Plastics Pipe Institute Publishes Case Study for Plastic Pipe NDT
Historically, inspection of plastic pipes, fittings and joints comprised visual inspection and conformance testing to the applicable standard. These methods are well proven as proactive measures that help ensure a quality plastic pipe system.
As with most industries, technology continues to evolve, driving continuous improvements in the knowledge base, methods and measurement techniques. This is now reflected in the growing use of non-destructive test methods and evaluation within the plastic pipe industry.
Over the last 30 years, only a few companies in North America have used non- destructive testing (NDT) for inspection and non-destructive evaluation (NDE) for the volumetric examination of plastic pipes. It is only within the last 2 – 5 years, organizations such as ASTM E07 or F17 and ISO TC138 have worked to introduce standardized inspection methods for polyethylene (PE) heat-fusion and electro-fusion (EF) joints.
Although visual assessment is an NDE technique, as discussed in Section 2.0, this document is primarily intended to address considerations for the existing and emerging instrumented methods as they relate to heat fusion (butt and saddle), electro-fusion (socket and saddle) and socket fusion of plastic pipe. Currently, these current state-of- the-art methods include:
• microwave testing
• ultrasonic testing (UT)
o phased array ultrasonic testing (PAUT) o time-of flight diffraction (TOFD)
o time-of flight diffraction (TOFD)
The plastic piping industries’ current NDE practice includes visual, bead inspection and short-term hydrostatic pressure test methods to evaluate the quality of fusions. For heat fusion, electrofusion and socket fusion, practitioners are generally limited to a visual inspection of the final joint with particular attention made to the size, shape and location of the resulting melt bead, where visible. The bead is not visible in all electrofusion fittings.
Two NDE methods widely used in the plastics pipe industry are listed below. Their use is regional in that, North America employs visual inspection and the United Kingdom utilizes the bead assessment method. These are a couple of the many confirmatory checks performed on the pipe, fittings and joints.
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