METHOD FOR DETECTING POOR ADHESION OF FACTORY- COVERED POLYETHYLENE ANTICORROSIVE COATING TO METAL TUBES Russian patent published in 2002 - IPC

FIELD: nondestructive inspections; diagnosing polyethylene covered metal tubes. SUBSTANCE: method involves introduction of ultrasonic pulses into coating by means of piezoelectric transducer of ultrasonic flaw detector, reception of many times reflected ultrasonic pulses and their conversion into echo signals. Mechanism of amplitude variations is determined for bottom echo signals as function of nonmetal layer thickness with specified parameters of nonmetal layer adhesion to metal using coupons with coatings of different thickness. Piezoelectric transducer is installed on coating surface of tube under inspection and its position is varied until maximal amplitude of first bottom echo signal is attained. With ultrasonic flaw detector amplitude being varied, amplitude of first bottom echo signal displayed on CRT screen is set to desired level. Sweep range is corrected so that all bottom echo signals of many times reflected ultrasonic pulses in metal occur within ultrasonic flaw detector screen. Amplitude distribution of bottom echo signals on ultrasonic flaw detector screen is analyzed to estimate reliability of metal-adhesive-polyethylene joint including coating thickness and mechanism of variation of first bottom echo signal amplitude as function of nonmetal layer thickness. EFFECT: enhanced reliability of flaw detection method. 1 dwg