The Inspection of Cold Welds in Electrofusion Joints

Electrofusion joints for polyethylene pipe are one of the common joining methods used in the water and gas industries for distribution pipelines. Common problems in manufacture of these joints are contamination, lack of fusion, lack of penetration and insufficient heat applied to the joint. The latter flaws can result in a joint that, although apparently fused, does not have the same mechanical properties as a properly prepared joint. This paper presents ultrasonic and thermal techniques for detecting and monitoring flaws in the weld. For post welding application a phased array ultrasonic technique is described that indicates flaws at the weld joint and the size of the heat affected zone as a record of the applied heat. Results of laboratory experiments on sample pipes are described, and prototype systems for application of the techniques to site work are also shown.