Identify the fuel to be used and if necessary where and how the fuel reserve is to be safely stored.
Shell boiler level control system.
Select the control systems that will support the boiler in supplying dry steam to the plant at the required pressure s and flowrate s.
In horizontal shell boilers the water level rises with increasing load due to the presence of more steam being below the water level in the boiler.
Opening or closing a relay.
Three element drum level control.
The three elements are made up of the following.
The float will move up and down as the water level changes in the boiler.
Control in external chamber with low connection or in long length protection tube.
Actions based on probe signals include.
This may be in an external chamber or directly within the boiler shell.
Size of the boiler shell.
Level in boiler is high but control is stable.
Waves caused by sudden load swings.
Advantages of shell.
A float is mounted in the boiler.
The next stage is to monitor this movement and to use it to control either.
The system used in steam boilers is very similar.
Low alarm may sound.
Boiler at high steady load.
A feedpump an on off level control.
Select the control systems that allow the boiler to operate safely and efficiently.
As it does so the water surface area steam release area will decrease because as the water level is above the centre line of the boiler the sides of the containing shell converge.
Levels at the control point hardly change with load or feedwater flow rate.