WO2015118326A1

WO2015118326A1 - Sensor system

Info

Publication number: WO2015118326A1
Application number: PCT/GB2015/050307
Authority: WO
Inventors: Brendan Peter Hyland; Grant MCLEAN
Original assignee: Wfs Technologies Ltd
Priority date: 2014-02-04
Filing date: 2015-02-04
Publication date: 2015-08-13

Abstract

A sensor system for mounting on a pipe, the sensor system comprising a sensor unit having at least one sensor for sensing a criteria, such as temperature or vibration, associated with the pipe, a securing mechanism for securing the system to the pipe, an isolation mechanism for isolating the at least one sensor from an ambient environment surrounding the pipe, and a resilient biasing member operable to act upon the at least one sensor, wherein the at least one sensor is resiliently biased against an outer surface of the pipe. Sensed data can be transmitted as a wireless electromagnetic and/or magnetic signal to a remote receiver located on an ROV or AUV.

Description

SENSOR SYSTEM

The present invention relates to a sensor system and, in particular, to a sensor system for mounting upon a pipe in a secure, removable, manner.

In the oil and gas production industry, there are many thousands of miles of existing pipeline already in situ which carries produced fluid from the production sites to end facilities where it can be processed or distributed. The temperature of fluid flowing through the pipeline is very often higher than the ambient temperature of the environment surrounding the pipe. Also, the fluid flowing through the pipeline may vary in temperature significantly. Over time it has become apparent that changes in temperature acting upon the pipeline can limit the pipe lifetime.

Overheating of the pipe either internally or externally can cause the pipe to expand and buckle, whereas temperatures which are very low can cause the pipe to contract and it may burst. In addition, the environment in which the pipes are deployed, or the fluid carried through the pipe, can encourage corrosion or fouling, either of which can impact on the performance or lifespan of the pipe. However, the replacement of damaged pipe is a costly process and not only in terms of the manpower and hardware requirements necessary to physically undertake the repair. Carrying out a pipeline repair requires the flow of fluid through the pipe to be stop and, depending on the location and significance of the pipeline, this can result in the stopping of production from an oil or gas site and thus a loss of income.

New pipeline systems typically have integrally fitted temperature sensors so that the temperature of fluid flowing through the pipe can be monitored effectively.

However, much existing pipeline is not supplied with an integral temperature sensor. At the same time, given that fluid typically flows through the pipes on an ongoing basis, it is not practical to retrofit penetrating temperature sensors to pre- installed pipes.

It is an object of the present invention to provide a sensor system for monitoring a pipe which obviates or mitigates at least some of the disadvantages in the prior art.

l According to first aspect of the invention there is provided a sensor system for mounting on a pipe, the sensor system comprising a sensor unit having at least one sensor for sensing a criteria associated with the pipe, a securing mechanism for securing the system to the pipe, an isolation mechanism for isolating the at least one sensor from an ambient environment surrounding the pipe and a resilient biasing member operable to act upon the at least one sensor wherein the at least one sensor is resiliently biased against an outer surface of the pipe.

By isolating the sensor from the ambient environment surrounding the pipe and biasing the sensor resiliently against the pipe, the sensor can record data relating to the measurable criteria which is clearly indicative of the measure of criteria relating directly to the pipeline without any inference from the ambient environment.

Preferably the securing mechanism secures the sensor unit to the outer surface of the pipe arrangement. By securing the sensor unit to the outer surface of the pipe arrangement the sensor unit is able to be a non-invasive monitoring system and therefore there is no need for the flow in the pipe to be interrupted in order for measurements to be taken.

Preferably, the securing mechanism is a magnetic securing means. By having a magnetic securing means, the sensor system can be easily attached and detached from the pipe which will typically be formed of a substantially ferrous material. Preferably, the securing mechanism is a strapping mechanism. A strapping mechanism enables the sensor system to be secured effectively to non-ferrous pipes.

The measurable criteria may include one or more of the following parameters including, but not limited to: stress; tension; upheaval; buckling; pig location;

temperature; riser over-temperature; pressure; noise; movement; flow; corrosion; fouling; wax build-up; flow induced vibration (FIV) and vortex induced vibration (VIV).

The pipe may comprise a single layer pipe wall or may alternatively comprise a multilayer wall structure. The pipe may comprise an inner pipe and an outer coat which substantially encircles the inner pipe. The outer coat may comprise a layer of insulation; the layer of insulation may be of a predetermined thickness. The outer coat may alternatively comprise a layer of protective material.

The isolation mechanism may be a housing having one open side around which is provided a gasket, wherein the sensor unit is located within the housing and the gasket forms a seal between the housing and the pipe such that the at least one sensor is operable to sit directly against the pipe within the sealed housing. A gasket will enable the sensor system to be securely retained directly against the pipeline whilst isolating the sensor unit from the ambient environment surrounding the pipe. The isolation mechanism may comprise at least one layer of resiliently deformable material.

Preferably the gasket is formed of a resiliently deformable material. Having a gasket formed of resiliently deformable material enables a seal to be formed between the sensor unit and the ambient environment surrounding the pipe where the pipe may have any one of a range of diameters.

The isolation mechanism and the gasket may be integrally formed of the same resiliently adaptable material. Such an integrally formed isolation mechanism and gasket may enable the sensor system to be applied to a range of different pipes having different diameters. The isolation mechanisms may further comprise a protective layer, the protect layer may include an insulation layer. The isolation mechanism insulation layer may be substantially equal to or greater than in thickness than the pipe insulation layer thickness.

By providing such an insulation layer to the isolation mechanism the isolated area is able to retain the heat of the oil in the pipe, the effect of temperature gradient at the edges of the insulation layer has therefore minimal effect within the sensor area of the isolated area. The thermal resistance of the insulation layer enables the air around the sensor to become heated even when the pipe is already insulated. The sensor unit may further comprise a data logger. A data logger will enable storage of data relating to the sensed criteria.

The sensor unit may further comprise a wireless transceiver. A wireless transceiver will enable the provision of sensed data to remote transceivers. Preferably, each transceiver has an electrically insulated magnetic coupled antenna. Alternatively, each transceiver has an electric field coupled antenna. The antenna may be a wire loop, coil or similar arrangement. Such antenna create both magnetic and electromagnetic fields. The magnetic or magneto-inductive field is generally considered to comprise two components of different magnitude that, along with other factors, attenuate with distance (r), at rates proportional to 1/r² and 1/r³ respectively. Together they are often termed the near field components. The electromagnetic field has a still different magnitude and, along with other factors, attenuates with distance at a rate proportional to 1/r. It is often termed the far field or propagating component. Preferably, the data is transmitted as an electromagnetic and/ or magneto-inductive signal. Signals based on electrical and electromagnetic fields are rapidly attenuated in water due to its partially electrically conductive nature. Propagating radio or electromagnetic waves are a result of an interaction between the electric and magnetic fields. Alternatively, the data may be transmitted through a cabled connection.

The at least one sensor may be one of a selection from a temperature sensor, an acoustic sensor, a vibration monitor and an ultrasonic flow monitor.

Preferably, the sensor unit is provided with at least two sensors. The provision of more than one sensor in the sensor unit enables multiple criteria to be monitored. The sensor system may be provided with at least two sensor units. The provision of two or more discreet sensor units within a sensor system increases the operational flexibility of the system with the ability of different sensors being located in each sensor unit so that different sensors may be applied to discreet different sections of the pipe within a single sensor system.

The sensor system may be battery powered, the battery may be rechargeable and in particular may be inductively rechargeable. Alternatively, the sensor system may be power by means of a cabled connection.

Preferably, the power is transmitted by magnetic coupling between the system transceiver and a remote transceiver. In this way, there is no need for direct electrical conductive contact. More preferably, each transceiver includes a circular coil structure surrounded by a flux guiding enclosure that inductively couples energy from a primary coil in the remote transceiver to a secondary coil in the system transceiver. Preferably, the transferred energy is used to power the sensor and the system transceiver. In this way, there is no limit to the lifespan of the sensor.

As the power transfer is achieved by magnetic coupling while the data transfer is by electromagnetic or magneto-inductive signals, the data can be transferred with the mobile apparatus at a greater distance from the sensor than that required for power transfer. The first and the second range may be approximately equal. In this embodiment, data and power transfer can be simultaneous.

The data may be compressed prior to transmission from the system. In this way the occupied transmission bandwidth can be reduced. This allows use of a lower carrier frequency which leads to lower attenuation. This in turn allows data transfer through fluids over greater transmission distances. In this way, the first range can be increased by lowering the carrier frequency.

Preferably, the data transmission is bi-directional. In this way, command and control signals can be transferred to the sensor system. Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings of which: Figures 1 A, IB and 1C are views of a sensor system according to an

embodiment of the present invention;

Figures 2A, 2B and 2C are views of a sensor system according to an

embodiment of the present invention; Figures 3 A, 3B and 3C are views of a sensor system according to an

embodiment of the present invention;

Figure 4 is a cross section view of a sensor system according to an

embodiment of the present invention;

Figure 5 is a block diagram of a transceiver for use in a sensor system of the present invention, and

Figure 6 is a block diagram of an antenna for use in the transmitter or receiver of the transceiver of Figure 5.

Reference is initially made to Figures 1A, IB and 1C, which illustrate a sensor system, generally indicated by reference numeral 10A according to an embodiment of the present invention. The sensor system 10A is removably attached to a pipeline, in this case a subsea pipe 12, the sensor system 10A being used to monitor the pipe 12.

The sensor system 10A comprises a housing 14 arranged so as to lie substantially horizontally along a section of the length of pipe 12, having a sensor unit 20 attached to a skirt arrangement 21 which is shaped to generally conform with the outer surface 13 of a pipe 12. Within the sensor unit 20, and thus isolated from the external ambient environment 30 is located a sensor, in this case a temperature sensor 22, a resilient biasing member, in this case a spring 24, is arranged to act upon the upper surface of sensor 22 so that the sensor 22 is resiliently biased against the outer surface of pipe 12. Within the unit 20 there is further provided a transceiver 28 which is in communication with the sensor 22 and is able to communicate wirelessly with a remote receiver (not shown). The housing 14 is further provided with a gasket 16 formed of compressible foam sealing material, which fills the space between the housing skirt 21 and the pipe surface 12 and when under compression which acts as a mechanical seal thus preventing leakage of the air or fluid of the ambient environment 30 into the housing 14. The housing 14 is retained against the pipe 12 by magnets 26 which are the securing mechanism that enables the system 10 to be secured to the pipe 12 in an easily removable manner. The placement and removal of the system 10 is facilitated further by the provision of grab handle 27 which can be held by an ROV (not shown) and used to manoeuvre the system 10 into the desirable position for measurements to be taken. The sensor system 10 is further provided with a battery 29 which can be recharged wirelessly by inductive transfer of power to transceiver 28.

Reference is now made to Figures 2A, 2B and 2C, which illustrate a sensor system, generally indicated by reference numeral 10B according to an embodiment of the present invention. Like components shared by sensor system 10A and 10B are referred to with the same reference numerals for the sake of simplicity. System 10B is removably attached to a pipeline, in this case a subsea pipe 12A, which is formed of an inner pipe 30 and an outer pipe insulating layer 32. The outer pipe insulating layer 32 has a thickness a.

The sensor system 10B comprising a housing 14 having a sensor unit 20 attached to a skirt arrangement 21 which is shaped to generally conform with the outer surface 13 of a pipe 12A. Gasket 16 creates a seal which isolates the interior of the sensor

Within the sensor unit 20, and thus isolated from the external ambient environment 30 is temperature sensor 22. It will be understood that one or more additional sensors (not shown) including, but not limited to, an acoustic sensor, a vibration monitor, an ultrasonic flow meter, can be included in the sensor unit 20. The skirt arrangement 21 is provided with an insulation layer 23 which has a thickness b where b is as thick as, or thicker than a. The skirt insulation layer 23 enables the area under the skirt 21 to retain the heat of the oil in the pipeline. The ambient environment 30 is prevented from acting as a coolant in the isolated area where temperature sensor 22 is located, instead the temperature gradient occurs at the outer edges of the skirt 21. Providing the sensor 22 with an insulation layer 23 means that the air around the sensor 22 is able to heat up even when the pipe itself is insulated by pipe insulation layer 32. The thermal resistance function of the skirt insulation layer 23 on a system with a pipe having an insulation layer 32 is comparable to the function of a potential divider in an electrical circuit. By having a skirt insulation layer 23 which is exactly as thick as pipe insulation layer 32 the sensor 22 is able to measure a temperature which is exactly half the temperature of the oil in the inner pipe 30. Increasing the thickness of skirt insulation layer 23 can further provide increased thermal resistance to the isolated environment for sensor 22. By increasing the thermal insulation of the skirt 23 to between five and ten times the thermal insulation of the outer pipe insulation 32, the measurement point of the temperature sensor 22 is approximately the same temperature as the temperature within the pipe bore 13.

Reference is made to Figures 3A, 3B and 3C, which illustrate a sensor system, generally indicated by reference numeral IOC according to an embodiment of the present invention. Like components shared with sensor systems 10A and 10B are referred to with the same reference numerals for the sake of simplicity.

The sensor system IOC is removably attached to a pipeline, in this case a subsea pipe 12, the sensor system IOC being used to monitor the pipe 12.

The sensor system IOC comprising a housing 14 arranged so as to lie substantially horizontally along a section of the length of pipe 12, having a sensor unit 20A disposed at a first end 14A of housing 14 and a second sensor unit 20B disposed at the second end 14B of housing 14, with the sensor unit skirts 21 A, 21B each is shaped to generally conform with the surface of a pipe 12. Each sensor unit skirt 21A,21B is provided with a gasket 16A, 16B respectively. Each gasket 16A, 16B formed of a resiliently deformable material such as a compressible foam sealing material, which fills the space between each housing skirt 21 A, 21 B and the pipe surface 13 and, when under compression, the gasket 16A, 16B acts as a mechanical seal thus preventing leakage of the air or fluid of the ambient environment 30 into the void 25 within sensor units 14A, 14B. Within each the void 25 A, 25B of sensor unit 20A, 20B respectively, and thus isolated from the external ambient environment 30 is located a sensor, in this case a temperature sensors 22A, 22B respectively and a resilient biasing member, in this case springs 24A, 24B respectively are arranged to act upon the upper surface of sensor 22A, 22B so that the sensor 22A, 22B is resiliently biased against the outer surface 13 of pipe 12. Within the housing 14, there is further provided a transceiver 28 which is in communication with the sensors 22A, 22B. The transceiver 28 is able to communicate wirelessly with a remote receiver (not shown). The sensor units 20 A, 20B are retained against the pipe 12 by magnets 26 A, 26B which are the securing mechanism that enables the system 10 to be secured to the pipe 12 in an easily removable manner. The sensor system 10 is further provided with a battery 29 which can be recharged wirelessly by inductive transfer of power to transceiver 28. The provision of a sensor system IOC with two sensor units 20A, 20B which are spaced discreetly apart, enables the sensor system IOC to effectively monitor, at the same time, separate sections of same pipe 12. This sensor system IOC may be of particular value in monitoring sections of pipeline where there is the likelihood of a sudden differential of behaviour between the two disparate points on the pipe, for example two spaced apart temperature sensors 22A, 22B could monitor a section of pipeline arranged immediately after a choke valve in order to monitor any sudden temperature differential that occurs along the section of pipe when the choke is opened. Similarly, accelerometers, vibration monitors, audio sensors of the like could also be of value in monitoring the progressive behaviour of a particular mechanical or physical aspect of the pipe or the fluid flowing within it along the length of pipeline.

Reference is made to Figures 4A, 4B and 4C, which illustrate a sensor system, generally indicated by reference numeral 10D according to an embodiment of the present invention. Like components shared with sensor systems 10A, 10B or IOC are referred to with the same reference numerals for the sake of simplicity.

The sensor system 10D is removably attached to a pipeline, in this case a subsea pipe 12, the sensor system 10D being used to monitor the pipe 12.

The sensor system 10D comprising a housing 14, arranged so as to project radially away from the pipe 12, having a sensor unit 20 disposed at a first end 14C of housing 14 with the sensor unit skirts 21C arranged to sit between the sensor unit 20 and pipe 12. The arrangement of the sensor system 10D to extend radially from the pipe surface 13 results in footprint of the sensor system 10D on the pipe surface 13 being considerably smaller than for sensor system arrangements 10A and IOC for example. This means that the sensor system 10D can be effectively deployed in positions where the pipe surface area available is limited or constrained.

The skirt 21C of sensor system 10D is formed of a resiliently deformable material such as a durable rubber material and is shaped to generally conform with the surface of a pipe 12. The resiliently deformable material of the skirt 21C enables the skirt 21C to deform to the extent that the skirt 21C can conform to a range of different pipe diameters. The sensor unit skirt 21C is provided with a gasket 16C which in this case comprises corrugated, or tread like, projections formed in the skirt 21C corresponding with the opening in the skirt 21C around the base end 14C of the housing. The skirt 21C and gasket 16C are integrally formed of a dense, resiliently deformable material such as a rubber based material which enables the gasket to act as sealing material, which fills the space between each housing skirt 21C and the pipe surface 13 so that when under compression, the gasket 21C acts as a mechanical seal thus preventing leakage of the air or fluid of the ambient environment 30 into the void (not shown) within sensor unit 20C. The components arranged within sensor unit 20C are such as has been described with reference to Figures 1, 2 and 3.

Reference is now made to Figure 5 of the drawings which illustrates the parts of transceiver 28. In transceivers 28 the sensor interface 56 receives data from the measurement systems in the sensor 22 which is forwarded to data processor 58. Data is then passed to signal processor 60 which generates a modulated signal which is modulated onto a carrier signal by modulator 62. Transmit amplifier 64 then generates the desired signal amplitude required by transmit transducer 66. The transceiver 28 can send data or command signals to the data processor 58 of the remote transceiver (not shown) which are transmitted by the above described path. These command signals can be used by the remote receiver (not shown) which is likely to be mounted on an AUV, to detect the location of a wireless transceiver 22 to determine if the transceiver 28 is within proximity or range to transmit data and/ or power.

Transceivers 28 also has a receive transducer 70 which receives a modulated signal which is amplified by receive amplifier 72. De modulator 74 mixes the received signal to base band and detects symbol transitions. The signal is then passed to signal processor 76 which processes the received signal to extract data. Data is then passed to data processor 58 which in turn forwards the data to control interface 68. Transceiver 28 can also be provided with a memory 78 which can store data for onward transfer. Figure 6 is an illustration of an example of an antenna 79 that can be used with the transceiver 28 of Figures 1, 2, 3 and 4. This has a high permeability ferrite core 80. Wound round the core are multiple loops 82 of an insulated wire. The number of turns of the wire and length to diameter ratio of the core 80 can be selected depending on the application. However, for operation at 125 kHz, one thousand turns and a 10:1 length to diameter ratio is suitable. The antenna is connected to the relevant transmitter/ receiver assembly parts 28 described in Figure 5 and is included in a sealed housing 84. Within the housing the antenna may be surrounded by air or some other suitable insulator 86, for example, low conductivity medium such as distilled water that is impedance matched to the propagating medium which in this case is ambient environment 30. The antenna can also be used to magnetically couple energy between the transceiver 28 of the system 10 and a transceiver 28 of and ROV (not shown). In this regard the housing acts as a magnetic flux guide and the multiple loops 82 with the ferrite core 80 provide a transformer when a pair of transceivers are brought together. In order for successful energy transfer the two transceivers must be arranged close together, there being an acceptable gap of only l-2cm. Thus the range for power transfer is much smaller than the range for data communication. Coupling efficiency reduces as frequency increases because of leakage inductance effects. Eddy current losses increase with frequency so also act to reduce the bandwidth available for data transmission. Data and power transmission can be separated in frequency to allow simultaneous operation of the two functions. Transfer efficiency is more critical for power transfer than for data communication applications so a higher frequency will usually be assigned to the data

communication signals. While transceiver 28 is described with a common antenna for transmit and receive, separate antennas may be used. Additionally, a separate transmitter coil arrangement can be provided solely for power transfer.

In use, the sensor system 10 is retrofittable to pipe 10 and enables the sensor 22 to be held in an environment protected from the ambient environment 30 such that the temperature of the fluid flowing through the pipe 12 can be measured without the temperature of the environment affecting the sensed value. Similarly, other sensors such as acoustic sensors and vibration sensors can be isolated from the ambient environment 30 in order to measure the necessary criteria required of pipe 12. The sensed criteria can be recorded as data and subsequently the transceiver 28 may provide the recorded data to a remote receiver such as an ROV, either upon interrogation or by emitting an output at a regular predetermined interval. As a retrofittable system, the sensor system 10 is non-invasive and can monitor measurement criteria on a spot check basis or over a long period of days, weeks, months or years to build up a data set for analysis and monitoring purposes. The use of electromagnetic and/ or magnetic signal transmission means that data can be transmitted through fluid effectively. Should the pipeline 12 and sensor system 10 be deployed in a subsea environment where they are provided with a concrete blanket (not shown) the use of electromagnetic and/ or magnetic signal transmission means that data can be transmitted effectively through both the concrete blanket and surrounding fluid in order to be received by a system such as a diver or deployed ROV or AUV sent to harvest the recorded data. The data can be recorded when specific sensor triggers, such as predetermined levels or variation parameters are exceed or met or at predetermined time intervals or upon demand by a ROV or the like which has come into proximity of the sensor system 10.

The use of wireless electromagnetic and/ or magnetic signal transmission means also can aid in the monitoring of complex subsea activities as wireless transmission means that the safety hazard of umbilicals being snagged from multiple ROVs can be avoided and can remove the complex manoeuvring required in forming connections with hot stab connectors.

As the system 10 is retrofittable, any sensors 22 which become obsolete or damaged can be replaced more simply, and at a far lower cost than for integrated sensor systems by removal of the system 10, refurbishment of the system 10 to include an operational sensor 22 and redeployment and refitting of the sensor system 10 upon the pipeline 12.

Temperature sensors 22 may not always enable the sensor system 10 to determine the exact temperature within the pipe 12 which is being monitored however in such cases that temperature sensors 22 are not able to provide an exact indication of temperature they are still able to give an accurate indication of relative temperature variation which will be in parallel with temperature variation occurring within the pipe 12.

As well as a temperature sensor, which can provide data that would be useful in the monitoring of temperature for the purposes of ongoing function or the potential for buckling or fracturing of the pipeline, the sensor system 10 can be provided with sensors a variety of other sensors to enhance the monitoring of a submerged pipeline or buried pipeline.

The sensors which may be deployed within the sensor system may included but not be limited to sensors such as ultrasonic thickness sensors with either one, or multiple sensors being deployed within a single system 10.

One or more accelerometers can be provided and these can monitor behaviour such as flow and vortex induced vibrations.

An Acoustic Doppler current profiler or ultrasonic flow sensor system can be provided to monitor the flow velocity within the pipeline and, over time, this data can be used to monitor any reduction in flow velocity which may indicate an impedance occurring within the pipe bore such as wax build up, fouling or the like. Acoustic lead detection sensors can be deployed within sensor systems 10 along the length of a pipe at predetermined intervals and an alarm system can be integrated with the sensor system 10 to identify instances when significant leaks are

determined to be occurring. A repeater system (not shown) can be deployed local to the sensor system 10, for example outwith a concrete blanket, such that the electromagnetic and/ or magnetic signals can be provided to the repeater which then transmit the signal onward using a different communication technique such as acoustic transmission, optical transmission, cabled transmission or using electromagnetic and/ or magnetic transmission.

Integrated voltage and current sensors (not shown) can be provided in the sensor system 10 to aid in cathode protection monitoring. A sensor system 10 with cathodic protection monitoring sensors can be deployed environments including upon buried pipelines, within manifolds and inside caissons as well as on submerged pipelines thus enabling cathodic protection monitoring in otherwise inaccessible, or difficult to access, pipes.

The sensor system 10 can be provided with a local processing mechanism such as processor 58 where it may be acted upon to assess the necessity to generate an alarm signal or the like. The principle advantage of the present invention is that it provides a sensor system for retrofitting to a pipe and which can be isolated from the ambient environment in order to record true data relating to a criteria of the pipe such as the temperature of the fluid flowing within. The data can be harvested and the sensors recharged wirelessly. A further advantage of at least one embodiment of the present invention is that it provides a sensor system which can be simply and effectively, yet securely, attached and detached from a pipe thus enabling short, medium or long term depending on the site requirements. It will be appreciated by those skilled in the art that various modifications may be made to the invention herein described without departing from the scope thereof. For example, the sensor system may be secured to a pipe using magnets as detailed above, however, alternatively a strap or clip arrangement may be used to secure the system 10 to the pipe 12. The ultrasonic flow meter which may be included in the sensor unit 20 may be utilised to detect flow rate of fluid through the pipe being monitored so that any localised or general silting of the pipe line may be determined. A vibration monitor which may be included in the sensor unit 20 can be used to determine if vibration is occurring and whether it is intermittent, environmental or consistent as well as whether any changes in vibration are experienced thus allowing an assessment of the cause of vibration to be made if needed. An acoustic sensor which can be included in the sensor unit 20 may be used to detect noise occurrence from within or acting upon the pipe. Whilst magnets have been described as being used to secure the sensor system 20 to the pipe, thus enabling a "drop on, peel off" manner of deployment, the facility can also be provided to enable more resilient manners of securing including for example, tie wraps, circlips, straps or the like.

Claims

1. A sensor system for mounting on a pipe, the sensor system comprising: a sensor unit having at least one sensor for sensing a criteria associated with the pipe;

a securing mechanism for securing the system to the pipe;

an isolation mechanism for isolating the at least one sensor from an ambient environment surrounding the pipe, and

a resilient biasing member operable to act upon the at least one sensor, wherein the at least one sensor is resiliently biased against an outer surface of the pipe.

2. A sensor system as claimed in claim 1 wherein the securing mechanism secures the sensor unit to the outer surface of the pipe arrangement.

3. A sensor system as claimed in claim 1 or claim 2 wherein the securing mechanism is a magnetic securing means.

4. A sensor system as claimed in claim 1 or claim 2 wherein the securing mechanism is a strapping mechanism.

5. A sensor system as claimed in any preceding claim wherein the measurable criteria may include one or more of the following parameters including, but not limited to: stress; tension; upheaval; buckling; pig location; temperature; riser over- temperature; pressure; noise; movement; flow; corrosion; fouling; wax build-up; flow induced vibration (FIV) and vortex induced vibration (VI V).

6. A sensor system as claimed in any preceding claim wherein the isolation mechanism is a housing having one open side around which is provided a gasket, wherein the sensor unit is located within the housing and the gasket forms a seal between the housing and the pipe such that the at least one sensor is operable to sit directly against the pipe within the sealed housing.

7. A sensor system as claimed in any preceding claim wherein the isolation mechanism comprises at least one layer of resiliently deformable material.

8. A sensor system as claimed in claim 6 wherein the gasket is formed of a resiliently deformable material.

9. A sensor system as claimed in claim 6 wherein the isolation mechanism and the gasket are integrally formed of the same resiliently adaptable material.

10. A sensor system as claimed in any preceding claim wherein the isolation mechanism further comprises a protective layer.

11. A sensor system as claimed in claim 10 wherein the protective layer includes an insulation layer.

12. A sensor system as claimed in claim 11 wherein the isolation mechanism insulation layer is substantially equal to or greater than in thickness than a pipe insulation layer thickness.

13. A sensor system as claimed in any preceding claim wherein the sensor unit further comprise a data logger.

14. A sensor system as claimed in any preceding claim wherein the sensor unit further comprise a transceiver.

15. A sensor system as claimed in claim 14 wherein the transceiver operable to provide data relating to the sensed criteria to at least one remote transceiver.

16. A sensor system as claimed in claim 14 or claim 15 wherein the transceiver is a wireless transceiver.

17. A sensor system as claimed in claim 16 wherein the data is transmitted as an electromagnetic and/ or magneto-inductive signal.

18. A sensor system as claimed in any one of claims 1 to 5 wherein the data is transmitted through a cabled connection.

19. A sensor system as claimed in any preceding claim wherein the at least one sensor comprises one of a selection from a temperature sensor, an acoustic sensor, a vibration monitor and an ultrasonic flow monitor.

20. A sensor system as claimed in any preceding claim wherein the sensor unit is provided with at least two sensors.

21. A sensor system as claimed in any preceding claim wherein the sensor system is provided with at least two sensor units.