It is advantageous for the upkeep of a pipeline to be able to take measurements of the fluid or gas conditions in the pipeline. In some cases, it is desirable to measure the condition of the fluid or gas at one particular location of the pipeline over a protracted duration. For example, in an oil-filled pipeline any free water that is present is likely to concentrate where there are dips in the pipeline profile, and is likely to be reduced near peaks in the profile. It may be of interest to the pipeline operator to monitor the rate of accumulation of water in the bottom of one or more of such dips in the pipeline profile. Such measurements can give an indication of the likelihood of corrosion of the pipeline at that location.

Presently, measurements of fluid conditions in a pipeline are made using a vehicle, typically referred to as a pipeline pig, which travels through the pipeline taking measurements as it progresses. Due to the continual motion of the pig it is impossible to measure any change in conditions at a single. location in the pipeline over a defined period of time. Furthermore, if a sensor on the pig for measuring fluid conditions has a slow response time, an area of pipeline that is of interest, e. g. a dip in the pipeline, may be too short to accurately measure the fluid conditions.

An International Application WO 00/79242 to Gartland describes a system which deposits carriers at intervals within a metal pipeline. The carriers include a magnet to attach the carrier to the pipeline wall and a weight loss coupon which absorbs moisture while the carrier is in place. Some time later the carrier is retrieved and the weight and/or thickness of the weight loss coupon measured to give an indication of corrosion at the position where the carrier was deposited. Although this system provides a measuring system at a location in a pipeline, the measurement cannot be determined over time as the coupons provide no data until they have been recovered and analysed. Additionally, the analysed result will only give an average rate of metal loss over the time spent in the pipeline, thus a continuous measurement is not possible. Furthermore, as the measurement is not'available in real time no indication can be obtained as to whether the amount of corrosion in the pipeline has reached a critical level.

It is an object of at least one embodiment of the present invention to provide a system which overcomes the drawbacks of the prior art travelling system.

It is a further object of at least one embodiment of the present invention to provide a system which enables fluid conditions at one position in a pipeline to be measured over time.

It is a yet further object of at least one embodiment of the present invention to provide a system which monitors conditions within a pipeline with the minimum disruption to fluid flow within the pipeline.

According to a first aspect of the present invention there is provided a system for acquiring data. representative of one or more characteristics of the contents of a pipeline at one or more predetermined locations in the pipeline, the system comprising a sensor depositor and one or more sensor units, wherein the depositor includes means for depositing a sensor unit at each location and the one or more sensor units include sensing means for acquiring signals representative of the one or more characteristics of the contents and data acquisition means for acquiring data from the signals at intervals over a time period.

The intelligent sensor depositor may be a pipeline pig though other arrangements are envisaged. For example, the depositor may be a deployment vehicle that travels in the opposite direction to the flow, that is the reverse direction from a conventional pig. Thus the depositor is transportable through the pipeline.

Preferably the depositor includes a compartment for storing the one or more sensor units in order of deployment. More preferably the compartment is at the rear of the depositor.

Preferably the means for depositing the one or more sensor units is an ejection device. Preferably the ejection device is a spring. Alternatively the ejection device may be a compressed gas cylinder.

Preferably the depositor includes a location determination sensor. More preferably the location determination sensor is an odometer measuring distance travelled by the depositor. Further the depositor may include an electronic counter which counts pulses derived from the odometer to determine a pre-set count.

Advantageously the depositor further includes a solenoid valve. The solenoid valve may open at the pre-set count and trigger the ejection device. In. this way sensor units are deposited from the depositor at predetermined positions along the pipeline.

Alternatively the location determination sensor may be a sensor capable of detecting appropriate local conditions in the pipeline.

Preferably the depositor includes a sensor unit retrieval means. Preferably the retrieval means are one or more permanent magnets mounted on the front of the depositor.

Alternatively the retrieval means may be a latching mechanism mounted on the front of the depositor which can

latch onto a complementary mechanism on the one or more sensor units.

Alternatively the system may further include a sensor unit retriever, the sensor unit retriever comprising a body transportable through a pipeline and sensor unit retrieval means. Preferably the retrieval means are one or more permanent magnets mounted on the front of the retriever. Alternatively the retrieval means may be a latching mechanism mounted on the front of the retriever which can latch onto a complementary mechanism on the one or more sensor units.

Preferably the one or more sensor units include orientation means. Thus when deposited the sensor units will adopt a preferred orientation with respect to the pipeline. Preferably the orientation means is one or more magnets attached to a face of the sensor unit which connect the face to a wall of the pipeline.

Alternatively, the orientation means may be one or more weights arranged on the sensor unit to provide a centre of mass toward a face of the sensor such that the sensor unit will tend to roll until the face is against a bottom most surface of the pipeline wall.

Preferably the sensing means comprises one or more sensors. The one or more sensors may be temperature sensors, pressure sensors, moisture sensors, corrosivity sensors, a combination thereof or the like.

Preferably the data acquisition means includes a data storage facility wherein the data are stored at each time interval. The stored data may then be downloaded when the

sensor unit is retrieved. Alternatively, the data acquisition means includes a data transmitter, wherein the data transmitter transmits the data to a receiver positioned outside the pipeline. The data may be transmitted by electro-magnetic, acoustic, nuclear or other means.

Preferably, the one or more sensor units further comprise protective means covering surfaces of the one or more sensor units. Preferably the protective means may be a membrane or coating which decays at a predictable rate.

Alternatively, the protective means may be a membrane or coating which dissolves on contact with the contents of the pipeline. The protective means therefore provides protection to the sensor units prior to deployment.

Preferably also, the one or more sensor units include a release mechanism to allow the sensor unit to be released from the pipeline wall after a pre-determined time. The release mechanism may be a switch to deactivate electro- magnets. Alternatively the release mechanism may be a weight-shifting apparatus. The weight-shifting apparatus may move weights internally or release external weights to lighten the sensor unit or shift its centre of mass.

Optionally the release mechanism may be a buoyancy chamber into which gas is released to reduce the submerged weight of the sensor unit.

According to a second aspect of the present invention there is provided a method for monitoring conditions in a pipeline, the method comprising the steps; (a) passing a sensor depositor through the pipeline ;

(b) deploying a sensor unit from the sensor depositor at a location in the pipeline ; (c) sensing a characteristic of the contents of the pipeline to provide a signal representative of the characteristic ; and (d) acquiring data from the signal at intervals over a time period.

Preferably the sensor unit, when deposited, orientates itself against a wall of the pipeline.

Preferably the method includes a further step of transmitting the data to a receiver outside the pipeline.

Alternatively the method includes the further step of storing the acquired data in the sensor unit.

The method may further include the step of retrieving the sensor unit from the pipeline. This step may be achieved by passing a sensor retriever through the pipeline. The sensor retriever may latch on to the sensor unit.

Alternatively the sensor unit may attach itself to the sensor retriever via magnets on the sensor retriever.

In the event that the sensor unit is not retrieved, after a given time period, the sensor unit may release itself from the pipeline wall.

In order to provide a better understanding of the invention, an embodiment of the invention will now be described by way of example only, with reference to the accompanying Figures, in which:

Figure 1 shows a schematic cross-sectional view of a system in accordance with the present invention; and Figure 2 shows an illustration of a section of pipeline containing an intelligent sensor depositor, a previously deployed sensor unit and a sensor retriever according to the present invention.

Referring initially to Figure 1 there is illustrated a system for acquiring data representative of characteristics of contents of a pipeline at predetermined locations in the pipeline. The system is generally indicated by reference numeral 10. System 10 comprises a conventional pigging vehicle 12 which includes a chamber 14 mounted at the rear 16 of the vehicle 12. Mounted on a surface 18 of the vehicle 12 is a sensor 20. Sensor 20 is an odometer for determining a distance travelled by the vehicle 12.

Within the chamber 14 there is located an ejection device 22 for ejecting or deploying sensor units 24 located within the chamber 14 from the rear 16 of the vehicle 12.

Ejection device 22 operates by forcing the sensor unit 24 out of the chamber 14. There is only one sensor 24 illustrated within the chamber 14 in Figure 1, however, it will be understood that any number of sensor units 24 may be located in the chamber 14 and that pressure applied to the sensor unit 24 closest to the ejection device 22 will sequentially push all the sensor units along the chamber 14 until a rearmost sensor unit 24 is ejected from the vehicle 12. The process may be repeated until all the sensor units are ejected from the vehicle 12. The ejection device 22 comprises a spring held under

tension and released at predetermined times or alternatively, from a release signal derived from the sensor 20. In the preferred embodiment, a solenoid valve is incorporated within the ejection device 22 and an electronic counter counts pulses derived from the sensor 20 to reach a preset count. At the preset count the solenoid valve opens and triggers the ejection device 22 so releasing the spring causing the sensor unit 24 to be ejected or deployed from the vehicle 12. In the preferred embodiment, the action of the spring is augmented hydraulically by use of the differential pressure which will exist between the rear 16 and front 26 faces of the vehicle 12 within the pipeline.

It will be appreciated that alternative ejection devices 22 may be used such as a compressed gas cylinder which 'forces gas against the sensor unit 24 when opened.

Reference is now made to the sensor unit 24 which is deployed from the vehicle 12. Sensor unit 24 ideally comprises a spherical steel sensor body 28 which is slightly truncated so as to produce a flat face 30.

Each sensor unit 24 has a protective coating 31 applied to it. The coating 31 dissolves on contact with the contents of the pipeline. In an alternative embodiment the coating 31 decays.

The sensor body 28 is so constructed internally that its centre of mass is displaced from the geometric centre towards the flat face 30. In this respect the sensor unit 24 will tend to roll when deployed until the face 30 is downward and thus it can then sit relatively stably in

the bottom of the pipeline on the said flat face 30. At the surface 32 of the sensor unit 24 are sensors 34 and 36. Sensor 34 is mounted in such a way that fluid flow towards the sensor unit 24 once deployed will impact the sensor, whereas fluid or gas passing sensor 36 will not impact the face of the sensor 36. Sensors 34,36 may be of any type such as pressure, temperature, moisture or corrosivity.

In the embodiment of Figure 1, the sensor unit 24 illustrates an alternative positioning and orientation means for the sensor unit 24 once deployed. This is by magnets 38 attached to the surface of the sensor unit 24.

As with the displaced centre of mass, the surface comprising the magnet 38 will adhere to the wall of the pipeline once the sensor unit 24 is deployed.

Sensor unit 24 further comprises a signal processor unit 40. Signal processor unit 40 acquires the signals from the sensors 34 and 36 and processes them to form data representative of some characteristics of the contents of the pipeline being sensed that are of interest. Signal processing unit 40 includes a data acquisition unit to acquire the signals and further includes a storage unit in the form of a microchip which stores the data so that they may be downloaded some time later. In the preferred embodiment the signal processor unit 40 also includes a transmitter. The transmitter transmits the data to a receiver (not shown) outside the pipeline, so that an operator can obtain the data in real time.

Reference is now made to Figure 2 of the drawings which illustrates a method of acquiring data representative of

characteristics of the contents of a pipeline at a predetermined location according to the present invention. Initially chamber 14 is loaded with one or more sensor units 24 and the vehicle 12 released into the pipeline 42 whereupon it travels through the pipeline under the force of the contents of the pipeline 42. As the vehicle 12 travels through the pipeline 42 the odometer 20 tracks the distance covered. Electrical pulses derived from the odometer 20 are counted until a pre-set value is reached. This pre-set value is pre- loaded onto the vehicle 12 to correspond to the distance at which deployment is desired.

When the pre-set value is reached, an electrical command opens the solenoid valve in the ejection device 22, thereby releasing the spring in the ejection device 22.

The action of the spring is augmented hydraulically by an arrangement comprising a channel between the front 26 face of the vehicle and the chamber 14 which makes use of the differential pressure between the rear 16 and front 26 faces of the vehicle 12. The resulting force from the hydraulic pressure and the spring forces a sensor unit 24 from the rear 16 of the vehicle.

If required, a number of a sensor units 24 may be carried on a single conveying pig vehicle 12 to be deployed at successive locations, depending on the conditions sensed in the pipeline 42 by the external sensor 20. In this embodiment sensor 20 would not be an odometer but would measure a condition within the pipeline 42 and once that condition was detected or a pre-set level reached the ejection device 22 would be activated. To achieve the launching of successive sensor units 24 an embodiment of

the invention would include in chamber 14 of the vehicle 12 a multi-chamber carrier (not shown), which is moved step wise to align successive sensor units 24 with an opening through which they are deployed.

On deployment from the vehicle 12, the sensor unit 24 orientates itself against the pipeline 42 wall due to its offset centre of mass, or alternatively via the magnets 38. The coating (not shown in Fig 2) on coming into contact with the contents of the pipeline dissolves. The sensor unit 24 remains in the one location while the sensors 34,36 sense one or more conditions in the pipeline 42. Due to the relatively small size, the streamlined, spherical shape and the location of the units 24 they do not obstruct the flow of the contents of the pipeline through the pipeline 42. The spherical shape further ensures that drag and other forces exerted by the fluid on the unit 24 are less than on a flat-faced unit of similar dimensions, and are independent of the orientation adopted by the unit 24.

Signals from the sensors 34,36 are processed in the signal processing unit 40 to provide data representative of the conditions in the pipeline 42. These data are continuously acquired at intervals over a time period.

The data are stored on a microchip in the unit 40 and transmitted via a transmitter to a receiver operating station (not shown) some distance away from the pipeline 42. In the preferred embodiment the data are transmitted via an electro-magnetic signal as is known in the art.

Alternative signal transmission means may be used such as acoustic, nuclear or the like.

After a time period the sensor unit 24 is retrieved from the pipeline 42. In the preferred embodiment this is achieved by passing a retrieval vehicle 44 through the pipeline 42. The retrieval vehicle 44 is a typical pigging vehicle with the addition of permanent magnets 46. The magnets 46 are mounted toward the front and underside of the vehicle 44 so that the sensor unit 24 becomes attached to the vehicle 44 via the magnets 46 as the vehicle 44 travels over the sensor unit 24. The vehicle 44 may collect more than one sensor unit 24 as it passes through the pipeline 42. The vehicle 44 exits the pipeline 42 via a pig trap (not shown) or other suitable apparatus. The data stored on the microchip in the sensor unit 24 may then be downloaded.

In an alternative embodiment the sensor units 24 include release mechanisms which allow the sensor unit 24 to detach itself from the pipeline wall after a period of time. Where the sensor unit 24 is attached via magnets 38 these will be demagnetised to effect release. Where an offset centre of mass has been used, release is effected by the movement of internal weights to provide a symmetrical centre of mass. Alternatively release of gas into a buoyancy chamber within the sensor unit 24 will reduce the submerged weight of the unit 24 and it will float in the contents of the pipeline. When released, the sensor units 24 travel in or on the contents of the pipeline and may be retrieved downstream.

The embodiments disclosed above are merely exemplary of the invention, which may be embodied in different forms.

Therefore, the details disclosed herein are not to be interpreted as limiting, but merely as a basis for the

Claims and for teaching one skilled in the art as to the various uses of the present invention in any appropriately designed structure.