When is a boiler typically considered to have a "failure"?

A boiler is typically considered to have a "failure" when it fails to function safely or efficiently. This encompasses various scenarios where the boiler does not meet operational standards, which can lead to hazards such as overheating, pressure build-up, or even potential explosions.

Safety is paramount in boiler operation, and any failure to function within safe parameters indicates a serious issue that may endanger both equipment and personnel. Additionally, efficiency losses can also imply that the boiler is not operating effectively, further emphasizing the importance of the correct functioning of heating systems.

The other options present scenarios that do not inherently indicate a failure. Operating at lower temperatures or high pressure might be normal for certain operational contexts, and producing excessive steam could sometimes be a part of specific processes, as long as it operates safely. Thus, the critical factor in defining a boiler's failure is its inability to operate in a manner that ensures safety and efficiency.