Regarding the steam pressure relief valve Y43H
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Today I disassembled a steam pressure relief valve of model Y43H. I had looked up a lot of information beforehand; it’s a pilot-operated type, and its working principle is easy to understand. What confuses me is that, as shown in the diagram, it seems to me that both the pilot steam port and the feedback port are located in the same passage – whereas they should be separated from each other, right? I don’t understand; please help me. I’ve been thinking about it all day but still can’t figure it out
But when I took it apart, there were no gaskets; could it be that gaskets should have been there originally? But if gaskets are to be used, why design it so complicated? A simple flat surface would do just fine
The pilot orifice uses the pressure generated by a small amount of gas to act on the larger surface area of the main valve body. (Ring-shaped air chamber)
I know that; the pressure of the pilot gas pushes the main piston downward, thereby opening the main valve. What I don’t understand is why, as shown in the diagram, the pilot hole and the feedback control hole are located in the same tunnel; in that case, when the pilot gas arrives, doesn’t it flow through the feedback hole and go downstream? How can pressure be created then?
Thank you all for your replies. I’ve found the reason: I took apart another large-pressure-reducing valve of the same model, and indeed there is a gasket there that serves to provide sealing; moreover, the piston sleeve is movable, and its end face is flat, matching the end faces of the pilot hole and the feedback hole. With the pressure relief valve that was removed earlier, firstly, I didn’t see any gasket when removing it; secondly, the end face of the piston sleeve was higher than those of the pilot hole and feedback hole, and it couldn’t move (it might have been rusted in place, which I didn’t notice). So I couldn’t figure it out – if there had been a gasket in that area, everything would have made sense.