TITANIC - watertight compartments-Bulkheads

TITANICOLOGY

"PRACTICALLY UNSINKABLE"

As some people know, the Titanic and her sister ship Olympic were built with a cellular double bottom and divided into 16 major watertight compartments with 15 transverse watertight bulkheads that ran clear across the ship. These watertight bulkheads were labeled "A" through "H" and "J" through "O". (The letter "I" was not used.) The first two and last six of these bulkheads ran as high as D deck while the middle seven ran as high as E deck. Titanic and Olympic were labeled a "two compartment ship" because they could remain afloat with any two adjacent  watertight compartments completely open to the sea without in any way involving the safety of the ship. Since no one could imagine anything worse than a collision near the juncture of two of the these compartments, these ships were often referred to as being "practically unsinkable." 

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Titanic's Watertight Doors and Bulkheads All the transverse bulkheads were carried up watertight to at least the height of the E deck. Bulkheads A and B, and all bulkheads from K to P, both inclusive, further extended watertight up to the underside of D deck. (Bulkhead A further extended to C deck, but it was watertight only to D deck.)  Bulkheads A and B forward, and P aft, had no openings in them. All the other bulkheads had openings in them, which were fitted with watertight doors. Bulkheads D to O, both inclusive, had each a vertical sliding watertight door at the level of the floor of the engine and boiler rooms for the use of the engineers and firemen. On the Orlop deck there was one door, on bulkhead N, for access to the refrigerator rooms. On G deck there were no watertight doors in the bulkheads. On both the F and E decks nearly all the bulkheads had watertight doors, mainly for giving communication between the different blocks of passenger accommodation. All the doors, except those in the engine rooms and boiler rooms, were horizontal sliding doors workable by hand both at the door and at the deck above.  The diagram below shows the location of all watertight doors [shown in red] on the Titanic. The 12 doors immediately above the inner bottom in the engine and boiler room spacesworked vertically. They closed by gravity, and were held in the open position by a clutch which could be released by means of a powerful electro-magnet controlled from the captain’s bridge. In the event of accident, or at any time when it might be considered desirable, the captain or officer on duty could, by simply moving an electric switch, immediately close all these doors. Each door could also be closed from below by operating a hand lever fitted alongside the door. As a further precaution floats were provided beneath the floor level, which, in the event of water accidentally entering any of the compartments, automatically lifted and thus released the clutches, thereby permitting the doors in that particular compartment to close if they had not already been dropped by any other means. These doors were fitted with cataracts which controlled the speed of closing. The time required for the doors to close was between 25 and 30 seconds. Due notice of closing from the bridge was given by a warning bell. A ladder or escape was provided in each boiler room, engine room, and similar watertight compartment, in order that the closing of the doors at any time should not imprison the men working therein. The watertight doors on E deck were of horizontal pattern, with wrought steel door plates. Those on F deck and the one aft on the Orlop deck were of similar type, but had cast iron door plates of heavy section, strongly ribbed. Each of the ‘tween deck doors, and each of the vertical doors on the tank top level could be operated by the ordinary hand gear from the deck above the top of the watertight bulkhead, and from a position on the next deck above, almost directly above the door. To facilitate the quick closing of the doors, plates were affixed in suitable positions on the sides of the alleyways indicating the positions of the deck plates, and a box spanner was provided for each door, hanging in suitable clips alongside the deck plate. ----------------------------------------------------------------------------- In reality, the design was closer to a three compartment ship for the most part as can be seen by reference to the diagram below which shows the maximum number of compartments that can be flooded in any given location without the ship foundering. These were derived from the ship's floodable-length curves which were published in the 1997 RINA Transactions by Hackett and Bedford, "The Sinking of S.S. TITANIC - Investigated by Modern Techniques." The design of these vessels almost met a three-compartment standard except for three conditions: flooding in hold 3 and boiler rooms 5 and 6, flooding in boiler rooms 4, 5, and 6, and flooding in both engine rooms and the electric dynamo room. Other than these three conditions, the ship would remain afloat with any 3 adjacent compartments open to the sea.

Flooding By Compartment

At the British Inquiry into the loss of the Titanic, H&W's naval architect Edward Wilding presented a plan that he called "Flooding by Compartment." This plan was developed to show how the Titanic would trim down by the head as individual compartments are flooded one at a time beginning with the first and working aft. It was used solely to show how the waterline of the ship would change as subsequent compartments are allowed to flood to the waterline, and was used to show when water would have overtopped the transverse watertight bulkheads if carried to various heights. It was not derived to demonstrate how the ship actually flooded as quite a few misinformed people tend to believe. The animated sequence is shown below followed by the text that describes what was presented by Wilding.

Condition B0 - The first plan shows the ship in the unflooded condition with the waterline marked as a solid blue line. Condition B1 - "The first thing was to flood the forepeak tank, that was the foremost compartment of the ship, which is marked in yellow, and which gave the yellow waterline." Condition B2 - "I then flooded No. 1 hold, which is tinted green, and I got the green waterline. That is No. 1 hold plus the forepeak."Condition B3 - "I then, in addition to having the forepeak flooded and No. 1 hold flooded, flooded No. 2 hold, which is marked brown, and I got thebrown waterline. When No. 2 was flooded it would flood the firemen's passage, because, the waterline has then got above the step in the bulkhead and can go down the stairs. Of course, as you will see, the water is still at that time below the level of the top of the bulkheads which run to the E deck."Condition B4 - "Then, having flooded the forepeak and No. 1 and No. 2 holds, I also flooded No. 3 hold, which I then wanted to indicate by the red space which is represented by the red line."Condition B5 - "I then flooded No. 6 boiler room, in addition to the others, of course, which is shown in the blue tint, and gave the blue waterline. You will now see that the water [from No.1 hold] had got up above the top of A bulkhead, and would get down into the rest of the forepeak. It means the eventual foundering of the ship."Condition B6 - "I then flooded No. 5 boiler room in identically the same way as I had previously flooded No. 6, adding its flooding effect to the forward spaces, and I got the black line, which, as you will notice, puts the forecastle entirely under water, and also the forward end of  B deck."Condition B7 - The next was the partial flooding of BR 4 shown in dashed red. "The [dashed] red line is approximately parallel to the forecastle head, and it shows that the stern is out of the water as far about as the base of the mainmast [the mast aft of the fourth funnel], or a little further forward." If the wound came as far aft as BR 5, carrying the watertight bulkheads to D deck would not have saved the ship. If the watertight bulkheads were carried up to C deck the ship might have been saved provided that there was no damage in BR 4. As Wilding said, "I believe that no bulkhead arrangement possible forward would have saved the ship [in that instance], because of the red dotted line which I have drawn across [Condition B7] as the result of the earlier calculations."

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MODIFICATIONS TO OLYMPIC FOLLOWING THE TITANIC DISASTER

After the Titanic disaster, the Olympic underwent a major fit to increase her watertight integrity by increasing the number of major watertight compartments from 16 to 17, increasing the height and stiffening of 5 transverse watertight bulkheads (WTBs), and adding an inner skin to the hull in way of the machinery spaces. The intent was to be able to say that she would float with any group of six of the original major compartments flooded. To do that, a WTB was  also added abaft the engine room, between two pairs of electric dynamo engines, and bulkheads A, D, F, K, and N were carried as high as Bridge deck B. In addition, the orlop deck in Hold No. 1 was made watertight, and an inner skin fitted from bulkhead D back to bulkhead M giving added protection to all six boiler rooms and the reciprocating and turbine engine rooms.
This inner skin, of about 1/2 inch steel plate, was carried from the tank top to the bottom of Middle deck F, and was spaced 36 inches from the outer hull plating between deck F and Lower deck G, and 30 inches from the outer hull plating below deck G, the depth of the original web frames. It then widened out to 4 feet at the tank top. The space between the inner and outer skins was also divided by watertight subdivisions, both horizontally and vertically, between the major watertight bulkheads therby dividing the space into a series of watertight compartments. Because of the added inner skin, the central boiler in boiler room No. 5 had to be replaced with one of slightly smaller diameter (going from 15' 9'' to 13' 6''). At the right is a partial cross-sectional diagram showing the added inner skin. 

The arrangement and height of the major watertight bulkheads was such that there were five groups of 6 ajoining major compartments that could be flooded without danger of the ship sinking. This did not make the ship into a 6 compartment vessel, as some people have been led to believe, because it was not any group of six that could be flooded, just 5 particular groups of six. In addition to some bulkheads being raised, three others were reduced in height because they no longer needed to go as high as they did before. These were bulkheads L, M, and O which originally were carried watertight to D deck, now they were carried watertight only to E deck as was the new bulkhead added between original bulkheads M and N that separated the electric dynamos into two compartments of 2 engines each.
Besides the bulkhead modifications and the addition of an inner skin, changes were also made to the pumping arrangement on board with the addition of an extra line of piping. (For more details, please refer to fine books by Mark Chirnside, The 'Olympic' Class Ships: Olympic, Titanic & Britannic, and RMS Olympic: Titanic's Sister.)


These modifications, really a knee-jerk reaction to the Titanic disaster, came at a cost; not only in monitary terms but also in passenger comfort by interfering with some of their movements. It made for some difficulties in passengers getting about. 


Below is a diagram that shows the original watertight bulkhead arrangement of Olympic and Titanic as completed, and the arrangement for Olympic following her refit in early 1913, including the extent of the added inner skin including its watertight subdivisions (all outlined in dark blue) and the her watertight bulkheads (shown in red).