Abstract: There is described an apparatus for monitoring particles in a fluid stream, comprising a body portion and a detector element that is acoustically decoupled from the body portion. The detector element comprises a target surface, a sample acoustic sensor and a corrosion sensor. The sample acoustic sensor is acoustically coupled to the target surface and is arranged to provide a first signal, which varies in dependence upon acoustic noise generated by impacts of particles and fluid on the target surface. The corrosion sensor is arranged to provide a second signal, which varies in dependence upon corrosion and/or erosion of the target surface. A corresponding method of monitoring particles in a fluid stream is also described. The method and apparatus are suitable for monitoring sand in oil and gas production flow streams.

Abstract: An apparatus (1) is disclosed for monitoring the effect on a material of exposure to a fluid, and thereby monitoring the effect on a section of pipe (9) for carrying the fluid. The apparatus includes a sensor element (51) exposed to the fluid and formed as a ring of the material coaxially mounted within, but electrically insulated from, the section of pipe (9). Changes in the electrical resistance of the sensor element (51) are monitored. Preferably, the apparatus also includes a reference element (31) electrically insulated from the pipe (9), electrically connected in series to the sensor element (51) and protected from exposure to the fluid. The elements may both be made from the same material as the pipe (9) and, as they are contained within it, experience the same temperature and pressure variations as the pipe (9).