BOC Boiler Systems and Steam 1 — Questions and Answers
Question 1: What is the primary purpose of a boiler low-water cutoff?
- To regulate steam pressure
- To shut down the burner if water level drops too low (Correct answer)
- To control feedwater temperature
- To prevent steam from entering the water supply
Correct answer: To shut down the burner if water level drops too low
A low-water cutoff automatically shuts off the burner when water drops below a safe operating level to prevent overheating and damage to the boiler.
Question 2: Which type of boiler operates at steam pressures above 15 psig?
- Low-pressure boiler
- High-pressure boiler (Correct answer)
- Hot water boiler
- Condensate boiler
Correct answer: High-pressure boiler
High-pressure boilers are defined as those operating at steam pressures exceeding 15 psig, requiring more stringent safety and licensing requirements.
Question 3: What does the term 'blowdown' refer to in boiler operation?
- Releasing excess steam pressure through a safety valve
- Removing accumulated solids and impurities from boiler water (Correct answer)
- Purging combustion gases from the firebox
- Draining condensate from steam traps
Correct answer: Removing accumulated solids and impurities from boiler water
Blowdown removes dissolved and suspended solids that concentrate in boiler water, preventing scale buildup and maintaining water quality.
Question 4: What is the function of a steam trap?
- To increase steam pressure in distribution lines
- To prevent steam from entering the condensate return line
- To discharge condensate and non-condensable gases while retaining steam (Correct answer)
- To separate steam from feedwater
Correct answer: To discharge condensate and non-condensable gases while retaining steam
Steam traps automatically discharge condensate and air from steam lines while blocking the passage of live steam, maintaining system efficiency.
Question 5: A boiler's Hartford Loop is designed to protect against:
- Overpressure conditions
- Siphoning of water out of the boiler (Correct answer)
- Excessive flue gas temperatures
- Waterlogging of steam radiators
Correct answer: Siphoning of water out of the boiler
The Hartford Loop prevents gravity-fed water from siphoning back out of the boiler through a return line leak, which could expose the heating elements.
Question 6: What does a boiler's 'stack temperature' indicate about combustion efficiency?
- Higher stack temperatures always indicate better combustion
- Lower stack temperatures generally indicate more heat is being extracted from the combustion gases (Correct answer)
- Stack temperature has no relationship to combustion efficiency
- Optimal stack temperature is above 600°F for all boiler types
Correct answer: Lower stack temperatures generally indicate more heat is being extracted from the combustion gases
Lower flue gas (stack) temperatures indicate that more heat is being transferred to the water, improving combustion efficiency and reducing energy waste.
Question 7: Which chemical is commonly added to boiler feedwater to prevent oxygen corrosion?
- Sodium chloride
- Sodium sulfite or hydrazine (Correct answer)
- Calcium carbonate
- Muriatic acid
Correct answer: Sodium sulfite or hydrazine
Oxygen scavengers such as sodium sulfite or hydrazine react with dissolved oxygen in feedwater, preventing pitting corrosion on boiler metal surfaces.
BOC Boiler Systems and Steam 1
What is the primary purpose of a boiler low-water cutoff?