The inlet valve in a Hydro Power station is used as a safety device. The valve is located within the power house on the upstream side. The inlet valve is used for isolating the Hydro-turbine for maintenance purpose also.
The inlet valve is basically a Butterfly valve having a very less head loss. The hydraulic power pack is mounted on the driving end of the valves. The non driving end of the valve trunion is mounted with a dead weight arrangement through a lever. |
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For small & medium turbines where grid power is not available, the valve is opened by a hand pump provided in the power pack. For Large power plants where grid power is available valve is opened with the motorized operation of the power pack. The inlet valve is provided with a by pass arrangement from the upstream side to the downstream sided, a valve provided in the bypass arrangement is opened so that the pressure in the both side of the valve is in equilibrium condition. After this the valve is opened. |
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In the event of the load shedding on the machine the turbine has a tendency to go to run a way speed which may damage the Generation and the parts of the machine. The runaway speed of the machine varies between 120% to 360% depending on the type of turbine i:e Impulse, francis or axial flow turbine. |
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In order to save the machine from this damage the solenoid valve provided in Hydro power pack is energized or de-energized depending upon the scheme which in turn released the hydraulic pressure in the cylinder resulting in closure of the valve in seconds with the help of dead weight arrangement. The solenoid valve of the power pack is interlocked with the generation power. |
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| FLOW CHARACTERISTICS OF BUTTERFLY VALVES |
The flow characteristics through a butterfly valve are generally as per FIG. The flow through the valve can easily be throttled for control purposes as the flow at various angles is percentage of the total flow of the valve in full open condition. |
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REGULATION OF FLOW BY INLET VALVE FOR LOW HEAD MACHINES. |
For low head machines sometimes it is economical to control the flow through the turbine by the inlet valve as per the flow characteristics through the butterfly valves. |
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| In this case the varies, the servomotor mechanism is eliminated reducing the cost of the machines. |
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