If the high pressure port became plugged in the spring-loaded, internal pilot, self-operated, steam pressure reducing valve illustrated, which of the following problems would probably occur? See illustration GS-0044.
• Flow path from high pressure inlet through passage C to the auxiliary (pilot) valve D and then to the underside of piston H • Role of spring A on the main valve B versus the role of steam pressure under piston H in actually lifting/opening the main valve • Difference between the high pressure supply port and the low-pressure sensing/feedback port J from the outlet
• Trace, step-by-step, how steam gets from the inlet to the space under piston H when the valve is operating normally. What specific passage must be clear for pilot valve D to have any effect? • If that high pressure passage becomes plugged, what force(s) are still available to move piston H and main valve B? Which components lose their ability to influence piston H? • Ask yourself whether a blocked high‑pressure port would tend to make the valve fail wide open or tend to leave the main valve closed/unchanged, and why.
• Identify exactly which port in the drawing is the high pressure port feeding the pilot, and confirm where it leads. • Verify which space above/below piston H is connected to the outlet (low pressure) and which should receive high pressure from the inlet. • Confirm whether opening auxiliary valve D can change the pressure on piston H if there is no high‑pressure flow available through the plugged port.
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