Talking Thermodynamics

[MJM460]

Hi Willy, I like the general direction of your questions.  (Like vectors they have direction as well as difficulty).  Direction being away from vectors and all that maths!

Intumescent coatings.  Like Admiral DK, I find myself reminded of things that I had forgotten that I once knew.  I have been deep into compressors and the like for so long, I had forgotten all about that stuff.

We used to use intumescent coatings back in the 70's.  It is a fireproofing coating used to provide a degree of protection from extreme heat.  Not a real long term answer, and no where near as good as concrete and other materials applied over steel to increase the time before the steel starts melting, leading to structures collapsing.

Concrete is heavy and not very practical for things that have to be opened such as metal cable trays in overhead pipe racks.  The intumescent coating is more like a thick tarry paint, but when exposed to fire, it reacts and expands to make a short term fire barrier. 

You would not use it instead of concrete, but even quite a small fire can melt a hundred cables in a steel cable tray.  It takes minutes to extinguish the fire and a week or more to get all the cables reconnected and working.  A relatively minor event shuts down half the plant, though a fire in a hydrocarbon processing plant is never considered a minor event.

A layer of that coating is not much heavier than thick paint if you need to get into the cable tray, but if it gives you 20 - 30 minutes before the cables melt, it could be well worthwhile.  I really don't know how well it worked, or if it is still in use.  Sometimes those things seem like a good idea, but turn out to have unanticipated disadvantages.  I also don't know what the compound actually is, but I assume it is something that reacts or breaks down on exposure to heat to make some gas which expands the product to improve its insulating value.

Some one else may be able to come in with more information on how well it works in an actual fire.

Another small topic which I have been intending to return to, is lubrication of steam engines, and the appropriate oil.  My engines are normally run on steam, and I include a displacement lubricator with each.  We have probably all heard or seen the oil company add which starts off with "Oils ain't oils...."  Unfortunately it does not do much to inform us about why their oil might be superior to the opposition's identical product, let alone why we might choose one type of oil over another, even within their own range.  And I always remember one major oil company that threw out my carefully prepared schedule of recommended lubricants (all of their manufacture) for the various equipment items in the plant we were just completing, insisting that it was too expensive to keep all those oils, they were only going to use one, the one they always use, and handled in bulk containers.  I wonder what they told their customers to buy?

However, I started out using standard light engine oil and sometimes machine oil in my lubricators.  Seemed to work ok, in that I had no seizures or other problems attributable to inadequate lubrication.  May not have run long enough for such problems to show up anyway, an oil can might have done the job.  But I started to notice that the liquid I drained from the lubricator, instead of being clear water followed by any remaining oil, was a bit of a grey emulsion.  Furthermore, the emulsion seemed quite stable and did not separate into separate oil and water layers, no matter how long I left it sitting.  It even gummed up the water outlet on the separator, which did not help its efficiency.

Now that emulsion settling and breaking time is an important property to look for in any oil you intend to use.  If you shake up some water with a bit of your oil in a clear container, you want it to separate reasonable quickly.

Running my engines again recently for those recent tests, (not analysed yet by the way) I found the slide valves had stuck, and would not seat to seal when the steam started coming through.  A stop valve probably would have helped by holding the steam in the boiler until there was a bit of pressure and the initial velocity might have had more chance of seating the valve, so I am currently drawing up a stop valve.  But when I took off the steam chest cover, I was greeted by a sticky mess  that took lots of WD40, rags, pipe cleaners etc to remove.  After re-assembly, the engine went as well as ever once again.

I managed to come by some "proper" steam oil, cleaned out my lubricators and used that for the most recent runs.  The first few runs showed quite a change in terms of improved emulsion  separation behaviour, and the last traces of the old oil were gone after a few runs.  Now I drain nearly clear liquid followed by some remaining oil, and the traces of emulsion break quite quickly, leaving nice looking oil floating on clear water.

Ok, now I have to add to my project list more carefully testing those oil behaviours and provide some measurements of times etc.  but for the moment, I am quite happy that the steam oil is definitely an improvement.  After a run, the remainder in the lubricator separates into two distinct layers quickly, and the valve and steam chest appear nicely lubricated instead of gummed up with sticky emulsion.  Clearly different behaviour to normal engine or machine oils.

I don't know much about the additives in different oils, but emulsion breakers are clearly present in the steam oil, perhaps a formulation more suited to the conditions in a steam engine.  Other additives speed air release in systems where there is a lot of turbulence, which leaves the oil full of tiny air bubbles, while others have a detergent action.  So it's worth a little effort to get something suited to your application.

When steam engines are run on air, displacement lubricators don't work, as they rely on condensation of some of the steam to float the oil into the steam line.  There are hydrostatic lubricators which can be used instead, and little pressure pumps.  I would be most interested to hear what people have used and their impressions about the success or otherwise of the systems they have tried.

Thanks for following along,

MJM460

[steam guy willy]

Hi MJM, i do have a can of steam oil...it is called COMPOUND STEEL OIL though ?? it is very gloopy and almost black/green in colour .I have used it with the electrically heated boiler to power different engines and have not noticed any problems with it. It takes a long time to drain and almost doesn't  completely !! Could you find out what the 680  refers to please...

Willy

[Dan Rowe]

Could you find out what the 680  refers to please...

Willy 680 is the ISO grade. 680 is recommended for higher pressures see:
http://www.lsc-online.com/steam-cylinder-oil/

Dan

[MJM460]

Hi Dan, good to hear from you again.  Thanks for coming in with an answer on that.  Do you know if the ISO viscosity grade (vg) is only the viscosity in centistokes at a defined temperature, or are there more conditions or regulations to meet?

In this case, the material data sheet specifies the viscosity as 684 centistokes at 40 deg C, so the 680 looks reasonably obvious, but despite having seven pages of regulatory compliance it does not mention ISO viscosity grade.  I wonder if they simply don't pay the appropriate fees.  Interestingly, they also make a 480 grade, which is actually over 500 Cs at 40, and a 1000 grade, specifically for non-condensing engines, specifically Zee's Stanley Steamer (note Chris has to build a workshop crane and a road truck now, so the Stanley is well down his list!)

Hi Willy, thanks for posting the picture of the can.  I did not know who manufactures this particular oil, but with a name, Mr Google came up with it immediately, with a local manufacturer here, in addition to the one near you, and some in other parts of the world.  With 5 litres on your shelf, it might be worth doing the obligatory search, downloading the safety data sheet from Morris, and you will have on file more ways of saying "nothing to see here" than you will ever need.  More seriously, if you ever feel unwell and wonder why, it will give you the information you need to eliminate your steam oil as a possible cause.   However, it also gives you the viscosity, recommended temperature range and recommended applications, (steam up to 175 psi and over 200 C) in addition to the regulatory safety data.  The high  viscosity is the reason it looks "goopy", but this will reduce at higher temperature in your cylinder, in a manner not specified on the data sheet, but not too much viscous drag on your engine.

I suspect your question is really about what "compounded" means, as the can clearly states it is steam oil.  Probably the spell checker does not believe you, a common problem with technical writing.  Interesting also that the can says "protect from frost".  This is telling us something about the composition without being very specific.  If you read that data sheet, you will find it is a hydrocarbon oil which has been hydro treated and solvent de-waxed before they add fatty compounds including tallow. 

Many petroleum oils come with hydrocarbon based paraffin waxes and similar, which cause the oil to set to a soap-like solid.  The presence of these compounds is indicated by the pour point, and I have seen oils with a pour point well into the ambient temperature range, which makes them difficult to handle.  It is not just an increase in viscosity, but a solidification in the form of a wax crystal structure which traps all the oil over a very small temperature range, rather like freezing.  Quite different from the gradual continuous change of viscosity with temperature.  Definitely looks and feels like a block of soap. 

So they de-wax with a solvent process to remove the paraffin wax, then add tallow and other compounds which improve the properties as a steam cylinder oil.  The hydro treated part means the base oil is treated with hydrogen at high pressure to saturate the double bonds, as in the term saturated hydrocarbon.  Converts ethylene into ethane, propylene into propane and so on.  I don't know if this also breaks the ring compounds.  Some of my compressors were part of a hydro treater plant, but now I am on the spot, I am not 100% sure of all that the process does.  We need input from a chemical engineer for that.

No doubt it is the tallow and other unspecified additives that require the protection from frost, as the de-waxed base oil should only show a viscosity increase at lower temperature.  I would guess that the term "compounded" is used to describe the total of all those things they do to make the oil more suitable for the specific purpose, a bit of a witches brew really.

I have tended to reserve its use for the lubricator and a drop on the piston and valve rods where they come into contact with steam, but the data sheet says it is also good for application on slides and pins by oil can, so it might be good for all those hard to lubricate pins on my diagonal engine.  I guess they all get hot enough to be worth using the special steam oil.  So thanks again for pointing me in the right direction.

Thanks for looking in,

MJM460

[zeeprogrammer]

specifically Zee's Stanley Steamer (note Chris has to build a workshop crane and a road truck now, so the Stanley is well down his list!)

I'm flattered that Chris has named his Stanley Steamer after me. 

[Dan Rowe]

MJM, here is a comparison of the methods used to determine viscosity grades... I did not know that there were so many in existence.
http://www.tribology-abc.com/abc/viscosity.htm

Dan

[crueby]

specifically Zee's Stanley Steamer (note Chris has to build a workshop crane and a road truck now, so the Stanley is well down his list!)

I'm flattered that Chris has named his Stanley Steamer after me. 

And the Zanley Zeemer also needs special steam oil, already its trouble!   

[Maryak]

The higher viscosity grades, (680+), were normally reserved for use with superheated steam in the likes of Weirs Glissard Valves and are not usually compounded. Compounded normally meaning an emulsifier has been added to the base oil. Good for ensuring the oil gets where it needs to go but making it more difficult to remove from the feed in the hot well before returning to the boiler so better used on non-condensing engines.

Regards Bob

[MJM460]

Hi Zee, glad to see you are looking in.  I hope the rest of the thread is also of interest.

Hi Dan, I guess if you are into tribology you could spend a lot of time comparing the different methods.  No doubt they each have advantages and disadvantages.  Unfortunately the data sheet does not specify the method they use, but centistokes at 40 degrees C will probably fit into any system.

Hi Chris, I don't know how you fit in checking so many other threads as well as achieving your amazing progress on the Marion.  I never miss reading a post.  I am learning so much from seeing your methods.

Hi Bob, glad to hear from you again.  I noticed the bit about the emulsifiers in the data sheet.  I have to look again at my observations on the oil drained from my lubricators.  I will try again with a clean glass collector vessel, and see if I can take a good photo.  I don't know if I was fooled by the nice clean oil colour at the surface compared with the grey mucky interface of the previous oils.  I don't know if my observation was mistaken, or if the emulsifiers break down at some point though that does not seem likely.  Perhaps it is some action of the other additives in the other oil.  The data sheet certainly says these oils should not be used if the condensate has to be cleaned for use as boiler feed. 

With no questions from Willy for a day or two, I went back to a list I prepared quite early on, a list of possible topics.  I think we have covered them all except the entry on noise and sound, and that came from Willy.  At the time, I think it was raised in the context of losses that reduce efficiency.  But we have compensated for that omission by covering quite a few extra topics.

I don't really have a lot to say about noise, but even quite loud noises generally involve very tiny numbers when measured in watts.  So while noise is evidence of inefficiency, the numbers don't seem very significant.  What is often more significant is a frequency analysis of noise, as the frequencies present are often important clues as to the actual noise source, just as vibration analysis also yields important clues to the source of the vibration.

This is supposed to be a knowledge base, but it is of not much use if the topics cannot easily be located.  I am going to try a change of pace and spend some time in the next few days, listing topics and post numbers/ dates.  When I have a reasonable listing, I will post the list, it might be possible to make it a "sticky" that stays at the top for easy reference.  While I am doing that, I will still be looking in each day, and will be very glad to look at new questions, or even more information on topics previously covered.  I don't really believe there are no further questions.  So if you have something you have observed and are wondering about, or something I have not explained clearly enough, please post a question.

I also have finally made that thermowell for my gas fired marine boiler, so I will do a test run to calculate the steam raised to add to data about the capacity of various types of boilers.  I don't have a coal fired boiler, so if anyone who has a coal fired boiler it would be great if you could do some steam raising tests and see if we can build up some data to help people decide how big a boiler they need.  That is a topic that has not really been completed, mostly due to lack of data.  I am also preparing some long steam pipes to try if I can do some pressure drop tests.  I will report on these as soon as I get some data.

Thanks to everyone for following along,

MJM460
 

[steam guy willy]

Hi MJM , I have been quite busy outside with the lovely weather, working at the allotment and socialising...I do have more questions but am always thinking they might be silly or they have been answered before !! so here goes.....If you had a gas in a container that was static and left for a long time  (100 years)  would the individual elements settle out into layers !!!???? Also when you use gas from a bottle it can cause frost to form on the outside . does this inhibit the efficiency and flow to the burner, and if the canister was well insulated would that be better for the burner to be more efficient ?? i don't know what i am trying to say here but it is just an observation !!! I am not spending so much time in the WKSP either ...Also can i still use the 680 oil in the low pressure engines with no adverse problems ??  Also if you did expose the 680 to frost what would happen to it ??   If one knows why and how things happen then one would respond and take heed sensibly !!!

Willy

[MJM460]

Hi Willy, don't worry about whether you have asked a question before.  If my answer had been really clear, you would assimilate the information and know the answer when the question arose again.  If I have another go at an answer, it will be different words, as I am not into search, copy, past type answers, I prefer to just talk about the subject while providing the information.  And you don't normally ask silly questions. 

A mixture of gases left for a long time?  This is always an interesting question.  Basically, gas molecules do not occupy much space out of the total volume even when they are close to condensing.  And they move around very fast, and experience many collisions with each other and with the walls of the vessel.  The collisions with the walls are the cause of what we experience as pressure, while the collisions ensure exchange of energy so it is well distributed.  But basically, in a vessel, each gas occupies the whole volume as though it was the only one there.  I believe that is generally referred to as Dalton's law of partial pressures.  And in any moderate sized vessel, there is no difference in pressure between the top and the bottom.  Of course gravity has an effect, that is why air stays near our planet, and does not expand out until it is lost in space.  The difference in pressure between the top and bottom of a liquid column is easy to see, and can be calculated by pressure equals density times height times acceleration due to gravity.  The same formula applies for gases, but the density, instead of being 1000 kg/m^3 as it is for water, is nearer 1 kg/m^3 for air, at atmospheric pressure, so the difference in pressure with height is almost insignificant.  However it is real.  So each gas will occupy the whole volume, but it's density in the space will be higher near the bottom than at the top.  As the total pressure is the sum of all the partial pressures, I suspect the heavier components of the mixture become a little more concentrated near the bottom, and the statistics of the collisions mean that the lighter ones become slightly more concentrated nearer the top.  I don't believe they ever settle out into layers, as that would imply minimal velocity in that random motion, but in the long term, especially in a very tall vessel, I would expect to see some evidence of a concentration gradient.  So still all gases found at every height, but the proportion of the heavier ones will be a little higher than average at the bottom and a little lower at the top, while the lighter ones will be slightly more concentrated at the top. 

With the gas bottle, it is important to recognise the the bottles store "liquified gas".  The normal ones are propane or butane or a mixture of the two, stored at a pressure sufficient to keep most of it in liquid form at ambient temperature.  Before you light the burner, the bottle, the vapour and liquid inside the bottle are all near enough to atmospheric temperature.  The pressure in the bottle is the vapour pressure of the liquid gas, in the same manner as steam in your boiler is at the vapour pressure of water at the relevant temperature.  But for liquified petroleum gases the vapour pressure at atmospheric temperature is much higher than the vapour pressure of water at atmospheric temperature.  The boiling point of these liquids is much lower than water at atmospheric pressure.

The burner draws gas from the vapour space at the top of the bottle, so lowering the vapour space pressure.  Some of the liquid evaporates as the vapour pressure of the liquid is now higher than the pressure in the gas space, just like some water evaporates in your boiler when some of the steam is allowed to escape.  The latent heat has to come from somewhere, and unless your gas bottle has a steam coil or similar heat source, the heat can only come from the sensible heat in the remaining liquid.  As a result, the liquid gets cooler, and heat starts to flow in from the atmosphere, due to this temperature difference.  But at the lower temperature, the vapour pressure of the liquid is lower, so there is less pressure to cause flow to your burner, a bit like turning the gas jet down to keep the kettle simmering once it has come to the boil.  You can feel the lower temperature below the liquid level on the outside of the bottle, and if you draw gas fast enough, so that the temperature of the liquid gets below the dew point of the surrounding atmosphere, then moisture from the atmosphere will condense on the outside of the bottle as you have observed. That condensation indicates a lower temperature of the liquid inside the bottle, so lower pressure to the burner.  That assumes the burner is connected directly to the gas bottle.

The flow of gas through the tiny orifice at the burner depends on the pressure immediately upstream of the orifice.  If your fuel is butane, or a mixture with less than about 30% propane! that is probably what you have.  With propane, the vapour pressure is much higher again, and you normally have a regulator.  Now, if you have a regulator in the gas line, the pressure at the burner orifice will be determined by the regulator.  The regulator is in effect a variable orifice, set up to control the pressure downstream of the regulator.  If the pressure at the inlet to the regulator is a bit low, the regulator will open a bit to maintain the downstream pressure, which is also the inlet pressure to the burner orifice.  While the regulator is able to maintain its set pressure, there will be no difference at the burner.  Well, if you are able to look very closely, as the temperature falls, the density will be increasing, so there will be a bit higher mass flow to the burner.  However, once the regulator is fully open, if your gas bottle continues to get colder (which it will do until the heat input from the atmosphere is sufficient to boil the required liquid,) the situation is the same as no regulator.  Lower pressure means lower flow to the burner, so less heat.

A bit of a long winded answer.  I hope it is clear, but it is only when you write it out in full that you see just how many things are going on.

I would definitely continue to use your 680 grade oil for your models.  The Morris data sheet says it is suitable for saturated and low superheated steam up to 175 psi and 230 deg C.  I am mindful of what Bob said regarding using it for higher temperatures in full size practice.  I suspect it is a matter of viscosity range, and balancing lubrication benefits with engine efficiency.

It is important to understand the effect of viscosity.  Basically viscosity determines drag on a lubricated bearing, much as friction determines drag on a dry bearing.  In the simplest terms, while friction at a moving bearing tends to be relatively independent of the sliding speed, viscous drag is proportional to velocity.  And in oil products, viscosity reduces with increasing temperature.  While the oil viscosity is specified at a moderate, standard temperature, in the is case 40 C, at operating temperature, the viscosity is much lower.  So for a high working temperature, you would select oil with higher viscosity (at 40 C), while for a lower working temperature you would select a lower viscosity oil (again at 40 C) to have the right viscosity at a lower working temperature.  Like moment of inertia, there is a considerable range of acceptable viscosity.  In general, with higher viscosity oil, there will be more viscous drag, but the bearing would be able to sustain higher load without metal to metal contact, while with lower viscosity, there would be less drag, and less load bearing capacity.

In a race car, where you want every last watt of power available, or on an ocean liner where fuel is a major operating cost, you would tend to select lower viscosity, and cut it finer on load bearing capacity.  On earth moving machinery, you might go for greater load bearing capacity to handle the unpredictable loads when the shovel hits rocks, and hang the fuel efficiency.  In your model engines, normally run unloaded, or relatively low load, efficiency is not usually a big issue, but you would not want to have to rebuild some of the wearing parts every few runs.  You probably would choose higher viscosity within reason.  So it is not unreasonable for you to continue to use the 680 grade within the manufacturers temperature limits.   Morris have a 1000 grade for higher superheat temperatures, however, Bob, in his marine career, might well choose the lower 680 grade at those operating conditions.  Experience soon pushes industry to a preferred selection within the acceptable range.  However, when you have used all your 680 grade oil, you might choose the 460 grade which would let your engines run a little more freely. 

There is another consideration, that is operating speed.  Because viscous drag is proportional to speed, a high viscosity oil gives good load bearing capacity and only limited drag at low speed.  While if you build a high speed engine for a planing model boat, the drag, with the same oil at similar temperature but at that higher speed would be much higher.  You might then want to go to the 460 grade oil for less drag on the higher speed engine, to leave more of the available power to drive the propellor.

The warning to protect from frost suggests to me that the tallow and other additives in the compounding formulation are prone to freezing.  Without knowing just what they mean, it is hard to tell whether, like ice blocks, you just need to warm them to melt them and stir them well before use in a running engine, or are they like bananas, never quite the same again.  In the mean time, I suspect that acting sensibly means maintain the temperature above freezing in storage.  In a cold climate, that might mean heating in the storage area, or keeping the oil indoors.

I hope that makes a few topics a little clearer, bit please keep asking, they are all interesting and even important questions.

Thanks everyone for following along.

MJM460

[steam guy willy]

Hi MJM, thanks for the info ...the gas question however was asked to enquire if the Carbon  and Hydrogen might separate out !! as most substances are trying to get back to its most stable form ( my car trying its utmost to become iron ore !!!) for example !! and the gas bottle question was about my tea making activities at the allotment ...I boil the kettle with butane and i was wondering if it would be more efficient if the bottle was actually buried under the shed in the soil !! I had one stolen as it was outside the shed and so more about security actually !!...Perhaps i should ask these questions with the actual answer i require !!!  thanks for all these extra observations with your answers as so much more knowledge is actually imparted , also new words... tribology for example ...does this word also equate/relate to 'tribulations' ..as in the phrase rubbing somebody up the wrong way !!??

Willy

[Admiral_dk]

Some places in the English speaking world gas = gasoline, and that triggered me, before I re-read your question Willy, but ....

Modern gasoline is not the same as what was sold some years ago. The last two years my main road MC has taken many minutes of cranking before firing after the winter break. I discussed this with my local dealer / mechanic and he said that it is funny because they do from time to time get a bike in that has 10-15 year old gasoline in the tank and they start immediately, but take a similar bike that has been standing still for more that two months with modern gasoline and it is almost impossible to start it ...!
My guess is the way modern gasoline is treated - they convert a heavier oil into high octane gasoline and it works nicely as long as it is fresh, but apparently the most flammable part of it evaporates even from inside the pressure lines on the vehicle or changes properties as you suggest

[MJM460]

Hi Willy, OK, that is a different question.  Yes, amplification of the question to provide a bit of a clue to what you are thinking would help me get to the point a bit quicker.  Not much point in providing lots of irrelevant information, no matter how good the information. 

So not talking about a mixture of gases, but hydrocarbon molecules.   The hydrogen and carbon in hydrocarbon fuels are not separate hydrogen and carbon molecules floating around in the same space, the hydrogen and carbon atoms are very tightly held together in very strict proportions, as discrete molecules, by covalent bonds which are very strong.  Each carbon has four bond sites, while each hydrogen has one.  This gives a huge range of possible combinations.  One carbon can have one hydrogen at each site, so one carbon to four hydrogens makes methane.  But one or more of those sites can join to another carbon, either different ones, or even the same one.  If they join to one or two carbons we get those chains that start with methane, two carbons make ethane, three make propane, four butane and so on, with hydrogen at all the other positions.  Enough variations to make a whole post without even going past four carbons, but if there is a limit, it is much higher.  If a carbon joins to another carbon with two bonds, we get the ...ene series, ethylene, propylene, etc., while if a carbon joins to another with three bonds, we get the acetylene series.  That white paraffin wax your mother used to seal the jar of home made jam is just a very long chain of carbons joined by single bonds, with the other sites occupied by hydrogens.  And those bonds are very strong.  You can bust them apart in a cracking furnace.  (Note, this is not an experiment for the kitchen table!). The gas goes through pipes which form tubes in a furnace.  The high alloy chrome steel tubes are strongly red hot even when your eyes are also experiencing strong sunlight, I don't remember what temperature inside the tubes, but it takes a lot of energy to crack those bonds.  When the gas leaves the furnace and cools, all those separate hydrogens grab what ever bond sites they find, as do the carbons, and all the possible combinations occur in the first second or so.  After fractions of seconds in the furnace, and not much more time to cool, it takes the rest of quite a large petrochemical plant to separate out the ones you want.  Hydrogen and carbon will never settle out of the hydrocarbon molecule by gravity.

Of course, they do like oxygen, so a lot of effort is put into making sure there is no oxygen in those tubes.  And to making sure the tubes don't leak.  But the bonds are strong enough that, in addition to a hydrocarbon and oxygen, you need some energy from an ignition source to break the bonds to give oxygen a chance.  However, your car, being steel will react with oxygen very slowly at atmospheric conditions, especially if there is also a bit of moisture, but the reaction is not so slow if there is a higher oxygen concentration than in atmospheric air and a small spark to start the process.

Regarding your gas bottles, I can't offer much on the security side, but getting the water hot enough for making tea is another mater.  The earth temperature becomes relatively constant not very far down, so most likely warmer than the air above.  You can check the temperature easily enough with your temperature probe at the depth you are prepared to dig.  But the second issue in the equation is the earth conductivity, and whether the earth can transfer enough heat to maintain the pressure.  When the kettle boils, you would need to recover and clean the gas bottle, as the potential for corrosion and bottle leakage is high.

A more reliable procedure might be to stand your gas bottle in a china, glass or even plastic jug.  When the pressure starts to drop enough to affect the burner, tip some of the warmed water into the jug around the bottle, and top up the kettle so it still has enough water for the teapot.  When you have the tea made, you only have to dry the gas bottle.

I don't know for sure where the word tribology comes from, Greek or Latin perhaps?  The ...ology ending is common enough for the sciences, but Tri meaning three does not seem to make sense, unless it refers two surfaces and a lubricant, which are the basis of tribology, or is it trib.. There was a department next door to the engineering school.  I didn't know what went on in there at the time.  The other building I never went inside was the anatomy department, but at least I had some idea of what went on in there, and why I might prefer not to enter!

Seriously, tribology deals with engineering and science of interacting surfaces in relative motion, so friction, bearings and lubrication.  I guess a whole building reflects the importance of understanding friction in every field.  I assume the students experienced plenty of tribulation and did their share of rubbing the wrong way in the most literal sense of the word.

Hi, Admiral DK, I was just about to post when your post appeared.  I am not sure that I have a definitive answer to your conundrum.   I have spent many years of my working life on refinery projects which contribute to those modifications to modern gasoline.  Please let me think about it overnight and I will write something about it tomorrow.  Thanks for posting.  I hope I can come up with something helpful.

Today is a significant day for this thread as it was exactly a year ago that I posted the first entry after asking in another thread if it would be of interest.  I don't know what the number of reads really means, but around 64000 reads in 365 days suggests an average of 175 people a day at least opening the page each day.  I don't spend much time analysing this, but from a modest beginning (though more than enough to encourage me), it has averaged over 400 per day this month.  (We need a bigger theatre Paul!)  I don't know who most of you are, forum members just silently looking in?  Or other visitors?  But I hope you are all finding interesting information, perhaps learning something you didn't know before and are enjoying the read.

I have made about 350 posts, and there have been about 550 by others in response.  Thank you all for responding, and especially to Willy who has provided a stream of interesting questions to start my conversations.   As always, much more satisfactory to feel like I am talking to someone who would like to know, rather than just writing stuff.  However, I am sure Willy won't mind if someone else suggests a topic of interest.  I am quite happy to say so if I don't know anything about the subject, so don't be shy.  And don't be shy to ask again of I miss the point of your question, or even just don't provide the vital step for understanding.  This stuff is all about understanding what goes on, it is not just simply learning facts.

I have a list of projects arising from the discussions, and some boiler tests to complete, so I hope to continue for a while yet.  But if I miss a day here and there, I will probably be out in the shed, collecting some more data, or making swarf for extra fittings I will need, or even at the computer analysing data when the boiler has cooled down and returned to the shelf.  And if you have measured something relevant to the performance of your model, please tell.

Thank you again everyone, whether you are following along, or just looking in,

MJM460

[MJM460]

Yesterday, Admiral DK's post appeared while I was writing, so I deferred a more complete answer for today. 

Certainly fuels have changed since the early days of oil discovery, but I don't believe there is anything sinister about it.

In the really early days, oil was transported to a refinery where it was separated by simple distillation into fractions of varying boiling point.  No doubt the lightest fractions were lost to the atmosphere during transport and storage, so there would be minimal light components such as ethane and propane.  There would have been a straight gasoline fraction, kerosene, light oils, black oils and tar.  The tars were used in road making, black oil largely went into ships bunkers, many a marine engineer will tell you it was dirty stuff.  But with a few minor variations that is roughly what happened.

Refineries have been modified over the years, initially simply to upgrade the low value fuel products in less demand into higher value gasoline and diesel products, increasingly to find an alternative sales outlet for the reducing bunker demand.  Then more recently to meet more stringent government regulations. 

So lead compounds, initially added to improve octane ratings have been phased out and processing units, called reformers, built to upgrade low octane components to replace the lead.  Catalytic crackers with a fluidised catalyst bed, crack the long chain components in heavier oils and increase the available lighter products.  (The heavier components are a bit easier to crack than the light ones I was talking about yesterday.)  Processing to reduce the sulphur content of the fuel was introduced to reduce air pollution in response to newer regulations.

Those losses to atmosphere are now reduced to nearly zero at every step of the way, and no deliberate venting for many years now.  I have been in teams designing many of those process units.  My responsibility was the compressors, so I know what is done to minimise and even eliminate emissions in that area.  I am not the process expert, but I think that summary will give you the general picture of what has happened.

You can see that gasoline was originally (back when vintage cars were the latest technology, not just 10 or 15 years ago) originally a full range natural product, just as it came out of the ground.  However, now most of the nasties are removed, and less saleable heavy, dirty products reformed into components in the gasoline range.  But gasoline is still a mixture, described in terms of boiling point range, together with initial and final boiling points.  Extra butane is added in winter season to give easier starting of engines, and less in summer when the temperatures make those lighter components less necessary.

I don't know all the details, just the general picture, but it is perhaps not too surprising that the fuel might behave a little differently these days, particularly after long term storage in the uncontrolled conditions in a fuel tank on a vehicle in a shed somewhere.  The other side of these changes is that our cars are no longer spewing out lead compounds or many other nasties.  The refineries are much more tightly controlled and our air is much cleaner for it.   No one is telling me what to say.  I don't even know if "they" would even approve.  But I suggest that the fuel is definitely not inferior, definitely much cleaner and has essentially the same energy content as ever.  It may even be better in some ways.

No doubt the day will come when electric or hydrogen powered vehicles, or who knows what else, will provide our needs, but we don't yet have everything in place for that.  And such change takes time. 

I don't know if that answer is helpful.  It is easy to notice the difficulty of starting, and in these days of conspiracy theories, wonder if we are being cheated.  It takes too many people to design and operate a modern refinery to ever keep the lid on any conspiracy.  I am sure you can rest assured that in return for that loss of starting ability on stale fuel, you have a cleaner, more uniform quality fuel of equal energy content.  The oil industry would probably help their image a bit if they were more open about the changes.  But for most people, so long as the car makers make cars that will run on today's fuel, it's not a big issue, it doesn't last long in the tank, so the conversation should probably give more emphasis to the reduction in air pollution.  It is still continuing.

You can probably remember the days of small high compression engines.  We used to get good performance from quite small engines.  I used to have a 1100 cc engined Renault 10.  More than enough power for most purposes, short of the race track.  Now we have lower compression, but much larger engines, and it has taken many years to get past the fuel efficiency of those high compression engines.  At first we had half the concentration of pollutants, but twice the volume, which I couldn't see as much improvement.  But the nature of the exhaust was changed, fewer oxides of nitrogen are formed in the low compression engines, and that helps our atmosphere in very beneficial ways.    But we are getting there and even surpassing the efficiency those early engines, with much cleaner exhaust.

That is the story as I understand it.  I hope it is essentially accurate.  I am sure we have members of the forum with much more expertise than me on the engine side of things.  We may also have chemical engineers who know more about the changes in refining, so I will leave it to them to correct any misunderstandings I may have, and tell us more about the effects of all the changes in fuel on how they design and tune modern engines.

We can fondly remember the days when those smelly fuels enabled such easy starting no matter how old the fuel, and compare the features of engines that have come about in response.  Be glad the old days are gone.

I hope that helps, thanks for following along,

MJM460