JP7533262B2 - Boiler - Google Patents

Description

The present invention relates to a boiler that burns fuel to generate steam.

In boilers that generate steam by burning fuel, the pressure of the generated steam is measured and the measured pressure value is fed back to control the boiler operation. For this reason, it is necessary to quickly detect a malfunction of the device that measures the steam pressure (a steam pressure sensor as an example) and respond appropriately. In response to this, for example, when an abnormal value is output from the steam pressure sensor and the difference between the steam pressure measured by the steam pressure sensor and the steam pressure calculated from the steam temperature value becomes larger than a certain value, there is a boiler that controls the boiler operation based on the higher of these steam pressures (see, for example, Patent Document 1).

Patent No. 5665438

However, in conventional boilers, even if a steam pressure sensor is actually malfunctioning, if the steam pressure sensor outputs a value that can be obtained under normal circumstances and is not abnormal, there is a risk that it will not be possible to identify that the steam pressure sensor is malfunctioning. Also, for example, when the boiler water level is low, the steam pressure measured by the steam pressure sensor will be low while the steam pressure temperature value will be high, and the difference between the steam pressure measured by the steam pressure sensor and the steam pressure calculated from the steam temperature value may be greater than a certain value. In such cases, there is a risk that an abnormality in the steam pressure sensor will not be detected correctly.

The present invention was devised in light of this situation, and its purpose is to provide a boiler that can accurately determine failures in the device that measures steam pressure.

In order to achieve the above object, a boiler according to one aspect of the present invention is a boiler that generates steam by heating water tubes, and is equipped with a pressure detection means for detecting the pressure of the generated steam, a temperature detection means for detecting the temperature at a predetermined position in the boiler, a first water level detection means for detecting whether the water level in the water tubes has reached a first water level, and a determination means for determining that the pressure detection means is faulty when a specific condition is met, the specific condition being a situation in which the pressure detected by the pressure detection means is equal to or lower than a first value and the temperature detected by the temperature detection means is equal to or higher than a second value, and further a specific situation in which it is determined by the first water level detection means that the first water level has been reached.

According to the above configuration, even if the temperature is equal to or higher than the second value but the pressure is equal to or lower than the first value, if the water level in the water pipe has not reached the first water level, it is not determined that the pressure detection means is malfunctioning. However, it is possible to determine that the pressure detection means is malfunctioning under a specific situation in which the temperature is equal to or higher than the second value but the pressure is equal to or lower than the first value and the water level in the water pipe has reached the first water level. Therefore, it is possible to accurately determine malfunction of the pressure detection means.

Preferably, the boiler includes a second water level detection means for detecting whether the water level in the water pipe has reached a second water level higher than the first water level, and a water supply means for supplying water to the boiler, and the specific condition is a condition that can be met when, under the specific circumstances, a predetermined time has passed since the second water level detection means determined that the second water level has not been reached, and the second water level detection means has not determined that the second water level has been reached despite the water being supplied by the water supply means.

According to the above configuration, even under certain circumstances, if it is determined that the second water level has been reached before a predetermined time has elapsed, it is not determined that the pressure detection means has failed, and if a certain period of time has elapsed after it is determined that the second water level has not been reached under certain circumstances, it may be determined that the pressure detection means has failed. Therefore, even under certain circumstances, it is not immediately determined that the pressure detection means has failed, and failure of the pressure detection means can be determined with even greater accuracy.

Preferably, the second water level is the water level used for controlling the water supply in the boiler.

According to the above configuration, even under certain circumstances, if it is determined that the second water level (e.g., water supply start water level, reference water level, etc.) used for water supply control has been reached before a predetermined time has elapsed, it is not determined that the pressure detection means has failed, thereby improving accuracy.

Preferably, the first water level is a combustion stop water level that is defined as the water level when combustion is stopped in the boiler.

The above configuration makes it possible to prevent a simple overheating of the water tube from being judged as a failure of the pressure detection means, thereby improving accuracy.

Preferably, a combustion amount control means is provided for controlling the combustion amount, and the second value is a value corresponding to the combustion amount controlled by the combustion amount control means.

The above configuration improves accuracy by taking into account the amount of combustion when determining whether the pressure detection means is faulty.

Preferably, the predetermined position is a position on the surface of the water tube that corresponds to a water level that is equal to or lower than the first water level.

The above configuration improves accuracy by determining whether the pressure detection means is faulty by taking into account the water temperature inside the water pipe.

FIG. 2 is a diagram illustrating a schematic configuration of a boiler control device. 10 is a flowchart for explaining an example of a vapor pressure sensor failure-related process.

<Overview of the Configuration>
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the drawings. First, a schematic configuration of a boiler according to the present embodiment will be described with reference to FIG.

As shown in FIG. 1, the boiler 1 includes a boiler body 2 that burns fuel to generate steam, a water level detector 3, a pressure detector (steam pressure sensor) 4, a controller 5 that controls the operation of the boiler 1, a water supply line 6 that supplies water to the boiler body 2, a temperature detector (temperature sensor, scale monitor) 7, a blower 8 that sends air into the combustion chamber of the boiler body 2 through the air supply passage 2e, a steam separator 9, an exhaust passage (not shown) that draws out exhaust gas from the boiler body 2, and a fuel supply line (not shown) that supplies fuel to the boiler body 2. Note that, although an example in which the fuel is oil is described, the fuel is not limited to a liquid such as oil, and may be a gas such as gas.

The boiler body 2 is formed in a roughly cylindrical shape, and includes a burner 2a, multiple water tubes 2b, an upper header 2c, and a lower header 2d. The multiple water tubes 2b are housed inside the boiler body 2, and are erected at a predetermined interval in the circumferential direction of the boiler body 2. This forms a combustion chamber in roughly the center of the boiler body 2.

The burner 2a is provided above the combustion chamber. The burner 2a heats boiler water introduced into the inside of the multiple water tubes 2b to generate steam. The burner 2a is also connected to a fuel tank (not shown) via a fuel supply line. A flow control valve is provided on the fuel supply line. The combustion amount of the boiler 1 is adjusted continuously or stepwise by controlling the opening of the flow control valve with the control device 5. For example, during high combustion, the opening of the flow control valve is controlled to 100%, and during low combustion, the opening of the flow control valve is controlled to 50%.

The lower header 2d is provided at the bottom of the boiler body 2 and is connected to the bottom of the multiple water tubes 2b. The lower header 2d is connected to a water supply line 6. The water supply line 6 is provided with a water supply pump 61 and a check valve 62. Water is supplied from the water supply pump 61 to the lower header 2d via the water supply line 6, and the supplied water is heated in the water tubes 2b.

The upper header 2c is provided at the top of the boiler body 2 and is connected to the tops of the multiple water tubes 2b. The upper header 2c collects the steam generated in the multiple water tubes 2b and directs it to the steam separator 9 via the steam outlet passage.

The steam separator 9 separates the steam from the upper header 2c into dry steam and water. The dry steam separated by the steam separator 9 is sent to a specified device via a steam supply passage. Meanwhile, the water separated by the steam separator 9 is returned to the lower header 2d via a downflow passage that connects the steam separator 9 to the lower header 22.

The water level detection device 3 includes a water level control tube 30 made of a conductive metal and a plurality of electrode rods 31. The water level control tube 30 is formed in a substantially cylindrical shape with both ends sealed. The upper end of the water level control tube 30 is connected to the upper header 2c. The lower end of the water level control tube 30 is connected to the lower header 2d. Therefore, the water level in the water level control tube 30 is substantially the same as the water level of the water tube 2b in the boiler body 2. The water level control tube 30 is provided with a plurality of electrode rods 31. In this embodiment, the L rod 31L, M rod 31M, and S rod 31S are provided. The L rod 31L, M rod 31M, and S rod 31S are arranged with their respective tips (lower ends) spaced apart from each other in the vertical direction, and are configured to be able to detect a plurality of water levels in the water level control tube 30 in stages. The L rod 31L detects the lowest water level L, the M rod 31M detects a water level M higher than water level L, and the S rod 31S detects a water level S higher than water level M.

The water level L is the minimum water level required in a combustion state, and is the water level at which combustion stops if the water level remains below L for a specified period of time or more. In other words, it is the combustion stop water level used to control the boiler to forcibly stop combustion.

Water level M is the water level used for water supply control during high combustion. When the control device 5 controls the ON/OFF of the water supply pump, for example, water level M is the water supply start water level during high combustion, and controls so that water supply begins when the water level falls below water level M and stops when a predetermined time has elapsed after water level M is detected. In contrast, in the case of constant water level control (control that continuously supplies water to reach the reference water level), water level M is the reference water level during high combustion, and water supply control is performed so that it is always at water level M.

The water level S is the water level used for water supply control at the start of combustion or low combustion. For example, at the start of combustion, the control device 5 starts water supply when the water level falls below the water level S, and starts combustion on the condition that the water level is above the water level S. Furthermore, for example, when the control device 5 controls the ON/OFF of the water supply pump, the water level S is the water supply start water level at low combustion, and controls so as to start water supply when the water level falls below the water level S and to stop water supply a predetermined time after the water level S is detected. In contrast, in the case of constant water level control, the water level S becomes the reference water level at low combustion, and water supply control is performed so that the water level S is always the water level S.

The electrode rod 33 (D rod) is arranged from the upper header 2c toward the inside of the water tube 2b. The set water level at which the tip of the D rod 33 is located is called water level D. Water level D is a water level for preventing overheating, and is set at a position higher than water level S, for example.

The pressure detection unit 4 is a steam pressure sensor that is provided on the steam supply passage (steam outlet) side of the steam separator 9 and detects the pressure of the steam generated in the boiler 1. The pressure of the generated steam correlates with the pressure of the water tubes 2b in the boiler body 2. Therefore, the control device 5 controls the operating state (combustion state) of the boiler based on the steam pressure detected by the steam pressure sensor 4. For example, if the detected steam pressure value is higher than a steam pressure that is predetermined according to the amount of combustion, control such as increasing the amount of water supply or switching to low combustion is performed. Fault determination of the steam pressure sensor 4 will be described later.

The control device 5 is realized by a computer including an internal memory, timer, and calculation processing unit, and controls the operation and behavior of the boiler 1, for example, controlling the operation at ignition and shutdown, and multiple types of combustion states with different combustion amounts (e.g., low combustion, high combustion).

The temperature detection unit 7 is a temperature sensor that detects the temperature of the water tube 2b in the boiler body 2, and for example, a scale monitor can be used. The scale monitor 7 detects the temperature of the water tube to monitor the adhesion of scale to the water tube, but there is a correlation with the pressure in the water tube, making it possible to identify the pressure in the water tube to a certain extent. The scale monitor 7 is attached to the surface of the water tube 2b, and it is preferable to attach it at a position below the water level L. When the boiler 1 is in operation, the water level of the water tube 2b is normally maintained at a position higher than the water level L. Therefore, by installing the scale monitor 7 at a position below the water level L, it is possible to more reliably grasp the temperature of the water in the water tube 2b.

<Determining if the vapor pressure sensor is malfunctioning>
When the steam pressure sensor 4 is operating normally and the measured steam pressure is a correct value, the control device 5 can operate the boiler normally by controlling the boiler based on the measurement value of the steam pressure sensor 4. Even if the steam pressure sensor 4 is broken, if the control device 5 can determine that the sensor is broken, the boiler can be operated continuously by operating the boiler without performing control based on the measured steam pressure. For example, when the control device 5 determines that the steam pressure sensor 4 is broken, the control device 5 can continue to operate the boiler based on a predetermined relatively high value (e.g., a value of about 90% of the maximum steam pressure in the boiler specifications) instead of the measurement value of the steam pressure sensor 4.

On the other hand, if the steam pressure sensor 4 is broken and it is not possible to determine that the sensor is broken, the boiler may be controlled based on an incorrect measurement, which may result in the boiler not operating normally. For example, if the actual steam pressure is high, water should be supplied, but if the steam pressure sensor 4 is broken, a lower value than the actual value is measured, and water is not supplied as it should. As a result, the water level in the water tube 2b does not rise and does not reach a specified water level (for example, water level L, water level M, or water level S), and the boiler operation is forcibly stopped. A forced boiler shutdown can occur for reasons other than the steam pressure sensor 4, but considering the reduced combustion efficiency and the effort required for restarting the boiler, it is desirable to avoid this as much as possible.

The inventor therefore verified cases where the cause of a forced boiler shutdown was a failure of the steam pressure sensor. Specifically, the measurements of the steam pressure sensor and the temperature sensor when the boiler operation was forced to shut down were sampled and compiled. As a result, it was confirmed that cases where the forced shutdown was caused by a failure of the steam pressure sensor were concentrated in a range where, for example, the temperature measured by the temperature sensor was 130°C or higher and the pressure measured by the steam pressure sensor was 0 MPa or lower. In other words, a high temperature of 130°C or higher means that the pressure of the generated steam should also be relatively high, but due to the failure of the steam pressure sensor, the pressure value detected by the steam pressure sensor was 0 MPa or lower, which was extremely low compared to the pressure of the steam actually generated. As a result of the water supply control being performed based on the detected low pressure, the water level in the water pipe did not rise, leading to a forced shutdown. Furthermore, as a result of further verification, the inventors confirmed that even if the steam pressure sensor is not broken, even if the water level in the water tube has not reached a low level, such as water level L, and the water tube is simply overheated, it is possible for the temperature measured by the temperature sensor to be 130°C or higher and the pressure measured by the steam pressure sensor to be 0 MPa or lower.

Based on the above verification results, in the boiler 1 of this embodiment, the failure of the steam pressure sensor 4 can be accurately determined by considering the water level condition in addition to the temperature and pressure conditions. Specifically, it is possible to determine the failure of the steam pressure sensor 4 when a specific situation occurs in which the pressure detected by the steam pressure sensor 4 is equal to or lower than a first value indicating low pressure, the temperature detected by the scale monitor 7 is equal to or higher than a second value indicating high temperature, and the water level is determined to have reached the first water level indicating a low water level.

The first value may be a low pressure value, and is preferably set to, for example, 0 MPa relative to atmospheric pressure. The second value may be a high temperature of 100°C or higher, and is preferably set to, for example, within the range of 130°C to 200°C (for example, 150°C). The second value is preferably a value according to the combustion amount set by the control device 5 and the combustion state controlled by the control device 5. Since the temperature of the water tube varies depending on the combustion amount and combustion state, the steam pressure, which is the reference in the operating state of the boiler, also varies, and a higher value is set as the second temperature when the combustion amount and combustion state are higher. For example, 130°C (or 150°C) is set for low combustion, and 200°C is set for high combustion.

The first water level may be any low water level, and it is preferable to use, for example, water level L (e.g., the combustion stop water level). When the water level remains below water level L for a predetermined period of time or more, combustion stops, so the water level is equal to or higher than L during normal operation. Nevertheless, if the water level is below water level L while the temperature is equal to or higher than the second temperature, there is a high possibility that the water tube is simply overheated. By using water level L as the first water level, it is possible to prevent the steam pressure sensor from erroneously detecting a failure due to simple overheating of the water tube.

In addition, in the boiler 1 of this embodiment, it is preferable to add to the conditions for determining a failure of the steam pressure sensor 4 that, under the specific circumstances described above, after it is determined that the water level at that time has not reached the second water level higher than the first water level, a predetermined time has passed without determining that the second water level has been reached despite water being supplied. In other words, if the water level is sufficiently secured, or even if it is not secured, if the water level is supplied and reaches the second water level before the predetermined time has passed, and the water level is sufficiently secured afterwards, the steam pressure sensor is not determined to be faulty, but if the water level is not sufficiently secured and water has been supplied for a predetermined time but has not yet reached the second water level, it is possible to determine a failure of the steam pressure sensor. If the second water level is reached before the predetermined time has passed, it is assumed that sufficient water is being supplied, so it is not recognized as a failure. Here, the second water level may be any water level higher than the first water level, and for example, the water level S used for water supply control during low combustion at low combustion and the water level M used for water supply control during high combustion at high combustion are exemplified, but are not limited to these, and may be the water level D.

<About handling vapor pressure sensor failure>
2 is a flowchart for explaining an example of a steam pressure sensor failure related process. The steam pressure sensor failure related process is a process for determining a failure of the steam pressure sensor 4 of the boiler 1, and is executed by the control device 5.

In step S01, it is determined whether the pressure based on the steam pressure sensor 4 is 0 MPa or less. If it is determined that the pressure based on the steam pressure sensor 4 is 0 MPa or less, the process proceeds to step S02, and if it is determined that the pressure exceeds 0 MPa, the process returns to step S01.

In step S02, it is determined whether the temperature based on the scale monitor 7 is equal to or higher than the temperature corresponding to the amount of combustion (for example, 130°C for low combustion, 200°C for high combustion). If it is determined that the temperature is equal to or higher than the temperature corresponding to the amount of combustion, the process proceeds to step S03, and if it is determined that the temperature is less than the temperature corresponding to the amount of combustion, the process returns to step S01.

In step S03, it is determined whether the water level in the water tube is equal to or higher than a first water level (e.g., water level L). If it is determined that the water level is equal to or higher than water level L, the process proceeds to step S04, and if it is determined that the water level is less than water level L, the process returns to step S01.

In step S04, it is determined whether the water level in the water tube is below a second water level (e.g., water level S during low combustion, water level M during high combustion). If it is determined that the water level is below the second water level, the process proceeds to step S05, and if it is determined that the water level is equal to or greater than the second water level, the process returns to step S01.

In step S05, it is determined whether water is being supplied. If it is determined that water is being supplied, the process proceeds to step S06, and if it is determined that water is not being supplied, the process returns to step S01.

Steps S06 to S09 start measuring time after it is determined in step S04 that the water level in the water tube is below the second water level, and determine whether the second water level is reached before a predetermined time (e.g., 60 seconds) has elapsed. Specifically, in step S06, 1 is added to the value of the count timer. In step S07, it is determined whether the water level in the water tube is below the second water level. If it is determined that the water level is below the second water level, the process proceeds to step S08, and if it is determined that the water level is equal to or greater than the second water level, the steam pressure sensor failure-related processing is terminated since the water level is sufficiently secured.

In step S08, it is determined whether the value of the count timer has reached a value equivalent to a predetermined time (e.g., 60 seconds) or more. For example, if steps S06 to S09 are repeated every 2 ms, the value equivalent to 60 seconds would be 30,000 (= 60 seconds / 2 ms) if the processing of steps S06 to S09 is performed every 2 ms. If it is determined in step S08 that the value of the count timer has not reached a value equivalent to a predetermined time or more, i.e., if the predetermined time has not elapsed, proceed to step S09.

In step S09, it is determined whether the pressure based on the steam pressure sensor 4 is 0 MPa or less (i.e., whether the measured value has changed or not). If it is determined that the pressure based on the steam pressure sensor 4 is 0 MPa or less, the process returns to step S06. If it is determined that the pressure based on the steam pressure sensor 4 exceeds 0 MPa, the measured value fluctuates, so the steam pressure sensor 4 is unlikely to be faulty, and the steam pressure sensor fault-related processing is terminated. On the other hand, after it is determined that the second water level has not been reached under a specific situation and the count timer increment has started in step S06, for example, if the detected temperature falls below the second value (temperature according to the amount of combustion) or the water level falls below the first water level (water level L), the measurement for the specified time is not stopped but is continued. This is because there may be cases where the temperature or water level temporarily does not meet the specific situation.

On the other hand, if it is determined in step S08 that the count timer value has reached a value equivalent to or greater than the predetermined time, i.e., if the predetermined time has elapsed without the second water level being reached, the process proceeds to step S10. In step S10, since the water level has not reached the second water level or greater before the predetermined time has elapsed, the steam pressure sensor 4 is likely to have failed, and the water level is not sufficiently secured, control is switched to that in the event of a steam pressure sensor failure, and a notice is issued that the steam pressure sensor is failed. As control in the event of a steam pressure sensor failure, control is not performed based on the measured steam pressure value, but, for example, the boiler is continued to operate based on a predetermined relatively high value (e.g., a value of about 90% of the maximum steam pressure in the specifications) instead of the measured value of the steam pressure sensor 4. This allows the boiler 1 to continue to operate even when there is a high possibility that the steam pressure sensor 4 is failed.

As described above, in this embodiment, as shown in steps S01 to S03 of FIG. 2, even if the temperature is equal to or greater than the second value but the pressure is equal to or less than 0 MPa, if the water level in the water tube has not reached level L, it is not determined that the steam pressure sensor 4 is malfunctioning. However, it may be determined that the steam pressure sensor 4 is malfunctioning under specific circumstances in which the temperature is equal to or greater than the second value but the pressure is equal to or less than 0 MPa and the water level in the water tube has reached level L. Therefore, a malfunction of the steam pressure sensor 4 can be accurately determined.

In addition, in this embodiment, even under certain circumstances, as shown in steps S04 to S09 in FIG. 2, if it is determined that the second water level has been reached before a predetermined time has elapsed, it is not determined that the steam pressure sensor 4 has failed, but if a certain time has elapsed without the second water level being reached after it has been determined that the second water level has not been reached under certain circumstances, it may be determined that the steam pressure sensor 4 has failed. Therefore, even under certain circumstances, it is not immediately determined that the steam pressure sensor 4 has failed, and therefore a failure of the steam pressure sensor 4 can be determined with even greater accuracy.

In addition, in this embodiment, a second water level (e.g., water supply start water level, reference water level, etc.) used for water supply control in boiler 1 is defined as the water level that serves as the judgment criterion in step S07. Therefore, even under certain circumstances, if it is determined that the second water level (water level S during low combustion, water level M during high combustion) has been reached before a specified time has elapsed, it is not determined that the steam pressure sensor 4 is faulty, thereby improving accuracy.

In addition, in this embodiment, the combustion stop water level (water level L), which is defined as the water level when combustion in the boiler is stopped, is set as the water level that serves as the judgment criterion in step S03, so that it is possible to prevent simple overheating of the water tube from being detected as a failure of the steam pressure sensor, thereby improving accuracy.

In addition, in this embodiment, the temperature that serves as the judgment criterion in step S02 is set to a temperature that corresponds to the amount of combustion controlled by the control device 5. The temperature of the water in the water pipe may vary depending on the amount of combustion, but by taking the amount of combustion into account when judging a failure of the steam pressure sensor 4, accuracy can be improved.

In addition, in this embodiment, as shown in FIG. 1, the scale monitor 7 detects the temperature on the surface of the water tube at a position corresponding to a water level that is equal to or lower than the water level L. When the boiler 1 is in operation, the water level of the water tube 2b is higher than the water level L, so that the failure of the steam pressure sensor 4 is determined taking into account the water temperature inside the water tube, thereby improving accuracy.

The present invention is not limited to the above-described embodiment, and various modifications and applications are possible. Below, we will explain modifications of the above-described embodiment that can be applied to the present invention.

In the above embodiment, an example of determining whether the steam pressure sensor 4 is faulty has been described with reference to FIG. 2, but the present invention is not limited to this. For example, the process may be performed in steps S01 to S03, and if the water level is equal to or higher than the water level L and the determination is YES in step S03, the process may determine that the steam pressure sensor 4 is faulty and proceed to step S10. Alternatively, the process may be performed in steps S01 to S04, and if the water level is less than the water level S and the determination is YES in step S04, the process may determine that the steam pressure sensor 4 is faulty and proceed to step S10. Alternatively, the process may be performed in steps S01 to S05, and if water is being supplied and the determination is YES in step S05, the process may determine that the steam pressure sensor 4 is faulty and proceed to step S10.

In addition, in steps S04 and S07 of FIG. 2, an example has been described in which the second water level (water level S during low combustion and water level M during high combustion) is set as the judgment criterion, but this is not limiting, and water level D may be set as the judgment criterion. In addition, judgment using water level S during low combustion and water level M during high combustion as the judgment criterion and judgment using water level D as the judgment criterion may be used in combination, and a malfunction may be determined when at least one of the judgment criteria is met, or a malfunction may be determined when both judgment criteria are met.

In addition, while 60 seconds is exemplified as the predetermined time in step S08 in FIG. 2, the predetermined time is not limited to this, and may be, for example, 20 seconds shorter than the disconnection determination time of the electrode rod S as a reference.

In addition, an example was shown in which the pressure in the water pipe 2b was indirectly determined from the temperature of the water pipe 2b using the temperature detection means (scale monitor) 7, but instead of the temperature detection means, for example, a pipe pressure detection means that determines the degree of pressure in the water pipe 2b using a gauge resistance or the like may be used. In this case, the specific condition for determining that the pressure detection means (steam pressure sensor) is malfunctioning may be a situation in which the pressure detected by the pressure detection means (steam pressure sensor) is equal to or lower than a first value and the pressure detected by the pipe pressure detection means (gauge resistance or the like) is equal to or higher than a second value (the pipe pressure corresponding to the temperature of the water pipe being, for example, 130°C), and further, a specific situation in which it is determined that the water level L has been reached may be established, or a specific situation in which it is determined that the second water level has not been reached under the specific situation, and then a specific time has passed without determining that the second water level has been reached despite water being supplied.

The embodiments disclosed herein should be considered in all respects as illustrative and not restrictive. The scope of the present invention is indicated by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

Reference Signs List 1 Boiler 2 Boiler body 2a Burner 2b Water tube 2c Upper header 2d Lower header 2e Air supply passage 3 Water level detection device 30 Water level control tube 31 Electrode rod 31L L rod 31M M rod 31S S rod 33 Electrode rod (D rod)
4 Pressure detection unit 5 Control device 6 Water supply line 7 Temperature detection unit 8 Blower 9 Steam-water separator

Claims (6)

A boiler that heats water tubes to generate steam,
A pressure detection means for detecting the pressure of the generated steam;
A temperature detection means for detecting a temperature at a predetermined position in the boiler;
a first water level detection means for detecting whether the water level in the water pipe has reached a first water level;
a determination means for determining that the pressure detection means is malfunctioning when a specific condition is satisfied,
The specific condition is a condition that can be met when a specific situation is met in which the pressure detected by the pressure detection means is equal to or lower than a first value and the temperature detected by the temperature detection means is equal to or higher than a second value, and further in which the first water level detection means determines that the first water level has been reached. a second water level detection means for detecting whether the water level in the water pipe has reached a second water level higher than the first water level;
a water supply means for supplying water to the boiler,
The boiler described in claim 1, wherein the specific condition is a condition that can be satisfied when, under the specific circumstances, a predetermined time has elapsed since the second water level detection means determined that the second water level has not been reached, and then the second water level detection means has not determined that the second water level has been reached, even though water is being supplied by the water supply means. The boiler according to claim 2, wherein the second water level is a water level used for controlling water supply in the boiler. The boiler according to any one of claims 1 to 3, wherein the first water level is a combustion stop water level that is set as the water level when combustion in the boiler is stopped. A combustion amount control means for controlling a combustion amount is provided,
5. The boiler according to claim 1, wherein the second value is a value according to a combustion amount controlled by the combustion amount control means. The boiler according to any one of claims 1 to 5, wherein the predetermined position is a position on the surface of the water tube that corresponds to a water level that is equal to or lower than the first water level.

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