What is the purpose of a trip-N-throttle valve?

• A. To control how much steam enters the turbine; it is two valves in one: throttle valve and trip valve for over speed
• B. To regulate how steam is condensed in the condenser
• C. To vent steam to atmosphere during startup
• D. To measure steam quality before entering the turbine

Answer: (A)

The key idea is that this valve bundle serves both normal control and safety. The throttle portion modulates how much steam gets to the turbine, letting the operator match steam flow to the load and keep the turbine running at the desired speed. The trip portion is a fast-acting safety valve that can close quickly to stop steam flow if the turbine riskily threatens to overspeed or if another fault is detected. By combining these two functions in one valve, you get smooth, controllable steam admission under normal operation plus an immediate shutdown mechanism to protect the turbine and generator. It isn’t used to condense steam in the condenser, vent steam during startup, or measure steam quality before entry—the throttle/trip valve’s job is to regulate flow and provide a rapid trip when needed.