By James Wren, Application Engineer, Prosig
A strain gauge is an electrical sensor which is used to accurately measure strain in a test piece. Strain gauges are usually based on a metallic foil pattern. The gauge is attached to the test piece with a special adhesive. As the test piece is deformed, so the adhesive deforms equally and thus the strain gauge deforms at the same rate and amount as the test piece. It’s for this reason that the adhesive must be carefully chosen. If the adhesive cracks or becomes detached from the test piece any test results will be useless.
Strain gauges are used not just for metals; they have been connected to the retina of the human eye, insects, plastics, concrete and indeed any material where strain is under investigation. Modern composite materials like carbon fibre when under development are often constructed with strain gauges between the layers of the material.
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Prosig have been awarded the contract to upgrade the Online Vibration Monitoring System at Wylfa nuclear power station.
Wylfa is located on the north coast of Anglesey and has two Magnox design nuclear reactors and four turbine generators. The station supplies 23 million kilowatt hours of electricity, enough to meet the needs of two cities the size of Liverpool and Manchester put together.
A PROTOR system has been installed and running Wylfa since 1998. The system monitors the four main steam turbine generators and also eight gas circulators, four for each of the two reactors. The system provides important vibration trends for these critical items of plant for both local and remote analysis.
The new contract is to replace the existing PROTOR-3 Remote Monitoring Data Analysis Systems (RMDAS) with new PROTOR-4 P4700 units. A total of eight P4700 units will be supplied, one for each main turbine and one to monitor a pair of Gas Circulators. The flexibility of the P4700 in handling multiple machines with individual tachometer or phase reference signals is ideally suited to this requirement.
