I would like to consult about the issues related to the turbine starting oil and emergency shutdown oil

The starting oil pushes the piston to the left against the piston disk, and then the quick-shut oil pushes the piston disk along with the piston to the right to open the quick-shut valve. Then why doesn’t it work to use quick-shut oil to push the piston disc directly to the left?

Is starting oil necessary? 1. Concept and function: The starting oil is sent to the right end of the piston; under the action of oil pressure, the piston is pressed against the piston disk, bringing the sealing surfaces of the piston and the piston disk into contact. This allows the quick-shut valve to open when quick-shut oil is supplied to it. In other words, if start-up oil is not introduced first and direct application of shut-off oil is used, the shut-off valve cannot be opened, as the piston disk does not make contact with the piston cylinder; therefore, applying shut-off oil at this point will not cause the shut-off valve to operate. 2. Significance of the design: Simply put, to enable the operation of the quick-shut valve, it is entirely unnecessary to design a starting oil system; instead, the valve can be designed such that the flow of quick-shut oil opens it, while the pressure-relief valve for that oil closes it. This simplifies the design and also reduces the failure rate. However, assuming a design without a start-up oil step, in extreme situations where the quick-shut oil is suddenly released, causing the unit to stop, and if that quick-shut oil is suddenly restored again, the quick-shut valve will open once more, allowing the unit to restart. This causes significant damage to the unit and results in a loss of the necessary protection. The design featuring starting oil ensures that once the quick-shut valve is closed, it must be restarted manually by creating starting oil, thereby enhancing safety.

How does this device without starting oil generate the quick-shut oil? The start-up oil serves not only to operate the quick-shut valve but also to engage the circuit breaker; without engaging it, the hydraulic fluid at the pump’s outlet will not flow, and it’s thus impossible to create the pressure needed for quick shutdown.

Without starting oil, it is impossible to generate quick-shut oil. In other words, when there is no oil pressure activated, it’s as if the quick-shut oil goes directly into the return oil line.

Only the quick-shut valves of Hangqi units, Siemens units, and Simens Sipron units have the concepts and terms of starting oil and quick-shut oil; such a design is intended primarily for rapid shutdown. It is called start-up oil because, during startup, the spring needs to be pre-compressed first; in this way, when the oil pressure drops, the valve closes and the machine stops operating immediately.

I have a post here with an animated explanation; it’s easy to understand at a glance!

Inside the quick-close valve, there is a component called a piston disk. This piston disk is connected to a piston rod, which in turn carries the valve head of the quick-close valve. There is a spring on one side of the piston disk, with starting oil and quick-close oil present on each side respectively. Before the quick-close valve opens, the starting oil fills the side of the piston disk that has the spring, thereby sealing the radial gap between the piston disk and the cylinder. Once the quick-close oil fills the side of the piston disk that has the piston rod, both sides of the piston disk are filled with oil at equal pressure. When the pressure release valve for the starting oil opens, the pressure on the side with the starting oil decreases. Since the starting oil seals the radial gap around the piston disk, the quick-close oil does not leak to the side with the spring. As a result, the pressure on the spring side decreases, while the high pressure of the quick-close oil on the piston rod side overcomes the force of the spring, causing the piston disk to move from the direction of the piston rod toward the direction of the spring, thus opening the quick-close valve. Its starting oil primarily serves to seal the radial gaps between the piston disc and the cylinder. Without this starting oil for sealing, the quick-shut oil will leak out through those gaps toward the piston disc springs; as a result, the piston disc will not move toward the springs, and the quick-shut valve will not be able to open.