GB2623048A - Sensor monitoring system - Google Patents

Abstract

A sensing device 25 coupled to a sensor electronics module of a subsea sensor (fig 2) to monitor environmental conditions. The device comprising one or more status sensors 33 e.g. temperature sensor, pressure sensor, acceleration sensor, clinometer or humidity sensor. The sensing device having a local data store 35, at least one power supply input 34 and at least one data output 36. The power supply input is adapted to receive power form a power supply within a housing of the subsea sensor. Preferably, the sensing device is part of a subsea sensor monitoring system which comprises operational sensors e.g. erosion or corrosion sensors. The status sensing device is preferably used to monitor conditions during transit or shipping. Also, a method of monitoring the status of a subsea sensor is disclosed.

Description

SENSOR MONITORING SYSTEM

This invention relates to a method and system for monitoring of a sensor, in particular for a subsea, or underwater sensor.

In oil and gas exploration, pipelines laid subsea are difficult to access and expensive to maintain or repair, requiring hire of specialised vessels and use of divers. However, over time, the pipeline may gradually wear, typically due to erosion or corrosion of the pipeline material, or the conditions within the pipeline may alter, requiring a change to the process flow, so subsea sensors are used to determine any changes to the state of the subsea pipeline, or the fluid flow within it, enabling steps to be taken to mitigate damage, or for repairs to be scheduled when a vessel is going to be on site for other reasons. As these sensors must be relied upon, it is desirable to monitor the sensors themselves, in case there is a fault or damage has caused the sensor to stop working correctly at some point in its lifecycle In accordance with a first aspect of the present invention, a status sensing device adapted to be coupled to a sensor electronics module of a subsea sensor comprises one or more status sensors, a local data store, at least one power supply input and at least one data output; wherein the at least one power supply input is adapted to receive power from a power supply within a housing of the subsea sensor.

The status sensors may comprise at least one of a temperature sensor, a pressure sensor, an acceleration sensor, a clinometer, a magnetic field sensor, or a humidity sensor.

The internal power supply may comprise a battery, an energy harvesting device; a Peltier element; or an energy storage module.

In accordance with a second aspect of the present invention, a subsea sensor monitoring system comprises a status sensing device according to the first aspect and a data communications link connected to the data output, the link adapted to couple the device to a control unit at a remote location.

In accordance with a third aspect of the present invention, a subsea sensor comprises a housing, sensor electronics, operational sensors and a power supply input; wherein the sensor further comprises a sensor status sensing device of any of claims 1 to 3.

The operational sensors may comprise at least one of an erosion or corrosion sensor, a pressure sensor, or a temperature sensor.

The power supply may comprise an external power supply, coupled to the sensor through a penetrator or electrical feedthrough.

The housing may comprise a metal, in particular super duplex stainless steel, alloy 625, or a composite.

In accordance with a fourth aspect of the present invention, a method of monitoring status of a subsea sensor comprises providing a status sensing device in the body of the subsea sensor, the device comprising one or more status sensors; detecting events which cause any of the one or more status sensors to exceed a predetermined threshold value, or produce values outside a predefined range; recording the data from the status sensor produced by the event, accessing the data at selected points in the lifecycle of the sensor; and determining whether or not the sensor is still operating reliably.

The step of accessing the stored data may comprise connecting a mobile device to a data output of the status sensing device and downloading and displaying the data on the mobile device.

The step of accessing the data may comprise connecting a data communications link to a data output of the status sensing device and requesting a download of stored data from the data store to a remote or central control unit.

Figure 1 illustrates an example of a typical subsea pipeline system in which subsea sensors may by monitored by a system according to the present invention; Figure 2 illustrates a first example of a subsea sensor, including a monitoring system according to the present invention, Figure 3 illustrates a second example of subsea sensor, including a monitoring system according to the present invention; Figure 4 illustrates more detail of a status sensing device according to the present invention, Figure 5 is a flow diagram illustrating a method of monitoring a subsea sensor, according to the present invention.

The drive to reduce overall lifecycle costs, both capital expenditure (CAPEX) and operational expenditure (OPEX), associated with deep-water oil and gas developments means that improvements to existing designs, manufacturing processes and operation are desirable. Reducing operational costs of maintenance of subsea equipment relies on remote monitoring of the status of the equipment and adapting the operation to reduce the rate of wear, or scheduling equipment replacement to coincide with other works that also require vessel or diver services, to reduce the overheads.

Conventionally, subsea sensors, such as erosion or corrosion sensors having a single sensor, which is subjected to the same harsh environment as the equipment or pipeline being monitored and a second, reference, sensor that is protected from that environment and allows a comparison to determine the state of the pipeline, or combined pressure and temperature sensors have been used to detect changes in the fluid flow, or the pipeline. Long term and reliable functionality is critical for subsea sensors because of the high costs involved with well shut ins and difficulties with product retrieval, for maintenance, after installation. Once subsea sensors leave the factory, the manufacturer and end customer ultimately rely upon the shipping company to handle the product with due care. If the sensors are damaged in transit, this may affect their longevity, but without that damage being immediately visible. Also, once the sensor has reached the customer, monitoring the product up to the point of first power up, is not possible. The end customer has no means of knowing how the sensor has been handled in transit, or before deployment and cannot be sure that it has not been dropped, or otherwise mistreated Unknowingly installing a sensor that is not able to survive for its design lifetime, may lead to significant costs, perhaps running to hundreds of thousands, or millions of dollars, if they fail in their sensing role, unexpectedly, or, if the sensors or the pipelines they are designed to protect, have to be replaced outside scheduled maintenance periods.

EP2592219A1 relates to monitoring of subsea control modules, before deployment, using a power supply that would not be used once deployed, whereas the present invention monitors subsea sensors during their operational lifetime, by active, rather than passive means.

EP271873 1 B1 describes a label which holds a fluid in a reservoir and in the event of an impact that exceeds a predetermined amount, the fluid wicks into a capillary gap to provide a visual indicator that an impact has occurred. However, use of this type of label, when mounted onto shipping boxes for sensors, does not give an accurate reading of what forces the actual sensors have been subjected to. Also, this method gives no indication of whether an impact has occurred after the sensor has been removed from the shipping box.

The absence of a way to provide a reliable indication of actual impact forces suffered by sensors throughout the pre-deployment period has resulted in sensors being required to meet a higher level of qualification, with an increased focus on robustness, often resulting in increased cost.

Fig.1 illustrates a typical installation in which an operational subsea sensor 1, for example an intrusive wear sensor, such as an erosion/corrosion sensor, or a pressure and/or temperature sensor, may be installed. One or more such sensors 1, each comprising one or more sensing elements, according to the type of sensing being carried out, may be installed in a pipeline 2 or other media carrying body. For wear sensors, the sensing element is exposed to process media, as indicated by the direction of flow arrow 14, which may for example, comprise a process fluid such as gas, or oil, together with water, as well as sand and/or chemicals. For pressure or temperature sensors, the sensing element is as close as possible too, but not actually in, the process fluid flow. For corrosion/erosion sensors, sand, in particular, may cause erosion of the pipeline and erosion is affected by the rate at which the sand and other material flows through the pipeline 2. Corrosion may be caused, for example, by sour service process media that is too harsh for the material grades used. Components downstream of the sensor may have been mechanically damaged by some other cause, which may also produce particles that wear down the pipeline and other wetted parts. Having multiple sensors in the pipeline allows particular issues to be located more easily, although an alternative would be to have a single sensor where the process media enters a pipeline section.

Data from the, or each, sensor may be collected in a control centre 3, the data being received at the control centre via communications lines 4. The control centre may be either subsea or topside, or at a remote location, for example when used as a part of an automated condition monitoring system. The received data may be monitored by operators or to automated to some extent. When detrimental erosion, or corrosion, rates are detected, or unexpected readings of pressure and/or temperature, the operator may send a control signal to the control centre and through communications lines 4 to a valve actuator 5, upstream of the sensor to change the flow rate of the process media in the pipeline section. Reducing the flow rate, typically reduces wear, but also reduces the rate at which the produced fluid is obtained, so lower flow rates have cost implications. In an automated system, the changes may be made in response to a trigger value being reached. Accurate measurement of the rate of erosion, or corrosion, allows changes to be made to the extraction process to reduce the amount of damage being done, if the rate of erosion of the pipeline is deemed to be too high All this information is only useful and made possible, if the sensor are operating correctly when deployed subsea. In order to ensure that the sensor works as well as expected, it is desirable to be able to monitor how that sensor has been treated before it is deployed. The present invention addresses this problem by providing the subsea sensor with at least one additional sensor located within the housing of the sensor. This is illustrated in more detail in Fig.2.

Fig.2 shows an example of a subsea sensor 1, in this case, a pressure and temperature sensor, designed to be mounted in a bore through a wall of a pipeline 2, or other subsea equipment that is being monitored by the sensor I. The sensor body 10 comprises a housing flange 11 for mounting the sensor onto the bore to the process fluid pipeline 12. The body 10 and flange 11 typically comprise a corrosion resistant metal, such as super-duplex stainless steel, which may be produced by forging, then machined to its final shape. The flange 11 is mounted to the bore of an operational sensor 20. Between the flange 11 and a housing 24 around the cylindrical body 13 are inlay welds 16, in this example, in alloy 625, as well as a BX gasket area 17 of the sensor flange I. The BX gasket is designed to meet appropriate standards requirements, such as API 6A. A pressure sensing element 22 is provided across the end of a cylindrical body 13 extending from the base of the sensor flange 11. The pressure sensing element is typically a flexible, corrosion resistant, steel membrane, such as super-duplex stainless steel. Flexibility is provided by making the membrane very thin, of the order of 0.1mm. The cylindrical body 13 passes through the bore of sensor 20 and housing 24 to the edge of the pipeline. The cylindrical body 13 may also be formed from corrosion resistant steel, by machining. Within the cylindrical body 13, centred about its longitudinal axis 21, a tube 15 transmits data from the pressure sensor back to sensor electronics 23 in the sensor body 10. Temperature data is detected on the surface of the body 13, within the bore of sensor 20 and fed back to the sensor electronics 23 of the process fluid pipeline and exposes the sensing element to the process fluid, indicated by the arrow 14.

In an alternative example of an operational sensor, shown in Fig.3, a wear sensor 30 is illustrated. The wear sensor comprises one or more wear sensing elements 31, which are exposed to the process fluid in the pipeline 2 and a reference sensing element 32 which is mounted in a section of the sensor body away from the process fluid. Resistance measurements across the sensing element 31 and across the reference sensing element 32 are communicated to the sensor electronics 23 within the sensor housing body 10 and can be compared to determine the rate of change of the exposed sensing element and from that derive the rate of wear in the pipeline. The reference sensing element 32 is protected from the direct fluid flow, but otherwise experiences the same environment as the sensing element 31.

In both examples, an additional condition monitoring and sensor device 25, including a data store, is mounted between an inner surface of the housing body 10 and the sensor electronics 23 to provide a record of how the sensor has been treated since it was manufactured. In order to extract electrical signals subsea, whether for power, data, or communications, either a penetrator -a pressure barrier providing a continuous electrical connection through a wall or equipment housing subsea, or a feedthrough -an electrical connection passing through a barrier subsea to pass power or communication through the barrier, must be used. The sensors 20, 30, when deployed and in use, or when under test, are connected to a mains power supply 29 through a penetrator or electrical feedthrough 28. However, there will be times, for example when in transit, that it would be impossible to be connected to that mains supply. For that reason, the sensor 20, 30 needs an internal power supply 26, which may only need to be used when the external power supply 29 is not connected, in order to conserve the power available for when there is no alternative. In other cases, the sensors 20, 30 may be powered by either an external or internal battery, in the body 10 of the sensor that is not in the pipeline 2 and the main battery also powers the additional sensors for a short period of time, deemed sufficient to cover shipping times and time taken for installation. Alternatives to the internal battery, include an energy harvesting device which is able to scavenge ambient energy, such as from movement or vibration during transport, or from ambient heat, or light and use or store that energy, a Peltier element to take advantage of temperature differentials; or other types of energy storage module, such as capacitors.

The additional sensors installed in the condition monitoring and sensor device 25 may measure such things as temperature, pressure, acceleration (to indicate shock or vibration), angular positioning (to indicate tilt), magnetic field (to indicate power up) and humidity. The device 25 ensures that even after delivery, the sensor 20, 30 is constantly monitoring and logging this sort of data, either until the external battery 29 is disconnected or until the internal battery 26 no longer contains enough charge to continue functioning. As explained above, the sensors 20, 30 are designed to provide data to a remote central controller 3, or other destination, by which the pipeline can be monitored. Thus, the data logged within the store of the device 25 may also be accessed remotely, giving the user the opportunity to determine whether long term functionality has been compromised. The monitoring works both when connected to an external power supply, or not. For example, a handheld test unit could be connected to the data input, where no external power supply is present and still download the stored data. This allows the device to monitor the treatment of the sensor from manufacture, through shipping, storage, installation and operation. With a long enough battery life, the device 25 can store data about how the sensor 20, 30 has been treated over its whole lifetime. The data store may be designed to prevent data being overwritten, so that warranty claims can be assessed. Event driven communications or recording of data may be used to reduce the drain on the internal battery. More detail of the status sensing device 25 can be seen in Fig.4. The device 25 comprises one or more sensors 33, each of which is powered from whichever power supply 26,29 is connected to the power supply input 34, either the internal or external power supply. The sensors are able to send data to the data store 35 in response to a trigger, typically detection of an event that exceeds a threshold for that sensor, or falls outside, a permitted range for that sensor. When connected to an external data link, data from the store 35 may be output via the data output 36.

A method of operation of the sensor monitoring system is described with respect to the flow diagram of Fig.5. On completion of all factory tests 40 before the sensor is dispatched to the customer, the fully operational status of the sensor may be indicated and stored 41 in the data store of the status sensing device 25. The sensor 20, 30 is then packed and dispatched. In transit, or when stored, prior to deployment, the internal power supply enables the sensors in the status sensing device to operate, recording events 42 in the data store, in response to any of the sensors detecting a value that exceeds a predetermined threshold or falls outside a predefined range, indicating the possibility of damage. Checks 43 can be made on the sensor before the sensor is finally deployed, either by connecting a handheld data reader to the data output 36, or by connecting the sensor to the remote or central controller 3 via a data link. The stored data is read from the store 35 and checked. Provided that there is no indication of damage that might compromise the operation of the sensor, then the sensor can be deployed 44. Optionally, the system may be set up to request data at intervals to ensure that no harm has come to the sensor in the meantime and that it is still operating effectively.

The present invention addresses the need for an effective monitoring system to ensure that a sensor is not damaged after leaving the factory, so that it can be deployed subsea with confidence that it still complies with the necessary performance requirements, as tested. This may enable the design criteria to be less stringent, so reducing manufacturing costs, without any loss of performance.

While the present invention has been described above by reference to various embodiments, it should be understood that many changes and modifications can be made to the described embodiments. It is therefore intended that the foregoing description be regarded as illustrative rather than limiting, and that it be understood that all equivalents and/or combinations of embodiments are intended to be included in this description.

The foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention disclosed herein. While the invention has been described with reference to various embodiments, it is understood that the words, which have been used herein, are words of description and illustration, rather than words of limitation. Further, although the invention has been described herein with reference to particular means, materials, and embodiments, the invention is not intended to be limited to the particulars disclosed herein; rather, the invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims. Those skilled in the art, having the benefit of the teachings of this specification, may affect numerous modifications thereto and changes may be made without departing from the scope of the invention in its aspects.

It should be noted that the term "comprising" does not exclude other elements or steps and "a" or "an-does not exclude a plurality. Elements described in association with different embodiments may be combined. It should also be noted that reference signs in the claims should not be construed as limiting the scope of the claims. Although the invention is illustrated and described in detail by the preferred embodiments, the invention is not limited by the examples disclosed, and other variations can be derived therefrom by a person skilled in the art without departing from the scope of the invention.

Claims (11)

1. CLAMS1 A status sensing device adapted to be coupled to a sensor electronics module of a subsea sensor, the device comprising one or more status sensors, a local data store, at least one power supply input and at least one data output; wherein the at least one power supply input is adapted to receive power from a power supply within a housing of the subsea sensor.
2. 2. A device according to claim 1, wherein the status sensors comprise at least one of a temperature sensor, a pressure sensor, an acceleration sensor, a clinometer, amagnetic field sensor, or a humidity sensor.
3. 3. A device according to claim 1, wherein the internal power supply comprises a battery, an energy harvesting device; a Peltier element; or an energy storage module.
4. 4. A subsea sensor monitoring system comprising a status sensing device according to any preceding claim; and a data communications link connected to the data output, the link adapted to couple the device to a control unit at a remote location
5. 5. A subsea sensor comprising a housing, sensor electronics, operational sensors and a power supply input; wherein the sensor further comprises a sensor status sensing device of any of claims 1 to 3.
6. 6. A subsea sensor according to claim 5, wherein the operational sensors comprise at least one of an erosion or corrosion sensor, a pressure sensor, or a temperature sensor.
7. 7 A subsea sensor according to claim 5 or claim 6, wherein the power supply comprises an external power supply, coupled to the sensor through a penetrator or electrical feedthrough.
8. 8. A subsea sensor according to any of claims 5 to 7, wherein the housing comprises a metal, in particular super duplex stainless steel, alloy 625, or composite.
9. 9 A method of monitoring status of a subsea sensor, the method comprising providing a status sensing device in the body of the subsea sensor, the device comprising one or more status sensors; detecting events which cause any of the one or more status sensors to exceed a predetermined threshold value, or produce values outside a predefined range; recording the data from the status sensor produced by the event; accessing the data at selected points in the lifecycle of the sensor, and determining whether or not the sensor is still operating reliably.
10. 10. A method according to claim 9, wherein the step of accessing the stored data comprises connecting a mobile device to a data output of the status sensing device and downloading and displaying the data on the mobile device.
11. 11. A method according to claim 9 or claim 10, wherein the step of accessing the data comprises connecting a data communications link to a data output of the status sensing device and requesting a download of stored data from the data store to a remote or central control unit.