Untethered, unpowered, rollable device to sense condition of pipeline wall
A sensor unit for use in sensing conditions in a pipeline comprises an untethered a ball-shaped surround adapted to roll along the interior surface of a pipeline, and instrument package within the ball-shaped surround. The package contains at least one magnetometer or accelerometer. Preferably, three magnetometers, arranged orthogonally, are present. Other sensors can also be present as required, such as an acoustic sensor to detect leaks and a temperature or chemical sensor. Recording means record the data acquired by the magnetometer(s) or accelerometer and the sensors, and optionally also record a timing trace.
1. A tether-free sensor unit of spherical or ellipsoidal shape with no motorized propelling means, for inspecting a pipeline which contains a moving liquid, which sensor unit comprises a sensor package containing a sensor to sense the number of revolutions of the sensor unit when such unit rolls along the bottom of the interior of the pipeline selected from at least one magnetic sensor and at least one accelerometer, and recording means for recording data sensed by said sensor, said sensor unit being of greater density than the density of the liquid in the pipeline to be inspected, whereby it can roll along the bottom of the pipeline to be inspected.
2. A sensor unit as claimed in claim 1 , in which said sensor is three magnetometers, arranged orthogonally to one another.
3. A sensor unit as claimed in claim 2 , additionally comprising an acoustic sensor.
4. A sensor unit as claimed in claim 3 , additionally comprising a ball shaped outer surround which surrounds and protects the sensor package.
5. A sensor unit as claimed in claim 1 , additionally comprising a temperature sensor to sense the temperature of liquid surrounding the sensor unit.
6. A sensor unit as claimed in claim 1 , additionally comprising an acoustic transmitter or transponder.
7. A sensor unit as claimed in claim 6 , in which the transmitter or transponder transmits a range of frequencies.
8. A sensor unit according to claim 6 , in which the transmitter or transponder emits at least one frequency above 20 KHz.
9. A sensor unit according to claim 6 , in which the acoustic transmitter or transponder transmits a range of frequencies comprising a swept pulse, in a range between 1 KHz and 200 KHz,
10. A sensor unit as claimed in claim 6 , additionally comprising a battery to power said recording means and the transmitter or transponder.
11. A sensor unit as claimed in claim 1 , in which the sensor unit is spherical and has a diameter of less than half and greater than 1/10 of the diameter of the pipeline to be inspected.
12. A sensor as claimed in claim 1 , in which the sensor unit is ellipsoidal and the length of its major axis is less than ½ of the diameter of the pipeline to be inspected.
13. A method of inspecting a pipeline which contains flowing liquid, comprising;
(a) providing a sensor unit which comprises a package containing a sensor selected from at least one magnetic sensor and at least one accelerometer, and means for recording data sensed by said sensor, said sensor unit being of greater density of the liquid in the pipeline to be inspected, and
(b) allowing the sensor unit to be rolled along the bottom of the interior of the pipeline by the flow of the liquid, while recording a signal representative of the number of revolutions that the surface of the sensor unit has made.
14. A method as claimed in claim 13 , in which the sensor unit comprises an acoustic transmitter or transponder, and the method includes emitting signals from the transmitter or transponder and receiving such signals at least one location along the pipeline.
15. A method as claimed in claim 14 , in which signals are emitted at a frequency above 20 KHz.
16. A method as claimed in claim 13 , in which signals are emitted at a range of frequencies comprising a swept pulse, in a range between 1 KHz and 200 KHz.
17. A method as claimed in claim 13 , in which said sensor is three magnetometers, arranged orthogonally to one another.