|Measuring Package Performance to Avoid Shipping Damage
by Alfred H. McKinlay
Many of us have received an eagerly awaited shipment, opened the package to find the contents damaged, and wondered, How in the world could anyone or anything do that to my item? The damage may have been caused by a rare catastrophic event during shipment, but more likely it happened because either (1) the shipper had not adequately packaged the item, or (2) the carrier had imposed excessive force en route.
Fortunately, ASTM Committee D10 on Packaging has developed a good way to determine what is adequate or excessive as specified in its standard D 4169, Practice for Performance Testing for Shipping Containers and Systems.
D 4169 furnishes packaging designers with a method for predicting the performance of new or redesigned packages when distributed by any mode of transport. It provides a uniform basis for evaluation in the laboratory by subjecting shipping containers to a test plan of anticipated hazard elements encountered in the distribution environment. Each hazard element is simulated by an ASTM test method, and a series of tests, specific to a particular type of distribution, are conducted in sequence with the packaging unopened for inspection until completion of testing. The package is then opened and a determination made concerning its performance have both contents and package emerged acceptably according to standardized criteria?
A Performance Standard
The performance approach has been practiced for many years in some technologies outside of packaging. It is a systematic way to 1) define the desired attributes of an item (i.e. packaged product), and 2) determine if it fulfills those requirements satisfactorily without regard to the specific materials used. Within the specified requirements of a performance standard, producers may use their ingenuity to produce a product that is both cost-effective and safe. There is general agreement within government and industry that performance standards are more likely to encourage innovative designs and less likely to restrain competitive product development than standards that specify materials or design methods.
In the early 1970s, the performance approach was being applied in a number of new fields and the late W.L. Bill Newman of General Electric began pushing for its application in packaging. When other organizations showed little interest in doing so, Newman used his position as the chairman of Committee D10 in 1973 to form a task group for developing a performance standard for shipping containers and systems. It turned out to be the most momentous task ever undertaken by D10, finally achieving full approval as D 4169 in 1982 due in no small part to task group co-leaders Fred Ostrem and W. D. Dunc Godshall. The contentious debates on test levels at times reached great heights of fervor, but eventually the co-leaders were able to achieve acceptance of a standard that is truly a product of the consensus process. A landmark technical report authored by Ostrem and Godshall in 1979, FPL 22 An Assessment of the Common Carrier Environment, provided much of the background for determining test levels in D 4169.
Packaging Problems Solved
Prior to the availability of D 4169, if any testing was performed, packaging designers typically followed one or more standard test methods to check the strength, durability and protective capability of the package they were developing. Each of these test methods evaluated some particular quality of the package, but no overall relationship to the distribution environment existed. Testing parameters such as intensity or duration were often at significantly higher levels than expected in actual shipments, and new package specimens were used for each test. Positive results indicated a package with good integrity for the test it had passed, but no assurance that it would perform well when exposed to all major hazards in distribution.
A more dire situation was the usual practice of not testing packages at all as shippers relied on abbreviated transportation rules that in most cases specify minimum container strength only and no details on interior protective packaging. Unfortunately this situation still exists, but the advent of D 4169 presents packaging designers with the opportunity to do their job right by checking expected performance in the lab before shipping out.
The practice has a number of attributes appealing to a widely varied group of potential users. Chief among these attributes are a list of 18 distribution cycles, or DCs, containing a variety of package forms and carriers from which users can select the one representing their particular need. There are DCs for truck, rail, air, export, import and even specialized military requirements. Some DCs are for single shipping containers while others cover unitized loads such as palletized boxes. All DCs utilize standard ASTM test methods as the basis of test schedules that simulate specific hazard elements such as rough handling, vibration or warehouse stacking. A sequence of test schedules make up the test plan for each DC. For instance, the test plan for DC 8, Rail only, unitized, requires handling tests, random vibration, horizontal impact tests, more handling tests, and a compression test. These tests and others included in the practice represent the seven major hazards in distribution rough handling, warehouse stacking, in-transit stacking, vehicle vibration, loose load vibration, rail switching, and ambient conditions of temperature and humidity.
Another unique feature of D 4169 is its flexibility in determining test intensity. There are three levels available for all test methods based on the assurance level one wants to achieve in package performance. For an average level of assurance, one may use Level II with medium test intensities; for highest level of assurance, Level I; and for the lowest level of assurance, Level III. The level selected is based on product value and end-use, desired level of anticipated damage that can be tolerated, number of units to be shipped, knowledge of the distribution environment, or other criteria. Level II is used by most companies for most goods while manufacturers of such products as high value items or critical care products like medical devices may select Level I for the highest assurance that their packaged product will arrive undamaged. There is undoubtedly a higher cost of packaging incurred to meet the requirements of Level I, but the higher assurance of acceptable performance is deemed worth the added cost.
Even further flexibility in application of D 4169 is available when users develop a good understanding of their distribution systems, but find that it is not truly represented by any of the standard distribution cycles. The user may then select DC 2, Specially Defined Distribution System, User Specified, to develop a test plan reflecting the features of their unique distribution system. With DC 2 the user may arrange test schedules for hazard elements in sequence as expected in the users distribution system, vary assurance levels between test schedules for each hazard element to be simulated, and modify test levels and other details within a test schedule when experience has shown it more accurately correlates with actual experience. The end result of applying a high level of understanding of ones distribution in conjunction with the unique attributes of DC 2 should be packaging that performs exactly as desired in shipping and handling, with a minimum of damage incurred and lower material costs.
D 4169 has been rigorously analyzed ever since it was approved over 20 years ago, and has occupied a fixed location on every D10 meeting agenda since. Currently, the addition of several new hazard elements are being considered, including high altitude simulation, and a radical change to the existing small package distribution cycle is under way. The standard won the ASTM Dudley Medal in 1995 and promises to continue for the foreseeable future as Committee D10s most prestigious standard. //
Case Study: Use of D 4169
The following shows how D 4169 performance tests are applied to measure the adequacy of packaging for a consumer product. In this example, products have been incurring excessive damage on corners and edges in truck shipments directly from the manufacturers distribution center to customer homes. Impact testing via free falls from expected drop heights have not indicated any damage.
The manufacturer implemented a study of the shipping and handling environment, including the use of small electronic recording instruments within packages during trial shipments. Results of the study indicated some higher impacts (42-in [1070 mm] equivalent drop height) than normally expected for the 33-pound [15 kg] package and a number of lower impacts. There were no reported instances of containers crushed due to excessive compressive force, and orientation during shipment was almost always upright.
Upon comparison of recorded information versus distribution cycles in D 4169, it was noted that test schedules in standard distribution cycles did not reflect the same information as recorded during the study. The decision was then made to employ DC 2, specially defined environment, user specified, and develop a test plan similar to DC 3, single package by truck, up to 100 pounds [45 kg], but modified by the recorded information. The following sequence of tests was produced to simulate the hazards as recorded in actual shipments.
Handling at shipping dock and initial carrier terminals Free-fall drop tests using ASTM D 5276, Test Method for Drop Test of Loaded Containers by Free Fall: drop from 21 inches [530 mm] in six different orientations (Figure 1).
Stacking in carrier trailers during transportation Compression machine test using ASTM D 642, Test Method for Determining Compressive Resistance of Shipping Containers, Components, and Unit Loads: apply force up to pre-calculated load of 760 pounds [345 kg] (Figure 2).
Loose load vibration during transportation Repetitive shock test using ASTM D 999, Methods for Vibration Testing of Shipping Containers, method A2 (rotary motion): 40 minutes in normal vertical orientation (Figure 3).
Vehicle vibration during transportation Random vibration test using ASTM D 4728, Test Method for Random Vibration Testing of Shipping Containers: 180 minutes in normal vertical orientation, truck PSD profile, overall level 0.52 g rms [5.1 m/s2] (Figure 4).
Handling at final carrier terminal and delivery to customer home Free-fall drop tests using ASTM D 5276: drop from 21 inches [530 mm] in five different orientations; drop from 42 inches [1070 mm] on the most damage-prone corner or edge (Figure 1).
Copyright 2004, ASTM International