🔍 Key Concepts

• Pneumatic flapper-nozzle system operation (what happens at the nozzle when the flapper moves) • Typical functions of the three ports on a pneumatic relay or pilot valve: supply, output, and vent/feedback • How the air path flows from supply, through the nozzle area, and out to the controlled device or atmosphere

💭 Think About

• Trace the air path starting at the supply port, then through the internal passages to the area near the nozzle, and finally to each of the labeled ports G, F, and H. Which one logically must go to atmosphere? • Look at what the moving parts (nozzle disc, blade, extension pin) are trying to control. Are they trying to modulate an output signal, a feedback signal, or simply bleed air to atmosphere? • Compare the internal connection of port F in the drawing with ports G and H. Which one appears to connect directly to the nozzle passage that opens/closes as the blade moves?

✅ Before You Answer

• Identify which port is clearly connected to the air supply line and eliminate that option from consideration for port F. • Determine which passage from the nozzle area must go to atmosphere or low pressure so the device can relieve/bleed air when the flapper moves away from the nozzle. • Confirm whether port F is drawn as sharing a passage with the nozzle/bleed or with a diaphragm chamber that would carry a controlled output or feedback pressure.