boiling gas

bicycler44

New User
Have a 1951 8n. After running it for awhile the gas
In the tank begins to bubble like it is boiling.
What could be causing this and is there danger of
An explosion?
 
" What could be causing this"

Ethanol boils at a lower temp than gasoline.

" is there danger of An explosion? "

Only if you take the cap off and get the gas near a spark.
75 Tips
 
"What could be causing this...."

Federal regulations.

Usually it is not a serious issue so long as the tank is properly vented, not filled near the top, and you do not remove the cap when it is pressurized.

Dean
 
Is there any chance that the gas you have in the tank is winter blend gas? Winter blend gas has a lower evaporation point than summer blend. I have had winter blend gas boil in the tank of my 8N when used on a hot summer day. I have never had summer blend gas boil regardless of the temperature.
 
Gasoline is blended to a vapor pressure specification. The vapor pressure is important since it insures the gasoline will evaporate in the engine; liquid gasoline does not burn, only vapor. In winter months the gasoline is blended for a higher vapor pressure than for the summer months. This is important and aids starting in cold weather.

Since the 8N gas tank is above and heated by the engine it is common to observe "boiling" gas. This condition is more likely to occur if winter gasoline is not consumed and remains in the tank into the hotter summer months. The higher the vapor pressure of gasoline, the lower the temperature at which it begins to boil.

It is common to hear the boiling blamed on ethanol blended in the gasoline. This is incorrect since the boiling point of ethanol is 172 degrees F. Gasoline has a range of boiling points with the lighter components beginning to boil at temperatures below 100 degrees F and the heavier components requiring temperatures of 400 degrees F and above.

In cars etc. the gas tank is located under the vehicle and picks up heat from the muffler and hot road surfaces in summer weather. If you could see into the tank (like you can on an 8N) you sould observe the same "boiling" under the right conditions, for example; hot day, stop/go traffic, etc.
 
(quoted from post at 09:19:24 08/05/14)
It is common to hear the boiling blamed on ethanol blended in the gasoline. This is incorrect since the boiling point of ethanol is 172 degrees F. Gasoline has a range of boiling points with the lighter components beginning to boil at temperatures below 100 degrees F and the heavier components requiring temperatures of 400 degrees F and above.

JMOR even risked his eyebrows demonstrating that. IIRC he observed a very perceptible boiling action at 130F - a full 40F under the boiling point of ethanol.

TOH

PS> Professional experimenter with Nomex fire suit. Don't try this at home kids :roll:

BoilingGasoline2.jpg
 
" with the lighter components beginning to boil at temperatures below 100 degrees F "

Isn't that called evaporation?

As was explained to me........

Ethanol boils at 172* F. Period.

Gasoline, however, will not really "boil" until around 200*.

So it's just a coincidence that frequent reports of gas boiling in N tanks has only been a recent (past 15 years or so) phenomena?
75 Tips
 
(quoted from post at 10:03:49 08/05/14) " with the lighter components beginning to boil at temperatures below 100 degrees F "

Isn't that called evaporation?

As was explained to me........

Ethanol boils at 172* F. Period.

Gasoline, however, will not really "boil" until around 200*.

So it's just a coincidence that frequent reports of gas boiling in N tanks has only been a recent (past 15 years or so) phenomena?
75 Tips

The "boiling point" of a liquid is the temperature at which it changes state from liquid to gas. Gasoline is a mixture of many different liquids and they boil at different temperatures.

In casual use, when we talk about a mixture boiling we are generally describing the state where visible gas bubbles are forming in the liquid and rising to the surface where the burst. That is not evaporation. Evaporation is a surface phenomenon where the molecules at the surface layer of a liquid reach the "boiling" temperature and change state to a gas. The gas molecules quickly coalesce into a partially saturated vapor - part liquid part gas. Only a very small percentage of the surface layer molecules do that at any given time and it is not generally detectable to the naked eye.

A moonshiner will tell you that ethanol "boils" at roughly 172F and water boils at roughly 212F. Consequently he can extract "pure" ethanol from a vat of fermented corn mash at temperatures right around 175F leaving the water and other byproducts behind. The ethanol gas is then passed through a condenser where it is cooled and turns back into "pure" liquid alcohol. That is "distillation". :D

As JMOR demonstrated you can produce visible "boiling" behavior in pump gasoline at temperatures well below the boiling point of ethanol (172F). In fact, if you look it up the boiling point of "gasoline" it is generally stated to be in the range of 100 to 400F. That doesn't mean different "gasolines" have different boiling points. It means the constituent parts of ANY gasoline blend have widely different boiling points. The individual components used to blend gasoline are refined from crude into their "pure" forms primarily through fractional distillation. After blending them into a new liquid mixture called "gasoline" you can extract them again using their boiling points and the process of distillation in just the same way a moonshiner makes "white lightning".

According to this 1999 publication (data from Shell) about 30% by weight of the hydrocarbons in unleaded pump gasoline have boiling points at or below 60C (140F). (nb. for some reason the YT bbcode software doesn't like the link but you can cut and paste to get to the document). The blending of pump gasoline has been an evolving science and that percentage may have changed slightly since the 40's but I don't think boiling gasoline in an N-series is a new phenomenon. The topic however has recently become red hot ;-)

http://www.etc-cte.ec.gc.ca/databases/Oilproperties/pdf/WEB_Gasoline_(Unleaded).pdf

TOH :D
 
(quoted from post at 11:53:47 08/05/14)
(quoted from post at 10:03:49 08/05/14) " with the lighter components beginning to boil at temperatures below 100 degrees F "

Isn't that called evaporation?

As was explained to me........

Ethanol boils at 172* F. Period.

Gasoline, however, will not really "boil" until around 200*.

So it's just a coincidence that frequent reports of gas boiling in N tanks has only been a recent (past 15 years or so) phenomena?
75 Tips

The "boiling point" of a liquid is the temperature at which it changes state from liquid to gas. Gasoline is a mixture of many different liquids and they boil at different temperatures.

In casual use, when we talk about a mixture boiling we are generally describing the state where visible gas bubbles are forming in the liquid and rising to the surface where the burst. That is not evaporation. Evaporation is a surface phenomenon where the molecules at the surface layer of a liquid reach the "boiling" temperature and change state to a gas. The gas molecules quickly coalesce into a partially saturated vapor - part liquid part gas. Only a very small percentage of the surface layer molecules do that at any given time and it is not generally detectable to the naked eye.

A moonshiner will tell you that ethanol "boils" at roughly 172F and water boils at roughly 212F. Consequently he can extract "pure" ethanol from a vat of fermented corn mash at temperatures right around 175F leaving the water and other byproducts behind. The ethanol gas is then passed through a condenser where it is cooled and turns back into "pure" liquid alcohol. That is "distillation". :D

As JMOR demonstrated you can produce visible "boiling" behavior in pump gasoline at temperatures well below the boiling point of ethanol (172F). In fact, if you look it up the boiling point of "gasoline" it is generally stated to be in the range of 100 to 400F. That doesn't mean different "gasolines" have different boiling points. It means the constituent parts of ANY gasoline blend have widely different boiling points. The individual components used to blend gasoline are refined from crude into their "pure" forms primarily through fractional distillation. After blending them into a new liquid mixture called "gasoline" you can extract them again using their boiling points and the process of distillation in just the same way a moonshiner makes "white lightning".

According to this 1999 publication (data from Shell) about 30% by weight of the hydrocarbons in unleaded pump gasoline have boiling points at or below 60C (140F). (nb. for some reason the YT bbcode software doesn't like the link but you can cut and paste to get to the document). The blending of pump gasoline has been an evolving science and that percentage may have changed slightly since the 40's but I don't think boiling gasoline in an N-series is a new phenomenon. The topic however has recently become red hot ;-)

http://www.etc-cte.ec.gc.ca/databases/Oilproperties/pdf/WEB_Gasoline_(Unleaded).pdf

TOH :D
hat is a great 'in-a-nut-shell' explanation with good parallels!
 
Good answers from the group. A few things you can do too is get a vented gas cap -there was an exchange program and it should still be in effect. take your old cap in to CNH dealer and he will exchange for the newer vented style. Also, the gas tank has a very small vent hole on top. You have to pull the hood off and drop the tank to get to it. The vent hole is about 1-2 mm in diameter and is on top of the 'dome' that sits on the top. Now, let's get back to making some sour mash...

Tim 'PloughNman' Daley(MI)
 
Bruce,

Sorry for the late reply - I was away from my computer for a few days. I will be brief since I suspect the most excellent post by TheOldHokie may have answered your questions.

Yes, ethanol boils at 172 degrees F and will continue boiling at that temperature until all the liquid has been boiled off.

For gasoline at 200 degrees F the lighter hydrocarbon components will be boiling. If the temperature is maintained, the boiling will stop as these lighter components are boiled off. Since the boiling point of the remaining heavier hyrocarbon components is above 200 degrees F any vapor formation from these liquids would be called evaporation. Therefore, liquid gasoline at 200 degrees F can be both boiling (visible) and evaporating (invisible).

Yes, certainly this has been going on long before it was discussed on this forum.

BTW - I like your 75 tips and refer them from time to time.

Ken
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top