Instrumented tubular device for transporting fluid under pressure, using Bragg network optical gauges to monitor temperature, pressure and pressure fluctuations and thus cumulative fatigue

摘要

At least three assemblies (B1, B2, B3), each of at least two Bragg network optical gauges assembled to form a rosette, are fixed in at least three measuring places (22) over the length of the tube, connected together (24) and to an optical cable (23) by optical fibres. The optical cable is connected to an opto-electronic measurement system. At least one assembly includes a temperature gauge : The device is a tube (20) in which the fluid circulates, with which means of measuring the principal deformations of the tube and the temperature of the fluid in the tube are associated. Each rosette of gauges forms a flexible detector in two dimensions. Each assembly has three gauges measuring tube deformation. Each detector includes a part measuring deflections and a part measuring temperature. The part measuring deflections is a monomode optical fibre on which Bragg networks are photo-etched, coiled and held stuck between two leaves. The fibre inlets and outlets are protected by capillaries. The parts of the fibre forming the Bragg networks are uncovered. The part measuring temperature is a Bragg network stuck on a metal plate of the same nature as the metal of the tube. Alternatively, the device has at least three measuring boxes (B1, B2, B3) in which are placed respectively three detectors, isolated from external hydrostatic pressure and connected by tubular connections (24). The central box (B2) is connected to the measuring instrumentation by an optical output cable (23). The boxes and connections are welded together to form a rigid assembly. The output cable is made of a stainless steel tube filled with gel containing several monomode optical fibres and a steel wire armouring separated by plastic sleeves. The central box includes a base designed to form the connection to the optical output cable. The device includes an assembly of at least three detectors covered with a protective coating of polymer 3 to 4cm thick. A bypass box forms the link between the detectors of each assembly and a main optical cable connected to the measuring instrumentation. The load on the main cable is made by coiling the cable around the tube. The output cable is included in the protective coating. The fluid transported is gas or hydrocarbons.