The locomotive diagrams come from one of Rolly's books:
Firing Locomotives; JW Harding; 1912-1928; International Textbook Company, Scranton, Pennsylvania.
... ICS/ITC was a huge correspondence course operation. They provided educational materials for many fields. Today, their extensive coverage of railway subjects provides a valuable insight into many old technologies.
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| Sheet music title page. from: archive.org scanned by Newberry Library. |
... The section on oil burning steam locomotives dates from 1912, and the particular technology used by the Southern Pacific Railroad is often cited. The SP and the ATSF were the pioneers in oil burning. This came about because most of the developed deposits of coal were found in the east or midwestern US. For fueling locomotives, the cost of transporting coal halfway across the continent could not compete with California's abundance of cheap, heavy crude.
The discovery of oil in the US southwest began circa 1890-1900 and heavy oil could be had for under a dollar per barrel. In the Firing Locomotives text, it explains that the lighter oils are richer in hydrogen content, while the really viscous oils are heavier in carbon content. Their respective heat outputs are fairly close, with the heavy stuff yielding slightly more heat. If you're a railroad buying in bulk, the heavy oil was the fuel of choice.
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| from: Geology of Petroleum; William Harvey Emmons; 1921; McGraw-Hill. |
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| Unused, undated postcard. |
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| from: Google circa 2026 Summerland, California. |
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| Unused, undated postcard. It has nothing to do with California, but I thought you might enjoy it. I suspect this long-lens shot was actually taken from the Oklahoma Capitol Building - not an aircraft. Today, all of the oil producing structures are gone and a large tree obscures this view of the governor's mansion. |
In addition to avoiding the transportation cost of coal, there was another advantage to oil. Fuel oil can be convinced to flow in pipes. Everywhere coal went, something had to physically take hold of it and lift it or move it where it was wanted ... from mine, to breaker, to hopper car ... [half way across the continent] ... to coal dock, to tender, to fireman's shovel or mechanical stoker. And then the ashes had to be handled.
... But, as we'll see, lighting heavy bunker oil on fire would not be as easy as lighting a propane barbeque.
* * *
But, be careful what you buy and store on railway property!
You'll remember that the untested Bakken crude oil involved in the Lac-Megantic Disaster (6 July 2013) was more volatile than its Safety Data Sheet classification had suggested. Its initial boiling point (an indicator of the presence of dissolved gases like methane, propane etc) was probably closer to 95 degrees Fahrenheit (35 degrees C). Its correct classification was probably UN 1267, PG1, 'High Danger'.
A century earlier, this book is raising a similar caution about petroleum sold to the company as 'fuel oil'.
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Looking at Southern Pacific Railroad equipment circa 1910 ...
The Tender
With the warning above about volatile components in the oil, they definitely did not want to be running a propane barbeque. The design of the tender supported the type of fuel being used.
A important feature of this tender plays a critical role in a future post. That is, the oil feed valve. The oil can be shut off at the tender by using that bell-crank arrangement. The seat of the intake valve is built up slightly so the oil is not drawn from the lowest level in the tank. See 'drain valve', below.
Another key feature of the valve assembly's design it that it is spring-loaded to ensure it closes.
Some tender designs have the oil reservoir above the tank holding water. Given the viscous nature of this fuel oil, having a greater hydraulic 'head' helped the oil to flow more freely.
... Failing that, steam is piped directly to the location near the oil feed valve. No effort is made to heat the whole volume of oil held in the tender. The 'tank heater pipes' end in simple T-connections which send the steam into a total of four different directions.
The drain valve removes fluid at the lowest level of the tender oil tank. One important function of the drain valve is to prevent water contamination in the oil from entering the burner at the firebox. As some steam from the tank heater pipes may condense and lie under the oil above, this is another source of contamination the drain valve is designed to remove.
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| from: The Central Pacific & the Southern Pacific Railroads: Lucius Beebe; 1963; Howell-North. |
Built by Alco in 1909, the 3066 will take the Pacific Limited from San Francisco to Roseville, California.
Photographed at Oakland in 1915.
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Under the Firebox
Here is what we find under a Southern Pacific firebox. The front of the engine is off the diagram to the left, the tender is just beyond the right margin. We're just going to follow the oil from the tender to the single burner at the front of the firebox. The dotted lines represent the locomotive frame.
To oil feed pipe on tank (bottom right)... is where we get our fuel oil from the tender.
The oil enters the superheater.
It comes out at the oil burner.
Usually, 'superheater' refers to a device designed to give the steam for propulsion more energy. To make things confusing for us, they use the same term for a completely different device. At this superheater the oil enters a pipe which is jacketed with steam because the oil needs to be very hot when it enters the firebox.
Near where it says 'oil burner' is where the fireman's controls terminate for the fuel to the burner ... and to control the 'damper' which admits more air at this location.
For extra credit on the test: The blowback valve allows the fireman to use steam to blast out blockages in the oil line in either direction. They don't show it here, but there is a drain on the front of the superheater to get rid of the water condensing from the steam inside the steam jacket.
Do you see where it says Atomizer Pipe to Oil Burner? 'Atomizer' and 'burner' are synonymous. The Atomizer Pipe carries steam. It is the high pressure of this steam which turns our hot oil into very small droplets, increasing the surface area to the point where it is thoroughly combustible in a very hot flame.
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The Firebox
If you've looked at many coal-burning fireboxes, this arrangement looks strange. Firebrick is used sparingly, there is no brick arch, there are no grates.
On Figure (b) you see the front of the firebox in cross-section, where you find the burner 'a' and the draft tubes 'c'.
On Figure (a) you can see both dampers: 'g' allowing air into the draft tubes, and the firedoor damper 'j'.
The flashwall 'd' and the deflector 'k' are seen at the firedoor 'h'.
The burner 'a' on Figure (a) is located about 6 feet in front of the flashwall.
About 5 feet in front of the burner is where the horizontal draft from the burner ... meets the downward draft from the firedoor.
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The Von Boden-Ingalls Burner (aka, the 'atomizer')
(Southern Pacific's standard burner circa 1912 and into the late 1940s)
The burner is installed using either one of the oil connections at 'a' and the other is plugged.
The steam is connected at 'b'.
The hot oil 'drools' down onto the corrugated lip at 'd'.
Driven by the steam, and the characteristics of the lip, the fine mist of oil roars into a broad, flat flame which spreads across the whole firebox.
The SP used only a single burner of this type on even its largest engines, and only experimented with other types of burners in the late 1940s near the end of steam.
I double-checked and the text gives no function for the plugs 'c' ... so we can make up our own reasons for having them, I guess.
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The Oil Regulator
The Figure (a) shows the side view and Figure (b) shows the top view.
The fireman would move the handle along the quadrant between the stop pin 'f' - regulator closed ... and stop pin 'g' - regulator wide open.
Using the latching arrangement standard to things like throttles and reversers (ignore Figure (c) if you want) very fine adjustments can be made to the oil feed. The book says 10 notches to the inch - but I haven't counted them all.
The regulating stop bolt 'c' is set and tightened in the desired point in the quadrant ...
The regulating stop pin 'd' is designed so its spring-loaded lower edge will push into the slotted head of the regulating stop bolt and stay there.
... this is why ... text from the book ...
"When in use, the regulating stop is locked on the quadrant in such a position that it will hold the regulating lever open just far enough to give a 'drifting fire'; that is, a fire that is as strong as can be carried while drifting or standing without the pops blowing."
... In an internal combustion engine, you would consider this to be the 'idle' setting.
* * *
Firing an Oil Burner
As you can imagine, there are many things to consider when starting a fire, when operating, always avoiding smoke, etc. The text goes on for many pages on all the things to consider. The paragraph below gives a brief sample of the complexity of operating an oil burner.
As you remember, the regulator controls the oil, the atomizer implies controlling the force of the steam to the burner, and there are also the dampers which have a similarly important role in managing the fire.
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| from: The Train; Jonathan Glancey; 2004; Carlton. |
You will recognize one of the first cab-ahead ('cab-in-front', etc) locomotives of the Southern Pacific. The SP needed this kind of power over the mountains between Roseville, California and Sparks, Nevada. However, the regularly-configured engines of this size (or doubleheaders) asphyxiated crews in the many tunnels and showsheds. Forward visibility was often blocked by smoke. So they put the cab on the leading end, and the smokestack at the back.
Built by Baldwin and delivered in 1910, the 4004 started out as a compound. You can see the high pressure cylinders are fed from the steam dome. Then the steam goes to the low pressure cylinders near the smokestack.
However, this engine/class was overhauled as a simple-expansion locomotive in the late 1920s. This reduced maintenance costs, increased tractive effort, and enabled higher speeds beyond the usual 25 mph.
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