Tuesday, November 3, 2015

Parameter Control in Boiler Automation System Using PLC and SCADA for Thermal Power Plant




Boiler is one of process equipment that serves to produce steam / vapor and requires continuous monitoring and inspection at frequent intervals. Steam produced will be used for various purposes, such as driving turbine and as a heating medium in the process unit. Automatic control system is needed to avoid the presence of possible errors in measurement and the various stages involved with human workers. There control system used is the Programmable Logic Controller and Supervisory Control and Data Acquisition System.

boiler automation clip art

Why Boiler need automation control system?

Boiler has a very important part and always generates high temperature water from the steam. The temperature of the steam boiler production process is very complex and difficult to control manually. Many accidents happens that cause injury as a result of human error in the operation of boilers and steam turbines. Usually, error occurs when the separation process is too low level may overheat and damage the boiler tube while the levels are too high they may interfere with separate water from steam and moisture transfer to the turbine, which Reduces boiler efficiency. Are data execution process can cause injury to operators who carry out such control that it took the automatic control system based SCADA.


Control Parameter and Boiler Operation

In a thermal power plant, the main raw material is water that must be controlled through automatic control system. How it works SCADA PLC-based control system of the boiler is the method that is currently ON OFF pushbutton initially switched ON the PLC, SCADA, different sensor switched ON. The system will be continued so that the feed water pump is switched ON using the feed water pump switch. Fuel coal from the coal space forwarded to a water tube boiler. As a result, the water from the water tank will be channeled through two parallel pipelines with a boiler with temperature controlled. Iterative process appropriate parameters have been determined.


The 3 Important things about Boiler Control Parameter

1. Boiler Temperature Control

Consists of:
  • Steams drum temperature, Underbed boiler temperature,
  • Force  draft  temperature,  Flue  gas  temperature,  Induced draft temperature, feed water temperature
In order to control temperature variations, it is used Resistance Temperature Detector (RTD PT100) which is a passive circuit element resistance and serves to raise the temperature in accordance with the predictions of a data input system. Raising the temperature is done by measuring the resistance and converts it into a voltage as differential amplifier input data on leads from RTD and provide the greatest voltage sensitivity. RTD signal measurements performed by connecting the RTD element in one leg of the Wheatstone or by RT pressure switch is used to sense the pressure in the boiler.
Boiler Temperature Control


2. Boiler Pressure Control

Consists of : Force draft pressure, Induced draft pressure, Steam drum  pressure,  Turbine  inlet  steam  pressure,  and  flue  gas pressure.

Pressure control system is done with the support RT pressure switch. This tool works on the basis of data input RT Series pressure switch which utilizes a seamless bellows sensing element. Bellows and can be either phosphor bronze or stainless steel to suit a wide range of media processes. Results of pressure control can be through a mechanism enclosed in a weather proof (IP66) enclosure that can be both DMC (Die Cast Aluminum). Pressure ranges between 1 to 30 bar
Boiler Pressure Control


3. Boiler Level Control

Consists of : Steam Drum level, Water level

Level control system is done with the support of a float switch to detect the level of liquid in the tank. This switch serves as the pump connectors, indicators, alarms, or other devices. Shape switches range from small to large and float in the liquid. It is made of mercury float switch in the hinged or as complicated series optical sensor or discrete output conductance produced as the liquid reaches various levels in the tank.
Boiler Level Control


Conclusion

Automatic control system in boiler operation is necessary for the safety of workers. The workings of PLC and SCADA is using sensors and connected through a communication cable for proper temperature control, so it can continue to maintain a certain the temperature in the boiler. Parameter to be controlled is the temperature, pressure and water level by using different sensors and the corresponding output is given to the PLC. If temperature and pressure in the boiler exceeds a predetermined value then the whole system shuts down automatically.


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