AS/NZS 4766 Impact Test of Molded Polyethylene Tanks

If being installed in certain locations molded polyethylene tanks used to store liquids must pass AS/NZS 4766 to ensure that they have been properly designed and manufactured. Appendix D of this standard defines a Low Temperature Impact Test that specimens cut from areas on the tank must pass to be certified to the standard. The Appendix calls for the testing of a 125mm specimen, that has been cooled to -40° C for 24 hours - with an uninstrumented 25 mm diameter hemispherical striker from a drop height that will reach a specified minimum impact energy as defined by the wall thickness of the specimen. To fully meet the standard the impact must take place within 10 seconds of removal from the conditioned environment.

We were recently asked to demonstrate how adding instrumentation to the defined test would benefit the process. As outlined in the standard impact energies ranging from 122 J to 271 J (89.98 ft-lb – 199.89 ft-lb) are to be used to test the specimens – the minimum energy to be used is based upon the wall thickness of the specimen. This energy range makes the CEAST 9350 with the optional High Energy package and standard weight crosshead the ideal system to use. Adding a custom Clamping Set (standard calls for a 90mm unsupported test diameter vs. the standard 76mm of the standard fixture) and the optional Environmental Chamber will allow the entire test to take place in a temperature controlled environment thereby eliminating any worries about meeting the 10 second rule.

Inclusion of a 22 kN Instrumented Tup will allow the end user to collect load-time-velocity data from the DAS (Data Acquisition System) and Visual Impact ;Software. By fully instrumenting the test the manufacturer is able to gather not only maximum values but more importantly they can establish the lower loads and impact energies where incipient damage begins.