BOC Boiler Systems and Steam 3

Question 1

What is the purpose of a modulating burner in a boiler?

Accepted Answer

To vary the firing rate to match the heating load rather than cycling on/off

Answer

To alternate between two fuels automatically

Answer

To preheat combustion air using burner exhaust

Answer

To increase burner capacity during peak demand

Question 2

Water hammer in a steam system is most commonly caused by:

Accepted Answer

Steam contacting condensate, causing rapid condensation and pressure shock

Answer

Excessive steam pressure in the distribution main

Answer

Oversized steam traps releasing too much condensate at once

Answer

Air binding in the return lines

Question 3

What is the correct sequence for safely shutting down a steam boiler for maintenance?

Accepted Answer

Reduce load gradually, shut off fuel, allow natural cooldown, then drain when cool

Answer

Shut off fuel, open all vents, then drain immediately

Answer

Shut off feedwater, then shut off fuel immediately

Answer

Open safety valve, shut off fuel, drain immediately while hot

Question 4

A boiler's 'combustion efficiency' is best improved by:

Accepted Answer

Optimizing the air-to-fuel ratio to minimize excess air while ensuring complete combustion

Answer

Increasing fuel pressure to the burner

Answer

Running the boiler at maximum rated capacity at all times

Answer

Increasing stack draft to remove flue gases faster

Question 5

What is the significance of the MAWP on a boiler nameplate?

Accepted Answer

Maximum Allowable Working Pressure — the highest safe operating pressure for that vessel

Answer

Minimum Adjusted Water Pressure — the lowest acceptable feedwater pressure

Answer

Maximum Automatic Water Purge — the blowdown cycle limit

Answer

Mean Annual Working Performance — the efficiency rating

Question 6

Which type of steam trap operates using the difference in temperature between steam and condensate?

Accepted Answer

Thermostatic trap

Answer

Float and thermostatic trap

Answer

Inverted bucket trap

Answer

Disc trap

Question 7

When performing a boiler inspection, a technician finds the sight glass is dirty and hard to read. The correct action is to:

Accepted Answer

Blow down the sight glass using the drain valve to clear sediment and verify level

Answer

Estimate the water level based on feedwater pump runtime

Answer

Shut down the boiler immediately as the sight glass is a critical safety device

Answer

Replace the sight glass during the next scheduled annual shutdown