Problems with the turbine emergency shutdown valve
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I used to not understand how the quick-shut valve operates. I just looked up information on forums and saw that most users explained that first, a starting oil is created to allow the piston and piston disk to come into contact and form a single unit; then, a quick-shut oil is introduced to push this combined unit to the left. After that, the starting oil is removed, and the quick-shut valve opens. I was wondering if it’s possible to directly create a starting oil supply, and then, even after removing that starting oil, the quick-close valve can still be opened? It doesn’t really matter whether to install a quick-shut off valve or not, right? Mainly, the veteran employees who used to drive the vehicles did it this way on site, and no quick-shut oil pressure was established. . . .
Without a quick-shut oil supply, the quick-shut valve is pressed against its seat by a spring – how can it be opened?
Whether it is a shutdown due to interlock, or the emergency cut-off switch being activated on-site, or the main control panel’s emergency stop button being pressed to shut down the system, in fact, the quick-shut oil valve remains open unless someone manually closes it. The reason for the oil supply to be activated is simply that the quick-shut oil valve is already open; next time you operate the system, just pay close attention to the local instrument panel and you’ll understand.
You must have seen this diagram before; take a close look and think about it. The structure marked with red lines can be understood as a cup lid and a cup (with a small hole in the cup, at the location indicated by the red circle). The starting oil enters through port F, pushing the cup to move to the left so that the cup and its lid become one unit. The quick-shut oil enters through port E, pushing the cup with the lid to move left until it touches the right wall (at this point the starting oil is no longer needed and can be released to relieve pressure), and the quick-shut valve opens. If no starting oil is provided, the cup and the lid remain separated due to the spring inside the cup; the quick-shut oil enters through port E, flows into the cup between the lid and the cup mouth, and then leaks out through the hole marked with a red circle back into the return oil line. Therefore, without starting oil to keep the lid and the cup together, there is no pressure in the quick-shut oil. Regarding what you mentioned about the old employees not using start-up oil, I guess your previous quick-shut valves were of the older type, which did not have a structure where the cover and the container were separate, nor any leakage holes in the container. In the previous design, when the quick-shut valve was closed, it was difficult for the oil in the valve chamber to lose pressure instantly, which resulted in the quick-shut oil acting as a damping force that hindered the closing of the valve due to the spring force. In the new design, when the pressure of the quick-shut oil drops, the spring pushes open the cover and the container, allowing the oil in the valve chamber to flow back into the tank instantly through the leakage ports, thereby enabling a faster shut-off. Look at it in terms of the system processes and structure.
Without quick-shut oil, it is not possible to operate the quick-shut valve; please refer to the illustration provided by the expert on floor 4