How Does a Petrol Pump Know When to Stop? | 3D Explained

You’re holding the trigger—and suddenly the petrol nozzle clicks off. How does it know when to stop? Go inside an automatic fuel nozzle with ProcessLens. This 3D cutaway follows fuel through the main valve and Venturi, air through a tiny sensing port, and the mechanical linkage that shuts off the flow. Watch how rising fuel covers the sensing hole, increases the vacuum, moves a diaphragm and releases the trigger’s support—allowing a spring to close the valve. CHAPTERS 00:00 How does the nozzle know? 00:12 Follow the fuel 00:26 The Venturi creates suction 00:39 The tiny sensing passage 00:55 Fuel covers the sensing port 01:10 Pressure moves the diaphragm 01:26 The latch releases 01:41 The spring closes the valve 01:58 Why it can click off early 02:15 Flow, sense, release, stop This animation shows a representative Venturi-operated automatic nozzle. Geometry, linkage motion and flow effects are simplified for explanation. Actual nozzle designs vary. The sensing port detects local conditions near the spout; it does not measure the tank’s capacity. Subscribe to ProcessLens for 3D engineering animations revealing the hidden mechanisms inside everyday objects. #HowItWorks #PetrolPump #ProcessLens