Boiler Control Systems Quiz & Flashcards

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Questions and Answers

What is the first step in the typical sequence of operation for most programming controllers described in the text?

Start purge

High airflow

Pre-ignition interlocks (correct)

Start draft fan

What component does the BMS start if all permissives and pre-ignition interlocks are satisfied?

Pilot SSOV

Combustion air damper

Draft fan or fans (correct)

Igniter

When does the BMS start the igniter and open the pilot SSOV?

Once the pilot is stabilized (correct)

Before the airflow reaches high fire

When the fan speed is increased

After the purge is complete

What is the purpose of the pilot trial for ignition period described in the text?

To stabilize the pilot flame Signup and view all the answers

During which step does the BMS detect high airflow?

Ignite pilot Signup and view all the answers

What initiates the purge counter in the BMS?

High airflow is confirmed Signup and view all the answers

What initiates the shutdown sequence in the burner system described in the text?

When the steam pressure or hot water temperature rises above the set point of the operating control Signup and view all the answers

What action causes the flame to be extinguished in the burner system?

De-energizing the SSOVs Signup and view all the answers

What is the purpose of the post-purge in the burner system?

Allowing time for SSOV proof-of-closure switches to close Signup and view all the answers

In the burner system, what does the programming controller do during standby mode?

Allows time for SSOV proof-of-closure switches to close Signup and view all the answers

What conditions need to be satisfied for the programming controller to repeat the startup sequence in the burner system?

Call for heat and all permissives and pre-ignition interlocks are satisfied Signup and view all the answers

What is the purpose of the BMS shutting the pilot SSOV and locking out the burner system?

To prevent the main burner from igniting Signup and view all the answers

During which stage does the BMS go into a 'safety shutdown and lockout' if the main flame is not established within 10 seconds?

Safe Start Signup and view all the answers

What happens if the pilot flame is not proven within 10 seconds during the Pilot Trial for Ignition period?

The BMS goes into safety shutdown and lockout Signup and view all the answers

When does the main SSOV close during the Main Flame Trial for Ignition period?

After 10 seconds of stable main flame Signup and view all the answers

What does the BMS do if a burner safety limit opens during operation?

Performs a safety shutdown and lockout Signup and view all the answers

During which stage does the programming controller begin a safe start check?

Standby Signup and view all the answers

What triggers the purge timer to begin counting in the ignition trials?

High airflow establishment Signup and view all the answers

When does the controller return to standby mode during startup?

After detecting a flame before ignition period begins Signup and view all the answers

What determines if the primary controller enters the Standby stage?

Call for heat is established Signup and view all the answers

What occurs if there are poor voltage conditions lasting greater than 4 minutes during initiation?

The controller locks out. Signup and view all the answers

What happens when a safety shutdown and lockout occurs during the SAFE START CHECK period?

The ignition transformer, the pilot SSOV, or the main SSOVs are energized. Signup and view all the answers

What does the programming controller do during a 15-second post-purge after a limit switch opens?

Enters standby mode. Signup and view all the answers

In which period would a safety shutdown and lockout NOT occur if the main SSOV is energized and there is no flame present?

RUN period Signup and view all the answers

What is indicated directly on the programming controller during a safety shutdown and lockout?

An ALARM light Signup and view all the answers

Which condition does NOT cause a safety shutdown and lockout during the PILOT TRIAL-FOR-IGNITION PERIOD?

Main SSOV is energized. Signup and view all the answers

What type of boiler does NOT require controllers with the ability to start draft fans and prove purge conditions?

Fuel-fired boilers with atmospheric burners Signup and view all the answers

What does the burner management system do if it detects an internal fault at any stage of operation?

Performs a safety shutdown and lockout. Signup and view all the answers

What happens when an operating control like pressuretrol opens in an automatically fired boiler?

The boiler shuts off but does not go into lockout. Signup and view all the answers

'Call for heat' in natural draft gas-fired boilers refers to what action?

'Call for startup.' Signup and view all the answers

'Uptake damper' is primarily opened by which component in natural draft gas-fired boilers?

'Primary controller.' Signup and view all the answers

What is necessary for the boiler if it is gas-fired according to the given text?

Ensure the fuel pressure is above the cutout point of the high gas pressure cut-off switch Signup and view all the answers

What initiates the boiler ignition sequence according to the text?

Closing the on-off and operating control switches Signup and view all the answers

What does the programming controller do after confirming the low-fire position?

Energizes the ignition transformer Signup and view all the answers

What is a crucial step for oil-fired boilers before starting up according to the text?

Properly priming the fuel lines and oil pump Signup and view all the answers

When does the programming controller energize the main SSOV according to the text?

After 10 seconds of lighting the pilot flame Signup and view all the answers

What must be ensured if a boiler uses oil that requires preheating according to the text?

The oil is hot enough to satisfy the low oil temperature cut-off switch Signup and view all the answers

Which action does NOT need to be performed for dual fuel boilers according to the text?

Ensuring low combustion air pressure fuel cut-off switch is open Signup and view all the answers

What is the primary function of the pilot SSOV in a boiler system?

To keep the main burner in operation until desired parameters are reached Signup and view all the answers

If the pilot does not light within 15 to 90 seconds, what action will the primary controller take based on the text?

Retrigger ignition Signup and view all the answers

What happens if the main flame goes out during the run period?

The burner immediately goes into safety shutdown and lockout Signup and view all the answers

In oil-fired boilers with no pilot, what signals a call for heat?

The boiler pressuretrol or aquastat Signup and view all the answers

What is the consequence of an ignition failure during boiler startup?

The programming control locks out Signup and view all the answers

What conditions must be satisfied before a steam or hot water boiler can be started by its programming controller?

All permissives and pre-ignition interlocks must be met Signup and view all the answers

What operation does a typical programming control perform in a fully automatic boiler system?

Energizes the motor that drives the draft fan and fuel oil pump Signup and view all the answers

How many main flame failures in a call for heat cycle may prompt a 5-minute natural draft purge based on the text?

5 Signup and view all the answers

Study Notes

Typical Sequence of Operation

The first step involves checking all permissives and pre-ignition interlocks for safety before proceeding.
If all checks are satisfactory, the burner management system (BMS) initiates the start of the main burner system.

Ignition and Flame Establishment

The BMS starts the igniter and opens the pilot shut-off valve (SSOV) when all conditions for ignition are met.
The pilot trial for ignition period is necessary to verify that a stable pilot flame is established before proceeding to the main flame.
High airflow detection by the BMS occurs during the pre-ignition phase.
The purge counter is initiated when there’s a need to clear the combustion chamber of unburned gas.

Shutdown Procedures

The burner system shutdown sequence is triggered by failure to establish a flame or by exceeding safety limits.
An action such as a failed flame detection or safety limit violation extinguishes the flame in the burner system.
The post-purge ensures that residual gases are cleared from the system after shutdown for safety.

Operating Modes

In standby mode, the programming controller continuously monitors system conditions and remains ready for ignition.
The startup sequence can be repeated only if all safety conditions and pre-ignition checks are satisfied.

BMS Operations

When the BMS shuts the pilot SSOV, it locks out the burner system to prevent unsafe operation.
If the main flame is not established within 10 seconds, the BMS goes into safety shutdown and lockout.
During the pilot trial for ignition period, if the pilot flame is not proven within 10 seconds, the BMS will execute a shutdown.

Timing and Conditions

The main SSOV closes during the main flame trial for ignition period if the flame is not detected.
If a burner safety limit opens during operation, the BMS will initiate a safety shutdown.
The programming controller begins the safe start check during the startup sequence to ensure all systems are operational.

Lights and Indicators

The controller returns to standby mode once ignition trials are satisfactorily completed, or safety conditions fail.
Poor voltage conditions lasting over 4 minutes will prevent energizing the burner and could lead to a system lockout.
During a safety shutdown and lockout, the programming controller displays an indicator to alert operators.

Boiler Operation Conditions

A safety shutdown and lockout does not occur during the pilot trial for ignition if the main SSOV is energized with no flame present.
Fire-tube boilers typically do not require controllers that start draft fans or prove purge conditions.
The BMS detects internal faults at any operational stage and will perform necessary safety actions.

Common Actions and Conditions

'Call for heat' in natural draft gas-fired boilers triggers the ignition sequence.
The uptake damper is primarily opened by the combustion air blower.
Gas-fired boilers require adequate fuel and air supply for combustion initiation.
The boiler ignition sequence begins with the command from the programming controller.

Specific Boiler Considerations

After confirming the low-fire position, the programming controller prepares for fuel delivery.
Oil-fired boilers necessitate pre-start checks for fuel viscosity and heater functionality.
The main SSOV is energized once the air-fuel mixture is confirmed safe and ready for ignition.

Fuel Considerations

If the boiler uses oil requiring preheating, the preheat condition must be ensured before ignition.
Dual fuel boilers do not require specific actions to ensure functionality besides basic startup checks.
The primary function of the pilot SSOV is to control the flow of fuel to the pilot burner.

Safety Measures

If the pilot fails to ignite within 15 to 90 seconds, the primary controller will execute a safety shutdown.
Main flame loss during the run period triggers an immediate system shutdown for safety.
In oil-fired boilers without a pilot, the call for heat is managed directly by the control system.
An ignition failure during startup results in a halt of operations, followed by troubleshooting protocols.

Starting Conditions

Before initiating a steam or hot water boiler, all safety limits and operational conditions must be verified.
A typical programming control in fully automatic boiler systems coordinates start-up, operation, and safety functions.
More than two main flame failures in a single call for heat cycle may require a 5-minute natural draft purge to ensure safety before restart.

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Description

This quiz provides an overview of boiler control systems, focusing on the role of the pilot SSOV, primary control, operating control, and programming control in maintaining the desired steam pressure or water temperature. It also covers the restart process in case of pressure or temperature drops.

Boiler Control Systems Overview