What is a Drop Impact Test?

Impact Resistance testing is a way of rating the resistance of a pipe or fitting to cracking or breakage when struck by an impact force. It is an arbitrary test under laboratory conditions.

Each standard will specify the requirements for the test, including the type and weight of the striker (the Tup), the impact force (usually rated in foot pounds force), and the specimen support (either a v-block of a flat plate). There are three types of striker (called a Tup) used for the test: 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. The Tup is attached to a long rod so weights can be added to bring the total weight up to the amount specified by the product standard. The Weighted Tup is attached to a cable and placed in a long vertical guide tube.

The specimen is placed under the guide tube in the required holder, and the Tup is raised to the specified height above the top surface of the part. The Tup is allowed to fall free and strike the specimen, and is caught by the cable before it can bounce and strike the specimen again. The specimen is then inspected for any signs of cracking or failure. When testing ductile materials like polyethylene, the signs of failure are often very subtle, but in the case of brittle materials like PVC of PC, a failure is usually quite dramatic, and a safety cage is required to contain the flying shrapnel.