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Why Do Petrol Bowsers Dispense Fuel Full of Air Bubbles?

03/31/2010 5:08 PM

G'day Yall,

Why do Petrol Bowsers dispense fuel full of air bubbles?

I pose this question because I've noticed this "phenomenon" over a few years now. It usually rears its head as an issue when I'm trying to fill, one or other of my 7 series Volvo's. As when the tanks are 3/4 full, they start to "reflux" the fuel. Unless I slow the fill rate considerably, until the fuel in the tanks settle out the "air". It extends the time filling the car's tanks greatly.

By comparison I could fill the fuel tanks using Jerry cans and a funnel in half of the time. Discounting filling the Jerry cans in the first place of course.

I was hoping someone who makes or repairs the bowsers might enlighten me (us).

As a side issue, I find other cars too have filling issues as well not just my 7 series Volvo's but they're the ones that I own. The sedan has a 2 tank setup for a capacity of 85 litres, the wagon has 1 tank at 65 litres.

Cheers

Perry

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Guru

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#1

Re: Why do Petrol Bowsers Dispense Fuel Full of Air Bubbles?

03/31/2010 6:18 PM

This is a gas pump here in the USA.

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#5
In reply to #1

Re: Why do Petrol Bowsers Dispense Fuel Full of Air Bubbles?

04/02/2010 4:26 AM

ha ha, GA!

I would reward you with a GA but I use Safari and the GA button doesn't show on here for some reason.

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Guru

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#2

Re: Why do Petrol Bowsers Dispense Fuel Full of Air Bubbles?

03/31/2010 6:48 PM

Yep we used to have those bowsers, and they didn't pump bubbles. You could see the "quality" of the fuel in the sight glass as you were pumping the fuel into your tank. If there were bubbles you knew the underground tank was really low, and you were pumping crap into your cars tank.

There are probably one or two of these hiding in the odd country service station. Haven't seen one (operating) on a suburban forecourt in over ten years.

As automated self serve stations took over, and then with fuel becoming(in Oz) 130.9cpl retail in price, the old bowsers got retired.

That bowser is in real nice condition, is that part of your collection of automobilia?

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#3
In reply to #2

Re: Why do Petrol Bowsers Dispense Fuel Full of Air Bubbles?

03/31/2010 9:20 PM

No, sorry.

It's not mine.


AutoSpeed - Restoring a Petrol Bowser

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Guru

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#4
In reply to #3

Re: Why do Petrol Bowsers Dispense Fuel Full of Air Bubbles?

03/31/2010 9:59 PM

All good, Thanks for the great link.

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#6

Re: Why Do Petrol Bowsers Dispense Fuel Full of Air Bubbles?

04/02/2010 6:16 AM

Why do Petrol Bowsers dispense fuel full of air bubbles?

It's so y'all can call it 'GAS' of course.

Jim

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Associate

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Location: Minnesota, USA
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#7

Re: Why Do Petrol Bowsers Dispense Fuel Full of Air Bubbles?

04/02/2010 9:47 AM

I noticed it just this morning trying to put gas in my truck. I have noticed it more and more especially lately.

I think it is some moron's idea of trying to make oxygenated fuel. If it works for fish maybe it will work for vehicles.

It seems to me that more bubbles means less gas in the same volume. Meaning less product and more air delivered for the money? Maybe the pump in the underground tank is running slower than the pump in the bowser and thus the bowser is putting more air into the fuel as it moves from the pump to the vehicle?

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#8

Re: Why Do Petrol Bowsers Dispense Fuel Full of Air Bubbles?

04/02/2010 10:33 AM

Depending where the bubbles are introducced to the liquid stream, sounds like you are getting short changed on your "delivered" volume of fuel. Try and pump a measured (imperial ?) gallon by the indicator on the pump, and measure the actual volume of fuel delivered.

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Commentator

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#13
In reply to #8

Re: Why Do Petrol Bowsers Dispense Fuel Full of Air Bubbles?

04/03/2010 7:31 AM

Cardio07,

In the USA, pumps are certified usually, annually by State licensed inspectors. One would assume that a transfer standard prover meter is attached and fuel delivery measured. The result should agree with that of the charge meter to gain (re)approval. I know that some dispensers use Neptune brand positive displacement (nutating disc) meters which should be temperature compensated, but not air bubble proof. The meter is pressurized at pump discharge pressure minus any flow and elevation losses. The bubbles, fuel vapor not air, should form where the nozzle valve pressure drop to atmospheric pressure occurs. Our EPA now requires a vapor recovery system to reduce environmental pollution. If there are more vapor bubbles, I would look at seasonal changes in fuel vapor pressures or the delivery temperature. A cheating vendor would have to inject air before the PD meter only when the "Unknown" inspector was NOT present.

Luther M

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#14
In reply to #13

Re: Why Do Petrol Bowsers Dispense Fuel Full of Air Bubbles?

04/05/2010 9:30 AM

Makes sense. I knew they were certified, but didn't know how. It is a nuisance since I can never seem to fill the tank on my truck without the nozzle clicking off 3-4 times in the first 10 gallons.

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#9

Re: Why Do Petrol Bowsers Dispense Fuel Full of Air Bubbles?

04/02/2010 11:21 AM

The bubbles are intentional and are designed to put a 'head" an your tank and filler neck when full. This plugs the suction tube and shuts off the nozzle. The foam on top of the fluid in the filler neck prevents you from getting your pants wet if it was liquid.

PS the fuel is measured before it reaches the nozzle so you get what you pay for.

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Anonymous Poster
#10
In reply to #9

Re: Why Do Petrol Bowsers Dispense Fuel Full of Air Bubbles?

04/02/2010 11:56 AM

Works too well then.
Is it my imagination or are station wagons the worst affected?

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#15
In reply to #9

Re: Why Do Petrol Bowsers Dispense Fuel Full of Air Bubbles?

04/07/2010 9:48 PM

Do you have details of this process?

How and where are these bubbles produced?

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#11

Re: Why Do Petrol Bowsers Dispense Fuel Full of Air Bubbles?

04/02/2010 5:59 PM

When the bubbles are in the fuel when coming out of the nozzle, they create a bubbling profit effect, since your gas is pumped with volumetric pumps.

the kind of profit like water in ham. Bubbles are cheaper than the actual liquid and sold @ the price of the liquid. but..

DONT WORRY, BE HAPPY: This is against the law and your bubbles are normally not in there when filling up.

When you put your nozzle in the tank pipe there is some difference in diameter. Once the gas flows out of the nozzle, it has a suction effect near it and mixes air from outside your car in it. This mixture creates foam, that disappear after a while.

Alcohol reduces this dramatically. (the foam) The rubber on some nozzles, that you can put against your filling opening is made to reduce this effect, not to not let you not see when it is full. The foam crawls up into your filling pipe and the pressure device cuts off the supply.

I hope this is a good expanation, well I believe in it.

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#12

Re: Why Do Petrol Bowsers Dispense Fuel Full of Air Bubbles?

04/02/2010 7:08 PM

I'm one of those folk, who actually likes to top the tank off. The thing is that when I'm filling my 740 sedan with the twin fuel tanks, At the point of transition between filling the bottom tank and the top tank. I get a reflux of fuel back up the filler neck.

Bottom tank is 65litres, top tank is 20litres, I get a range of 850km from it.

My wagon has only a 65litre tank, I get 600k range as the twin cam is a tad thirsty..LOL.

As part of the change over to Unleaded from Leaded fuel, all Australian delivered cars from 1986 had a restrictor plate fitted with a little spring loaded plate. This was to stop people "accidentally" filling Unleaded cars with Leaded fuel.

I've removed the flap on both cars to facilitated filling, mostly because of the foaming preventing me from filling the tanks properly.

If the reason for the foaming is to produce additional back pressure in the tank when filling it, then somebody deserves a wire brush enema for thinking that was a benefit.

I've had other cars where if I'd stopped filling at the first click off, I'd only have 1/2 filled the tank (My F350, AU Falcon, VYII Commodore).

Thanks for your responses and suppositions.

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