【Q&A No. 026】2018.01.26
Thread Content
【Q&A No. 026】January 26, 2018: What is three-pulse control of the drum water level? In waste boiler operation, maintaining a stable drum water level is the most important task. The drum water level is affected not only by changes in the water supply volume but also by the steam generation rate; therefore, using a single-parameter control method for regulating the water level is not ideal. It is necessary to employ a method that takes into account the difference between steam and water volumes in order to control the water inflow and achieve a more stable drum water level. This method of controlling the drum water level is commonly referred to as three-pulse control. Three-impulse control is actually cascade control. The drum water level is the main parameter of this control system; that is, in this control loop, the output signal from the water level regulator serves as the setpoint for the cascade regulator, while the difference between the steam flow rate and the feedwater flow rate, after being added together, acts as the measurement value (secondary parameter) for the cascade regulator. As long as there is a deviation between the measured value and the set value, the cascade regulator outputs a signal to control the variation in the inlet flow rate. (Unless otherwise specified, all questions and answers are based on hydrogenation units.) ) Due to the limitations on the number of posts in the “One Question per Day” section, “One Image per Day” has been moved to the registered devices section; you can access it through the directory I posted. For management purposes, if you need to view content from a few days ago, please access it through the summary post below. 2018 Chemical Engineering Technology Training – Daily Questions Summary Thread: https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=18889712018 Registered Equipment Section – Daily Images Summary Thread: https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=1888970
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Water supply to the drum, drum liquid level, steam generation rate of the drum
In drum operation, maintaining drum water level balance is the most important task. The drum water level is affected not only by changes in the feedwater volume but also by the steam generation rate. Therefore, using a single-parameter control method for water level adjustment is not ideal; it is necessary to employ a method that takes into account the difference between steam and water flow rates in order to control the inflow of water and thus maintain a more stable water level in the drum. This method of controlling the drum water level is commonly referred to as three-pulse control. Three-pulse control is actually a form of cascade control, with the drum water level serving as the main parameter in this control system. In this control loop, the output signal from the water level regulator acts as the setpoint for the cascade regulator, while the difference between the steam flow rate and the feedwater flow rate, after being added together, serves as the measurement value (the secondary parameter) for the cascade regulator. As long as there is a deviation between the measured value and the set value, the cascade regulator outputs a signal to control the variation in the inlet flow rate.
A method that utilizes a certain difference between steam and water flow rates is employed to control the feedwater volume, thereby making the drum level more stable. This approach to controlling the drum level is commonly referred to as three-variable control; in fact, it is a form of cascade control. The drum level serves as the primary parameter in this control system. In this control loop, the output signal from the level controller acts as the setpoint for the cascade controller, while the difference between the steam flow rate and the feedwater flow rate, after being added together, functions as the measurement value (secondary parameter) for the cascade controller. As long as there is a deviation between the measured value and the set value, the cascade regulator outputs a signal to control the variation in the inlet flow rate.
In drum operation, maintaining drum water level balance is the most important task. The drum water level is affected not only by changes in the feedwater volume but also by the steam generation rate. Therefore, using a single-parameter control method for water level adjustment is not ideal; it is necessary to employ a method that takes into account the difference between steam and water flow rates in order to control the inflow of water and thus maintain a more stable water level in the drum. This method of controlling the drum water level is commonly referred to as three-pulse control. Three-pulse control is actually a form of cascade control, with the drum water level serving as the main parameter in this control system. In this control loop, the output signal from the water level regulator acts as the setpoint for the cascade regulator, while the difference between the steam flow rate and the feedwater flow rate, after being added together, serves as the measurement value (the secondary parameter) for the cascade regulator. As long as there is a deviation between the measured value and the set value, the cascade regulator outputs a signal to control the variation in the inlet flow rate.
In drum operation, maintaining drum water level balance is the most important task. The drum water level is affected not only by changes in the feedwater volume but also by the steam generation rate. Therefore, using a single-parameter control method for water level adjustment is not ideal; it is necessary to employ a method that takes into account the difference between steam and water flow rates in order to control the inflow of water and thus maintain a more stable water level in the drum. This method of controlling the drum water level is commonly referred to as three-pulse control. Three-pulse control is actually a form of cascade control, with the drum water level serving as the main parameter in this control system. In this control loop, the output signal from the water level regulator acts as the setpoint for the cascade regulator, while the difference between the steam flow rate and the feedwater flow rate, after being added together, serves as the measurement value (the secondary parameter) for the cascade regulator. As long as there is a deviation between the measured value and the set value, the cascade regulator outputs a signal to control the variation in the inlet flow rate.
The three-element control system for drum level refers to the situation where three signals – drum level, steam flow rate, and feedwater flow rate – act on the regulator; in other words, each of the three controlled variables corresponds to one regulator.
In waste boiler operation, maintaining a stable drum water level is the most important task. The drum water level is affected not only by changes in the water supply volume but also by the steam generation rate; therefore, using a single-parameter control method for regulating the water level is not ideal. It is necessary to employ a method that takes into account the difference between steam and water volumes in order to control the water inflow and achieve a more stable drum water level. This method of controlling the drum water level is commonly referred to as three-pulse control. Three-impulse control is actually cascade control. The drum water level is the main parameter of this control system; that is, in this control loop, the output signal from the water level regulator serves as the setpoint for the cascade regulator, while the difference between the steam flow rate and the feedwater flow rate, after being added together, acts as the measurement value (secondary parameter) for the cascade regulator. As long as there is a deviation between the measured value and the set value, the cascade regulator outputs a signal to control the variation in the inlet flow rate.
In drum operation, maintaining drum water level balance is the most important task. The drum water level is affected not only by changes in the feedwater volume but also by the steam generation rate. Therefore, using a single-parameter control method for water level adjustment is not ideal; it is necessary to employ a method that takes into account the difference between steam and water flow rates in order to control the inflow of water and thus maintain a more stable water level in the drum. This method of controlling the drum water level is commonly referred to as three-pulse control. Three-pulse control is actually a form of cascade control, with the drum water level serving as the main parameter in this control system. In this control loop, the output signal from the water level regulator acts as the setpoint for the cascade regulator, while the difference between the steam flow rate and the feedwater flow rate, after being added together, serves as the measurement value (the secondary parameter) for the cascade regulator. As long as there is a deviation between the measured value and the set value, the cascade regulator outputs a signal to control the variation in the inlet flow rate.
In waste boiler operation, maintaining a stable drum water level is the most important task. The drum water level is affected not only by changes in the water supply volume but also by the steam generation rate; therefore, using a single-parameter control method for regulating the water level is not ideal. It is necessary to employ a method that takes into account the difference between steam and water volumes in order to control the water inflow and achieve a more stable drum water level. This method of controlling the drum water level is commonly referred to as three-pulse control. Three-impulse control is actually cascade control. The drum water level is the main parameter of this control system; that is, in this control loop, the output signal from the water level regulator serves as the setpoint for the cascade regulator, while the difference between the steam flow rate and the feedwater flow rate, after being added together, acts as the measurement value (secondary parameter) for the cascade regulator. As long as there is a deviation between the measured value and the set value, the cascade regulator outputs a signal to control the variation in the inlet flow rate.