Automatic non-destructive testing

Automatic non-destructive testing

measurement of metal thickness by ultrasonic methods has provided one way in which accurate and up-to-date data can be gathered. The problems in apply...

117KB Sizes 2 Downloads 25 Views

measurement of metal thickness by ultrasonic methods has provided one way in which accurate and up-to-date data can be gathered. The problems in applying ultrasonics to hot work are discussed, the methods currently in use are outlined and the limitations explained. 1. 2.

Banks, B., Oldfield, G. E. and Rawding, H., 'Ultrasonic flaw detection in metals' Iliffe, London (1962). McMaster, R. C. (Ed.)'Non-destructive testing handbook,' Ronald, New York (1959).

LEV E LAN D FLO W MEA SUR E MEN T P. Franchi

M. Franchi is head of the Ultrasonics Division of L' Electronique Appliquee

Level measurement is performed by reflection of ultrasonic pulses from the surface. It is indispensable for the propagation medium to be homogeneous. Automatic calibration using a fixed echo makes it possible to measure to the sound velocity. The measurement can be carried out in gas or liquid, in the latter through the walls of the container. Both methods have numerous applications. Flow measurement is performed by several methods: apparent variation of velocity; deflection of a beam picked up by a differential cell; and the Doppler effect. A differential unit can eliminate the effects of changes in velocity so that accuracy is finally limited only by the nature of the flow. The transducers are usually piezoelectric, sometimes magnetostrictive. 1. 2.

Goldman, R. G. 'Ultrasonic technology' Reinhold, New York. George, P. et al 'Debitmetre sanguin a effet Doppler' Paper at Electronique Medicale, 1966.

N. D. T. AND ENGINEERING INSURANCE INSPECTION B.Lambert

Mr. Lambert is Supervising Engineer of the Non-destructive Testing Section, Research Department, British Engine Boiler & Electrical Insurance Co. Ltd. He is primarily concerned with the prevention of service failures by the early detection of defects

Of all the various n.d.t. techniques, ultrasonics was found to have the widest application. Tests have been successfully applied to forged, welded and riveted pressure vessels; axles, crankshafts and other rotating parts; forgings, castings and rolled materials; welds in pipelines, lifting machinery and gasholders. The company is at present co-operating with several clients in order to establish 'corrosion-logs' by using thickness gauging techniques to check the thickness of vessels and pipelines in service. Various types of failure will be illustrated, together with the method of detection.

1. 2.

3. 4.

Krautkramer, J. U. H. 'Werkstoffprufung mit Ultraschall', Springer (1961) In German. Banks, B., Oldfield, G. E. and Rawding, H. 'Ultrasonic flaw detection in metals' Iliffe, London (1962). Holt, D., British Journal of Non-destructive Testing, 6, No.2, (June 1964). Lambert, B., British Engine, Boiler and Electrical Insurance Co Technical Report, Vol. 5 and 6.

AUTOMATIC NON-DESTRUCTIVE TESTING D.H.Davies

Mr. Davies is Superintendent of Non-Destructive Testing at Stewarts and Lloyds Ltd

EQuipment will be described which examines steel tubes and indicates, by means of a graphic presentation, the area and extent of any imperfections which may be present in the tube. The tubes to be examined are passed through a rotating inspection head which carries ultrasonic transducers. The transducers on the rotating head describe helical inspection paths on the tube; the transducers are spaced at 90 0 intervals about the circumference. The equipment is arranged to measure tube wall thickness and to indicate any areas of lamination which may exist. Also, arrangements are made to indicate crack-like imperfections. To futiil these requirements and to allow the equipment to operate at reasonable throughput speeds, eight transducers are used, four arranged at normal incidence to the tube surface and producing longitudinal waves, and four arranged to produce shear waves. The transducers are mounted in pairs. The information collected by the transducers rotating about the tube is processed by electronic equipment and presented as permanent recordings. The recordings indicate the position of imperfections relative to the longitudinal and circumferential dimensions of the tube. A continuous and permanent record of wall thickness is produced. British Patent No.1 ,040,242.

FURTHER ADVANCE S IN U LT RASONIC DIAGNOSIS Ian Donald

Professor Donald is Regius Professor Of Midwifery in the University of Glasgow

This diagnostic work has now extended to routine daily use and at the Queen Mother's Hospital, Glasgow, about 80 cases a month are being investigated, not counting foetal head measurements. A very early diagnosis of pregnancy is possible, easily within the first fortnight after a missed menstrual period, and the location of the level of implantation within the uterus can be readily demonstrated. In cases who have already aborted the need for curettage can be determined by demonstrating whether or not the uterus still retains unpassed products of conception. Likewise cases of secondary postpartum haemorrhage can be investigated for retained tissue requiring evacuation. The diagnosis of twin pregnancy still rests primarily on the demonstration of two foetal heads but with care a double gestation sac may be demonstrable at an even earlier stage. Our studies in foetal head mensuration in utero indicate that the bipariental diameter is more related to maturity than to foetal weight and is increaSingly used therefore in the estiULTRASONICS October 1966

222