Drum level control systems are used to control the level of boiling water in boiler drums to provide a constant supply of steam. There are single, two, and three element drum level control systems that vary in their ability to maintain tight control of water level under changing demand conditions. A three element system provides the tightest control and is best for systems with unpredictable steam demands through the use of multiple field devices and controllers to measure steam flow, water level, and feedwater flow and compute setpoints.
This document discusses strategies for variable flow chilled water generation and distribution systems. It compares them to constant flow systems and focuses on large applications like college campuses. Type A central plant configurations are described, where all chilled water generation and pumping is centralized. Advantages include downsized equipment and centralized maintenance, while disadvantages include higher costs. Variable flow systems are recommended over constant flow as they can better match flows to changing loads.
This document summarizes the status of Unit 3 reactor at Fukushima Daiichi nuclear power plant on May 11, 2011 according to TEPCO. It finds that while fresh water is being injected, a closed-loop heat removal system has not been established, and the reactor temperature and pressure remain high. The containment vessel is believed to be damaged based on pressure readings, and intermittent radiation releases continue. Analysis of water from the spent fuel pool detected high levels of cesium-134 and -136, indicating damage to stored fuel rods.
Theoretical analysis of the performance of dual pressure condenser in a therm...IAEME Publication
This document analyzes the theoretical performance of a dual pressure condenser in a thermal power plant compared to a single pressure condenser. It begins with background on condensers and discusses how a dual pressure condenser works with two shells operating at different pressures. It then analyzes design and test parameters for a sample condenser and compares the cooling water flow and heat transfer between a low pressure and high pressure section. The dual pressure condenser is found to improve efficiency by lowering the average turbine back pressure compared to a single pressure condenser.
It is related to piping system in Air-condition(AC) or Room heaters. In this slide, you come to know how heated or cooled water transfer from generater to terminal units(heat exchangers).
This document discusses energy recovery requirements, design, and applications. It covers reasons to use energy recovery like code requirements and economic benefits. It describes ASHRAE standards requiring waterside energy recovery for large facilities. It explains different types of heat recovery chillers and their characteristics. The document discusses waterside heat recovery temperatures and effects on chiller performance for different compressor types. It also covers heat recovery chiller control strategies and system configurations.
Lambda In-Row offers a state-of-the-art row-level cooling solution for data centers using microchannel evaporators. It provides exceptional cooling capacity of up to 180kW/m2 and superior energy efficiency compared to competitors. The small unit outperforms traditional large CRAC units while saving valuable data center space and reducing installation costs.
رسالتي إلى المؤتمر الخامس لحوار تبريد المناطق 2021 في دبي وفرص السوق الحقيقية - م. جمعة
My Message to the 5th DC Dialogue 2021 in Dubai & TRUE Market Opportunity - by Eng. Juma
This document discusses strategies for variable flow chilled water generation and distribution systems. It compares them to constant flow systems and focuses on large applications like college campuses. Type A central plant configurations are described, where all chilled water generation and pumping is centralized. Advantages include downsized equipment and centralized maintenance, while disadvantages include higher costs. Variable flow systems are recommended over constant flow as they can better match flows to changing loads.
This document summarizes the status of Unit 3 reactor at Fukushima Daiichi nuclear power plant on May 11, 2011 according to TEPCO. It finds that while fresh water is being injected, a closed-loop heat removal system has not been established, and the reactor temperature and pressure remain high. The containment vessel is believed to be damaged based on pressure readings, and intermittent radiation releases continue. Analysis of water from the spent fuel pool detected high levels of cesium-134 and -136, indicating damage to stored fuel rods.
Theoretical analysis of the performance of dual pressure condenser in a therm...IAEME Publication
This document analyzes the theoretical performance of a dual pressure condenser in a thermal power plant compared to a single pressure condenser. It begins with background on condensers and discusses how a dual pressure condenser works with two shells operating at different pressures. It then analyzes design and test parameters for a sample condenser and compares the cooling water flow and heat transfer between a low pressure and high pressure section. The dual pressure condenser is found to improve efficiency by lowering the average turbine back pressure compared to a single pressure condenser.
It is related to piping system in Air-condition(AC) or Room heaters. In this slide, you come to know how heated or cooled water transfer from generater to terminal units(heat exchangers).
This document discusses energy recovery requirements, design, and applications. It covers reasons to use energy recovery like code requirements and economic benefits. It describes ASHRAE standards requiring waterside energy recovery for large facilities. It explains different types of heat recovery chillers and their characteristics. The document discusses waterside heat recovery temperatures and effects on chiller performance for different compressor types. It also covers heat recovery chiller control strategies and system configurations.
Lambda In-Row offers a state-of-the-art row-level cooling solution for data centers using microchannel evaporators. It provides exceptional cooling capacity of up to 180kW/m2 and superior energy efficiency compared to competitors. The small unit outperforms traditional large CRAC units while saving valuable data center space and reducing installation costs.
رسالتي إلى المؤتمر الخامس لحوار تبريد المناطق 2021 في دبي وفرص السوق الحقيقية - م. جمعة
My Message to the 5th DC Dialogue 2021 in Dubai & TRUE Market Opportunity - by Eng. Juma
Parametric Studies of an Automotive Air Conditioning System IDES Editor
This document presents a mathematical model and parametric study of an automotive air conditioning system. The model describes the key components of the system - evaporator, condenser, expansion valve, and compressor. Results show the effect of varying condenser inlet air temperature and velocity, as well as compressor speed, on system performance metrics like cooling capacity and coefficient of performance. The study found that performance degraded significantly when refrigerant outlet conditions at the condenser fell into the two-phase region.
This document discusses how to calculate system flow requirements for selecting a pump. It explains that the flow rate in gallons per minute (GPM) depends on the building's heat load and the designed temperature change of the fluid as it travels through the system. It also provides typical designed temperature changes for different system types. The document then presents two formulas for calculating GPM based on the heat load and designed temperature change, with one formula for water and another more general formula for glycol mixtures that accounts for their different properties. Tables with load factors for propylene and ethylene glycol mixtures at different temperatures and concentrations are also included.
This document discusses water to water heat recovery concepts and applications. It begins with an overview of industry trends and topics to be covered, including the basics of heat pumps and various heat recovery arrangements. It then provides examples of heat pump applications for hospital and university preheating, hotel domestic hot water heating, and industrial process water heating. Overall economics are evaluated for different applications. Design considerations like temperature ranges, control schemes, and water quality are also addressed.
Climate control products from Rittal provide concise summaries of key information from technical documents. The summary of the given document is:
[1] Climate control products help control temperature, humidity, dust and vibration inside enclosures to improve reliability of electrical and electronic equipment.
[2] Rittal offers a range of climate control products including air conditioners, filter fans, panel heaters and heat exchangers to maintain optimal internal enclosure temperatures.
[3] Rittal's sizing software helps select the right climate control product by calculating heat loads, temperature differences and required cooling capacity.
This document summarizes a technical seminar on thermosyphon reboilers and their operational characteristics. It begins with an introduction to reboilers and thermosyphon reboilers. It then discusses the working principles and types of thermosyphon reboilers, including vertical and horizontal designs. The document reviews the operational characteristics of thermosyphon reboilers and how they are influenced by factors like temperature difference, operating pressure, and pipe diameter. It also compares advantages and disadvantages of vertical and horizontal designs. Finally, it discusses common industrial applications of thermosyphon reboilers and concludes with a summary of key points and references.
Water Management in Thermal Power Plants .pdfeldoctol
The document discusses water management in thermal power plants. It describes the various uses of cooling water in power generation, including condensing turbine exhaust steam and auxiliary cooling. It also discusses sources of water, types of cooling water systems like once-through, closed re-circulating, and open re-circulating systems. Key terms associated with cooling towers like evaporation, drift, blowdown, and makeup water are also defined. Factors that can lead to scaling and corrosion in cooling water systems are explained.
This document presents a dissertation submitted by Md. Khurshid Alam to the Department of Mechanical Engineering at Al-Falah University in partial fulfillment of the requirements for a Master of Technology degree in Thermal Engineering. The dissertation analyzes the life cycle of split and multi-split variable refrigerant flow air conditioning systems through a case study. It includes chapters on the introduction, literature review, methodology, life cycle analysis and references. Tables and figures presented include component lists, schematics of VRF systems, load calculations, and economic analyses. The aim is to design an energy efficient and cost effective HVAC system for a building through life cycle analysis of VRF options.
This document provides guidelines for connecting new or renovated buildings to the centralized campus chilled water plants. Buildings can connect directly to the primary chilled water loop or indirectly via a plate and frame heat exchanger. For direct connections, the chilled water supply is 42°F with a 16°F delta T and the system pressure is set at 80 PSIG. Indirect connections are required if a building's static pressure exceeds this. Guidelines are provided for pumps, valves, meters, and other components as well as testing, balancing, and commissioning requirements to ensure building systems interface properly with the central plants.
The presentation is about the boiler drum's water level control, which is used on the ship for generating the steam. The presentation briefs about some controls used overboard to maintain the level inside the boiler for continuous steam supply.
Importance of three elements boiler drum level control and its installation i...ijics
Conversion of water into steam is the primary function of a utility boiler. The steam pressure is used to turn
a steam turbine thus, generating electricity. Within the boiler drum there exists a steam/water interface.
Boiler steam drum water level is one of the important parameters of power plant that must be measured
and controlled. For safe and efficient boiler operation, a constant level of water in the boiler drum is
required to be maintained. Too low water level may cause damage boiler tube by overheating. On the other
hand too high drum water level leads to improper function of separators, difficulty in temperature
controlling and damage in superheater tubes. Turbine may also be damaged by moisture or water
treatment chemicals carryover. The amount of water entering the boiler drum must be balanced with the
amounts of steam leaving to accomplish the constant water level in the drum. Therefore it is extremely
important to have the knowledge of the operating principles, installation requirements, strength and
weaknesses of drum water level control system. Ignoring these considerations can result in misapplication,
frequent maintenance, unsafe operation and poor instrument as well as system performance. In this paper
design aspects and installation requirements of boiler drum level control are discussed for safe and
economic operation.
This document discusses instrumentation and controls for boiler plants. It describes the key inputs and outputs to a boiler control system for maintaining energy and mass balance. The document outlines several basic control loops for fuel, combustion air, and feedwater. It then provides more details on combustion control systems, including different control schemes and hardware. Finally, it discusses various feedwater control systems from single element to multi-element approaches for maintaining proper water levels over a range of boiler loads.
Flow Control Using Variable Frequency Drive In Water Treatment Process of Dei...IJTET Journal
The document discusses using a variable frequency drive instead of a control valve to control the flow of chemicals in a water treatment process. By controlling the speed of an induction motor with a variable frequency drive based on inlet water flow, the chemical dosage flow can be precisely controlled to improve water treatment efficiency. Vector control is implemented to control the induction motor speed by measuring motor quantities, transforming currents to reference frames, and separately controlling the flux and torque producing current components.
This slide expain on shrink and swell phenomena in Boiler operation. It also talk about three element control principle applied to mitigite these effect
Boiler Drum level measurement in Thermal Power StationsManohar Tatwawadi
The paper describes the basics of Boiler Drum water Level measurement in a Thermal Power Station. The Single element and three element control has been described in a very simple manner. Useful for the Thermal Engineers
This document discusses different methods of boiler feedwater control systems. Single element control uses drum level measurement alone and is the simplest method. Two element control adds steam flow measurement to provide feedforward control. Three element control further adds feedwater flow measurement, providing feedback on the controlled variable to improve control over load changes. The document describes the control loops and components used in these systems.
This document summarizes flooding in a distillation column. Distillation separates mixtures based on differences in volatility through boiling and vaporization. Flooding occurs when excessive vapor flow carries liquid up the column, reducing efficiency. It can be detected by increases in differential pressure and decreases in separation. The document describes an experiment where a distillation column's reboiler heat was incrementally increased. Measurements from pressure transmitters showed that filtering and monitoring standard deviation of the pressure signal could provide early detection of the column approaching flooding. This allows operators to make adjustments and prevent loss of separation and reduced efficiency.
Electrical thermal plant boiler temperature and water level monitoringEcway Technologies
This document discusses monitoring the water level and temperature in a boiler system for a process plant. Maintaining the proper water level and temperature is critical, as too low or high of a level can damage the boiler or turbines. The project aims to provide partial automation and manual supervision of these values using a microcontroller-based system. Sensors measure the water level and temperature, which are converted to digital values and displayed on an LCD screen. An alarm will also sound if the liquid overflows.
Electrical thermal plant boiler temperature and water level monitoringEcwaytech
This document discusses monitoring the water level and temperature in a boiler system for a process plant. Maintaining the proper water level and temperature is critical, as too low or high of a level can damage the boiler or turbines. The water level is difficult to control due to nonlinearities and other factors. The goal of this project is to provide partial automation and manual supervision of the water level and temperature using a microcontroller-based system that converts analog sensor readings to digital values for display on an LCD screen and issues alerts if the levels change too much.
Electrical thermal plant boiler temperature and water level monitoringEcwayt
This document discusses monitoring the water level and temperature in a boiler system for a process plant. Maintaining the proper water level and temperature is critical, as too low or high of a level can damage the boiler or turbines. The water level is difficult to control due to nonlinearities and other factors. The goal of this project is to provide partial automation and manual supervision of the water level and temperature using a microcontroller-based system that converts analog sensor readings to digital values for display on an LCD screen and activates a buzzer for alerts.
The primary function of a utility boiler is to convert water into steam to be used by a steam turbine/ generator in producing electricity. The boiler consists of a furnace, where air and fuel are combined and burned to produce combustion gases, and a feedwater tube system, the contents of which are heated by these gases.
Parametric Studies of an Automotive Air Conditioning System IDES Editor
This document presents a mathematical model and parametric study of an automotive air conditioning system. The model describes the key components of the system - evaporator, condenser, expansion valve, and compressor. Results show the effect of varying condenser inlet air temperature and velocity, as well as compressor speed, on system performance metrics like cooling capacity and coefficient of performance. The study found that performance degraded significantly when refrigerant outlet conditions at the condenser fell into the two-phase region.
This document discusses how to calculate system flow requirements for selecting a pump. It explains that the flow rate in gallons per minute (GPM) depends on the building's heat load and the designed temperature change of the fluid as it travels through the system. It also provides typical designed temperature changes for different system types. The document then presents two formulas for calculating GPM based on the heat load and designed temperature change, with one formula for water and another more general formula for glycol mixtures that accounts for their different properties. Tables with load factors for propylene and ethylene glycol mixtures at different temperatures and concentrations are also included.
This document discusses water to water heat recovery concepts and applications. It begins with an overview of industry trends and topics to be covered, including the basics of heat pumps and various heat recovery arrangements. It then provides examples of heat pump applications for hospital and university preheating, hotel domestic hot water heating, and industrial process water heating. Overall economics are evaluated for different applications. Design considerations like temperature ranges, control schemes, and water quality are also addressed.
Climate control products from Rittal provide concise summaries of key information from technical documents. The summary of the given document is:
[1] Climate control products help control temperature, humidity, dust and vibration inside enclosures to improve reliability of electrical and electronic equipment.
[2] Rittal offers a range of climate control products including air conditioners, filter fans, panel heaters and heat exchangers to maintain optimal internal enclosure temperatures.
[3] Rittal's sizing software helps select the right climate control product by calculating heat loads, temperature differences and required cooling capacity.
This document summarizes a technical seminar on thermosyphon reboilers and their operational characteristics. It begins with an introduction to reboilers and thermosyphon reboilers. It then discusses the working principles and types of thermosyphon reboilers, including vertical and horizontal designs. The document reviews the operational characteristics of thermosyphon reboilers and how they are influenced by factors like temperature difference, operating pressure, and pipe diameter. It also compares advantages and disadvantages of vertical and horizontal designs. Finally, it discusses common industrial applications of thermosyphon reboilers and concludes with a summary of key points and references.
Water Management in Thermal Power Plants .pdfeldoctol
The document discusses water management in thermal power plants. It describes the various uses of cooling water in power generation, including condensing turbine exhaust steam and auxiliary cooling. It also discusses sources of water, types of cooling water systems like once-through, closed re-circulating, and open re-circulating systems. Key terms associated with cooling towers like evaporation, drift, blowdown, and makeup water are also defined. Factors that can lead to scaling and corrosion in cooling water systems are explained.
This document presents a dissertation submitted by Md. Khurshid Alam to the Department of Mechanical Engineering at Al-Falah University in partial fulfillment of the requirements for a Master of Technology degree in Thermal Engineering. The dissertation analyzes the life cycle of split and multi-split variable refrigerant flow air conditioning systems through a case study. It includes chapters on the introduction, literature review, methodology, life cycle analysis and references. Tables and figures presented include component lists, schematics of VRF systems, load calculations, and economic analyses. The aim is to design an energy efficient and cost effective HVAC system for a building through life cycle analysis of VRF options.
This document provides guidelines for connecting new or renovated buildings to the centralized campus chilled water plants. Buildings can connect directly to the primary chilled water loop or indirectly via a plate and frame heat exchanger. For direct connections, the chilled water supply is 42°F with a 16°F delta T and the system pressure is set at 80 PSIG. Indirect connections are required if a building's static pressure exceeds this. Guidelines are provided for pumps, valves, meters, and other components as well as testing, balancing, and commissioning requirements to ensure building systems interface properly with the central plants.
The presentation is about the boiler drum's water level control, which is used on the ship for generating the steam. The presentation briefs about some controls used overboard to maintain the level inside the boiler for continuous steam supply.
Importance of three elements boiler drum level control and its installation i...ijics
Conversion of water into steam is the primary function of a utility boiler. The steam pressure is used to turn
a steam turbine thus, generating electricity. Within the boiler drum there exists a steam/water interface.
Boiler steam drum water level is one of the important parameters of power plant that must be measured
and controlled. For safe and efficient boiler operation, a constant level of water in the boiler drum is
required to be maintained. Too low water level may cause damage boiler tube by overheating. On the other
hand too high drum water level leads to improper function of separators, difficulty in temperature
controlling and damage in superheater tubes. Turbine may also be damaged by moisture or water
treatment chemicals carryover. The amount of water entering the boiler drum must be balanced with the
amounts of steam leaving to accomplish the constant water level in the drum. Therefore it is extremely
important to have the knowledge of the operating principles, installation requirements, strength and
weaknesses of drum water level control system. Ignoring these considerations can result in misapplication,
frequent maintenance, unsafe operation and poor instrument as well as system performance. In this paper
design aspects and installation requirements of boiler drum level control are discussed for safe and
economic operation.
This document discusses instrumentation and controls for boiler plants. It describes the key inputs and outputs to a boiler control system for maintaining energy and mass balance. The document outlines several basic control loops for fuel, combustion air, and feedwater. It then provides more details on combustion control systems, including different control schemes and hardware. Finally, it discusses various feedwater control systems from single element to multi-element approaches for maintaining proper water levels over a range of boiler loads.
Flow Control Using Variable Frequency Drive In Water Treatment Process of Dei...IJTET Journal
The document discusses using a variable frequency drive instead of a control valve to control the flow of chemicals in a water treatment process. By controlling the speed of an induction motor with a variable frequency drive based on inlet water flow, the chemical dosage flow can be precisely controlled to improve water treatment efficiency. Vector control is implemented to control the induction motor speed by measuring motor quantities, transforming currents to reference frames, and separately controlling the flux and torque producing current components.
This slide expain on shrink and swell phenomena in Boiler operation. It also talk about three element control principle applied to mitigite these effect
Boiler Drum level measurement in Thermal Power StationsManohar Tatwawadi
The paper describes the basics of Boiler Drum water Level measurement in a Thermal Power Station. The Single element and three element control has been described in a very simple manner. Useful for the Thermal Engineers
This document discusses different methods of boiler feedwater control systems. Single element control uses drum level measurement alone and is the simplest method. Two element control adds steam flow measurement to provide feedforward control. Three element control further adds feedwater flow measurement, providing feedback on the controlled variable to improve control over load changes. The document describes the control loops and components used in these systems.
This document summarizes flooding in a distillation column. Distillation separates mixtures based on differences in volatility through boiling and vaporization. Flooding occurs when excessive vapor flow carries liquid up the column, reducing efficiency. It can be detected by increases in differential pressure and decreases in separation. The document describes an experiment where a distillation column's reboiler heat was incrementally increased. Measurements from pressure transmitters showed that filtering and monitoring standard deviation of the pressure signal could provide early detection of the column approaching flooding. This allows operators to make adjustments and prevent loss of separation and reduced efficiency.
Electrical thermal plant boiler temperature and water level monitoringEcway Technologies
This document discusses monitoring the water level and temperature in a boiler system for a process plant. Maintaining the proper water level and temperature is critical, as too low or high of a level can damage the boiler or turbines. The project aims to provide partial automation and manual supervision of these values using a microcontroller-based system. Sensors measure the water level and temperature, which are converted to digital values and displayed on an LCD screen. An alarm will also sound if the liquid overflows.
Electrical thermal plant boiler temperature and water level monitoringEcwaytech
This document discusses monitoring the water level and temperature in a boiler system for a process plant. Maintaining the proper water level and temperature is critical, as too low or high of a level can damage the boiler or turbines. The water level is difficult to control due to nonlinearities and other factors. The goal of this project is to provide partial automation and manual supervision of the water level and temperature using a microcontroller-based system that converts analog sensor readings to digital values for display on an LCD screen and issues alerts if the levels change too much.
Electrical thermal plant boiler temperature and water level monitoringEcwayt
This document discusses monitoring the water level and temperature in a boiler system for a process plant. Maintaining the proper water level and temperature is critical, as too low or high of a level can damage the boiler or turbines. The water level is difficult to control due to nonlinearities and other factors. The goal of this project is to provide partial automation and manual supervision of the water level and temperature using a microcontroller-based system that converts analog sensor readings to digital values for display on an LCD screen and activates a buzzer for alerts.
The primary function of a utility boiler is to convert water into steam to be used by a steam turbine/ generator in producing electricity. The boiler consists of a furnace, where air and fuel are combined and burned to produce combustion gases, and a feedwater tube system, the contents of which are heated by these gases.
1. This document presents a functional approach to flow assurance analysis for deepwater field developments.
2. The approach involves systematically reviewing all operating conditions, including steady state, start-up, shut down, and non-producing periods to ensure fluid properties remain within allowable pressure and temperature ranges throughout.
3. Multiphase flow simulations and thermal analysis are used to model critical conditions like hydrate formation, wax deposition, and assess insulation needs under different scenarios.
This document discusses cascade control in a power plant boiler. Cascade control uses two controllers, a master and slave, to more precisely control a process. In a boiler, drum level is controlled using cascade control with drum level as the master controller and feedwater flow as the slave controller. This provides improved control over drum level as steam load changes are compensated for through remote manipulation of the feedwater flow setpoint. Benefits of cascade control include reduced lag time and improved dynamic response, while drawbacks include increased complexity, cost, and controller tuning difficulty.
International Journal of Engineering and Science Invention (IJESI) is an international journal intended for professionals and researchers in all fields of computer science and electronics. IJESI publishes research articles and reviews within the whole field Engineering Science and Technology, new teaching methods, assessment, validation and the impact of new technologies and it will continue to provide information on the latest trends and developments in this ever-expanding subject. The publications of papers are selected through double peer reviewed to ensure originality, relevance, and readability. The articles published in our journal can be accessed online.
This document discusses boiler blowdown analysis conducted on a 33TPH water tube boiler in an industrial plant. Boiler blowdown involves intentionally removing water from a boiler to control the concentration of dissolved solids as water evaporates during steam generation. Too high a concentration can cause problems like carryover of water in steam. The analysis found that the boiler's total dissolved solids level of 572ppm on average was lower than the recommended maximum of 2200ppm, due to the manual blowdown control system being unable to precisely adjust to varying conditions. Installing an automatic blowdown control system based on continuous water quality monitoring could help maintain optimal solids levels while reducing blowdown rates and saving energy.
This document describes the closed loop control system used for boiler drum level control. It uses a three element control approach with drum level, feedwater flow, and main steam flow as process variables. During startup, a single 30% capacity feedwater control valve (FCV-101) is used to maintain drum level setpoint. At 30% load, control switches to two 100% capacity main feedwater valves (FCV-102) controlled via a three element algorithm. Drum level is measured by three level transmitters and averaged for input to the level controller (LIC-101). The controller output is summed with steam flow and used to set the remote setpoint for FIC-101, which controls FCV-102 position
TECHNIQUE TO REDUCE DUMP LOAD IN ISOLATED HYDRO POWER PLANT BY LOAD FREQUENCY...Journal For Research
In this paper, a new technique for load frequency control is adopted In general the frequency is controlled by using a dump load, whose rating is equal to the rated power output of the plant. The new scheme proposed reduces the size of the dump load by controlling input power of the hydro power plant using on/off controls. The water flowing through the penstock is rerouted in smaller pipes, two or three ï¬Âtted with motor operated valves. The opening or closing of the valves is achieved by on/off controls. The on/off control linearly raises or lowers the generation. A transfer function model for the system is developed with an on/off control logic. Finally, system transient’s performance is compared for the case of two –pipe (50% dump load) and the three-pipe (30% dump load).
1. Application Drum Level Control Systems
Guide in the Process Industries
Drum Level Control Systems are used extensively throughout the process industries and the Utilities
to control the level of boiling water contained in boiler drums on process plant and help provide a
constant supply of steam.
If the level is too high, flooding of steam purification equipment can occur.
If the level is too low, reduction in efficiency of the treatment and recirculation function.
Pressure can also build to dangerous levels.
A drum level control system tightly controls the level whatever the disturbances, level change, increase/
decrease of steam demand, feedwater flow variations.
Suitable ABB products for use in Drum Level Control systems are:
• COMMANDER 300 Controller (for single-element systems)
• COMMANDER 1900 Controller (for single, two and three-element systems)
• MOD 30ML (for single, two and three-element systems)
• MODCELL
ABB Instrumentation
2. Drum Level Control Systems – in the Process Industries
In the process industries, boiling water to make steam is a very important procedure.
Drum Level Control The control of water level is a major function in this process and it is achieved
through a water steam interface established in a cylindrical vessel called the drum
Systems which is usually lying on its side and located near the top of the boiler.
Providing tight water level control in a drum is accomplished by utilizing one of
three types of drum level control: single-element, two-element, or three-element. All
three types of control strategies can be provided for utilizing one MOD 30ML
Controller and supporting field products such as ABB electronic differential pressure
transmitters (type 621D) and WEDGE™ flow elements.
Maintaining the correct water level in the drum is critical for many reasons. A water
The Boiler Drum level that is too high causes flooding of the steam purification equipment; resulting
in the carry over of water and impurities into the steam system. A water level that is
too low results in a reduction in efficiency of the treatment and recirculation function.
It can even result in tube failure due to overheating from lack of cooling water on the
boiling surfaces. Normally drum level is expected to be held within 2 to 5cm of the
set-point with some tolerance for temporary load changes.
Under boiling conditions, steam supporting field products such as bubbles exist
Components Affecting below the water/steam level interface. These bubbles have volume and therefore
displace water to create a misrepresentation of the true water level in the drum.
Drum Water Level Another effect upon drum level is pressure in the drum. Because steam bubbles
compress under pressure (if the drum pressure changes due to load demands), the
steam bubbles expand or contract respective to these pressure changes. A higher
steam demand will cause the drum pressure to drop, and the steam bubbles to
expand to give the appearance of a water level higher than it truly is. This fictitious
higher water level causes the feedwater input to be shut down at a time when more
water is really required. A surge in water level as a result of the drum pressure
decreasing is called 'swell'. A water level decrease due to drum pressure increase
is called 'shrink'.
Figure 1 depicts three types of drum level control strategies with typical applications
Level Control for each. While single-element drum level control is acceptable for steady boiler
load conditions; as load changes become more frequent, unpredictable, or severe;
Strategies this type of level control cannot respond quickly enough to compensate. More
information must be included and processed to predetermine the amount of water
to be added to the drum to compensate for load changes. The addition of elements
(flow and transmitter devices) enables the controller to predict the amount of water
added to the drum to maintain drum level set-point.
System Classification Load Change Capabilities Typical Applications
Magnitude Rate
Single-element Moderate Slow Institutional and industrial heating plants
Steady process conditions
Two-element Moderate Moderate Industrial plants with essentially continuous
type processes and good feedwater
pressure regulation
Three-element Wide Fast Combination of batch and continuous type
operations such that plant steam load
characteristics varies continuously and
usually unpredictably. Most industrial power
applications fall into this category.
Figure 1 Application Chart for Drum Level Control System
3. Drum Level Control Systems – in the Process Industries
Figure 2 depicts the control scheme for single-element drum level control. In this
Single-Element Drum configuration, only the water level in the drum is being measured (hence the term "
single element" ) . LT- 1 is an electronic differential pressure transmitter with a high
Level Control static pressure range. The high side of the transmitter is connected to the bottom of
the drum. Because of the drum's static pressure, the low side of the transmitter is
connected to the top of the drum above the water/steam interface. This provides a
reference for the transmitter by cancelling the static pressure effect and allowing
only the water hydrostatic head to be measured.
A constant head reservoir is required to maintain a consistent head in the reference
leg of the transmitter. This is often referred to as a ''wet leg" The output of the electronic
DP transmitter is the process Input for the MOD 30ML Controller, (LC-1), and the
output is then compared to a drum level set-point. Any discrepancy between set-
point and drum level causes an output from the MOD 30ML controller in
compensation. Because controller action is reverse, as the drum level Increases, a
resultant output signal will decrease to close the feedwater control valve. The output
of the Controller is fed to the feedwater control valve (FCV-1). If the feedwater valve
is pneumatic, an lP (current-to-pressure) converter is required to change the
Controller current output to accommodate the pneumatic valve.
Note that the response from the controller to the feedwater control valve is reactive;
i.e. feedwater is added only in response to a drop in drum level. This type of control
is acceptable if steam load changes are not dramatic because the controller can
respond well to steady demands. In applications where steam load changes become
frequent and unpredictable, a reactive strategy is better suited. This type of system
requires more field devices for input.
Steam
LX Constant Head
1 Reservoir
Water/Steam
Interface
LT Drum Level
1 Transmitter
Water with
Steam Bubbles LC Drum Level
Boiler 1 Controller
Drum FCV
1 FK
1 A
M
Feedwater
Feedwater
Control
Valve
Figure 2 Single-element drum level control system
4. Drum Level Control Systems – in the Process Industries
A two-element drum level control system is capable of providing close adherence
Two-Element Drum of drum level to its set-point under steady-state conditions as well as being capable
of providing the required tight control during a transient. Its performance during
Level Control System transient conditions permits its use on many industrial boiler applications. Such
applications are characterized by adequately-sized drums used with load changes
of moderate rate and degree. These characteristics are usually found in plants with
continuous-type processes, and those with mixed heating and processing demands.
Caution should be exercised in its use on systems without reasonably constant
feedwater pressure.
The term 'two-element' is derived from two variables: steam flow and drum level
influence on the feedwater valve position. It is often classified as a combination
'feed-forward-feedback' system because the steam flow demand is fed forward as
the primary index of the feedwater valve position. The drum level signal becomes
the feedback which is used to constantly trim the accuracy of the feed-forward
system and provide final control of the water/steam interface in the drum.
Refer to Figure 3 for the control scheme of a two-element drum level control. Note
the left side of the doted line is identical to that used in single-element control.
Additional equipment required for two-element drum level control consists of a steam
flow measuring device, a differential pressure transmitter, a square root extractor, a
feedwater flow computer and a feedwater flow mode transfer station. At first this
may appear like a large investment in order to gain stable drum level control, but as
you will see this is not necessarily true.
How it works:
Steam flow is measured by the steam flow transmitter (FT-1), its signal is fed to the
feedwater flow computer (FC-1) after processing through the square root extractor
(FY-1). As in the single-element level control, the drum level is measured by the
level transmitter (LT-1) and its signal is transmitted to the drum level controller (LC-
1). In the drum level controller, the process signal is compared to the drum level set-
point, where a required corrective output signal to maintain the drum level is
produced. This corrective signal is sent to the feedwater flow computer. The
feedwater flow computer combines the signal from the two variables, and produces
an output signal to the feedwater control valve (FCV-1). Auto/Manual transfer of the
feedwater control valve is accomplished via FK-1.
Nearly all of the load change work is done by the feed-forward system, for example,
a pound of feedwater change is made for every pound of steam flow change. The
drum level control system is used for compensation only.
It is expected that the drum level will be maintained very closely to the set-point
value. This is true in spite of the low-to-moderate volume/throughput ratio and a
wide operating range. As a result, integral response (reset) is a necessary function
in the drum level controller.
Using one MOD 30ML Controller, four of the functions in the two-element control
scheme are accomplished: level control (LC-1), square root extraction (FY-1),
feedwater flow computation (FC-1), and feedwater flow mode transfer (FK-1). The
MOD 30ML Controller is a multi-functional controller providing level control for
LC-1. Utilizing the linearization block in the ML will provide the required square root
function to obtain a linear signal from the steam flow transmitter. A math block in the
Controller enables feedwater flow computations. Finally, a feedwater flow transfer
5. Drum Level Control Systems – in the Process Industries
station is easily provided for with an operator-accessible Auto/Manual button on the
…Two-Element Drum Controller display. Once in manual, the controller output is ramped up or down by
an operator using keys on the controller display. Should a totalized steam flow be
Level Control System required, the
MOD 30ML Controller provides an eight-digit display of the totalized value.
FT-1 is an ABB electronic transmitter providing accuracy of 0.2% and is rugged
enough to handle static pressures up to 6000 PSI.
FE
1
Steam
Constant Head
Reservoir
Steam
LX
FT Flow
1
1 Transmitter
Drum Level FY √ Square Root
1 Extractor
Water/Steam Transmitter
Interface LT
1
Drum Level
Controller
Water with LC FC ∑ Feedwater Flow
1 1
Steam Bubbles Boiler Computer
Drum A
FCV
1
M FK Feedwater Flow
1 Mode Transfer
Station
Feedwater
Feedwater
Control
Valve
Figure 3 Two-element drum level control system
6. Drum Level Control Systems – in the Process Industries
In most drum level control applications, the two-element drum level control will
Three-Element Drum maintain the required water/steam interface level – even under moderate load
changes. However, If an unstable feedwater system exists exhibiting a variable
Level Control System feed header-to-drum pressure differential, or if large unpredictable steam demands
are frequent, a three-element drum level control scheme should be considered. As
implied from the previous information, this control strategy supplies control of
feedwater flow in relationship to steam flow.
The performance of the three-element control system during transient conditions
makes it very useful for general industrial and utility boiler applications. It handles
loads exhibiting wide and rapid rates of change. Plants which exhibit load
characteristics of this type are those with mixed, continuous, and batch processing
demands. It is also recommended where normal load characteristics are fairly steady;
but upsets can be sudden, unpredictable and/or a significant portion of the load.
How it works:
Figure 4 shows the control scheme for three-element drum level control. To the left
of the dotted line, the instrumentation is the same as that for the two-element drum
level control, with one exception: the output of the feedwater flow computer now
becomes the set-point of the feedwater flow controller (FIC-2). Equipment required
to complete our three-element drum level control scheme includes an additional
flow device (FE-2) and differential pressure transmitter (FT-2).
The area to the left of the dotted line in figure 4 functions the same as that of a two-
element drum level control. We can pick up the operation for this scheme where the
output signal of the feedwater flow computer (the combination of steam flow and
drum level) enters the feedwater controller (FIC-2).
This in effect becomes the set-point to this controller. Feedwater flow Is measured
by the transmitter (FT-2). The output signal of the feedwater flow transmitter is
linearized by the square root extractor, (FY-2). This signal is the process variable to
the feedwater controller and is compared to the output of the feedwater flow computer
(set-point). The feedwater flow controller produces the necessary corrective signal
to maintain feedwater flow at its set-point by the adjustment of the feedwater control
valve (FCV-1).
As in the two-element drum level control scheme, nearly all of the work necessary to
compensate for load change is done by the feed-forward system (i.e. a pound of
feedwater change is made for every pound of steam flow change). The drum level
portion of the control scheme is used only in a compensating role. Despite low-to-
moderate volume/ throughput ratio and a wide operating range, it is expected the
drum level will be maintained very close to set-point. Achieving this requires use of
the integrating response and reset in both the drum level and feedwater controllers.
This application may suggest that an additional controller is required for the feedwater
flow controller, however this Is not true. The MOD 30ML Controller is a multi-loop
unit. An easily-configured feed-forward command in the MOD 30ML means no
additional wiring is required to have the drum level controller and feedwater controller
working together. Feedwater flow computations are effortlessly done in the maths
block of the controller, all square root functions are performed within.
The feedwater flow element (FE-2), is an ABB WEDGE unit. A reliable, rugged, yet
accurate measuring device that will be in service for many years. Many models
include the option of mounting the transmitter on the WEDGE itself, thus eliminating
the need for expensive lead lines, valves and flanges.
7. Drum Level Control Systems – in the Process Industries
The feedwater flow transmitter (FT-2), is an ABB electronic differential pressure
…Three-Element Drum transmitter. If the system is appropriately designed. FT-1. FT-2, and LT-1 may be the
same type of transmitter. This means stocking only one type of transmitter In the
Level Control System case of a transmitter failure.
FE
1
Steam
Steam Constant Head
Reservoir
LX
FT Flow
1
1 Transmitter
Drum Level FY √ Square Root √
1 FY
Water/Steam Transmitter Extractor
Interface LT 2
1
Drum Level ∑
Controller
Water with LC FY FIC FT Flow
Steam Bubbles Boiler 1 3 2 2 Transmitter
Feedwater Flow
Drum Computer FCV A
1 M
FK Feedwater Flow
1 Mode Transfer
Station
Feedwater
FE Feedwater Flow
Feedwater 2
Control Element
Valve
Figure 4 Three-element drum level control system