20 Questions
What happens to the electrical switch attached to the float chamber when the boiler water drops below the minimum safe level?
It opens, causing the safety shut-off valve to close
What does the float inside the chamber do when the water in the boiler is above the lowest permissible level?
Keeps the electrical switch in the closed position
What does the mercury switch do when there is a drop in water level?
Opens the electrical circuit to the SSOV and closes alarm circuit contacts
What happens if the feedwater pump fails to start when the water is still above the lowest permissible level?
The bulb with the three-wire switch acts as a boiler emergency shutdown
What does the float controlled make-up water valve do if the boiler drum level drops?
Moves to a lower position, which opens the make-up valve further to admit more water into the boiler
What is indicated if the alarm circuit energizes due to low water in a boiler?
The burner has shut down due to low water
What is the function of the low water fuel cut-off (LWCO) in a boiler system?
To shut off the boiler burner system if water level drops to a dangerous level
In which type of boilers are low water fuel cut-offs not required?
Electrode-type electric boilers
What is the purpose of the lowest permissible water level (LPWL) in a boiler?
To indicate the lowest safe operating water level for the boiler
What does the low water fuel cut-off (LWCO) device consist of?
A float chamber connected to the water gauge glass
What does the LWCO do in relation to the lowest permissible water level (LPWL) in a boiler?
It turns off the burner system after reaching LPWL
Why is the low water fuel cut-off (LWCO) considered an important boiler safety control?
It prevents overheating and weakening of pressure-retaining parts
What happens when the plunger drops entirely outside of the magnetic field at the cut-off point?
The contacts close, opening the burner circuit and shutting off the fuel supply
What causes a small current to flow through the water between the probes in the electric probe type low water fuel cut-off?
Water covering both probes
What is the advantage of the electric probe type low water fuel cut-off?
It contains no moving parts, reducing mechanical failure possibilities
What are hot water boilers usually equipped with, connected to the water supply?
Automatic fill valve
What can develop in hot water heating boilers as well as in steam boilers?
Low water conditions
What may be caused by a faulty feedwater level controller or feedwater pump failure?
Rapidly falling water level in the boiler
What happens if the cut-off fails to shut the boiler down when the water level drops to the low water cut-off point?
The water level may drop to a dangerous level
What action is essential for the plant operator to take regarding the low water cut-off?
Conduct regular tests of the low water cut-off
Test your knowledge about the low water fuel cut-off (LWCO) in boilers. Learn about its function and importance in boiler safety.
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