Fuel container

[skippydiesel]

16 minutes ago, kgwilson said:

The red Proquip I have will hold 24 litres of 98 ULP filled right to the base of the filler neck.

As I put a pump into mine - filling to the very top/neck results in spillage.

[onetrack]

It's not a good idea to overfill petrol containers beyond their stated capacity, as some airspace is needed to counter fuel expansion and contraction with major ambient temperature changes.

[kgwilson]

I don't store PULP. It ghoes straight in to the aircraft when I get back from the Servo. Fresh is always best.

[skippydiesel]

12 minutes ago, onetrack said:

It's not a good idea to overfill petrol containers beyond their stated capacity, as some airspace is needed to counter fuel expansion and contraction with major ambient temperature changes.

This is certainly conventional wisdom BUT somehow doesn't make sense to me (perhaps the more scientific members of the Forum will give their thoughts).

 

The pressure, the evaporating fuel will exert, to a sealed container will surely be the same, no matter the size of the airspace (or lack of).  

 

My observations are that :

• In hot weather, a residue of fuel (within the "proper red" container" ) will bulge the sides of the container, just as much as a partially full or 100% full. 
• In cold weather (below that the container was last opened to atmosphere) a residue or partially filled container will "hollow out" while the 100% full just returns to "normal" resting shape/dimensions.

I suspect this wisdom applies more to containers open to atmosphere - fill beyond the recommended level, risks expansion beyond the reserve volume (air space) and fuel spillage.

[old man emu]

It's probably trifling, but isn't it important to know how much fuel you actually put into a tank, especially if you are not going "full tanks". Four litres is only a tad under 3 kgs, by every gram counts.

 

By the way, if you need to refuel at The Event, I will have a ladder, earthing straps, grounding rod and a Mister Funnel available. You supply the grunt to lift the fuel container.

[kgwilson]

In my experience a partially full container will expand far more than one that is full when the temperature increases. The presence of air in the container allows for evaporation of the lighter aromatics and unless the container is vented pressure will build up and in the case of plastic containers, then the container itself will bulge. If the container is full the fuel will only expand based on the temperature as evaporation is prevented.

[old man emu]

 

This is an extreme version

53 minutes ago, onetrack said:

It's not a good idea to overfill petrol containers beyond their stated capacity, as some airspace is needed to counter fuel expansion and contraction with major ambient temperature changes.

Skippy, Onetrack is talking about vapour pressure the pressure of the vapor resulting from evaporation of a liquid (or solid) above a sample of the liquid. What KGWilson  indicates is that the greater the space above the surface ofthe liquid, the more that can evaporate from the liquid and squeeze between the usual molecules making up fresh air. So, it you restrict that free-air volume, you will restrict the degree of vapour pressure heating will allow.

 

This video is not quite an example of vapour pressure, but sort of explains it.

 

 

[facthunter]

Near empty volatile liquid containers will collapse with a tight lid on a cold night. With only a small airspace that cannot happen.   Nev

[skippydiesel]

48 minutes ago, kgwilson said:

In my experience a partially full container will expand far more than one that is full when the temperature increases. The presence of air in the container allows for evaporation of the lighter aromatics and unless the container is vented pressure will build up and in the case of plastic containers, then the container itself will bulge. If the container is full the fuel will only expand based on the temperature as evaporation is prevented.

Its unusual for a fuel container to be filled, so as to have no airspace at all - even a small air space will allow for some fuel to vaporise. Agreed if this is very small the effect (even with the same pressure) will not bulge the container (much)

[onetrack]

Vapour compresses a lot more easily than a liquid, so all the recommendations from agencies with authority, are not to overfill fuel containers, to allow for liquid expansion.

 

The U.S. Army handles more petrol than anyone else in the world, so I guess they know what they're talking about.

 

https://www.army.mil/article/246291/respect_the_dangers_of_gasoline_protect_you_and_your_family

[skippydiesel]

OME - thank you for the Sumner-Millar video - Hookes Law applies however its effects are not usually so marked, in Australian ambient condition and with plastic fuel containers, that usually return to their origional shape/dimensions, when diurnal  temperature rise.

 

Me thinks you are sort of supporting, in the main, my less scientific observations.

[facthunter]

You have  several factors here. Vapour pressure and thermal expansion of the liquid (which is incompressible) OR freezing expansion with water. The first one I have seen make steel contains collapse. I've never seen one split due positive pressure.  The ice water thing splits large rocks in nature and makes Icebergs float.. Water is unique in expanding as it freezes. It will crack open the strongest of engine blocks.  Nev

[old man emu]

I was going to go into the effect of the pressure the liquid exerts on the wall of the container due to  the weight of the liquid itself, and how that pressure interacts with the atmospheric pressure from the outside. But then you'd have to take into account the resistance of the material of the container itself to deformation. 

 

Who started this journey down a rabbit hole?

[facthunter]

The pressure you speak of there is of a very low order.   Nev

[Old Koreelah]

8 hours ago, facthunter said:

Near empty volatile liquid containers will collapse with a tight lid on a cold night. With only a small airspace that cannot happen.   Nev

I have a couple of old sealed 44s next to my shed that go bang at predictable times of the day and night.

[spacesailor]

I have just vented my 44 G  drum to get cold air in before the winter chill,s make it buckle .

Long ago ( working life ) I filled a drum with steam , then capped it in the morning it had collapsed to a quarter of it,s width . it looked weird.

spacesailor

[spacesailor]

Footnote to above !

" and capped it  .  In the morning " .

Were did my full stop go !, just vanished.  LoL

spacesailor

[facthunter]

We did science experiments like that. 14.7 lbs / sq inch  adds up to a bit of force.. Nev

[old man emu]

33 minutes ago, facthunter said:

14.7 lbs / sq inch

 

Or close enough to one kilogram per square centimetre. 

[spacesailor]

Mine Was only 29 inch mercury . The steam temp Was " superheated "   about 170 C .

Hot 

spacesailor

[Carbon Canary]

I recall having to put the butane canister inside my sleeping bag while camping in Kosciusko NP in winter, otherwise the flame was barely a flicker in the morning.

 

 Clapeyron equation for calculating vapour pressure....or 'clap your eyes on' equation as it was colloquially known back when I was young and foolish,...... but anyhow, I've since forgotten more than I ever learnt.

[old man emu]

I'm glad that we use the Metric system in aviation for air pressure. Using hectoPascals for QNH and QNE provides for better accuracy simply by there being more divisions on a hPa scale than on an inch scale.

[facthunter]

STD sea level 29.92 inches of mercury 1013. 2 millibars or 760 mm of mercury=1 Bar 14.7 lbs/sq Inch pressure. I didn't know the 760 MM thing and have never used it  Nev

[Carbon Canary]

Yep- gotta love the use of the metric system at least in GA........

 

Runway distance in metres,

altitude in feet

horizontal separation in metres, but vertical separation in feet

Oil in the engine in quarts (Lycoming)

Fuel in the tanks in litres

Speed in knots

air pressure in Hpa

Tyre pressure in psi

 

Glad we've got that all sorted.  Good thing I'm bilingual.

 

I flew a LSA in Germany last year and the ASI was in km/h.  It was quite disconcerting to approach a grass strip at "100" ! 

[kgwilson]

It is about time everything changed to metric. The only thing that makes sense is speed in knots as it relates to degrees of latitude & even then with decimal degree settings and electronic everything now it doesn't matter. Why is altitude in feet? It is in metres in Europe. I assume it is due to the original dominance of American & British aviation. Even oil comes in quarts from Aeroshell. Shell is European (Dutch) so you'd expect litres. Again the only reason i can think of is the dominance of the US GA industry, though it probably comes in litres in Europe.