Generating Steam

Steam was generated in Titanic’s boiler rooms located just ahead of the engine rooms on the tank top level just above the ship’s keel. The ship carried 24 double-ended Scotch boilers, each 15 feet 9 inches in diameter and 20 feet long with 6 furnaces, three on each end. The ship also carried 5 single-ended auxiliary boilers, also 15 feet 9 inches in diameter but only 11 feet 9 inches long with three furnaces each. Although these single-ended boilers could also be hooked up to the ship’s main steam supply lines, they were generally used to power the ship’s electric generating plant and other auxiliary engines while the ship was in port. The total heating surface of Titanic’s boiler plant was 144,142 square-feet with a grate surface of 3,466 square-feet. All of the boilers were constructed in accordance with the rules of the Board of Trade for a working pressure of 215 pounds-per-square-inch (psi), and were tested to a pressure of 430 psi. They were arranged for working under natural draught conditions, assisted by fans that blew air into the open stokeholds. With the reciprocating engines running at 75 revolutions per minute and 24 double-ended boilers hooked up, a supply rate of just over 260 lbs of steam per minute per boiler would be produced.³

The Scotch marine fire-tube boilers such as the ones used on the Titanic contained a large quantity of water and took a long time to bring it up to pressure. Typically, it took almost 12 hours from the time one of these boilers was lit until it could brought on line at a working pressure of 215 lbs per square inch. A bank of these boilers is shown in the photograph below.

The three furnaces at the end of a Scotch boiler were in the form of corrugated fire-tubes. Each furnace terminated in a combustion chamber surrounded by water. From the combustion chamber the hot gases from the burning coals passed through a bank of relatively small fire-tubes surrounded by water to the smoke uptake box on the front face of the boiler. In the double-ended boilers, overall space was saved since furnaces on opposite ends shared the same combustion chamber. To prevent cold air hitting the combustion chamber’s opposite wall when a furnace door was opened, a baffle of firebrick was typically  installed in the middle of the chamber. The diagram below shows a schematic of one of these double-ended Scotch boilers viewed from the side.

The boiler rooms, also called sections, were numbered 1 through 6. Boiler Room (BR) No. 1 was just ahead of the reciprocating engine room and contained the five auxiliary single-ended boilers. When lit, these boilers would be fired from stokehold No. 1 at the forward end of the room. No. 2 boiler room was forward of No.1 and contained 5 double-ended boilers. The furnaces facing aft were fired from stokehold No. 2 and those forward were fired from stokehold No. 3. Ahead of BR No. 2 was BR No. 3 also with 5 double-ended boilers that were fired from stokeholds 4 and 5, respectively. Similarly, ahead of BR No. 3 was BR No. 4 with stokeholds 6 and 7, and ahead of that was BR No. 5 with stokeholds 8 and 9. Ahead of BR No. 5 was BR No. 6 with stokeholds 10 and 11. However, due to the narrowing of the hull as we approached the bow, BR No. 6 contained only 4 double-ended boilers instead of the usual 5.

The Titanic had four elliptical-shaped funnels, but only the three forward funnels were used to take up the waste gases from the six boiler rooms.⁴ The funnel elliptical cross section measured 24 feet 6 inches by 19 feet 0 inches. Their average height above the casing was about 70 feet. The uptakes by which the waste gases were conveyed to these funnels were united immediately above the watertight bulkheads which separated boiler rooms No. 1 and 2 (J), No. 3 and 4 (G), and No. 5 and 6 (E). The aft most of the three forward funnels with boiler uptakes, the ship’s third funnel, had a transverse baffle in its lower end that divided the funnel between boiler rooms No. 1 and No. 2. This was in the portion between the top of the boiler uptakes and the top of the funnel casing. The aft side of the funnel, serving No. 1 boiler room, had 5 individual flues each serving a single-ended boiler; while the forward side, serving boiler room No. 2, had two flues that were offset to port with each serving one of the two port-side double-ended boilers that could be operated separately there. A large single combined starboard-side flue served the other three double-ended boilers in BR No. 2. The ship’s second funnel also had a transverse baffle in its lower end that divided it between boiler rooms No. 3 and No. 4. In this case, the aft side of the funnel, serving No. 3 boiler room, had a combined flue serving all 5 double-ended boilers in that room. The forward side, serving No. 4 boiler room, had 2 flues that were offset to starboard with each serving one of the two starboard-side double-ended boilers that could be operated separately there. A large single port-side flue served the other 3 double-ended boilers in BR 4. The foremost funnel had only a single transverse division that separated boiler room No. 5 from boiler room No. 6, each served by a single combined flue.

The baffling was eliminated in stages as the temperature of the gases dropped. Initially, there was baffling that divided each bundle of smoke tubes from the next within the same boiler end. Then there were separate uptake trunks from each boiler end. Then, once these merge, interior baffles divided each boiler from the next, and one boiler room from the next up to the top of the uptakes. Then, in the lower part of the funnel, a transverse baffle dividing one boiler room from the other plus the additional baffling as noted above for the single-ended boilers and those double-ended boilers that could be connected separately to the auxiliary steam supply line. The visible part of the funnel above the casing had a single, non-divided inner flue which vented all the gases from the two boiler rooms that it served.

For use at sea, there were automatic ash ejectors equipped in boiler rooms No. 2 through No. 6, the boiler rooms that contained the double-ended boilers. These were recessed into the coal bunkers one located on the port side and the other located on the starboard side in one of the section’s stokeholds. The specific locations of these automatic ash ejectors on the Titanic were: BR No. 2 in stokehold 2, BR No. 3 in stokehold 4, BR No. 4 in stokehold 7, BR No. 5 in stokehold 8, and BR No. 6 in stokehold 10. These ash ejectors were worked from a duplex feed pump located in a small pump room located off the ship’s centerline and recessed into the aft port-side coal bunker in boiler rooms No. 2, 3, 5 and 6. In BR No.4, the pump room was recessed into the aft starboard-side bunker since the recess in the aft port-side bunker was used as a store space.⁵ To remove the ash, a trimmer would wheel it in a barrow to the nearest ash ejector where he would dump it into a hopper. From there the ash would be carried by a water jet up an inclined pipe and ejected well clear of the ship above the waterline.

For port use, four ash hoists were used to lift the ash in canvas bags to small rooms on E deck called “ash places” for later disposal. These were located at the aft starboard side of BR No. 2, the aft port side of BR No. 3, the forward starboard side of BR No. 4, and the aft port side of BR No. 6. 

Each boiler room was separated from another by a transverse watertight bulkhead (WTB) that ran as high as E deck 11 feet above the ship’s load waterline. The coal bunkers feeding the stokeholds were arranged transversely on both sides of these watertight bulkheads, and a watertight passage through the bunker space on the tank top level to starboard of the ship’s centerline allowed access from one section to another and was protected by a drop-down watertight door (WTD). These watertight doors, as well as all the others on the tank-top level, could be dropped by throwing a single switch on the ship’s navigating bridge, or locally by a hand lever located near each door, or automatically by a float under the floor plates should a compartment get flooded accidentally.

Steam from the boiler rooms was carried by two main steam pipes which passed through the watertight bulkheads to the reciprocating engine room. Shut-off valves were located at three of these bulkheads, including the one at bulkhead K going into the engine room. This was a quick-acting, balanced emergency valve fitted on each main steam pipe so that the steam could at once be shut off in case of a rupture in either one of the main pipes. On the after side of this bulkhead in the engine room were the main steam stop valves, 24-inches in diameter, each provided with a large separator and a cross connection. The separators were used in saturated steam lines to separate and remove any moisture formed because of heat losses. They worked by providing a series of changes in direction of the steam flow and included a large surface area to intercept the droplets. The cross connection allowed either range of piping to be used for either or both engines. The main stop valves were operated by hand wheels and screws from the starting platform which was situated in the center of the forward end of  reciprocating engine room near the bottom.

The Titanic’s coal bunkers were filled through coaling ports located just above F deck. Although the major bunker spaces ran transversely across the ship, they also filled some side space that ran longitudinally between decks F and G. The ship’s coal bunker capacity was over 6,600 long-tons, enough for 8 days of steaming at full speed.

For the purpose of specifying bunker capacities, letter designations were given in the Harland & Wolff drawing office notebook. These spaces and their designations are shown in the figure below. Also shown are the location of the watertight bulkheads and their letter designations,⁶ the locations of the watertight passages through the bunkers and their watertight doors on the tank-top level, ash ejector recesses and ash hoist locations, and the locations of the coaling ports on F deck.

The capacities in tons of Titanic’s coal bunkers are given in the table below.

The simplified diagram below shows a typical midship boiler room with its bunker spaces.

To work the 24 double-ended boilers while at sea during a four-hour watch period required 48 firemen, 20 trimmers, and 5 leading firemen, also called leading stokers. Each boiler room required 4  trimmers to work the coal and carry the ash to the ejectors. That is because there were two stokeholds in each of these rooms, one forward and the other aft, and each stokehold had two bunkers to work, one to port and the other to starboard. To feed the boiler furnaces required from 8 to 10 firemen. One fireman was responsible for working one end of a given double-ended boiler. Thus 10 firemen were needed in boiler rooms No. 2 through No. 5 that had five double-ended boilers in each. In boiler room No. 6, with only four double-ended boilers, only 8 firemen were needed. The men in each of these double-ended boiler rooms were supervised by a leading stoker. If some of the double-ended boilers were not lit, the extra personnel in a watch section would be assigned other jobs like cleaning machinery, etc.

Each of the six boiler rooms were equipped with an illuminated telegraph that received orders from a single transmitting telegraph located in the engine room. The illuminated colored orders read, from top to bottom, STOP (red), SLOW (blue), HALF (green), and FULL (white).⁷ There was also a Kilroy’s stoking indicator equipped in each of the 11 stokeholds. These were controlled by two stoking regulators that were located in the engine room. The stoking indicator showed which of the three furnaces was to be fired at a given end of a boiler at a given time. Only one of the three furnaces on a given end would be opened at any time, and an arrangement was made on the stoking regulators so that corresponding furnaces on the other end of a double-ended boiler would never be opened at the same time. The stoking regulator set the time that each furnace was to be fired. It could be set to regulate the firing of the furnaces every 8, 9, 10, 12, 15, 20, 25, or 30 minutes, depending on how much steam was needed and the number of boilers that were connected up at any given time.

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