Development and validation of an automated ultrasonic system for the non-destructive evaluation of welded joints in thermoplastic storage tanks

摘要

There are over 60,000 medium-to-large industrial storage tanks made of thermoplastic materials in Europe. Thermoplastic tanks are an attractive alternative to metal tanks for storing many products, including hazardous chemicals due to their outstanding chemical resistance, longer design life and cheaper installation costs. Unlike metallic storage tanks, there are no established procedures for inspecting safety critical welds in thermoplastic storage tanks, either at the manufacturing stage or during service and consequently they are often used without due consideration of their condition and fitness for service. Where inspection is required for the continued use of the tank this involves the costly draining and venting of the tank prior to personnel entry. The development of a reliable and repeatable volumetric NDT technique for examining the containment welds in thermoplastic tanks will open up new and more demanding applications for these products as well as avoiding the need for draining the tank to inspect existing stock. This paper will describe the progress on the development of an ultrasonic inspection system for plastic storage tanks. Results will show the progress on the inspection of butt welds and fillet welds in plastic storage tanks.