Packaging for the Distribution Environment

By Victor Suben, P. E.

ery often the one thing that convinces a customer to purchase a new product for the first time is the packaging. If the package design is aesthetically attractive, unusual, or if it somehow stimulates the customer’s imagination, then the customer often purchases the product on the spur of the moment, even though it might not have been an item on a shopping list.
Conversely, if the package is scratched, scuffed, or otherwise damaged, you can be sure the customer will not make that impulse purchase. If there are other packages of the same product that are in pristine condition, the consumer may choose one of those, leaving the damaged package on the shelf.

If the consumer has experience with the brand and has a degree of loyalty to it, she may accept a package that is not in pristine condition if it is the only one left on the shelf, but she will probably feel some degree of disappointment that her brand has let her down.

Perfect Primary Packaging

The packages that appear on the shelf in the store or behind the counter are called primary packages. These are the packages that are in direct contact with the product and often serve to dispense it. Ideally, these containers should be perfect.

Although blister cards on a peg board are not primary packages, they also need to be intact and in pristine condition to attract both potential and existing customers.

Distribution Packaging Gets It There

Distribution packaging, containers that hold the primary packaging, is needed to have the product survive the rigors of the distribution environment. Because manufacturers realize the importance of safely shipping their finished goods to the store, a considerable amount of attention is paid to the distribution packaging.

Getting products to the store is not as simple as it sounds. In addition to being placed in a “pick and pack” corrugated container and subjected to the shock and vibration of being loaded on transportation as it is being moved from place to place, a package may also be subjected to elevated (or reduced) temperatures. The products may also be exposed to elevated (or reduced) conditions of relative humidity. Con­se­quently, the packaging must be rugged enough to withstand whatever conditions might occur on its way to the consumer.

Plant to Warehouse

When moving from the manufacturing plant to a warehouse, primary packaging such as bottles, jars, tubes and other forms of primary packaging need to be protected from damage that might occur during this phase of distribution. At this point, they are usually packaged in case lots. Handling with care is more easily accomplished in this environment, because the cases that comprise a given shipment are usually placed on a pallet, and the pallet is placed in a truck or freight car by either a fork lift or other device for moving pallets. In addition, all the packages in a given case will be uniform in size thereby reducing the need for dunnage (packing material).

From Warehouse to Retail

The next step in a product’s trip to the retail shelf is more problematic, because retailers often order less than case lot quantities of individual products. Thus, a retailer may order six units of Product A, three units of Product B, and so on. Not only is the total order likely to be less than a case lot quantity, but the various products will probably be in different size packages. This is called a “pick and pack” order. For shipment, all the items in a “pick and pack” order are placed in a single corrugated container, the empty space in the container is filled with dunnage, the carton is sealed, and usually shipped by a carrier such as United Parcel Service.

Where Damage Happens

While many people in the packaging industry believe that the most severe handling occurs in the “pick and pack” environment, they often overlook the severity of the environment when pallets are transported over the road or by rail.

Some years ago I saw a brief film of the gyrations of a liquid laundry product that was at the top of a pallet stack in a unitized load. It is fair to say that the gyrations of the individual bottles reminded one of a manic dance. Even though the individual bottles were separated by corrugated partitions, they still managed to contact each other.

In this environment, the displacement caused by vibration is amplified at each level of the stack. Therefore, the movement of the individual packages will be greatest at the top of the stack.

In the “pick and pack” environment the corrugated containers may be palletized for inter-city transport, but for local delivery, the individual corrugated containers are not likely to be palletized. Rather, they will be placed on the floor or on shelves within a truck such as a step van. Because they have some freedom of movement, the individual containers in this environment are likely to be bounced from the floor or shelf as well as shaken in response to road conditions on the route traveled. In this environment, the package will experience vibration as well as impacts of significant magnitude.

Early Testing for Shipping Safety

When I first joined the cosmetics industry an “old timer” told me that when the company was small, and staff needed to ascertain whether or not the packaging was adequate, they would fill a case with the product, step into the back of an empty truck, and throw the case against the wall of the truck. If nothing broke, they considered the packaging to be satisfactory.

By the time I had joined the company, the method of testing had grown somewhat more sophisticated. In this scenario, either a case lot or a pallet load of a product would be prepared. This material would be shipped, usually by truck, to a company facility in another part of the country. Upon receipt at the remote facility, the package would be immediately returned to the manufacturing location by the same method of shipment. If the container arrived back at its origin with contents intact, the packaging was considered satisfactory. Yet, even though the test shipments were usually completed successfully, commercial shipments of finished goods were sometimes found to be damaged when they reach their final destination.

Variations Are Everywhere

Upon studying the causes for the disparity between the results of test shipments, and commercial shipments, it became apparent that even though the same method of shipment was used, two trips over the same route were likely to be significantly different in terms of the shock, vibration, temperature and humidity of the environment. Temperature and humidity are a function of the weather, which usually varies from day to day. Variations in the shock and vibration characteristics of different trips are a function of the condition of the truck’s tires, its springs, the road, the route, the speed, and where within the truck a given unit is located.

Rail shipments are also likely to vary depending on how the freight car is loaded, the condition of its springs and the rails over which it travels. Variations also occur as a result of the number of times a railcar is “humped.”“Humping” occurs when a train is being made up. Cars from various points of origin that are to proceed along a certain route toward a particular destination are made up into a single train. Cars are allowed to freely roll down a section of sloping track onto a section of horizontal track. The first car is permitted to roll until it comes to a stop. Succeeding cars roll until they impact the car before it. As a result of its mass and momentum, the moving car hits the stationary car already in place on the horizontal section of track. The impact of the moving car latches the coupling thereby adding a new car to the train.

The number of times a train stops and the position of a particular car within the line of cars also makes a difference. Also, when the locomotive of a very long train stops, the cars near the end of the train can continue to roll for almost one hundred yards before they suddenly come to a halt. This results from the fact that there is a certain amount of slack in the coupling of each car. By coming to a sudden stop, the cars near the back end of the train experience significantly greater impact loads than those near the front of the train.
Even a variation in the number of cases that are stacked one atop the other in a warehouse or in a truck, can make a difference in how the package performs.

Standardized Testing

As a result of all the possible conditions that might be encountered in moving and storing goods, several standardized tests were developed to help determine whether a given packaging system was rugged enough to make it to the consumer intact. Initially, there were two standardized tests that were widely used to determine whether a new package was capable of withstanding the rigors of the distribution environment. One of these tests was developed by the National Safe Transit Association (NSTA), now known as the International Safe Transit Association (ISTA). The other test addressed the requirements for rail shipment.

Until fairly recently, the NSTA (now ISTA) procedure required that a given box be subjected to vibration (usually at a single frequency) and then dropped from a specified height onto a hard surface a total of 10 times. In addition to being dropped onto each of its six faces, the container had to be dropped onto one corner, and three edges. Also until recently, Rule 41 of the Uniform Freight Classification provided a drop test method specifically for chinaware, earthenware and glassware. This test method also specified a series of 10 drops onto a hard surface. The Rule 41 test differs from the ISTA in that a corner drop is not required; instead, the container is dropped onto each of the eight flap edges (edges that join the vertical sides of the box with the top and bottom flaps that enable it to be closed). and onto its top and bottom faces.

In addition to those tests, the Amer­ican Society for Testing and Materials (ASTM) also developed standardized tests to simulate the distribution environment. These tests included inclined impact testing to simulate the effect of “humping” and some compressive tests to simulate the effect of stacking.

During the 1980’s, the ASTM Committee on Packaging undertook a bold initiative to unify the various test methods to make it easier for individual companies to tailor the test protocol to their specific needs.

The protocol that came out of this effort is identified as ASTM D-4169, Standard Practice for Performance Testing of Shipping Con­tainers and Systems. This protocol lists the tests that are appropriate for rail shipments, full truck load shipments, or less than truck load shipments.

One of the shortcomings of the old NSTA test was that it was usually performed at a single frequency and amplitude of vibration. Studies of the actual distribution environment quickly revealed that the vibratory input varied with respect to both amplitude and frequency. The methods developed by the ASTM Committee on Packaging provided for vibratory input at different levels of frequency and vibration, and even for vibration at natural and harmonic frequencies.

For those unfamiliar with the terms frequency and amplitude, perhaps the easiest analogy is that of a person standing at the outer edge of a diving board (over a filled swimming pool, of course). The person’s up and down movement on the board forces the board to move as well. Starting from rest and moving upward to the top of travel is the amplitude of input. The number of times in a second (or minute) that the person goes through one complete cycle is called the frequency.

In a single document, ASTM D-4169 provides for drop testing, inclined impact testing, compression testing, vibration testing that includes random vibration, and vibration at natural and harmonic frequencies. In recognition of the value of the ASTM D-4169 document, Rule 41 no longer specifies drop testing.

By selecting the appropriate tests and the appropriate level of severity, experience has shown that ASTM D-4169 is very accurate in predicting the performance of a given package in the distribution environment. The equipment required to perform some of these tests can be quite expensive. Before deciding to purchase this equipment, a cost/benefit study should be performed. When there is doubt regarding the wisdom of purchasing the needed equipment, there are independent laboratories that have already made the investment.

No matter which course is chosen, each new package/product combination should be tested to be sure that it reaches the retailer in pristine condition.