Actions based on probe signals include.
Shell boiler level control system.
Opening or closing a relay.
Level in boiler is high but control is stable.
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.
Levels at the control point hardly change with load or feedwater flow rate.
Identify the fuel to be used and if necessary where and how the fuel reserve is to be safely stored.
Select the control systems that will support the boiler in supplying dry steam to the plant at the required pressure s and flowrate s.
Advantages of shell.
A float is mounted in the boiler.
The system used in steam boilers is very similar.
The float will move up and down as the water level changes in the boiler.
This may be in an external chamber or directly within the boiler shell.
Level control systems with sensors or probes that fit inside of a boiler shell or steam drum provide a higher degree of safety than level control systems installed externally.
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.
Control in external chamber with low connection or in long length protection tube.
Size of the boiler shell.
The three elements are made up of the following.
Low alarm may sound.
A feedpump an on off level control.
Select the control systems that allow the boiler to operate safely and efficiently.
The next stage is to monitor this movement and to use it to control either.
Boiler at high steady load.
The three element drum level control is ideally suited where a boiler plant consists of multiple boilers and multiple feedwater pumps or where the feedwater has variations in pressure or flow.