GB1395852A - Apparatus for inspecting tubular goods - Google Patents

Abstract

1395852 Inspecting pipes using radiation detectors PLASTIC APPLICATORS Inc 7 Aug 1973 [7 Aug 1972] 37357/73 Heading G1A To inspect a pipe for flaws its wall thickness is measured by a radiation detector in the pipe bore which co-operates with a multiple radiation source which is moved along a circular path round the outside of the pipe. The radiation source has three radio-active emitters which emit separate beams of radiation towards the pipe, a movable mask being provided to control the intensity and width of the total radiation emitted. The basic apparatus is shown in Fig. 1, added on to a known magnetic flaw testing machine. The known machine drives a pipe 16 to be tested through magnetic coils 18 and 20 to test for circumferential flaws and on to a current carrying probe 21 to test for longitudinal flaws. The present invention provides apparatus shown generally at 10 which comprises a detector assembly 25 fitted on to the end of the magnetic flaw probe 28 and a source assembly 27 which rotates around the pipe as the latter moves along the probe, so as to examine a helical path along the pipe. The detector assembly has fins 30, 31 Fig. 2 which help to maintain it centrally within the pipe; this fig also shows a motor 39 which causes the source assembly to rotate on bearings 37, 38. This assembly has three chambers 43, 44, 45 shown in Fig. 5, each housing a gamma emitter such as Cobalt 60 or Cesium 137; passages leading from these chambers direct radiation on to an area around the axis 17 of pipe 16. The passages are dimensioned so that by choice of the power of the individual sources a uniform radiation density is achieved in the area irradiated, and hence deviation of the detector from axis 17 can be tolerated. An apertured plate 58 is provided which is movable from left to right in Fig. 5 to block the two outer passages and provide an unobstructed passage for the central emitter if it is desired to reduce the field irradiated, e.g when small pipes are tested. In this latter case the scintillation counter used as a detector has a hollow bore, Fig. 7 (not shown), to increase the tolerance on its position. The apertured plate can be manually moved from one position to the other after the two spring loaded bolts at its ends have been released. A further apertured plate is provided below the first one, as described with regard to Fig. 3 (not shown), which allows all the passages to be blocked automatically by the operation of solenoids when the pipe is not present. This prevents the excessive radiation which would otherwise strike the detector in the absence of the pipe. Known circuitry which records the detector signals, effects calibration, and if necessary activates an alarm is described.