If you are looking for a carrying case, transit case or shipping case to protect your equipment, you should be able to relay the performance expectations to your packaging professional. That’s so he / she can adequately address your requirement. If you do not set these expectations, you run the risk of having inadequate protection with potential equipment damage and nobody to blame.
In this posting, I address how handling and transport influence the design of protective case interiors. How the case or container will be transported plays an important role in dictating the design of an interior to protect the equipment (stored within) from impacts the case may encounter in transit.
On a general level, how the protective case will be moved around is a factor to consider when determining what height the case might be dropped from.
If the case is small and light enough for one or two individuals to carry, it’s safe to assume at some point in time the case will likely be dropped (human error). Depending on the size of the case, and location / orientation of the handles, you would expect the case to be dropped from a height of 24 to 30 inches (609.6 to 762 mm).
Larger, heavier items are usually handled using pallet trucks and forklifts. If the weight of the case is a couple hundred pounds or less, we assume the case will be placed on a pallet. Assuming it may not always be strapped down, there is a chance the case could fall off the pallet. In this scenario, it’s prudent to assign a drop height of 24 to 30 inches (609.6 to 762 mm). If the case weight is over 200 lbs. (90.7 kg), there is less of a high-drop probability. But, the operator may lower the load too quickly. So, a general rule of thumb is to assume a drop height of 8 to 12 inches (203.2 to 304.8 mm).
A small item weighing a few ounces (grams) to a few pounds (kilograms) will typically be shipped via courier. Whereas, larger items weighing hundreds of pounds (kilograms) are likely to be palletized and shipped via commercial transport.
Transport via courier means the case will be loaded / unloaded by hand, potentially sorted using a conveyor system, and loosely placed in a cargo van or something similar. So, it’s not unreasonable to expect there might come a time when the case could be dropped, kicked, tumble or bounce around in the back of a vehicle. This means the protective case could be impacted on any face, corner or edge.
Larger, heavier items will usually be handled using pallet trucks and forklifts. Once they lift a pallet off the ground, forklift operators typically tilt the load towards them for stability. When the pallet is lowered down, one edge or corner usually contacts the floor first before sitting down proper.
Unless there is a requirement to protect equipment under the most extreme situations, packaging experts will usually reason that a palletized or forklift able case will not drop from a height where it can flip upside down.
However, tall cases may be prone to tip over. Assuming the length is greater than the width, the case height should not exceed 1.5 times its width in order to maintain stability and minimize risk of tipping over. If the height must exceed this 1.5X factor, you need to assume the case may tip over at some point. In that case, the side walls may see a much higher level of impact than the other areas.
Now that we’ve narrowed down the scope of how the protective case will be handled and transported, we can look at defining an appropriate drop height.
If your requirement is Aerospace or Defense related, you should refer to the United States Department of Defence (DoD) test standard MIL-STD-810G, Method 516.6, Procedure IV (Transit Drop) for directions in assigning the correct drop heights and parameters.
The following table is a modified / simplified version of the Transit Drop Test tables found in MIL-STD-810G.
| Handling | Approx. Weight | Drop Height | Drop Surfaces |
| Carrying (1 Person) |
< 20 lb (< 9.1 kg) |
30 in. (762 mm) |
All Corners (8) All Edges (8) All Faces (8) |
| Carrying (1 Person) |
21 – 50 lb (9.5 – 22.7 kg) |
24 – 30 in. (609.6 – 762 mm) |
All Corners (8) All Edges (8) All Faces (8) |
| Carrying (2 Persons) |
51 – 100 lb (23.1 – 36.3 kg) |
18 – 24 in. (457.2 – 609.6 mm) |
All Corners (8) All Edges (8) All Faces (8) |
| Forklift | 101 – 200 lb (45.8 – 90.7 kg) |
24 – 30 in. (609.6 – 762 mm) |
All Corners (8) |
| Forklift | > 200 lb (> 90.7 kg) |
8 – 12 in. (203.2 – 304.8 mm) |
Bottom Corners (4) Bottom Face (1) |
As discussed in my last posting, the fragility rating refers to the maximum rate of acceleration (in g) which an object can withstand without being damaged. Combining your equipment’s fragility with the understanding of how the protective case will be handled and transported, you’re now ready to define the case’s performance with respect to shock attenuation (cushioning). A simple statement combining the defined fragility, drop height and desired impact surfaces will suffice.
Example: The item stored within shall see no more than 30 g when the case is dropped from a height of 24 inches on any face, corner or edge.
In my next blog, I’ll provide a general overview of foam cushion materials.
