Boiler Low Water Fuel Cut-Off (LWCO) Quiz

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What happens to the electrical switch attached to the float chamber when the boiler water drops below the minimum safe level?

It closes, causing the safety shut-off valve to open

It opens, causing the safety shut-off valve to close (correct)

It stays in the same position

It causes the fuel supply to increase

What does the float inside the chamber do when the water in the boiler is above the lowest permissible level?

Causes the electrical switch to open

Keeps the electrical switch in the closed position (correct)

Increases the water level in the boiler

Has no impact on the electrical switch

What does the mercury switch do when there is a drop in water level?

Has no impact on any circuit

Opens the electrical circuit to the SSOV and closes alarm circuit contacts (correct)

Increases fuel supply to the burner

Closes the electrical circuit to the SSOV and opens 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 Signup and view all the answers

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 Signup and view all the answers

What is indicated if the alarm circuit energizes due to low water in a boiler?

The burner has shut down due to low water Signup and view all the answers

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 Signup and view all the answers

In which type of boilers are low water fuel cut-offs not required?

Electrode-type electric boilers Signup and view all the answers

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 Signup and view all the answers

What does the low water fuel cut-off (LWCO) device consist of?

A float chamber connected to the water gauge glass Signup and view all the answers

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 Signup and view all the answers

Why is the low water fuel cut-off (LWCO) considered an important boiler safety control?

It prevents overheating and weakening of pressure-retaining parts Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers

What is the advantage of the electric probe type low water fuel cut-off?

It contains no moving parts, reducing mechanical failure possibilities Signup and view all the answers

What are hot water boilers usually equipped with, connected to the water supply?

Automatic fill valve Signup and view all the answers

What can develop in hot water heating boilers as well as in steam boilers?

Low water conditions Signup and view all the answers

What may be caused by a faulty feedwater level controller or feedwater pump failure?

Rapidly falling water level in the boiler Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers