost of ownership.  It is important to point out that most vacuum insulated containers on the market are not molded. In most cases they are constructed by assembling 5 vacuum insulated panels (VIPs) for the base and using the sixth panel for the lid. The base panels are often taped together in an attempt to eliminate air gaps.  The same consideration to the dynamic nature of the distribution environment and how those dynamics can affect the integrity and therefore performance of these containers should be considers as with 6-piece EPS and PUR containers.  Rigorous vibration and multiple impacts may create gaps (thermal shorts) in between the panels and therefore affect performance. There is currently only one manufacturer of molded vacuum insulated containers. See the information below for a few of the advantages and disadvantages of using vacuum insulated containers.

Advantages

• High R-Value – Vacuum insulated containers have the highest R-value of any containers, allowing them to resist extreme heat or extreme cold for long durations and therefore extend shipping times and allow for tighter product temperature control.
• Low Shipping Weight – Because of their increased insulation value, vacuum insulated containers require less refrigerant and in most cases weigh less than a comparably-designed PUR and EPS containers.  Analysis of the total cost of ownership should be made to see if reduced shipping costs outweigh the material cost difference.
• Reusable – As long as the vacuum insulated containers remain undamaged and the vacuum is not lost, the containers can be reused multiple times.   Each container must be inspected and tested prior to re-use to ensure against R-value loss.

Disadvantages

• High Cost – The cost of the vacuum insulated containers can make them a luxury of low-volume, high-value products or restrict them to being used in longer shipping durations and tighter temperature criteria situations.
• Durability – The effectiveness of a vacuum insulated container is dramatically reduced once the vacuum is lost in any of the panels. Assuming that the value of the product is high, these containers can have a risk associated with them.  Manufacturers of vacuum insulated containers often include extra materials to buffer the insulation from damage.
• Availability – Fewer manufacturers offer vacuum insulated containers than EPS or PUR and production speed is generally slower.

Active Containers

“Active” is a general term given to shipping systems that do not rely solely on the passive heat transfer principals of the packaging materials to regulate the temperatures of the payload. Passive containers use refrigerants (such as gel packs) to keep product temperatures within the desired criteria. The natural physical dynamics of the system control the product temperatures. Active containers may use thermostatic controllers, often powered by batteries, to regulate temperatures.

Active systems can use compressors or other sources such as dry ice to introduce cold air into a system and some have the ability to produce heat as well.  There are a wide variety of active containers that vary form the type of active systems used, insulation, size and shape, FAA/EASA classifications, logistics model etc.  As with all other container choices there are advantages and disadvantages. The following list highlights some of them.   

Advantages

• Automated Thermostat – Container can automatically detect that product temperatures are too warm or too cold and can adjust the internal container temperature.
• Ease of Packout – Many active containers require no packout; simply place the product load into the space provided, close the container and send. Preparation may be needed before the container is packed, such as pre-conditioning, recharging the batteries/loading new batteries or loading dry ice for systems that require it.  Overall, most active systems are simple to pack out particularly with larger payload sizes.
• Payload Size – Because there is no need to include gel packs or other refrigerants, active containers often have a larger payload area for product than passive systems. This means more temperature-sensitive material can be shipped per container, which should be considered when evaluating the total cost of the packaging.
• Reusable – In general, active containers are made to be reused multiple times.  They are usually made of durable materials and can be repaired and refurbished prior to re-use.
• Lease Options – Most manufacturers choose to lease active containers, a benefit since it requires little up-front capital. 

Disadvantages

• Availability – There has been some history of gaps in active container available.  Some vendors may require significant advance warning.  Be sure to check availability in your area.
• Battery Life – An inherent part of active containers is the need for a power source. In most cases this is a battery or batteries. For longer shipments, this can be an issue. At some point, the source of energy may be exhausted and the container will lose its ability to hold product temperatures within criteria. Some active containers only advertise 48 or 72 hours of shipping duration before the batteries have to be replaced or recharged.  Additionally, active containers with little insulation to aide in controlling temperature may experience rapid temperature change if one the batteries lose their ability to power the system.
  
• Winter Shipping – Many active containers are limited in that they can only introduce cold air into the system. This can be an issue in colder ambient conditions since these types of containers have limited protection from cold temperatures.  This may be an issue in the winter with products that cannot freeze.

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