Which of the following conditions indicates conveyor overload?

The condition that indicates conveyor overload is reflected in the choice regarding uneven spaces between the top plates of the conveyor chain. When a conveyor system is overloaded, it may experience an increase in tension and strain on its components, which can result in uneven spacing as the chain struggles to manage the excessive weight. This uneven spacing may signal misalignment or stress, which are direct consequences of the system being tasked beyond its intended capacity.

Frequent jams can occur for various reasons, including mechanical failures or operational issues, but they do not exclusively indicate overload. Noisy operation can also arise from several factors, such as wear or lack of lubrication. Excessive vibration may suggest misalignment or other mechanical issues, but like noise, it can occur without necessarily implying that the system is overloaded.

Therefore, identifying uneven spacing in the chain is a clear indicator of potential overload conditions, as it directly relates to the strain and operational limits being exceeded in the conveyor system.