Podcast
Questions and Answers
EASY What is the purpose of a thermocouple in a boiler?
EASY What is the purpose of a thermocouple in a boiler?
- To control the fuel input
- To measure the temperature of the furnace
- To detect flame failure (correct)
- To generate a large voltage
What is the limitation of thermocouple flame safeguards?
What is the limitation of thermocouple flame safeguards?
- They are difficult to install
- They are expensive
- They have a slow flame failure response time (correct)
- They are unreliable
What is the typical voltage generated by a thermocouple?
What is the typical voltage generated by a thermocouple?
- 100 millivolts
- 20 to 30 millivolts (correct)
- 5 volts
- 1 volt
What is the function of the pilotstat in a thermocouple circuit?
What is the function of the pilotstat in a thermocouple circuit?
What is the purpose of the cold junction in a thermocouple?
What is the purpose of the cold junction in a thermocouple?
What is the material used for the outer sheath of a thermocouple?
What is the material used for the outer sheath of a thermocouple?
What happens when the thermocouple voltage drops below 7 millivolts?
What happens when the thermocouple voltage drops below 7 millivolts?
What is the maximum input of a boiler that can use a thermocouple flame safeguard?
What is the maximum input of a boiler that can use a thermocouple flame safeguard?
What is the name of the valve body that combines a gas pressure regulator, safety shut-off valve, and manual gas valve?
What is the name of the valve body that combines a gas pressure regulator, safety shut-off valve, and manual gas valve?
What is the purpose of a pilotstat?
What is the purpose of a pilotstat?
What is the typical voltage generated by a thermocouple?
What is the typical voltage generated by a thermocouple?
What is the purpose of a thermopile?
What is the purpose of a thermopile?
What is the principle of operation of a flame rod?
What is the principle of operation of a flame rod?
What is the purpose of a limit switch in an SSOV circuit?
What is the purpose of a limit switch in an SSOV circuit?
What is the advantage of a millivolt system?
What is the advantage of a millivolt system?
What is the purpose of a safety shut-off valve?
What is the purpose of a safety shut-off valve?
What is the typical input range of combination gas valves?
What is the typical input range of combination gas valves?
How does a flame rod detect a flame?
How does a flame rod detect a flame?
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?
What type of light is emitted by the igniter sparks in a firetube boiler burner assembly?
What type of light is emitted by the igniter sparks in a firetube boiler burner assembly?
What is the recommended maximum temperature for mounting a UV scanner in a firetube boiler burner assembly?
What is the recommended maximum temperature for mounting a UV scanner in a firetube boiler burner assembly?
What is the function of the cathode in a rectifying photocell?
What is the function of the cathode in a rectifying photocell?
What happens when the flame fails in a rectifying photocell?
What happens when the flame fails in a rectifying photocell?
What is the purpose of the pilot flame in a firetube boiler burner assembly?
What is the purpose of the pilot flame in a firetube boiler burner assembly?
Why did the scanner detect a flame signal in the case study?
Why did the scanner detect a flame signal in the case study?
Where is the rectifying photocell often mounted in small packaged oil burners?
Where is the rectifying photocell often mounted in small packaged oil burners?
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?
What causes the DC flow from the burner to the flame rod in a flame rod system?
What causes the DC flow from the burner to the flame rod in a flame rod system?
What happens if the flame rod is accidentally grounded to the burner?
What happens if the flame rod is accidentally grounded to the burner?
What is the role of the relay in a basic flame rod system?
What is the role of the relay in a basic flame rod system?
What is the advantage of using flame rods over thermocouples and thermopiles?
What is the advantage of using flame rods over thermocouples and thermopiles?
What is the purpose of a photoelectric cell in a flame monitoring system?
What is the purpose of a photoelectric cell in a flame monitoring system?
What type of photocell is used in the scanner illustrated in Figure 15?
What type of photocell is used in the scanner illustrated in Figure 15?
What happens to the resistance of the lead-sulfide cell when it receives an increase in the amount of infrared light?
What happens to the resistance of the lead-sulfide cell when it receives an increase in the amount of infrared light?
What is the purpose of the electronic amplifier in an infrared scanner?
What is the purpose of the electronic amplifier in an infrared scanner?
What happens to the power supply to the main SSOV when a flame failure occurs in an infrared scanner system?
What happens to the power supply to the main SSOV when a flame failure occurs in an infrared scanner system?
MEDIUM What is the reason thermocouples are limited in use to pilot burners for small boilers?
MEDIUM What is the reason thermocouples are limited in use to pilot burners for small boilers?
What is the function of the cold junction in a thermocouple?
What is the function of the cold junction in a thermocouple?
What is the purpose of the outer copper sheath in a thermocouple?
What is the purpose of the outer copper sheath in a thermocouple?
What happens when the thermocouple voltage drops below 7 millivolts?
What happens when the thermocouple voltage drops below 7 millivolts?
What is the typical voltage generated by a thermocouple?
What is the typical voltage generated by a thermocouple?
What is the function of the pilotstat in a thermocouple circuit?
What is the function of the pilotstat in a thermocouple circuit?
What is the purpose of the inner wire in a thermocouple?
What is the purpose of the inner wire in a thermocouple?
What occurs when the hot junction is exposed to a flame in a thermocouple?
What occurs when the hot junction is exposed to a flame in a thermocouple?
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?
Why did the scanner detect a flame signal in the case study?
Why did the scanner detect a flame signal in the case study?
What type of light is emitted by the igniter sparks in a firetube boiler burner assembly?
What type of light is emitted by the igniter sparks in a firetube boiler burner assembly?
Where is the rectifying photocell often mounted in small packaged oil burners?
Where is the rectifying photocell often mounted in small packaged oil burners?
What happens when the flame fails in a rectifying photocell?
What happens when the flame fails in a rectifying photocell?
What is the function of the cathode in a rectifying photocell?
What is the function of the cathode in a rectifying photocell?
What is the recommended maximum temperature for mounting a UV scanner in a firetube boiler burner assembly?
What is the recommended maximum temperature for mounting a UV scanner in a firetube boiler burner assembly?
What is the principle of operation of a UV scanner?
What is the principle of operation of a UV scanner?
What is the purpose of a combination gas valve?
What is the purpose of a combination gas valve?
What is the function of a pilotstat?
What is the function of a pilotstat?
What is the typical input range of boilers that can use thermocouples or thermopiles?
What is the typical input range of boilers that can use thermocouples or thermopiles?
What is the principle of operation of a flame rod?
What is the principle of operation of a flame rod?
What is the purpose of a limit switch in an SSOV circuit?
What is the purpose of a limit switch in an SSOV circuit?
What is the advantage of a millivolt system?
What is the advantage of a millivolt system?
What is the purpose of the manual reset button on a combination gas valve?
What is the purpose of the manual reset button on a combination gas valve?
What happens when the thermocouple voltage drops below a certain threshold?
What happens when the thermocouple voltage drops below a certain threshold?
What is the purpose of a thermopile?
What is the purpose of a thermopile?
What is the typical voltage generated by a thermopile?
What is the typical voltage generated by a thermopile?
What is the reason for pulsating DC current in a flame rod system?
What is the reason for pulsating DC current in a flame rod system?
What happens if the flame rod is accidentally grounded to the burner in a flame rod system?
What happens if the flame rod is accidentally grounded to the burner in a flame rod system?
What is the function of the relay in a basic flame rod system?
What is the function of the relay in a basic flame rod system?
What is the advantage of using flame rods over thermocouples and thermopiles?
What is the advantage of using flame rods over thermocouples and thermopiles?
What is the purpose of a photoelectric cell in a flame monitoring system?
What is the purpose of a photoelectric cell in a flame monitoring system?
What type of photocell is used in the scanner illustrated in Figure 15?
What type of photocell is used in the scanner illustrated in Figure 15?
What happens to the resistance of the lead-sulfide cell when it receives an increase in the amount of infrared light?
What happens to the resistance of the lead-sulfide cell when it receives an increase in the amount of infrared light?
What is the purpose of the electronic amplifier in an infrared scanner?
What is the purpose of the electronic amplifier in an infrared scanner?
What happens when a flame failure occurs in an infrared scanner system?
What happens when a flame failure occurs in an infrared scanner system?
What is the purpose of the sighting tube in a photoelectric cell?
What is the purpose of the sighting tube in a photoelectric cell?
HARD What is the primary reason for the limitation of thermocouple flame safeguards to small boilers?
HARD What is the primary reason for the limitation of thermocouple flame safeguards to small boilers?
What is the purpose of the reference junction in a thermocouple circuit?
What is the purpose of the reference junction in a thermocouple circuit?
What is the effect of the hot junction being exposed to a flame in a thermocouple?
What is the effect of the hot junction being exposed to a flame in a thermocouple?
What is the function of the outer copper sheath in a thermocouple?
What is the function of the outer copper sheath in a thermocouple?
What is the purpose of the pilotstat in a thermocouple circuit?
What is the purpose of the pilotstat in a thermocouple circuit?
What happens when the thermocouple voltage drops below 7 millivolts in a thermocouple circuit?
What happens when the thermocouple voltage drops below 7 millivolts in a thermocouple circuit?
What is the purpose of the inner wire in a thermocouple?
What is the purpose of the inner wire in a thermocouple?
What is the primary advantage of using thermocouples over other flame detection methods?
What is the primary advantage of using thermocouples over other flame detection methods?
What is the primary reason why flame rods are used in burners over 120 kW input?
What is the primary reason why flame rods are used in burners over 120 kW input?
What is the effect of soot bridging on a flame rod system?
What is the effect of soot bridging on a flame rod system?
What is the purpose of the threaded ring in a photoelectric cell installation?
What is the purpose of the threaded ring in a photoelectric cell installation?
What happens to the resistance of the lead-sulfide cell when it receives an increase in the amount of infrared light?
What happens to the resistance of the lead-sulfide cell when it receives an increase in the amount of infrared light?
What is the purpose of the electronic amplifier in an infrared scanner system?
What is the purpose of the electronic amplifier in an infrared scanner system?
What happens when the flame rod is accidentally grounded to the burner?
What happens when the flame rod is accidentally grounded to the burner?
What is the primary function of the relay in a basic flame rod system?
What is the primary function of the relay in a basic flame rod system?
What is the effect of carbon deposits on a flame rod system when used with oil-fired burners?
What is the effect of carbon deposits on a flame rod system when used with oil-fired burners?
What is the primary advantage of using flame rods over thermocouples and thermopiles?
What is the primary advantage of using flame rods over thermocouples and thermopiles?
What is the purpose of the sight tube in a photoelectric cell installation?
What is the purpose of the sight tube in a photoelectric cell installation?
What is the primary reason for using a thermopile instead of a thermocouple in a millivolt system?
What is the primary reason for using a thermopile instead of a thermocouple in a millivolt system?
Which of the following components is NOT typically included in a combination gas valve?
Which of the following components is NOT typically included in a combination gas valve?
What is the primary function of the pilotstat manual reset button?
What is the primary function of the pilotstat manual reset button?
What is the primary advantage of a millivolt system over a traditional electrical power source?
What is the primary advantage of a millivolt system over a traditional electrical power source?
What is the primary function of the flame rod in a flame detection system?
What is the primary function of the flame rod in a flame detection system?
What is the primary reason for using a limit switch in an SSOV circuit?
What is the primary reason for using a limit switch in an SSOV circuit?
What is the primary function of the thermocouple in a thermocouple circuit?
What is the primary function of the thermocouple in a thermocouple circuit?
What is the primary disadvantage of using a thermocouple in a millivolt system?
What is the primary disadvantage of using a thermocouple in a millivolt system?
What is the primary function of the pilotstat in a combination gas valve?
What is the primary function of the pilotstat in a combination gas valve?
What is the primary advantage of using a flame rod over a thermocouple or thermopile?
What is the primary advantage of using a flame rod over a thermocouple or thermopile?
What is the reason for placing the UV scanner as close as possible to the flame?
What is the reason for placing the UV scanner as close as possible to the flame?
What was the likely cause of the scanner detecting a flame signal in the case study?
What was the likely cause of the scanner detecting a flame signal in the case study?
What is the primary function of the cathode in a rectifying photocell?
What is the primary function of the cathode in a rectifying photocell?
What is the purpose of angling the scanner sight tube?
What is the purpose of angling the scanner sight tube?
What happens when the flame fails in a rectifying photocell?
What happens when the flame fails in a rectifying photocell?
Why do newer burner management systems distinguish between sparks and flames?
Why do newer burner management systems distinguish between sparks and flames?
What is the benefit of using a UV scanner over other flame detection methods?
What is the benefit of using a UV scanner over other flame detection methods?
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?
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
This quiz covers various methods used to detect flame failure in boilers, including thermocouples, thermopiles, flame rods, and photoelectric cells.
