Measurement of stress in a ferromagnetic material
US6854336B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | Dec 18, 2001 |
| Grant date | Feb 15, 2005 |
| Priority date | — |
| Expiry date | Dec 18, 2021 |
Classification
- Technology area (CPC F)Mechanical Engineering; Lighting; Heating
- CPC primaryF16L2101/30
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Stress in the wall of a pipe (12) is measured using a pig (10) carrying at least one linear array of probes, so that the probes (30) in the array pass in succession over a location on the pipe wall. Each probe (30) comprises an electromagnetic core (32) with two spaced apart electromagnetic poles (34), and a magnetic sensor (36) arranged to sense the reluctance of that part of the magnetic circuit between the poles (34), and an alternating magnetic field is generated in the electromagnet means and consequently in the pipe wall. Successive probes (30) in the array are oriented differently so that the corresponding orientations of the magnetic field in the pipe wall are different. Preferably the probes (30) also include sensors (38) between the two poles (34) to sense magnetic flux perpendicular to the direction of the free space magnetic field between the poles. The signal from the sensor (36) and (38) enable the stress to be determined. Such an array may be used with any long object of ferromagnetic material.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.