Issues with the oil circuit of the emergency cut-off valve in the turbine protection system?
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When the start-up oil is established, the emergency throttle cut-off mechanism causes automatic gear shifting; the control oil port is connected to the rapid shutdown oil port – what is the purpose of the return line at the outlet? Please explain!
At startup, a switch (start) is first established; once the hydraulic pressure for starting is released, the pressure in this pipeline keeps the valve in the downward position, ensuring connectivity between the control oil and the quick-shut oil. When the unit speeds up, the flyweight activates; together with the force of the spring, this causes the valve to move upward, blocking the control oil passage. As a result, the rapid shutdown hydraulic pressure is relieved, the rapid shutdown valve closes, and the steam supply to the unit is cut off.
At startup, a switch (start) is first established; once the hydraulic pressure for starting is released, the pressure in this pipeline keeps the valve in the downward position, ensuring connectivity between the control oil and the quick-shut oil. When the unit speeds up, the flyweight activates; together with the force of the spring, this causes the valve to move upward, blocking the control oil passage. As a result, the rapid shutdown hydraulic pressure is relieved, the rapid shutdown valve closes, and the steam supply to the unit is cut off.