GB2536962A

GB2536962A - Apparatus and method for joint monitoring

Info

Publication number: GB2536962A
Application number: GB1505762.3A
Authority: GB
Inventors: Cattley Robert
Original assignee: University of Huddersfield
Current assignee: University of Huddersfield
Priority date: 2015-04-02
Filing date: 2015-04-02
Publication date: 2016-10-05
Also published as: WO2016156828A1; GB201505762D0

Abstract

An apparatus and a method for monitoring the condition of one or more joints each formed between two adjacent flanges 10a, 12a are provided. The apparatus comprises: one or more gasket bodies 14a, 14b formed of a deformable material for positioning between adjacent flanges 10a, 12a; and a transmission line 16 for positioning between adjacent flanges 10a, 12a and in contact with at least one of the one or more gasket bodies 14a, 14b. The apparatus further comprises means for determining changes in the characteristic impedance along the transmission line 16, where a change of characteristic impedance is indicative of a deformation of the one or more gasket bodies 14a, 14b and the condition of the one or more joints.

Description

Apparatus and Method for Joint Monitoring [0001] This invention relates to an apparatus and method for joint monitoring, and, in particular, to an apparatus and method for monitoring the condition of a joint formed between two adjacent flanges.

BACKGROUND

[0002] Joints, such as joints between two pipe ends, are often formed by the connection of a pair of adjacent flanges and often include deformable gaskets between the flanges. A gasketed joint is preloaded to hold the two flanges together, where, typically, preloading is achieved by way of a plurality of circumferentially distributed bolts through the flanges. The gasket serves to fill any gap between the flanges and make the joint substantially pressure and vacuum tight. Additionally, the gasket may compensate for any unevenness in the opposing flange surfaces that may arise from manufacture or installation. Similarly, the gasket may compensate for any angular misalignment between the flanges when they are connected to one another and preloaded. For example, if the preloading is uneven about the circumferences of the flanges, the faces of the flanges may not lie parallel to one another as ideally desired.

[0003] Over time, the applied preloading may gradually diminish. For example, nuts and bolts may loosen and provide less preloading on the flanges due to vibration, seismic changes or other external factors. As the preloading diminishes, the gasket may relax and expand to fill the gap created. Typically, such expansion may be up to around 10% of the compressed gasket thickness and serves to allow the gasket to maintain the integrity of the joint.

[0004] However, over time, whether by gradual diminishment of the preloading or sudden failure of the gasket or the preloading, gaskets may fail to fill the gap between the flanges leading to leakage through the joint. Such leaks are undesirable and may be potentially dangerous, particularly if the type, temperature or pressure of the leaking substance poses a risk to nearby operators or surroundings.

[0005] US patent publication US2003/0042688 describes an apparatus and method for measuring gasket compression forces for pipe connections. In particular, the forces are described as being determined by measurement of the capacitance between a capacitor plate on the gasket and one of the pipe flanges or another capacitor plate on the gasket. As such, the method relies on measurements being taken at two spatially separated locations.

[0006] It is an object of certain embodiments of the present invention to overcome certain disadvantages associated with the prior art.

BRIEF SUMMARY OF THE DISCLOSURE

[0007] In accordance with an aspect of the present invention there is provided an apparatus for monitoring the condition of one or more joints each formed between two adjacent flanges, the apparatus comprising: one or more gasket bodies formed of a deformable material for positioning between adjacent flanges; a transmission line for positioning between adjacent flanges and in contact with at least one of the one or more gasket bodies; and means for determining changes in the characteristic impedance along the transmission line, where a change of characteristic impedance is indicative of a deformation of the one or more gasket bodies and the condition of the one or more joints.

[0008] In certain embodiments, the transmission line is an electrical transmission line. In other embodiments the transmission line is an optical transmission line.

[0009] The means for determining changes in the characteristic impedance along the transmission line may include signal generation means for generating a signal for transmission along the transmission line, and detection means for detecting a reflected signal from the transmission line. Additionally, the means for determining changes in the characteristic impedance along the transmission line may include processing means for processing the reflected signal and determining changes in the characteristic impedance along the transmission line. The means for determining changes in the characteristic impedance along the transmission line may include means for determining the reflection coefficient of the transmission line. The means for determining changes in the characteristic impedance along the transmission line may utilize time domain reflectometery (TDR).

[0010] The one or more gasket bodies may comprise a first gasket body for disposal on a first side of the transmission line, and a second gasket body for disposal on a second side of the transmission line, wherein the first side of the transmission line is opposite the second side of the transmission line.

[0011] In certain embodiments, the transmission line may be at least partially embedded in the one or more gasket bodies.

[0012] The apparatus may further comprise one or more joints each formed between two adjacent flanges. One or both of the two adjacent flanges may be pipe flanges. One of the two adjacent flanges may include a groove and the transmission line is at least partially disposed in the groove.

[0013] The apparatus may further comprise a display for displaying information indicative of the condition of the joint.

[0014] The apparatus may further comprise a connector for permitting an optical and/or electrical connection to the transmission line.

[0015] In accordance with another aspect of the present invention, there is provided a method for monitoring the condition of one or more joints each formed between two adjacent flanges, the method comprising: providing one or more deformable gasket bodies and a transmission line between adjacent flanges wherein the transmission line is in contact with at least one of the one or more gasket bodies; determining changes in the characteristic impedance along the transmission line, where a change of characteristic impedance is indicative of a deformation of the one or more gasket bodies and the condition of the one or more joints.

[0016] Determining changes in the characteristic impedance along the transmission line may include generating a signal, transmitting the signal along the transmission line, and detecting a reflected signal from the transmission line.

[0017] Determining changes in the characteristic impedance along the transmission line may include calculating the reflection coefficient of the transmission line.

[0018] Determining changes in the characteristic impedance along the transmission line may utilize time domain reflectometery (TDR).

[0019] In certain embodiments, the step of generating a signal may comprise generating an electrical signal. In other embodiments, the step of generating a signal comprises generating an optical signal.

[0020] In accordance with another aspect of the present invention, there is provided a tubular member having a flange, wherein the flange has a connection face for mounting to a flange of an adjacent tubular member, and wherein the flanges includes a groove in the connection face for receiving a transmission line. The tubular member may further comprise a transmission line disposed in the groove. In certain embodiments, the tubular member may be a pipe, or a cylinder head for an internal combustion engine.

[0021] In accordance with another aspect of the present invention, there is provided a gasket body having a transmission line at least partially connected to the gasket body. The gasket body may include a first part and a second part, and the transmission line is at least partially disposed between the first part and second part.

[0022] In accordance with another aspect of the present invention, there is provided a kit of parts comprising one or more gasket bodies and a transmission line, wherein the one or more gasket bodies and the transmission line are configured for disposal between two adjacent flanges of a joint with the transmission line in contact with at least one of the one or more gasket bodies

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which: Figure 1 is a cross-sectional view of a joint formed between two pipes in accordance with an embodiment of the present invention; and Figure 2 is a perspective view of a pipe in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION

[0024] Figure 1 shows a joint formed between a first pipe 10 and a second pipe 12 in accordance with an embodiment of the present invention. The first pipe 10 has a first flange 10a and the second pipe 12 has a second flange 12a. The joint is formed by connecting means (not shown) that connect the first flange 10a to the second flange 12a. Suitable connecting means include, but are not limited to, nuts and bolts, where the bolts may pass through a plurality of apertures distributed circumferentially around each of the first and second flanges 10a,12a. Between the adjacent first flange 10a and second flange 12a there is disposed a first gasket body 14a and a second gasket body 14b. Each of the first gasket body 14a and second gasket body 14b is formed of a deformable material such that the preloading of the joint provides an initial compression to the first and second gasket bodies 14a,14b. The first gasket body 14a and second gasket body 14b comprise a dielectric layer and each serves to provide sealing to the joint such that any fluid passing between the first pipe 10 and second pipe 12 does not leak.

[0025] Any reduction of the preloading (e.g. gradual loosening of nuts and bolts due to vibrations) or any irregularities in the alignment or finish of the first and second flanges 10a,12a permits each of the first and second gasket bodies 14a,14b to expand towards an uncompressed configuration. Therefore, the first and second gasket bodies 14a,14b may maintain a seal around the joint for a limited and predetermined degree of expansion. In alternative arrangements, one or any other number of gasket bodies may be present between the flanges 14a,14b to achieve the desired effect.

[0026] In accordance with an embodiment of the present invention, a transmission line 16 is disposed between the first flange 10a and second flange 12a. The transmission line 16 is arranged to contact the first gasket body 14a and second gasket body 14b when the joint is in a preloaded state. In embodiments where another number of gasket bodies are present, the transmission line 16 should contact at least one of the gasket bodies when the joint is in a preloaded state. In certain embodiments, the transmission line 16 may be embedded in one of the gasket bodies. Optionally, more than one transmission line 16 may be provided where each is in contact with at least one of the gasket bodies when the joint is in a preloaded state. Any one or more of the transmission lines 16 may be disposed radially inwardly or radially outwardly of the connecting means (e.g. radially inward or radially outwards of bolts connecting the first flange 10a and second flange 12a.

[0027] In certain embodiments, the transmission line 16 is an electrical transmission line such as an electrical conductor. In other embodiments, the transmission line 16 may be an optical transmission line such as an optical fiber. In either case, the transmission line 16 has the inherent property of characteristic impedance Zo which is partly dependent on the geometry and material of the transmission line 16. Additionally, the characteristic impedance, Zo, of the transmission line 16 varies as 4 ocVT., where c is the dielectric constant of the dielectric layer provided by the first and second gasket bodies 14a,14b. Furthermore, the characteristic impedance varies as 4 cc log St, where St is the change in thickness of the dielectric layer. Considering embodiments where the transmission line 16 is an optical transmission line, the skilled person will appreciate that the characteristic impedance of the transmission line 16 will be inversely proportional to the refractive index of the transmission line 16. In such embodiments, deformation of the dielectric (and resulting deformation of the transmission line 16) results in a change in the refractive index of the transmission line 16, thereby causing a change in the characteristic impedance.

[0028] In certain embodiments, the transmission line 16 may include an outer sheath or other outer layer. In such embodiments, the outer sheath or other outer layer may be the component of the transmission line 16 that contacts at least one of the one or more of the gasket bodies when the joint is in a preloaded state.

[0029] The first pipe 10 is provided with a connector 18 which may permit an electrical and/or optical signal to be transmitted to and received from the transmission line 16. In the embodiment shown in Figure 1, the connector 18 passes through the first flange 10a. In alternative embodiments, the connector 18 may be positioned elsewhere to form a connection to the transmission line 16. In certain embodiments, a direct connection may be made between a signal generating means and the transmission line 16 without the need for the intermediate connector 18.

[0030] In certain embodiments a signal generating means (e.g. a signal generator) may be provided to generate a signal for transmission along the transmission line 16. The generated signal may be an electrical signal or an optical signal. Additionally, detecting means (e.g. a detector) may be provided for detecting a reflected signal from the transmission line 16.

Furthermore, processing means (e.g. a processor) may be provided to process the reflected signal and determine changes in the characteristic impedance along the transmission line 16.

[0031] In certain embodiments, changes in the characteristic impedance along the transmission line 16 may be determined by determining the reflection coefficient of the transmission line 16. For example, the reflection coefficient may be the ratio of a property of the reflected signal relative to the same property of the incident (i.e. input) signal along the transmission line 16. The signal will be transmitted at points along the transmission line 16 where there is a change in characteristic impedance. As discussed above, such changes in characteristic impedance will depend on the deformation of the one or more gasket bodies 14a,14b in contact with the transmission line 16. For electrical signals, the reflection coefficient may be the voltage (or other amplitude) of the reflected signal relative to (e.g. divided by) the voltage (or other amplitude) of the incident signal. For optical signals, the reflection coefficient may the amplitude or intensity of the reflected signal relative to (e.g. divided by) the amplitude or intensity, respectively, of the incident signal.

[0032] In certain embodiments, the determined change in characteristic impedance may be attributed to a specific location along the transmission line 16. For example, for a transmission line 16 of known length and a signal of known transmission speed, details concerning the location of reflections of the signal can be determined by considering the time delay between generation of certain features of the incident signal and detection of the same features of the reflected signal. In such embodiments, the precise or approximate area of changing gasket or joint condition may be identified and corrected or repaired.

[0033] One particularly preferable method of determining changes in the characteristic impedance along the transmission line 16 utilizes time domain reflectometery (TDR). For TDR analysis, the generated signal comprises a step or impulse of energy (e.g. electrical or optical). The magnitude, duration and/or shape of the reflected signal is subsequently detected and compared with the input signal in order to determine the change in characteristic impedance. A reflectometer may be used to perform the TDR analysis. In preferable embodiments, the reflectometer has a resolution that is sufficient to discriminate distances that are less than the spacing between adjacent ones of the connecting means (e.g. bolts) connecting the first flange 10a to the second flange 12a. In certain embodiments, the spacing between adjacent ones of the connecting means may be of the order of several tens of mm (e.g. around 50 mm). Around pico-second per division resolution is preferable in certain embodiments. In certain embodiments, a reflection coefficient sensitivity of around 0.01 per division would be preferable. The TDR rise time is preferably as fast as possible. In certain embodiments, the maximum rise time is around 100 pico-seconds. If a vector network analyzer is used as a TDR, the sweep may be set to cover from the lowest frequency available to about 5 -7 GHz, where higher frequencies will provide better resolution. Since the network analyzer output is in the frequency domain, it may be transformed into the time domain by the use of Fourier transforms to provide a TDR display. In certain embodiments, a mode suppressor or other suitable apparatus may be utilized to clean the signal (e.g. by removing certain modes).

[0034] In accordance with embodiments of the present invention, the changes in the characteristic impedance along the transmission line 16 may be determined by direct or indirect means. For example, the characteristic impedance may be measured directly. Alternatively, other parameters (e.g. reflection coefficient) may be measured and used to determine changes in the characteristic impedance.

[0035] By determining changes in the characteristic impedance along the transmission line 16, the preloading of a joint can be more uniformly and effectively achieved. For example, an imbalanced preloading will result in a greater degree of compression (i.e. deformation) of the one or more gasket bodies in a particular area relative to other areas. This differential compression will in turn result in a differential characteristic impedance along the transmission line 16 which may be determined in accordance with embodiments of the present invention.

Therefore, by monitoring changes in the characteristic impedance along the transmission line 16 during preloading, the operator can adjust the preloading around the joint so as to achieve a uniform and balanced (or other desired) preload. Similarly, continued monitoring of determined changes in characteristic impedance along the transmission line 16 may help identify a local reduction in the applied preloading or any other early indications of the joint failing (e.g. degradation of the one or more gasket bodies). By determining the changes in characteristic impedance, the joint may be preloaded correctly once more, or the one or more gasket bodies may be replaced before the joint fails entirely (which may permit leakage therethrough). Certain embodiments of the present invention therefore allow for in situ monitoring of the condition of joints and advantageously may permit operators to correct any anomalies prior to the joints failing. As such, embodiments of the present invention may help avoid the need to shut pipe lines down for repair after failure. Such shut downs may be very costly and inconvenient.

[0036] In certain embodiments of the present invention, there may be provided display means (e.g. a display such as an oscilloscope display) for displaying information indicative of the condition of the joint. Considering embodiments that include display means and utilize TDR, a graphical output on the display means may indicate the condition of the joint. If the one or more gasket bodies (or, more generally, the joint) was to fail, the graphical output displayed may correspond to an open circuit (e.g. if the joint was facilitating the flow of a non-conducting substance) or a short circuit (e.g. if the joint was facilitating the flow of a conducting substance). The height of the peaks of the graphical output may be representative of the severity of the problem and the position (e.g. along the x-axis) on the graphical output may be indicative of the location along the transmission line 16 of the problem.

[0037] In certain embodiments of the present invention, a single transmission line 16 may be in contact with the one or more gasket bodies of more than one joint. In such embodiments, determining the location along the transmission line 16 associated with a change in characteristic impedance will serve to identify which of the joints (and where in that joint) a problem may exist.

[0038] Figure 2 shows a modified first pipe 10 that includes a first flange 10a and a connector 18. The connector 18 shown in Figure 2 is orientated parallel to the plane of the first flange 10a in contrast to the connector 18 shown in Figure 1 which is orientated perpendicular to the respective first flange 10a. Indeed, in certain embodiments, the connector 18, if present, may be located in any suitable position and orientated in any suitable orientation. The first flange 10a of the embodiment of Figure 2 additionally includes a groove 20 on the face that would form the connection with an adjacent flange (i.e. a connection face). The groove 20 is continuous around the first flange 10a and is configured to receive at least part of the transmission line 16 such that when a gasket body is provided against the connection face, the transmission line 16 may contact the gasket body. The first flange 10a shown in Figure 2 additionally includes a plurality of holes 22 circumferentially distributed around the first flange 10a. The plurality of holes 22 may receive fixing means, such as a plurality of bolts, for fixing the first flange 10a to an adjacent flange when forming a joint.

[0039] Whilst embodiments of the invention are described above in relation to joints between pipes, other embodiments of the invention may relate to non-pipe applications. For example, certain embodiments of the invention may relate to the monitoring of any joint formed between two adjacent flanges of tubular bodies. In this context, the term flange relates to a mating surface of the joint (i.e. where two mating surfaces meet at the joint) which is connected by the connecting means to form the joint. Certain embodiments of the invention relate to the monitoring of a joint formed in a cylinder head.

[0040] Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of them mean "including but not limited to", and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0041] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

[0042] The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

Claims

CLAIMS1. An apparatus for monitoring the condition of one or more joints each formed between two adjacent flanges, the apparatus comprising: one or more gasket bodies formed of a deformable material for positioning between adjacent flanges; a transmission line for positioning between adjacent flanges and in contact with at least one of the one or more gasket bodies; and means for determining changes in the characteristic impedance along the transmission line, where a change of characteristic impedance is indicative of a deformation of the one or more gasket bodies and the condition of the one or more joints.
The apparatus of claim 1, wherein the transmission line is an electrical transmission line.
3. The apparatus of claim 1, wherein the transmission line is an optical transmission line.
4. The apparatus of any preceding claim, wherein the means for determining changes in the characteristic impedance along the transmission line includes signal generation means for generating a signal for transmission along the transmission line, and detection means for detecting a reflected signal from the transmission line.
5. The apparatus of claim 4, wherein the means for determining changes in the characteristic impedance along the transmission line includes processing means for processing the reflected signal and determining changes in the characteristic impedance along the transmission line.
6. The apparatus of any of claims 4 or 5, wherein the means for determining changes in the characteristic impedance along the transmission line includes means for determining the reflection coefficient of the transmission line.
7. The apparatus of any of claims 4 to 6, wherein the means for determining changes in the characteristic impedance along the transmission line utilises time domain reflectometery (TDR).
8. The apparatus of any preceding claim, wherein the one or more gasket bodies comprises a first gasket body for disposal on a first side of the transmission line, and a second gasket body for disposal on a second side of the transmission line, wherein the first side of the transmission line is opposite the second side of the transmission line.
9. The apparatus of any preceding claim, wherein the transmission line is at least partially embedded in the one or more gasket bodies.
10. The apparatus of any preceding claim, further comprising one or more joints each formed between two adjacent flanges.
11. The apparatus of claim 10, wherein one or both of the two adjacent flanges are pipe flanges.
12. The apparatus of claim 10 or 11, wherein one of the two adjacent flanges includes a groove and the transmission line is at least partially disposed in the groove.
13. The apparatus of any preceding claim, further comprising a display for displaying information indicative of the condition of the joint.
14. The apparatus of any preceding claim, further comprising a connector for permitting an optical and/or electrical connection to the transmission line.
15. A method for monitoring the condition of one or more joints each formed between two adjacent flanges, the method comprising: providing one or more deformable gasket bodies and a transmission line between adjacent flanges wherein the transmission line is in contact with at least one of the one or more gasket bodies; determining changes in the characteristic impedance along the transmission line, where a change of characteristic impedance is indicative of a deformation of the one or more gasket bodies and the condition of the one or more joints.
16. The method of claim 15, wherein determining changes in the characteristic impedance along the transmission line includes generating a signal, transmitting the signal along the transmission line, and detecting a reflected signal from the transmission line.
17. The method of claim 16, wherein determining changes in the characteristic impedance along the transmission line includes calculating the reflection coefficient of the transmission line.
18. The method of claim 16 or 17, wherein determining changes in the characteristic impedance along the transmission line utilises time domain reflectometry (TDR).
19. The method of any of claims 16 to 18, wherein the step of generating a signal comprises generating an electrical signal.
20. The method of any of claims 16 to 18, wherein the step of generating a signal comprises generating an optical signal.
21. A tubular member having a flange, wherein the flange has a connection face for mounting to a flange of an adjacent tubular member, and wherein the flanges includes a groove in the connection face for receiving a transmission line.
22. The tubular member of claim 21, further comprising a transmission line disposed in the groove.
23. The tubular member of claim 21 or 22, wherein the tubular member is a pipe, or a cylinder head for an internal combustion engine.
24. A gasket body having a transmission line at least partially connected to the gasket body.
25. The gasket body of claim 24, wherein the gasket body includes a first part and a second part, and the transmission line is at least partially disposed between the first part and second part.
26. A kit of parts comprising one or more gasket bodies and a transmission line, wherein the one or more gasket bodies and the transmission line are configured for disposal between two adjacent flanges of a joint with the transmission line in contact with at least one of the one or more gasket bodies.
27. An apparatus for monitoring the condition of a joint formed between two adjacent flanges substantially as hereinbefore described with reference to the accompanying drawings.
28. A method for monitoring the condition of a joint formed between two adjacent flanges substantially as hereinbefore described with reference to the accompanying drawings.