Determining the deformation of a pressure vessel

Abstract

A method for determining pressure-induced deformation of a pressure device (10) is proposed, wherein the pressure device (10) comprises a device wall (11) and a waveguide (21) connected to the device wall (11), wherein the waveguide (21) is subjected to a high-frequency alternating voltage, the pressure device (10) is subjected to pressure causing deformation of the device wall (11) and the waveguide (21), a change in an electrical property of the waveguide (21) caused by the deformation is detected, and the presence and / or position of deformation of the device wall (11) is derived from the change in the electrical property. A corresponding pressure device (10) and means for carrying out the method are also proposed.

Description

[0001] The present disclosure relates to a method for determining a deformation of a pressure device, a pressure device and means for carrying out the proposed method. Background of the invention

[0002] The term "pressure equipment" includes, for example, containers, pipelines, safety equipment, and pressure-retaining equipment, as defined in the European Union's Pressure Equipment Directive 2014 / 68 / EU. For further definitions, which may also apply within the scope of this disclosure, reference can be made, for example, to Article 2 of the Pressure Equipment Directive. This disclosure may refer to all pressure equipment, including pressure equipment not covered by the Pressure Equipment Directive but falling within its respective definitions.

[0003] Pressure equipment is conventionally subjected to routine or event-driven inspections to prevent bursts, leaks, or pressure and gas losses, for example, due to material fatigue or accidental damage. During these inspections, critical areas of the pressure equipment are examined as necessary, for example, using suitable measuring instruments that can detect deformations and stresses with sufficient accuracy, or by methods such as ultrasound or X-rays.

[0004] There is a need for improvements in the determination of deformations in pressure equipment, overcoming the disadvantages of the state of the art and possibly opening up further areas of application or enabling statements. Disclosure of the invention

[0005] Against this background, a method for determining the deformation of a pressure device, a pressure device, and means for implementing the proposed method with the respective features of the independent claims are proposed. Embodiments are the subject of the dependent claims and the following description.

[0006] The proposed method serves to determine pressure-induced deformation of a pressure device, wherein the pressure device comprises a device wall and a waveguide connected to or deforming with the device wall, wherein the waveguide is subjected to a high-frequency alternating voltage, the pressure device is subjected to pressure causing deformation of the device wall and the waveguide, and a change in an electrical property of the waveguide caused by this deformation is detected. The presence and / or location of the deformation of the device wall is derived from this change in electrical property. Based on the presence and / or location of the deformation, certain conclusions can be drawn in various embodiments of the method, and in particular, appropriate measures can be taken.

[0007] The proposed method and its embodiments are based in particular on the understanding that a cost-effective, readily available, mature, and well-understood technology exists in the form of high-frequency waveguides capable of measuring in the single-digit micrometer range. This technology, especially through the use of ultra-high frequencies, as explained below, can detect deformations of a pressure vessel or its wall. The high-frequency waveguides can be mounted on or near the surface of the vessel wall and, due to their geometry, are very easy to integrate. At the ultra-high frequencies used, the corresponding waveguides require a very small size and can, for example, be manufactured from standard sheet steel.

[0008] Embodiments of the present method may, in particular, include a continuous, sectional, or point-like connection of the waveguide using known means, especially by welding, bonding, crimping, and the like. This can cause a deformation of the pressure device or its wall to also cause a corresponding deformation of the waveguide, or to be reflected in a deformation of the waveguide.

[0009] The waveguides used in the proposed method and its various configurations enable the realization of a robust, online-capable system, thus allowing continuous monitoring of pressure equipment rather than being limited to routine or event-driven inspections. This results in a safety and availability advantage for the pressure equipment in question.

[0010] The impedance and propagation velocity of a waveguide depend on its cross-section, which changes, for example, due to pressure-induced strain on the monitored pressure device, thus providing information about the device's safety. Damage caused by both external influences and fatigue stress is measurable. Due to its small dimensions, integration into and / or onto a device wall is possible.

[0011] In embodiments of the proposed method, the device wall has a cylindrical section, and the waveguide is connected to the device wall within this cylindrical section. Such embodiments offer particular manufacturing advantages, as the waveguide only needs to be adapted to the relatively simple geometric shape of a cylinder. At the same time, safety advantages arise because, for example in compressed gas cylinders or pressure tanks, the cylindrical sections between, for instance, dome-shaped end caps are particularly susceptible to damage simply because they have the largest surface area.

[0012] In certain configurations, the waveguide can have several sections arranged parallel to each other and extending parallel to a cylinder axis of the cylindrical section of the device wall. This allows essentially the entire device wall of the pressure vessel within the cylindrical section to be monitored in close spatial segments using the waveguide, resulting in further improved measurement without significant gaps.

[0013] In particular, the waveguide can, in appropriate configurations, have arc-shaped sections that connect the parallel sections in such a way that the waveguide has a meandering shape. In this way, a very long waveguide can be constructed from simple, for example prefabricated, subunits.

[0014] In appropriate configurations, the electrical properties of the waveguide can be adjusted by changing the lateral offset between the parallel sections and the arc-shaped sections. A waveguide designed accordingly is therefore easily calibrated.

[0015] In embodiments of the proposed method, the waveguide has a rectangular cross-section with a first dimension in the range of 0.05 to 2 mm, particularly from 1 to 1.8 mm, for example approximately 1.6 mm, and a second dimension perpendicular to the first dimension in the range of 0.1 to 0.8 times the first dimension. Such a waveguide can be easily integrated into or mounted on a device wall without significantly increasing the size of the pressure vessel. Manufacturing is simple and can be carried out, for example, as mentioned, using standard sheet metal.

[0016] In certain embodiments of the method, the high-frequency alternating voltage can have a frequency of 100 GHz to 1 THz and / or the electrical property can be an impedance and / or propagation speed. The aforementioned high and ultra-high frequencies enable the small dimensions, and the aforementioned electrical properties are particularly easy to detect.

[0017] In various embodiments of the proposed method, the pressure device can be a pressure vessel designed to store a gas under pressure, for example, a compressed gas cylinder for industrial purposes, a corresponding pressure tank, or a breathing gas cylinder for divers or firefighters. The proposed method eliminates the need for decommissioning for inspection. Instead, the pressure device can be continuously monitored during operation.

[0018] In further embodiments of the proposed method, the pressure device can also be a hydraulic cylinder, and the method can be used to detect the position of a hydraulic piston within the hydraulic cylinder. It is known that the position of a hydraulic piston can be determined from a deformation of the hydraulic cylinder. The proposed method and its embodiments make such position determination particularly simple and reliable.

[0019] The proposed pressure device, which can be designed, for example, in the manner just mentioned, is configured to detect pressure-induced deformation of the pressure device, wherein the pressure device has a device wall and a waveguide connected to the device wall and is configured to apply a high-frequency alternating voltage to the waveguide, to apply pressure to the pressure device causing deformation of the device wall and the waveguide, to detect a change in an electrical property of the waveguide caused by the deformation, and to derive from the change in the electrical property the presence and / or position of the deformation of the device wall.

[0020] For further features and configurations of such a pressure device and preferred embodiments thereof, reference is expressly made to the above explanations regarding the method according to the invention and its respective advantageous configurations. Advantageously, such a pressure device is configured to carry out a method as described in its various configurations.

[0021] The proposed computing unit, which can be assigned to a printing device, for example, is designed, particularly in terms of programming, to carry out a procedure as previously explained in different configurations.

[0022] Implementing a proposed method as a computer program or computer program product with program code to execute all process steps is also advantageous, as this incurs particularly low costs, especially if an executing control unit is already available for other tasks. Suitable data carriers for providing the computer program include magnetic, optical, and electrical storage media, such as hard drives, flash memory, EEPROMs, DVDs, etc. Downloading a program via computer networks (Internet, intranet, etc.) is also possible.

[0023] The present invention is explained in more detail below with reference to the accompanying drawings, which illustrate embodiments of the measures proposed here. Figures

[0024] The embodiments are described below purely as examples with reference to the attached drawing, whereby Fig. 1. A pressure device with a measuring arrangement is illustrated; Fig. 2 the measuring arrangement according to Fig. 1 further illustrated; Fig. 3 Details of a measurement setup according to Fig. 1 illustrates; Fig. 4 illustrates a hydraulic cylinder with a measuring arrangement; Fig. 5 illustrates a measurement signal of a measurement setup; Fig. 6 further illustrates a measurement signal of a measurement setup; Fig. 7a and Fig. 7b Illustrate cross-sections through linear guide rails; Fig. Figure 8 illustrates a cross-section through a linear guide rail; and Fig. Figure 9 illustrates a system consisting of a shaft and a ball bushing. Designs

[0025] The embodiments described below are provided solely to assist the reader in understanding the claimed and previously explained features. They represent only representative examples and are not intended to be considered exhaustive or limiting with regard to the features of the embodiments described herein. It is understood that the advantages, embodiments, examples, functions, features, structures, and / or other aspects described above and below are not to be considered limitations on the scope of the invention as defined in the claims, or limitations on equivalents to the claims, and that other embodiments may be used and modifications made without deviating from the scope of the claimed invention.

[0026] Different embodiments may include, feature, consist of, or essentially consist of further advantageous combinations of the described elements, components, features, parts, steps, means, etc., even if such combinations are not specifically described herein. Furthermore, the disclosure may include other inventions that are not currently claimed but may be claimed in the future, particularly if they are within the scope of the independent claims.

[0027] Explanations relating to devices, apparatus, arrangements, systems, etc., according to the embodiments proposed herein may also apply to procedures, processes, methods, etc., according to other embodiments, and vice versa. Identical, functionally equivalent, structurally identical or comparable elements, process steps, etc., may be indicated with identical reference numerals.

[0028] The following explanations and definitions, which concern some of the fundamentals of the designs proposed here, may apply to all or part of the designs presented here, and the explanation of certain aspects in connection with only one part or one of the designs should not be understood to mean that these aspects cannot also be implemented with other or all designs, insofar as technically possible and sensible.

[0029] The conjunction "and / or," when used before the last item in a list, should be understood in this context to mean that all previously mentioned items in the list can be combined with each other in any way. In other words, "A, B and / or C" means "A and / or B and / or C" or "at least one of the elements A, B, and C in any combination."

[0030] The proposed designs are based on the well-known fact in high-frequency technology that the dimensions of a waveguide are directly related to the propagation speed within the waveguide. This fact, in particular, is used here to determine the extent and / or location of a deformation in a pressure vessel or its wall. The proposed designs benefit especially from the current technological leap in high-frequency technology to very high frequencies in the range of 100 GHz to 1 THz. Consequently, the number of system reference documents for frequency approvals and already granted frequency allocations of this type is increasing worldwide.

[0031] In principle, the extent of deformation could also be determined using known strain gauges. However, there is currently no known way to use strain gauges in a cost-effective and sufficiently robust manner. Another solution, which is generally applicable, is the use of fiber optic sensors, but these are currently hardly cost-effective.

[0032] A first group of proposed solutions involves determining the extent of deformation in pressure equipment as part of a safety inspection. As already mentioned, this safety inspection is conventionally carried out at intervals or on specific occasions, for example, when damage is suspected. For instance, compressed air cylinders used by fire departments are regularly visually inspected and, if damage is suspected, are tested by an inspection organization. An integrated testing procedure does not currently exist. A robust, online-capable monitoring system is not yet feasible. The proposed solutions address this issue.

[0033] The proposed designs utilize thin waveguides to implement robust, online-capable deformation detection systems. The waveguide's impedance and propagation velocity depend on its cross-section, which changes due to pressure-induced strain on the monitored pressure vessel, thus providing information about the vessel's safety. Damage caused by external forces is measurable. Integration into and / or onto the vessel wall of pressure vessels is conceivable. These designs can be used with all types of pressure vessels in stationary and mobile systems. In certain cases, a waveguide itself may be damaged. In such a case, damage to the entire pressure vessel must be assumed. Multiple, redundantly arranged waveguides or corresponding measurement setups can also be used, allowing for continued measurement even if one waveguide or measurement setup is damaged.

[0034] In Fig. Figure 1 illustrates a pressure device 10 with a device wall 11. In the illustrated example, the device wall has a cylindrical section 12 and adjoining end caps 13, for example, dome-shaped, or other wall structures, which are only indicated by dashed lines in the illustrated example for clarity and generality. The pressure device 10 can, for example, be designed as a breathing gas cylinder or gas pressure tank, or serve any other purpose.

[0035] In the example shown, an external measuring arrangement 20 is connected to the inner device wall 11, which has a Fig. 1 includes a non-visible waveguide. The waveguide is connected to a sensor 22, which in particular has suitable high-frequency technology and is connected via sensor lines (not shown) to a control unit 30 (illustrated in a highly simplified manner).

[0036] In a specific embodiment, the cylindrical section, and thus a part of the pressure vessel 10, can be designed as a round tube. Generally, however, the shape of a pressure vessel 10 can be arbitrary, as long as it can contain or be connected to a waveguide that accommodates the deformation of the pressure vessel or a part thereof, in this case, by its change in cross-section. In the field of structural engineering, such components are also referred to as "deformation-fit" connected. For this purpose, a section-by-section or continuous, and in particular a material-bonded, connection between the pressure vessel and the waveguide is required. This can be achieved, for example, by welding, soldering, bonding, or other joining techniques.

[0037] In the example illustrated here, the diameter of the pressure device 10 or the cylindrical section 12 can, for example, be 100 mm. The measuring arrangement 20 can, for example, include an outer cover of, for example, 1 mm and a 3 mm thick waveguide layer.

[0038] The sensor 22 of the measuring arrangement 20 can, for example, have external dimensions of 40 × 40 × 40 mm, thus being comparable in size to radar sensors used in the automotive sector. Smaller dimensions are also possible, but space must be provided for a connector for communication and power supply or a radio interface with a battery. The sensor 22 contains a high-frequency component with a structure and connection technology that can also be similar to that of radar sensors used in the automotive sector. The connected waveguide, which, as in Fig. The maximum waveguide cross-section shown in Figure 2 is 220 mm, but this is not a limitation. Thicker, thinner, longer, or shorter waveguides can also be used, as high-frequency chips are available from 60 GHz (3 mm waveguide cross-section) up to well over 600 GHz. The power requirement on the high-frequency side can be less than 1 mW, as the sensor element has very low losses (these depend on the geometry and material). Any evaluation method can be used.

[0039] Fig. Figure 2 illustrates details of a measuring arrangement 20 as proposed in embodiments. The measuring arrangement 20 comprises a meandering waveguide 21, which has several sections 23 arranged parallel to each other and extending parallel to the waveguide. Fig. 2. Section of the cylinder axis of the cylindrical section 12 of the device wall 11, which is not shown separately for the sake of clarity (see also Fig. 1) extend. The parallel sections 23 of the waveguide 21 are in particular arranged equidistantly around the circumference of the cylindrical section, wherein, for example, 10 to 100, 20 to 80 or 30 to 50 parallel sections may be provided.

[0040] The waveguide 21 points in the Fig. 2. In the illustrated embodiment, further arc-shaped sections 24 are shown, which connect the parallel sections 23 in a suitable manner and thus provide the meandering shape of the waveguide 21 in the illustrated embodiment.

[0041] As not specifically illustrated, a connection at one end of the waveguide 21 can extend out of the cover of the measuring arrangement 20 and into the sensor 22.

[0042] This is particularly possible with purely reflective measuring arrangements 20. Connections at multiple points, for example at both ends, of the waveguide 21 are also possible in other configurations.

[0043] As in Fig. Figure 3 illustrates an enlarged section from Fig. Figure 2 shows that a deliberate offset can be provided between the parallel sections 23 and the arc-shaped sections 24 of the waveguide 21, for example during manufacturing, as shown in Fig. 3 is designated as 25, where the electrical properties of the waveguide 21 are adjustable by this lateral offset 25 and the waveguide 21 can be calibrated in this way. Temperature compensation in connection with a risk classification scheme is also possible.

[0044] By using the waveguide 21 or a corresponding measuring arrangement 20, damage to a pressure vessel 10 caused by both external influences and fatigue stress can be measured. Continuous testing of the pressure vessel 10 is thus possible at any time. The assessment of the pressure vessel 10, as well as of any vessel walls 11 or areas 12 of vessel walls 11, is significantly improved, since data is now available as a time series and the damage can be localized. In direct comparison to fiber optic sensors, a waveguide system can be considered a more cost-effective alternative.

[0045] External influences on the pressure vessel 10 can also be detected using the measuring arrangement 20 with a waveguide 21 for strain measurement, either through continuous monitoring or inspection within the framework of today's standard test cycles for pressure vessels. In this way, it is possible to use higher pressures than usual, such as 500 bar, in corresponding pressure vessels 10, thus maintaining, for example, the same operating time for breathing gas cylinders with a smaller cylinder volume. A breathing apparatus technician can then, in addition to the usual visual inspection, also better assess the cylinder using this new waveguide sensor for strain measurement.

[0046] The deformation behavior of a device wall 11 of a pressure vessel 10 is highly characteristic, so much so that it can be described as a fingerprint. As a result of external loads or environmental influences over time, such as temperature fluctuations, filling and unloading processes, or stresses caused by misuse or accidents (rockfall, etc.), damage accumulates gradually. The damage to the material directly influences the deformation behavior of the device wall 11 of the pressure vessel 10, which can be measured as a deviation from the initial deformation behavior, i.e., as a change in the fingerprint. This allows for a determination of the condition of the device wall 11 of the pressure vessel 10.

[0047] The expansion and contraction, as well as external influences on a tank above the filling pressure, can be observed over time during tank filling and emptying processes and during storage. For this purpose, the internal pressure of the pressure vessel 10 and the temperature at a specific point can be monitored. Based on manufacturer tests using the waveguide sensor for strain measurement, conclusions can later be drawn about the condition of the pressure vessel 10 in the field.

[0048] Examples of measurement results in the pressure device 10 can essentially correspond to those obtained in Fig. 5 and Fig. 6 are illustrated.

[0049] Another application of the proposed embodiments is the position determination of a hydraulic piston within a hydraulic cylinder or cylinder tube, which in this case constitutes the pressure device. Position determination can be achieved based on an evaluation of the bulging of the hydraulic cylinder, as an alternative to strain gauges. The waveguide cross-section is directly coupled to the waveguide propagation velocity. The waveguide bulges radially under pressure. In corresponding embodiments, very high frequencies from 122 GHz and very small, rectangular waveguides with a diameter of less than 1.6 mm can be used. A piston diameter can range, for example, from 40 to 320 mm, and the piston rod cross-section from 22 to 220 mm. A stroke length can be, for example, up to 6 m. These dimensions are purely exemplary and do not limit the invention.

[0050] In Fig. 4 is a pressure device of a corresponding type, comprising a hydraulic cylinder 51 with a hydraulic piston 52 on a piston rod 53, designated by 50. On or in a device wall, i.e., the hydraulic cylinder 51, is a measuring arrangement 20 with a waveguide 21 in the Fig. 1 and Fig. 2 as explained above, for example comprising 71 parallel sections 23 with an angular offset of 5° with respect to a central axis of the hydraulic cylinder 51.

[0051] In Fig. Figure 5 illustrates in the form of a diagram 500 results of three-dimensional electromagnetic field simulations in the printing device 50, with frequencies in GHz on the horizontal axis versus the magnitude of the input fidelity parameter S 11 illustrated in linear units of the waveguide on the vertical axis. Fig. Figure 6 is an enlarged representation. The four frequency responses shown correspond to different radial strains r. d of the pressure device and thus the deformation of the waveguide.

[0052] Fig. Figure 6 illustrates in the form of a diagram 600 the change in the phase position of the transmission scattering parameter S21 in linear units on the vertical axis in "degrees phase angle" and frequencies in GHz on the horizontal axis over the four different radial strains rd of the pressure device.

[0053] Position determination on a linear system or linear actuator can also be achieved using appropriate waveguide technology. Such systems are well-known in the field and described in relevant technical books, for example, the applicant's "Handbook of Linear Technology," published in 2006, ISBN 978-3-9816398-5-8. Reference can be made, for example, to Chapter 3, "Profile Rail Guides," in particular 3.1.1.1, "Construction of a Profile Rail Guide," and Chapter 4, "Ball Bushing Guides," in particular 4.1.1.1, "Construction of a Ball Bushing."

[0054] In general, such linear systems have elements that can be displaced relative to each other, a first element of which has one or more bearing balls or other rolling elements that roll or roll along a rolling path of the second element, for example a corresponding groove or raceway of a profile or a shaft guided in a ball bushing.

[0055] In the Fig. 7a and Fig. Figure 7b shows cross-sections through a guide rail of a linear system, for example designed as a ball rail.

[0056] Fig. Figure 7a illustrates a conventionally designed guide rail 710, such as that sold by the applicant as part of a corresponding system. Details can be found in the applicant's document no. R999000466, "Integrated Measuring System IMS for Ball and Roller Guides". A ball or roller carriage, not shown separately for clarity, can be slidably mounted on the guide rail 710, for example with an adapter plate. Likewise, a measuring head, in particular including sensors, electronics, connecting cables and connectors, can be mounted on the guide rail. This can, for example, be mounted on the ball or roller carriage.

[0057] The guide rail 710 can have a one- or multi-part base body 701, for example made of aluminum. Lateral tracks 702 can be fitted as shown in Fig. Figure 7A, enlarged and illustrated with dashed lines, shows that dimensional embodiments 703 may be integrated, which may include, for example, integrated reference marks or an absolute code band, thereby creating an incremental or absolute integrated measurement system.

[0058] As in Fig. Figure 7B, illustrating a proposed innovation of a guide rail 720, shows that instead of or in addition to a corresponding scale 703, a waveguide 704 can also be provided on, along, or in a suitable track or surface 705 of the guide rail 720. If a bearing ball or other rolling element rolls on the waveguide 704, which extends perpendicular to the plane of the paper along at least part of the length of the guide rail 710, the waveguide or element presses on the waveguide 705, causing deformation in it, and thus enabling an alternative position detection of the ball or roller carriage.

[0059] In Fig. Figure 8 illustrates another cross-section through a guide rail 800, in deviation from the one shown in Fig. Figure 7B illustrates guide rail 720 having a groove formed in a head surface 701 of the guide rail 800 and a corresponding waveguide, as previously designated 704, being provided in or on this.

[0060] Fig. Figure 9 shows an arrangement 900 in a partial perspective view, comprising a shaft 910 which is enclosed in a highly schematic and dashed-line ball-bearing housing 920. In the illustrated example, a waveguide, designated 704 as above, is inserted into the shaft 910 and extends over at least part of the length of the shaft 910.

[0061] In all the aforementioned examples of linear systems, pressing in the bearing ball or another rolling element can cause a displacement of a stationary shaft, which allows a conclusion to be drawn about a position. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited non-patent literature

[0000] “Handbook of Linear Technology” of the applicant, publication year 2006, ISBN 978-3-9816398-5-8

[0053] No. R999000466, “Integrated measuring system IMS for ball and roller rail guides

[0056]

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