JPH0232524B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is designed to control the operation of a boiler using a water level detection device installed to guide the water level inside the boiler to the outside of the boiler, such as in a multi-tubular once-through boiler. This invention relates to an overheat prevention device in a boiler.

An example of a water level control mechanism in a conventional boiler of this kind is shown in FIG. 1. In a boiler formed by connecting an upper header 1 and a lower header 2 with a large number of water pipes 3, 1 and lower header 2
Float-type or electrode-type water level detectors 8, 9, 1 are installed in the water level control tube 4 as a water level detection device that guides water inside the boiler to the outside using connecting pipes 12, 13.
0 and 11 are provided, and the starting and stopping of the water supply pump 6 and the burner 7 are controlled via the controller 5 based on the signals from these detectors.

The water level detector 8 is a detector that detects the lowest water level (minimum water level d), and is used as a ground electrode. The other three water level detectors 9, 10, 11 are used as electrodes on the anti-ground side. The water level detector 9 detects the water level C and issues a signal to start (when the water level increases and reaches the water level C) and stop (when the water level decreases and reaches the water level C) the combustion of the burner 7. Water level detector 10 detects water level b and issues a signal to start water pump 6 (when the water level decreases and reaches water level b), and water level detector 11 detects water level a and issues a signal to start water pump 6 (when the water level decreases and reaches water level b). When the water level increases and reaches water level a), a signal is issued.
With this method, during normal operation, the water level is a
and b, and when the water level drops below C, combustion in the burner 7 is stopped in order to prevent the water pipe 3 from overheating.

In this type of boiler, the water level inside the boiler, especially in the water pipes, is in a boiling state and is unstable, making it difficult to clearly detect the water level, so water is led outside the boiler and the water level is determined using a separate water level detection device. However, in the conventional device as described above, the difference between the water level in the boiler and the water level in the water level control tube 4 is used to detect the evaporation amount, combustion amount,
It has been difficult to completely prevent overheating of the water pipes since the temperature varies depending on the temperature of the canned water and other factors. Furthermore, if the connecting pipe 12 or 13 becomes clogged or frozen, the burner 7 continues to burn even if the water surface is below the water level C, resulting in a dry firing accident.

In order to improve this drawback, for example,
112405, a water level detector is installed on the upper pipe header,
There is also a method to operate the water pump by adding a time factor, but there is no function to directly stop combustion depending on the water level in the water pipe, and the time factor is involved, and the water supply pump is activated by the amount of evaporation and pressure. Since the performance of the pumps varies and it is not possible to replenish a constant amount of water, it has been difficult to reliably prevent dry firing.

An object of the present invention is to provide a boiler overheating prevention device that can directly detect the water level in a water pipe, reliably prevent overheating of the water pipe, and prevent dry firing accidents, without the above-mentioned drawbacks of the conventional one. The purpose is to

The present invention provides a water level control tube 4 with a water level detection device installed to guide the water level inside the boiler to the outside of the boiler, which is equipped with a water supply pump 6 and a burner 7.
In the boiler overheat prevention device, which is configured to detect and control the operation of the boiler, there are three water level detectors in the water level control tube 4: a water pump start water level detector 10 and a water pump stop water level detector 11. and a combustion start/stop water level detector 9, and a safe water level detector 8 is provided at a safe water level at which overheating does not occur even if combustion occurs in the boiler, and the safe water level detector 8 is used to activate the water pump.・A common ground terminal is used for the stop water level detection circuit and the combustion start/stop water level detection circuit, and the contact 18 is connected to the water supply pump 6 to connect the combustion supply valve 2 of the burner 7.
This is an overheating prevention device for a boiler, characterized in that a time-limited return contact 21 is connected and arranged at 0.

Embodiments of the present invention will be described using the drawings.

In FIGS. 2 and 3, the water level detector 8 is installed in the water pipe 3, and its detected water level d' is higher than the water level C at which the burner starts and stops, and even when the boiler is started. If the water level reaches that level, it acts as a safe water level detection end for detecting a safe water level at which overheating of the water pipe 3 does not occur.

To explain the detection circuit and control circuit with reference to FIG. 3, 14 is an AC power supply, the water level detector 8 for safe water level is connected to the ground side, and the other water level detectors 9, 10, 11 are connected to the anti-ground side. It is connected.
A water level detector 9 for detecting the boiler combustion start/stop water level C is connected to an AC power source 14 via a relay 15, and together with the water level detector 8 forms a combustion start/stop water level detection circuit. Water pump starting water level b
The water level detector 10 that detects the
7 to the AC power supply 14, and the water level detector 8
Together with this, a water pump starting water level detection circuit is formed. The water level detector 11 for detecting the water supply pump stop water level a is connected to the AC power supply 14 via the above-mentioned relay 17 in common, and together with the water level detector 8 forms a water supply pump stop water level detection circuit. That is, the water level detector 8, which is a safe water level detection end, serves as a common ground end for the water supply pump start/stop water level detection circuit and the combustion start/stop water level detection circuit. As for the control circuit, a contact 18 is connected to the water supply pump 6, and a time-limited return contact 21 is commonly connected to the fan 19 of the burner 7 and the fuel supply valve 20 (electromagnetic valve).

The operation will be explained.

When the inside of the water pipe 3 reaches a boiling state in a steady state, the water level in the water pipe 3 rises relative to the water level in the water level control cylinder 4, and the grounding of the water level detector 8 is continuously maintained. Therefore, when the water level inside the water level control tube 4 decreases from the starting water level b, the water supply pump 6 starts and the water level rises, and when it reaches the stop water level a, the water pump 6 stops, and this is repeated until the water level reaches a. ~b
kept between.

If the water level in the water pipe 3 becomes lower than the safe water level d' for some reason during operation, the water level detector 8 will no longer be grounded, and the contact 18 will be turned on by the action of the relay 17, regardless of the water level in the water level control tube 4. First, the water supply pump 6 starts.

Even if the water supply pump 6 operates, the water level in the water pipe 3 does not return to the safe water level d' within the specified time, or even if the water level in the water level control tube 4 falls below the water level C and a specified period of time has passed. If the water level does not return to C, combustion is stopped by the action of the time-limited return contact 21 to prevent overheating. The reason why the time-limited return contact 21 is used here is to prevent chattering because the water level in the water tube 3 fluctuates violently in a boiling state.

At the time of startup, the water level in the water pipe 3 and the water level in the water level control tube 4 are almost the same since boiling is not occurring. The water supply pump 6 continues to operate until the water level reaches the safe water level d', and the water level rises until the water level reaches the safe water level d'.
Only after reaching d' does the water supply pump 6 stop and combustion begin.

In this way, when combustion starts at startup, the water level in the water pipe 3 has already reached the safe water level d', so there is no risk of the water pipe 3 overheating and causing a dry firing accident.

FIG. 4 shows a detection circuit of another embodiment, in which the combustion start/stop water level C and the water supply pump start water level b are made to match, and the water level detector 10 is also used as the water level detector 9. You can omit one.

The above is a description of the multi-tubular once-through boiler.
The present invention can be applied to other boilers, regardless of the type of boiler, in which the difference between the water level in the boiler and the water level in the water level control cylinder changes due to combustion.

The present invention includes three water level detectors in a water level control cylinder: a water pump start water level detector, a water pump stop water level detector, and a combustion start/stop water level detector, and the combustion in the boiler is carried out. A safe water level detector is provided at a safe water level that does not cause overheating, and the safe water level detector is used as a common ground terminal for the water pump start/stop water level detection circuit and the combustion start/stop water level detection circuit. By connecting a contact to the water pump and connecting and deploying a time-limited return contact to the burner combustion supply valve, safe operation can be achieved even if the performance of the water pump differs, and even if the water level in the boiler water pipe is at a boiling point, it can be operated safely. Stable operation is possible without chattering even under strong vibrations, and regardless of startup, steady operation, or abnormal conditions, it prevents water pipes from running dry due to insufficient water level, and reliably prevents boiler overheating. Therefore, it is possible to provide a boiler overheating prevention device that can provide a boiler overheating prevention device that can achieve extremely great practical effects.

[Brief explanation of drawings]

FIG. 1 is a flow diagram of a conventional example, FIG. 2 is a flow diagram of an embodiment of the present invention, FIG. 3 is a detection and control circuit diagram thereof, and FIG. 4 is a detection circuit diagram of another embodiment. 1...Upper header, 2...Lower header, 3...Water pipe,
4... Water level control cylinder, 5... Controller, 6... Water supply pump,
7...Burner, 8,9,10,11...Water level detector,
12, 13... Connection pipe, 14... AC power supply, 15... Relay, 16... Contact, 17... Relay, 18... Contact,
19...Fan, 20...Fuel supply valve, 21...Time-limited return contact.

Claims (1)

[Claims] 1. The water level in the boiler equipped with the water supply pump 6 and the burner 7 is detected by a water level control tube 4 equipped with a water level detection device installed to guide the water level in the boiler to the outside of the boiler to control the operation of the boiler. In the overheat prevention device for a boiler, the water level control tube 4
There are three water level detectors inside: a water pump start water level detector 10 and a water pump stop water level detector 11.
and a combustion start/stop water level detector 9, and a safe water level detector 8 is provided at a safe water level at which overheating does not occur even if combustion occurs in the boiler, and the safe water level detector 8 is used to activate the water pump.・In addition to providing a common ground terminal for the stop water level detection circuit and the combustion start/stop water level detection circuit, the contact 18 is connected to the water supply pump 6, and the time-limited return contact 21 is connected to the combustion supply valve 20 of the burner 7. A boiler overheat prevention device characterized by: