25 Questions
What is required for steam boilers not continuously attended by a certified operator according to CSA-B51 6.3.2.1?
At least two low-water fuel cut-off devices
What does it mean when the installation of low-water fuel cut-off devices 'cannot be rendered inoperative'?
No valves or switches may be installed that interfere with the operation of the control
Why may large capacity boilers be required to run continuously?
To prevent negative consequences for plant operations
What is installed in parallel to the low water cut-off switch to blow down the low water cut-off without tripping the boiler?
Momentary contact switch
What must the operator maintain pressure on during a blowdown to restore the operation of the low water cut-off control?
Pushbutton switch
How many low-water fuel cut-off devices are required for steam boilers according to ASME codes?
At least one
What are the consequences of not equipping steam boilers with low-water fuel cut-off devices as per CSA-B51 6.3.2.1?
Negative impact on plant operations
'Cannot be rendered inoperative' means that no ____ may be installed on the low water cut-off piping.
Valves
What does CSA B51 require regarding the flow-sensing device for hot water boilers?
To be installed at the hot water outlet
How does CSA B51 define a boiler's capacity?
By not defining capacity
What is the requirement for testing low water cut-offs of hot water boilers according to Part HG-614?
Testing should not render the device inoperable
What is the purpose of having independent water connections for low-water fuel cut-offs in steam boilers?
To prevent plugging of both cut-offs simultaneously
Where can the low-water fuel cutoff be located for hot-water heating boilers according to ASME CSD-1 Part CW-130?
Above the lowest safe permissible water level
What is recommended for low water cut-off testing frequencies and procedures in heating and power boilers according to ASME BPVC VII and CSD-1?
Recommended testing frequencies and procedures are provided
Why does ASME CSD-1 require each low-water fuel cutoff to be installed in individual chambers (water columns) for high-pressure steam boilers?
To facilitate internal inspection and cleaning
According to ASME CSD-1 Part CW-120, what must be done if the two cut-off devices share a common water connection in low-pressure steam boilers?
'Test and check' valves must be installed
'One cut-off control shall be set to function ahead of the other' according to ASME CSD-1 Part CW-120. What is the purpose of this requirement?
To prevent overloading of the control system
According to CSA-B51 6.3.2.2, what is the requirement for automatically fired hot water boilers not continuously attended by a certified operator?
They must be equipped with a low-water fuel cut-off device that can be tested under operational conditions.
In ASME BPVC I, what is the requirement for low water cut-offs on fuel-fired or waste heat fired boilers?
Low water cut-offs are not required on any type of boilers.
What does ASME VII Part C5.100 recommend for each automatically fired boiler?
Two independent low water cut-offs are recommended.
Regarding modular steam heating boilers, what is the requirement for each module according to ASME rules?
Each module should have a low water cutoff.
What is the purpose of special “test and check” fittings in hot water boilers?
To prevent the system from draining while testing the low water cut-off.
In ASME IV, what is the restriction regarding shutoff valves in the interconnecting piping of the LWCO?
Shutoff valves of any type shall not be placed in such pipe.
According to CSA-B51 6.2.2.3, what is the requirement for hot water boilers requiring forced circulation to prevent overheating?
They must be equipped with a flow-sensing device to automatically cut off the fuel supply if the flow rate is reduced.
What is the requirement for electric boilers of the resistance element type according to ASME BPVC I, Part PEB-13.2?
They must be equipped with an automatic low-water cutoff on each boiler pressure vessel.
Study Notes
Steam Boilers Requirements
- For steam boilers not continuously attended by a certified operator, a low-water fuel cut-off device is required according to CSA-B51 6.3.2.1.
- This device cannot be rendered inoperative, meaning no valves or other devices can be installed on the low water cut-off piping.
Large Capacity Boilers
- Large capacity boilers may be required to run continuously to ensure a stable supply of steam.
Low-Water Cut-Off Devices
- Two low-water fuel cut-off devices are required for steam boilers according to ASME codes.
- The purpose of having independent water connections for low-water fuel cut-offs is to ensure reliable operation.
- A manual reset valve is installed in parallel to the low water cut-off switch to blow down the low water cut-off without tripping the boiler.
Operator Responsibilities
- During a blowdown, the operator must maintain pressure on the manual reset valve to restore the operation of the low water cut-off control.
Consequences of Non-Compliance
- Failure to equip steam boilers with low-water fuel cut-off devices as per CSA-B51 6.3.2.1 can result in serious consequences, including accidents and damage.
Hot Water Boilers
- For hot water boilers, CSA B51 requires a flow-sensing device to detect low water levels.
- A boiler's capacity is defined as the heat output in BTUs per hour according to CSA B51.
- Low water cut-offs in hot water boilers must be tested according to Part HG-614.
Location of Low-Water Fuel Cut-Off
- For hot-water heating boilers, the low-water fuel cut-off can be located in the boiler or in a separate chamber according to ASME CSD-1 Part CW-130.
Testing and Maintenance
- ASME BPVC VII and CSD-1 recommend testing low water cut-offs regularly, with detailed procedures and frequencies.
- Each low-water fuel cutoff should be installed in individual chambers (water columns) for high-pressure steam boilers to ensure reliable operation according to ASME CSD-1.
Special Requirements
- For low-pressure steam boilers, if the two cut-off devices share a common water connection, one cut-off control must be set to function ahead of the other according to ASME CSD-1 Part CW-120.
- This requirement ensures that the boiler is shut down in a safe and controlled manner.
- Modular steam heating boilers must have each module equipped with a low-water fuel cut-off device according to ASME rules.
Electric Boilers
- Electric boilers of the resistance element type require special precautions, including a control system to prevent overheating according to ASME BPVC I, Part PEB-13.2.
Shutoff Valves
- In ASME IV, shutoff valves are restricted in the interconnecting piping of the LWCO to prevent accidental shutdown.
Forced Circulation
- Hot water boilers requiring forced circulation to prevent overheating must meet specific requirements according to CSA-B51 6.2.2.3.
Test your knowledge of the requirements for low-water fuel cut-off devices in steam boilers according to CSA B51 Boiler, Pressure Vessel, and Pressure Piping Code. This quiz covers the regulations outlined in CSA-B51 6.3.2.1.
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