A boiler test shall be conducted with a boiler load change of 70% in 45 seconds, ranging from 15 to what % of full boiler power?

The question focuses on a boiler test that involves adjusting the load quickly and specifies that a 70% change in boiler load is to occur within a 45-second timeframe. The critical aspect to focus on is the calculation of the maximum percentage of full boiler power that one can achieve, given the lower limit of 15%.

To determine the upper limit of boiler power, one can add 70% to the lower limit of 15%. This calculation provides the following:

• Starting at 15% full power,

• A change of 70% means you compute 15% + 70% of the total capacity of the boiler.

The total maximum capability reaches:

• If the total percentage we can achieve is not supposed to exceed 100%, then we calculate:

• 15% + 70% = 85%.

Since this percentage calculation reaches a maximum threshold before hitting the ceiling of 100%, the next logical percentage that allows for a 70% increase from the starting point of 15% is 90%. Therefore, while many options were presented, the percentage of 95% would mean a load that is not achievable within the limits described when starting from 15%.

Thus, the correct answer allows for the operational understanding that