Governor speed-control valves

It is really just like cruise control on your car. You select the speed you want to drive at. If the car is going slower than the speed you selected, or set speed, the gas pedal is depressed, to bring the car up to your selected set speed. The governor speed-control valve is just like the gas pedal. 

The high-velocity steam strikes the buckets around the rim of the turbine wheel shown in Fig. 17.1. Actually, these so-called buckets resemble blades or vanes. I imagine the term bucket is a carryover from the days of the water wheel. The velocity of the steam is now transferred to the spinning turbine wheel. If the turbine is running below its set speed, the speed controller causes the governor speed-control valve to open. 

What I wish to achieve is to maintain the same horsepower output from the turbine. But at the same time, I want to force open the governor speed-control valve, raise the pressure in the steam chest, but decrease the steam flow through the steam nozzle. The only way this can be done is to make the nozzle smaller. 

The net effect of this exercise will be to save not 20 percent of the motive steam, but 10 percent. The 20 percent reduction in nozzle area is partially offset by the opening of the governor valve. The inefficient, irreversible, isoenthalpic expansion and pressure drop across the governor speed control valve are reduced. The efficient, reversible, isoen-tropic expansion and pressure drop across the nozzles are increased. 

Our overall objective is to wind up with both the process-control valve downstream of the pump and the governor speed-control valve in a mostly wide-open, but still controllable, position. To achieve this dual objective, we have to simultaneously ... 

Ladies and gentlemen, it is not a good idea to run a turbine with the governor speed-control valve wide open. Why Because you no longer have any speed control. And the turbine speed is then free to wander. The rest of this story is pure philosophy. 

During the evening, my operators decided to increase the combustion airflow from the blower or air compressor. This is done by opening the suction valve to the blower. Naturally, it requires more work to compress more air. But the turbine could not produce any more work or horsepower because the steam turbine s governor speed-control valve was already 100 percent open ... 

A turbine-driven pump is said to be driver-limited when the governor speed-control valve is wide open. This speed-control valve, is usually called the Woodward governor. It is not that easy to see if the governor is really wide open. A few simple methods to make this determination are... 

Governor speed-control valve Controls a turbine s sp>eed automatically by... 

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