In a multi-valve turbine, what is true about the throttle valves?

Throttle valves in a multi-valve turbine are designed to regulate the flow of steam into the turbine, and their balancing properties play a crucial role in this process. When they are double seated and balanced, it means that the design allows for equal pressure on both sides of the valve, which helps reduce the force required to open or shut the valve. This balance minimizes wear and tear and allows for smoother operation within the steam system.

A double-seated design is advantageous because it enables the valve to close quickly and maintain a tight seal, which is vital for the efficient operation of a turbine. Proper regulation of steam flow is essential to optimize performance and prevent damage to the turbine from excessive pressure variations.

Other options presented do not accurately characterize the operation and role of throttle valves in this context. For example, single-seated valves may not provide the same level of efficiency in steam regulation, while stating that the valves only control steam for backing pressure overlooks their primary function of managing the steam flow into the turbine across a broader operational range. Additionally, throttle valves are typically present at different points in the system, not restricted solely to the high-pressure end, which demonstrates their significant role throughout the entire turbine mechanism.