What is checked to assess the HP turbine for boiler water carryover after a boiler high water casualty?

The correct choice pertains to the turbine casing drains. After a high water casualty in the boiler, it's crucial to check the turbine casing drains to determine if any water has carried over into the steam system. Water carryover can cause significant damage to the turbine due to the sudden influx of liquid in a system designed for steam, which can lead to issues such as water hammer or erosion.

Inspecting the turbine casing drains allows for verification of the presence of boiler water in the steam supply. If water is found in these drains, it serves as an indication of boiler water carryover, prompting necessary actions to mitigate potential damage to the turbine and associated systems.

While the other options—steam trap, pressure gauge, and boiler feed pump—play important roles in boiler and turbine operations, they do not directly assess the situation of water carryover following a high water incident. Steam traps are meant to remove condensed steam, pressure gauges monitor system pressures, and the boiler feed pump manages water supply to the boiler but do not provide information on water carried over into the steam line.