Pneumatic controller with improved calibration method and reduced influence from external temperature

Abstract

The present invention relates to a pneumatic controller with an improved calibration method and reduced influence from external temperature, the controller constantly maintaining the pressure of a reset bellows so that the balance of the pneumatic controller can be maintained despite temperature changes. The present invention provides the pneumatic controller with an improved calibration method and reduced influence from external temperature, the controller calibrating a bellows-based pneumatic controller that includes a proportional bellows and a reset bellows provided to a water level control system of a feedwater heater of a nuclear power plant, and then performing proportional control and closing with a reset valve so as to maintain the pressure of the reset bellows, and comprising: a pressure regulator capable of regulating the pressure between the reset valve and the reset bellows; a pressure indicator capable of monitoring the pressure of the pressure regulator; and a flow rate control valve for constantly maintaining the pressure of the reset bellows by regulating the rate of flow supplied from the pressure regulator.

Description

Pneumatic controller with improved correction method and external temperature effect

[0001] The present invention relates to a pneumatic controller for controlling the pressure of a feedwater heater of a nuclear power plant.

[0002] Typically, the feedwater heater of a nuclear power plant preheats the temperature of the feedwater during normal operation to increase power generation efficiency. By maintaining the water level of the feedwater heater constant, the latent and sensible heat of the turbine's exhaust steam and condensate are transferred to the feedwater.

[0003] These feedwater heaters consist of a water level control system that maintains the water level at a constant level.

[0004] The water level control system of the feedwater heater controls the water level of the feedwater heater to maintain the water level at the programmed water level setting position so that the heat exchange between the steam and condensate and the feedwater is as designed.

[0005] For example, since the pneumatic controller that controls the water level of a water heater determines the control range by the balance of the force applied to each element and the set value, the change in the state of the bellows is the same as the change in the control range. To calibrate the pneumatic controller, the system is taken out of service, and the bellows-based pneumatic controller is calibrated and then the reset valve is closed (proportional control) and used.

[0006] And when the ambient temperature changes after the system is put into service, the gas inside the reset bellows expands, shifting the control range. As control becomes impossible due to the change in control range, tuning must be performed. This process is repeated until the system reaches its normal operating temperature, including when the ambient temperature changes.

[0007] In the case of a water level controller, the controller can be taken out of service and the chamber filled with water to accurately calibrate the nozzle and flapper. However, if a problem occurs during operation, there is no way to determine the extent of the change in the control range.

[0008] Precision calibration of pneumatic controllers requires adjusting the reset bellows pressure to the set value, setting a reference value, and then performing calibration. However, this adjustment is difficult for users, and precision calibration is impossible during operation.

[0009] And when converting from proportional control to proportional control, the pressure of the reset bellows changes, which changes the reference pressure, resulting in a control range different from the initial calibration, which causes control instability.

[0010] Additionally, if the position of the nozzle or flapper changes during use, it is possible to respond by changing the setting value, but if it goes beyond the setting range, the controller must be stopped and corrected.

[0011] The present invention has been proposed to solve the above-mentioned conventional problems, and the purpose of the present invention is to provide a correction method capable of maintaining the balance of a pneumatic controller even when temperature changes by maintaining the pressure of a reset bellows constant, and a pneumatic controller with improved external temperature influence.

[0012] The pneumatic controller with improved external temperature influence and the correction method proposed by the present invention is a pneumatic controller that corrects a bellows-based pneumatic controller including a proportional bellows and a reset bellows provided in a water level control system of a nuclear power plant feedwater heater, and then proportionally controls and closes the reset valve to maintain the pressure of the reset bellows.

[0013] A calibration method including a pressure regulator capable of controlling the pressure between the reset valve and the reset bellows, a pressure indicator capable of monitoring the pressure of the pressure regulator, and a flow rate control valve for controlling the flow rate supplied from the pressure regulator to maintain the pressure of the reset bellows constant, and a pneumatic controller with improved external temperature influence are provided.

[0014] The above reset valve and reset bellows are connected to a connecting pipe, the pressure regulator is connected to a supply pipe capable of supplying a flow rate to the connecting pipe, and a flow rate control valve is provided in the supply pipe.

[0015] The air pressure controller according to the present invention, which has an improved external temperature influence and a correction method, supplies the flow rate from the pressure regulator by controlling it with a flow rate control valve, thereby maintaining the pressure of the reset bellows constant, thereby maintaining the balance of the air pressure controller even in the event of temperature changes.

[0016] Figure 1 is a configuration diagram of a pneumatic controller with improved external temperature influence and a correction method according to the present invention.

[0017] Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the attached drawings.

[0018] Figure 1 is a configuration diagram of a correction method according to the present invention and a pneumatic controller with improved external temperature influence. The pneumatic controller according to one embodiment of the present invention can be applied to a water level control system of a feedwater heater of a nuclear power plant.

[0019] The water level control system of the feedwater heater maintains constant heat exchange between the feedwater, steam, and condensate during normal operation of the nuclear power plant.

[0020] The pneumatic controller according to the present invention, which has an improved external temperature influence and a correction method, is configured to correct a bellows-based pneumatic controller (6) including a proportional bellows (2) and a reset bellows (4) provided to a water level control system of a nuclear power plant feedwater heater while the system is out of service, and then maintain the pressure of the reset bellows (4) by proportionally controlling and closing it with a reset valve (8).

[0021] After the system is out of service and the air pressure controller (6) is corrected, the reset valve (8) is fixed to the closed state, and a certain pressure is generated between the reset valve (8) and the reset bellows (4) connected to the connecting pipe (L1).

[0022] At this time, the pneumatic controller (6) is a field controller, and there is a difference between the ambient temperature during calibration and the temperature during power plant operation, and accordingly, when the ambient temperature around where the pneumatic controller (6) is installed changes, the gas trapped in the reset bellows (4) expands or contracts depending on the temperature, and the force applied to the beam and flapper (10) also changes.

[0023] The present invention can maintain the balance of the pneumatic controller (6) even when the temperature changes by maintaining the pressure of the reset bellows (4) constant in the above situation.

[0024] That is, the pneumatic controller according to the present invention is provided with a supply pipe (L2) that can supply a flow rate through a pressure regulator (12) in the connection pipe (L1) so as to be able to control the pressure between the reset valve (8) and the reset bellows (4) connected to the connection pipe (L1).

[0025] A pressure indicator (14) and a flow control valve (16) are installed in the supply pipe (L2), so that the supply pressure of the pressure regulator (12) can be monitored through the pressure indicator (14), and the flow rate supplied from the pressure regulator (12) can be controlled by the flow control valve (16) to maintain the pressure of the reset bellows (4) constant.

[0026] Accordingly, even if the ambient temperature of the location where the pneumatic controller (6) is installed changes, the pressure of the reset bellows (4) is kept constant by supplying a flow rate to the connecting pipe (L1) through the pressure regulator (12), so that the balance of the pneumatic controller (6) can be maintained even if a temperature change occurs.

[0027] In this pressure control, the pressure of the pressure regulator (12) must be cut off before setting the reset time (integral control), and if there is a problem with the reset time closed (proportional control) or the control range of the pneumatic controller (6), the reset bellows (4) (reference value) can be changed to maintain a constant output value and the changed control range can be calculated.

[0028] And, if the control range completely deviates from the set range due to fluctuations in the nozzle (18) or beam and flapper (10), the pressure regulator (6) can be used to reset the control range to a usable range.

[0029] Although the preferred embodiments of the present invention have been described above for illustrative purposes, they are not limited thereto, and various modifications may be made within the scope of the claims, the detailed description of the invention, and the attached drawings.

Claims

1. In a pneumatic controller that maintains the pressure of the reset bellows by proportionally controlling and closing the bellows based on a bellows that is provided to a water level control system of a feedwater heater of a nuclear power plant after correcting the bellows and reset bellows, using a reset valve. A calibration method including a pressure regulator capable of controlling the pressure between the reset valve and the reset bellows, a pressure indicator capable of monitoring the pressure of the pressure regulator, and a flow rate control valve for controlling the flow rate supplied from the pressure regulator to maintain the pressure of the reset bellows constant, and an air pressure controller with improved external temperature influence.

2. In claim 1, The reset valve and reset bellows are connected to a connecting pipe, the pressure regulator is connected to a supply pipe that can supply a flow rate to the connecting pipe, and the supply pipe is provided with a flow rate control valve. A pneumatic controller with an improved correction method and an external temperature influence.

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