Which is NOT a method used to check a safety valve's capacity?

Visual inspection is primarily used to assess the physical condition of a safety valve rather than its capacity to relieve pressure. While visual inspections are critical in identifying visible defects, leaks, corrosion, or other physical issues that might affect the functioning of the safety valve, they do not provide information about how much pressure the valve can safely release when activated.

In contrast, the other methods listed focus on evaluating the actual performance of the safety valve. The accumulation test measures the pressure rise in the system under specific conditions to ensure the valve can handle excess pressure. The maximum amount of fuel burned refers to the operational parameters of the boiler, which impact how the safety valve functions under maximum load scenarios. Similarly, determining the maximum evaporative capacity of feed water is essential, as it provides insight into the system's steam generation under peak operational conditions, which directly relates to the safety valve's expected performance.

Overall, the key distinction is that while visual inspection is an important maintenance practice, it does not assess the valve's operational capacity, which is why it stands out as the method not used to check a safety valve's capacity.