![]() ![]() As such, PLCs run nonstop to translate continual strings of command for corresponding machinery. Today, the code is programmed for a variety of complex tasks. Since their development in the late 1960s, PLCs have grown more complex. The user pushes a button, the PLC translates this information into a command the machine can understand and the command takes effect. The PLC code lives in a central processing unit that acts as the go-between. Therefore, a code must cause the machine to act. However, the machine itself has no way of understanding this without a programmable code. On machines, a user will push a button to activate a particular command. None of this would be possible without a programmable logic controller (PLC), which translates commands for machines to understand. In thermal power plants the stack effect aids the Induced draft fans in removing the hot flue gases from the furnace and dispersing them at the top of the stack.Quick Links: Input/Output Modules and Field Devices | Ground Integrity | Power Supply Failure | Electrical Noise Interference | Loss of Network Communication | Heat | Conflict With the Outer Environment | Corrupted Memory | Managing the Risks Reasons Why PLC Control Systems FailĪt industrial facilities, vast numbers of electronically operated machines are programmed to move in various directions. In numerical terms this can be represented asĬhimney effect = 353 x Chimney Height x įor a thermal power plant with a stack height of 250 meters the effect could be around 77 mm of water column. Depending on the height it can be gentle draught or heavy suction. ![]() You can feel the effect if you stand near the doors or openings at the bottom of a stack or at open door of an elevator shaft. This pressure difference that pushes the hot gas up the flue gas stack or the chimney is the ‘chimney or stack effect’. This causes the natural flow of gases up the flue gas stack. The high density and heavier cold air will be always pushing the low density and lighter hot gases up. Consider this as two air columns connect at the bottom. The outside ambient air temperature is around say 30° C. The gas temperature inside the flue gas stack is around 140° C. This effect is found not only in chimneys but also in tall buildings. This is called the ‘chimney or the stack effect’. This is the natural flow of air up the chimney. There is a natural phenomena associated with the chimney or the flue gas stack. ![]() Many factors like terrain, dispersion pattern, plume heights, adjacent tall structures, and population density determine the height of the stack. The tallest stack currently is 420 meters in Kazakhstan. It serves the dual function of removing the hot gases out of the house at the same time bringing in fresh air to the fireplace for combustion.įlue gas stacks higher than 250 meters are common nowadays for larger power plants. Chimneys and fireplaces are a common household item in countries with a cold climate. At these heights the pollutants disperse in a very large area so that ground level concentrations are within permissible levels not harmful for humans or vegetation.Ĭhimneys were in use from the times of the Roman Empire. The function of the stack is to disperse at a great height the hot gases, emissions and particulates that leave the boiler. You can see the tall flue gas stacks in all the power plants.
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