Abstract: A method for determining the position of a leak in a conduit or pipeline, especially one of small diameter, in which a carrier body, for example a short length of co-axial cable, carrying a short-lived radioisotope is inserted into the conduit or pipeline and is caused to move along it by pressuring up the conduit or pipeline from one or both ends thereof with fluid, for example water. The carrier body travels to the leak but no further and its location is detected from outside the conduit or pipeline using a radiation detector.

Abstract: Method and apparatus to determine the position of a liquid/liquid or liquid/vapor interface in a remote inaccessible location, for example in undersea oil storage tanks, by exposing the liquids or liquid and vapor to gamma-radiation from a source adjacent to or within the vessel containing the liquid(s) and monitoring the gamma-radiation issuing from the liquids or liquid and vapor, and using long lengths of optical fibre to convey the signals received to a measuring instrument. The invention employs optical fibres which may be up to several hundred meters long and among its advantages is the need for no moving parts, electrical supply or electronics at the remote location.

Abstract: A method and apparatus for determining the position of a valve for example ball valves, plug valves, gate valves using a source of radiation such as cesium-137 located either on or adjacent to the external surface of the valve or within the valve itself, for example in the ball of a ball valve, and a radiation detector such as a Geiger-Muller tube on the external surface of the valve. Source and detector are aligned and located relative to one another so that the count rate detected is indicative of the valve position. The method is accurate and, for example, allows the position of the ball in a ball valve to be monitored to within .+-.1 mm.