ASTM D2444 covers the process used to determine the resistance of thermoplastic pipe and fittings to impact by a tup (falling weight) under defined conditions.  The mass of the tup shall be 6, 12, 20 or 30 lbs (2.7, 5.4, 9.1, or 13.6 kg) and shall fall from a maximum height of at least 10 ft (3.0 m) and a minimum of 2 ft (0.6 m). There are three interchangeable inserts for the tup, Type A is a cone with a rounded point, Type B is a cylinder with a relatively flat surface, and Type C has a 0.5" diameter “pin” with a rounded end. Two specimen supports (either a V-block or a Flat Plate) are defined in the standard.  The combination of test variables which offers reasonably repeatable results with the test being easy to run with little or no hazard to personnel is the one that should be used.

The impact resistance of thermoplastic pipe and fittings relates to its suitability for service and to quality of the processing. It may also provide a relative measure of the tested material’s resistance to breakage during handling and installation, and in non-buried applications, to in-service breakage. Results gathered by this test can be used as the basis for establishing impact test requirements in product standards; to measure the effect of changes in materials or processing on the product and to measure any effects of the environment on the pipe or fittings.

When asked to offer a testing solution to this standard we recommend the use of our Instron 9400 Series. For those customers who are testing only to the lower impact energies (12 ft-lb to 60 ft-lb) set by the test conditions in the standard we recommend using drop tower model 9440.  If the product being tested needs the maximum test conditions (300 ft-lbs) we recommend the use of our drop tower model 9450 with the High Energy Option.  To prevent a secondary impact of the falling weight onto the pipe or fitting we employ our anti rebound device. Smaller pipes and fittings can be easily tested on either the 9440 or the 9450.  The large area below offers room for larger diameter pipes up to 12 inches.  For pipes over that we offer larger, extended support tables. To fully protect the operator from flying debris we include and offer a selection of interlocked safety enclosures.

Though the test defined in the standard calls for visual inspection after impact to determine if the specimen has failed, by including instrumentation with our Data Acquisition System, Bluehill Impact software and instrumented tup failure points/modes that may remain hidden under normal test conditions can be found. One piece of information that may not be found without the use of instrumentation is the first crack or incipient damage point.  Pipes or fittings may fail in interior areas and remain undetected when visually inspected.

Read More ...