Deterioration diagnosis method for ultraviolet flame detectors

Abstract

To provide a deterioration diagnosis method for an ultraviolet flame detector that can incorporate flame detector deterioration monitoring into a conventional monitoring system with no need for a monitoring system that performs high-speed scanning separately from the flame detector.SOLUTION: A deterioration diagnosis method for determining a degree of deterioration of an ultraviolet flame detector 10 for detecting the presence or absence of a flame on a burner by detecting the amount of ultraviolet light radiated from the flame, comprises: sampling flame current when the burner is stopped, considering the cases in which the flame current rises above a certain value to be a self-discharge occurrence, calculating a probability of self-discharge occurring, for example, on a daily basis, from the number of samplings and the number of times self-discharge has occurred, and determining the deterioration by a deterioration monitor 18 or 20 depending on the degree of increase in the probability of self-discharge occurrence.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a degradation diagnosis method for determining the degree of degradation of an ultraviolet flame detector. [Background technology]

[0002] As a device for checking the presence or absence of a burner flame, an ultraviolet flame detector is known which detects the presence or absence of a flame by detecting the amount of ultraviolet light radiated from the flame. Ultraviolet flame detectors use the property that when ultraviolet light hits an internal electrode, a discharge occurs due to the photoelectric effect. An impulse voltage is applied to the electrodes, and the electrode spacing and voltage are set so that a discharge will not occur unless ultraviolet light is incident, and the presence or absence of a flame (ultraviolet rays) is determined by the discharge current when the impulse voltage is applied.

[0003] When a flame detector deteriorates, it can self-discharge, causing discharge even when there is no flame. If this event occurs during combustion, even though the actual flame may have disappeared due to some factor, the sequence interlock control unit will correctly determine that a flame exists and will continue to output the fuel shutoff valve open operation signal, causing the burner to continue releasing fuel, which could lead to a serious accident.

[0004] Furthermore, if an abnormality occurs during non-combustion, a combustion device equipped with a burner will output a fuel shutoff valve open operation signal after confirming that there is no flame just before ignition. However, if the presence of a flame is detected just before ignition, the sequence interlock control unit will determine that ignition is dangerous, and the interlock will be activated as a pseudo-flame anomaly, and the combustion device will be abnormally stopped without outputting a fuel shutoff valve open operation signal.

[0005] Flame detectors are consumables and their sudden abnormal shutdown could have a major impact on the operation of equipment, so they are replaced regularly. However, due to differences in the operation of the combustion equipment and individual differences, they may deteriorate (self-discharge) in a shorter period of time than expected, causing the combustion equipment to shut down due to a pseudo-flame abnormality. For this reason, the following methods have traditionally been proposed as methods for detecting deterioration and failure of flame detection equipment. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2020-165825 A Summary of the Invention [Problem to be solved by the invention]

[0007] In Patent Document 1, signs of flame detector deterioration are detected based on the probability of discharge when the shutter is opened and closed, without being affected by fluctuations in the power supply voltage. It is known that flame detectors use flame current (or flame voltage) as a method for monitoring the flame detection state, deterioration, and failure. In Patent Document 1, monitoring using flame voltage is an issue, so as a countermeasure, the probability of discharge is calculated and monitored from the discharge current when an impulse voltage is applied.

[0008] The flame current is obtained by integrating the discharge current generated when ultraviolet light is incident while an impulse voltage is applied to electrodes inside the flame detection device and converting it into a current output (when converted to a voltage output, it becomes the flame voltage, and the flame current and the flame voltage have the same characteristics).As described in Patent Document 1, it is difficult to read momentary abnormalities using the flame current, and since the flame current is also affected by fluctuations in the power supply voltage, it has been difficult to detect deterioration of a flame detector based solely on the degree of fluctuation in the flame current.

[0009] In addition, with a normal flame detector, self-discharge can be reduced to zero by completely blocking the entry of ultraviolet light when there is no flame. However, the structure of the burner has an observation window for visually checking the flame, making it difficult to completely block ultraviolet light. Although the probability is low, self-discharge will occur even in normal products, and the probability of this occurring also depends on the power supply voltage, so there was an issue that deterioration cannot be determined solely on the presence or absence of self-discharge.

[0010] For this reason, Patent Document 1 proposes forcibly controlling the incidence of ultraviolet light by opening and closing the shutter, etc., to detect abnormalities from the probability of discharge while the shutter is open and closed, but since the impulse voltage depends on the commercial power supply frequency, in 50 Hz areas it is applied at least once every 20 msec, and if a discharge occurs during that time, it will occur over a period of several ms. For this reason, not only is a monitoring system capable of high-speed scanning separate from the conventional flame detection device necessary, but in some cases there is an issue that this cannot be implemented due to space restrictions.

[0011] The present invention aims to provide a deterioration diagnosis method for an ultraviolet flame detector that does not require a monitoring system that performs high-speed scanning processing separate from the flame detector, and that makes it possible to incorporate flame detector deterioration monitoring into the system of a conventional monitoring device. [Means for solving the problem]

[0012] Self-discharge is an event that occurs when there is no flame, and as the flame detector deteriorates, the probability of self-discharge increases, although it is a low probability, and this is based on the fact that it can be seen as a temporary increase in the flame current. If it is a temporary increase in the flame current, it is possible to incorporate flame detector deterioration monitoring into a conventional monitoring device system without adding a monitoring system with high-speed scanning processing. In addition, since sampling is performed at a fixed cycle, the deterioration monitoring unit may be incorporated into a remote monitoring device connected by communication or the like.

[0013] The deterioration diagnosis method for an ultraviolet flame detector of the present invention is a deterioration diagnosis method for determining the degree of deterioration of an ultraviolet flame detector which detects the presence or absence of a burner flame by detecting the amount of ultraviolet light radiated from a flame, and is characterized in that the frame current while the burner is stopped is sampled, and when the flame current rises to a certain value or above, it is deemed that a self-discharge has occurred, the probability of self-discharge occurrence is calculated at regular intervals from the number of samples and the number of times self-discharge has occurred, and deterioration is determined based on the degree of increase in the probability of self-discharge occurrence.

[0014] In the above method, for example, the probability of self-discharge occurrence is calculated for each day. In the above method, if the probability of self-discharge occurring is higher than the previous time, +2 points are added, and if the probability is lower than the previous time, -1 point is subtracted. When the points reach a specified value, it can be determined that the battery has deteriorated. Effect of the Invention

[0015] The deterioration diagnosis method for an ultraviolet flame detector of the present invention does not require a monitoring system that performs high-speed scanning processing separate from the flame detector, and it is possible to incorporate deterioration monitoring of the flame detector into the system of a conventional monitoring device.

[0016] By detecting deterioration trends while the burner is stopped, sudden equipment shutdowns can be avoided. For example, by calculating the probability per day, the effects of temporary voltage fluctuations can be averaged out, making it possible to increase the reliability of deterioration diagnosis.

[0017] In the early stages of degradation, the probability of self-discharge is extremely low, and attempting to diagnose degradation by the number of discharges using high-speed scanning would require a large data storage area. However, monitoring using frame current makes it possible to capture the degradation trend even with a sampling period of one minute, enabling the data storage area to be kept small.

[0018] If the probability increases from the previous day, +2 points are added, and if it decreases, -1 point is subtracted. By determining that the probability has deteriorated when the points reach a specified value, it is possible to reduce the impact of temporarily occurring unreliable probabilities and achieve more accurate deterioration judgments during normal operation. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is an explanatory diagram showing a schematic configuration of an apparatus for carrying out the degradation diagnosis method of the present invention. [Diagram 2] FIG. 2 is an explanatory diagram showing an example of a control flow in the degradation diagnosis method of the present invention. [Diagram 3]FIG. 3 is a bar graph showing an example of deterioration determination in the deterioration diagnosis method of the present invention. [Figure 4] FIG. 4 is a line graph showing an example of deterioration determination in the deterioration diagnosis method of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiment and can be modified as appropriate. FIG. 1 shows a schematic configuration of an apparatus for carrying out the degradation diagnosis method of the present invention.

[0021] As shown in Fig. 1, ultraviolet flame detector 10 uses the characteristic that discharge occurs due to the photoelectric effect when ultraviolet light hits the internal electrodes, applies an impulse voltage to the electrodes, sets the electrode distance and voltage at which discharge will not occur unless ultraviolet light is incident, and judges the presence or absence of flame (ultraviolet rays) by the discharge current when the impulse voltage is applied (the discharge current conversion unit 12 judges and outputs the presence or absence of flame and the flame current). 24 is a flame detection circuit, 26 is an impulse voltage generation unit, and 28 is a commercial power source.

[0022] When the ultraviolet flame detector 10 deteriorates, a phenomenon called self-discharge occurs, in which discharge occurs even in the absence of a flame. If this event occurs during combustion, even though the actual flame has disappeared due to some factor, the sequence interlock control unit 14 will normally determine that there is a flame and will continue to output the fuel cutoff valve open operation signal, so the burner will continue to release fuel, which may lead to a serious accident. 30 is the fuel cutoff valve.

[0023] Furthermore, if an abnormality occurs during non-combustion, a burner-equipped combustion device (not shown, see "Flame" in FIG. 1) will output a fuel cutoff valve open operation signal after confirming that there is no flame just before ignition. However, if the presence of a flame is detected just before ignition, the sequence interlock control unit 14 will determine that ignition is dangerous, and an interlock will be activated as a pseudo flame abnormality, causing the combustion device to stop abnormally without outputting a fuel cutoff valve open operation signal.

[0024] Flame detectors are consumables, and a sudden abnormal shutdown would have a significant impact on the operation of equipment, so they are replaced regularly. However, due to differences in the operation methods of the combustion equipment and individual differences, they may deteriorate (self-discharge) in a shorter period of time than expected, causing the combustion equipment to shut down due to a pseudo-flame abnormality. What we focused on was that self-discharge is an event that occurs without a flame, and that as the battery deteriorates, the probability of self-discharge increases, although it is a low probability, and this can be seen as a temporary increase in the flame current.

[0025] If the flame current is only a temporary increase, it is possible to incorporate flame detector deterioration monitoring into a conventional monitoring device system without adding a monitoring system equipped with high-speed scanning processing (see deterioration monitoring unit 18 of burner control device 16 in FIG. 1). Note that because the sampling is performed at a fixed cycle, the deterioration monitoring unit 20 may be incorporated into a remote monitoring device 22 connected by communication or the like.

[0026] Next, an example of the degradation diagnosis method of the present invention will be described. The frame current is sampled while the burner is stopped, and when the frame current rises above a certain value, it is deemed to be a self-discharge occurrence. The probability of self-discharge occurring is calculated for each day, and deterioration is judged from the probability of self-discharge occurring.

[0027] By detecting deterioration trends while the burner is stopped, sudden equipment shutdowns can be avoided, and by calculating the probability per day, the effects of temporary voltage fluctuations can be averaged out, making it possible to increase the reliability of deterioration diagnosis.

[0028] In the early stages of degradation, the probability of self-discharge is extremely low, and attempting to diagnose degradation by the number of discharges using high-speed scanning would require a large data storage area. However, monitoring using frame current makes it possible to capture the degradation trend even with a sampling period of one minute, enabling the data storage area to be kept small.

[0029] The probability of self-discharge is affected by local operation and power supply voltage due to a and b below, so the probability of self-discharge occurring may vary from site to site. a. The number of burner shutdowns that occur in a day varies depending on the operational conditions at the site. If the shutdown time is short, the denominator becomes smaller, reducing the reliability of the probability. b. The higher the impulse voltage, the more likely self-discharge is to occur. However, since the impulse voltage is proportional to the local power supply voltage, the probability of self-discharge varies from site to site.

[0030] For this reason, it is difficult to determine deterioration based on a fixed threshold from the self-discharge probability, so deterioration is determined based on the degree of increase in probability. To determine the degree of increase in probability, a 2Up1Down counter is used, and if the probability has increased from the previous day, +2 points are added, and if it has decreased, -1 is subtracted. Deterioration is determined when the points reach a specified value, which reduces the impact of temporarily occurring unreliable probabilities and achieves more accurate deterioration determination during normal operation.

[0031] It is also possible to achieve higher accuracy by setting a lower limit for the burner stop time used in the judgment and excluding the stop time below the lower limit from the judgment, or by monitoring the power supply voltage and performing sampling only when the power supply voltage is within a certain range. EXAMPLES

[0032] The following describes an embodiment of the present invention, but the present invention is not limited to the following embodiment and can be modified as appropriate. Figure 2 shows an overview of this embodiment (an example of actual deterioration determination).

[0033] The flame detector flame current is sampled every minute while the burner is stopped. The number of samples is S, and the number of samples with a flame current of 1 μA (*1) or more is A. A is considered to be the number of times self-discharge has occurred, and the self-discharge probability P is calculated for each day (*2) as follows (see F1 in Figure 2). P=A / S×100

[0034] 1. If S is less than 30 (※3), point C will not change from the previous day (see F2 and F7 in Figure 2). 2. If S is 30 or more (※2) (see F2 in Figure 2) and P is 0.1% or more (※4) (see F3 in Figure 2) and the probability has increased compared to the previous day (see F4 in Figure 2), increase C by +2 (※5) (see F5 in Figure 2). 3. If S is 30 or more (※2) and P is less than 0.1% (see F3 in Figure 2) or has decreased from the previous day (see F4 in Figure 2), subtract 1 (※6) from C (see F6 in Figure 2). Note that the lower limit is 0, and if the result is negative, reset C to 0. 4. If C is 10 (※7) or more, it is determined to be degraded (see F8 in Figure 2).

[0035] An example of the actual determination as described above is shown in Figs. 3 and 4. The value and probability of the discharge current change depending on the flame detector circuit constant, impulse voltage, etc., and as a result, the flame current value also changes. Furthermore, the amount of ultraviolet light entering the burner while it is stopped changes depending on the structure and settings of the combustion equipment, so each parameter *1 to *7 can be changed depending on the circuit used, the structure and installation conditions of the combustion equipment, etc.

[0036] There is also a known method of integrating the discharge current and converting it into a frame voltage, but since the characteristics remain the same after conversion, only the unit changes from current to voltage, either value can be used for this deterioration detection. In addition, by reducing the amount of data, the deterioration judgment unit can be incorporated into a microcomputer or other device that controls the burner, but it is also acceptable to transmit the data remotely via communication and perform probability calculations and judgments on a server PC or the like. [Explanation of symbols]

[0037] 10. Ultraviolet flame detector 12 Discharge current converter 14 Sequence interlock control section 16 Burner control device 18, 20 Deterioration monitoring section 22 Remote monitoring equipment 24 Flame detection circuit 26 Impulse voltage generator 28 Commercial power supply 30 Fuel shutoff valve

Claims

1. A deterioration diagnosis method for determining the degree of deterioration of an ultraviolet flame detector that detects the presence or absence of a burner flame by detecting the amount of ultraviolet rays emitted from a flame, characterized in that the flame current is sampled when the burner is stopped, and when the flame current rises to a certain value or above, it is deemed that a self-discharge has occurred, the probability of self-discharge occurrence is calculated at regular intervals from the number of samples and the number of times self-discharge has occurred, and deterioration is determined based on the degree of increase in the probability of self-discharge occurrence.

2. 2. The method for diagnosing deterioration of an ultraviolet flame detector according to claim 1, wherein the probability of occurrence of self-discharge is calculated for each day.

3. 3. The method for diagnosing deterioration of an ultraviolet flame detector according to claim 1 or 2, wherein the degree of increase in the probability of self-discharge occurrence is determined by adding +2 points if the probability is higher than the previous time, subtracting -1 points if the probability is lower than the previous time, and determining that deterioration has occurred when the points reach a specified value.

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