Sealing ring, arrangement and method for detecting wear on a piston compressor

Abstract

The invention relates to a sealing ring (1) for a piston rod packing of a compressor with at least two circumferentially adjacent ring segments (2) which are arranged around a common principal axis (3), wherein the sealing ring (1) is circumferentially enclosed on its outer circumferential surface by a clamping ring (4) made of an elastic material, the electrical resistance of which changes depending on the circumferential extent of the clamping ring (4).

Description

[0001] The invention relates to a sealing ring with at least two circumferentially adjacent ring segments arranged around a common principal axis. The invention further relates to an arrangement and a compressor comprising a sealing ring or arrangement. The invention also relates to a method for detecting the wear condition of a piston rod packing of a compressor.

[0002] Compressors are fluid energy machines that convert supplied energy into other energy states. Compressors are used in a variety of applications, for example, in the form of piston compressors for compressing gases.

[0003] Compressors are typically operated continuously for several months to years and are only shut down for maintenance. During this continuous operation, the functionality of compressor components can be impaired, for example, by wear, deposits, or component failure. This can lead to a reduction in compressor efficiency, even to its complete inoperability. Various monitoring and diagnostic methods are known in the art to detect such processes early and, if necessary, to take measures to counteract damage such as wear, erosion, or deposits. For piston compressors, monitoring the sealing system between the moving piston rod and the stationary compressor housing is of particular importance.

[0004] A sealing system for a piston compressor typically includes a piston rod packing, also known as a piston rod seal or piston rod ring. The primary function of a piston rod packing is to allow the movement of the piston rod while preventing the escape of gases or liquids from the compression chamber. A piston rod packing typically comprises a packing body and several packing rings arranged within it. The packing rings enclose the piston rod and are made of a material that provides a seal when in contact with the piston rod's outer surface, such as graphite or a plastic like polytetrafluoroethylene (PTFE). The packing rings conform to the piston rod's outer surface, thereby preventing the escape of gases or liquids from the compression chamber.Permanent contact between the piston rod's outer surface and the sealing rings can be ensured, for example, by pressing the sealing rings radially onto the piston rod via tension springs. Additionally, the pressure within the piston rod packing chambers typically presses the sealing rings against the piston rod.

[0005] Sealing rings suitable for use in piston compressors are known from the prior art, for example from document DE 10 2006 015 327 A1. Due to their design, the sealing rings wear over time through the constant friction of their radially inner surface against the outer surface of the piston rod. It is therefore necessary to regularly inspect the piston rod packing and, if necessary, maintain or replace it to prevent leaks and ensure optimal performance of the piston compressor.

[0006] Document DE 10 2017 202 148 A1 discloses a sealing ring for a piston rod packing, which has an indicator means that can detect a change in the radial expansion of the sealing ring. The indicator means can, for example, be a pin attached to the sealing ring, the position of which can be detected by a stationary sensor, such as an optical sensor.

[0007] In addition to optical monitoring, electromechanical monitoring devices are also known for other applications. For example, document DE 10 2020 211 404 A1 describes a sealing device with sensor technology for condition monitoring, comprising a sealing ring with a dynamic sealing section for dynamic sealing against a sealing surface of a machine part and a preload ring for preloading the sealing section against the sealing surface. A measuring element is arranged on the preload ring, which responds to a deflection movement of the preload ring and thus detects a change in the state of the sealing ring. However, this monitoring device is unsuitable for use in piston rod packings because its operating principle is based on the preload ring preloading the sealing section of the sealing ring against a housing, which is structurally impossible in a typical piston rod packing.

[0008] A disadvantage of the methods and systems known from the prior art is that they require complex instrumentation or can only be used for special compressor designs.

[0009] The task was to provide a device and a method for detecting wear on the sealing system of piston compressors that can reliably provide information about the wear condition, is simple and cost-effective to install and maintain, and can be used for a wide variety of piston compressors.

[0010] This problem is solved according to the invention by a sealing ring according to claim 1, an arrangement according to claim 5, a compressor according to claim 7 and a method according to claim 8. Preferred embodiments of the invention are specified in the dependent claims.

[0011] In the following, the terms "have," "exhibit," "comprise," or "include," or any grammatical variations thereof, are used in a non-exclusive manner. Accordingly, these terms can refer both to situations in which, apart from the feature introduced by these terms, no other features are present, and to situations in which one or more other features are present. For example, the expression "A has B," "A exhibits B," "A comprises B," or "A includes B" can refer both to the situation in which, apart from B, no other element is present in A (i.e., a situation in which A consists solely of B) and to the situation in which, in addition to B, one or more other elements are present in A, such as element C, elements C and D, or other elements.

[0012] Furthermore, it should be noted that the terms "at least one" and "one or more," as well as grammatical variations of these terms or similar terms, when used in connection with one or more elements or features and intended to express that the element or feature may be present once or multiple times, are generally used only once, for example, when the feature or element is first introduced. Upon subsequent mention of the feature or element, the corresponding term "at least one" or "one or more" is generally no longer used, without restricting the possibility that the feature or element may be present once or multiple times.

[0013] Furthermore, the terms "preferably," "in particular," "for example," or similar terms are used in the following text in connection with optional features without limiting alternative embodiments. Features introduced by these terms are optional features, and it is not intended that these features limit the scope of protection of the claims, and in particular the independent claims. As the person skilled in the art will recognize, the invention can also be implemented using other embodiments. Similarly, features introduced by "in one embodiment of the invention" or by "in an exemplary embodiment of the invention" are understood as optional features without limiting alternative embodiments or the scope of protection of the independent claims.Furthermore, these introductory expressions are intended to leave all possibilities of combining the features introduced herein with other features, whether optional or non-optional features, unaffected.

[0014] One aspect of the invention relates to a sealing ring for a piston rod packing of a compressor with at least two circumferentially adjacent ring segments arranged around a common principal axis, characterized in that the sealing ring is circumferentially enclosed on its outer circumferential surface by a clamping ring made of an elastic material, the electrical resistance of which changes depending on the circumferential expansion of the clamping ring.

[0015] Another aspect of the invention relates to an arrangement comprising at least one sealing ring according to the invention, a resistance measuring device configured to detect the change in the electrical resistance of the clamping ring of the at least one sealing ring, and an evaluation unit configured to generate a signal characteristic of the resistance from the data detected in the resistance measuring device.

[0016] Another aspect of the invention relates to a compressor with a piston rod and with at least one sealing ring encompassing the piston rod according to the invention and / or with at least one arrangement according to the invention.

[0017] Another aspect of the invention relates to a method for detecting the wear condition of a piston rod packing of a compressor. The piston rod packing has at least one sealing ring with at least two ring segments adjacent to one another in the circumferential direction and arranged about a common principal axis, wherein the sealing ring is circumferentially enclosed on its outer circumferential surface by a clamping ring made of an elastic material, the electrical resistance of which changes depending on the circumferential expansion of the clamping ring. The method comprises the steps: a) Measuring the electrical resistance of the clamping ring of the at least one sealing ring, b) Generating a signal characteristic of the resistance from the data acquired in step 1. c) Comparison of the characteristic signal with a reference value representing a good condition of the piston rod packing, as a measure of the wear condition of the piston rod packing.

[0018] The invention offers several advantages. For example, the sealing ring according to the invention can be used in place of conventional sealing rings. It is therefore suitable for various compressors, regardless of their design. The sealing ring is inexpensive to manufacture, easy to install, and virtually maintenance-free. Standard industrial components, which are cost-effective and easy to install, can be used to measure the electrical resistance of the clamping ring and to evaluate the collected data. This allows for the simple and reliable acquisition of information about the wear condition of a piston rod packing in a piston compressor, which can then be used for planning maintenance or optimizing compressor operating time.

[0019] Piston rod packings are commonly used in piston compressors to create a seal between two chambers and prevent the escape of gases or liquids from either chamber. To achieve this seal, a piston rod packing contains at least one sealing ring. Multiple sealing rings can also be arranged in series around the piston rod. If multiple sealing rings are present, they can be of identical design or different types.

[0020] Sealing rings suitable for piston rod packings are known from the prior art, for example from documents DE 10 2006 015 327 A1 and DE 10 2017 202 146 A1. The sealing ring according to the invention comprises at least two circumferentially adjacent ring segments arranged about a common principal axis. The principal axis corresponds to the cylinder axis of the piston, which is sealed by the piston rod packing. The sealing ring can also comprise more than two ring segments, for example three, four, five or six ring segments.

[0021] On its outer circumferential surface, the sealing ring is surrounded by a clamping ring. The axial dimension of the clamping ring, i.e., along the main axis, is preferably from 5 mm to 15 mm. This axial dimension can be constant or variable around the circumference of the clamping ring; preferably, it is constant. The radial dimension of the clamping ring, i.e., its thickness, is preferably from 1 mm to 5 mm. This radial dimension can also be constant or variable around the circumference of the clamping ring; preferably, it is constant.

[0022] In one embodiment, the outer circumferential surface of the sealing ring has a circumferential groove in which the clamping ring is arranged. An advantage of this embodiment is that the clamping ring is prevented from slipping axially by the groove edges, so that the clamping ring is permanently and stably attached to the outer surface of the sealing ring.

[0023] The clamping ring is made of an elastic material whose electrical resistance changes depending on the circumferential expansion of the clamping ring. Preferably, the clamping ring is made of an elastic material in which the change in electrical resistance exhibits no hysteresis effects. This ensures that each value of the clamping ring's expansion corresponds to a unique resistance value.

[0024] In one embodiment, the elastic material comprises an electrically conductive elastomer. Preferably, the elastomer is rubber-based and contains electrically conductive particles or fibers. The conductive particles or fibers can, for example, comprise carbon, metal, or silicon dioxide. Particles can be incorporated into the base material, e.g., rubber, during the elastomer production process, for example, in powder form or as small granules. Fibers can have different lengths. They can, for example, be similarly short to the particles. However, they can also be designed as wires that cover part or all of the circumference of the clamping ring. Fibers can also be incorporated into the base material, e.g., rubber, during the elastomer production process.

[0025] The choice of elastic material can depend on the specific intended use, for example on process parameters such as pressure and temperature or the chemical properties of the substances with which the sealing ring comes into contact when used in a compressor.

[0026] The elastic material can, for example, have a specific resistance per unit length of the clamping ring, which can be specified in Ω / m (ohms per meter). The change in length can be easily determined from the change in resistance, which in turn is proportional to the change in the diameter or radius of the sealing ring.

[0027] Due to the elasticity of its material, the clamping ring can exert a compressive force on the ring segments and preload the clamping ring radially in the direction of the piston rod. The preload force can be selected according to the specific requirements of the application. Preferably, the clamping ring rests in close contact with the outer circumferential surface of the sealing ring, both in its unworn and worn states.

[0028] In one embodiment of the invention, an arrangement according to the invention comprises a resistance measuring device configured to detect the change in the electrical resistance of the clamping ring of the sealing ring. The electrical resistance of the clamping ring can be detected, for example, by a resistance measuring device. In one embodiment, the clamping ring is electrically connected in series with a defined resistor, with a constant voltage applied to the circuit. In this case, the voltage drop across the clamping ring is directly proportional to its change in resistance. The change in electrical resistance can also be detected using other types of electrical circuits, for example, bridge circuits.

[0029] In a preferred embodiment, the electrical resistance of the clamping ring is detected without contact. In one embodiment, the arrangement according to the invention comprises at least one transmitter, for example an RFID chip.

[0030] In one embodiment, the data acquired by the resistance measuring device is fed to an evaluation unit. For this purpose, both the resistance measuring device and the evaluation unit can each have a communication interface through which the data can be exchanged. This communication can be wired or wireless. The data can also be transmitted from the resistance measuring device to the evaluation unit via a transfer device. The transfer device can, for example, be a storage medium on which the acquired data can be stored and retrieved. The transfer device can also be integrated into the communication via wired and / or wireless means, for example, as cloud-based storage.

[0031] The evaluation unit is designed to generate a signal characteristic of the resistance from the data acquired by the resistance measuring device. This characteristic signal can be, for example, a value in ohms. It can also be a voltage signal in volts, from which the resistance can be determined.

[0032] In one embodiment, the evaluation unit generates a signal from the acquired data that indicates a measure of the sealing ring's wear condition. Such a signal can be determined, for example, by calculating the length or change in length of the sealing ring from the data acquired in the resistance measuring device, using the resistance rate specific to the elastic material of the clamping ring. Instead of the length or change in length, other characteristic values ​​of the sealing ring can also be calculated, such as a radius, a change in radius, a diameter, or a change in diameter.

[0033] The data acquired by the resistance measuring device can be used in their original form to generate the characteristic signal. Alternatively, the data can be processed using signal processing methods, such as smoothing, averaging, or filtering.

[0034] In one embodiment, the arrangement according to the invention further comprises a temperature measuring device for detecting the temperature at and / or around the sealing ring. The temperature measuring device can, for example, be a temperature sensor such as a PT100, a resistance thermometer such as an NTC, or a thermocouple.

[0035] In one embodiment, the evaluation unit is designed to take the data acquired by the temperature measuring device into account when generating the resistance characteristic signal in such a way that the resistance characteristic signal is corrected for temperature influences. For example, if the resistance value depends not only on the change in length of the clamping ring but also on the temperature prevailing in or on the clamping ring, this measure allows the temperature dependence to be corrected so that only the dependence of the resistance value on the change in length of the clamping ring is considered. This increases the reliability and informative value of the resistance characteristic signal.

[0036] In one embodiment, the signal characteristic of the resistance is transmitted from the evaluation unit to a display unit. The display unit can, for example, include a display for graphically showing the characteristic signal. The display unit can be installed stationary at a fixed location or be located in a mobile device, such as smartphones, tablets, or wearables carried by an operator. In the case of displaying the characteristic signal on a mobile device, the evaluation unit preferably includes a communication interface through which it can communicate with the mobile device.

[0037] In one variant, the characteristic signals are displayed in their temporal sequence in the display unit. Such a display has the advantage that, in addition to the absolute numerical value of the characteristic signal, a temporal trend can also be recognized, for example, the reduction of the outer diameter of a sealing ring over time as a measure of the wear prevailing in the piston rod packing.

[0038] In one embodiment, the signal characteristic of the resistance is compared with a reference value representing a good condition of the piston rod packing. This comparison serves as a measure of the wear condition of the piston rod packing. The reference value can be a fixed, predetermined value, for example, a material property of the elastic material used in the clamping ring. For comparison purposes, it is advantageous if the characteristic signal and the reference value have comparable units of measurement, for example, both representing electrical resistance or both representing a unit of length. However, the comparison can also be based on different physical data, for example, by converting the characteristic signal or the reference value into a comparable quantity using appropriate correlations.

[0039] In one embodiment, the comparison of the characteristic signal with the reference value is performed in the evaluation unit. In this case, the evaluation unit has means for comparison. These means for comparison can be an arithmetic unit of a processor, in which arithmetic and comparison operations can be performed.

[0040] In one embodiment, the single sealing ring or the multiple sealing rings in a piston rod packing are calibrated at the beginning of their use, for example, after they have been replaced following compressor maintenance. Preferably, during calibration, the electrical resistance of the unworn sealing ring is determined and stored in an electronic memory for later use. The value of the electrical resistance in the unworn state, or a signal derived from it that is characteristic of the resistance, can be used as a reference value representing a good condition of the piston rod packing.

[0041] The evaluation unit and the display unit can be implemented as separate units or as parts of a shared or higher-level data processing system. They can be implemented as software components, hardware components, or combinations of hardware and software components. The evaluation unit, the display unit, and / or the data processing system can be located locally on the piston compressor, for example, as a standalone application on a compressor system. The evaluation unit, the display unit, and / or the data processing system can also be part of a larger automation system, for example, as a component of a programmable logic controller (PLC) or a process control system (PCS). They can be implemented as a centralized system or as a decentralized system distributed across multiple components that exchange data with each other.

[0042] Further details and features of the invention will become apparent from the following description of preferred embodiments, particularly in conjunction with the dependent claims. The respective features can be implemented individually or in combination with one another. The invention is not limited to these embodiments. The embodiments are shown schematically in the drawings. The drawings are to be understood as schematic representations. They do not constitute a limitation of the invention, for example, with regard to specific dimensions or design variants. Identical reference numerals in the individual drawings denote identical or functionally equivalent elements, or elements that correspond to one another with respect to their functions.

[0043] They show: Fig. 1: Sectional views of a sealing ring according to the invention in its unworn state Fig. 2: Sectional views of the sealing ring according to Fig. 1 in worn condition Reference symbol list 1 sealing ring 2 ring segment 3 Main axis 4 clamping rings 5 shot game

[0044] The left image in Fig. Figure 1 schematically shows a cross-section through a sealing ring for a piston rod packing of a compressor in an unworn state as an embodiment of the invention. The illustrated sealing ring 1 comprises three ring segments 2, which in this example are identically shaped. They adjoin each other circumferentially and are arranged about a common main axis 3, which is Fig. 1 is shown as the intersection of the two dashed lines. In the depicted unworn state, the inner diameter of the sealing ring corresponds to the outer diameter of the piston rod for which it is intended to seal. The three ring segments 2 are designed such that, in the unworn state, a gap forms between each pair of adjacent ring segments 2 at the inner edge, which is also referred to as the butt clearance 5. The outer edge of the ring segments 2 has no gap, resulting in a continuous outer circumferential surface of the sealing ring.

[0045] On its outer circumferential surface, the sealing ring 1 is enclosed by a clamping ring 4, the inner surface of which rests tightly against the outer circumferential surface of the sealing ring 1. The outer diameter of the sealing ring 1 corresponds to the inner diameter of the clamping ring 4 and, in its unworn state, has the value D1. The figure on the right illustrates this. Fig. 1 schematically a longitudinal section through the sealing ring 1, for example along the vertical dashed line of the cross-section.

[0046] Fig. Figure 2 shows schematic cross-sectional views of the sealing ring according to Fig. 1 in the worn state. In this example, a worn state means that, due to friction between the inside of the sealing ring 1 and the piston rod (not shown), material has been worn away from the inner surface of the ring segments 2. The radial expansion of the ring segments 2 is reduced compared to the unworn state, and the end gap 5 has shrunk to a value close to zero. Since the ring segments 2 still bear against the piston rod, the inner diameter of the sealing ring 1 remains unchanged. However, due to the reduced radial expansion, the outer diameter of the sealing ring 1 is reduced. The in Fig. The diameter of the outer circumferential surface of the sealing ring 1, designated D2, and thus also the inner diameter of the clamping ring 4, is smaller than the diameter D1 according to Fig. 1 in unworn condition.

[0047] The clamping ring 4 is made of an elastic material whose electrical resistance changes depending on the circumferential expansion of the clamping ring 4. In the unworn state according to Fig. 1. The clamping ring 4 has a first value R1 for electrical resistance. In the worn state according to Fig.The clamping ring has a second value R2 for electrical resistance, where the second value R2 is lower than the first value R1. Knowing the radius r1 of the outer circumferential surface of the sealing ring 1 and the change in resistance due to thermal expansion of the elastic material of the clamping ring, the change in the outer diameter of the clamping ring in its worn state can be easily calculated. This can be done, for example, using the formula R1−R2=(r1−r2)2πk where r1 is the radius of the outer circumferential surface of the sealing ring in the unworn state, r2 is the radius of the outer circumferential surface of the sealing ring in the worn state, and k is the specific resistance rate per length of the clamping ring. 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 patent literature

[0000] DE 10 2006 015 327 A1 [0005, 0020] DE 10 2017 202 148 A1

[0006] DE 10 2020 211 404 A1

[0007] DE 10 2017 202 146 A1

[0020]

Claims

[1] Sealing ring (1) for a piston rod packing of a compressor with at least two circumferentially adjacent ring segments (2) which are arranged about a common principal axis (3), characterized by , that the sealing ring (1) is enclosed on its outer circumferential surface in the circumferential direction by a clamping ring (4) made of an elastic material, the electrical resistance of which changes depending on the expansion of the clamping ring (4) in the circumferential direction. [2] Sealing ring (1) according to claim 1, characterized by that the elastic material comprises an electrically conductive elastomer, preferably an elastomer based on a rubber containing conductive particles or fibers. [3] Sealing ring (1) according to claim 1 or 2, characterized by , that the extension of the clamping ring (4) in the axial direction is from 5 mm to 15 mm and / or the extension of the clamping ring (4) in the radial direction is from 1 mm to 5 mm. [4] Sealing ring (1) according to one of the preceding claims, characterized by , that the outer circumferential surface of the sealing ring (1) has a circumferential groove in which the clamping ring (4) is arranged. [5] Arrangement comprising at least one sealing ring (1) according to one of claims 1 to 4 and a resistance measuring device configured to detect the electrical resistance of the clamping ring (4) of the at least one sealing ring (1), and an evaluation unit configured to generate a signal characteristic of the resistance from the data detected in the resistance measuring device. [6] Arrangement according to claim 5, comprising a temperature measuring device for detecting the temperature at and / or around the sealing ring, wherein the evaluation unit is configured to take into account the temperature measured values ​​detected in the temperature measuring device when generating the signal characteristic of the resistance in such a way that the signal characteristic of the resistance is corrected for temperature influences. [7] Compressor with a piston rod and with at least one sealing ring (1) encompassing the piston rod according to one of claims 1 to 4 and / or with at least one arrangement according to one of claims 5 to 6. [8] Method for detecting the wear state of a piston rod packing of a compressor, wherein the piston rod packing has at least one sealing ring (1) with at least two ring segments (2) adjacent to each other in the circumferential direction and arranged about a common principal axis (3), and the sealing ring (1) is enclosed circumferentially on its outer circumferential surface by a clamping ring (4) made of an elastic material, the electrical resistance of which changes in the circumferential direction depending on the expansion of the clamping ring (4), the method comprising the steps: a) Determining the electrical resistance of the clamping ring (4) of the at least one sealing ring (1), b) Generating a signal characteristic of the resistance from the data acquired in step a), c) Comparison of the characteristic signal with a reference value representing a good condition of the piston rod packing, as a measure of the wear condition of the piston rod packing.

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