HP COMPRESSION TEST METHOD A Rev. A

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Sherilyn Goodman
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1 1. SCOPE HP COMPRESSION TEST METHOD A Rev. A This Standard describes the methods and specifications for compression testing of shipping containers, both empty and filled with product. 2. PURPOSE The purpose of this testing is two fold: a. It can be used as a quality control check for corrugated shipping containers. Instead of specifying corrugated materials (specs which can rarely be tested), performance level specifications can be developed and placed onto drawings. Requiring vendors to conduct compression testing on shipping cartons will provide a method of judging the combined quality of materials and construction of a container. Recording test results over time should provide expected control limits for container strength and provide a good baseline for material or design modifications. b. The test method should provide an accurate way of assessing the overall strength of a filled container and determining if the product/package will survive the compression loads expected within distribution. This method can also be used to test loading points of unboxed products. This will be useful where the compression load is transmitted to the product via packaging. When the inherent strength characteristics of the product can be harnessed to survive the rigors of distribution, packaging costs can decrease. 3. DAMAGE When conducting compression testing, failure can be defined in a number of ways. The two quantitative factors being measured in compression testing are load (lb. or kg) and deflection (in or mm). Following are parameters of compression failure which should all be weighed during testing: a. The peak load (lb. or kg) and the amount of deflection (in or mm) at that peak load. b. The amount of load at 0.5 in (12.7 mm) deflection. c. If desired, the amount of deflection allowable may be calculated to be some percentage of the overall height of the test specimen. d. If the package becomes cosmetically unacceptable, or there is damage to the product or its accessories, prior to the peak load or deflection described above, it is considered failure. 4. REFERENCED DOCUMENTS ASTM D ASTM D Appendix B - Page: 1 of 5

2 5. SPECIFICATIONS All testing should continue until failure. To determine the amount of load carrying capacity of a shipping container, one should know the warehousing and vehicle stacking heights encountered in the distribution system. Usually there will be a higher stacking height in storage than in transit. For instance, HP commonly stacks 80 in (2032 mm) pallet loads two high. Unless the Packaging Engineer knows of another specific maximum stack height within their product's distribution system, it is recommended that a packaged product be able to support loads stacked to 160 in (4064 mm). Be sure to add the weight of the pallets in calculating the total load. This calculated dead load is the first step in determining the actual strength of the packaged product. The strength of a corrugated box can be altered drastically throughout distribution. Corrugated board cannot be considered an engineering material due to the fact that its strength characteristics are not predictable within its normal range of use. Humidity and temperature changes affect corrugated greatly. Drops, vibration, compression, and printing all reduce the strength of flute structure. Misalignment of vertical edges from one box on top of another can reduce carrying capacity up to 50%. Because of all these things, it is common to use a "safety factor" when calculating the needed compression strength of a corrugated box. The safety factor is a multiplier by which the calculated dead load is increased to makeup for the hazards of distribution which impair the strength of corrugated board. If the shipping container were made of a material whose strength was not compromised by its environment, such a safety factor would not be necessary. Likewise, if all the compression load were transmitted directly into the product (i.e., cans of pop in a corrugated tray), the safety factor would not be needed. But, if any amount of compression load is to be supported by the box, then a safety factor should be used. ASTM recommends safety factors ranging from 1.5 to 8.0, depending upon the value of the product and percentage of load supported by corrugated. Experience has shown that a safety factor of about five seems right for corrugated boxes and corrugated inserts supporting the majority of compression load. If the interior packaging is non-humidity sensitive and helps support load, along with the product, this safety factor can be minimized. 6. TEST EQUIPMENT (1) It is highly recommended to conduct compression testing in an environmentally controlled room of fixed air temperature and humidity. Ideally, corrugated samples will first be dried in a hot room, removing most of the moisture in the board. Then, for 24 hours, it should be exposed to /- 2.0% relative humidity and /- 2.0 degrees F (23.0 +/- 1.0 degrees C). Using these conditions will permit remote laboratory comparisons and consistency over time and seasons. (2) There are two common types of compression testers: fixed platen and floating platen. The fixed platen type has two metal platens which remain parallel to each other throughout the test. The floating platen variety has one platen rigidly restrained while the other platen is universally mounted and allowed to tilt freely. The floating platen machine has two parallel platens, flat to within 0.02 in (0.5 mm), one which is moveable in the vertical direction so as to compress the specimen between the platens. One is the load measuring platen, and both are of sufficient size so that the test container does not extend beyond the edges of the platens. One platen is fixed in Appendix B - Page: 2 of 5

3 the horizontal direction so as to have no lateral movement greater than 0.05 in (1.3 mm). The second platen is attached to the machine by a swivel or universal joint directly centered on the platen, thus allowing the platen to tilt freely. It is believed that floating platen testing identifies and measures the weakest part of a container while fixed platen testing measures the strongest aspect. Depending upon the design of the tester, as much as a 19% difference may exist between the results of a fixed platen compared to a floating platen. Since it is the weakest aspect of a box which will fail first in stacking, it is recommended that a floating platen tester be used. (3) Common Features of a Compression Test Machine a. Each machine should have a means of driving the moveable platen at a uniform speed of 0.5 +/ in/min. (12.0 +/- 2.5 mm/min.). b. Each machine should have a means of recording or indicating the applied load to within +/- 0.5% of the scale capacity. NOTE: the tolerance is based upon the scale capacity, not the actual test reading. For example, a 2000 lb. scale capacity is used and a box tests to 670 lb. The actual strength of that box is 670 +/- 10 lb. c. Each machine should have a means of recording or indicating the resultant deformation within +/ in (+/ mm). 7. SAMPLING, TEST SPECIMENS, AND TEST UNITS Test specimens and sample quantities should be chosen to provide an adequate determination of representative performance. For large production runs, lot sampling is advised. It is recommended that five or more replicate tests be conducted to improve the statistical reliability of the data obtained. The test specimen should be closed and secured in the same manner as will be used in preparing them for shipment, unless otherwise specified. 8. PROCEDURE Center the specimen on the bottom platen of the testing machine. Lower the top platen until it comes in contact with the specimen. For single wall corrugated, apply an initial pressure, or preload, of 50 lbf (222 N) to ensure a definite contact between the specimen and the platens. For double wall, apply 100 lbf (445 N). At this time, record the distance between the platens as zero deformation. Apply the load with a continuous motion of the moveable head of the testing machine at a speed of 0.5 +/- 0.1 in/min. (12.7 +/- 2.5 mm/min.), until failure, as defined above, has been reached. Usually, the greatest compression forces within distribution will be exerted while the product is in palletized form. Therefore, it is recommended that boxes be tested in their pallet orientation. NOTE: When testing full containers, and the load sensing device is located under the bottom platen, be sure to zero the test machine with the product on it, or subtract the container weight from peak load readings. Appendix B - Page: 3 of 5

4 Strength Calculation The determination of what amount of compression force a shipping container will have to endure in the warehouse and shipping environment is the basis of this guideline. This section will cover two methods for determining this. Safety Factors There are many elements that effect the structural strength of a corrugated container from raw material to used carton. The elements are humidity, temperature, printing, handling, storage conditions, and time. These factors reduce the strength of the material and must be taken into consideration when calculating the required strength needed when conducting compression tests. The term used to describe this is "safety factor". A safety factor is used as a multiplier in the calculation to makeup what the elements of the distribution environment take away. Methods for Determining Test Levels The first method can be seen in ASTM D-4169 section The second method is more simplistic but obtains nearly the same results. Appendix B - Page: 4 of 5

5 The third method is using Edge Crush Test (ECT) calculation. USING ECT Formula for Calculating Corrugated Box Compression Strength (developed by Institute of Paper Chemistry in 1963) COMPRESSION STRENGTH = (5.87)x(ECT) (Box Perimeter)x(Board Thickness) Where ECT = Edgewise crush or short column test, pounds/inch Box perimeter = 2 x inside length + 2 x inside width, inches Board Thickness = overall thickness of linerboards and corrugated medium, inches and box shape is regular, ie. style ie. RSC, depth is at least 1/7 of box perimeter (2L + 2W), and no dimension is more than twice any other. Example How high can an RSC style corrugated box be safely stacked in a warehouse if it (not contents) must carry entire load? Given: Gross weight - 32 pounds; inside dimensions-18" x 12" x 10"; board - "C" flute, 200 psi burst, 40 pounds/inch ECT, thickness of 0.160". Use a design or safety factor of 4.5 since conditions are average Calculations Compression Strength = (5.87)x(40) (60)x(.160) Safe load on box = 728#/4.5 = 162 pounds Safe number of boxes to stack on bottom box = = 5 Total stack height = Bottom 1 plus 5 on top = 6 Appendix B - Page: 5 of 5

Standard Test Method for Determining Compressive Resistance of Shipping Containers, Components, and Unit Loads 1

Designation: D 642 00 (Reapproved 2005) Standard Test Method for Determining Compressive Resistance of Shipping Containers, Components, and Unit Loads 1 This standard is issued under the fixed designation