Ask the average person what a steam locomotive burns, and they will probably answer “coal.” Some might also say “wood.” “Oil” is considerably less likely to be uttered, but in fact, it’s just as valid of an answer, and oil-burning steam locomotives were more common than one might think. If you have any burning questions about oil burners or their local historical context, then hopefully they are answered in some form or another on this page.
How is this different from a diesel locomotive?
The image of a coal-burning steam locomotive is so strong in the public imagination that a common reaction to finding out a steam locomotive burns oil is to question whether or not it’s a “real” steam locomotive. It doesn’t help that some heritage railroads with oil burning steamers run them on actual diesel fuel. These are still true steam engines (and are not true diesel engines), because engines are not defined by what fuel they use (although some are less flexible than others in this regard), but rather by how they use it.
An oil-burning steam engine uses its fuel in the same way as a coal- or wood-burning one: it burns the fuel in order to raise steam, and this steam (the working fluid of the engine) is used to generate mechanical work. Because the combusting fuel does not directly generate work or make direct contact with the working fluid, steam engines are a type of external combustion engine. The changes necessary to burn liquid fuel (see “But how did they do it?” below) are fairly small and do not involve any changes to the working fluid. Locomotives on some railroads were converted back and forth between coal and oil multiple times in their lives as they were transferred to different divisions with different fuel availability.
By contrast, diesel engines are a type of internal combustion engine – the fuel is burned inside the cylinders and the rapidly-expanding combustion gases serve as the working fluid. The different working fluid and more explosive method of pushing down the pistons mean that diesel cylinders and steam cylinders are built radically different from one another and are not interchangeable. Conversion of a steam locomotive (of any fuel type) to a diesel locomotive thus requires discarding the actual “engine” part of the engine and was rarely done.
But how did they do it?
The key differences between a typical oil-burning steam locomotive and a coal- or wood-burning one begin in the tender and end in the bottom of the firebox. There’s the obvious addition of an oil tank in place of a coal bunker, but depending on the kind of oil being used, there may also be a heater. Historically, the type of oil used – either crude or roughly equivalent to Navy “Bunker C” oil – was extremely viscous at room temperature and required heating to around 100ºF to really begin flowing.
Being liquid, the oil obviously can’t rest on a grate as it burns. Instead, a burner nozzle atomizes the oil with a jet of steam and sprays it into the firebox like a flamethrower. This might seem a bit extreme, but it’s the best way to allow enough oxygen to reach the fuel; a fire burning on the surface of an oil pool would quickly become an asphyxiated, sooty mess. Refractory bricks are used to prevent the combusting fuel-air-steam mixture from damaging the firebox walls and their arrangement varied in the early years, but solutions eventually converged on the mixture being ejected into a brick-lined channel called a firepan, located just below the firebox proper. A continuous supply of combustion air to feed the fire (as well as to control its direction through draft) enters through several openings in the firepan and can be adjusted via dampers. At the opposite end of the firepan from the burner is a brick flash wall, which deflects the combustion gases upwards into the firebox.
But when/where/why did they do it?
Short answer: beginning in the late 19th century / in areas where there was a lot of oil but not a lot of good coal / because it was easier and/or cheaper to get.
Long answer: there are several practical benefits of oil over coal – no embers, burns cleaner (usually), less physically demanding to stoke the engine, easier to refuel – but burning liquid fuel also presented several technical challenges, so the use of oil fuel was not as straightforward as that of coal. The world’s first successful oil burners debuted in 1882 on Russia’s Grazy-Tsaritzin Railway. Successful replication of this system followed in 1887 on the Pennsylvania Railroad, but with considerably less fanfare: the abundance and availability of coal led PRR to conclude that there was little point in using oil.
In California, however, “abundance” and “coal” do not belong in the same sentence. The Golden State was infamous for its lack of good coal: a handful of seams do exist in the state, but the coal they produced was near-universally of a barely passable quality – often not passable at all for railroads. There was wood in the foothills and near the coast, of course, but wood’s lower fuel value compared to coal meant that it was only an attractive option where harvesting it was dirt cheap. By contrast, it was becoming increasingly apparent in the late 19th century that California was absolutely loaded with oil, driving continued interest in the fuel and culminating in a flurry of joint Union Oil – Southern Pacific – Santa Fe experiments in 1895 that demonstrated the feasibility of oil burners*.
By 1910, oil was a popular choice of fuel in many petroleum-rich areas, dominant in some, and had replaced coal on nearly every locomotive in California. Outside of these regions, the advantages of oil also made it a popular option in special applications. For instance, the Delaware & Hudson Railroad operated a few oil burners circa 1912 to reduce fire risks in heavily forested areas.
*Successes in Russia and Pennsylvania (among other places such as Peru) clearly did not carry over to Californian railroads initially. Sporadic experimentation here had begun shortly after the debut of oil burners in Russia and successful oil-fired Californian steamships debuted in 1884, but experiments in the Californian railroad environment did not lead anywhere until 1895. Earlier attempts were described as unsatisfactory at best and failed to raise enough steam to run the locomotive at worst.
Adoption of Oil Fuel on Peninsula Railroads
Southern Pacific
As the largest railroad in a state with no good coal, Southern Pacific was a key player in the development of California’s petroleum industry and was happy to do away with the expense of imported fuel. As early as 1900, plans were being drawn up for eventual systemwide conversion from coal to oil, although the immense size of this system meant that the effort took more than a decade. It’s unclear when the Coast Division (including the line up the Peninsula) finally rid itself of coal, but the effort was probably nearing completion by 1906, if not earlier.
Atchison, Topeka & Santa Fe
The first Santa Fe locomotive in the City was Santa Fe Terminal Company #1, a tiny 0-4-0 built in 1899 and arriving in early 1900. According to the California Trolley & Railroad Corporation (which now has the still-extant locomotive on display in San Jose), it was “built to burn oil,” which would mean that Santa Fe’s operations on this side of the Bay were oil-burning from the start. If there were any subsequent coal (or wood) burners barged over from the East Bay, they would all become oil burners within a few months anyways, because Santa Fe issued a shop order in late 1900 to convert every single locomotive on the rosters of its other Californian subsidiaries to oil. This work had evidently been done by the close of the year, bringing an abrupt statewide end to coal on the Santa Fe right at the turn of the century.
State Belt
The locomotives of the State Belt burned coal until early 1907. Lots of coal was imported by ship through San Francisco, which probably contributed to the late changeover of this endemic line. With a roster of just three locomotives to convert to oil at the time, though, the changeover was rapid. The switch to oil effected “great economy in the cost of fuel and in time necessary for coaling” according to the Board of Commissioners’ Biennial Report. A 72000 gallon concrete oil tank was constructed for fuel storage, and as far as we can tell, the Belt never looked back: every subsequent steam locomotive (including No. 4 of course) was delivered as an oil burner.
Other railroads
With all but two hand-me-down locomotives on its initial roster dating to 1906 or later, Western Pacific was an exclusively oil-burning operation within California from the start. Ditto for the Ocean Shore, once its initial plans for full electrification were abandoned. Seeing as how the Park & Ocean Railroad went in the other direction (i.e. steam to electric) in 1902 and the Cliff House steam line followed in 1905, it’s unclear if either of them converted any of their locomotives to oil.
For the only other three steam railroads which had Peninsula track around this time (all of which were restricted to yards along the State Belt), we do not have much information on the path to oil. The two narrow-gauge railroads, North Pacific Coast and South Pacific Coast, are known to have operated at least some oil burners by 1901, but it seems that neither operated their engines on the City side of the barge ride anyways. It’s uncertain if the standard gauge San Francisco & North Pacific had any locomotives stationed in the City either. It’s likely (though not at all certain) that NPC and SF&NP had completed the conversion by the time they were consolidated into the Northwestern Pacific Railroad.
Miscellaneous Musings About Oil Burners
(Only?) Oil at Bayshore
Perhaps surprisingly, given Southern Pacific’s eagerness to ditch coal, an early draft of Bayshore Yard shown in a 1907 issue of the San Francisco Call featured what may have been the largest and most sophisticated coal bunker ever constructed in California. As far as we can tell, however, it and several other curious features of that draft did not materialize. All subsequent maps and blueprints which we know of show only oil tanks and pipes in its place. Indeed, it’s uncertain if a coal burning locomotive ever set drivers on the premise.
Of course, oil handling comes with some environmental hazards when working on reclaimed land approximately at sea level. Spilled oil could be carried away by rainwater and soak into the ground, contaminating the groundwater and possibly the adjacent Bay as well. In an unexpected display of environmental consciousness from a mega-corporation in the Twenties (or perhaps fearing public outrage that not even the notorious “Octopus” would be able to weather), SP actually addressed this by installing oil traps around the refueling track. These were concrete sumps with baffles inside that separated out any spilled oil carried by rainwater. The oil could then be skimmed out from the sump and reused. A massive oil trap was also installed to handle the grease and grime of the Roundhouse and Shops’ inspection pits, although their low elevation required the contents to be pumped into it.
State Belt No. 4: Vulcan’s First Oil Burner?
(Spoiler: no, but…)
When assembling the body of research on State Belt No. 4’s history, a number of early doucuments made it seem like Vulcan was unfamiliar with oil burners, and so we believed that No. 4 was the first such engine they made. However, this turned out to not be the case, and the (dis)proof was sitting under our noses the whole time!
Among the original Vulcan drawings located for the restoration effort was a drawing for an oil tank heater. We say an oil tank heater because, as had been overlooked, it wasn’t No. 4’s: the drawing actually belonged to an earlier locomotive from 1907 that was destined for New Orleans. Sure enough, after looking back through the Hagley Museum’s collection of Vulcan negatives, we found an exact match for this locomotive occupying construction no. 1167, confirming that it was indeed built and pushing the date for Vulcan’s first oil burner back to 1907 at latest. A 1911 Vulcan catalog was also discovered which indicated that Vulcan was offering oil burners by this time.
After reviewing the replies from San Francisco to Wilkes-Barre (we have not been able to locate the letters going the other way around), it became apparent that Vulcan wasn’t unfamiliar with oil burners per se, but was unfamiliar with the “Southern Pacific oil burning system.” SP was never among Vulcan’s customers and the small Pennsylvanian builder apparently expressed confusion at several other SP standards.
It’s still unclear how common oil burners were for Vulcan before (or after) No. 4. The aforementioned 1911 Vulcan catalog describes all locomotive models as being built “to burn coal, wood or oil as desired,” but the fields on our locomotive’s record card clearly presume coal or wood and had to be edited in post. Vulcan also charged extra for factory-equipping the burner, which evidently was normally installed by the customer. The “hydro-carbon furnace” set up in No. 4’s firebox was considered an industry standard for mainline locomotives, and so the evidently mutual unfamiliarity between Vulcan and patent holder Aetna Combustion Company suggests that No. 4 was some sort of milestone in oil burners for the builder.