com Abstract: Now a day’s demandfor power generation is increasing. Therefore control system requirements arealso increasing. In this paper boiler is operated using many control strategiesso that resultant operation will be practically implemented for industrialpurpose. In this experiment the electrically heated boiler and pipe in pipetype heat exchanger is used.
Electrically heated boilers make use of electriccurrent running through a heating element to create heat, to boil water intohigh-temperature and high-pressure steam. Totest better Controllability pipe in pipe type counter current heat exchanger.During first phase the installation, calibration and testing for alltransmitters and actuators are completed. Bymaking a system available to programming logic controllers, distributed controlsystem as well as to simulation softwares phase. Multiple control ends areachieved.
Pilot plants are controlled using user friendly frontends. In thisdifferent control strategies are used such as PLC,DCS, MATLAB as well as virtual PLC and DCS with local controllerswithout any compromise in safety.Keywords: Pilot Plant, Boiler, Heat exchanger, Programming logic controller.INTRODUCTION Automation is the use of machines, control systems andinformation technologies to optimize productivity in the production of goodsand services. Beyond that possible with current human labor levels so as torealize economies of scale, and realize predictable quality levels.10In the presentworld of rapid technological changes there is an urgent demand for the verybest quality products . The automation and simulation of this project is beingdone with the help of PLC.
Programmable logic controllers have been an integralpart of factory automation as well as industrial process control.9As we knowpower demands are increasing unit operations should be handled with good amountof efficiency and control to save energy and enhance production quality andquantity. Controllers like Programmable Logic Controllers, Distributed ControlSystems and simulation tools and test control strategies are available tocontrol pilot plants. We have comparative studies of different class of controlstrategies and different class of controllers. We are having two pilot plantsboiler and heat exchanger. The boiler is an electrical boiler operated at3.5bar pressure at 1350C temperature giving steam of 30kg=hr.
This Steam isutilized in Heat Exchanger which is of pipe in pipe type and operated incounter current flow of fluids .Both pilot plants are well equipped withtransmitters and actuators of industry grade. The boiler drum contains waterwhich is electrically heated with a PWM controller and generates steam at 4 barand 144C. The water for heating is pumped from a boiler feed water tank using apositive displacement pump. BLOCK DIAGRAM Fig.1 Block diagram of Boiler and HeatExchanger pilot plant The boiler drummade up contains water which is electrically heated with a PWM controller andgenerates steam at 4 bar and 144C.
The water for heating is pumped from aboiler feed water tank using a positive displacement pump.The steamgenerated Flows towards the heat exchanger through an equal percentage globevalve which controls the steam flow.The heatexchanger being of tubular counter flow type, water to be heated is pumped froma cold water tank from the other end using a centrifugal pump. The condensateformed in the heat exchanger during heat transfer is collected in a separatecondensate tank. The hotwater is collected in hot water tank which also be either mixed in the coldwater tank or can be added partially/fully to the feed to the boiler to changethe feed water temperature. Boiler and Heatexchanger Fig.2shows the working Automation of Boiler and heat Exchanger pilot plant in thedepartment of Instrumentation & Control College of Engineering Pune. Fig: 2 Workingof Boiler and Heat Exchanger pilot PlantBoilerA boiler is a closed vessel usually made of stainlesssteel in which water or other fluid is heated.
Electric steam boilers use resistance- orimmersion-type heating elements.Heat ExchangerA heat exchanger is a piece of equipment built forefficient heat transfer from one medium to another. The media may be separatedby a solid wall, so that they never mix, or they may be in direct contact.There are two primary classifications of heat exchangers according to their flowarrangement. In parallel flow heat exchangers, the two fluids enter the exchangerat the same end, and travel in parallel to one another to the other side. Incounter flow heat exchangers the fluids enter the exchanger from opposite ends.
Sensors andtransmittersThe transducer measures a process variable while thetransmitter transmits the data to the controller as a 4-20 mA current signal.Final controlelementsThe final control element adjusts the amount of energy/massthat goes into or out from process as commanded by the controller. Followingare the final control elements used in the plant:a. Positive displacement pump for feeding boiler feedwater : The speed of the motor and in turn feed flow is changed using variablefrequency drive.b. Centrifugal pump for feeding cold water to heatexchanger: The speed of the motor and in turn feed flow is changed usingvariable frequency drive.
c. Equal percentage globe control valve for manipulatingsteam flow current signal from controller is converted to pneumatic signalusing an I/P converter which decides the valve opening.d. Solenoid valve which has 2 positions (open or close):Opening of the valve allows mixing of hot water with the cold water feed forheat exchanger as well as changing the boiler feed water temperature.
Safety componentsThese components ensure process safety whichgenerally refers to the prevention of unintentional releases of chemicals,energy, or other potentially dangerous materials (including steam) during thecourse of process that can have a serious effect to the plant and environment.Process safety involves, for example, the prevention of leaks, spills,equipment malfunction, over-pressures, over-temperatures, corrosion, metal fatigueand other similar conditions. Following instruments are included to keepprocess variables under safe limit as well as provide alarms interlocks toautomatically take necessary action:a. Pressure switch and temperature switch : Shuts o_ theboiler if drum pressure/temperature exceeds 4 bar/144 deg C .b.
Low level switches: For the boiler drum this switch,shuts off the heater if there is no water in the drum. For other tanks theseswitches are used to avoid dry running of pumps if there is nothing to pump inthe tanks.c. High level switches provided to the cold water and hotwater tanks to avoid overflow of liquid. Variable tag and input output range ofdevices with unit Tag Service Range Unit PT-1 Steam 0-5 Bar LT-1 water 0-260 mmWc TT-1 steam 0-200 Deg LG-1 water 0-260 mm Wc PG-1 steam 0-7 Bar FT3 steam 0-7 Bar FCV-1 Steam 0-12 Mm TSH-401 Steam 0-150 deg Celsius PSH-401 Steam 0-7 Bar RV Steam 0-7 Bar P-101 Water -0-50 LPH(0-910 RPM) P-301 Water 0-1200 LPH Tk1 Tk2 Water 100 Liters Flowchart: Communicationin different modes of controlling Fig.4 Topology of communication Above figure shows how networking is done so thatuser can have multiple options to control. Local PLC provide two serial ports(one with RS232 and other RS232/485) and Ethernet port utilizing MODBUS andEthernet IP protocols. As shown in Fig.
4 we communicate PC where MATLAB and serverfor VPLC and VDCS resides with MODBUS RTU with RS232 serial protocol.DCS iscommunicated through MODBUS RTU with RS485 as make of local PLC and DCS aredifferent and we aim to have daisy chaining for other pilot plants. Ascontrologix PLC is connected with Ethernet IP protocol and communicated throughmessaging.Conclusion To provide a solution, ideas are tested and verified on pilot plants asthey represent a down scaled version of industrial process plants. According tothis practice, pilot plants are experimented for various control strategies anda solution is given to professional world in order to implement that specificstrategy to industry grade process plants.
One step ahead of this, we makepilot plants available to control from variety of controllers like ProgrammableLogic Controllers, Distributed Control Systems and simulation tools and testcontrol strategies. We can have comparative studies not only in class ofcontrol strategies but also in class of different controllers. AcknowledgmentI am very thankful of Prof. S. D.
Agashe for hisideas and guidance. Without his motivation and guidance this work would havebeen impossible. He always answered my questions and helped me out when I wasstuck with a problem.References