69 Questions
EASY What is the primary difference between fully automatic and semi-automatic ignition systems in boilers?
Level of operator interaction
What is the purpose of the proof of closure switch in the main gas line?
To ensure the valve is fully closed
What is the sequence of events in a boiler ignition system?
Pre-purge, pilot ignition, main burner ignition, run period, post purge
What is the function of the fuel line bleed valves in semi-automatic ignition systems?
To operate automatically for safety
Why do semi-automatic ignition systems require interaction with trained operators?
Because they have manual control elements
What is the purpose of the SSOVs in the fuel train?
To ensure safety by shutting off the gas supply
What is the significance of the 10-second time period in semi-automatic ignition systems?
It is the time within which the operator must complete a step
What is the primary purpose of the supervised main test firing valves in semi-automatic ignition systems?
To ensure safety by requiring manual operation
What is the immediate action required when the valve energizes?
Rotate the operating lever to the CLOSED position and then back to the OPEN position
What happens to the vent valve 'M' when the SSOVs energize?
It closes automatically
How should the supervised main test firing valve be opened?
Gradually to allow the burner to light gently
What ignites the gas in the main burner?
The pilot flame
In modern burners without semi-automatic magnetic latching SSOVs, what is the operator's role in the ignition sequence?
To open the main burner test firing valve only
What is the purpose of the safety vent valve or “bleed” solenoid in Figure 5?
To prevent gas from entering the furnace when the boiler burner is off
What happens to valves L and N when the burner is off?
They are both closed
What is the purpose of the main test firing valve (Q)?
To ensure the boiler is fully closed before recycling or pre-purging
What is the purpose of the local burner control panel?
To start and stop the forced draft fan, start the purge sequence, and start the burner and ignitor
What must be satisfied before the ignition sequence can begin?
All the boiler permissives must be satisfied
What is the purpose of the boiler master controller in larger boilers?
To send control signals to the airflow controller and fuel flow controller
What is the first step in starting the burner?
Start the forced draft fan
What happens during the purge period?
The forced draft fan ramps up to high speed
What happens after the purge is complete?
The BURNER READY light comes on
What must be done if SSOV “N” is of the magnetic latching valve style?
It must be reset after ignition
MEDIUM What is the consequence of not rotating the operating lever to the CLOSED position and then back to the OPEN position immediately after the valve energizes?
The ignition sequence will not complete.
What is the purpose of opening the supervised main test firing valve gradually?
To allow the gas to flow to the main burner and ignite gently.
What happens to SSOV 'L' and SSOV 'N' in modern burners without semi-automatic magnetic latching SSOVs?
They open automatically during the main flame trial for ignition period.
What is the result of completing the ignition sequence in time?
The boiler can be warmed up.
What is the source of ignition for the gas in the main burner?
The pilot flame.
What is the purpose of the additional safety features in semi-automatic ignition systems?
To ensure the correct sequence of events is followed during startup
What is the function of the SSOVs in the pilot gas line?
To provide a safety shut-off in case of an emergency
What happens if the valve fails to close completely due to mechanical failure or debris on the valve seats?
The proof of closure switch will not close, preventing the ignition sequence from beginning
What is the purpose of the main burner SSOVs in the fuel train?
To provide a safety shut-off in case of an emergency
What is the significance of the time period in which the main test firing valve must be opened?
It forces the operator to complete the ignition sequence within a set time period
What is the primary purpose of the supervised main test firing valve?
To require manual operation by a trained operator
What is the purpose of the fuel train in a natural gas burner?
To control the flow of fuel to the main burner
What is the significance of the proof of closure switches in the main gas line?
They prevent the ignition sequence from beginning if the valve fails to close completely
What is the primary function of the safety vent valve or 'bleed' solenoid?
To prevent gas from entering the furnace when the boiler burner is off
What happens to valves L and N when the burner trips?
Both L and N close
What is the purpose of the local burner control panel?
To start and stop the forced draft fan, purge sequence, and burner
What must be satisfied before the ignition sequence can begin?
The water level, boiler pressure, fuel pressure, and SSOV and main test firing valve proof of closure switches
What happens during the purge period?
At least five furnace volumes of air are exchanged
What is the function of the proof of closure switch in the main test firing valve?
To prevent the boiler from recycling or pre-purging unless the main test firing valve is fully closed
What is the purpose of the boiler master controller in larger boilers?
To send control signals to the airflow controller and fuel flow controller
What happens when the PURGE COMPLETE light comes on?
The fan returns to its low-fire start speed, and the BURNER READY light comes on
What must be done if SSOV 'N' is of the magnetic latching valve style?
It must be manually latched open during light-off
What is the first step in starting the burner?
Start the forced draft fan, using the control panel FD Fan START button
HARD What would be the consequence of not venting valve 'M' immediately after the SSOVs energize?
The main burner would not ignite.
What would occur if the supervised main test firing valve is opened rapidly?
The gas flow would be unstable.
What is the primary purpose of the supervised main test firing valve in modern burners without semi-automatic magnetic latching SSOVs?
To manually open the main burner.
What would occur if the SSOVs fail to close completely due to mechanical failure or debris on the valve seats?
The main burner would ignite prematurely.
What is the significance of the operator's role in the ignition sequence in modern burners without semi-automatic magnetic latching SSOVs?
To manually open the main burner test firing valve.
What is the purpose of the pre-purge period in the boiler ignition sequence?
To ensure at least five furnace volumes of air have been exchanged
What happens to the forced draft fan during the purge period?
It ramps up to high speed or the dampers open wide
What is the purpose of the boiler master controller in larger boilers?
To send control signals to the airflow and fuel flow controllers
What happens to valve 'M' when the burner is operating?
It closes
What is the purpose of the proof of closure switch in the main test firing valve?
To ensure the valve is fully closed before ignition
What must be done if SSOV 'N' is of the magnetic latching valve style?
It must be manually latched open during light-off
What happens when the PURGE COMPLETE light comes on?
The fan returns to its low-fire start speed or damper position
What is the purpose of the local burner control panel?
To start and stop the forced draft fan, and start the purge sequence
What happens to valves L and N when the burner trips?
They close
What is the purpose of the safety vent valve or 'bleed' solenoid?
To ensure no gas can enter the furnace when the boiler burner is off
What is the primary purpose of the proof of closure switches in the main gas line?
To prevent the ignition sequence from beginning if the valve fails to close completely
What is the significance of the 10-second time period in semi-automatic ignition systems?
The maximum time allowed for the operator to complete the ignition sequence
What is the primary function of the safety vent valve or 'bleed' solenoid in Figure 5?
To vent the fuel line during the purge period
What is the consequence of not completing the ignition sequence within the set time period?
The main burner will not ignite
What is the primary purpose of the main test firing valve in semi-automatic ignition systems?
To allow the operator to supervise the main test firing
What is the significance of the proof of closure switch in the main gas line?
It prevents the ignition sequence from beginning if the valve fails to close completely
What is the primary function of the fuel train in a natural gas burner?
To control the flow of natural gas to the main burner
What is the consequence of the valve failing to close completely due to mechanical failure or debris on the valve seats?
The proof of closure switch will not close
Study Notes
Boiler Ignition Systems
- Most boilers in smaller power plants have fully automatic burner management systems that automatically recycle on call for heat.
- Larger plants, however, have semi-automatic ignition systems that require interaction with trained operators to progress through their ignition sequences.
Sequence of Ignition Steps
- Pre-purge
- Pilot ignition
- Main burner ignition
- Run period
- Post purge
Semi-Automatic Systems
- Control the order of events that an operator must perform to light-off the boiler.
- Force the operator to complete these steps within a set time period.
Safety Features
- Fuel line bleed valves operate automatically.
- Supervised main test firing valves require manual operation.
- Proof of closure switches are burner pre-ignition interlocks or permissives.
Fuel Train Components
- Pilot gas line equipped with two safety shut-off valves (SSOVs).
- Main gas line equipped with two automatically operated main burner SSOVs.
- Safety vent valve or "bleed" solenoid ensures no gas enters the furnace when the boiler burner is off.
Main Test Firing Valve
- Also known as a supervised cock.
- Has a built-in proof of closure pre-ignition interlock switch.
- Prevents a boiler from recycling or even pre-purging unless the main test firing valve is in the fully closed position.
Local Burner Control Panel
- Located beside the fuel train and mounted on the boiler.
- Has switches that start and stop the forced draft fan, start the purge sequence, and start the burner and ignitor.
- Has status lights that show when the purge is permissive, when the purge is complete, when the burner is ready for start, and when the burner has tripped.
Boiler Permissives
- Water level, boiler pressure, and fuel pressure must be within their acceptable limits.
- SSOV and main test firing valve proof of closure switches must be closed.
- Boiler "run" switch must be in the "on" position.
Ignition Sequence
- Start the forced draft fan.
- Press the PURGE START button.
- When the purge is done, the PURGE COMPLETE light will come on.
- Press the IGNITION START push button.
- If SSOV "N" is of the magnetic latching valve style, it must be reset.
- Finally, the operator must manually open the supervised main test firing valve.
Boiler Ignition Systems
- Most boilers in smaller power plants have fully automatic burner management systems that automatically recycle on call for heat.
- Larger plants, however, have semi-automatic ignition systems that require interaction with trained operators to progress through their ignition sequences.
Sequence of Ignition Steps
- Pre-purge
- Pilot ignition
- Main burner ignition
- Run period
- Post purge
Semi-Automatic Systems
- Control the order of events that an operator must perform to light-off the boiler.
- Force the operator to complete these steps within a set time period.
Safety Features
- Fuel line bleed valves operate automatically.
- Supervised main test firing valves require manual operation.
- Proof of closure switches are burner pre-ignition interlocks or permissives.
Fuel Train Components
- Pilot gas line equipped with two safety shut-off valves (SSOVs).
- Main gas line equipped with two automatically operated main burner SSOVs.
- Safety vent valve or "bleed" solenoid ensures no gas enters the furnace when the boiler burner is off.
Main Test Firing Valve
- Also known as a supervised cock.
- Has a built-in proof of closure pre-ignition interlock switch.
- Prevents a boiler from recycling or even pre-purging unless the main test firing valve is in the fully closed position.
Local Burner Control Panel
- Located beside the fuel train and mounted on the boiler.
- Has switches that start and stop the forced draft fan, start the purge sequence, and start the burner and ignitor.
- Has status lights that show when the purge is permissive, when the purge is complete, when the burner is ready for start, and when the burner has tripped.
Boiler Permissives
- Water level, boiler pressure, and fuel pressure must be within their acceptable limits.
- SSOV and main test firing valve proof of closure switches must be closed.
- Boiler "run" switch must be in the "on" position.
Ignition Sequence
- Start the forced draft fan.
- Press the PURGE START button.
- When the purge is done, the PURGE COMPLETE light will come on.
- Press the IGNITION START push button.
- If SSOV "N" is of the magnetic latching valve style, it must be reset.
- Finally, the operator must manually open the supervised main test firing valve.
Boiler Ignition Systems
- Most boilers in smaller power plants have fully automatic burner management systems that automatically recycle on call for heat.
- Larger plants, however, have semi-automatic ignition systems that require interaction with trained operators to progress through their ignition sequences.
Sequence of Ignition Steps
- Pre-purge
- Pilot ignition
- Main burner ignition
- Run period
- Post purge
Semi-Automatic Systems
- Control the order of events that an operator must perform to light-off the boiler.
- Force the operator to complete these steps within a set time period.
Safety Features
- Fuel line bleed valves operate automatically.
- Supervised main test firing valves require manual operation.
- Proof of closure switches are burner pre-ignition interlocks or permissives.
Fuel Train Components
- Pilot gas line equipped with two safety shut-off valves (SSOVs).
- Main gas line equipped with two automatically operated main burner SSOVs.
- Safety vent valve or "bleed" solenoid ensures no gas enters the furnace when the boiler burner is off.
Main Test Firing Valve
- Also known as a supervised cock.
- Has a built-in proof of closure pre-ignition interlock switch.
- Prevents a boiler from recycling or even pre-purging unless the main test firing valve is in the fully closed position.
Local Burner Control Panel
- Located beside the fuel train and mounted on the boiler.
- Has switches that start and stop the forced draft fan, start the purge sequence, and start the burner and ignitor.
- Has status lights that show when the purge is permissive, when the purge is complete, when the burner is ready for start, and when the burner has tripped.
Boiler Permissives
- Water level, boiler pressure, and fuel pressure must be within their acceptable limits.
- SSOV and main test firing valve proof of closure switches must be closed.
- Boiler "run" switch must be in the "on" position.
Ignition Sequence
- Start the forced draft fan.
- Press the PURGE START button.
- When the purge is done, the PURGE COMPLETE light will come on.
- Press the IGNITION START push button.
- If SSOV "N" is of the magnetic latching valve style, it must be reset.
- Finally, the operator must manually open the supervised main test firing valve.
This quiz covers the differences between fully automatic and semi-automatic burner management systems used in boilers of various sizes. It explains the startup sequence and safety features of each system.
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