Customer
Our client, a market leader, is a producer and supplier of electricity in France and Europe for companies, local authorities and individuals.
Tested product
Cylindrical test pieces simulating water valves used by the customer.
These may include water fittings such as steam valves, globe valves, gate valves, double-sealed isolation valves, etc.
Objective
R&D approach: Investigate the tightness of the customer's valves in nuclear power plant circuits by measuring liquid leakage.
Problematic issues
The test bench must come as close as possible to the operating conditions of nuclear power plant circuits, by reproducing the same effects (metal-to-metal contact) on the cylindrical specimens.
The bench is installed in the R&D laboratory.
Solution and result
The transmissivity measurement bench developed by LF Technologies makes it possible to quantify the leakage of water, in liquid phase, between 2 surfaces in mechanical support (test piece in support on a reference counterpart), subjected to a differential pressure, according to
- the shape defect of the specimen
- the pressures (internal and external)
- the force with which the specimen rests on the antagonist.
The test specimen is placed in the centre of the test chamber, where a thrust rod stresses its test face against an antagonist. A bell closes the chamber and protects the area.
The antagonist, made of a rigid material with a flat reference surface, is applied to the specimen face with the shape defect. The tube is sized to provide a measure of the applied force. An inductive displacement transducer of high sensitivity is placed in the tube to measure its axial deformation. The axial loading is carried out by means of a short-stroke hydraulic cylinder (10 mm), with a pressure of up to 300 bar and a thrust of 150 kN.
The shape of the bell is designed to limit air retention zones. The pressure is measured in each "chamber". A temperature sensor measures the temperature as close as possible to the leak.
Three independent plungers allow a continuous flow and perform different functions, including external pressurisation, compressibility measurement, external leakage measurement and flow measurement (in and out).
The system is able to provide a perfect controlled pressure with very precised measurement of flow, which depends on the tested part. This system is able to measure very low flows, corresponding to very small leaks.
A control PC, using software developed under LabVIEW, provides the control and measurement functions.
