While you can safely operate the engines at up to 100% of the power level, there is also a requirement to operate at a range of powers levels.
An upper range of 109% has been set as a temporary override to the engine limits. This may be run for up to 600 seconds of operation.
Actual flight performance has not been tested beyond time and power levels for more than 600 seconds. Exceeding this can permanently damage the vehicle.
The primary computer system monitors the temperature of the turbopump components including:
•high pressure fuel pump
•high pressure oxidizer
•high pressure pump at low temperature
Temperatures exceeding operating limits will result in a main engine shutdown. If the captain has manually prevented this the temperature can be forced to exceed limits.