Detecting failures in flexible multistrand steel structures
US7876096B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Dec 14, 2005 |
| Grant date | Jan 25, 2011 |
| Priority date | — |
| Expiry date | Aug 23, 2027 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N27/9046
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A flexible elongate structure, such as a flexible riser (10) for connecting oil and gas wells to floating production platforms, comprising at least one layer (20) of steel wires near the surface which extend at least partly along the length of the structure, can be monitored by inducing a magnetic field in the steel wires using an electromagnetic coil, and monitoring the magnetic flux density near the surface of the structure so as to detect if any wires have broken. Measurements are made at two different frequencies, the lower frequency giving an output dependent both on stresses and on the number of adjacent wires in the layer (20), and the higher frequency giving an output primarily dependent on the number of these wires. By comparing these two measurements a corrected output parameter (P) may be obtained that is indicative only of stress. A break in a wire can be expected to change the stress in that and adjacent wires.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.