The Steam Chimney: A Maritime Research Blog

April 27, 2020 Posted by: Christopher Edwards

 

When one talks of entering the engine room of a ship, it is usually implied that you will be climbing down below deck. Though this is usually true, for the steam Ferryboat Eureka it is also equally true to climb up and around it. Along with the walking beam engine (nearly 5 stories tall) there are other structures that reach upward. One of these is a curious annular (ring-like) metal chamber that surrounds the base of the smoke stack.

In delivering steam steam from the boilers around a ship, common practice at the turn of the 20 century had steam pipelines from a ship’s boilers combine into larger ones which in turn delivered steam to the various steam driven equipment throughout vessel. On board the Eureka and many other steamships with similar engines, however, the individual steam lines from each boiler first delivered their steam to the above-mentioned annular chamber. Only from here did the various delivery pipelines branch out around the ship. 

This annular chamber on Eureka has been known by a few labels over its museum ship life. Some sources described it as a simple super heater. Other park staff, who have been around long enough to know long-since departed volunteers with direct connection to the ship’s history, have heard these volunteers refer to it as an economizer. In general, however, this item has simply been accepted as the way the railroad, who owned the vessel, set up the engine room.

 

A drawing of the Eureka showing the annular chamber
surrounding the base of the stack (marked here as
“superheater”). Image Source: SAFR collection #:
HDC 555, drw, B4.24-2


There are, in fact, many similar unusual items and arrangements in the engine room. Most of these are simply because Eureka had a long career dating from 1890-1957, and during this time went through many changes. This constant element of change is still visible in the engine room today and often leads steam technology enthusiasts to scratching their head as to why something exists or why the long-departed engineers of Eureka did something the way they did.

The annular chamber, however, has continually perplexed me. This is not simply an unusual piping arrangement or pumping set up. This is a major item of immense size. It’s so large, in fact, that it requires four very robust riveted support legs underneath it to support its weight. Every time I looked at it, the same basic questions always floated through my head.
 

• Why arrange steam distribution this way? Why not simply merge the pipes into traditional delivery lines direct from the boilers?
• Did this chamber really provide superheating and was superheating necessary?
• And, was there ever an official name for this thing and when was it installed?

While there is an ongoing effort to provide thorough answers for the above questions, recent research has provided a lot of information as well as the long sought for name. This item was known as a Steam Chimney and its function was to prevent priming (water carry over from the boilers into the piping), dry out the steam by evaporating water droplets suspended within it, and to provide a limited amount of superheat. In today’s terminology you might call it a simple waste-heat superheater. It was invented in 1827 by James P. Allaire. His original patent apparently involved a dual chamber arrangement where steam entering from the boilers first passed through an outer space from top to bottom, and then curved around a wall at the bottom edge and then proceeded back up an inner space in immediate contact with the skin of the smoke stack. The steam was then drawn out of the top for delivery throughout the engine room. (Eureka’s version is simplified by having only a single chamber where steam enters the bottom and exits via the top.) A few years later, another design appeared that neatly avoided the patent description.  In this design, the actual steam chimney was physically part of the top of the boiler. The function of this newer design, however, was the same as the design in Allaire’s patent and was likely meant to avoid royalty payments. 

The value and success of the steam chimney was and still is debated. One historic source, the Journal of the Franklin Institute of the State of Pennsylvania (Vol II, 1828), stated:
 

“Mr. Allaire may probably expect to derive some advantage of heating the steam just as it is passing into the vacuum of the cylinder, as this appears to be his intention; but we apprehend that this advantage, if any, will be very small, as the density of the steam in his cylinder will be less than in the boiler.” (italics original)¹ 

And even today, among park staff, the value of such a device is a bit unclear, for reciprocating steam engines function very well with saturated steam in which water particles are suspended within the steam. These water particles tend to assist in lubricating the piston within cylinder. Additionally, steamships in the late nineteenth and early twentieth centuries that were equipped with triple expansion engines utilizing steam at pressures well above 100psi still operated with saturated steam and were without anything like a steam chimney. 

Answers, admittedly, are still being worked out and will be revised as research continues. One of the possibilities, however, is that Eureka operated at a steam pressure of 60psi and Walking Beam Engines such as hers usually went no higher than 70psi.²  This is far below what later triple expansion engines operated with. For example, one of the other steam ships within the park, the 1907 built Steam Tug Hercules, operated at a boiler pressure of 180psi. At this pressure, the Hercules’ steam would lose little heat and pressure between the boiler and engine. Eureka, operating at 60psi, might have lost enough heat, within the piping and in the cylinder during expansion, to make such a device as a steam chimney worth while. With this in mind, drying the steam out and superheating it (raising its temperature above the boiling point after evaporating the water particles) a small amount to gain a bit of efficiency may have been useful given the already low efficiency of such a low boiler pressure and single expansion engine. 



A steam chimney of the original type placed separately
from the boiler around the base of the smoke stack. This
drawing appears to show the specific variety like what is
extant on the Ferryboat Eureka with with a single annular
chamber, steam admitted via the bottom, and drawn out
of the top. The steam experiences only a single pass
through it, vs. the double pass of Allaire’s original design.
Image Source: The American Marine Engineer, “Questions
on Marine Engineering,” The American Marine Engineer
vol. x, no. 5 (May 1915): 26


What is definite, however, is that steam chimneys appear to have been common on steamboats/ ships with walking beam engines. Whether this was universal in all steam vessels operating in the 60psi range or lower is still being looked into. However, a drawing of the only other surviving walking beam engined vessel, the S.S. Ticonderoga (now a museum ship at the Shelburne Museum in Shelburne, VT) and drawings of the San Francisco Bay steamer S.S. James M. Donahue (also walking beamed engined) both show steam chimneys of the type attached directly to the boilers.

Finally, when was this apparatus installed? Research has shed a likely answer here as well via a Boiler Inspection Report of the Steamboat Inspection Service now in the custody of the Historic Documents Collection of the park. This report, dated July 1911, was prepared for the then-named Ferryboat Ukiah. 

It details both the machinery of the vessel as well as what occurred during the hydrostatic test of the boilers. At this time, the Ukiah had two main boilers of a type described as firebox flue return tubular (more on this in a separate blog) and that there were several failures during this test. The inspector noted that the boilers were old and would need replacement soon (which was accomplished in 1914). Among many failures noted, one in particular indicated the failure on boiler number 1 of several stay bolts of the steam chimney.³  This statement clearly indicates that the steam chimney was belonging to boiler number 1 and that, thusly, it was of the type directly attached to the boiler itself (e.g. each boiler had its own steam chimney).This being the case, it means that the current steam chimney was most likely installed when the Ukiah had her new boilers installed in 1914 and are still on the Eureka today. This is further backed up by photos of the vessel taken during its rebuild from 1920-1922. In these photos, the walking beam engine still shows its wooden frame. After being rebuilt as the Eureka, the engine had a metal frame. This would mean that the image is showing the Ukiah being stripped down before being built back up as the Eureka. So, in this image that likely shows Ukiah (not yet Eureka), the separately mounted steam chimney is clearly visible.