package performance testing of dangerous goods in high-altitude shipments

INTRODUCTION

The Federal Aviation Administration (FAA) hasobserved an increase in the number of packagefailures of dangerous goods (DG) in commercialand cargo aircraft over the past 3 years.1,2 It is notclear whether this increase is due to more actualfailures or the FAA’s increased inspection andenforcement efforts following the ValuJet incident.Figure 1 shows the different classifications of prod-ucts that had package-related failures. Table 1shows the cause of failure by package type. Forplastic and metal packages, failure of the closure/seal accounted for about 65% of failures. For glasscontainers, drops account for about half, with sealfailures down to 23%.

In addition to the above findings, the UnitedParcel Service presented a study to the AmericanSociety of Testing and Materials (ASTM) describ-ing the conditions that packages experience in the

single parcel shipping environment.3 The studyresulted in the following key observations asdescribed in ASTM D6653-01:

• Cargo air jets are typically pressurized to about75kPa, which is normal atmospheric pressure atan altitude of 2438m (8000ft). Temperature ismaintained at approximately 20–23°C (68–74°F)

• Packages transported on the ground may expe-rience altitudes as high as 3658m (12000ft)when shipped over certain mountain passes,especially in Colorado. Temperature extremesrange from -15 to 30°C (5–86°F) with averagetemperatures ranging from -4 to 18°C (25–64°F)

• Non-pressurized ‘feeder aircraft’ typically fly at approximately 3963–4877m (13000–16000ft). The highest recorded altitude in a non-pressurized feeder aircraft was 6017m (19740ft). Temperatures ranged from approximately -4 to 24°C (25–75°F).

PACKAGING TECHNOLOGY AND SCIENCEPackag. Technol. Sci. 2003; 16: 119–130DOI:10.1002/pts.619

Package Performance Testing of DangerousGoods in High-altitude Shipments

By S. Paul Singh, Gary J. Burgess and Jagjit SinghSchool of Packaging, Michigan State University, East Lansing, MI 48824, USA

This paper discusses the impact of high-altitude shipments on package integrity.High-altitude shipments are encountered when trucks travel over high mountainpasses or when cargo and feeder aircraft transport packages in non-pressurized orpartially-pressurized cargo holds. Both these types of transport methods will resultin severe changes in pressure as compared to packages being transported close tosea level. The testing of packages under these conditions is critical since packageintegrity may be compromised. The current shipping tests performed in testlaboratories do not account for pressure changes and vibration together. This studyshowed that combination packages for dangerous goods and hazardous materialsthat are tested to existing UN, ICAO and US DOT requirements are limited, andcan result in significant number of leaks. Testing under combined vibration andpressure changes is necessary. Copyright © 2003 John Wiley & Sons, Ltd.Received 24 March 2003; Revised 13 June 2003; Accepted 11 July 2003

KEYWORDS: packaging; air transport; dangerous goods; high altitude; leaks; torque; testing

* Correspondence to: S. P. Singh, 130 Packaging Building, Michigan State University, East Lansing, MI 48824-1223, USA.Email: [email protected]

Copyright © 2003 John Wiley & Sons, Ltd.

Based on these findings, it is evident that pack-aged products transported by the feeder aircraftnetwork used by cargo carriers like United ParcelService, Federal Express and the US Postal Serviceare liable to experience altitudes as high as 6100m(20000ft). Packages transported on the groundmay experience altitudes as high as 3658m (12000ft) when shipped over mountain passes inthe USA. When exposed to these conditions, prod-ucts and/or packages may be adversely affectedby the changes in pressure and temperature.

In an attempt to create a laboratory test methodthat replicates the environment, ASTM developedand approved a new test method, D6653-01,4 Stan-dard Test Method for Determining the Effects of High

Altitude on Packaging Systems by Vacuum Method.The test method recommends that the package be subjected to a reduced pressure of 59.5kPa, representing an altitude of 4267m (14000ft) for 60min. There are other test methods used by Depart-ment of Transportation (DOT) and InternationalCivil Aviation Organization (ICAO). The problemwith all of these existing test methods is that theydo not consider the combined effects of pressure,temperature and vibration. The existing DOT spec-ification for shipping and handling dangerousgoods containers requires that the packages areplaced with the closure facing up at all times.However, we have a real concern, shared by theFederal Aviation Adminstration (FAA), that a pro-

S. P. SINGH, G. J. BURGESS AND J. SINGHPackaging Technologyand Science

Copyright © 2003 John Wiley & Sons, Ltd. 120 Packag. Technol. Sci. 2003; 16, 119–130

DANGEROUS GOODS AIR ACCIDENTS BY HAZARD CLASS -1999

TOTAL OF 583 INCIDENTS

CLASS 92%

37 TOTAL

CONSUMER COMMODITY5%

73 TOTAL

CLASS 820%

312 TOTAL

CLASS 7<1%

5 TOTAL

CLASS 41%

14 TOTAL

CLASS 65%

79 TOTAL CLASS 51%

19 TOTAL

CLASS 1<1%

10 TOTALCLASS 2

6%88 TOTAL

CLASS 3 60%

946 TOTAL

Figure 1. Dangerous goods air accidents by hazard class, 1999.Source: FAA, Office of Aviation Security.

Table 1. Factors contributing to combination packaging failures

Packaging Seal Inner Fork Other Possibletype closure Unknown broken Punctured lift Seam freight Chime Drop drop Total

Plastic/4G 65% 3% 1% 2% 3% 0 5% 0 9% 12% 100%111 5 2 4 6 8 16 20 172

Metal/4G 66% 4% 0 4% 6% 4% 0 0 7% 7% 100%44 3 3 4 3 5 5 67

Glass/4G 23% 6% 17% 0 5% 0 1% 0% 22% 25% 100%15 4 11 3 1 14 16 64

Unknown/4G 27% 33% 0 0 13% 0 7% 0 13% 7% 100%8 10 4 2 4 2 30

Source: FAA, Office of Aviation Security.

portion of the reported leakers, especially those insmaller combination packages, could be the resultof packs being shipped in adverse orientations,where the combined effects of the transport envi-ronment, low pressure and the adverse orientationcause leaks to occur. Previous studies5,6 show aclear indication that single parcels get exposed toimpacts and vibrations in all orientations duringhandling, sorting and transportation, includingthose with designated shipping orientations. Airshipments are generally ‘cubed out’ and there-fore packages are placed in the orientation mostlikely to provide the highest volume efficiency; webelieve it likely that individual smaller combina-tion packages will be at risk of being treated in thisway. This scenario certainly provides an explana-tion for problems with validated packs in real-lifeshipments.

The purpose of this study was to investigate the effects of vibration alone, altitude alone, andvibration in combination with altitude on the performance of UN-approved dangerous goodspackages containing liquids placed in the side-ways and upside-down orientations. Temperatureeffects were not considered because the shippingtemperatures found in the UPS study (25–75°F)were not significant. Since lowering the tem-perature of a test package acts to reduce the headspace air pressure, which lowers the pressuredifferential and makes altitude effects less severe,testing was done at room temperature to incor-porate a small safety factor. Testing was done infive phases. Each test phase represents different combinations of low pressure and vibration towhich packages are likely to be exposed duringhigh-altitude shipments. Based on the results, anew test method will be proposed to ASTM for thetesting of packages that undergo high-altitudeshipments.

MATERIALS AND TEST METHODS

Samples of UN-approved DG packages were pro-cured by Michigan State University from threeleading DG packaging suppliers. The test packageswere certified to meet both the UN/ICAO andapplicable US DOT requirements. The confiden-tiality of the package suppliers was maintained forthe study at the request of the sponsoring agencies.Table 2 shows package types tested during the dif-ferent phases of the study. The DG packagesranged in capacity from 4oz to 0.5 gallons (0.12–1.9 l). In addition to these DG packages, two testpackages were prepared that consisted of glass testtubes with rubber stoppers. PACK 1 and PACK 2are glass test tubes with rubber stoppers, butPACK 1 has tape wrapped around the stopper andtest tube in the neck area. These were tested toaddress concerns over ‘friction-type’ closures. Thetest tubes hold approximately 10ml of liquids.

When performing vibration tests, a decisionmust be made regarding the severity of the environment. ASTM D 41697 describes three different test levels (Assurance Levels I, II and III)for evaluating shipping container performance.These test levels are related to uncertainties inenvironmental conditions. Assurance Level I corresponds to a high level of abuse, but has a lowprobability of occurrence. This leads many peopleto consider Assurance Level I as conservative, withplenty of safety factor built in. Upon consultationwith the FAA and DOT, and from past experienceswith various tests, a decision was made to useAssurance Level II for this project. Assurance levelII is also the most commonly used test level bytesting facilities. The five test phases are describedbelow.


IMPACT OF HIGH-ALTITUDE SHIPMENTS ON PACKAGE Packaging Technologyand Science

Table 2. Packages tested

Supplier UN numbers for combination packages tested

1 HMS-08, UN950PPT, UN950GPT, UN16FFPS, UN32FFPS, UNHWS16, UN32NPVB, HMSP-32N, UN32PPS,UN4FFPS, UAC32FPS, UN32FAPS

2 UNE151, UN112, UN1541, UN61, UN62, UNIS80, UN51, UN52, UN78, UN793 CT-SP-0002, CT-1-92-1000N, CT-1-92-1000-N,V1-0125-N,V1-0500N,V1-1000N,V1-0500W

Phase I: truck/air vibration and vacuum at 4267m (14000ft)

This test was designed to replicate feeder aircraftand high altitude ground shipments as closely aspossible in a single test. It consisted of simultane-ous low pressure representing an altitude of 4267m (14000ft) and random vibration using combinedtruck/air power spectral density (PSD) data.Figure 2 shows the test set-up. The four legs of therigid steel vacuum chamber were bolted to thevibration table to form a direct coupling of the two,so that the vibration environment inside thechamber was the same as the vibration table itself.The vacuum pump motor was placed near thevibration table. Packages were conditioned atASTM standard conditions of 73.4 ± 3.6°F for aminimum of 24h before testing. The test procedurewas as follows:

• The primary containers were filled to the rec-ommended fill-level with water and the recom-mended application torque was applied to theclosure.

• Secondary packaging was applied, as if prepar-ing for shipment, in accordance with the manu-facturer’s instructions.

• Two samples of each stock-keeping unit (SKU)were used for this phase.

• The test specimen was placed upside down inthe vacuum chamber and the vacuum chamberwas placed on an electro-hydraulic vibrationtable.

• After sealing the vacuum chamber, the vacuumpump was turned on and adjusted to reduce thepressure at a rate of 305m (1000ft) in 30–60s, asrecommended in ASTM D6653-01. This repli-cates normal take-off conditions on an airplane.

• A vacuum of 59.5kPa (pressure equivalent of 14000 feet or 4267m) was achieved with a per-missible error of ±2%.

• While maintaining a vacuum of 59.5kPa, thevibration table was operated for 30min in therandom mode under the combined truck/airshipping environment (Assurance level II,ASTM D 4169), representing shipments of 250miles (400km).

• After 30min, the chamber inlet valve wasopened and the vacuum was released at a rateof 305m (1000ft) in 30–60s, simulating normaldescent conditions.

• The test specimen was removed and anyleakage was recorded.

• The closures were removed using a torque testerand the removal torques were measured andrecorded.

Some of the results of the Phase I test are shownin Figures 3–8 and Tables 3–5. Figures 3–4 showthat large closures had a greater tendency to leakcompared to smaller ones. Tables 3–5 show that 15of 32 packages tested leaked. Both friction-typeclosures failed.

Phase II: truck/air vibration only

The purpose of this test was to remove the pres-sure differential in order to study the effect ofvibration only. So the test procedure was exactly



Figure 2. Experimental set-up for Phase I.

Figure 3. Closures that failed.

the same as in Phase I but with the vacuumchamber steps omitted. An additional step notdone in Phase I was to place alignment marks onthe container and closure to see if the closures werebacking off. This was not found in any of the tests,including Phases III–V that follow, probablybecause tape was applied around the closure afterit was torqued on, as recommended by the manu-facturer. Only packages shown in Table 3 weretested in this phase and the test phases that follow.The results of the Phase II tests are shown in Table6. There were only two leakers of the 14 tested,compared to seven of the same 14 in Phase I (Table3). Only one of the friction-type closures failed,



Figure 4. Closures that passed.

Figure 5. Phase I, UNHWS16.

Figure 7. Phase I, UN32PPS.

Figure 8. Phase I, CT-SP-0002.

Figure 6. Phase I, UNHWS16.



Table 4. Results for Phase I, Supplier 2

Phase I

Sample A Sample B

AT RT AT RT

Stock-keeping units N/m lb/in N/m lb/in N/m lb/in N/m lb/in

UNE151 1.25 11.1 0.81 7.2 1.25 11.1 0.82 7.3UN112 2.27L 20.1L 2.07L 18.3L 2.29 20.3 2.12 18.8UN1541 1.29 11.4 0.73 6.5 1.26 11.2 0.80 7.1UN61 2.27 20.1 1.96 17.4 2.27 20.1 2.09 18.5UN 62 6.33 56.1 5.32 47.1 6.39L 56.6L 5.07L 44.9L

UNIS80 4.00L 35.4L 3.35L 29.7L 4.02 35.6 3.65 32.3UN51 1.28 11.3 0.95 8.4 1.26 11.2 0.68 6.0UN52 1.82 16.1 1.70 15.1 1.82 16.1 1.51 13.4UN78 3.96L 35.1L 3.48L 30.8L 3.96L 35.1L 3.62L 32.1L

UN79 3.96 35.1 3.59 31.8 3.99L 35.3L 3.70L 32.8L

AT, application torque; RT, removal torque. LLeakers.


Phase I

Sample A Sample B

AT RT AT RT


HMS-08 2.39L 21.2L 2.18L 19.3L 2.44L 21.6L 1.86L 16.5L

UN950PPT 2.27 20.1 1.75 15.5 2.26 20.0 1.85 16.4UN950GPT 1.26L 11.2L 1.24L 11.0L 1.25 11.1 0.91 8.1UN16FFPS 1.26 11.2 1.13 10.0 1.25 11.1 0.99 8.8UN32FFPS 1.84 16.3 1.45 12.8 1.84 16.3 1.46 12.9UNHWS16 3.97L 35.2L 3.56L 31.5L 3.96L 35.1L 2.50L 22.1L

UN32NPVB 6.32 56.0 4.03 35.7 6.37 56.4 3.68 32.6HMSP-32N 2.04 18.1 1.51 13.4 2.05 18.2 1.65 14.6UN32PPS 2.27 20.1 2.21 19.6 2.27L 20.1L 2.16L 19.1L

UN4FFPS 1.25 11.1 1.12 9.9 1.28 11.3 1.04 9.2UAC32FPS 1.81 16.0 1.78 15.8 1.82 16.1 1.60 14.2UN32FAPS 1.26 11.2 1.04 9.2 1.28L 11.3L 0.85L 7.5L

PACK 1 L L L L L L L L

PACK 2 L L L L L L L L

AT,Application torque; RT, removal torque. L Leakers.




Phase I

Sample A Sample B

AT RT AT RT


CT-SP-0002 2.39 21.2 2.17 19.2 2.39 21.2 2.24 19.8CT-1-92-1000-N 3.77 33.4 2.31 20.5 3.79 33.6 2.44 21.6CT-1-92-1000-W 6.34L 56.2L 3.65L 32.3L 6.45 57.1 4.14 36.7CT-4-92-1000-N 3.74 33.1 2.04 18.1 3.75L 33.2L 1.89L 16.7L

V1-0125-N 1.30 11.5 1.12 9.9 1.25 11.1 1.04 9.2V1-0500N 1.29 11.4 1.11 9.8 1.25 11.1 1.04 9.2V1-1000N 2.30 20.4 1.19 10.5 2.27 20.1 1.65 14.6V1-0500W 3.97L 35.2L 3.18L 28.2L 3.99L 35.3L 2.57L 22.8L


Table 6. Results for Phase II

Phase II

Sample A Sample B

AT RT AT RT


HMS-08 2.38 21.1 2.24 19.8 2.39 21.2 2.20 19.5UN950PPT 2.31 20.5 2.05 18.2 2.31 20.5 2.13 18.9UN950GPT 1.28 11.3 1.22 10.8 1.26 11.2 1.15 10.2UN16FFPS 1.25 11.1 1.11 9.8 1.25 11.1 1.07 9.5UN32FFPS 1.82 16.1 1.56 13.8 1.81 16.0 1.52 13.5UNHWS16 3.99 35.3 3.13 27.7 3.96 35.1 3.51 31.1UN32NPVB 6.40 56.7 5.04 44.6 6.36 56.3 5.39 47.7HMSP-32N 2.07 18.3 1.81 16.0 2.07 18.3 1.65 14.6UN32PPS 2.26L 20.0L 2.00L 17.7L 2.29 20.3 2.00 17.7UN4FFPS 1.25 11.1 1.16 10.3 1.30 11.5 1.14 10.1UAC32FPS 1.81 16.0 1.49 13.2 1.82 16.1 1.55 13.7UN32FAPS 1.25 11.1 1.15 10.2 1.26 11.2 1.11 9.8PACK 1 L L L L L L L L

PACK 2


compared to two in Phase I. These results clearlyshow the influence of pressure differential.

Phase III: vacuum only at 4267m (14000ft)

The purpose of this test was to remove vibrationin order to study the effect of pressure differentialonly. So the test procedure was exactly the same as in Phase I, but with vibration-related stepsomitted. The results are shown in Table 7. Therewere no leakers, indicating that vibration is a nec-essary component for failure.

Phase IV: truck/air vibration andvacuum at 2438m (8000ft)

The purpose of this test was to subject the testpackage to lower altitudes, but for longer times inorder to recreate the environments found in pres-surized cargo holds of large commercial aircraft onlong flights. The procedure was the same as inPhase I, except that the test pressure was 75.3kPa

instead of 59.5kPa, simulating 8000ft (2438m)instead of 14000ft. (4267m). In addition, the vibra-tion table was operated for 3h instead of 30min, asrecommended in ASTM D4169. The results areshown in Table 8. There were four leakers of 14tested. These results are between those of Phase I(seven of 14) and Phase II (two of 14), which hadthe same vibration environment but with lowerand higher pressures, respectively. Test time doesnot appear to influence the results as much as testpressure.

Phase V: truck vibration only andvacuum at 2438m (8000ft)

The purpose of this test was to remove the airtransport PSD data from the vibration test spec-trum to see if there was any difference in pureground transport and combined ground/air trans-port, both at 8000ft (2438m). So the test procedurewas exactly the same as in Phase IV, but with onlythe truck PSD data. The results are shown in Table9. There were three leakers of 14, one less than inPhase IV and one more than Phase II.



Table 7. Results for Phase III

Phase III

Sample A Sample B

AT RT AT RT


HMS-08 2.39 21.2 2.07 18.3 2.39 21.2 1.92 17.0UN950PPT 2.26 20.0 2.01 17.8 2.27 20.1 1.94 17.2UN950GPT 1.25 11.1 1.15 10.2 1.26 11.2 1.21 10.7UN16FFPS 1.25 11.1 0.99 8.8 1.25 11.1 1.04 9.2UN32FFPS 1.84 16.3 1.60 14.2 1.81 16.0 1.67 14.8UNHWS16 4.01 35.5 3.24 28.7 4.01 35.5 3.61 32.0UN32NPVB 6.33 56.1 4.55 40.3 6.36 56.3 5.20 46.1HMSP-32N 2.04 18.1 1.59 14.1 2.03 18.0 1.54 13.6UN32PPS 2.28 20.2 2.00 17.7 2.27 20.1 2.00 17.7UN4FFPS 1.25 11.1 1.23 10.9 1.26 11.2 1.24 11.0UAC32FPS 1.81 16.0 1.78 15.8 1.82 16.1 1.72 15.2UN32FAPS 1.25 11.1 1.22 10.8 1.25 11.1 1.23 10.9PACK 1PACK 2




Table 8. Results for Phase IV

Phase IV

Sample A Sample B

AT RT AT RT


HMS-08 2.39 21.2 2.21 19.6 2.44 21.6 2.09 18.5UN950PPT 2.27L 20.1L 2.10L 18.6L 2.29 20.3 2.24 19.8UN950GPT 1.26L 11.2L 0.41L 3.6L 1.25 11.1 1.04 9.2UN16FFPS 1.30 11.5 1.24 11.0 1.28 11.3 1.23 10.9UN32FFPS 1.82 16.1 1.78 15.8 1.85 16.4 1.74 15.4UNHWS16 3.97L 35.2L 3.18L 28.2L 4.02L 35.6L 3.61L 32.0L

UN32NPVB 6.34 56.2 4.02 35.6 6.32 56.0 4.34 38.4HMSP-32N 2.04 18.1 1.51 13.4 2.03 18.0 1.38 12.2UN32PPS 2.29 20.3 2.24 19.8 2.26 20.0 1.90 16.8UN4FFPS 1.25 11.1 1.23 10.9 1.26 11.2 1.16 10.3UAC32FPS 1.82 16.1 1.60 14.2 1.83 16.2 1.41 12.5UN32FAPS 1.26 11.2 1.23 10.9 1.28 11.3 1.22 10.8PACK 1PACK 2 L L L L L L L L


Table 9. Results for Phase V

Phase V

Sample A Sample B

AT RT AT RT


HMS-08 2.38L 21.1L 1.95L 17.3L 2.38 21.1 1.78 15.8UN950PPT 2.26 20.0 1.98 17.5 2.29 20.3 1.85 16.4UN950GPT 1.25 11.1 1.22 10.8 1.24 11.0 1.15 10.2UN16FFPS 1.25 11.1 1.15 10.2 1.26 11.2 1.19 10.5UN32FFPS 1.81 16.0 1.67 14.8 1.82 16.1 1.72 15.2UNHWS16 3.96L 35.1L 3.56L 31.5L 3.97 35.2 3.40 30.1UN32NPVB 6.33 56.1 4.39 38.9 6.37 56.4 4.54 40.2HMSP-32N 2.03 18.0 1.61 14.3 2.07 18.3 1.90 16.8UN32PPS 2.29 20.3 1.94 17.2 2.30 20.4 2.12 18.8UN4FFPS 1.25 11.1 1.16 10.3 1.28 11.3 1.17 10.4UAC32FPS 1.81 16.0 1.64 14.5 1.83 16.2 1.69 15.0UN32FAPS 1.24 11.0 1.11 9.8 1.25 11.1 1.15 10.2PACK 1PACK 2 L L L L


DISCUSSION

Table 10 summarizes the results of the five differ-ent tests on the packages in Table 3. By comparingthe data in pairs of rows in Table 10 the followingconclusions were drawn. These conclusions are ofcourse biased toward the sample set of packagesstudied, but they are believed to be true of pack-ages in general.

• Vibration alone did produce leakers (2nd row inTable 10) but altitude alone did not (1st row).

• Altitude is much more important than test time(4th vs. 5th row).

• High altitude is much worse than low altitude(2nd vs. 5th row).

• Combined truck/air vibration is worse thantruck alone (3rd vs. 4th row).

• There is a significant interaction between alti-tude and vibration (5th row vs. 1st and 2ndrows).

The torque data in Tables 3–9 do not show anycorrelation between leakers and loss of applicationtorque. It is normal for the removal torque to besomewhat less than the application torque. It wasexpected, however, that leakers would be theresult of the cap backing off or the liner failing insome way, which would show up as an exagger-ated loss in torque, but this did not happen. Themechanism responsible for leaks must therefore besomething else.

The most likely cause of leaks is localized com-pression of the liner (Figure 9). When the containeris turned upside down and vibrated, it has a ten-

dency to tilt to one side and bounce up and downon the edge of the closure. In a typical truck loadthere are about five impacts.8 During each impact,the rim of the bottle is forced against the liner,causing it to compress more. Immediately afterimpact milliseconds later, the liner remains com-pressed for a while because it is made of a softinelastic material. So there is a period of timebetween impacts when there is a temporary loss ofsealing force. There may even be a sizeable gapbetween the liner and bottle. Since the liquid isalways in contact with the liner when the bottle isturned upside down or on its side, every impactrepresents an opportunity for a leak. Upright con-tainers can also leak if they bounce high enough tohit the top of the box, or if other packages bounceup and down on them. Even if no liquid leaks out,there may be a ‘vapour trail’ if the liquid is volatile.

The fact that large closures tend to leak morethan small ones is related to two independenteffects. The first is the pressure differential itself.As the external pressure is reduced, the air trappedinside the container finds it easier to push the capout. The force tending to push the closure off thecontainer is the area of the cap multiplied by thepressure differential. The area of the cap increasesas the square of the diameter, so doubling the capdiameter quadruples the force for a given pressuredifferential. Larger caps also tend to distort moreeasily. This, combined with the increased force, cancause the cap to ‘dome’, which in turn allows the



Table 10. Ranking of environments

Number of leakers out of Conditions 14 packages tested

No vibration, 14000 ft, 030min

Truck and air vibration, 20 ft, 30min

Truck only vibration, 38000 ft, 180min



Figure 9. Localized compression of the liner.

liner to raise up a little, making it easier for vibra-tion to create gaps between the liner and the rimof the container.

Large closures may also tend to leak morebecause of the US industry practice for specifyingapplication torques: the recommended applicationtorque in inch-lbs is half the diameter of the closurein millimeters.9 So a 1 inch (25.4mm) closurewould have an application torque of 12.7 in-lbs(1.44 N-m). The manufacturers’ recommendedapplication torques for the closures used in thisstudy appeared to follow this practice almostwithout exception. The problem with this rule isthat it leads to larger liners being compressed lessthan smaller ones, for the following reasons. Thesealing force, which is the force pressing the lineragainst the rim of the bottle is approximately:10

where S = seal force (lb or N), D = cap diameter (inor mm), T = application torque (in/lb or N/m) and

= average coefficient of static friction between allsliding surfaces (dimensionless).

A 1 inch (25.4mm) closure having a liner forwhich the coefficient of friction is 0.2 would there-fore have a seal force of 12.7/(0.2 ¥ 1.0) = 63.5 lb(282N), if the industry practice for the recom-mended application torque is followed. This sealforce was confirmed experimentally.10 Accordingto the formula, if the recommended applicationtorque is proportional to the diameter, then thesealing force becomes independent of the diame-ter. So following industry practice leads to thesame sealing force for all closure sizes, but this isnot what we want because the sealing force is dis-tributed around the rim of the container. The sameforce distributed over a larger perimeter reducesthe stress on the liner. Consequently, larger clo-sures compress the liner less. This makes it easierfor vibration to open up gaps.

CONCLUSIONS

The following conclusions can be drawn from theresults of this study:

1. The UN-approved DG packages tested did notprevent leaks under combined vacuum and

m

STD

=m

vibration characteristic of air and high-altitudeground shipments.

2. A pressure differential alone does not appear tocause leaks, but vibration alone can. Simultane-ous vibration and vacuum testing is thereforenecessary to recreate the shipping environ-ment for both air and high-altitude groundshipments.

3. Altitude is more important than test time,higher altitude is worse than lower altitude, andcombined truck/air vibration is worse thantruck alone.

4. There is a significant interaction between alti-tude and vibration. The combined effects of alti-tude and vibration produced far more leakersthan either altitude or vibration alone.

5. An increase in altitude affects larger caps morethan smaller ones because the pressure differ-ential acts over a greater area. The potential forleaks is greater for larger caps.

6. The effect of vibration is to subject the liner tointermittent compression loads. If the liner mate-rial is slow to recover, and most are, then vibra-tion periodically reduces the sealing force andmay produce intermittent gaps which open andclose at concentrated pressure points, in stepwith whatever frequency the bottle vibrates atduring transportation.

7. The shippers of these DG packages do appearto be following the industry rule regarding theapplication torque.

8. The industry rule is equivalent to requiring thatthe seal force be the same for all bottles, regard-less of cap diameter, and this has the conse-quence of compressing the liner less for largercaps, so larger caps have greater potential forleaks.

REFERENCES

1. Wybenga F. Air transport incident data and analysis of packaging failures. Dangerous GoodsPanel Meeting Proceedings, Singapore, 14–18 May2001.

2. McLaughlin J. FAA report: package failure analysisfor HazMat shipments for 1998–99. Presented at the Annual Consortium of Distribution PackagingBoard Meeting, Michigan State University, Fall 2000.

3. UPS. Study, RR:D10-1013, Altitude and Temperature –Study of the Feeder Aircraft Network. ASTM D6653-01.ASTM: West Conshohocken, PA, 2001.



4. ASTM. D6653-01, Standard Test Methods for Determining the Effects of High Altitude on Pac-kaging Systems by Vacuum Method. ASTM: West Conshohocken, PA, 2001.

5. Singh PS and Cheema A. Measurement and analysis of the overnight small package shippingenvironment for Federal Express and United Parcel Service. J. Testing Evaluation 1996 July: 205–211.

6. Newsham M, Pierce SR and Singh P. Parcel labels,distribution pose challenges for drop orientation.Packag. Technol. Eng. 1999; April: 30–33.

7. ASTM. Annual Book of ASTM Standards, vol 15.09.ASTM: West Conshohocken, PA, 2002.

8. Marcondes J, Singh P and Burgess G. Dynamicanalysis of a less than truck load shipment. Paper#88-WA-EEP-17. ASME: New York, NY, 1989.

9. Closure Guide. Closure Manufacturers’ Association:2000.

10. Pisuchpen S. Model for Predicting ApplicationTorque and Removal Torque of a ContinuousThread Closure. Master of Science Thesis, School ofPackaging, Michigan State University, 2000.



package performance testing of dangerous goods in high-altitude shipments

Documents