What are common signs of overheating in machinery?

The correct choice emphasizes the indicators that suggest machinery is experiencing overheating, which are critical for identifying potential failures and ensuring proper maintenance. Increased operating temperature is a direct sign of overheating, as machinery typically operates within a specific temperature range. When temperatures exceed this range, it can lead to damage or decreased efficiency.

Unusual noises, such as grinding or whining, can indicate that internal components are under stress or experiencing friction due to lubrication breakdown from high temperatures. Lastly, the smell of burning is a clear signal of overheating and can also indicate melting of insulation or other materials, which can lead to severe damage if not addressed.

In contrast, the other options mention scenarios that are not typically associated with overheating. Increased output and reduced noise suggest efficient operation instead of a problem. Frequent maintenance requests and low energy consumption do not specifically relate to machinery overheating and can represent other operational issues. Complete system shutdowns and overcooling may suggest other faults, as they do not align with the gradual indicators or signs of overheating but rather indicate that the system is not operating as intended. Thus, recognizing the specific signs highlighted in choice B is essential for maintaining machinery health and preventing failure.