converting UP 4014 from coal to oil

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converting UP 4014 from coal to oil
Posted by NP Eddie on Thursday, July 18, 2019 6:29 PM

How did the UP convert the 4014 from coal operation to oil operation? I asssume that a large oil tank is placed in the tender where the coal was stored. Also, what are the two former steam tenders used for?

Ed Burns

Retired Clerk from Northtown and too young for steam.

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Posted by Overmod on Thursday, July 18, 2019 6:54 PM

In general, oil conversion involves an arrangement that replaces the firegrate and 'gas plume' from coal combustion with a suspended combustion plume of ignited atomized oil.  This usually involves partially lining the firebox with a 'firepan' of some high-temperature material and providing careful primary and secondary air. 

Details of the specific conversion on 4014 have not been extensively publicized, perhaps because the team wants to be sure any problems are 'ironed out' first.  The situation likely involves more than 'scaling up' the system that has by and large worked well on 3985.

Many of these engines are intended to run on #5 heavy fuel oil or the equivalent (NOT 'residual') and the 'oil tank' in the tender bunker area therefore needs coils or some other means to heat the oil to fluidity ... but not much beyond that or the dread 'gassing' may start.  The most familiar kinds of burner use steam to give final heat and spray atomization (see the von Boden-Ingles burner for one successful principle) rather than pressure atomization as in the Racer burner.

The two 'tanks' (from gas turbines) are for water.  Even fire trucks hooked up to water mains have a hard time giving a locomotive this size 'cruising range' to the next logical support time in a few minutes, so it pays to be able to carry hundreds of miles' worth of critical water with you.

Incidentally the issue of the NWHS Arrow (v14n1, Jan/Feb 1998) which contained one of the 'debunking' articles about N&W supposedly cheating in the 1952 F-unit comparison test also has a good article about oil-firing conversion, including the approach used (without lasting success) on UP 4005.

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Posted by Overmod on Tuesday, July 30, 2019 9:47 AM

Let me 'bump' this as considerably more detail is known now than a couple of weeks ago...

The conversion was made with a modified Thomas burner, not very different from the arrangement on 3985.  There is a comparatively thick flash wall (Austin Barker indicated about 3' although I haven't actually seen it) which positions the backward-firing burner well behind the actual throat plate of the firebox.  There is no refractory on the circulators, and in fact any portion of the arch that may have been carried on them has been removed.  Interestingly, although I would think this would cause increased 'quench' in the combustion plume I haven't seen any abnormal increase in the need for sanding, or for that matter increased unburnt matter in the exhaust beyond what I'd consider normal hazing at periods of high steam demand and draft.

Oil bunkerage is 6200 gallons, and the fuel is waste motor oil.  I have not verified how this fuel is treated before used; normal 'best practice' is to wash it, to separate out some of the additives in commercial motor oil that can cause issues (like ZDDP or other friction modifiers) and any hygroscopic hydraulic oil or antifreeze, and then use centrifugal separators (which are commercially available for this specific purpose and are pretty cost-effective below about 120gph capacity) to remove water from the oil.  It is possible that UP outsources its oil delivery to parties that presumably provide good QC in this regard; someone might comment on the companies whose trucks have been observed refuelling 4014 on this trip so far.

Feed was stated (by both Barker and Dickens) to be purely by gravity.  I don't think waste motor oil requires extensive heating to flow in cold weather, and certainly doesn't need the careful coil management that, say, 4449 would.  I wouldn't be surprised to find some heating arrangement on the locomotive somewhere, considering how low Plains temperatures can get (to say nothing of Chicago!) but don't know yet what the details actually are.

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Posted by Leo_Ames on Tuesday, July 30, 2019 10:05 AM

Interesting, I thought Union Pacific switched years ago to burning the same diesel fuel in their steamers as the rest of their locomotives use. 

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Posted by ATLANTIC CENTRAL on Tuesday, July 30, 2019 10:05 AM

Since most internal combustion engines use relatively light oil these days, can we assume that the oil is pretty light weight? Not an expert here, but that seems like a really good approach.

Sheldon

    

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Posted by Overmod on Tuesday, July 30, 2019 10:09 AM

Leo_Ames
I thought Union Pacific switched years ago to burning the same diesel fuel in their steamers as the rest of their locomotives use. 

I only know what Barker and Dickens say for 4014.  I'd be suspicious if 844 had been converted to #2 gas oil (and it would have been a complicated conversion if 'conventional wisdom' about the higher required mass flow and other considerations is right) and then further converted during the 'quality' rebuilding to the heavier oil.

Jack Wheelihan might be a good source to consult on this.  He may not know 100% of the specifics, but could get you up to speed on the possible vs. the unlikely and then direct you to people in the industry who'd know the rest.

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Posted by Overmod on Tuesday, July 30, 2019 10:24 AM

ATLANTIC CENTRAL
Since most internal combustion engines use relatively light oil these days, can we assume that the oil is pretty light weight?

You raise a highly interesting point which I hadn't thought about before you mentioned it.  There's been a great push toward lower viscosity oil as a specific means of enhancing fuel economy (e.g. GM and dexos) and I have no idea what the comparative heat content of, say, 5W20 vs. older common oils is.  Nor do I know if there is a point where operation in a 'lip' burner like a Thomas becomes more difficult or 'dribblier' depending on viscosity.  It is also more than possible that enhanced friction modifiers are in the formula, and it is less than likely that their chemistry takes account of (or optimizes) their combustability...

To an extent, the waste oil probably tends a bit toward the 'heavier' side as mixed, and likely has increased somewhat 'in service' as it ages, starts to crosslink, etc.  There certainly appears to be little if any problem in burning waste oil in 4014's burner even at remarkably high turndown.

A point I didn't establish in the earlier post: For reasons not directly associated with the boiler, it's become 'preferred' to keep 4014 above 200psi at all times she's standing.  To do this, instead of adding internal heat exchangers or heating elements like the arrangement in the rebuilt Kriegslok 8055, they periodically fire the burner.  What I found fascinating was that they didn't see the need to purge the combustion spaces with the blower before lighting off whatever part of the burner is used for slow 'pressure building,' nor did they use any blower at all for enhanced draft after starting to fire.  (You can hear the feed through the burner, but there is nothing but natural-circulation heat eddies visible at the stack.)

I would not have thought this practical ... but there it was.

Later they did need either quicker or better heat rise, and did augment the draft -- fairly gently -- using the blower.  This produced the first of the pops lifting within no more than a couple of minutes, so the heat's there and effective whatever the viscosity or chemical makeup in the outsourced feed is.

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Posted by Flintlock76 on Tuesday, July 30, 2019 1:00 PM

Leo_Ames

Interesting, I thought Union Pacific switched years ago to burning the same diesel fuel in their steamers as the rest of their locomotives use. 

 

Canadian Pacific did when their steam program was active.  As Bill Stetler, head of the steam program at the time, told the story one day the fuel oil delivery truck didn't show up and they had to refuel with something, so they fueled it with diesel.  It worked perfectly, and they never looked back. 

What the long term effects of burning diesel versus fuel oil (actually it was reclaimed waste oil, like 4014's using now) might have been we'll never know.  They used diesel effectively from 2003 until Hunter Harrison killed the steam program.  Super Angry

They also credited burning diesel as one of the reasons CP 2816 was typically clean enough to eat off of!  That and a lot of elbow grease by the crew, of course.

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Posted by SD70Dude on Tuesday, July 30, 2019 4:13 PM

I can understand wanting to keep plenty of pressure in the boiler, means you are ready to move on a moment's notice.  While it may only take 30 PSI of steam (or a diesel's main reservoir air supply) to run the burner and blower(s), it will probably take at least a couple hours to build up a good head of steam from that starting point. 

We burn used motor oil in our engine, which of course is much, much smaller than 4014.  It is supposed to be "re-refined" but in reality they never get all the water, antifreeze and other "goodies" out of it.  Some of that stuff will settle to the bottom of the tender tank after sitting for a while, but some globs remain in suspension in the oil. 

Before lighting up we drain off as much of the watery residue as possible (don't worry, it is caught and properly disposed of) and then blow shop air back into the tank through the burner oil line.  This mixes the remaining residue with the oil quite nicely, so you don't get a slug of water/antifreeze/ATF coming down the line and putting the flame out.

In years past another volunteer had arranged a deal with the local transit agency to donate unprocessed used oil straight from one of the bus garages.  Their fleet at the time was largely composed of GM New Look buses with 'green leaker' Detroit engines.  I'm told this "fuel" was absolutely awful to work with, and many oil spills resulted from flameouts. 

In contrast, it seems that straight used diesel locomotive engine oil is a pretty good fuel.  It should be around 40W, with a little bit of diesel fuel (makes lighting up easier), minimal water content, and zero antifreeze or ATF. 

Greetings from Alberta

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Posted by Flintlock76 on Tuesday, July 30, 2019 4:55 PM

'Dude, there was a steam tourist railroad in New Jersey from the mid-60's to 1981 called the Morris County Central that burned waste oil.  The 'roads chief organizer, Earle Gil, drove a tanker truck around all the gas stations in that area periodically collecting the oil, mostly from engine oil changes.  The gas stations gave him the stuff, just glad to be rid of it, so they fueled their two steam engines free.

If there are any issues with the waste oil no-one ever mentioned it.

Sadly the Morris County Central went out of business in 1981.  Mr. Gil was the driving force, and when a job transfer took him out of state the 'road collapsed without him.  

 

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Posted by SD70Dude on Tuesday, July 30, 2019 5:06 PM

Our deal with Edmonton Transit continued for years too, for the same financial reason.  The stuff was usable, just very difficult to work with, especially when lighting up. 

I believe the idea of bubbling the oil tank with air didn't come about until after we ceased burning the straight bus oil, that would have made it infinitely easier to use.

As to the question of viscosity, we haven't noticed any undesirable effects on the burner, firebox and boiler from continuing to burn used motor oil.  But in Alberta there is a disproportionate ratio of diesel trucks to small cars, so it is likely that the used oil has plenty of 5 or 15W40 to go along with the lighter 20W stuff. 

Greetings from Alberta

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Posted by Electroliner 1935 on Saturday, August 03, 2019 11:31 PM

Overmod
The conversion was made with a modified Thomas burner, not very different from the arrangement on 3985.

Can you direct me to some source of information on what a "Thomas burner" is. Google sent me everywhere but nowhere on finding anything about the thing. Thanks

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Posted by Overmod on Saturday, August 03, 2019 11:58 PM

Here's an article from aptly enough Locomotive Fireman's Magazine discussing the early history of the burner and showing its basic principles.  (Not missing a trick, the same story appears in other locomotive firemen's publications of the time...)

There is some contemporary advertising in trade publications, but I have not found anything that postdates WWI yet.  Somebody with one of the free copies of the '22 Cyc might look to see if this company or any other still made or sold this design 'in commerce' then.

 

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Posted by tdmidget on Sunday, August 04, 2019 12:16 AM

SD70Dude

I can understand wanting to keep plenty of pressure in the boiler, means you are ready to move on a moment's notice.  While it may only take 30 PSI of steam (or a diesel's main reservoir air supply) to run the burner and blower(s), it will probably take at least a couple hours to build up a good head of steam from that starting point. 

We burn used motor oil in our engine, which of course is much, much smaller than 4014.  It is supposed to be "re-refined" but in reality they never get all the water, antifreeze and other "goodies" out of it.  Some of that stuff will settle to the bottom of the tender tank after sitting for a while, but some globs remain in suspension in the oil. 

Before lighting up we drain off as much of the watery residue as possible (don't worry, it is caught and properly disposed of) and then blow shop air back into the tank through the burner oil line.  This mixes the remaining residue with the oil quite nicely, so you don't get a slug of water/antifreeze/ATF coming down the line and putting the flame out.

In years past another volunteer had arranged a deal with the local transit agency to donate unprocessed used oil straight from one of the bus garages.  Their fleet at the time was largely composed of GM New Look buses with 'green leaker' Detroit engines.  I'm told this "fuel" was absolutely awful to work with, and many oil spills resulted from flameouts. 

In contrast, it seems that straight used diesel locomotive engine oil is a pretty good fuel.  It should be around 40W, with a little bit of diesel fuel (makes lighting up easier), minimal water content, and zero antifreeze or ATF. 

 

The only thing found in ATF that is not in  engine oils is the red dye. Automatic transmission oils of today especially are generically antiwear hydraulic oils. Aintifreeze and water readily selly out and can be rapidly removed with coalescing filters.  A used oil fuel should certainly be filktered to removed any possible contaminants but mythology does not contribut anything. With steam atomization even a bit of water would never be noticed.

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Posted by Overmod on Sunday, August 04, 2019 10:02 AM

tdmidget
A used oil fuel should certainly be filtered to remove any possible contaminants but mythology does not contribute anything.  With steam atomization even a bit of water would never be noticed.

Part of the difficulty is that relative flameholding in the burner is of importance in some designs; another is that turndown can be something of a problem when poor flameholding isn't 'counteracted' by high temperature ignition source reasonably close to the plume.  There are documented instances of locomotives fueled on 'unrefined' WMO that have encountered running problems with slugging causing low-fire problems -- I consider these more to be problems with the design and practice of their burners than with the overall 'combustibility' of the fuel.

This is complicated a bit in practice, at least for me, because of a source I encountered a few years ago, involving the combustibility of sprayed fluids against a high-temperature fixed source..  If I tried to tell you that a coolant leak would turn into a torch, but a gasoline leak wouldn't, I'd be lambasted worse than any poster in Kalmbach history -- but that was the result of actual testing.

Up to the time I read that, I was an unreformed Ted Pritchard-style high-pressure mechanical-atomization advocate, even in large-scale steam locomotive applications.  These are geared toward generating a large radiant plume, but usually not producing an excessively high temperature in nominally thermally-insulating refractory intended to 'protect' the inner firepan and firebox surfaces around and below the actual throw of the burner.  This is precisely the sort of design susceptible to slugs of higher-flash-point or high-volatility contamination, whereas a large pan of the kind of broken refractory or 'lava rock' brought up to incandescence provides lavish effective flameholding and spot ignition contact as described for steam-atomized material of many kinds ... probably including glycol coolant.

In any case, the use of waste motor oil in von Boden-Ingles or Thomas ... or, probably, Gyro-Jet or other late-steam practical refinements ... is a very different thing from running it as 'black diesel' where much more stringent requirements on both dewatering and contaminant removal would need to be observed.  The versions of dewatering centrifuge we were using for the Cliffside 110 project involved little more than the spinning-dome-with-lip type of separator; rather obviously, using one of the high-speed types like this one or this one produces a much 'better' product at relatively little marginal cost (for most excursion operation, anyway).  My own suspicion is that the dewatering, for most large-volume railroad systems that are inherently gravity-feed, is by far the more important operation for pre-treating received feedstock before pumping it in for storage; the general advice I've received indicates that dome centrifugation is a better method than coalescing filtration and dependence on gravity separation as it handles throughput at least semi-automatically with good quality and can run unattended for long periods of time with positive separation.  Since many of the contaminants are inherently hygroscopic this allows a certain amount of intentional 'fuel washing' followed by defined removal of the 'aqueous phase' in the same continuous pass with no clogging that default centrifugation would.  

We were at least considering a test whether high-speed centrifugation as a second step would produce actual benefits for non-expert firemen in typical excursion-locomotive running, or provide measurable benefits of any kind for steam-atomization burners -- heaven knows the incremental cost of the high-speed centrifuge equipment isn't a high expense especially if its use can be 'spread' across a number of organizations, and it's for all intents and purposes a one-time cost.

A problem I see coming is that when a sizable amount of entrained water has had time to settle out in the bunker, it will of course preferentially pond somewhere low in the structure, probably in the portion kept as a 'well' against just the sort of slugging issues railroads running oil fuel might expect to face in practice (e.g. rain getting in when the locomotive is refueled on the road).  Just the wrong motion of the tender going over the road might cause preferential feeding of large slugs of water into the gravity line going to the burner -- resulting in dramatic loss of actual combustible mass precisely at the time water at relatively low temperature, with a known and enormous propensity to absorb heat as it 'swells' into incombustible vapor, is being flashed in the burner.  Something I don't know offhand (but a millwright well might!) is whether hygroscopically affected oils like brake fluid have higher density than the hydrocarbon main oil, and might therefore be preferentially included in such slugging.

In any case, whether you centrifuge or coalesce I think it does make sense to dewater the received fuel in one step, even though small amounts of water in fuel would (as stated) flash with little effect due to the effective superheat in the atomizing steam.

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Posted by Electroliner 1935 on Sunday, August 04, 2019 2:14 PM

Overmod
Here's an article from aptly enough Locomotive Fireman's Magazine discussing

Thanks for the link. As Artie Johnson used to say on Laugh In, "Verrrry interesting", In addition to explaining the E. W. Thomas Burner, the magazine contained many other nuggets of wisdom and some humor such as: What is a fixed signal? One that has been sent to the shop and repaired. 

And: In case of doubt, what should be done? NOTHING.

See page 796 for more

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Posted by tdmidget on Sunday, August 04, 2019 3:29 PM

Overmod

 

 
tdmidget
A used oil fuel should certainly be filtered to remove any possible contaminants but mythology does not contribute anything.  With steam atomization even a bit of water would never be noticed.

 

Part of the difficulty is that relative flameholding in the burner is of importance in some designs; another is that turndown can be something of a problem when poor flameholding isn't 'counteracted' by high temperature ignition source reasonably close to the plume.  There are documented instances of locomotives fueled on 'unrefined' WMO that have encountered running problems with slugging causing low-fire problems -- I consider these more to be problems with the design and practice of their burners than with the overall 'combustibility' of the fuel.

This is complicated a bit in practice, at least for me, because of a source I encountered a few years ago, involving the combustibility of sprayed fluids against a high-temperature fixed source..  If I tried to tell you that a coolant leak would turn into a torch, but a gasoline leak wouldn't, I'd be lambasted worse than any poster in Kalmbach history -- but that was the result of actual testing.

Up to the time I read that, I was an unreformed Ted Pritchard-style high-pressure mechanical-atomization advocate, even in large-scale steam locomotive applications.  These are geared toward generating a large radiant plume, but usually not producing an excessively high temperature in nominally thermally-insulating refractory intended to 'protect' the inner firepan and firebox surfaces around and below the actual throw of the burner.  This is precisely the sort of design susceptible to slugs of higher-flash-point or high-volatility contamination, whereas a large pan of the kind of broken refractory or 'lava rock' brought up to incandescence provides lavish effective flameholding and spot ignition contact as described for steam-atomized material of many kinds ... probably including glycol coolant.

In any case, the use of waste motor oil in von Boden-Ingles or Thomas ... or, probably, Gyro-Jet or other late-steam practical refinements ... is a very different thing from running it as 'black diesel' where much more stringent requirements on both dewatering and contaminant removal would need to be observed.  The versions of dewatering centrifuge we were using for the Cliffside 110 project involved little more than the spinning-dome-with-lip type of separator; rather obviously, using one of the high-speed types like this one or this one produces a much 'better' product at relatively little marginal cost (for most excursion operation, anyway).  My own suspicion is that the dewatering, for most large-volume railroad systems that are inherently gravity-feed, is by far the more important operation for pre-treating received feedstock before pumping it in for storage; the general advice I've received indicates that dome centrifugation is a better method than coalescing filtration and dependence on gravity separation as it handles throughput at least semi-automatically with good quality and can run unattended for long periods of time with positive separation.  Since many of the contaminants are inherently hygroscopic this allows a certain amount of intentional 'fuel washing' followed by defined removal of the 'aqueous phase' in the same continuous pass with no clogging that default centrifugation would.  

We were at least considering a test whether high-speed centrifugation as a second step would produce actual benefits for non-expert firemen in typical excursion-locomotive running, or provide measurable benefits of any kind for steam-atomization burners -- heaven knows the incremental cost of the high-speed centrifuge equipment isn't a high expense especially if its use can be 'spread' across a number of organizations, and it's for all intents and purposes a one-time cost.

A problem I see coming is that when a sizable amount of entrained water has had time to settle out in the bunker, it will of course preferentially pond somewhere low in the structure, probably in the portion kept as a 'well' against just the sort of slugging issues railroads running oil fuel might expect to face in practice (e.g. rain getting in when the locomotive is refueled on the road).  Just the wrong motion of the tender going over the road might cause preferential feeding of large slugs of water into the gravity line going to the burner -- resulting in dramatic loss of actual combustible mass precisely at the time water at relatively low temperature, with a known and enormous propensity to absorb heat as it 'swells' into incombustible vapor, is being flashed in the burner.  Something I don't know offhand (but a millwright well might!) is whether hygroscopically affected oils like brake fluid have higher density than the hydrocarbon main oil, and might therefore be preferentially included in such slugging.

In any case, whether you centrifuge or coalesce I think it does make sense to dewater the received fuel in one step, even though small amounts of water in fuel would (as stated) flash with little effect due to the effective superheat in the atomizing steam.

 

DOT 3 and 4 brake fluids are actually very heavy alcohol related compounds. They are soluble in water and would mix with water/ antifreeze mixtures. Like antifreeze, they will burn at a high ignition temperature. DOT 5 brake fluid is a silicone compound and I am not familiar with it's flamability. It is not very common, primarily found in antique and classic cars due to not mixing with water.

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Posted by SD70Dude on Sunday, August 04, 2019 4:03 PM

tdmidget
SD70Dude

I can understand wanting to keep plenty of pressure in the boiler, means you are ready to move on a moment's notice.  While it may only take 30 PSI of steam (or a diesel's main reservoir air supply) to run the burner and blower(s), it will probably take at least a couple hours to build up a good head of steam from that starting point. 

We burn used motor oil in our engine, which of course is much, much smaller than 4014.  It is supposed to be "re-refined" but in reality they never get all the water, antifreeze and other "goodies" out of it.  Some of that stuff will settle to the bottom of the tender tank after sitting for a while, but some globs remain in suspension in the oil. 

Before lighting up we drain off as much of the watery residue as possible (don't worry, it is caught and properly disposed of) and then blow shop air back into the tank through the burner oil line.  This mixes the remaining residue with the oil quite nicely, so you don't get a slug of water/antifreeze/ATF coming down the line and putting the flame out.

In years past another volunteer had arranged a deal with the local transit agency to donate unprocessed used oil straight from one of the bus garages.  Their fleet at the time was largely composed of GM New Look buses with 'green leaker' Detroit engines.  I'm told this "fuel" was absolutely awful to work with, and many oil spills resulted from flameouts. 

In contrast, it seems that straight used diesel locomotive engine oil is a pretty good fuel.  It should be around 40W, with a little bit of diesel fuel (makes lighting up easier), minimal water content, and zero antifreeze or ATF. 

The only thing found in ATF that is not in  engine oils is the red dye. Automatic transmission oils of today especially are generically antiwear hydraulic oils. Aintifreeze and water readily selly out and can be rapidly removed with coalescing filters.  A used oil fuel should certainly be filktered to removed any possible contaminants but mythology does not contribut anything. With steam atomization even a bit of water would never be noticed.

Have you ever actually lit up or fired a oil-fired steam locomotive?

The difference between draining off the settled residue and re-mixing the tank, or not doing so is amazing.  I don't know exactly how the used oil re-refining process works but whatever filters they use certainly fail to catch a fair amount of 'crap'.  And the fuel quality can vary widely between loads.

Compounding the problem, the oil line on steam locomotives is gravity-fed directly from the bottom of the tank.  Any non-oil residue will of course settle to the bottom and fill the line, and unless you mix it up again first this is what you will be trying to light up with, in a cold firebox to boot.  

Even bad fuel with a relatively high water content will vaporize properly and/or spontaneously ignite when exposed to the red-hot brick of a operating firebox, but the same is not true if the engine is cold.

And those of us who do not have access to a external source of steam have to run the burner on compressed air when lighting up.  It works, but not nearly as well as steam, and with air you do not get the added benefit of heat.  

Greetings from Alberta

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Posted by SD70Dude on Sunday, August 04, 2019 4:12 PM

Overmod

Part of the difficulty is that relative flameholding in the burner is of importance in some designs; another is that turndown can be something of a problem when poor flameholding isn't 'counteracted' by high temperature ignition source reasonably close to the plume.  There are documented instances of locomotives fueled on 'unrefined' WMO that have encountered running problems with slugging causing low-fire problems -- I consider these more to be problems with the design and practice of their burners than with the overall 'combustibility' of the fuel.

The steam atomizer burners in question here were designed and intended to run on heavy fuel oil (No. 5, No. 6) from refineries.  And to operate hot all the time.  The problems we are discussing here all occur outside those normal operating parameters. 

Running such a steam locomotive on waste oil or a lighter grade of fuel oil could be compared to running 100% kerosene in a diesel engine.  It will burn and the engine will run on it, but there are other consequences that may not be obvious initially, and additional steps that need to be taken to avoid them. 

Greetings from Alberta

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Posted by tdmidget on Sunday, August 04, 2019 4:25 PM

Overmod

 

 
tdmidget
A used oil fuel should certainly be filtered to remove any possible contaminants but mythology does not contribute anything.  With steam atomization even a bit of water would never be noticed.

 

Part of the difficulty is that relative flameholding in the burner is of importance in some designs; another is that turndown can be something of a problem when poor flameholding isn't 'counteracted' by high temperature ignition source reasonably close to the plume.  There are documented instances of locomotives fueled on 'unrefined' WMO that have encountered running problems with slugging causing low-fire problems -- I consider these more to be problems with the design and practice of their burners than with the overall 'combustibility' of the fuel.

This is complicated a bit in practice, at least for me, because of a source I encountered a few years ago, involving the combustibility of sprayed fluids against a high-temperature fixed source..  If I tried to tell you that a coolant leak would turn into a torch, but a gasoline leak wouldn't, I'd be lambasted worse than any poster in Kalmbach history -- but that was the result of actual testing.

Up to the time I read that, I was an unreformed Ted Pritchard-style high-pressure mechanical-atomization advocate, even in large-scale steam locomotive applications.  These are geared toward generating a large radiant plume, but usually not producing an excessively high temperature in nominally thermally-insulating refractory intended to 'protect' the inner firepan and firebox surfaces around and below the actual throw of the burner.  This is precisely the sort of design susceptible to slugs of higher-flash-point or high-volatility contamination, whereas a large pan of the kind of broken refractory or 'lava rock' brought up to incandescence provides lavish effective flameholding and spot ignition contact as described for steam-atomized material of many kinds ... probably including glycol coolant.

In any case, the use of waste motor oil in von Boden-Ingles or Thomas ... or, probably, Gyro-Jet or other late-steam practical refinements ... is a very different thing from running it as 'black diesel' where much more stringent requirements on both dewatering and contaminant removal would need to be observed.  The versions of dewatering centrifuge we were using for the Cliffside 110 project involved little more than the spinning-dome-with-lip type of separator; rather obviously, using one of the high-speed types like this one or this one produces a much 'better' product at relatively little marginal cost (for most excursion operation, anyway).  My own suspicion is that the dewatering, for most large-volume railroad systems that are inherently gravity-feed, is by far the more important operation for pre-treating received feedstock before pumping it in for storage; the general advice I've received indicates that dome centrifugation is a better method than coalescing filtration and dependence on gravity separation as it handles throughput at least semi-automatically with good quality and can run unattended for long periods of time with positive separation.  Since many of the contaminants are inherently hygroscopic this allows a certain amount of intentional 'fuel washing' followed by defined removal of the 'aqueous phase' in the same continuous pass with no clogging that default centrifugation would.  

We were at least considering a test whether high-speed centrifugation as a second step would produce actual benefits for non-expert firemen in typical excursion-locomotive running, or provide measurable benefits of any kind for steam-atomization burners -- heaven knows the incremental cost of the high-speed centrifuge equipment isn't a high expense especially if its use can be 'spread' across a number of organizations, and it's for all intents and purposes a one-time cost.

A problem I see coming is that when a sizable amount of entrained water has had time to settle out in the bunker, it will of course preferentially pond somewhere low in the structure, probably in the portion kept as a 'well' against just the sort of slugging issues railroads running oil fuel might expect to face in practice (e.g. rain getting in when the locomotive is refueled on the road).  Just the wrong motion of the tender going over the road might cause preferential feeding of large slugs of water into the gravity line going to the burner -- resulting in dramatic loss of actual combustible mass precisely at the time water at relatively low temperature, with a known and enormous propensity to absorb heat as it 'swells' into incombustible vapor, is being flashed in the burner.  Something I don't know offhand (but a millwright well might!) is whether hygroscopically affected oils like brake fluid have higher density than the hydrocarbon main oil, and might therefore be preferentially included in such slugging.

In any case, whether you centrifuge or coalesce I think it does make sense to dewater the received fuel in one step, even though small amounts of water in fuel would (as stated) flash with little effect due to the effective superheat in the atomizing steam.

 

DOT 3 and 4 brake fluids are actually very heavy alcohol related compounds. They are soluble in water and would mix with water/ antifreeze mixtures. Like antifreeze, they will burn at a high ignition temperature. DOT 5 brake fluid is a silicone compound and I am not familiar with it's flamability. It is not very common, primarily found in antique and classic cars due to not mixing with water.

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