Boiler Systems and Steam Flashcards
7 cards from real BOC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Boiler Systems and Steam flashcards as text
What is the purpose of a modulating burner in a boiler?
Answer: To vary the firing rate to match the heating load rather than cycling on/off
A modulating burner adjusts its firing rate proportionally to the heating demand, improving efficiency and temperature stability compared to simple on/off cycling.
Water hammer in a steam system is most commonly caused by:
Answer: Steam contacting condensate, causing rapid condensation and pressure shock
Water hammer occurs when high-velocity steam contacts accumulated condensate, collapsing rapidly and creating a pressure shockwave that can damage pipes and fittings.
What is the correct sequence for safely shutting down a steam boiler for maintenance?
Answer: Reduce load gradually, shut off fuel, allow natural cooldown, then drain when cool
Gradual cooldown prevents thermal shock to boiler components; the boiler must be cool before draining to avoid injury and damage from sudden contraction.
A boiler's 'combustion efficiency' is best improved by:
Answer: Optimizing the air-to-fuel ratio to minimize excess air while ensuring complete combustion
Correct air-to-fuel ratio minimizes heat loss from excess air while ensuring all fuel is burned completely, which is the primary lever for improving combustion efficiency.
What is the significance of the MAWP on a boiler nameplate?
Answer: Maximum Allowable Working Pressure — the highest safe operating pressure for that vessel
MAWP (Maximum Allowable Working Pressure) is stamped on the boiler by the manufacturer and represents the highest pressure at which the vessel is legally permitted to operate.
Which type of steam trap operates using the difference in temperature between steam and condensate?
Answer: Thermostatic trap
Thermostatic steam traps use temperature-sensitive elements that open to discharge cooler condensate and close when steam (at a higher temperature) is present.
When performing a boiler inspection, a technician finds the sight glass is dirty and hard to read. The correct action is to:
Answer: Blow down the sight glass using the drain valve to clear sediment and verify level
Blowing down the sight glass by briefly opening its drain valve flushes sediment and verifies that the glass is connected properly, restoring an accurate water level reading.