A procedure in which the speed of a turbine is held constant for a specified length of time; a method used to bring steam-to-metal temperature mismatches back to normal.

• A. Heat soak
• B. Slow ramp
• C. Isothermal hold
• D. Temperature equalization

Answer: (A)

A heat soak is a procedure where the turbine speed is held constant for a set period to let heat move through the system and bring steam-to-metal temperature differences toward balance. Keeping the speed steady stabilizes heat input from the steam, giving hotter and cooler areas time to come to the same temperature. This helps reduce thermal stresses and distortion caused by uneven heating as components respond to steam temperatures. The goal is to dampen temperature gradients so the turbine can operate more safely and reliably. Other terms describe related ideas or different approaches, but the essence here is using a controlled, steady condition to achieve temperature uniformity in the metal.