APPARATUS, SYSTEM AND METHOD FOR MONITORING SEALING DEVICES

Abstract

The invention in provides an apparatus, system and method of monitoring a sealing device. The apparatus comprises an inlet configured to receive pressurised fluid from a seal activation fluid pressure source and an outlet configured to be connected to a sealing device to deliver pressurised fluid to a seal element of the sealing device to energise the sealing device in use. A fluid barrier is disposed between the inlet and the outlet and is operable to isolate the inlet from the outlet. A fluid chamber is defined between the fluid barrier and the outlet, and the apparatus comprises means for detecting a change in condition in the fluid chamber indicative of a change in volume of the seal element of the sealing device.

Claims

1. An apparatus for monitoring a condition of a sealing device, the apparatus comprising: an inlet configured to receive pressurised fluid from a seal activation fluid pressure source; an outlet configured to be connected to a sealing device to deliver pressurised fluid to a seal element of the sealing device to energise the sealing device in use; a fluid barrier disposed between the inlet and the outlet and operable to isolate the inlet from the outlet, wherein a fluid chamber is defined between the fluid barrier and the outlet; and means for detecting a change in condition in the fluid chamber indicative of a change in volume of the seal element of the sealing device.

2. The apparatus according to claim 1, wherein the detected change in condition in the fluid chamber is a change in volume of the fluid chamber, and wherein the fluid chamber is operable to change in volume in response to a change in volume of the seal element.

3. The apparatus according to claim 2, wherein the change in volume of the fluid chamber is measured, and a change in volume of the seal element is determined from the measured change in volume of the fluid chamber.

4. The apparatus according to claim 1, wherein the fluid chamber comprises a piston chamber, and wherein the fluid barrier is a piston element which forms a seal with an inner wall of the piston chamber and which is movable in the piston chamber in response to a change in condition in the fluid chamber.

5. The apparatus according to claim 4, wherein the piston element has a first piston face exposed to pressurised fluid from the seal activation pressure source and a second piston face exposed to pressurised fluid in the fluid chamber, and wherein the first piston face has a piston area which is smaller than the piston area of the second piston face.

6. (canceled)

7. The apparatus according to claim 4, comprising a linear transducer which is operable to measure the position of the piston element in the piston chamber.

8. The apparatus according to claim 1, wherein the apparatus is configured to recharge the fluid chamber when the fluid chamber reaches a depleted condition.

9. The apparatus according to claim 1, wherein the apparatus is provided with at least one bypass to the fluid barrier, which is operable to fluidly connect the seal activation pressure source to the fluid chamber via the inlet.

10. The apparatus according to claim 9, wherein the at least one bypass comprises a bypass valve which is operable to deliver fluid from the seal activation fluid pressure source to the fluid chamber.

11. The apparatus according to claim 1, further comprising an inlet pressure transducer located between the inlet and the fluid chamber to monitor the pressure of the pressurised fluid which enters the apparatus via the inlet and an outlet pressure transducer located between the fluid chamber and the outlet to measure the pressure of the pressurised fluid delivered to the seal element.

12. The apparatus according to claim 1, further comprising a pressure regulator located between the fluid chamber and the outlet, which is operable to regulate the pressure of the pressurised fluid at the outlet of the apparatus, and therefore to regulate the pressure of the pressurised fluid delivered to the seal element via the outlet.

13. A sealing device monitoring system comprising: a sealing device comprising a seal element, the sealing device operable to be energised by a pressurised fluid from a seal activation pressure source; and an apparatus for monitoring a condition of the sealing device; wherein the apparatus comprises: an inlet for pressurised fluid coupled to the seal activation fluid pressure source; an outlet coupled to the sealing device to deliver pressurised fluid to the seal element to energise the sealing device; a fluid barrier disposed between the inlet and the outlet and operable to isolate the inlet from the outlet, wherein a fluid chamber is defined between the fluid barrier and the outlet; and means for detecting a change in condition in the fluid chamber indicative of a change in volume of the seal element.

14. The system according to claim 13, wherein the sealing device is a slip joint packer and where the seal element is a packer element.

15. The system according to claim 13, further comprising a control module operable to perform at least one of: receiving data and monitoring readings from transducers and/or sensors included in the apparatus; controlling the operation of valves included in the apparatus; performing calculations based on readings obtained from the transducers and/or sensors; communicating with an external processing device; and recording time series data.

16. A method of monitoring a sealing device, the method comprising: providing an apparatus comprising an inlet connected to a seal activation pressurised fluid source, and an outlet connected to the sealing device; delivering pressurised fluid to a seal element of the sealing device to energise the sealing device; isolating the sealing device from the seal activation pressurised fluid source by a fluid barrier disposed between the inlet and the outlet of the apparatus; detecting a change in condition in a fluid chamber between the fluid barrier and the outlet, the change in condition indicative of a change in volume of the seal element of the sealing device.

17. The method according to claim 16, comprising exposing the fluid chamber to a pressurised fluid from the seal activation pressurised fluid source to put the apparatus in a charged condition, and isolating the sealing device from the seal activation pressurised fluid source after the fluid chamber has been charged.

18. The method according to claim 16, comprising detecting a change in condition in the fluid chamber until the fluid chamber reaches a depleted condition.

19. The method according to claim 16, comprising recharging the fluid chamber by exposing the fluid chamber to a pressurised fluid from the seal activation pressurised fluid source to put the apparatus in a recharged condition.

20. The method according to claim 19, comprising isolating the sealing device from the seal activation pressurised fluid source after the fluid chamber is recharged.

21. The method according to claim 20, comprising repeating the steps of detecting a change in condition in the fluid chamber until the fluid chamber reaches a depleted condition and recharging the fluid chamber.

22. A method of determining an operational life of a sealing device, the method comprising: monitoring a sealing device according to the method of claim 16; measuring one or more reference parameters while monitoring the sealing device; calculating a rate of change in volume of the seal element with respect to the one or more reference parameters; calculating from the rate of change a value of the one or more reference parameters at which a lower threshold volume of seal element is passed.

23. The method according to claim 22, wherein the one or more reference parameters comprises one or more reference parameters selected from the group comprising: time, pressure, heave, relative travel between the seal element of the sealing device and a surface on which the seal element makes a seal, and temperature.

24. A method of analysing seal wear characteristics, the method comprising: (a) monitoring a sealing device according to the method of claim 16; (b) measuring first and second reference parameters while monitoring the sealing device; (c) calculating a rate of change in volume of the seal element with respect to the first reference parameter; (d) calculating an average value of the second reference parameter; and (e) associating the calculated rate of change in volume with the calculation of the average value of the second reference parameter and recording the association in a database.

25. The method according to claim 24, comprising repeating steps (a) to (e) for one or more further sealing devices, and determining a correlation between a rate of change in volume of the seal element and the second reference parameter.

26. The method according to claim 25, comprising calculating from the correlation, for a given value of the second reference parameter, a value of the first reference parameter at which a lower threshold volume of seal element is passed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0081] There will now be described, by way of example only, various embodiments of the invention with reference to the drawings, of which:

[0082] FIGS. 1A and 1B are schematic representations of a sealing device monitoring system in accordance with a first embodiment of the invention, with an unworn sealing device and a worn sealing device respectively;

[0083] FIG. 2 is a schematic representation of a sealing device monitoring apparatus in accordance with a second embodiment of the invention;

[0084] FIG. 3 is a schematic representation of a sealing device monitoring apparatus in accordance with an alternative embodiment of the invention;

[0085] FIGS. 4A and 4B are schematic representations of a sealing device monitoring system incorporating the apparatus of FIG. 3, with an unworn sealing device and a worn sealing device respectively; and

[0086] FIG. 5 is a schematic representation of the sealing device monitoring apparatus of FIG. 3 in conjunction with a packer monitoring and control system.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0087] FIGS. 1A and 1B are schematic representations of a sealing device monitoring system in accordance with a first embodiment of the invention. The system is shown and described in the context of a packer for a telescopic slip joint for a marine drilling riser, but it is applicable to other sealing device systems across a range of industrial applications. These include systems in the pipeline, food processing and pharmaceutical industries.

[0088] Referring to FIG. 1A, the system 10 comprises a monitoring apparatus 10 and a sealing device in the form of a slip joint packer 32. The apparatus 11 comprises an inlet 12 connected to a seal activation fluid pressure source (not shown), which may be a hydraulic or pneumatic pressure source provided at the site (in this case the drilling rig), and an outlet 14 through which a pressurised fluid is delivered to the packer for actuation of the packer. In this case the packer is energised by inflation of the sealing element 36. Supply of the pressurised fluid is generally indicated by the arrows.

[0089] Located between the inlet 12 and the outlet 14 of the system 10 is a fluid barrier 17, which in this case is an electronically actuated solenoid valve. A fluid chamber 20 is located between the fluid barrier 17 and the outlet 14, and is isolated from the inlet by the fluid barrier 17, when the valve is closed. An optional bypass 22 to the fluid barrier connects the inlet to the fluid chamber 20, and comprises an inline valve 24 to control the function of the bypass. A sensor 30 is provided in the fluid chamber 20, and communicates with a control module 50. In this embodiment, the control module 50 also communicates with the valves 22 and 24 to control their operation.

[0090] FIG. 1A shows the system 10 with a substantially unworn seal element 36 in the packer 32. The valve 17 is initially opened (with the valve 24 closed) to provide fluid pressure to energise the seal element of the packer. The valve 17 is then closed to lock in fluid pressure in the fluid chamber 20 between the outlet 14 and the valve 17. The fluid pressure in the chamber is sufficient to maintain a seal between the packer 32 and the riser 40.

[0091] FIG. 1B shows the system 10 after a period of use, with a worn seal element 36 in the packer 32. Wear of the seal element has decreased the volume of the seal element by reducing its wall thickness. This increases the volume of pressurised fluid required to effectively energise the seal element. A sensor 30 is provided in the fluid chamber and monitors conditions in the fluid chamber that are indicative of a change in volume of the seal element of the packer. A signal is provided to the control module 50 from the sensor 30, and the measured data is used to determine a loss in volume and/or wear condition of the seal element 36. This determination may be by calculations performed by the control module itself, or may be by calculations performed by an external processing device such as a computer.

[0092] After a period of use, pressurised fluid is introduced into the fluid chamber from the seal activation pressurised fluid source to reinstate desired conditions in the fluid chamber. This may be achieved by opening the valve 17. The bypass 22 can be used to deliver pressurised fluid into the chamber 20 without opening the valve 17, or in the event that the valve 17 is unable to open. Continued monitoring of the conditions within the fluid chamber 20, including accounting for the introduction of pressurised fluid during a reinstatement of desired conditions, enable continued monitoring of the wear condition of the seal element. The wear condition of the seal element can be determined from the cumulative monitoring over several monitoring and reinstatement cycles.

[0093] In FIGS. 1A and 1B the system 10 is illustrated in schematic form, to permit the basis of its operation to be briefly illustrated and described. However, various embodiments of the inventive apparatus and system are possible, and exemplary embodiments will be described below with reference to FIGS. 2 to 5.

[0094] Referring to FIG. 2, there is shown generally at 110 a sealing device monitoring apparatus in accordance with a second embodiment of the invention. The monitoring apparatus 110 is configured to be connected to a sealing device (not shown) in the form of an inflatable slip joint packer, which seals against an outer wall of a marine riser that extends through the packer.

[0095] In this example, the packer is energised by inflation of the sealing element by hydraulic fluid. The apparatus 110 comprises an inlet 112 connected to a seal activation fluid pressure source (not shown), which is a hydraulic pressure source provided on a drilling rig, and an outlet 114 through which the pressurised fluid is delivered to the packer for actuation of the packer. Supply of the pressurised fluid is generally indicated by the arrows.

[0096] Located between the inlet 112 and the outlet 114 of the system 110 is a ram-type piston cylinder arrangement, shown generally at 116, comprising a piston element 117 on a piston rod 118, and operable to move within a piston chamber 119 defined within a cylinder 120. The piston element 117 provides a fluid seal in the piston chamber to define a lower piston chamber 119a and an upper piston chamber 119b, and can move in an axial direction with respect to the cylinder 120. FIG. 2 shows the piston 117 stroked towards an upper condition, with the piston chamber 119 of the cylinder 120 containing a relatively large volume of pressurised fluid below the piston element 117 in lower chamber 119a, compared with the volume in upper chamber 119b.

[0097] The piston arrangement 116 is provided with a linear transducer 130 internally within the piston cylinder, which is operable to measure the position of the piston element 117 in the piston cylinder, and therefore enable the volume of the lower piston chamber 119a to be determined by a simple calculation.

[0098] The apparatus comprises a pair of bypass lines 122a, 122b, located between the inlet 112 and the outlet 114, and arranged to bypass the piston element 117. Each bypass line is provided with a valve 124a, 124b, which is operable by a control module (not shown) to open and close. The default failsafe position of valves 124a, 124b is open. The two bypass lines 122a, 122b, and valves 124a, 124b, provide redundancy in the event that one of the lines and/or the valves becomes damaged or inoperative. A supply pressure transducer 113 is provided between the inlet 112 and the bypass lines 122a, 122b, to monitor the pressure of the pressurised fluid which enters the apparatus 110. The apparatus 110 also comprises a pressure regulator 126 located between the lower piston chamber 119a and the outlet 114, and an outlet pressure transducer 128 located between the regulator 126 and the packer (not shown) on the outlet side. The regulator 126 regulates pressure at the outlet of the apparatus and thus to the packer, preventing an excess of pressure (i.e. higher than the desired operating range) from being presented to the packer. The outlet pressure transducer 128 is located on the outlet side of the regulator, to measure the pressure supplied to the packer. A further transducer may be provided between the lower piston chamber 119a and the regulator 126 to monitor the pressure in the piston chamber.

[0099] The apparatus comprises a control module 150, which is in communication with the pressure transducers 113 and 128, the linear transducer 130, and the bypass valves 124a, 124b. The control module receives data signals from the respective transducers and controls the operation of the valves. Determination of a loss in volume and/or a wear condition of the seal element may be by calculations performed by the control module itself, or may be by calculations performed by an external processing device such as a computer, connected to the control module. In this embodiment, the control module has a human machine interface (HMI) (not shown).

[0100] To energise the packer, the pressurised fluid is delivered through the apparatus 110 from the inlet 112 to the outlet 114. With one or both of the bypass valves open, pressurised fluid enters the apparatus via the inlet 112 and through bypass line(s) to fill the apparatus.

[0101] The piston areas of the respective piston faces are such that there is an initial net force on the lower (piston chamber) side of the piston element, which raises the piston element in the chamber to an upper position, which increases the volume of the lower piston chamber 119a to a maximum. In this particular embodiment, the piston area of the lower side of the piston element is two times that of the upper side of the upper side. This particular ratio of piston areas has been selected to rapidly move (or return) the piston to its uppermost position when pressure is equalised; however, it will be appreciated that other ratios can be used.

[0102] The valves 124a and 124b are then closed to isolate the fluid outlet 114 and the lower piston chamber 119a from the source of pressurised fluid on the inlet side.

[0103] A consequence of the ratio of piston areas used is that the supply pressure (the pressure that is supplied to the apparatus) must be higher than the working pressure of the packer so that there is sufficient supply pressure to cause a net force on the piston element to initially raise the piston element at the start of the filling cycle.

[0104] After the piston element has been moved to its uppermost position, it is initially unable to move downward within the cylinder in the event of packer wear due to the excess pressure contained within the apparatus. Therefore, some of the initial pressurised fluid must be bled from the system to reduce the system pressure to a manageable working pressure. After bleeding of the system, the piston will be able to move as intended. The pressure removed from the system during this process can be treated as negligible, and/or dismissed from consequent calculations performed by the system. Alternatively, the calculations and/or recorded data might be adjusted to compensate for the pressurised fluid which is bled from the system at the start of the measurement.

[0105] The control module 150, via the respective transducers, monitors the condition of the system.

[0106] In operation, the sealing device experiences wear and the material of the sealing element reduces in thickness and volume. The reduction in volume of the seal element is compensated for by increased inflation of the seal element; in other words, the volume of fluid on the interior of the seal element increases to maintain the sealing element in sealing contact with the riser surface. The outlet of the apparatus 114 is isolated from the fluid supply from inlet 112, but the required volume of fluid is provided from the piston chamber, with a corresponding downward movement of the piston element 117 to decrease the volume of the fluid in the lower chamber 119a. The required fluid pressure for energising the sealing element is maintained throughout by the regulator 126. The linear transducer 130 measures the change in position of the piston element 117 over time, and by a simple calculation, the reduction in volume of the sealing element can be determined in the control module. The control module can record a time series of the seal element determined volume, to enable calculation of a seal wear rate.

[0107] When the linear transducer 130 detects that the piston element has reached a lower position in the cylinder (e.g. a set point before the chamber 120 is completely empty), the apparatus and lower piston chamber can be refilled by opening of a bypass valve 124a and/or 124b. The valves 124a and/or 124b are actuated to open by the control module 150. This moves the piston element 117 back to an upper position as described above. The bypass valve(s) is subsequently closed when the piston element reaches a set point upper position in the cylinder, fluid is once again bled to reduce pressure in the apparatus (if required) and the apparatus continues to monitor conditions in the fluid chamber; as the sealing device is used, a loss in volume is determined from movement of the piston element. This process can be repeated so that over an extended period of time, over a number of piston movement and refill cycles, the total volume reduction in the packer material can be determined.

[0108] As described above, the apparatus of the invention enables a wear rate to be calculated from the change in volume over time. Typically the sealing device manufacturer will specify a maximum volume reduction that is acceptable for reliable operation of the sealing device, and using the calculated wear rate, a prediction can be made of a remaining available operating time of the sealing device. This prediction can be used to plan drilling operations and/or schedule servicing and/or replacement of the sealing device. Alternatively, the system can be used to set a maximum volume reduction that is acceptable to the system operator, and using the calculated wear rate, a prediction can be made of a remaining available operating time of the sealing device to the set volume reduction.

[0109] There may be a number of periods during operation of the system in which data relating to the wear/volume loss of the seal element is not collected or is intentionally discarded from measurements and/or calculations. For example, during the refilling of the system or during the bleeding of the system. Losses which are experienced during these times are expected to be negligible and, in any case, these losses will be repeated during every refill cycle and may cancel one another out and/or may be predicted by the system in order to compensate for their occurrence. Measurements may also be adjusted to compensate for the real or expected losses.

[0110] Referring to FIGS. 3, 4A, and 4B, there is shown generally at 211 a sealing device monitoring system in accordance with an alternative embodiment of the invention. The system 211 comprises a monitoring apparatus 210 and a sealing device in the form of an inflatable slip joint packer 232, which seals against an outer wall of a marine riser 240 that extends through the packer. The apparatus 210 is similar to the apparatus 110, and will be understood from FIG. 2 and the accompanying description. Like features are given like reference numerals, incremented by 100 in FIGS. 3, 4A, and 4B, and are not described in detail for reasons of brevity. The apparatus 210 differs from the apparatus 110 in that the linear transducer 230 is external to the piston cylinder, in contrast with the internal linear transducer configuration shown in FIG. 2. The linear transducer 230 is provided on an external rod. Technically, both internal and external linear transducers function in exactly the same way. The apparatus 210 also differs in that it does not comprise a pressure regulator located between the lower piston chamber 219a and the outlet 214; however it will be appreciated that a regulator can be provided in the same manner as in FIG. 2. In addition, the outlet pressure transducer 228 is provided between the outlet 214 and the bypass lines 222a, 222b, to monitor the pressure in the piston chamber on the outlet side of the apparatus 210.

[0111] The system may also be provided with a sealing device sensor module 241, which is located at or near the sealing device and collects data relating to its operating conditions. The sensor module 241 monitors heave data or movement data for the slip joint, and optionally monitors the temperature of the sealing device and/or the ambient temperature at or near the sealing device. The data collected by the sensor module 241 may be correlated with the determined wear condition of the sealing device, and may facilitate predictive monitoring as will be described in more detail below.

[0112] The monitoring of the reduction in volume of the seal element can be correlated with data collected by the sensor module 241 to lead to improved operational planning as follows. The sensor module 241 comprises a linear transducer that is configured to measure the heave of the offshore installation, and thus the amount of relative axial movement between the packer element and the riser. This means that the wear rate, calculated as a function of time, can be associated with an average heave, or heave expressed as a total distance travelled, experience by the system. Data relating to the wear rate of the packer can be associated with the heave data, and by collecting data from a number of systems and/or a single system under a range of conditions, a picture can be built up of how the heave experienced by the system affects the wear rate. This information can be used to predict the operating lifespan of a sealing device for a given heave condition; this information can be used by the manufacturer or operator of a particular packer assembly to plan its drilling operations and/or maintenance schedule, regardless of whether that particular packer assembly is to be provided with the monitoring apparatus itself.

[0113] Alternatively, or in addition to the above-described correlation of heave data to wear rate, the apparatus can be used to calculate a wear rate of a sealing device as a function of heave, or of distance travelled by the seal with respect to the riser, rather than as a function of time. A time-based prediction may not be reliable, if there is a change in sea state, and a heave-based prediction may provide a more reliable indication of the operating lifetime of the seal element. By calculating the wear of the sealing element per metre of stroke between the sealing device and the riser, a prediction can be made of a remaining total stroke of the sealing device that can be experienced before the set volume reduction is reached. The actual heave can continuously be measured n expected sea state condition can be used to predict the remaining operating time available, or the actual heave can continuously be measured to update the prediction.

[0114] Although the apparatus is primarily concerned with measuring, recording and calculating changes in volume and/or pressure over time, it will be appreciated that additional parameters relating to the operating conditions of the sealing device may be measured and/or related to the wear condition in embodiments of the invention. For example, drilling mud parameters, such as fluid type, density, cuttings type and/or temperature may be detected by the sensor module 241 and related to the determined wear condition of the sealing device, which may facilitate predictive monitoring.

[0115] FIG. 5 shows the system 211 used in conjunction with a system, generally shown at 300, for monitoring and controlling packer activation in a riser slip joint. The system 300 is as described in the applicant's international patent publication number WO 2015/150800, the contents of which are incorporated by reference. The system 300 is connected to two packers in a slip joint packer assembly; a primary upper packer 232a and a secondary lower packer 232b (not shown). However, it will be appreciated that additional packers may be provided. For example, the system may be a three or a four packer system.

[0116] The system 300 monitors the pressure of the primary packer supply, and is capable of activating the secondary packer, for example if the primary packer is determined as having failed or is required to be deactivated. The system is also capable of activating both packers simultaneously, for example in the event of a rig divert mode being activated.

[0117] In the configuration of FIG. 5, the apparatus 210 is disposed between the system 300 and the primary upper packer 232a, with the inlet 212 of the apparatus connected to an outlet 302 of the system. The system 300 is also connected to the secondary lower packer 232b via outlet 204. As described above, a typical function of the system 300 is to activate the lower packer 232b when a failure of the upper packer is detected. However, used in conjunction with the apparatus 210, the system 300 can be configured to activate the lower packer when a maximum wear condition of the upper packer, as determined by the apparatus 210, is reached.

[0118] Although the configuration of FIG. 5 shows an apparatus 210 connected to the upper packer 232a, it will be appreciated that an apparatus may alternatively or additionally be connected to the lower packer, so that wear of the lower packer can be determined.

[0119] It will be appreciated that the apparatus 110 of FIG. 1 functions in substantially the same way as the apparatus 210, and can also be used in conjunction with a sensor module (not shown) and the packer monitoring and control system 300 as described herein.

[0120] Functional fail safes may be incorporated into the system, including those listed below.

[0121] The control module and/or an external processor may be programmed with a maximum wear rate of the sealing element, which is consistent with the extremes of seal element wear during use. If the apparatus determines that this seal wear rate is exceeded (i.e. a reduction in the volume of fluid exceeds that of the maximum wear rate), this is indicative of a fluid leak in the packer. An operator of the system can be alerted, and/or if the system is used in conjunction with a packer monitoring and control system (such as 300 described in FIG. 5), a secondary packer could be activated.

[0122] The control module and/or an external processor may be programmed with a maximum time required for refilling the piston cylinder. The time taken to refill the piston can be measured, and if the time is exceeded, this is indicative of a fluid leak in the packer. An operator of the system can be alerted, and/or if the system is used in conjunction with a packer monitoring and control system (such as 300 described in FIG. 5), a secondary packer could be activated.

[0123] The status of the transducers and/or valves can be monitored by the control module to ensure that they are functioning properly.

[0124] In the embodiments described above, the apparatus depends on a ratio of respective piston areas to move the piston to its initial position within the chamber. However, it will be appreciated that such movement of the piston may be controlled in additional and/or alternative ways. For example, the piston may be driven back to its uppermost position after reaching a lower position in the chamber. To achieve this, a hydraulic supply could be provided at the base of the cylinder and used to drive the piston back to its starting position.

[0125] Alternatively, a cylinder could be provided which has a capacity for holding a volume of pressurised fluid greater than the volume of the seal element (or which may be sufficient to fill the seal element a number of times over), such that only one cycle of piston movement is required, at a maximum. Hence, no refill cycle will be required in this configuration and the piston will not be required to return to the uppermost position after use. In addition, bleeding of the system will not be required. Preferably, a cylinder of this type would be made longer (as opposed to wider) to accommodate the additional volume capacity in order to retain linear resolution in measurements.

[0126] The apparatus and systems described above provides an apparatus, system and method of monitoring a sealing device. It facilitates effective maintenance, servicing, or replacement of the seal prior to its failure. The invention is described in the context of telescopic slip joint packers used in the offshore drilling industry, but has general application to a range of sealing systems in a range of industries. These include, but are not limited to, oilfield applications to stuffing boxes, “nodding donkey” well pumps, and overshot tools.

[0127] Variations to the above-described embodiments are within the scope of the invention as defined herein. For example, although the embodiments of FIGS. 2 to 5 rely on the principle of measuring a change in volume while maintaining a fluid pressure, the invention is not limited to this principle. For example, in an alternative configuration, the fluid chamber has a fixed volume, and a loss in volume of the packer element is measured as a reduction in pressure in the chamber. Optionally in conjunction with other parameters such as temperature, the change in pressure can be used to determine a reduction in volume due to a wear condition, and the chamber can be refilled to allow continued monitoring over a number of pressure reduction and refill cycles. Pressure reductions due to wear can be distinguished from those due to a leak by virtue of their rate, and the time taken to refill the chamber.