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Questions and Answers
EASY What is the main limitation of using thermocouples for flame failure detection?
EASY What is the main limitation of using thermocouples for flame failure detection?
What is the maximum boiler input size for which thermocouples can be used for flame failure detection?
What is the maximum boiler input size for which thermocouples can be used for flame failure detection?
What is the purpose of the copper outer sheath in a thermocouple?
What is the purpose of the copper outer sheath in a thermocouple?
What is the typical voltage output of a thermocouple when exposed to a flame?
What is the typical voltage output of a thermocouple when exposed to a flame?
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What is the purpose of the pilotstat in a thermocouple circuit?
What is the purpose of the pilotstat in a thermocouple circuit?
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What is the minimum voltage required to keep the SSOV open?
What is the minimum voltage required to keep the SSOV open?
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What is the main component that makes up a thermocouple?
What is the main component that makes up a thermocouple?
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What is the function of the cold junction in a thermocouple circuit?
What is the function of the cold junction in a thermocouple circuit?
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In a basic flame rod system, what happens when the flame is present?
In a basic flame rod system, what happens when the flame is present?
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What can cause grounding between the flame rod and the burner?
What can cause grounding between the flame rod and the burner?
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What is the advantage of using flame rods in burners over 120 kW input?
What is the advantage of using flame rods in burners over 120 kW input?
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What type of photocell is shown in Figure 15?
What type of photocell is shown in Figure 15?
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What happens when a flame failure occurs in an infrared scanner system?
What happens when a flame failure occurs in an infrared scanner system?
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What is the purpose of the threaded ring in a photoelectric cell?
What is the purpose of the threaded ring in a photoelectric cell?
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What is the maximum temperature allowed for a lead sulfide scanner?
What is the maximum temperature allowed for a lead sulfide scanner?
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Why are flame rods not commonly used with oil-fired burners?
Why are flame rods not commonly used with oil-fired burners?
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What is the purpose of the scanner sight tube in a firetube boiler burner assembly?
What is the purpose of the scanner sight tube in a firetube boiler burner assembly?
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What type of rays does the ultraviolet (UV) scanner respond to?
What type of rays does the ultraviolet (UV) scanner respond to?
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What is the function of the burner management system (BMS) in automatically fired boilers?
What is the function of the burner management system (BMS) in automatically fired boilers?
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What is the purpose of the flame relay in a photoelectric safeguard system?
What is the purpose of the flame relay in a photoelectric safeguard system?
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Why is it important to ensure the UV scanner cannot see the igniter spark?
Why is it important to ensure the UV scanner cannot see the igniter spark?
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What is the function of the rectifying photocell in a burner management system?
What is the function of the rectifying photocell in a burner management system?
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Why did the programming controller open the main safety shut-off valves in the case study?
Why did the programming controller open the main safety shut-off valves in the case study?
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What is the advantage of mounting the rectifying photocell inside the combustion air supply tube?
What is the advantage of mounting the rectifying photocell inside the combustion air supply tube?
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What is the purpose of the pilot burner in a firetube boiler burner assembly?
What is the purpose of the pilot burner in a firetube boiler burner assembly?
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What is the typical operating temperature range for a UV scanner?
What is the typical operating temperature range for a UV scanner?
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What is a combination gas valve?
What is a combination gas valve?
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What is the purpose of an external pilotstat?
What is the purpose of an external pilotstat?
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What is required to relight the pilot?
What is required to relight the pilot?
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What is the function of a thermocouple?
What is the function of a thermocouple?
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What is a thermopile?
What is a thermopile?
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What is the advantage of a millivolt system?
What is the advantage of a millivolt system?
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What is the function of a flame rod?
What is the function of a flame rod?
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What is the principle of a flame rod?
What is the principle of a flame rod?
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Why does the AC get rectified to pulsating DC in a flame rod circuit?
Why does the AC get rectified to pulsating DC in a flame rod circuit?
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What is the purpose of a limit switch in the SSOV circuit?
What is the purpose of a limit switch in the SSOV circuit?
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MEDIUM What is the reason why the UV scanner should not be able to see the igniter spark?
MEDIUM What is the reason why the UV scanner should not be able to see the igniter spark?
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What is the purpose of the sight tube in a firetube boiler burner assembly?
What is the purpose of the sight tube in a firetube boiler burner assembly?
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What is the function of the rectifying photocell in a burner management system?
What is the function of the rectifying photocell in a burner management system?
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What is the advantage of mounting the rectifying photocell inside the combustion air supply tube?
What is the advantage of mounting the rectifying photocell inside the combustion air supply tube?
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What was the root cause of the problem in the case study?
What was the root cause of the problem in the case study?
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What is the principle of operation of the UV scanner?
What is the principle of operation of the UV scanner?
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What is the function of the pilot burner in a firetube boiler burner assembly?
What is the function of the pilot burner in a firetube boiler burner assembly?
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What happened when the programming controller opened the main safety shut-off valves in the case study?
What happened when the programming controller opened the main safety shut-off valves in the case study?
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What is the primary direction of electron flow in a flame rod system?
What is the primary direction of electron flow in a flame rod system?
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What is the primary reason why thermocouples are limited to small gas burners?
What is the primary reason why thermocouples are limited to small gas burners?
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What is the purpose of the insulated inner wire in a thermocouple?
What is the purpose of the insulated inner wire in a thermocouple?
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What is the purpose of the relay in a basic flame rod system?
What is the purpose of the relay in a basic flame rod system?
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What happens when the hot junction of a thermocouple is exposed to a flame?
What happens when the hot junction of a thermocouple is exposed to a flame?
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What can cause soot bridging between the flame rod and the burner?
What can cause soot bridging between the flame rod and the burner?
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What is the function of the relay in a thermocouple circuit?
What is the function of the relay in a thermocouple circuit?
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What type of photocell responds to infrared, ultraviolet, or visible light emitted by fire?
What type of photocell responds to infrared, ultraviolet, or visible light emitted by fire?
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What is the main component of a thermocouple that is exposed to the flame?
What is the main component of a thermocouple that is exposed to the flame?
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What is the effect of a flame failure on the resistance of the infrared scanner cell?
What is the effect of a flame failure on the resistance of the infrared scanner cell?
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What is the purpose of the sighting tube in a photoelectric cell installation?
What is the purpose of the sighting tube in a photoelectric cell installation?
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Why is it important to ensure the thermocouple voltage drops below a certain level before the safety shut-off valve closes?
Why is it important to ensure the thermocouple voltage drops below a certain level before the safety shut-off valve closes?
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What is the purpose of the pilot burner assembly in a firetube boiler?
What is the purpose of the pilot burner assembly in a firetube boiler?
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Why are flame rods not commonly used with oil-fired burners?
Why are flame rods not commonly used with oil-fired burners?
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What is the advantage of using thermocouples for flame failure detection in small gas burners?
What is the advantage of using thermocouples for flame failure detection in small gas burners?
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What is the function of the burner management system (BMS) in automatically fired boilers?
What is the function of the burner management system (BMS) in automatically fired boilers?
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What is the effect of grounding between the flame rod and the burner on the burner monitoring circuit?
What is the effect of grounding between the flame rod and the burner on the burner monitoring circuit?
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What is the advantage of using flame rods in burners over 120 kW input?
What is the advantage of using flame rods in burners over 120 kW input?
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What is the purpose of a combination gas valve?
What is the purpose of a combination gas valve?
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What happens when a pilot flame fails in a system with an external pilotstat that provides 100% shutoff?
What happens when a pilot flame fails in a system with an external pilotstat that provides 100% shutoff?
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What is the purpose of a thermopile?
What is the purpose of a thermopile?
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What is the purpose of a limit switch in the SSOV circuit?
What is the purpose of a limit switch in the SSOV circuit?
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What is the principle of a flame rod?
What is the principle of a flame rod?
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Why does the AC get rectified to pulsating DC in a flame rod circuit?
Why does the AC get rectified to pulsating DC in a flame rod circuit?
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What is the advantage of a millivolt system?
What is the advantage of a millivolt system?
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What is required to relight the pilot?
What is required to relight the pilot?
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What is the function of a thermocouple?
What is the function of a thermocouple?
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What is the purpose of an external pilotstat that provides 100% shutoff?
What is the purpose of an external pilotstat that provides 100% shutoff?
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What is the reason why thermocouples have a slow flame failure response time?
What is the reason why thermocouples have a slow flame failure response time?
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What is the purpose of the insulated inner wire in a thermocouple?
What is the purpose of the insulated inner wire in a thermocouple?
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What happens when the hot junction of a thermocouple is exposed to a flame?
What happens when the hot junction of a thermocouple is exposed to a flame?
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Why are thermocouples limited to small gas burners?
Why are thermocouples limited to small gas burners?
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What is the function of the pilotstat in a thermocouple circuit?
What is the function of the pilotstat in a thermocouple circuit?
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What is the purpose of the external low voltage power supply in a thermocouple circuit?
What is the purpose of the external low voltage power supply in a thermocouple circuit?
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What happens when the thermocouple voltage drops below about 7 millivolts?
What happens when the thermocouple voltage drops below about 7 millivolts?
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What is the purpose of the copper outer sheath in a thermocouple?
What is the purpose of the copper outer sheath in a thermocouple?
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What is the primary reason why the UV scanner in the case study detected a flame signal of 3.5 volts?
What is the primary reason why the UV scanner in the case study detected a flame signal of 3.5 volts?
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What is the purpose of the curved metal cathode in a rectifying photocell?
What is the purpose of the curved metal cathode in a rectifying photocell?
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Why is it important to mount the UV scanner close to the flame, but not beyond 100°C?
Why is it important to mount the UV scanner close to the flame, but not beyond 100°C?
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What is the primary function of the burner management system in automatically fired boilers?
What is the primary function of the burner management system in automatically fired boilers?
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What is the advantage of mounting the rectifying photocell inside the combustion air supply tube?
What is the advantage of mounting the rectifying photocell inside the combustion air supply tube?
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What is the primary reason why the programming controller opened the main safety shut-off valves in the case study?
What is the primary reason why the programming controller opened the main safety shut-off valves in the case study?
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What is the primary function of the flame relay in a photoelectric safeguard system?
What is the primary function of the flame relay in a photoelectric safeguard system?
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HARD What is the primary reason why the UV scanner should not be able to see the igniter spark?
HARD What is the primary reason why the UV scanner should not be able to see the igniter spark?
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What is the primary function of the flame relay in a flame rod system?
What is the primary function of the flame relay in a flame rod system?
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What is the reason why flame rods are not commonly used with oil-fired burners?
What is the reason why flame rods are not commonly used with oil-fired burners?
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What is the primary difference between a flame rod system and a photoelectric cell system?
What is the primary difference between a flame rod system and a photoelectric cell system?
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What is the purpose of the sighting tube in a photoelectric cell system?
What is the purpose of the sighting tube in a photoelectric cell system?
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What happens to the electrical resistance of the lead-sulfide cell in an infrared scanner when it is exposed to infrared radiation?
What happens to the electrical resistance of the lead-sulfide cell in an infrared scanner when it is exposed to infrared radiation?
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What is the primary function of the burner management system (BMS) in automatically fired boilers?
What is the primary function of the burner management system (BMS) in automatically fired boilers?
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What is the primary reason why the flame rod system is more suitable for high-input boilers?
What is the primary reason why the flame rod system is more suitable for high-input boilers?
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What is the primary function of the threaded ring in a photoelectric cell system?
What is the primary function of the threaded ring in a photoelectric cell system?
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What happens when the flame relay opens in a flame rod system?
What happens when the flame relay opens in a flame rod system?
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What is the primary difference between a lead-sulfide cell and a rectifying photocell?
What is the primary difference between a lead-sulfide cell and a rectifying photocell?
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What is the primary function of a combination gas valve?
What is the primary function of a combination gas valve?
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What is the purpose of a thermopile?
What is the purpose of a thermopile?
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What is the primary advantage of a millivolt system?
What is the primary advantage of a millivolt system?
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What is the purpose of a flame rod?
What is the purpose of a flame rod?
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What is the principle of operation of a flame rod?
What is the principle of operation of a flame rod?
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What is the purpose of a limit switch in the SSOV circuit?
What is the purpose of a limit switch in the SSOV circuit?
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What is the reason why the AC gets rectified to pulsating DC in a flame rod circuit?
What is the reason why the AC gets rectified to pulsating DC in a flame rod circuit?
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What is the purpose of an external pilotstat?
What is the purpose of an external pilotstat?
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What is the function of a thermocouple?
What is the function of a thermocouple?
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What is the purpose of relighting the pilot?
What is the purpose of relighting the pilot?
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Study Notes
Flame Failure Detection Methods
- Various methods are used to detect flame failure in boilers, including:
- Thermocouples
- Thermopiles
- Flame rods
- Photoelectric cells
Thermocouples
- A thermocouple consists of two dissimilar wires welded together at one end to form a measuring (or “hot”) junction.
- The opposite ends are connected to an electric circuit, called the reference (or “cold”) junction.
- When the hot junction is exposed to a flame, its temperature increases above that of the cold junction, generating a small voltage (about 20 to 30 millivolts).
- This voltage energizes a sensitive relay, called a pilotstat, which may be built into an SSOV (Safety Shut-Off Valve).
- Thermocouples are limited to pilot burners up to 120 kW input due to their slow flame failure response time (up to 90 seconds).
Thermopiles
- A thermopile is a flame detector that develops sufficient voltage to operate an SSOV independently from any external power source.
- It consists of multiple thermocouples in series, generating around 750 millivolts.
- Thermopiles are also limited to burners not exceeding 120 kW input.
- They offer the advantage of operating without external power, making them suitable for small residential boilers.
Flame Rods
- A flame rod is a flame detection device that operates on the principle that flames can conduct electricity.
- It consists of two electrodes (the flame rod and the burner) and the flame, which conducts electricity between them.
- The flame rod is a heat-resistant, small diameter metal rod, supported by a ceramic holder that keeps the rod electrically insulated from the burner.
- Flame rods are commonly used with gas burners and are suitable for burners over 120 kW input due to their fast flame failure response time.
Photoelectric Cells
- A photoelectric cell is a device that reacts to infrared, ultraviolet, or visible light emitted by fire.
- Common types of photocells include:
- Infrared scanner
- Ultraviolet scanner
- Rectifying photocell
- A scanner is mounted on the boiler in such a way that it can observe the flame, and its resistance decreases with an increase in the amount of infrared light it receives from the flame.
- When a flame failure occurs, the scanner does not sense a flame, and its resistance increases, causing the flame relay to open, which shuts off the fuel to the burner.
Case Study
- A case study highlights the importance of proper installation and maintenance of flame safeguard controls to avoid false readings and potential explosions.
Flame Failure Detection Methods
- Various methods are used to detect flame failure in boilers, including:
- Thermocouples
- Thermopiles
- Flame rods
- Photoelectric cells
Thermocouples
- A thermocouple consists of two dissimilar wires welded together at one end to form a measuring (or “hot”) junction.
- The opposite ends are connected to an electric circuit, called the reference (or “cold”) junction.
- When the hot junction is exposed to a flame, its temperature increases above that of the cold junction, generating a small voltage (about 20 to 30 millivolts).
- This voltage energizes a sensitive relay, called a pilotstat, which may be built into an SSOV (Safety Shut-Off Valve).
- Thermocouples are limited to pilot burners up to 120 kW input due to their slow flame failure response time (up to 90 seconds).
Thermopiles
- A thermopile is a flame detector that develops sufficient voltage to operate an SSOV independently from any external power source.
- It consists of multiple thermocouples in series, generating around 750 millivolts.
- Thermopiles are also limited to burners not exceeding 120 kW input.
- They offer the advantage of operating without external power, making them suitable for small residential boilers.
Flame Rods
- A flame rod is a flame detection device that operates on the principle that flames can conduct electricity.
- It consists of two electrodes (the flame rod and the burner) and the flame, which conducts electricity between them.
- The flame rod is a heat-resistant, small diameter metal rod, supported by a ceramic holder that keeps the rod electrically insulated from the burner.
- Flame rods are commonly used with gas burners and are suitable for burners over 120 kW input due to their fast flame failure response time.
Photoelectric Cells
- A photoelectric cell is a device that reacts to infrared, ultraviolet, or visible light emitted by fire.
- Common types of photocells include:
- Infrared scanner
- Ultraviolet scanner
- Rectifying photocell
- A scanner is mounted on the boiler in such a way that it can observe the flame, and its resistance decreases with an increase in the amount of infrared light it receives from the flame.
- When a flame failure occurs, the scanner does not sense a flame, and its resistance increases, causing the flame relay to open, which shuts off the fuel to the burner.
Case Study
- A case study highlights the importance of proper installation and maintenance of flame safeguard controls to avoid false readings and potential explosions.
Flame Failure Detection Methods
- Various methods are used to detect flame failure in boilers, including:
- Thermocouples
- Thermopiles
- Flame rods
- Photoelectric cells
Thermocouples
- A thermocouple consists of two dissimilar wires welded together at one end to form a measuring (or “hot”) junction.
- The opposite ends are connected to an electric circuit, called the reference (or “cold”) junction.
- When the hot junction is exposed to a flame, its temperature increases above that of the cold junction, generating a small voltage (about 20 to 30 millivolts).
- This voltage energizes a sensitive relay, called a pilotstat, which may be built into an SSOV (Safety Shut-Off Valve).
- Thermocouples are limited to pilot burners up to 120 kW input due to their slow flame failure response time (up to 90 seconds).
Thermopiles
- A thermopile is a flame detector that develops sufficient voltage to operate an SSOV independently from any external power source.
- It consists of multiple thermocouples in series, generating around 750 millivolts.
- Thermopiles are also limited to burners not exceeding 120 kW input.
- They offer the advantage of operating without external power, making them suitable for small residential boilers.
Flame Rods
- A flame rod is a flame detection device that operates on the principle that flames can conduct electricity.
- It consists of two electrodes (the flame rod and the burner) and the flame, which conducts electricity between them.
- The flame rod is a heat-resistant, small diameter metal rod, supported by a ceramic holder that keeps the rod electrically insulated from the burner.
- Flame rods are commonly used with gas burners and are suitable for burners over 120 kW input due to their fast flame failure response time.
Photoelectric Cells
- A photoelectric cell is a device that reacts to infrared, ultraviolet, or visible light emitted by fire.
- Common types of photocells include:
- Infrared scanner
- Ultraviolet scanner
- Rectifying photocell
- A scanner is mounted on the boiler in such a way that it can observe the flame, and its resistance decreases with an increase in the amount of infrared light it receives from the flame.
- When a flame failure occurs, the scanner does not sense a flame, and its resistance increases, causing the flame relay to open, which shuts off the fuel to the burner.
Case Study
- A case study highlights the importance of proper installation and maintenance of flame safeguard controls to avoid false readings and potential explosions.
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Description
Learn about the different methods used to detect flame failure in boilers, including thermocouples, thermopiles, flame rods, and photoelectric cells.