JP2003504516A - Anode monitoring system and method - Google Patents

Abstract

(57) [Abstract] An anode monitoring system for monitoring an intact state of an anode (2) provided on a metal structure such as a pipeline system (1). A signal circuit (S _n ) including the pipeline (1) and one of the anodes (2) is set up and a suitable signal is searched for in the central office (4). The reception of the signal at the central office (4) depends on the intact state of the anode (2) under the current test. If the anode (2) is missing or defective, the expected signal is not received and a failure of the anode (2) can be detected. A notch filter (5) is inserted in series between each anode (2) and the pipeline (1). The filter (5) provides a high impedance that can signal across the cathodic protection system but does not interfere with the cathodic protection system.

Description

Detailed Description of the Invention

The present invention relates to an anode monitoring system and an anode monitoring method for monitoring an intact state of an anode provided on a metal structure for protecting a cathode. Examples of such structures include elements used in pipelines and pipeline systems, such as trees,
Manifolds and processing plants.

[0002] Subsea pipelines are typically protected by the use of cathode protection. This means that the sacrificial anodes are spaced apart along their length. The continued presence and effectiveness of the anode is essential to the function of cathode protection. Therefore, the anode must be regularly inspected to ensure the continuous integrity of the pipe itself. Currently, this is done through the use of remote controls and / or potential testing. Each of these methods is very expensive and can only be implemented if weather conditions permit.

It is an object of the present invention to provide a technique for monitoring the integrity of the anode that mitigates at least some of the problems of existing techniques.

The anode is effective in several ways, for example, if the anode is completely separated from the pipeline, loses electrical contact with the pipeline, and collapses to the extent that it ceases to be effective. It will be understood that no longer. It is desirable to be able to detect when some of these events occur.

According to a first aspect of the present invention, an anode monitoring system for monitoring the integrity of an anode provided to a metal structure for protection of the cathode, the system having a metal structure and a selected anode. A signal circuit having at least one signal communication path, whereby a characteristic of the signal circuit depends on the effectiveness of the selected anode, and a signal generation for generating a signal and adding the signal to the signal circuit. A system is provided that includes means and a central office that monitors the signal of the signal circuit to thereby determine if the selected anode is valid.

A second aspect of the present invention is an anode monitoring method for monitoring an intact state of an anode provided on a metal structure for protecting a cathode, the method including generating a signal and adding the signal to a signal circuit. The signaling circuit comprises at least one signaling channel having the metal structure and a selected anode, whereby the characteristics of the signaling circuit depend on the effectiveness of the selected anode. And a step of monitoring a signal on the signal circuit at a central office to thereby determine if the selected anode is valid.

[0007] Preferably, the signal generating means is configured to add a signal indicating the validity of the selected anode to the signal circuit when the selected anode is valid.

Preferably, said signal generating means or at least one element thereof is arranged on said selected anode.

The configuration may be such that the lack or defect of the selected anode is detectable as a break in the signal circuit. The circuit break may be detectable as a result of the inability to add a signal to the signal circuit and / or the inability to receive a signal from the circuit. The lack or defect of the selected anode may be detectable due to the lack of the expected signal. The expected signal may be based on changes in the effective impedance of the signal circuit.

The signal circuit may have a return path through ground. Preferably, the selected anode, when available, provides a conductive path from the metal structure to ground.
If the selected anode provides a path to ground, the lack or defect of the selected anode may be detectable as a loss of ground connection.

The signal circuit may include impedance means. The impedance means may be arranged between the selected anode and the rest of the metal structure.
The impedance means may be provided in series between the selected anode and the metal structure.

The impedance means may comprise a separating means. The impedance means may include an inductance means. The impedance means may include filter means. The impedance means may be configured to provide a high impedance to the time-varying signal within one or more selected range of frequencies and a low impedance to the signal outside of the selected range. The impedance means is
The real part of the impedance may be configured to be substantially zero. This means that there is little or no attenuation of the DC component of the signal passing through the impedance means.

The use of said inductance means and / or filter means makes it possible to provide a high impedance to the time-varying signal used for signal transmission when metal structures are used to carry the signal. It has the advantage that it can be chosen to reduce losses and provide a low impedance to the current used for cathode protection.

The transmitting means and the receiving means may be able to provide so that the data can be transmitted along the metal structure. Sending and receiving means may be provided to assist the anode monitoring operation and / or provide a separate data sending function.

The transmitting means and / or the receiving means may be arranged to be connected across said impedance means and to transmit and / or receive signals across said impedance means.

When a signal is received across an impedance means, the use of a filter means as an impedance means has the additional advantage that noise generated outside the frequency band of interest before it enters the receiver is attenuated. Have.

In one embodiment, the signal generating means comprises transmitter means, the signal circuit requires that the transmitter means is grounded, and the selected anode is of an anode detectable by the central office when enabled. Ground is provided to allow the transmission of a signal indicating validity. If the selected anode is defective or missing, the transmission means will not have a ground reference and the transmission means will be unable to transmit a signal. Thus, in the absence of signal, it can be determined that the selected anode is defective or missing. In such an embodiment, the transmitting means is preferably connected across the impedance means.

In another embodiment, the signal generating means comprises a reference signal generating means configured to add a reference signal to the signal circuit, and an effective impedance of the signal circuit, the transmitted data. An effective impedance changing means for changing the central circuit according to the present invention, wherein the central office has monitoring means for monitoring a change in the reference signal caused by changing the effective impedance of the signal circuit, the signal circuit being the selected one. A defect or lack of an anode is configured to cause a break in the signal circuit, whereby the ineffectiveness of the selected anode is detectable at the central office due to the lack of change in the reference signal.

In such an embodiment, the reference signal generating means may be arranged at a position apart from the selected anode. The impedance changing means may be arranged adjacent to the selected anode.

[0020] Preferably, the signal circuit may include a plurality of signal communication paths each including the metal structure and each anode. The sub-features described above relating to the selected anode apply equally to each of the respective anodes in a system having multiple signal channels. An independent signal generating means or at least one independent element of the signal generating means may be arranged on each anode.

Different data and / or different signals and / or different frequencies may be associated with each of the respective anodes. The system may be configured such that the signals associated with each anode are generated at different times. The signal may be randomly generated. Thus, for example, certain anodes are ineffective and, therefore,
If the relevant data / signal is not received at the central office, it can be determined which anode is inactive.

According to the third aspect of the present invention, the transmitting means and the receiving means, which originally have different purposes, operate as a signal communication path between the transmitting means and the receiving means in use. A metal structure, the metal structure including at least one anode provided for protection of the cathode, the impedance transmission means being arranged between the metal structure and the anode. It

The data transmission system may include a signal circuit having a metal structure and a return path.
The return route is via earth. The signal circuit may have an anode. Preferably, the anode provides a path from the metal structure to ground.

The impedance means may be provided in series between each anode and the metal structure.

The impedance means may include an inductance means. The impedance means may include filter means. The impedance means is configured to have a high impedance for the time-varying signal within one or more selected range of frequencies and a low impedance for the signal outside of the selected range. The use of inductance means or filter means provides the advantages mentioned above.

According to a fourth aspect of the invention there is provided a device for use in a metal structure in carrying out the first, second or third aspect of the invention.

In all aspects of the invention, the metal structure may have a pipeline, for example an undersea pipeline of the type used to carry oil and gas. The metal structure may have a processing plant and / or a tree and / or a manifold.

[0028]   Hereinafter, embodiments of the present invention will be exemplarily described with reference to the accompanying drawings.

FIG. 1 shows a first anode monitoring system, which generally has a metallic structure consisting of a pipeline 1 having a plurality of anodes 2 and connected to a central office 4 via a link 3. Although only three are shown in FIG. 1, it will be appreciated that the pipeline system may have a large number of anodes 2.

Each anode 2 has an associated notch filter 5 connected in series between the respective anode 2 and the metal structure 1. Furthermore, each anode 2 has an associated transmitter 6 operating across the respective notch filter 5, acting as a signal generating means.

The metal structure 1 of the pipe is cased with an insulating coating 7. Therefore, the resistance between the metal structure and the surrounding medium is high. There is a capacitance between the surrounding medium with the coating 7 acting as a dielectric and the metal structure 1. However, unless the signal frequency is high enough for the capacitance to act, the loss from the metal structure 1 to the environment is almost exclusively through the anode 2. Therefore, the signal circuit S having respective signal channel S ₁ -S _n for each of the anode 2 is considered to be present. In each case, the signal path S _n has a metal structure 1, a respective anode 2, a link 3 and a respective return path through ground to the central office.

The notch filter 5 associated with each of the anodes 2 has a high impedance to the signal of the frequency generated by the associated transmitter 6, but a low impedance for the protection of the cathode that is applied to the metal structure 1. Selected to give to. This allows the cathode protection current to simply flow through the notch filter 5 when the respective anode 2 is present, allowing the cathode protection system to work effectively. However, when transmitting a signal using the transmitter 6, the metal structure 1 is such that the signal can be transmitted along with the metal structure 1 having an anode 2 which provides the transmitter 6 with a ground reference.
There is effectively an open circuit between and the respective anode 2.

On the other hand, if the respective anode 2 is not present, the transmitter 6 will not have a ground reference, or in another way the ground return path will be broken resulting in no signal being received at the central station 4. Let's do it. The same applies if the effectiveness of the anode 2 is compromised in other ways. Therefore, by searching for the expected lack of signal, it can be determined at the central station 4 that the anode 2 is not valid.

In particular embodiments, each transmitter 6 is configured to send a simple message at a random time during a selected time period, eg, once a week. The time it takes to send each message will be on the order of 5 seconds. Therefore,
In a system with about 50 anodes, the total transmission time would be 250 seconds each week. For this reason, the possibility that the two transmitters 6 simultaneously transmit is very low,
The probability of missing a signal from a functioning anode due to a collision is very low. In fact, a signal drop of more than one second is awaited before determining that the anode is not functioning. Thus, the chance of misdiagnosing a faulty anode would be reduced to about 1 / 1,000,000. Random signaling techniques are used because it is not practical to access each anode in real time.

Each message has various elements such as an address (8 bits), a protocol overhead (8 bits), an error check (16 bits), a battery status (8 bits), a measurement result (16 bits), and the like. is doing. The measurement results sent in the message may include the current value through each anode and the potential difference between the anode and the metal structure adjacent to the anode. These measurements can help in evaluating relevant metal structures and other anodes. In the alternative, each transmitter 6 can be configured to transmit on a separate frequency from each of the other transmitters and / or to send its own simple message to a particular anode 2. The central station 4 can then search for a plurality of different signals and can be configured to indicate exactly which anode is missing in the absence of a particular signal. In such an alternative, notch filter 5 is replaced with a bandstop filter selected to provide high impedance at each of the different frequencies used.

In another alternative, the notch filter 5 is replaced by another circuit element, for example an inductor having the necessary properties of providing high impedance to the transmitted signal and low impedance to the cathode protection current. It

FIG. 2 illustrates a second anode monitoring system that is similar to the first anode monitoring system shown in FIG. 1, but uses a different signaling technique. In the first anode monitoring system, it is necessary to have a power supply on each of the anodes 2 driving the respective transmitter 6. Power demands are high due to the losses inherent in the length of pipelines and the type of signaling used by the system. These power demands may be met by the use of one-shot batteries, which means that the system can function for a limited period of time before the batteries have to be replaced.

In the second monitoring system shown in FIG. 2, the power required to send a signal from each of the anodes can be provided at a location remote from the anodes. However, a power source may be provided at each anode to drive the electronics located at the anode. However, the power requirements of any such electronic device will be much less than that required to transmit a signal.

The second anode monitoring system generally comprises a metallic structure of the pipeline 1 having a plurality of anodes 2 in spaced apart positions and connected to a central office 4 via a link 3. Each of the anodes 2 is connected to the metal structure 1 via a bypass loop having a notch filter 8 and a switch 9. When the switch 9 opens, the metal structure 1
Only the conduction path between the and the respective anode 2 leads to the notch filter 8, but when the switch 9 is closed, there is a free conduction path. The tone detection circuit 13 is connected across each filter 8. Each switch 9 has an associated control means 10 arranged to open and close the switch 9 depending on the data transmitted. The switch 9 and the control means 10 operate as impedance changing means.

The central office 4 has a current source 11 which operates as a reference signal generating means, a first terminal connected to the metal structure 1 via the link 3, a second terminal which is grounded, and Has a voltage measuring means 12 connected to the first terminal of the current source 11 and the other terminal to the reference ground. The tone transmission circuit 14 is connected across the current source.

[0041]   The pipeline has an insulating layer 7 and is associated with each of the anodes 2, respectively.
Signal path S₁-S_nIt is considered that there is a signal circuit S having Each signal path S _n Has respective anode 2, metal structure 1, link 3 and respective ground return
It

Under normal circumstances, the signal path S _n is completed via the notch filter 8.
In this way, there is a current path from the metal structure 1 to the anode 2 that allows the cathode protection system to function because the notch filter 8 provides substantially no impedance to the cathode protection current. However, the notch filter is chosen to have a high impedance in the reference signal generated by the current source 11. If it is desired to send a signal from a particular anode 2, the reference signal is applied to the signal circuit and the control circuit 10 operates the respective switch 9 to encode the data to the signal circuit S. When all of the switches 9 are open, there is only a ground return path through the insulating layer and through the notch filter 8 to the second terminal of the current source 11. However, when the switch associated with a particular anode is closed, the respective notch filter 8 is bypassed, so that the effective impedance of the signal circuit S as a whole is considerably reduced with respect to the reference signal. Therefore, the effective impedance can be changed by opening and closing switches to encode the data to the signal circuit. The voltage measuring means 12 at the central office 4 is used to detect the resulting change in the potential difference between the first terminal of the current source 11 and ground when the switch 9 is opened and closed. The control means 10 associated with each anode 2 is used to encode the signal to the signal circuit S representing the respective anode. Therefore, the central office 4 can search for a specific signal in order to confirm the effectiveness of the specific anode 2. However, if the anode 2 is not present, opening and closing the switch 9 does not change the effective impedance of the signal circuit, and correspondingly no change in the potential difference is detected by the central station 4.

The transmission of signals from the anode is controlled as described below. The tone transmission circuit 14 transmits tones along the metal structure 1. The tones are detected by each of the tone detection circuits 13. Each tone detection circuit 13 is configured to send a trigger signal to the respective control means 10 after a predetermined period has elapsed. Once each control means 10 receives the trigger signal, it is disabled to encode the desired data into the metal structure. The predetermined time periods for each tone detection circuit 13 are different so that the signals are sent from each anode 2 at different times. It is known when the signal is received from each anode 2, so that the signal can be sought at the central office at these times. The lack of a particular signal means that the corresponding anode 2 is not valid.

In an alternative to each anode monitoring system, the central station 4 is capable of sending a particular command only to a particular anode for the respective transmitter 6 or control means 10 to operate as instructed. (Not shown). Typically, central office 4
Sends a series of individual signals, each of which causes the electronics associated with a particular anode to produce a signal that can subsequently be searched by the central station 4.

[Brief description of drawings]

FIG. 1 schematically illustrates a first anode monitoring system.

FIG. 2 schematically shows a second anode monitoring system.

[Procedure for Amendment] Submission for translation of Article 34 Amendment of Patent Cooperation Treaty

[Submission date] May 4, 2001 (2001.5.4)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Contents of correction]

[Claims]

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 2

[Correction method] Change

[Contents of correction]

[Fig. 2]

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0039

[Correction method] Change

[Contents of correction]

The second anode monitoring system generally comprises a metallic structure of the pipeline 1 having a plurality of anodes 2 in spaced apart positions and connected to a central office 4 via a link 3. Each of the anodes 2 is connected to the metal structure 1 via a bypass loop having a notch filter 5 and a switch 9. When the switch 9 opens, the metal structure 1
Only the conduction path between the and the respective anodes 2 leads to the notch filter 5, but there is a free conduction path when the switch 9 is closed. The tone detection circuit 13 is connected across each filter 5. Each switch 9 has an associated control means 10 arranged to open and close the switch 9 depending on the data transmitted. The switch 9 and the control means 10 operate as impedance changing means.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0042

[Correction method] Change

[Contents of correction]

Under normal circumstances, the signal path S _n is completed via the notch filter 8.
In this way, there is a current path from the metal structure 1 to the anode 2 that allows the cathode protection system to function because the notch filter 5 does not present a substantial impedance to the cathode protection current. However, the notch filter is chosen to have a high impedance in the reference signal generated by the current source 11. If it is desired to send a signal from a particular anode 2, the reference signal is applied to the signal circuit and the control circuit 10 operates the respective switch 9 to encode the data to the signal circuit S. When all of the switches 9 are open, there is only a ground return path through the insulating layer and through the notch filter 5 to the second terminal of the current source 11. However, when the switch associated with a particular anode is closed, the respective notch filter 5 is bypassed, so that the effective impedance of the signal circuit S as a whole is considerably reduced with respect to the reference signal. Therefore, the effective impedance can be changed by opening and closing switches to encode the data to the signal circuit. The voltage measuring means 12 at the central office 4 is used to detect the resulting change in the potential difference between the first terminal of the current source 11 and ground when the switch 9 is opened and closed. The control means 10 associated with each anode 2 is used to encode the signal to the signal circuit S representing the respective anode. Therefore, the central office 4 can search for a specific signal in order to confirm the effectiveness of the specific anode 2. However, if the anode 2 is not present, opening and closing the switch 9 does not change the effective impedance of the signal circuit, and correspondingly no change in the potential difference is detected at the central station 4.

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Claims (17)

[Claims] 1. An anode monitoring system for monitoring the integrity of an anode provided to a metal structure for cathode protection, the signal comprising at least one signal communication path having a metal structure and a selected anode. A circuit, whereby the characteristics of the signal circuit depend on the effectiveness of the selected anode, signal generating means for generating a signal and adding it to the signal circuit, and a signal of the signal circuit. A central office for monitoring and thereby determining if the selected anode is valid. 2. The signal generating means is configured to add a signal representing the validity of the selected anode to the signal circuit when the selected anode is valid. Anode monitoring system as described. 3. The anode monitoring system according to claim 1, wherein the signal generating unit is arranged in the selected anode. 4. The anode monitoring system according to any one of the preceding claims, wherein the arrangement is such that the lack or defect of the selected anode is made detectable by the lack of the expected signal. 5. The signal circuit according to claim 1, wherein the signal circuit has a return path through ground, and the selected anode, when available, provides a conductive path from the metal structure to ground. Anode monitoring system. 6. An anode monitoring system according to any one of the preceding claims, wherein the signal circuit comprises impedance means provided in series between the selected anode and the metal structure. 7. The impedance means is configured to provide a high impedance to the time-varying signal within one or more selected range of frequencies and a low impedance to the signal outside of the selected range. 6. The anode monitoring system according to 6. 8. The anode monitoring system of claim 7, wherein the impedance means is configured such that the real part of the impedance is substantially zero. 9. A transmission means and / or a reception means connected across said impedance means and arranged to transmit and / or receive a signal across said impedance means. The anode monitoring system according to claim 1. 10. The signal generating means is a reference signal generating means configured to add a reference signal to the signal circuit, and an effective impedance for changing the effective impedance of the signal circuit according to transmitted data. Changing means, the reference signal generating means is arranged at a position separated from the selected anode, and the impedance changing means is arranged adjacent to the selected anode. The anode monitoring system according to any one of claims. 11. A predecessor having a plurality of signal communication paths each including the metal structure and a respective anode configured to generate a signal associated with each anode at different randomly determined times. An anode monitoring system according to any one of the preceding claims. 12. An anode monitoring method for monitoring an intact state of an anode provided on a metal structure for protecting a cathode, the method comprising: generating a signal and adding the signal to a signal circuit. A signal circuit having at least one signal communication path having the metal structure and a selected anode, whereby the characteristics of the signal circuit depend on the effectiveness of the selected anode; Monitoring a signal on a signal circuit and thereby determining whether the selected anode is valid. 13. A metal structure having a transmitting means, a receiving means, and a metal structure, which is originally for a different purpose, but operates as a signal communication path between the transmitting means and the receiving means in use. A data transmission system, wherein the structure comprises at least one anode provided for protection of said cathode, and impedance means is arranged in series between said metal structure and said anode. 14. The impedance means is configured to have a high impedance for the time-varying signal within one or more selected range of frequencies and a low impedance for the signal outside the selected range. 13. The data transmission system according to item 13. 15. A data transmission system according to claim 13 or 14, wherein the transmitting means and / or the receiving means are connected across the impedance means. 16. A device used in a metal structure of the method or system of any preceding claim. 17. An anode configuration used in the method or system for monitoring an anode according to claim 1, wherein the sacrificial anode is configured to be mounted on a metal structure, and the anode. An impedance means having one terminal connected to and another terminal configured to be connected to the metal structure, and connected across the impedance means for transmitting and / or receiving signals An anode configuration having an electronics module.