EMAT thickness measurement for tubes in coal-fired boilers

Boilers, the most troublesome components of electric-power generation plants, cost the US utility industry over $5 billion per year in unscheduled shutdowns, repairs and power replacements. The non-destructive testing technique is an important tool for predicting the life of boiler tubes. A standard ultrasonic technique is used for measuring their wall thicknesses and determining the degree of corrosion. Such a test requires clean, rust-free surface and all tubes must be sandblasted prior to the inspection. This adds precious hours to the boilerʹs outage-time. This paper presents the application of the electromagnetic-acoustic transducer (EMAT) process that accurately measures the tubeʹs wall thickness through thick layers of crusty scale—the kind most often found in aging fossil-fired boilers. Laboratory and field trials were carried out during the last outage season. Back-to-back tests showed that good agreement between the results of the EMAT technique and the classic ultrasonic thickness gauge measurement process.