Regarding the crisis cut-off switch for steam turbines
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Everyone, I am currently learning about the emergency cut-off valves in steam turbines. When it is necessary to reset such valves, one method involves using reset oil to overcome the spring force and create a pressure that enables rapid shutdown; another method is to pull the handle directly, also with the aim of overcoming the spring force. My question is: why, when pressure oil is applied directly, it isn’t enough to lift the spool and overcome the spring force? Why is reset oil needed to help overcome it? Normally, isn’t it the pressure oil that creates the quick-shut oil circuit? Then why is extra force required for resetting?
It cannot be set to auto-reply to ensure safety
On-site manual reset is intended for further inspection and confirmation.
Those with reset oil can reset automatically; this is the principle of operation of the spool valve
My point is that even if a reset oil is used for resetting, it is removed after the reset; in the end, isn’t it still the pressure oil itself that overcomes the spring force? In other words, the pressure oil is sufficient to overcome the spring force, so why is it necessary to rely on the power of the reset oil during the reset process? Is there some other internal structure that I haven’t noticed? Please advise
Before reset, the pressure oil inside the emergency safety device is connected to the return oil, so it is not possible to reset it using hydraulic pressure.
Wasn’t the quick-shut oil connected to the circuit before it was reset? Is the pressure oil also connected?