Arrangement and method for detecting damage to an inner coating of a container

Abstract

Arrangement and method for detecting damage to an inner coating of a container is provided. The arrangement has been devised which is influenced by damage to the inner coating and/or actuation of plant parts (shut-off valves) and/or by electrical changes in the current paths. This is accomplished such that the latter generates a reproducible signal excursion which can be assigned to the respective activity and therefore to the corresponding parts of the plant, such as a container. Thus, by means of the measuring arrangement, both slowly changing values, which arise as a function of process-induced slowly changing process parameters, such as temperature, concentration, conductivity, and other gradually occurring damage to an inner coating, and also short-term significant changes of values are detected, which are brought about e.g. by pumping operations or by connecting together plant parts, which influence the electrical properties of the system. The detected signal excursion is interpreted.

Claims

1. An arrangement for detecting damage at an inner coating of a container, wherein the container (1) comprises a container wall made of a conductive material, which is connected to a lightning protection or equipotential bonding (2) and wherein a first electrode for a first measuring point (9) is arranged in the container (1) or in a pipe (5) leading into the container (1), which first measuring point (9) is connected to a measuring arrangement, wherein the pipe (5) and the container (1) are at least partially filled with an electrically conductive process liquid, wherein the container wall has an insulating inner coating made of plastic, and wherein the container (1) is connected to a plant part (3) remote from the container (1) via a first pipe (5) made of an electrically non-conductive material, a second measuring point (10) is arranged on the plant part (3) remote from the container (1), the first measuring point (9, 9b) is arranged on a first electrode of a plastic intermediate flange disk (22, 22b) or on an electrode in the container (1), and the measuring arrangement is connected for electrical conduction with the first measuring point (9, 9b) and the equipotential bonding (2) or with second measuring point (10).

2. The arrangement according to claim 1, wherein the measuring arrangement comprises a voltage source (13) and a voltmeter (14), wherein the voltage source (13) is connected with a first terminal to the first measuring point (9b) and with a second terminal to the equipotential bonding (2) or to the second measuring point (10), and wherein the voltmeter (14) is directly connected to the first measuring point (9b) and directly or via a capacitance with the equipotential bonding (2) or the second measuring point (10).

3. The arrangement according to claim 1, wherein the measuring arrangement is a grounding resistance tester (12) or an ISO meter (18).

4. An arrangement for detecting damage to an inner coating of a container, wherein the container (1) comprises a container wall made of a conductive material, which is connected to a lightning protection or equipotential bonding (2) and wherein a first electrode for a first measuring point (9) is arranged in the container (1) or in a pipe (5) leading into the container (1), which first measuring point (9) is connected to a measuring arrangement, wherein the pipe (5) and the container (1) are at least partially filled with an electrically conductive process liquid, and wherein the container wall has an insulating inner coating made of plastic, wherein the measuring arrangement comprises a first controllable voltage source (19), which is connected with its first terminal via an ammeter (21) to the first measuring point (9, 9b) in a plastic intermediate flange disk (22b) and with its second terminal to the equipotential bonding (2), a second controllable voltage source (20), which is connected with its first terminal to a first electrode (9) of a further plastic intermediate flange disk (22) arranged in a second pipe (6) or in a third pipe (7) and with its second terminal to the equipotential bonding (2), and a voltmeter (14), which is connected between a second measuring point (10) of the further plastic intermediate flange disk (22) and a second measuring point (10b) of the plastic intermediate flange disk (22b).

5. The arrangement according to claim 1, wherein the measuring arrangement is connected to two first measuring points (9a, 9b) of two containers (1a, 1b) and/or to the second measuring point (10) and a third measuring point (11), which is arranged on a second plant part (4).

6. The arrangement according to claim 1, wherein the first plant part (3) and/or the second plant part (4) is a heat exchanger.

7. The arrangement according to claim 2, wherein the voltage source (13) is an AC voltage source or a pulsed DC voltage source.

8. The arrangement according to claim 4, wherein the first voltage source (19) and/or the second voltage source (20) is a DC voltage source or a controllable AC voltage source or a frequency-synchronous controllable AC voltage source.

9. A method for detecting damage to an inner coating of a container, providing a container (1) connected to a lightning protection or equipotential bonding (2) with a first electrode for a first measuring point (9) arranged in the container (1) or in a pipe (5) before the container (1), at least partially filling the pipe (5) and the container (1) with an electrically conductive process liquid, providing a container wall of the container (1) with an insulating inner coating made of plastic, providing a first plant part (3) with a second measuring point (10) connected with remote from the container (1, 1b) via a first pipe (5, 5b), and detecting the damage to the inner coating of the container (1, 1b) by a measuring arrangement electrically connected to the first measuring point (9, 9b) and the equipotential bonding (2) or to the second measuring point (10), and providing the first measuring point (9, 9b) on an electrode of a plastic intermediate flange disk (22, 22b), which has one or more electrodes in contact with the process liquid.

10. The method according to claim 9, wherein the measuring arrangement performs an insulation measurement or a resistance measurement for the detection of damage to the inner coating of the container (1).

11. A method for detecting damage to an inner coating of a container, wherein a container (1) connected to a lightning protection or equipotential bonding (2) with a first electrode arranged in the container (1) or in a pipe (5) before the container (1) is provided for a first measuring point (9), wherein the pipe (5) and the container (1) are at least partially filled with an electrically conductive process liquid, and wherein a container wall of the container (1) is provided with an insulating inner coating made of plastic, wherein the measuring arrangement performs a voltage measurement, wherein a first controllable voltage source (19) is provided, which is connected with its first terminal via an ammeter (21) to the first measuring point (9, 9b), which is provided by means of a first electrode of the plastic intermediate flange disk (22, 22b) and which is connected with its second terminal to the equipotential bonding (2), and a second controllable voltage source (20) is provided, which is connected with its first terminal to a further first measuring point (9) provided on a further plastic intermediate flange disk (22), and wherein the voltage measurement is performed with a voltmeter (14) between a second measuring point (10) of the further plastic intermediate flange disk (22) and a second measuring point (10b) of the plastic intermediate flange disk (22b).

12. The method according to claim 9, wherein upon detection of damage to an inner coating of a container (1), a digital or analog error signal signaling the damage is outputted.

13. The method according to claim 9, wherein for detecting damage to the inner coating of the container (1), a measurement is performed with the measuring arrangement between at least two interconnected first measuring points (9a, 9b) of two containers (1a, 1b) and the second measuring point (10) and/or a third measuring point (11), which is provided on a second plant part (4).

Description

BRIEF DESCRIPTION OR THE DRAWINGS

(1) Further details, features and advantages of embodiments of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings, which show in:

(2) FIG. 1: a schematic diagram of a plant with multiple containers to be monitored,

(3) FIG. 2: a first embodiment of the invention (variant 1, alternative 1, grounding measurement) for detecting damage to the inner coating of containers,

(4) FIG. 3: a second embodiment of the invention (variant 1, alternative 2; ISOMETER) for detecting damage to the inner coating of containers, and

(5) FIG. 4: a third embodiment of the invention (variant 2, alternative 3; determination of the flow of current through the defective container) for detecting damage to the inner coating of containers.

DETAILED DESCRIPTION OF THE INVENTION

(6) FIG. 1 shows in a schematic diagram a plant with the essential elements for the present invention. The diagram shows four containers 1a, 1b, 1c and 1d, each having a lightning protection or equipotential bonding 2a, 2b, 2c and 2d, via which they are connected to a ground potential. The fluid, which is also referred to as a conductive process liquid, is stored in these containers 1a, 1b, 1c and 1d.

(7) The system further includes two parts 3 and 4 of the plant, which are connected via pipes 5 with the associated containers 1. The first plant part 3 is connected via the pipe 5a to the first container 1a and via the pipe 5b to the second container 1b. The second plant part 4 is connected via the pipe 5c to the third container 1c and via the pipe 5d to the fourth container 1d. Electrically non-conductive plastic pipes are typically used for the pipes 5a, 5b, 5c and 5d.

(8) Such plant parts 3 and 4 may, for example, be heat exchangers. Other elements or assemblies, which are connected to the container 1 via a pipe 5 and through which the fluid flows, can also be understood to represent plant parts 3 and 4. Hereinafter, by way of example, a heat exchanger is used as plant part 3 and 4.

(9) FIG. 1 also shows a second pipe 6 arranged between the first and the second heat exchangers 3 and 4. The exemplary second heat exchanger 4 is shown to be connected to a third pipe 7 for supplying a cooling medium. The first heat exchanger 3 can also have such a connection, which is not shown in FIG. 1.

(10) A resistance 8 is depicted in the region of the third pipe 7, which is a function of the electrical conductivity of the fluid flowing through the pipe 7. This resistance is shown here by way of example only. Such a resistor 8 has been omitted in the lines 5a, 5b, 5c and 5d, although it may also be present therein. The same applies to the pipe 6, if it is made of a non-conductive material.

(11) With reference to the third pipe 7, it is shown by way of the marked resistor 8 that the second heat exchanger 4, even if this heat exchanger 4 itself does not have a lightning protection or equipotential bonding, is connected with its resistance 8 at least via a equipotential bonding 2e to a ground potential via the cooling water flowing in the pipe 7.

(12) For protection against the aggressive process fluid stored therein, the containers 1a, 1b, 1c and 1d are provided with an inner coating made of plastic, the functionality of which is to be monitored by the present invention.

(13) A first measuring point 9a, 9b, 9c and 9d is provided inside each container 1a, 1b, 1c and 1d or in each line 5a, 5b, 5c or 5d leading to a container 1a, 1b, 1c and 1d which may be embodied as a contact in the electrically conducting process liquid (immersion probe). The embodiment with an immersion probe in the container 1a is shown in FIG. 1 by a dash-dash line. Alternatively, the measuring points 9a, 9b, 9c and 9d may be arranged as probes in the line 5a, 5b, 5c or 5d proximate to the container 1a, 1b, 1c or 1d to be monitored. These probes are, for example, designed as a plastic intermediate flange disk 22 with, for example, two integrated tantalum probe heads in contact with the fluid and installed at a junction between a plastic tube and the flange of the internally coated steel container. In this embodiment, the measuring point 9a, 9b, 9c or 9d is located directly on the container 1a, 1b, 1c or 1d. The electrodes forming the measuring points 9a, 9b, 9c, 9d can be arranged, for example, opposite one another and electrically separated from one another in the plastic intermediate flange disk 22. Furthermore, for the arrangement according to FIG. 2 and/or FIG. 3, the measuring points 9a to 9d, which are not connected to the measuring arrangement, can be set to a potential. Alternatively, it is also possible to interconnect or short-circuit the respectively opposite electrodes, for example 9b to 10b, to increase the electrode surface on, for example, the plastic intermediate flange disk 22b used for the measurement.

(14) A second measuring point 10 is provided at the first heat exchanger 3 and a third measuring point 11 is provided on the second heat exchanger 4. In addition, a further second measuring point 10b may be provided on the second plastic intermediate flange disk 22b.

(15) All measuring points 9, 10 and 11 are designed so that they can be connected via an unillustrated line with a centrally arranged measuring device. For example, leads from the measuring points 9, 10 and 11 lead to a central office, in which the system is regularly monitored and controlled.

(16) The plant illustrated in FIG. 1 shows only the components and compounds essential for the explanation of invention. Of course, such plant may have further modules, plant parts and pipes in order to fully fulfill their function.

(17) FIG. 2 shows the plant already known from FIG. 1 with its already described components and connections. FIG. 2 shows a first embodiment of the invention for detecting damage to the inner coating of a container 1a, 1b, 1c or 1d in the first alternative of the first variant with a grounding measuring device.

(18) For this purpose, a resistance measuring device is used, which can be for example a grounding resistance tester (e.g. CHAUVIN ARNOUX C.A 6460) or an ISOMETER (e.g. BENDER iso 685), which is equipped with a voltage source 13, a voltmeter 14 or components for calculating, displaying, possibly also storing the temporal course of the resistance of the individual resistance measurements between the measuring points 9b, or 9a, 9c or 9d, and equipotential bonding.

(19) The connection to the different measuring points can be suitably designed by inserting unillustrated switches into the test leads. For example, such switches can be used to connect the first terminal 15A and/or 15B of the grounding resistance tester 12 either to the first measuring point 9b or alternatively to the first measuring point 9a. The switches may be switched on and off, for example, under control by a central control or manually.

(20) Irrespective of whether a discontinuously measuring grounding resistance tester or a continuously measuring ISOMETER is used as measuring device 12 or as measuring device 18 in FIG. 3, the most important task in the choice of measuring points is to connect them in such a way that the measured resistance values in the GOOD state are within the measurement range limits of the measuring device 12 (18).

(21) While an ISOMETER in the GOOD state can measure several megohms, the measuring range of grounding resistance testers is at most a few kilo ohms.

(22) This means that ISOMETERN are better suited to measure directly between container-proximate measuring points, such as the measuring points 9a, 9b, 9c, 9d, and measuring points, which are close to ground potential, the equipotential bonding or the container wall.

(23) Grounding resistance testers 12 should therefore more likely between container-proximate measuring points 9a, 9b, 9c, 9d and measuring points which are located closer to the container 1a, 1b, 1c, 1d to be monitored, which can be, for example, the measuring points 10, 11, but also other measuring points 9.

(24) If it is not possible to use of commercially available grounding resistance testers or ISOMETER by appropriate selection of the measuring points and their location in the container system and the structural design of the electrodes contacting the process medium (surface size), then the second variant with the third alternative, which is shown in FIG. 4, can be used.

(25) In an example shown in FIG. 2, a grounding resistance tester 12, which can be designed, for example, as a three-terminal or four-terminal device, and which provides, for example, a pulsed measuring voltage is used. Alternatively, the components of the grounding resistance tester 12, which includes a voltage source 13 embodied as an AC voltage source or a pulsed DC voltage source, as well as a voltmeter 14, can be simulated in a circuit.

(26) It is intended to connect the terminals 15A and 15B of the grounding resistance tester 12 to the first measuring point 9b, i.e. to an electrode of the plastic intermediate flange plate 22b. These connection points are referred to as E and ES at the grounding device 12.

(27) The second connection 16 of the grounding resistance tester 12 is connected to equipotential bonding, as shown in the example of FIG. 2. This terminal 16 is also designated as H(Z).

(28) The third terminal 17 of the grounding resistance tester 12, which is also designated as S(Y), is likewise connected to a grounding point, a lightning protection or equipotential bonding.

(29) In an alternative, the second connection 16 and the third connection 17 may be connected for a measurement to the second measuring point 10 of the heat exchanger 3 or to the third measuring point 11 of the heat exchanger 4.

(30) For example, a commercially available 3-terminal or 4-terminal grounding resistance tester, as offered by the company Chauvin Arnoux, which has the described terminals 15A, 15B, 16 and 17, can be used. This grounding resistance tester operates with a pulsed measuring voltage, which is detected by the grounding resistance tester itself as its own measuring voltage.

(31) By means of the voltage source 13 (AC voltage source or pulsed DC voltage source), in the example a pulsed measuring voltage is applied as a so-called test voltage between the measuring point 9b and the equipotential bonding.

(32) When the inner coating of the connected container or containers 1a, 1b, 1 c or 1d is intact, a specific voltage value is determined with the voltmeter 14 and an associated value R for the insulation is displayed by the grounding resistance tester 12.

(33) The value R decreases in the event of damage to an inner coating of a container 1a, 1b, 1c or 1d. The reason for the decrease is a further current path, which extends from the first terminal 15A/15B, for example via the first measuring point 9b of the plastic intermediate flange disk 22b, the conductive fluid in the container 1b through the defective inner coating to the steel container itself and the potential equalization 2b. Although the absolute value for an intact inner coating of all containers 1a, 1b, 1c and 1d depends on the various plant components and on the currently process running in the plant, damage to the inner coating causes a noticeable perceptible drop of the displayed value.

(34) For example, the values for different plant conditions may be acquired and stored, thus allowing a comparison in the event that one or more inner coatings become defective.

(35) In addition detecting damage, it is also possible to isolate the damage in such a way that the associated container 1a, 1b, 1c or 1d can be determined. For this purpose, the first terminal 15A/15B of the measuring device 12 is successively connected to the first measuring point 9a, 9b, 9c and 9d, and the displayed value is observed while a valve attached to the inlet of the respective container 1a, 1b, 1c or 1d is closed and opened. Since closing a valve interrupts an electrically conductive fluid path, the displayed previously measured value changes significantly when the valve on the container 1a, 1b, 1c or 1d having the damaged inner coating is closed. Thus, the defective container 1a, 1b, 1c or 1d is located and can accordingly be removed from the ongoing process and/or repaired.

(36) FIG. 3 shows a second alternative of the first variant, wherein damage to an inner coating of a container 1a, 1b, 1c, 1d is detected with an ISO meter 18. In this embodiment, for example, the first terminals 15A and 15B of the ISO meter 18 are connected to a first electrode 9b of, for example, two electrodes disposed opposite each other in the plastic intermediate flange disk 22 and in communication with the fluid. The second terminal 16 and the third terminal 17 is connected to the equipotential bonding 2 as shown. Alternatively, the second port 16 and the third port 17 may be connected for the measurement to the second measuring point 10 of the heat exchanger 3 or to the third measuring point 11 of the heat exchanger 4.

(37) With this measuring arrangement, damage to an inner coating of a container can be determined by performing a first measurement of the resulting resistance R when a valve (fitting) disposed between the plastic intermediate flange disk 22b and the container 1b is in an open state. In addition, a second measurement of the resistance R is performed when the valve is in a closed state. In the event that the inner coating of the container 1b is defective, values are measured that clearly differ from each other, since closing of the valve causes an interruption of the current path via the conductive fluid. If there is no significant change in the measured resistance R in both cases, the inner coating of a container 1b is undamaged.

(38) FIG. 4 shows the second variant of the measuring arrangement and thus a third alternative of the invention. This second variant is again based on an already known design of the plant with four containers 1a, 1b, 1c and 1d, two heat exchangers 3 and 4 and the corresponding connecting pipes. The measuring points 9a, 9b, 9c, 9d necessary for detecting damage to an inner coating are also provided.

(39) The measuring arrangement includes a first voltage source 19, which preferably may be a controllable or non-controllable voltage source 19, for supplying a test voltage at one or more first measuring points 9a, 9b, 9c or 9d. Alternatively, the first voltage source 19 may be constructed as a DC voltage source or a frequency synchronous AC voltage source. Furthermore, an ammeter 21 is provided, which measures the current I supplied by the voltage source 19.

(40) In addition, a second controllable voltage source 20, designed as a DC voltage source or a frequency-synchronous AC voltage source, is provided which supplies, for example, a DC voltage or an AC voltage to a first measuring point 9 of a further plastic intermediate flange disk 22. The respective second electrodes 10 and 10b of the plastic intermediate flange disks 22 and 22b are connected to a voltmeter 14. Since the use of a conductive fluid is assumed in the present invention, a voltage is measured by the connected voltmeter 14. This measured voltage is regulated to a value of zero Volt by a corresponding change in the DC or AC voltage provided, for example, by the second voltage source 20.

(41) The further plastic intermediate flange disk 22 may for example be installed in a corresponding flange in the conduit 6 or the conduit 7. When the voltage at the voltmeter 14 is regulated to zero Volt, no current flows in this state in the illustrated measuring circuit of FIG. 4 via the line 5b. Likewise, when supplying the DC voltage or the AC voltage of the first voltage source 19 at all first measuring points 9a, 9b, 9c and 9d, regulating this voltage to zero Volt at the voltmeter 14 requires that no current flows in any of four lines 5a, 5b, 5c and 5d. The current flowing via the cooling water line 7 and the resistance 8 toward the equipotential bonding 2e is not important for the detection of damage. For example, in the event of damage to an inner coating of the container 1b, as shown in FIG. 4, a current flows from the first measuring point 9b via the conductive fluid in the container 1b to the equipotential bonding 2b, since this current flow due to damage to the non-conductive inner coating of container 2b can no longer be prevented.

(42) For example, the display of voltmeter 14 was regulated to a value of zero Volt. In this case, no current flows through the line 5b. However, if the ammeter 21 shows a current flow, this current canin the event of damageflow only through to the liquid present in the container 1b, the defective inner coating, the container wall to the equipotential bonding 2b.

(43) If several first measuring points 9a, 9b, 9c and 9d in several plastic intermediate flange disks 22a, 22b, 22c, 22d are simultaneously supplied by the voltage source 19, the container 1a, 1b, 1c or 1d, which has the damage to the inner coating, must still be identified after detecting a higher current on the ammeter 21 indicative of damage. In this case, the first measuring points 9a, 9b, 9c and 9d are switched on and off sequentially with switches not explicitly shown in FIG. 4. Based on the result, the container 1a, 1b, 1c or 1d causing the increased current flow is identified.

(44) In all variants of the detection of damage, a measured value characterizing the damage can be displayed and an error or alarm signal in an analogue or digital form can be outputted. In this way, the invention can be integrated into an existing central plant control.

(45) In summary, the following applies to the first variant both in the first alternative and in the second alternative of FIGS. 2 and 3.

(46) All electrodes having the same designation (9a, 9b, 9c, 9d) and all ground connections could each be connected to one potential. In this way, a single measuring device can be used to monitor several containers. In this case, the damaged tank(s) 1a, 1b, 1c, 1d can be identified in the presence of a bad signal as follows: 1. The mechanical closing/opening of the liquid column in a pipe to a measuring point or between a container without damage and a measuring point has no significant effect on the measuring signal. The same applies to the electrical disconnection/connection of the measuring line to a measuring point proximate to the container (container without damage). In the event of damage, both aforementioned activities lead to reproducible signal bumps. 2. If a current flow is detected from the vessel wall via the lightning conductor with a current probe, this is a sure sign of damage to the lining, since no current flows in the GOOD state.

(47) Substantially the same as for the first variant applies to the second variant in the third alternative, as shown in FIG. 4, provided that the further plastic intermediate flange plate 22 (without an additional letter) is connected to the two electrodes 9 and 10 (without an additional letter) is not placed at the same potential as the other plastic intermediate flange disks 22a, 22b, 22c, 22d and their electrodes 9a, 9b, 9c, 9d and 10b.

LIST OF REFERENCE SYMBOLS

(48) 1a-d container 2, 2a-e equipotential bonding/Lightning protection/grounding 3 first plant part/heat exchanger 4 second plant part/heat exchanger 5a-d first pipe 6 second pipe 7 third pipe 8 resistance 9, 9a-d first measuring point 10, 10b second measuring point 11 third measuring point 12 measuring device/grounding resistance tester 13 voltage source (AC voltage source or pulsed DC voltage source) 14 voltmeter 15A, 15B first terminal 16 second terminal 17 third terminal 18 ISO meter (resistance meter with voltage source, I and U measurement) 19 first controllable voltage source (DC voltage source or controllable AC voltage source or frequency-synchronous controllable AC voltage source) 20 second controllable voltage source (DC voltage source or controllable AC voltage source or frequency-synchronous controllable AC voltage source) 21 ammeter 22 plastic intermediate flange disk