WO2018142102A1

WO2018142102A1 - System and method for monitoring a flange joint assembly

Info

Publication number: WO2018142102A1
Application number: PCT/GB2018/050108
Authority: WO
Inventors: Graham Barker; Owen John Lloyd JONES; Clive Antony Marchant; Francis O'DOHERTY; Carl Robert TIPTON; Victoria WHITTLE
Original assignee: Johnson Matthey Public Limited Company
Priority date: 2017-02-01
Filing date: 2018-01-16
Publication date: 2018-08-09
Also published as: GB2560612A; GB201800677D0; GB201701675D0

Abstract

System and method for monitoring a flange joint assembly A system for monitoring a flange joint assemblyis disclosed. The system comprisesa sensor sheet for positioning between adjacent load bearing surfaces in the flange joint assembly. The sensor sheet comprises a plurality of sensors printed on a substrate.

Description

System and method for monitoring a flange joint assembly Field of the Invention

The present invention relates to a system for monitoring a flange joint assembly, a flange joint assembly comprising such a system, a method of installing such a system on a flange joint assembly and a method of monitoring a flange joint assembly. The present invention also relates to a method of installing a gasket or washer on a flange joint assembly and a method of installing a flange joint assembly. Background

Flange joint assemblies are commonly used on industrial plants for connecting pipework, vessels and other fluid transfer components. The two items to be connected are each provided with a flange, which is typically an annular plate surrounding an opening into the item. The two flanges are placed against one another with a gasket in between them to provide a seal. The two flanges are then secured together using fasteners, typically bolts passing through the flanges, so as to compress the gasket and form a fluid-tight seal. Common types of flange joint assemblies include floating type flange joints and metal to metal contact flange joints.

The force applied by the fasteners to hold the flanges together is referred to as the clamping force. The clamping force applies across various load bearing surfaces in the flange joint assembly. For example, the faces of the flanges, which are pressed against each other with the gasket between them, are load bearing surfaces across which the clamping force applies. Similarly, the surfaces of the fasteners, such as the surfaces of bolts and washers and the surfaces of the reverse sides of the flanges against which those bolts and/or washers press are load bearing surfaces in the flange joint assembly. The clamping force applies across those surfaces so as to transfer the clamping force to the flanges from the fasteners. During a typical installation of a flange joint assembly a gasket is inserted between the flanges and the fasteners are tightened until a desired torque is reached. The torque may be measured using, for example, a torque wrench. The selection of gasket, the torque applied and any record keeping is dependent on the actions of the operator and is therefore difficult to monitor.

Once the flange joint assembly is installed it may be

inspected from-time-to-time to ensure that it is functioning correctly. The inspections may involve a tightening of fasteners if the joint slackens over time. The purpose of the inspections is often to detect any leaks that are occurring so as to avoid costly and damaging spills to the environment. Performing the inspections can be time-consuming and the quality of the inspection and record keeping is again

dependent on the actions of the operator.

Attempts have been made to automate the monitoring of the flange joint assemblies in order to detect leaks occurring and provide an alarm. US5793150 discloses including sensor chips in gaskets to detect pressure or leakage. US7316154 discloses a system where there are two sealing surfaces and a leak in one of them is detected before the second one leaks. In effect, the second surface acts as a back-up that keeps the seal intact when the first surface fails, with the sensor providing an alert of what has happened so that the seal can be replaced. US7009409 discloses the use of capacitance measurement for gasket integrity and gasket compression monitoring. EP2138744 discloses comparing a signal from a sensor in a polymer seal to historical performance data or thresholds in order to predict the lifetime of the seal. US8061211 discloses using the changing conductivity or capacitance of a seal to measure pressure. DE102004025135, DE4101871, US20080073054 , US20060220498 and GB2317701 also disclose sensors in gaskets. The prior art systems have not been widely adopted however and there is still a need for improved monitoring systems. Because of the large number of flange joint assemblies in a typical industrial plant, any automated sensor needs to be manufactured cheaply to prevent cost becoming prohibitive. However, the sensor must not reduce the integrity of the flange joint assembly. The need for a cheap sensor that retains the high level of integrity of the flange joint assembly is as yet unfulfilled.

A common failure mode of flange joints is insufficient clamping force across the gasket face. Leaks due to such failures may be detected using inspections as described above. However, another important failure mode is the use of an incorrect part, such as an incorrect gasket, which therefore fails prematurely. Such failures are typically due to operator error and it would be advantageous to reduce or eliminate such failures.

Preferred embodiments of the present invention seek to ameliorate one or more of the above problems of the prior art. In particular, preferred embodiments of the present invention seek to provide improved systems for monitoring a flange joint assembly. Summary of Invention

According to a first aspect of the invention, there is provided a system for monitoring a flange joint assembly, the system comprising a sensor sheet for positioning between adjacent load bearing surfaces in the flange joint assembly, wherein the sensor sheet comprises a plurality of sensors printed on a substrate. Preferably the sensor sheet comprises a first communications interface, wherein the first

communications interface is printed on the substrate and wherein the sensors are connected to the first communications interface by conductors printed on the substrate.

The printing of components such as sensors, conductors and communications interfaces onto substrates is possible in a high-volume, cost-effective manner. The sensor sheets can thus be produced in sufficient numbers and at low enough cost to be a practical option for installation on the large numbers of flange joint assemblies in a typical plant.

Because the sensor sheets are produced at low cost, they can be replaceable, single-use components and durability for re- use is therefore not an issue. By printing a communications interface onto the sheet, the sensors can be read remotely by another device that communicates with the communications interface. That device can be re-used, since it is not inserted into a part of the flange joint assembly critical for the sealing performance. The costlier parts of a

monitoring system, such as processors, memory, power supplies or longer range communications systems can therefore be contained in a re-usable device that interfaces with the low- cost printed sensor sheet. It may be that the first communications interface comprises a plurality of electrical contacts printed on the substrate. Such a communications interface, which could interface, for example, with a socket on or attached to another device, may provide a reliable, low-cost communication interface. It may be that the first communications interface is a wireless communications interface, preferably a short-range wireless communication interface. Short-range wireless communications include systems such as ANT+, Bluetooth, ISAlOOa, Infrared, ISM band, NFC, RFID, 6L0WPAN, ZigBee and Z-Wave and typically have a range of from around 10 cm to around 5 m. Short-range wireless communications may be particularly advantageous in permitting faster connection and disconnection (since no physical connection is required to make the connection) and in enabling multiple sensor sheets to connect to a single device. Short-range wireless communications that can also transfer power, such as NFC for example, are particularly advantageous since they have the advantages of wireless communications whilst also avoiding the cost of having a power supply on the sensor sheet. Thus the first

communications interface is preferably an unpowered

communications interface, more preferably an unpowered wireless communications interface and most preferably an unpowered short-range wireless communications interface. The sensor sheet preferably does not comprise a power supply. NFC, which may be as set out in standards Ecma-340 and

ISO/IEC 18092, uses magnetic field induction to communicate and transit power over short distances.

Preferably the sensors comprise at least one pressure sensor and at least one temperature sensor. By providing a pressure sensor on the sheet, which is located between load bearing surfaces in the flange joint assembly, the clamping force on the flange joint assembly can be monitored. Loss of clamping force, for example due to slackening of fasteners or loss of elasticity of gaskets, is a significant cause of gasket failures. The temperature sensor may be important so as to allow compensation for the effects of temperature on the pressure sensor. Preferably, the sensors comprise at least three pressure sensors and at least one temperature sensor. Providing three or more pressure sensors allows the

distribution of the clamping force across the flange joint assembly to be monitored and thus allows the detection and identification of faults such as the slackening of a single fastener. It will be appreciated that a leakage can occur if one part of the flange joint assembly is not subject to sufficient clamping force and monitoring the distribution of the clamping force across the flange joint assembly using three or more pressure sensors may be particularly

advantageous. It may be that a single temperature sensor is sufficient to compensate for temperature effects in all the pressure sensors since the temperature may be relatively constant across the flange joint assembly or at least across the sensor sheet. Providing a single temperature sensor may advantageously reduce the cost of the sensor sheet. It may be that the sensor sheet is comprised in a gasket. Thus, according to the invention, there may be provided a gasket comprising a sensor sheet as described in relation to the first aspect of the invention. The substrate may, for example, be a gasket material such as a fibrous gasket material. In some embodiments, the sensor sheet may comprise an opening and opposing surfaces of the sensor sheet

surrounding the opening may be at least partially covered by a gasket material folded around the sensor sheet and passing through the opening. Providing the sensor sheet as a gasket or as part of a gasket may allow measurements, for example pressure measurements, to be taken between the flange faces. Such measurements may be particularly useful in predicting future failures. By providing a sensor sheet comprising an opening wherein opposing surfaces of the sensor sheet

surrounding the opening are at least partially covered by a gasket material folded around the sensor sheet and passing through the opening, the sensor sheet may be separated from the process fluid flowing through the flange joint assembly. The opening in the sensor sheet is sized and shaped so as to exceed the internal diameter of the flow passage through the flange joint assembly and the gasket material protects the inner edge of the sensor sheet surrounding the opening from the fluid. Thus the substrate of the sensor sheet can be selected to be advantageous for the printing of the sensor sheet and the gasket material can be selected so as to be advantageous for sealing the flange joint assembly and the two materials can each perform their respective roles. The advantage of a low-cost printed sensor sheet can thus still be combined with advanced gasket materials for sealing flange joint assemblies handling even aggressive process fluids.

It may be preferable that the sensor sheet is comprised in a washer. Thus, according to the invention, there may be a provided a washer comprising a sensor sheet as described in relation to the first aspect of the invention. The sensor sheet may be comprised in a washer having a single opening for use with a single fastener but preferably the sensor sheet comprises multiple openings whereby fasteners such as bolts can be inserted through the sensor sheet. Thus a single sensor sheet may be provided that comprises openings for each of the fasteners on the flange joint assembly so that one sensor sheet is used per flange joint assembly. The sensor sheet may be generally c-shaped, or generally ring-shaped with a split at one point of the ring to allow the sensor sheet, which is preferably flexible, to be put into place around a pipe that the flange joint assembly is on. It will be understood that a generally c-shaped or generally ring- shaped sensor sheet may comprise one or more protruding tabs to accommodate the first communications interface. The fasteners are preferably bolts. Where the sensor sheet is a washer or part of a washer it may be preferable to provide at least one fishplate having at least two openings through which the fasteners, preferably bolts, on the flange joint assembly pass, the fishplate spanning two or more of the fasteners so that at least part of the sensor sheet comprising one or more pressure sensors is between the fishplate and a flange. Thus the load bearing surfaces are the fishplate and the flange. Providing such a fishplate may advantageously reduce twisting of the sensor sheet as fasteners such as bolts are tightened. Such a fishplate may be particularly advantageous where the sensor sheet comprises multiple openings whereby fasteners can be inserted through the sensor sheet and especially advantageous where a single sensor sheet is provided that comprises openings for each of the fasteners on the flange joint assembly so that one sensor sheet is used per flange joint assembly. The fishplate is preferably an open shape, such as an arc or an arced or straight-edged c- or u-shape. Such a shape means the fishplate fits into place around the pipe and spanning the fasteners in a way that would not be possible with a closed circular-ring or closed square-ring. The fishplate is preferably formed from a rigid material, such as steel .

Providing the sensor sheet as a washer, or as part of a washer, is advantageous in that washers are typically

positioned on the outside of the flange joint assembly, away from the sealing surfaces. There is thus no need for the sensor sheet to be compatible with the process fluid, or for the sensor sheet to form part of any seal. The load bearing surfaces of the fasteners, or for example fishplates, and the parts of the flange joint assembly against which they press will be under the same loads as the contacting flange faces since that is how the load is passed from the fasteners to the flanges. Thus the sensor sheets can still monitor the clamping force on the flange joint assembly, without them forming part of a seal. The data from the sensors can be monitored to detect any reduction in the clamping force and thus to predict failure of the flange joint assembly.

Preferably the sensor sheet comprises a pressure sensor around each of the openings. In that way the clamping force being applied by each of the fasteners can be monitored. That may have significant advantages in that it may allow the monitoring to identify that a particular fastener is

responsible for a loss of clamping force and warn that the fastener should be tightened in order to prevent more serious failure. The sensor sheet can also be used to monitor the individual fasteners as the flange joint assembly is

installed and to provide feedback during the tightening of the fasteners and an automated record of the correct

tightening . The substrate is preferably a flexible substrate. A flexible substrate may conform better to the geometry of the flange joint assembly and may be more easily installed. Suitable substrates include plastics, preferably high temperature plastics. Examples of suitable substrates include acetate and PTFE.

As discussed above, an advantage of providing a low-cost printed sensor sheet with a printed first communications interface is that the costlier parts of a monitoring system can be provided in a separate device that can be used for a longer period of time with only the sensor sheet being replaced as required. Thus the system preferably further comprises an electronics module, the electronics module comprising a housing separate from the sensor sheet, the housing containing a processor and a communication module, wherein the electronics module comprises a second

communications interface configured to reversibly connect to the first communications interface, and wherein the processor is configured to process data received from the sensors via the first and second communications interfaces and to

transmit the processed data via the communication module. The processor may process the data for example to turn raw conductivity data from the sensors into pressure or

temperature data. The processor may process the data for example to adjust data from a pressure sensor using data from a temperature sensor to compensate for temperature effects of the pressure sensor. The processor may process the data for example to add a time stamp to the data. The processor may process the data for example to transform it into a form suitable for communication via the wireless communication module. The communication module is preferably a wireless communication module. For example, the wireless communication module is preferably a WirelessHART module. Many industrial plants will include a WirelessHART network and it is

advantageous to transmit the data over that network. The electronics module thus serves to monitor data from the sensors, and communicate that data over longer ranges, for example to a plant control room or to an internet-connected device that uploads the information to a cloud location from which it can be accessed on any internet connected device. The electronics module may upload the data directly to the cloud location. The electronics module is not replaced each time the sensor sheet is replaced and the electronics module can therefore include costlier components, such as a

processor, memory, and/or longer range communications.

Preferably the electronics module comprises a power supply, which is preferably able to supply power to both the

electronics module and the sensor sheet. The power supply is preferably a battery, which advantageously removes the need for any wired connection of the electronics module to the rest of the plant and thus simplifies installation. The power is preferably supplied to the sensor sheet via the first and second communications interfaces. That may be advantageous during installation as only one connection may need to be made between the sensor sheet and the electronics module. Thus the electronics module preferably comprises a battery to power the electronics module, wherein power from the battery can be supplied to the sensors via the first and second communications interfaces. The electronics module is

preferably a purpose-built module. The electronics module is not a general purpose desktop computer. Preferably the first and second communications interface are short-range wireless communication interfaces. That may simplify installation as the first and second communications interfaces may be connected without needing to make any physical connection. The connection in such a case may be made by positioning the first and second communication interfaces in the vicinity of each other and initiating a wireless connection, for example using the processor in the housing. A particularly preferable form of short-range wireless communication may by NFC. In that way power can be provided to the sensor sheet via the first and second

communications interfaces. For example, the first

communications interface may be an NFC target and the second communications interface may be an NFC initiator. Such communication may be referred to as passive NFC, where the initiator has a power supply and the first target does not have a power supply.

In some embodiments the first and second communications interfaces may involve a physical connection. For example, the first communications interface may comprise a plurality of electrical contacts printed on the substrate and the second communications interface may comprise a socket

configured to mate with the electrical contacts. The socket may be mounted on or in the housing of the electronics module or the socket may be connected to the housing of the

electronic module by a wired connection. Comprising the sensor sheet in a washer may be particularly advantageous as the sensor sheet does not form part of the sealing surface of the joint and is not inserted between any elements of the sealing surface, such as the flanges. Thus there is less risk of the sensor sheet contributing to a sealing failure and more design options available for the sensor sheet. Thus, according to a broad aspect of the invention, there may be provided a flange joint assembly comprising two flanges having flange faces that press against one another when a clamping force is applied, wherein the clamping force is applied by a plurality of fasteners, the plurality of fasteners pressing against the flanges to exert the clamping force on the flanges and a sensor sheet

comprising at least one pressure sensor is preferably located between one of the flanges and at least one of the fasteners so as to be compressed between the fastener and the flange. The fasteners are preferably nuts and bolts. There may be further washers or fishplates between the fasteners and the flange. The sensor sheet is preferably a sensor sheet as described above. Data from the at least one pressure sensor is preferably monitored to predict failure of, or detect problems with, the flange joint assembly. The data, or trends in the data, may be compared to historical data from the or other flange joint assemblies in order to predict future failures or detect problems.

According to a second aspect of the invention, there is a provided a flange joint assembly comprising a system

according to the invention for monitoring the flange joint assembly. The system may for example be as described in relation to the first aspect of the invention. Most preferably, the electronics module is multiple-use, while the sensor sheet is a replaceable, single-use item. The electronics module may thus be thought of as associated with the flange joint assembly to create a 'smart' flange joint assembly and the sensor sheet as a consumable item used by the 'smart' flange joint assembly. The housing of the

electronics module is preferably mounted on the flange joint assembly .

In a particularly preferable arrangement the first

communications interface is located on a tab of the sensor sheet. The tab preferably protrudes from the flange joint assembly. Thus the sensors on the sensor sheet may be

positioned between load bearing surfaces in the flange joint assembly and the tab may protrude from between the load bearing surfaces. In that way the first communications interface is accessible for connection to the second

communications interface. Preferably the housing is mounted on the flange joint assembly so as to cover the part, for example the tab, of the sensor sheet on which the first communications interface is located. The second

communications interface may be positioned on or in the housing so that, when the housing covers the part, for example the tab, of the sensor sheet on which the first communications interface is located a connection between the first and second communications interfaces can be made. For example, the housing may comprise a recess into which the tab fits. A socket for forming a physical connection between the first and second communications interfaces may be in the recess. The housing may comprise a port into which the tab inserts to form the connection between the first and second communications interfaces. If the first communications interface is a wireless communications interface, the second communications interface may be positioned on or in the housing so that, when the housing covers the tab, a wireless connection between the first and second communications interfaces can be made.

In some embodiments multiple sensor sheets may interface with a single electronics module. For example, a separate sensor sheet may be provided for each fastener, with each of the sensor sheets communicating, preferably wirelessly, with a common electronics module. Where flange joint assemblies are located close together, the first communications interface on a sensor sheet in a second flange joint assembly may

communicate with the second communications interface of the electronics module of the first flange joint assembly. Such arrangements could be considered, for example, where a piece of equipment such as a valve or gauge has two flange joint assemblies, for example inlet and outlet, in close proximity, such as on either end of the piece of equipment. According to a third aspect of the invention there is

provided a method of monitoring a flange joint assembly comprising providing a system of the invention, for example as described in relation to the first aspect, and monitoring data from the sensors over time. Preferably the method involves predicting future leakage by monitoring a clamping force on the flange joint assembly over time.

Preferably the processor in the electronics module transmits data from the sensors via the wireless communication module. Preferably the data from the sensors is processed by the processor, for example to add a time stamp, to compensate for temperature effects, to compute pressure or temperature data from raw data, or to convert the data into a form suitable for transmission. Thus the processor preferably processes data received from the sensors and transmits the processed data via the wireless communication module. The transmission may be to a control room or a cloud location, either directly or via a network, such as a mesh network. For example, the transmission may occur over the plant's WirelessHART network. The data may be monitored for indicators of actual or

imminent failure by the processor in order, for example, to provide an alarm signal. However, the data is preferably monitored centrally, for example on servers connected to the internet. The data may be monitored for example by comparing pressure readings to expected pressure readings so as to detect loss of clamping force. Data from sensors spaced across the flange joint assembly, for example spaced across the flange faces, or associated with individual fasteners, may be analysed to detect uneven clamping forces. That may be particularly advantageous in that a single detection of overall clamping force may fail to predict a leakage path that results from loss of local clamping force in one region of the seal. Data may be compared with historical data from the sensors, or from other sensors mounted on the or other flange joint assemblies, in order to predict future leakages of the flange joint assembly. For example, long term trends in the sensor readings may be compared with equivalent trends in other flange joint assemblies with known failure times in order to predict when the present flange joint assembly might fail. By transmitting the data to a central, preferably cloud location, advantage can be taken of the quantity of data available from many sensors on many flange joint assemblies, potentially on many different plants, to identify trends and carry out comparisons with similar joints. Thus while a particular flange joint assembly may have never failed before, across a large number of plants over an extended period of history there may be a number of similar flange joint assemblies that have experienced a variety of failures. By gathering data from many different flange joint assemblies into a cloud location for analysis, those similarities may be exploited to predict failures.

Preferably the processor compares the data from the sensors to previous data from the sensors and transmits the data via the wireless communication module if the data is different from the previous data. The previous data is preferably the most recently transmitted data. Transmitting the data may be a relatively power-consuming activity and it is thus

advantageous to only transmit data when something has

changed. The processor preferably applies an algorithm to determine whether or not there has been a significant change in the data since the most recently transmitted data. In that way, data which varies only within the normal precision of the sensor, is not unnecessarily transmitted. For example, the algorithm may check whether the data has changed by more than a pre-determined threshold, which may be an absolute threshold or a relative, for example a percentage change, threshold .

According to a fourth aspect of the invention, there is provided a method of monitoring a flange joint assembly comprising: a. providing a first sensor sheet, wherein the first sensor sheet comprises a plurality of sensors printed on a substrate and a first communications interface, wherein the first communications interface is printed on the substrate and wherein the sensors are connected to the first communications interface by conductors printed on the substrate; b. providing an electronics module, the electronics module comprising a housing separate from the sensor sheet, the housing containing a processor and a wireless

communication module, wherein the electronics module comprises a second communications interface, and wherein the processor is configured to process data received from the sensors via the first and second communications interfaces and to transmit the processed data via the wireless communication module; c. positioning the first sensor sheet between adjacent load bearing surfaces in the flange joint assembly; d. mounting the electronics module on the flange joint

assembly and connecting the first communications

interface to the second communications interface; e. monitoring data from the sensors on the first sensor

sheet over time; f . disconnecting the first communications interface from the second communications interface; g. removing the first sensor sheet; h. providing a second sensor sheet, wherein the second sensor sheet comprises a plurality of second sensors printed on a second substrate and a second first

communications interface, wherein the second first communications interface is printed on the second substrate and wherein the second sensors are connected to the second first communications interface by second conductors printed on the second substrate; i. positioning the second sensor sheet between adjacent

load bearing surfaces in the flange joint assembly; j . connecting the second first communications interface to the second communications interface; and k. monitoring data from the second sensors on the second sensor sheet over time. Preferably the steps f to k are performed when the data from the sensors on the first sensor sheet monitored in step e indicate that failure of the flange joint assembly is

imminent. As discussed above, it is an advantage of the present invention that the costlier components of the system are comprised in an electronics module that is separate from the sensor sheet and reversibly connectable to the sensor sheet via the communications interfaces. The same electronics module can therefore be used repeatedly while the sensor sheet is changed each time the flange joint assembly is opened in accordance with typical practices for changing gaskets or washers. Changing the sensor sheet each time ensures that risks to joint integrity from re-used sensor sheets is avoided. Depending on how the electronics module is mounted on the flange joint assembly it may be possible to remove the sensor sheet and install the second sensor sheet (steps f to ) without dismounting the electronics module from the flange joint assembly. However, it may be necessary, for example if the housing is arranged to cover a part of the sensor sheet as discussed above, to remove the electronics module in or prior to step f and to remount it in step j .

According to a fifth aspect of the invention, there is provided a method of installing a gasket or washer on a flange joint assembly, wherein the method comprises: providing a wireless identifier on each of (a) the gasket or washer and (b) the flange joint assembly, the wireless identifiers storing data related to the compatibility of the gasket or washer with the flange joint assembly; providing a device configured to interface with the wireless identifier, the device comprising a processor configured to analyse data read from the wireless identifiers by the device ; reading the wireless identifiers with the device; analysing the data read from the wireless identifiers using the processor to determine that the gasket or washer is compatible with the flange joint; and installing the gasket or washer on the flange joint assembly.

Preferably the gasket or the washer are as described

elsewhere in this specification according to the invention. Preferably the wireless identifier is printed on the

substrate. In a particularly preferably embodiment, the wireless identifier on the gasket or washer is comprised in the first communications interface on the sensor sheet. Thus the device may read the first communications interface of the sensor sheet and read the wireless identifier on the flange joint assembly and the processor may analyse the data read from the first communications interface and from the wireless identifier to confirm that the gasket or washer is compatible with the flange.

The wireless identifier may be, for example, a bar code or QR code. The wireless identifier may be a short-range wireless communication interface, such as described above. The short- range wireless communication interface may for example be an NFC tag. By providing such wireless identifiers on the gasket or washer and on the flange joint assembly, an operator with a portable device, which might for example be a smartphone running an app, can scan the wireless identifiers with the device and the device can compare the data read from the wireless identifiers to check the compatibility of the gasket or washer with the flange. The device preferably comprises a reader to read the data from the wireless identifier. For example, the reader may be a barcode scanner or an NFC initiator. The device may comprise memory for storing data about the compatibility of various gaskets or washers with various flange joint assemblies and the processor may use that data when determining the compatibility. Advantageously, the device is able to access the internet and further data about the compatibility is stored in an internet, or cloud, location. Thus the data related to the compatibility read from the wireless identifier on the flange joint assembly may be data identifying the flange joint assembly and the data related to the compatibility read from the wireless

identifier on the gasket or washer may be data identifying the gasket or washer, such as data identifying the type of gasket or washer, and the device may analyse that information using the processor by transmitting that information to an application running at a remote location, for example on a server such as in the cloud, which compares the flange joint assembly with the gasket or washer and determines

compatibility and communicates that determination to the device. In that way, the identifiers on the flange joint assembly do not need updating, for example, each time a new gasket type is launched that is compatible with that flange joint assembly. Instead, the application can be updated to include the information that the new gasket type is

compatible with the existing flange joint assembly. The data identifying the flange joint assembly and the data

identifying the gasket or washer may uniquely identify the particular flange joint assembly or gasket or washer or may more generally identify the type of flange joint assembly or gasket or washer.

Preferably the device also records the information from the wireless identifiers on the gasket or washer and on the flange joint assembly, thus creating a reliable, automatic record of the type of gasket or washer installed and the date of installation. The record may be created on, or

communicated to, an application, such as a cloud application, running on remote servers. In that way a reliable maintenance record that can be accessed via the internet is created. For record keeping, it is preferable that the data identifying the flange joint assembly uniquely identifies the particular flange joint assembly.

According to a sixth aspect of the invention, there may be provided a method of installing a system according to the first aspect of the invention on a flange joint assembly, wherein the method comprises: providing a wireless identifier on each of (a) the sensor sheet and (b) the flange joint assembly, the wireless

identifier storing data related to the compatibility of the sensor sheet with the flange joint assembly; providing a device configured to interface with the wireless identifiers, the device comprising a processor configured to analyse data read from the wireless identifiers by the device ; reading the wireless identifiers with the device; analysing the data read from the wireless identifiers using the processor to determine that the sensor sheet is

compatible with the flange joint assembly; and installing the sensor sheet on the flange joint assembly. The wireless identifiers may, for example, be bar codes or QR codes. Preferably the wireless identifiers are short-range wireless communications interfaces. Preferably the short- range wireless communication interface on the sensor sheet is comprised in the first communications interface. Thus there is no possibility for operator error in trying to scan the wrong interface. It will be appreciated that features

described in relation to the fifth aspect of the invention, particularly with regards to the operation of the device and the checking of compatibility and keeping of records may be applied equally to the sixth aspect of the invention, with the gasket or washer being replaced by the sensor sheet as appropriate and, for brevity, are not repeated again here.

According to a seventh aspect of the invention there is provided a method of installing a flange joint assembly, comprising providing a system according to the first aspect of the invention, positioning the sensor sheet between adjacent load bearing surfaces in the flange joint assembly, tightening fasteners on the flange joint assembly, monitoring data from the sensors while the fasteners are tightened and providing a signal when the fasteners are correctly

tightened. For example, the signal may be provided when data from the sensors indicates that the clamping force exerted by a fastener has reached a predetermined force.

The fasteners are preferably bolts, which preferably engage with nuts.

It may be that the system includes the electronics module and the housing is mounted on the flange joint assembly and the electronics module comprises memory contained in the housing configured to store information identifying the correct tightness of the fasteners.

Preferably the signal is provided on a portable device. The portable device may link directly with the first

communications interface or may communicate with the

electronics module, preferably via the wireless communication module. The portable device may for example be a smartphone running an app . The portable device may display data from the sensors in real time so that an operator can view the

progress of tightening the fasteners. The data from the sensors is not necessarily raw data and is preferably data that has been processed to show clamping force or pressure. The portable device preferably also provides instructions to the operator. For example, the portable device may display a user interface that includes data on individual fasteners and instructs the operator which fastener to tighten, wherein the device monitors the tightening of that fastener and instructs the operator when to stop tightening the fastener. For example, the device may monitor the clamping force applied by a fastener, for example by measuring a pressure exerted on a pressure sensor by the fastener, and instruct the operator to stop tightening the fastener when a predetermined force or pressure is reached. The portable device may repeat that process for other fasteners or for the same fastener. For example, it is usually recommended to tighten fasteners little-by-little in a particular pattern, but to achieve that manually is time consuming. The portable device may indicate on the user interface which fastener to tighten next and indicate when to move to the next fastener, which may improve compliance with recommended tightening schemes. In order to provide that information, the portable device preferably comprises a processor that receives data from the sensors and processes the data to determine the clamping force exerted by each individual fastener. If the processor in the electronics module has already processed the data from the sensors into data on the clamping force exerted by each individual

fastener, the processor on the portable device may determine the clamping force by using that data from the sensors as processed by the electronics module. Calculating the force exerted by each individual fastener might be achieved for example by having the sensor sheet in the form of a washer with a pressure sensor for each fastener, or by analysing data from pressure sensors across the flange joint assembly to determine the forces from the individual fasteners. The portable device may also receive data to identify the flange joint assembly, for example from a short-range wireless communication interface on the flange joint assembly or from the electronics module, preferably via the wireless

communication module. The data may directly identify the desired tightening scheme, the portable device may include memory containing data on the desired tightening scheme or, preferably, the portable device may send the data to an application running on a remote server, for example in the cloud, to determine the desired tightening scheme. The processor may receive the desired tightening scheme and display a user interface on a screen on the portable device, the user interface identifying individual fasteners and indicating the order in which the fasteners should be

tightened. For example, the next fastener to be tightened may be highlighted in a particular colour. The processor may then monitor the data from the sensors to monitor the tightness of the fastener being tightened and to indicate, for example by highlighting the fastener in a different colour, that the fastener is now sufficiently tightened for that step of the tightening scheme. The processer may then indicate on the user interface another fastener to be tightened and so on. The processor can store data related to the tightening, for example the variations in fastener tightness over time, for future use. The device may include memory for storing the data. Such future use might advantageously include audit or prevention of other failures if the flange joint assembly subsequently fails prematurely. The data may, for example, be stored by transmitting the data to an application or storage running on remote servers, for example in the cloud. Having such records automatically stored in an accessible location is a significant advantage over present systems, which often rely on simple paper records that record in general terms that an action has been taken, or even produce no records at all.

It will be appreciated that features described in relation to one aspect of the invention may be equally applicable in another aspect of the invention. For example, features described in relation to the systems of the invention, may be equally applicable to the methods of the invention, and vice versa. Some features may not be applicable to, and may be excluded from, particular aspects of the invention.

Description of the Drawings Embodiments of the present invention will now be described, by way of example, and not in any limitative sense, with reference to the accompanying drawings, of which:

Figure 1 is a diagram of a system comprising a sensor sheet according to the invention; Figure 2 is a diagram of another system comprising a sensor sheet according to the invention; Figure 3 is a schematic view of a flange joint assembly comprising a system comprising sensor sheets according to the invention;

Figure 4 is an exploded perspective view of a system

comprising a sensor sheet according to the invention on a flange joint assembly;

Figure 5 is a view of a gasket according to the invention;

Figure 6 is a schematic cross-sectional view of the gasket of figure 5 installed in a flange joint assembly; Figure 7 is a view of a washer according to the invention installed on a flange joint assembly;

Figure 8 is a cross sectional view of a system according to the invention installed on a flange joint assembly;

Figure 9 is a schematic representation of a method of

installing a gasket according to the invention;

Figure 10 is a schematic representation of a method of installing a flange joint assembly according to the

invention; and

Figure 11 is a user interface for use in the method of figure 10.

Detailed Description

In figure 1 a sensor sheet 1 is formed from an acetate substrate 4, on which is printed pressure sensors 2 and a temperature sensor 3. The sensor sheet 1 is sized so as to fit on a flange with openings 6 through which fasteners in the form of flange bolts can pass. A tab 7 protrudes from the sensor sheet 1 so as to extend beyond the flange. A first communication interface 8 in the form of multiple electrical contacts printed on the substrate 4 is on the tab 7. The first communication interface 8 is connected to the pressure sensors 2 and the temperature sensor 3 by conductors 9. The conductors 9 may be printed by printing, for example screen or inkjet printing, conducting material, such as silver or copper, onto the substrate 4. The pressure sensors 2 are for example printed graphene sensors, whose conductivity changes with pressure. Since the conductivity also varies with temperature, data from the temperature sensor 3, which may be a printed resistance temperature detector (RTD) , is used to correct the data from the pressure sensors 2 for temperature effects. Data from the pressure sensors 2 and the temperature sensor 3 can be read by connecting a device to the first communication interface 8. In use, data from the pressure sensors 2 is used to measure the clamping force across the surface of the flange. If the clamping force reduces, or becomes uneven across the flange, it may indicate an

increased risk of failure. Comparison with historical data from the or other flange joint assemblies may allow future failures to be predicted. The printed sensor sheet 1 can be produced in high volumes and at low cost. In figure 2 another sensor sheet 10 is also formed from an acetate substrate 14. The sensor sheet 10 has 4 openings 11 to allow fasteners such as flange bolts (not shown) to pass through the sensor sheet 10. The sensor sheet 10 also has a central opening 16 through which a pipe leading into a flange joint can pass. The sensor sheet 10 can thus be installed on the outside of a flange joint in the same way as a washer might be installed. The sensor sheet 10, which is flexible, has a slit 15 to allow the sensor sheet 10 to be opened and flexed into place around the pipe. Around each of the 4 openings 11 there is a printed pressure sensor 12, which may for example be a graphene sensor as described above. A temperature sensor 13 is also on the sensor sheet 10. As before, data from the temperature sensor 13, which may be a printed RTD, can be used to correct data from the pressure sensors 12 for temperature effects. The sensor sheet 10 has a tab 17 protruding from the sensor sheet 10, on which is located a first communication interface 18. The first

communication interface 18 has printed electrical contacts to interface with a suitable socket, but could take other forms such as a printed near-field-communication (NFC) interface. The first communication interface 18 is linked to the

pressure sensors 12 and the temperature sensor 13 by

conductors 19 printed on the sensor sheet 10. In use, data from the pressure sensors 12, for example resistance

measurements, are read by a device connecting to the first communications interface 18. When the first communication interface 18 is an NFC target, the changing properties, for example resistance, of the sensors 12, 13 may be used to alter the NFC target so as to allow an NFC initiator to read the data. The data are corrected for temperature effects using data read from the temperature sensor 13 in the same way. The data from the pressure sensors 12 can be used to monitor the tightness of fasteners such as flange bolts passing through each of the openings 11. Slackening of the pressure at any of the fasteners may indicate an increased failure risk and can be used to predict future failures. The data can be compared with other data from the same or other flange joint assemblies in order to predict future failures. The printed sensor sheet 10 can be produced in high volumes at low cost. In figure 3 a flange joint assembly 20 has two pipe ends 21 on each of which is a flange 22. Fasteners in the form of bolts 23 pass through the flanges 22 and are secured by nuts 24. Washers 25, or fishplates spanning more than one bolt 23, may be included between the bolts 23, nuts 24 and flanges 22. When the bolts 23 are tightened the load bearing surfaces, for example load bearing surface 26, of the bolts 23 press against the flanges 22, which in turn therefore have load bearing surfaces against which the bolts 23 press. Similarly, the nuts 24 and washers 25 have load bearing surfaces which press against the load bearing surfaces of the flanges 22 or bolts 23. The clamping force applied by the bolts 23 is thus transferred to the flanges 22 by the load bearing surfaces. The clamping force causes the faces 27 of the flanges 22 to press against each other, compressing a gasket 28 between them. The faces 27 and the surfaces of the gasket 28 between those faces 27 thus also form load bearing surfaces in the flange joint assembly 20 and the clamping force acts across those surfaces. A sensor sheet 30, which may be similar to the sensor sheet 1 in figure 1, can be inserted into the flange joint assembly 20 between the flanges 22. Since the sensor sheet 30 is between load bearing surfaces of the flange joint assembly 20, the sensors on the sensor sheet 30 can thus monitor the clamping force acting on the flange joint assembly 20. Alternatively, or additionally, a sensor sheet 40, which may be similar to the sensor sheet 10 in figure 2, can be inserted into the flange joint assembly 20 between the bolts 23 and the flange 22. Since the sensor sheet 40 is also between load bearing surfaces of the flange joint assembly 20, sensors on sensor sheet 40 can also monitor the clamping force acting of the flange joint

assemb1y 20.

In figure 4 a flange joint assembly 50 has pipe ends 51 on which are located flanges 52. Flanges 52 are clamped together by fasteners in the form of bolts 53 and nuts 54. A gasket 55 in the form of a sensor sheet similar to sensor sheet 1 of figure 1 is inserted between the flanges 52. The bolts 53 pass through openings 56 in the gasket 55 and the gasket 55 has a central opening 57 through which the fluid flowing in pipe ends 51 passes. In this embodiment the sensor sheet of the gasket 55 is made from a substrate compatible with the process fluid and the sensor sheet therefore acts as the gasket 55. The gasket 55 has 4 pressure sensors 58 and a temperature sensor 59 printed on the gasket 55. The gasket 55 also has a tab 60 that protrudes beyond the flanges 52. On the tab 60 there is printed a communications interface 61 in the form of electrical contacts. The communications interface 61 could be a short-range wireless communication interface, such as an NFC target. When the gasket 55 is installed in the flange joint assembly 50 between the flanges 52, the bolts 53 are tightened so as to clamp the flange joint assembly 50 closed. The pressure sensors 58 are compressed along with the gasket 55 between load bearing surfaces of the flange joint assembly, in this embodiment the faces of the flanges 52. The changing conductivity of the pressure sensors 58 with

clamping force and the changing conductivity of the temperature sensor 59 with temperature can be monitored via the communication interface 61, for example by measuring resistance between two contacts on the communication

interface 61 or by measuring the changes in an NFC target caused by the changing conductivities of the sensors 58, 59. The data from the temperature sensor 59 can be used to correct temperature effects in the data from the pressure sensors 58 in order to monitor the compressive pressure on each of the pressure sensors 58. That information can be used to monitor the clamping force on the flange joint assembly 50. The information can also be used to derive information about the distribution of that clamping force across the flanges 52. Both loss of clamping force and maldistribution of clamping force are significant causes of flange joint assembly failure and by monitoring them such failures can be predicted. To do that, trends in the data over time may be identified and potentially compared with other data series from other flanges in a central or cloud-based application.

In figures 5 and 6 a gasket 80 comprises a sensor sheet 70. The sensor sheet 70 may be similar to the sensor sheet 1 in figure 1. The sensor sheet 70 has 4 openings 71, through which fasteners in the form of bolts 77 pass when the gasket 80 is installed in a flange joint assembly 79. Conductors 74 printed on the sensor sheet 70 connect printed sensors (not shown) to a communications interface 73 printed on a

protruding tab 72 of the sensor sheet 70. The communications interface connects to a second communication interface in the form of a socket 75 which slots onto the end of the tab 72 over the communication interface 73. In that way data from the sensors can be read by a device connected to the second communication interface 75. The gasket 80 has a central opening 81 through which the process fluid passes when the gasket 80 is installed in the flange joint assembly 79. In this embodiment the sensor sheet 70 is not itself compatible with the process fluid flowing through the flange joint assembly 79. Therefore, to protect the sensor sheet 70 from the process fluid, and to ensure that the gasket 80 functions properly as a seal, the gasket 80 comprises a gasket material 76, which passes through the central opening 81 and folds around the sensor sheet 70 so as to cover the surfaces of the sensor sheet 70 surrounding the central opening 81. Looking at figure 6, as the bolts 77 and nuts 78 are tightened, the flange joint assembly 79 is compressed and the gasket

material 76 is pressed against the flanges 82 and the sensor sheet 70 and forms a seal that prevents leakage of the process fluid both out of the flange joint assembly 79 and onto the sensor sheet 70. Because the sensor sheet 70 is compressed between the load bearing surfaces of the flange joint assembly 79, the sensors can monitor the status of the flange joint assembly 79, for example by monitoring the clamping force. The sensor sheet 70 and the gasket material 76 can be separately produced and combined to form gasket 80 in high volumes and at low cost.

In figure 7 a sensor sheet 95 is installed on a flange joint assembly 90. The sensor sheet 95 is similar to sensor sheet 10 in figure 2. The flange joint assembly 90 has flanges 91, which are pressed together using fasteners in the form of bolts 92, nuts 93 and fishplates 94. The sensor sheet 95 is installed between the load bearing surfaces of the fishplates 94 and the flange 91. The fishplates 94 ensure that the substrate of the sensor sheet 95 is not twisted and damaged as the bolts 92 are tightened. Around each of the openings in the sensor sheet 95, through which the bolts 92 pass, are pressure sensors 96, two of which are visible in figure 7. Similar pressure sensors 96 surround the other bolts 92. The sensor sheet also has a temperature sensor (not visible in figure 7) . The pressure sensors 96 are connected to a first communication interface 89 on a tab 98 of the sensor sheet 95 by conductors 97 printed on the sensor sheet 95. The first communication interface 89 is connected to a second

communication interface 99 by a physical connection whereby a socket slots over electrical contacts printed on the tab 98. A short-range wireless communication interface could also be used. When the flange joint assembly 90 is compressed by tightening the bolts 92, the tightness of the bolts 92 can be monitored by the pressure sensors 96. As there is a pressure sensor 96 for each bolt 92 it is straightforward to associate the readings with the bolts 92. However, it would still be possible to compute readings from 3 pressure sensors spread across the sensor sheet 95 by computing the force balance from the 4 bolts 92 and the effect that would have at the location of the sensors. The data from the sensors can be used to monitor the integrity of the joint over time and could, for example, be used to alert operators if a bolt 92 needed tightening. The data can also be used in real time during installation of the flange joint assembly 90 to monitor tightening of the bolts 92 and direct an operator to tighten the bolts 92 by the correct amounts and in the correct order. The data can be monitored by a device

connected to the second communication interface 99. The sensor sheet 95 does not need to be compatible with the process fluid because it is on an outside of the flange joint assembly. The sensor sheet 95 also does not need to be able to form a sealing surface for the same reason. For that reason, the choice of materials may be wider for a sensor sheet 95 installed as a form of washer as in figure 7, which may, for example, permit more cost-effective manufacture.

In figure 8 a sensor sheet 100 is combined with an

electronics module 101. The sensor sheet 100 may be similar to the sensor sheet 1 of figure 1 and has 4 pressure sensors 102 and a temperature sensor 103. It will be understood that electronics modules such as electronics module 101 could be used with any of the sensor sheets of figures 1 to 7. The pressure sensors 102 and the temperature sensors 103 are connected by conductors 104 to a first communication

interface 105 located on a tab 106 protruding from the sensor sheet 100. The sensor sheet has openings 107 through which fasteners such as flange bolts can pass and a central opening 108 through which the process fluid can pass. The sensor sheet is mounted on a flange joint assembly 109 (only the outer diameter of the flange is visible in figure 8) and the electronics module 101 is mounted on the outside of the flange joint assembly 109. The electronics module has a housing 110 which is mounted on the flange joint assembly 109 so that the housing 110 covers the tab 106. The housing has a recess 114 into which the tab 106 fits and in which a second communication interface 116 is mounted. In this embodiment the second communication interface 116 is a socket in the housing 110 into which the first communication interface 105 on the tab 106 plugs. However, the first communication interface 105 could be a short-range wireless communication interface, such as an NFC tag, which is brought into

proximity with, and wirelessly connects to, a second

communication interface, such as an NFC initiator, mounted on or in the housing 110. The electronics module 101 has a processor 111 in the housing 110. The processor 111 is connected to the second communications interface 116 to receive data from the pressure sensors 102 and the

temperature sensor 103. The processor is connected to memory 113, where data and other information can be stored and to wireless communication module 112, which in this embodiment is a WirelessHART module. In some embodiments wireless communication module 112 may be replaced by a wired

communication module. The processor receives data from the pressure sensors 102 and the temperature sensor 103 and processes that data, for example by performing operations on that data, such as operations to convert conductivity

readings into pressure readings and to perform temperature compensation. The data from the sensors thus processed may be stored in the memory 113 and/or transmitted via the wireless communication module 112 to a remote location, such as an application running on a cloud server. The application may perform further operations, for example to analyse trends in data over time, and may present the data to a user, for example via a web application. The data could also be

transmitted to a nearby portable device, for example to allow real-time in-situ monitoring whilst carrying out an

inspection or maintenance action. The processor 111 may store the last transmitted data in the memory 113 and then compare subsequent data with that last transmitted data to determine whether or not the subsequent data differs significantly from the last transmitted data. If it does, the processor 111 may transmit the subsequent data via the wireless communication module 112 and store that data in the memory 113 as new values for the last transmitted data. The process can then be repeated. In that way only significant changes in the data are reported, which saves on power consumption by

transmitting unchanged data over and over again. The

processor 111, memory 113 and wireless communication module 112 are powered from a power supply, in this embodiment a battery 115 located in the housing 110. When the flange joint assembly 109 needs opening, for example because the data indicates that failure is imminent, the housing 110 is dismounted from the flange joint assembly 109 and the first communication interface 105 disconnected from the second communication interface 116. The sensor sheet 100 is removed from the flange joint assembly and discarded and a new sensor sheet 100 is provided. That new sensor sheet 100 is installed in the flange joint assembly and the new first communication interface 105 connected to the second

communication interface 116 in the housing 110, which is re- mounted on the flange joint assembly 109. In that way the costlier components of the system, which are contained in the separate electronics module 101 are re-used, while the sensor sheet 100 is replaced to ensure continued joint integrity.

In figure 9 a gasket 130 is to be installed on a flange joint assembly 131. The flange joint assembly 131 has a wireless identifier 132 mounted on it and the gasket 130 has a

wireless identifier 133 mounted on it, for example printed onto the gasket 130. The wireless identifiers 132 and 133 may be NFC tags. The gasket 130 may comprise a sensor sheet as described above, but may not. An operator 134 is equipped with a portable device 135, in this embodiment a smartphone running an app, which is equipped to read 136 the wireless identifiers 132 and 133. The read 136 enables the portable device 135 to read data identifying the gasket 130 and the flange joint assembly 131 and optionally to read data about their compatibility with each other. The portable device 135 may store information about the compatibility of different types of gaskets 130 with different types of flange joint assemblies 131 so that it can compute whether or not the gasket 130 is compatible with the flange joint assembly 131. However, in some embodiments, the portable device 135 will communicated wirelessly 137 with an application running on a remote, for example cloud, server 138. The portable device

135 will pass data read during the reads 136 to the

application on the server 138 and receive wirelessly 137 information from the application on the server 138 concerning the compatibility of the gasket 130 with the flange joint assembly 131. Regardless of how the compatibility information is generated, the portable device 135 may then display that compatibility information to the operator 134. The portable device 135 may also record information obtained in the reads

136 concerning the type of gasket 130 and the flange joint assembly 131 as a record of which gasket 130 has been

installed on the flange joint assembly 131. The recording may be performed in response to the operator 134 inputting on the portable device 135 that the gasket 130 has been installed. The recording may take place on the portable device 135, possibly for later upload or onward communication to a cloud or other application, or may take place by communicating the information wirelessly 137 to the application running on the server 138. The system thus permits confirmation that a gasket 130 is compatible with a flange joint assembly 131 and creates a reliable record of the installation of that gasket 130 on that flange joint assembly 131. The wireless

identifiers 132 and 133 may store unique information about the individual gasket 130 or flange joint assembly 131 or may store general information about the type of gasket 130 or flange joint assembly 131. It may be preferable for record creating purposes for the information on wireless identifier 132 to uniquely identify the individual flange joint assembly 131, but it may be sufficient for wireless identifier 133 to store general information about the type of gasket 130. It will be appreciated that the gasket 130 in this embodiment could be replaced or supplemented with a washer or a sensor sheet as described in other embodiments and the compatibility of that washer or sensor sheet checked for compatibility and recorded as installed.

In figure 10 an operator 155 is installing a flange joint assembly 150. The flange joint assembly has a sensor sheet (not shown) as described above installed, for example as shown in figure 7. The sensor sheet is connected to an electronics module 151 via communication interfaces on the sensor sheet and the electronics module 151. The connection may be as discussed above, for example as in figure 8. The operator 155 is equipped with a portable device 154, for example a smartphone running an app, which communicates wirelessly 153 with a wireless communication module in the electronics module 151. In that way the portable device 154 is fed information from the sensors on the sensor sheet in real time about the tightness of fasteners in the form of bolts 156. The portable device 154 may store information about the correct tightness of the bolts 156 or it may receive that information from the electronics module 151. However, in this embodiment, the portable device 154 also communicates wirelessly 152 with a remote, for example cloud, application running on a server 157. The remote application receives information from the portable device 154 about the flange joint assembly 150 and responds with information about the correct tightening of the bolts 156. The portable device 154 monitors the tightness of the bolts 156 as they are tightened in real time and displays instructions to the operator 155 about which bolt to tighten and by how much. In that way greater adherence to recommended installation practices may be obtained. The portable device 154 may store information about the tightening of the bolts 156, for example for audit purposes. That information may be stored on the portable device 154, possibly for later upload to a cloud application, or it may be communicated to the application running on the server 157 by the wireless communication 152. In this embodiment, and the embodiment of figure 9, the portable device 154 is a smartphone running an app, but the portable device 154 could be a bespoke device or other portable device running software to carry out the steps above .

In figure 11 a user interface 200 can be displayed, for example, on a portable device to an operator or on a web application to a remote user or in a control room to an operator. The user interface 200 indicates the readings 201, 202, 203, 204 from 4 pressure sensors. The pressure sensors are on a sensor sheet in a flange joint assembly as described above. The readings 201, 202, 203, 204 can be updated in real time to give information about the clamping force in the flange joint assembly. In this embodiment the user interface 200 is displayed on a portable device as an operator is installing the flange joint assembly. The user interface 200 indicates which fastener to tighten by highlighting the relevant reading 201, 202, 203, 204 in a different colour. When that fastener is sufficiently tightened the colour changes and a new reading 201, 202, 203, 204 is highlighted. For example, reading 201 may first be highlighted in red to indicate that the first fastener should be tightened. As the operator tightens the fastener the reading 201 is updated in real time as described above. When the correct tightness is reached, for example because the clamping force applied by the fastener has reached a predetermined force, the reading 201 changes to green to indicate that the operator should stop tightening the fastener. An audible indication may also be given. Reading 203 is then highlighted in red and the process repeated until the third fastener is correctly tightened at which point reading 203 turns green. Reading 202 may next be highlighted in red, followed by reading 204. At that point all fasteners may be correctly tightened or the process may repeat in the same or a different order to continue tightening the fasteners. In that way clear

instructions based on real time measurements are given to the operator to allow them to follow an approved tightening scheme whereby the fasteners are tightened in a specified order and by specified amounts. Such a system may greatly facilitate the proper installation of the flange joint assembly, which may in turn reduce the risk of premature failure of the joint. In subsequent inspections, which may be triggered by the ongoing monitoring of data from the sensors by a central or cloud application, the user interface 200 may display up-to-date readings 201, 202, 203, 204 from each of the sensors and display instructions as set out above for any further tightening of the fasteners that is required. It will be appreciated by persons skilled in the art that the above embodiments have been described by way of example only, and not in any limitative sense, and that various alterations and modifications are possible without departure from the scope of the invention as defined by the appended claims. For example, individual sensor sheets might be provided for each fastener. As another example, there may be more or fewer pressure sensors. In some embodiments there are three

pressure sensors positioned so as to allow the force balance across the flange joint assembly to be calculated. The printed sensors described above operate on the basis of changes in conductivity. However, other printed sensors may be used, for example based on changes in capacitance.

Claims

1. A system for monitoring a flange joint assembly, the system comprising a sensor sheet for positioning between adjacent load bearing surfaces in the flange joint assembly, wherein the sensor sheet comprises a plurality of sensors printed on a substrate.

2. A system according to claim 1, wherein the sensor sheet comprises a first communications interface, wherein the first communications interface is printed on the

substrate and wherein the sensors are connected to the first communications interface by conductors printed on the substrate.

3. A system according to claim 2, wherein the first

communications interface is a short-range wireless communication interface.

4. A system according to claim 2, wherein the first

communications interface comprises a plurality of electrical contacts printed on the substrate.

5. A system according to any preceding claim, wherein the substrate is a flexible substrate.

6. A system according to any preceding claim, wherein the sensors comprise at least three pressure sensors and at least one temperature sensor.

7. A system according to any preceding claim, wherein the sensor sheet is comprised in a gasket.

8. A system according to claim 7, wherein the sensor sheet comprises an opening and opposing surfaces of the sensor sheet surrounding the opening are at least partially covered by a gasket material folded around the sensor sheet and passing through the opening.

9. A system according to any of claims 1 to 6, wherein the sensor sheet is comprised in a washer.

10. A system according to claim 9, wherein the sensor sheet comprises multiple openings whereby fasteners can be inserted through the sensor sheet.

11. A system according to claim 10, wherein the sensor

sheet comprises a pressure sensor around each of the openings .

12. A system according to any of claims 2 to 4 or any of claims 5 to 11 when dependent on at least claim 2, wherein the system further comprises an electronics module, the electronics module comprising a housing separate from the sensor sheet, the housing containing a processor and a wireless communication module, wherein the electronics module comprises a second communications interface configured to reversibly connect to the first communications interface, and wherein the processor is configured to process data received from the sensors via the first and second communications interfaces and to transmit the processed data via the wireless

communication module.

13. A system according to claim 12, wherein the electronics module comprises a battery to power the electronics module, wherein power from the battery can be supplied to the sensors via the first and second communications interfaces .

14. A system according to claim 12 or claim 13, wherein the wireless communication module is a WirelessHART module.

15. A system according to any of claims 12 to 14, wherein the first and second communications interface are short- range wireless communication interfaces.

16. A system according to claim 15 wherein the first

communications interface is an NFC target and the second communications interface is an NFC initiator.

17. A system according to any of claims 12 to 14, wherein the first communications interface comprises a plurality of electrical contacts printed on the substrate and the second communications interface comprises a socket configured to mate with the electrical contacts.

18. A flange joint assembly comprising a system according to any preceding claim.

19. A flange joint assembly according to claim 18 wherein the system is according to any of claims 12 to 17, wherein the housing is mounted on the flange joint assembly .

20. A flange joint assembly according to claim 19, wherein the first communications interface is located on a tab of the sensor sheet, wherein the tab protrudes from the flange joint assembly and the housing is mounted on the flange joint assembly so as to cover the tab.

21. A method of monitoring a flange joint assembly

comprising providing a system according to any of claims 1 to 17 and monitoring data from the sensors over time.

22. A method according to claim 21 wherein the system is according to any of claims 12 to 17, wherein the

processor compares data from the sensors to previous data from the sensors and transmits the data via the wireless communication module if the data is different from the previous data.

23. A method according to claim 21 or claim 22, wherein the data is compared with historical data from the sensors, or from other sensors mounted on the or other flange joint assemblies, in order to predict future leakages of the flange joint assembly.

24. A method according to any of claims 21 to 23 wherein future leakage is predicted by monitoring a clamping force on the flange joint assembly over time.

25. A gasket comprising a system according to any of claims 1 to 6.

26. A washer comprising a system according to any of claims 1 to 6.

27. Use of a gasket according to claim 25 or a washer

according to claim 26, in a method according to any of claims 21 to 24.

28. A method of monitoring a flange joint assembly

comprising : a. providing a first sensor sheet, wherein the first sensor sheet comprises a plurality of sensors printed on a substrate and a first communications interface, wherein the first communications

interface is printed on the substrate and wherein the sensors are connected to the first

communications interface by conductors printed on the substrate; b. providing an electronics module, the electronics module comprising a housing separate from the sensor sheet, the housing containing a processor and a wireless communication module, wherein the electronics module comprises a second

communications interface, and wherein the processor is configured to process data received from the sensors via the first and second communications interfaces and to transmit the processed data via the wireless communication module; c. positioning the first sensor sheet between adjacent load bearing surfaces in the flange joint assembly; d. mounting the electronics module on the flange joint assembly and connecting the first communications interface to the second communications interface; e. monitoring data from the sensors on the first

sensor sheet over time; f . disconnecting the first communications interface from the second communications interface; g. removing the first sensor sheet; h. providing a second sensor sheet, wherein the second sensor sheet comprises a plurality of second sensors printed on a second substrate and a second first communications interface, wherein the second first communications interface is printed on the second substrate and wherein the second sensors are connected to the second first communications interface by second conductors printed on the second substrate; i. positioning the second sensor sheet between

adjacent load bearing surfaces in the flange joint assembly; j . connecting the second first communications

interface to the second communications interface; and k. monitoring data from the second sensors on the

second sensor sheet over time.

29. A method according to claim 28, wherein steps f to k are performed when the data from the sensors on the first sensor sheet monitored in step e indicate that failure of the flange joint assembly is imminent.

30. A method of installing a gasket or washer on a flange joint assembly, wherein the method comprises: a. providing a wireless identifier on each of (a) the gasket or washer and (b) the flange joint assembly, the wireless identifiers storing data related to the compatibility of the gasket or washer with the flange joint assembly; b. providing a device configured to interface with the wireless identifiers, the device comprising a processor configured to analyse data read from the wireless identifiers by the device; c. reading the wireless identifiers with the device; d. analysing the data read from the wireless

identifiers using the processor to determine that the gasket or washer is compatible with the flange joint; and e. installing the gasket or washer on the flange joint assembly .

31. A method according to claim 30, wherein the gasket is a gasket according to claim 25 or the washer is a washer according to claim 26.

32. A method according to claim 31, wherein the wireless identifier is printed on the substrate.

33. A method according to any of claims 30 to 32, wherein the data related to the compatibility of the gasket or washer with the flange joint assembly comprises data identifying the gasket or washer and the flange joint assembly .

34. A method of installing a system according to any of

claims 1 to 17 on a flange joint assembly, wherein the method comprises: a. providing a wireless identifier on each of (a) the sensor sheet and (b) the flange joint assembly, the wireless identifiers storing data related to the compatibility of the sensor sheet with the flange joint assembly; b. providing a device configured to interface with the wireless identifiers, the device comprising a processor configured to analyse data read from the wireless identifiers by the device; c. reading the wireless identifiers with the device; d. analysing the data read from the wireless

identifiers using the processor to determine whether the sensor sheet is compatible with the flange joint assembly; and e. installing the system on the flange joint assembly.

35. A method according to claim 34, wherein the wireless identifier on the sensor sheet is comprised in the first communications interface.

36. A method according to claim 34 or claim 35, wherein the data related to the compatibility of the sensor sheet with the flange joint assembly comprises data

identifying the sensor sheet and the flange joint assembly .

37. A method of installing a flange joint assembly,

comprising providing a system according to any of claims 1 to 17, positioning the sensor sheet between adjacent load bearing surfaces in the flange joint assembly, tightening fasteners on the flange joint assembly, monitoring data from the sensors while the fasteners are tightened and providing a signal when the fasteners are correctly tightened.

38. A method according to claim 37 wherein the system is according to any of claims 12 to 17, wherein the housing is mounted on the flange joint assembly and wherein the signal is provided on a portable device wirelessly connected to the electronics module via the wireless communication module.