What is a potential danger when bringing a boiler online with significantly higher steam pressure?

Bringing a boiler online with significantly higher steam pressure can lead to priming and carryover. Priming occurs when the steam generated in the boiler is not pure and carries water droplets along with it into the steam system. This can happen due to excessive pressure that causes rapid formation of steam bubbles, leading to instability within the boiler.

When carryover occurs, water that has not been fully evaporated travels with the steam into the piping and potentially into turbines or other equipment downstream. This can result in a variety of operational problems, such as reduced efficiency, potential damage to components, and interference with the safe operation of auxiliary equipment.

By contrast, other options present issues that are not directly tied to the specific act of raising steam pressure significantly. System leakage could occur under high pressure but is more related to mechanical integrity rather than steam formation dynamics. Cooling system failure relates to the inability to maintain an adequate heat exchange process which is not necessarily a direct consequence of raising steam pressure. Similarly, fuel combustion issues could arise, but they typically relate more to the fuel system's performance than to the steam pressure when the boiler starts up. Thus, the primary concern with high steam pressure during boiler startup is indeed priming and carryover.