How petrol pumps know when to turn themselves off

Gas or petrol pump nozzles turn off automatically when your tank is full. The way it works is really clever and uses the venturi effect.

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[SteveMould]

If I've set things up right, the title of this video should say "gas" for US people, and "petrol" for UK people! If you're in one of those countries, can you confirm?

[donaldasayers]

As a (retired) technology teacher, I can respect the huge investment in time and energy needed to make and test those models. Also your perspex models are getting better as you learn. Good jobs all round.

[iTrialpha]

You can feel the petrol (water) hammer/hydraulic shock when the pump shuts off as the valve closes as well. Always wondered about that, cheers Steve this was really interesting

[frankmayer]

I am fascinated by how much simple technologies are put together inside that thing and how hard it is to explain how they interfere with each other…

[Worlds_okayest_engineer]

I’m a an engineer and I used to work for the company that originally created that design. Actually, I redesigned that ball bearing mechanism. I can confirm that you are correct in your assessment of how it works. Also, most gas nozzles have a second diaphragm or plunger (not membrane) that deflects when there is pressure in the fuel line. It is used for prepay fill up. When you hit the prepay amount the dispenser shuts off, the pressure in the nozzle drops and that second diaphragm which is spring biased up will move and shut the nozzle off. There is a third shutoff in some nozzles that is called an attitude device. When a … moron… pulls a flowing nozzle out of a car’s fill pipe, a ball bearing blocks the pickup tube and shuts the nozzle off.

[gordonmcknight]

I remember looking up how this worked a few years back. The fluid dynamics and drawings went way over my head and I was left confused. Incredibly impressed (but not surprised) that you managed to clearly explain the mechanism to a total lay person in just over ten minutes!

[romanmichaelhamilton]

I was mentored by the two engineers who patented this back in 1965 and worked with them for over three years. They are both gone now, but they gave me a lot of knowledge during that time. One was like a second father to me and he was as detailed and meticulous as one could be. They two men didn't get much out it as like most corporations do, the board takes it all for themselves.

[journeyon]

This is one invention that never seems to fail. It's never failed for me and I'm 66 years old. I've never seen or heard of this valve not working from other people either. That's quite a successful bit of engineering, I'd say.

[DunningKruger]

I had it, then lost it. Had it, lost it again. Then I got it. I love how you keep explaining with different visual examples. Such a great teacher.

[richardstewart]

I have worked as a mechanic and as an electrician for most of my adult life. Part of the fun of these careers is trying to figure out how things work. Most are pretty easy, however, I can remember a few times while pumping gas into my car that I thought about how those nozels worked. I thought a ventury and valve might have been involved, but never was able to tie it all together. Thank you for clearing all that up...Its always nice to see how things work. Well done!

[MrEcted]

This is one of those things I've probably wondered about 100 times while pumping gas, but always forget about by the time I get home so I never looked it up. I'm glad you have finally answered this mini-mystery, and done such in a way that is intuitive and easy to understand!

I always assumed it was probably some sort of electronic sensor, but this is far more clever!

[ernest]

The fact that this is all done mechanically and not electronically is what makes this so cool to me

[RobertoTifi]

I'm so satisfied when there's no electronics involved... Nothing but pure fluid-mechanical principles in action. Ingenious! And you're such a good teacher!

[ftS]

I am no engineer, technician or mechanic, but I have been taking things apart all my life to figure out how they work. Thank you for explaining it all so well.

[NoTimeLeft_]

The fact that you made a see-through, 2D version makes me unbelievably happy! Well done good sir

[wojtekpolska]

You have a great style of making these videos.
1 - You really struck gold with these 2D models, they show everything so nicely and without clutter
2 - You explain things in multiple different ways, which is helpful when someone doesn't get it the first time, and then would be confused for the rest of the video

So thanks for showing off clever designs and physic principles in this way :D

[beppebergmanable]

My parents ran a gas station and I helped them since I was a child. Your explaination helped me understand a phenomenon I experienced many times in my first twenty years of life! Very ingenious, hope someone was rewarded for this mechanism. Nice video and very good explaination, thanks!

[kayderl]

I respect the tremendous amount of time and effort you put in to the making of visual tools that you use to explain. There were at least 2 glass tubes, that green and red pipe stuff, the sawn in half nozzle, that mock up of the sawn in half nozzle and possibly more. Yet somehow, all I could do was to like, sub and share your video to my social media. I few that what I do isn't proportional to the amount of work you put in to this video and that is why I have mad respect for you. I thought I was a huge nerd, but I think I found a bigger one in you.

[abrievanwyk]

I don't usually comment on videos, but this deserves appreciation... Thanks Steve! That green and red model was amazing! To remove complexity with simple models is an extremely difficult thing to do and you nailed it here! Thanks again!

[andrewshipp]

I'm a mechanic by trade. Can't say I've ever known how these work. As soon as you started on Venturis it all clicked for me, seeing carburettors work using the same principal. It's all clear now thanks to your great explanation. Thank you!