GB782752A - Improvements relating to inspection methods and apparatus - Google Patents

Abstract

782,752. Flaw detection by nuclear radiation. ROLLS-ROYCE, Ltd., and UNITED KING- DOM ATOMIC ENERGY AUTHORITY. Dec. 19, 1955[Dec. 17, 1954] No. 36658/54. Class 40(3). In order to test a flexible hose, made, for example, of rubber, for cracks or flaws the hose is filled with liquid containing a radio-active isotope in solution and under pressure, it is then emptied, rinsed and moved past a radiation sensing device to detect any parts having abnormal radio-activity. A suitable isotope combination is cerium 144-praseodymium 144 and the test solution may be made up in the proportions of 7 millicuries of this in 200 c.c.s. of redistilled water containing a minimum of 20 micrograms per c.c. of inactive cerium and praseodymium as carriers. Apparatus for effecting the test may comprise a drum 11 on which the hose 10 can be mounted with its ends connected by tubes 12 and 13 to mechanically coupled rotary valves 14 and 15. These valves are coupled to a reservoir 28 for the test liquid, a pump 36, a source of water 30, and a drain pipe 38. They have four positions : in the first the pump forces test liquid through the hose, in the second the pump continues to force in liquid but the far end of the hose is closed by a pressure gauge so that the required pressure is reached inside the hose; in the third valve position both ends of the hose are opened to drain the test liquid back into the reservoir 28, and in the fourth water from source 30 is allowed to flow through the hose to the drain to rinse it. The hose now has a small residual radioactivity and greater activity at any points where cracks or flaws retain some of the test liquid. To locate such flaws the hose is wound slowly from drum 11 past a test position to a further drum. At the test position the hose 10 passes through an array of geiger-muller tubes 42 the output of which is fed through a cathode-follower circuit CF to a rate-measuring circuit RM. The circuit R.M. feeds a potentiometer recording apparatus P continuously recording the level of radiation emission on a paper chart and also a solenoid operating a marking pen. The pen may either be arranged to mark continuously except when the emission exceeds a certain value or to mark only when such emission occurs. In either case the defective portions, if any, of the hose can readily be located.