Method for predicting a time of a failure of a component of a field device, and field device

Abstract

The invention relates to a method for predicting a time of a failure of a component (1) of a field device (2), wherein: the field device (2) determines and / or monitors at least one chemical and / or physical parameter of a medium (3); the field device (2) is designed to determine a measurement signal of the component (1); the measurement signal is assigned a threshold value; the component (1) is exposed to aging influences which influence the measurement signal, the method comprising at least the following steps: - recording measurement values of the measurement signal of the component (1) over a measurement period, - determining a current state of the component (1) on the basis of the recorded measurement values, - determining whether the aging influences on the component (1) are increasing or decreasing, - calculating the time of the failure of the component (1) on the basis of the current state and the threshold value, - if the aging influences are increasing or decreasing, outputting information regarding the changed time of the failure as a result of the increasing or decreasing aging influences.

Description

[0001] Method for predicting a time of failure of a component of a field device and field device

[0002] The invention relates to a method for predicting the time of failure of a component of a field device, wherein the field device determines and / or monitors at least one chemical and / or physical parameter of a medium. The field device is configured to determine a measurement signal of the component, wherein a limit value is assigned to the measurement signal, and wherein the component is exposed to aging influences that affect the measurement signal. The invention further relates to a field device configured to carry out the method.

[0003] Field devices in process and automation technology are used to monitor and / or determine at least one process variable, such as a chemical or physical variable, of a medium. For the purposes of this application, field devices essentially refer to all measuring devices that are used close to the process and that provide or process-relevant information. A large number of such field devices are manufactured and distributed by companies in the Endress+Hauser Group.

[0004] The process variable to be determined by the field device can be the fill level, flow, pressure, temperature, pH value, redox potential, or conductivity of the respective medium. The various possible measuring principles underlying the determination of the process variable are known from the state of the art and will not be explained further here. Field devices for measuring fill levels are designed in particular as microwave level gauges, ultrasonic level gauges, time domain reflectometric level gauges (TDR), radiometric level gauges, capacitive level gauges, conductive level gauges, and vibronic level gauges. Field devices for measuring flow, on the other hand, operate according to the Coriolis, ultrasonic, vortex, thermal, and / or magnetic inductive measuring principles.Pressure measuring devices are typically absolute, gauge, or differential pressure devices. In addition to the previously mentioned measuring devices and actuators, field devices also include remote I / Os, wireless adapters, and generally devices located at the field level.

[0005] Field devices have a number of components which serve, for example, to attach the field device to a container, supply the field device with energy, determine and / or monitor at least one chemical and / or physical parameter of the medium, evaluate measurement signals, display information about the field device and / or the medium, etc. Most of the components are subject to an aging process which, over time, leads to wear and tear and ultimately to component failure.

[0006] For example, sealing elements that seal the interior of a field device from the medium must be replaced regularly to prevent failure and the penetration of medium into the field device. For sealing elements, it is known to calculate the remaining service life of the sealing element based on a temperature determined in the area of ​​the sealing element, so that the sealing element can be replaced in a timely manner. Regular maintenance intervals that are not based on a calculation or estimation of the remaining service life have the disadvantage of scheduling maintenance significantly too early or too late, thus resulting in unnecessarily high costs.

[0007] Electrical and electronic components of the field device are also subject to aging. However, the extent of these aging effects cannot be easily measured, as in the example of the sealing element. In particular, the aging effects can change over time and become more or less pronounced at times, so that the remaining service life changes accordingly. Therefore, it is not possible for an operator or user of the field device to determine the current condition of the component and when it should be serviced to prevent failure.

[0008] It is therefore the object of the present invention to provide a method and a field device which simplify the maintenance of a component.

[0009] The object is achieved according to the invention by a method according to claim 1 and a field device according to claim 9.

[0010] The object is achieved with regard to the method according to the invention by a method for predicting a time of failure of a component of a field device, wherein the field device determines and / or monitors at least one chemical and / or physical parameter of a medium, wherein the field device is designed to determine a measurement signal of the component, wherein a limit value is assigned to the measurement signal, wherein the component is exposed to aging influences which influence the measurement signal, wherein the method comprises at least the following steps:

[0011] Recording measured values ​​of the component’s measurement signal over a measuring time,

[0012] Determine the current condition of the component based on the recorded measured values, Determine whether the aging effects on the component are increasing or decreasing,

[0013] Calculate the time of failure based on the current state and the limit value,

[0014] In the event that the aging influences increase or decrease, output information about the time of failure changed by the increasing or decreasing aging influences.

[0015] The method according to the invention simplifies component maintenance. By outputting information about the time of failure, which changes due to increasing or decreasing aging influences, the operator or user of the field device can easily determine when the component should be serviced in order to prevent component failure.

[0016] The component is, in particular, an electrical or electronic component. The component may be designed to determine the measurement signal. However, a computing unit of the field device may also be designed to determine the measurement signal. The component's measurement signal is influenced by aging and can increase or decrease. If the measurement signal exceeds or falls below the limit value, the component fails. Aging influences include, for example, environmental influences such as temperature, humidity, etc.

[0017] If the aging effects on a component increase significantly over a certain period of time, the remaining service life may be unexpectedly shortened and the point of failure may occur significantly earlier. Scheduled maintenance for the component may then need to be performed earlier than planned before the specified period.

[0018] Conversely, the effects of aging may also be temporarily less pronounced than in a previous period, extending the remaining service life and the time of failure of the component accordingly. In this case, the component's maintenance interval may also need to be adjusted.

[0019] If, on the other hand, the aging influences on the component are essentially constant, i.e. remain the same, the remaining service life decreases essentially monotonically continuously. In this case, information about a changed time of failure is not provided because the time for component failure and a possible time for servicing the component remain unchanged. The information about the time of failure changed due to the increasing or decreasing aging influences includes, in addition to an indication of the time of failure, preferably also an indication of the type and / or degree of change in the time of failure. In this way, the operator can quickly see that the time of failure has unexpectedly changed compared to a previous time and how.The type and / or degree of change in the time of failure can be indicated, for example, using one or more arrows, the number of which is determined by the degree of change and / or the orientation of which indicates the type of change in the remaining service life, i.e., increasing or decreasing. Alternatively, the type and / or degree of change in the time of failure can also be indicated in text form.

[0020] In a further development, the current condition and a recently recorded measurement value are used to determine whether the aging influences on the component are increasing or decreasing. For example, it can be checked to what extent the last recorded measurement value corresponds to the current condition. If deviations occur, the aging influences on the component are increasing or decreasing.

[0021] In one embodiment, the current state is calculated as the integral of the measured values ​​over the measurement time. The measured values ​​are multiplied by their respective measurement time interval, and the resulting products are summed.

[0022] In a further embodiment, an estimated value for the last measured value is determined based on the current state, whereby a comparison of the estimated value with the last measured value provides a statement about the increase or decrease in aging influences. Since the current state includes the history of the determined measured values, an estimated value for the last measured value can be determined based on the current state, e.g., by extrapolating the determined measured values ​​(excluding the last measured value). The comparison of the estimated value with the last measured value indicates whether the last measured value deviates from the history of the determined measured values ​​and is thus a measure of a change in aging influences.

[0023] In case of a negative difference between the estimated value and the last measured value, it can be stated that the ageing influences are increasing.

[0024] If the difference between the estimated value and the last measured value is positive, it can be concluded that the aging influences are decreasing. A further development provides that information about the change in the time of failure due to increasing or decreasing aging influences is only output if the change in the time of failure exceeds a predefined threshold. For example, the threshold can specify a defined number of days, weeks, or months. This ensures that information about the change in the time of failure is not output for every small change in the time of failure.

[0025] With regard to the field device, the object underlying the present application is achieved by a field device of process and automation technology with a component, wherein the field device determines and / or monitors at least one chemical and / or physical parameter of a medium, wherein the field device is designed to determine a measurement signal of the component, wherein a limit value is assigned to the measurement signal, wherein the component is exposed to aging influences which influence the measurement signal, wherein the field device has a computing unit which is designed to carry out a method according to the previous embodiments, and wherein the field device has a display unit which is designed to output the information about the time of the failure changed by an existing or decreasing fault.

[0026] By means of the field device according to the invention, it is achieved that a change in the time of failure due to increasing or decreasing aging influences can be quickly recognized and maintenance of the component can be planned accordingly.

[0027] In a further development, the display unit has a display, e.g. an LC display.

[0028] In one embodiment, the component is a terminal connection and the measurement signal is a terminal voltage. The terminal connection is designed to mechanically and electrically connect the field device to a power source. A terminal voltage can be measured at the terminal connection. Due to aging, the terminal voltage approaches a limit value beyond which the power source can no longer guarantee the supply of electrical energy to the field device. Possible maintenance of the terminal connection includes, among other things, tightening any loose terminal connection.

[0029] In an alternative embodiment, the component is a sensor unit and the measurement signal is a sensor signal. The sensor unit is configured to determine a sensor signal. The field device can be configured to determine and / or monitor the at least one chemical and / or physical parameter of the medium based on the sensor signal. Aging can cause the amplitude of the sensor signal to attenuate. If the amplitude is too attenuated, the at least one chemical and / or physical parameter of the medium can no longer be reliably determined.For example, the field device is a radar-based level gauge that has a transmission unit as a sensor unit, which is particularly designed to be exposed to a high-frequency signal and by means of which high-frequency signals can be transmitted towards a filling material and, after reflection from a filling material surface, can be received as received signals. The transmission unit can preferably be designed as an antenna or measuring probe. The level gauge can further have a signal generation unit designed to generate the high-frequency signal to be transmitted, as well as a reception unit designed to record the received signal. The sensor signal in this example is the high-frequency signal.

[0030] The present invention will be explained in more detail below with reference to the following figures 1-2. They show:

[0031] Fig. 1 : an embodiment of a field device according to the invention.

[0032] Fig. 2: a schematic curve of the component’s measurement signal.

[0033] The method according to the invention can be used on all types of field devices. An example of a field device 2 according to the invention is shown schematically in Fig. 1. The field device 2 has a component 1, in this example a terminal connection 6, a computing unit 4 and a display unit 5. The field device 2 is used to determine and / or monitor at least one chemical and / or physical parameter of a medium 3. The medium 3 is generally located in a container 8 to which the field device 2 is attached. The field device 2 can comprise a sensor unit 7, which is arranged such that it projects into the container 8. The sensor unit 7 can be designed to determine a sensor signal, based on which the at least one chemical and / or physical parameter of the medium 3 is determined. The component 1 or the terminal connection 6 is used in Fig.1 for connecting the field device 2 to a power source 9 via an electrical line 10. The field device 2 is designed to determine a terminal voltage of the terminal connection 6. The terminal voltage is influenced by aging.

[0034] Fig. 2 shows an example curve of a terminal voltage v over time t. At the beginning, the terminal voltage v has a starting value vo. Due to aging influences, the terminal voltage v increases over time t. The terminal voltage v is assigned a limit value VG. If the limit value VG is exceeded, the terminal connection 6 fails and the field device 1 is no longer supplied with power. The graph has three time sections A, B and C. In section A, the terminal voltage v increases essentially monotonically. The contribution of the aging influences is constant. Although the remaining service life decreases between t0 and t1 in section A, the time of failure of the terminal connection 6 remains the same. Accordingly, no information is provided about the (unchanged) time of failure.

[0035] In section B, the increase in terminal voltage v exhibits a significantly greater gradient than in section A. The aging influences in section B are increasing compared to section A. After the time ti is exceeded, the time of failure will occur significantly earlier than the time of failure calculated in section A, since the remaining service life has decreased unexpectedly sharply. Since the aging influences increase after the time ti, information is output about the time of failure changed by the increasing aging influences.

[0036] In section C, the gradient of the terminal voltage v is significantly lower than in section B. The aging effects are decreasing or less pronounced than in section B, so that the remaining service life is greater than the remaining service life calculated in section B. The time of failure of the terminal connection 6 occurs later than calculated in section B. After the measuring time t2 has been exceeded, information is provided about the time of failure which has changed due to the decreasing aging effects. The information may not be output directly after the measuring time t2 has been exceeded, but can also only be output after several measuring points within section C, since the first measuring point determined in section C may lead to a barely changed time of failure.It may be that the time of failure changes only after the contribution of several measuring points in section C, so that the information about the time of failure changed by the decreasing aging influences is only output then.

[0037] Fig. 2 is merely an exemplary diagram for an increase and decrease in aging influences. The example is not limited to a terminal connection 6 and a terminal voltage, but can be transferred to other components, such as a sensor unit with a sensor signal. It may be that an increase or decrease in aging influences only changes the time of failure insignificantly, so that no information is provided about the time of failure changed by the decreasing aging influences, in particular if a threshold value for the change in the time of failure has been defined. The method according to the invention provides that, in a first step, measured values ​​of the measurement signal are determined over a measurement time, as shown by way of example in Fig. 2. Based on the determined measured values, a current state of component 1 is determined. The current state is, for example, the integral of the measured values ​​over the measurement time, i.e.Z =. ■ v it where v t the respective measured value and At the measuring time interval associated with the measured value and Z the current state.

[0038] Subsequently, it is determined whether the aging influences on component 1 are increasing or decreasing. This can be done, for example, based on the current state and a recently recorded measured value. Thus, based on the current state, an estimated value for the last recorded measured value can be determined, and by comparing the estimated value with the last recorded measured value, a statement can be made about the increase or decrease in the aging influences. The estimated value v v can be calculated as v v = 2(z ~ °' t:> + Vqi where t is the measurement time and vo is the first measured value. By calculating the difference between the estimated value v v and the last measured value v n , i.e. Av = v v - v n, an increase or decrease in the aging influences can be determined. If Av is negative, the aging influences are increasing or have increased. If Av is positive, the aging influences are decreasing or have decreased. In a further step, the time of failure of component 1 is calculated based on the current condition Z and the limit value VG. The remaining service life t R can be calculated, for example, using the following formula: t R = ( G ~ o) ■ t - t. From the remaining lifetime t R results in the

[0039] W _ ^o)

[0040] Time of failure by summing the remaining lifetime t R with the measurement time t.

[0041] In a final step of the method, information about the time of failure changed by the increasing or decreasing aging influences is output if the aging influences increase or decrease. Optionally, a predefined threshold value can be assigned to the change in the time of failure. The information about the time of failure changed by the increasing or decreasing aging influences is then only output if the change in the time of failure exceeds a predefined threshold value. The information about the time of failure changed by the increasing or decreasing aging influences can include both an indication of the time of failure and an indication of the type and / or degree of the change in the time of failure. List of reference symbols

[0042] 1 component

[0043] 2 Field device 3 Medium

[0044] 4 Computing unit

[0045] 5 Display unit

[0046] 6 terminal connection

[0047] 7 Sensor unit 8 Container

[0048] 9 Power source

[0049] 10 electrical cables

Claims

Patent claims 1 . Method for predicting a time of failure of a component (1) of a field device (2), wherein the field device (2) determines and / or monitors at least one chemical and / or physical parameter of a medium (3), wherein the field device (2) is designed to determine a measurement signal of the component (1), wherein a limit value is assigned to the measurement signal, wherein the component (1) is exposed to aging influences which influence the measurement signal, wherein the method comprises at least the following steps: Recording measured values of the measuring signal of the component (1) over a measuring time, Determining the current state of the component (1) based on the measured values, Determine whether the aging effects on component (1) are increasing or decreasing, Calculate the time of failure of the component (1) based on the current state and the limit value, In the event that the aging influences increase or decrease, output information about the time of failure changed by the increasing or decreasing aging influences.

2. Method according to claim 1, wherein it is determined on the basis of the current state and a last recorded measured value whether the aging influences on the component (1) are increasing or decreasing.

3. Method according to one of the preceding claims, wherein the current state is calculated as an integral of the determined measured values over the measuring time.

4. Method according to one of the preceding claims, wherein an estimated value for the last recorded measured value is determined on the basis of the current state, wherein a statement on the increase or decrease of the aging influences is made on the basis of a comparison of the estimated value with the last recorded measured value.

5. Method according to claim 4, In the case of a negative difference between the estimated value and the last measured value, it is stated that the ageing influences are increasing.

6. The method according to claim 4, wherein in the case of a positive difference between the estimated value and the last measured value, the statement is made that the ageing influences are decreasing.

7. Method according to one of the preceding claims, wherein the information about the time of failure changed by the increasing or decreasing aging influences is only output if the change in the time of failure exceeds a predetermined threshold value.

8. Method according to one of the preceding claims, wherein the information about the time of failure changed by the increasing or decreasing aging influences comprises an indication of the time of failure and an indication of the type and / or degree of change in the time of failure.

9. A field device for process and automation technology (2) with a component (1), wherein the field device (2) determines and / or monitors at least one chemical and / or physical parameter of a medium (3), wherein the field device (2) is designed to determine a measurement signal of the component (1), wherein a limit value is assigned to the measurement signal, wherein the component (1) is exposed to aging influences which influence the measurement signal, wherein the field device (2) has a computing unit (4) which is designed to carry out a method according to claims 1-8, and wherein the field device has a display unit (5) which is designed to output the information about the time of failure of the component (1) which has changed due to the increasing or decreasing aging influences.

10. Field device according to claim 9, wherein the display unit (5) has a display. 11 . Field device according to one of claims 9-10, wherein the component (1) is a terminal connection (6) and the measurement signal is a terminal voltage.

2. Field device according to one of claims 9-10, wherein the component (1) is a sensor unit (7) and the measurement signal is a sensor signal.

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