Improvements in the Compartments of Merchant Ships.
Year: 1896

page_text: C
Date of Application, 26th June, 1896
1007
CLL
1007
PROVISIONAL SPECIFICATION.
Improvements in the Compartments of Merchant Ships.
FREDERICK EDWARD SHEAN 360 Upland Road, East Dulwich, London, S.E.,
Engineer, do hereby declare the nature of this invention to be as follows:-
Firstly, and chiefly, as relates to affording a ship immunity from sinking, as a
result of severe injury to her Bottom, or her Bilge.
This is effected by covering all main compartments, possible, by a crown, or
Arched Deck.
The said crown, or Arched Deck springs from the sides of the ship, and rises
up to, or above the Load Line level, and is capable of standing an internal pressure,
up to about 12lbs. pr. sq. inch.
This arched "Deck" is for the purpose of sustaining air pressure below it.
Let it be assumed that, in the hill of a ship, in which there are no compartments,
an arched Deck runs from the fore end, to the after end; or, from stem to stern.
(a) If the "Deck" be air-tight, and sufficiently strong, the ship's bottom may be
opened, and the water allowed free admission.
The influx will cease, when the weight of the ship is taken by the arched "Deck"
compressing the air, between it and the internal surface.
And, if the ship have sufficient freeboard to enable her to sink to the depth
necessary to transfer her weight thus, from the outside, below the bottom, to the
inside, below the deck, she can sink no further.
(b) Whatever the internal pressure may be when this condition of rest obtains,
it is clear, that, if the ship's bottom were 25 feet below the surface, (before she
began to sink, by influx through the bottom,) and the corresponding pressure (of
11-1 lbs. per sq. inch) of air were maintained below the Deck; then the bottom
might have been opened to the sea, without the entry of any water whatever.
As it is with the whole ship, (as above, assumed) so it is with the parts, or
compartments of the actual one; in that (a), when closed at the top, and open to
the sea, at the bottom, they cannot "fill," beyond a certain height;
And, (b), when containing air-pressure, equal to that of the water immediately
below their bottoms, they may be open to the sea without water entering them,
through such openings at the bottoms;
When under atmospheric pressure (a). If injury, or opening occur, above the
Bottom, as, some distance up the Bilge, the injured, or opened compartment "fills,"
until the air above the internal water surface is compressed to the difference of
pressure between the internal and external columns, and the Buoyancy of the com-
partment is, to that extent lost.
When, under Buoyancy pressure, i.e., pressure equal to that exerted on the
Bottom, by the sea, i.e., with the internal pressure equal to the sea pressure, on the
Bottom of the ship, (b) if the same opening occur the compartment "fills" to
the highest part of the opening, which forms the air-outlet, and the Buoyancy of the
compartment is only to that extent, lost.
With such compartments, sustaining the proper pressure, no injury to the Bottom
could sink a ship, nor, even disable her (provided that the open compartment, con-

page_text: taining the engines, and boilers, remains intact,) and, injury to the Bilge only
lessens that security in proportion to the height of such injury, (i.e., opening) above
the ship's Bottom.
A ship, having such main compartments, closed, and pumped up, with air, to the
Buoyancy pressure, before leaving port; and, that pressure maintained, during her
passage, may have the Bottom of every such main compartment, broken into, and
open to the sea; and every main water-tight Bulkhead, except the two, enclosing
the engine and boiler compartment,-also broken through, without seriously
affecting her Buoyancy, or her ability to continue her passage,-Provided that, the
uncovered engine and boiler compartment remains intact.
Secondly As relates to the effect of collision, in a ship fitted with an arched
pressure Deck," as previously described.
In this case, the arched deck would be cut into; and the compartment flooded.
But where there is sufficient breadth, the effect may be greatly diminished, by
bringing a light, and curved, bulkhead from each side of the centre of the arched
deck, down to the bottom; the bellying, or bulging, being towards the sides of the
ship, and the fore, and after ends fastened to their respective transverse bulkheads,
thus dividing each main compartment into three sub-compartments; the middle one
of which, like the main compartment, is capable of withstanding a pressure
of 12 lbs. pr. sq. inch.
This middle sub-compartment, is, as relates to collision, a reserve of buoyancy;
and the distance of its enceinte (bellying; bulging)-from either side of the ship
is dictated by the probable penetration of a ship's bow.
The two side compartments are collision compartments.
When proceeding under buoyancy pressure, the sub-compartments are fed, by the
air first entering the side, or collision ones; and, passing, under check-valves, into
the reserve one; the pressure in all three compartments, being practically the same.
If collision occur, and either side be crushed into; the air, from that side com-
partment, at once escapes; and, the supply valves on that side of the Reserve com-
partment remain closed, whilst the Reserve, and the opposite collision compartment
retain their pressure, as before;
But, the arched bulkhead which forms the side of the Reserve compartment, next
to the flooded one having taken the duty of the ship's side, has now, the buoyancy
pressure within, acting against the sea pressure without it.
Dated this 26th June. 1896.
FREDK. SHEAN.
Improvements in the Compartments of Merchant Ships.
FREDERICK, EDWARD, SHEAN, 360 Upland Road, London, S.E. Engineer, do
hereby declare the nature of this invention and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement :-
(1) Firstly, and chiefly, as relates to affording a ship immunity from sinking, as a
result of severe injury to her bottom, or her bilge.
(2) This is effected by covering all main compartments, by a crown, or arched
deck, which springs from the sides of the ship, and may rise up to the load-line
level, and, is capable of standing internal pressure, up to about 12 lbs. per square
inch.
(3) The "crown" is for the purpose of sustaining air-pressure below it, and is
formed, and built in such manner, and of such strength as shall enable it to with:
stand a pressure below it, equal, per sq. inch, to that exerted by the sea, upon the
bottom of the ship, when at her load draught.

page_text: (4) Therefore, its form, in vertical cross-section, would be, preferably, a circular
are; and its strength equal to that of the bottom.
(5) The object, and purpose of the said crown, and the air pressure thereunder, is
to limit, or prevent the sinking of the ship-due to any, or, all of her compartments
being broken open to the sea, by transferring the sustaining, or buoyancy pressure,
from the outside of the ship, below the bottom, to the inside, below the crown,
under either of the following conditions, prior to the bottom being opened to the sea.
(6) A; Atmospheric pressure, below the crown.
B; Air pressure below the crown, equal, per sq. inch to the pressure exerted by
the sea, upon the ship's bottom, when at load draught.
EXAMPLE;
(7) A rectangular sectional vessel, Fig. 1, having no partitions, or bulkheads, has
a draught of water, of 25 ft.
(8) A flat crown deck a, running from side to side, and from end to end, divides
the vessel, near the load line level, into two portions, upper, and lower.
(9) If the said crown, a, be air-tight, and sufficiently strong, the vessel's bottom
may be opened, and the sea allowed free admission to the hull, below the crown, a.
(10) The influx will cease when the weight of the vessel is borne, by the crown, a,
compressing the Internal volume of air between the Internal Surface, w, (i.e., the
level of the water within the vessel) and the said crown itself.
(11) And, if the vessel have sufficient freeboard, f, to enable it to sink to the
depth necessary to transfer ifs weight, thus, from the outside, below its bottom, to
the inside, below the crown, a, it can sink no further.
(12) The transference of the weight, from the bottom to the crown, produces
pressure below the latter, equal, pr. sq. inch, to that exerted by the sea, upon the
vessel's bottom, at 25 ft. depth below the surface, and that is 111 lbs. pr. sq. inch.
(13) (At the load line section, the excess of the outer, above the inner area-due
to the thickness of the skin,-would require the internal pressure to be more; and
the sinking of the vessel, from its original draught, d, Fig. 1 to the new draught,
d, Fig. 2, would, by lessening the weight borne by the internal pressure, require it
to be less than that given above).
(14) Such details, however, do not materially, affect the position.

page_text: Fig. 6. (Buoyancy pressure below crown.)
All compartiments from stem to boiler room broken into one. EB
intact.
Fig. 7. (Buoyancy pressure below crown.)
Torn open, from end to end.
(15) The rising of the Internal Surface, w, is limited by the pressure of the air
between it and the crown.
(16) The crown a, being parallel to the bottom, b; the space, a a bb, being at
any point, P, of rectangular section; and the pressure of air, below the crown, a,
being inversely as its volume.
(17) If the Internal Surface rise to M, (midway between the crown, a, and the
bottom, b-i.e., 12 ft. above the bottom-it compresses the original volume of air,
below the crown, into half that volume; and, therefore, to double its pressure; or,
to 15 lbs. per sq. inch.
(18) But, the sustaining pressure, exerted by the sea, under the bottom, is
11.1 lbs. pr. sq. inch, which, also, must be the pressure exerted by the air, under the
crown, nearly (Par. 13) and the height to which the Internal Surface, w, can rise,
above the bottom, b, is about 8 feet.
(A) (19) With the entrance of the water, and the subsiding of the vessel, a new
force is brought into operation.
(20) The freeboard, f, in (conjunction with the crown, a), now represents true
reserve of buoyancy; and, as it diminishes, the reserve of buoyancy which it repre-
sents, actively operates, as a new displacement-to arrest submergence.
(B) (21) Whatever the internal air pressure may be, when the condition of rest
obtains, it is clear that, as the vessel's bottom is 25 ft. below the sea-surface, if
there were an internal pressure of air, or other gas, equal, to the pressure of the
sea upon her bottom, (i.e., 11.1 lbs. per sq. inch) the bottom might have been
opened to the sea, without the entry of any water, whatever.
(22) As with the whole vessel, as above assumed, Figs. 1 & 2, so it is, generally,
with the parts, or compartments of the actual ship; in that, when closed to the air,
at the top; and open to the sea, at the bottom, they cannot "fill" above a certain
height, which will be proportionate to the fineness of their lower portions.
(A) (23) When under atmospheric pressure, if opening occur above the bottom,
as, for example, some distance up the bilge,o, Figs. 4 & 6-the opened compart-
ment "fills," until the air, above the Internal Surface, is compressed to the
difference of pressure between the internal, and external coluinns; and, the
buoyancy of the compartment is, to that extent, lost.
(24) Therefore a ship-Fig. 3, with sufficient freeboard, f, to include a volume
equal to her original displacement; and having all possible main compartments so
crowded, may, so long as the power compartment, E B, be intact have all others
torn open to the sea, and to each other, without either foundering, or, being
rendered helpless.
(25) If the freeboard, f, include a volume greater than the original displacement;
then, with the same damage as above, and also, the escape of the air, by leakage,
the ship still floats, for she now rests, wholly upon her second, or reserve displace-
ment Fig. 5.
(26) If, in either case, the power compartment, E B, also, be cut through,-lower
parts of bulkheads included; thus, opening the bottom, by one continuous rent,
from end to end; the loss of the support of that compartment, will lessen the
reduced buoyancy in proportion to the relative volumes of their displacement.
(27) Condition A, then, requires a certain freeboard, and reserve of buoyancy,
and where the margin is narrow, or insufficient, the maintenance of the Internal
pressure, is vital.
(28) The possibility of air leakage from below the crown, is therefore provided
against by an air pump, placed in a position, above the sea level, and readily

page_text: coupled to some auxiliary engine, ordinarily used for some other purpose; but,
preferably, one taking its steam from an auxiliary boiler, also above the sea level.
(29) The air-pump requires a delivery pipe to each coinpartment, and a pressure
gauge upon each delivery.
(30) If the extent of the air leakage be beyond the capacity of the pump, then,
in the case of insufficient freeboard (Par. 27) it is merely a question of time, as the
ship must sink.
(31) But, even in this case, there is some time; for, sudden disappearance-which
would inevitably be the fate of any existing ship, under similar conditions of injury
-is impossible here.
(32) Should there be no leakage of air, or such only, as it is well within the
capacity of the pump to make good, the Internal pressure increases, and the ship
slowly rises.
(33) The extent to which she can so rise, is limited by the depression of the
Internal Surfaces, allowing the air to escape, through the opening.
(34) When the said opening is in the bottom, and the power compartment is
intact, the ship may, under continual pumping of air, regain her original buoyancy.
(35) When this occurs, the Internal pressure (air) is equal, per sq. inch, to the
pressure of the sea upon the ship's bottom, which is the buoyancy pressure; or,
Condition B.
(36) When compartments contain internal pressure equal to that of the sea
immediately below them, their bottoms may be open to the sea, without the
possibility of any water entering them.
(37) Under this buoyancy-pressure, if an opening occur some distance up the
bilge, o. Fig. 4-the compartment "fills" to the highest part of the opening,
which forms the air outlet; and the buoyancy of the compartment is only to that
extent reduced, (Par. 23).
(38) With such crowned compartments, a, sustaining the buoyancy pressuro, no
injury to the bottom can sink a ship; nor, if the power compartment E B remain
intact, even disable her; and, injury to the bilge, only lessens that security, in pro-
portion to its height above the bottom, b.
(39) A. ship, so built, having her compartments closed, before leaving port, may
have them pressed by air-pumps, on the dock-side, or in a tug, alongside her.
(40) Then, with means of maintaining the pressure, if necessary (Par. 28) she
may-so long as the power compartiment is intact-have the bottoms of all other
compartments torn open to the sea, and to each other, without appreciably
affecting her buoyancy, or her ability to continue on her passage. Fig. 6.
(41) Should the power compartment also, be flooded, the executive function of the
ship is gone-she is iuert, and helpless; but, still afloat. Fig. 7.
(42) As the excessive opening along the whole length of the bottom does not
necessarily sink the ship, neither can similar opening, in any part of that length
do so.
(43) There is possibility of fatal injury under either of the conditions, A, or B,
viz. when the side is opened, all along, at, or above its junction with the crown-a
contingency exceedingly remote.
(44) The basis of the strength of the crown (Par. 4) is in the hull and bulkheads.
Example: If a ship be 50 feet beam; her compartments, below the crown, 50 ft.
between bulkheads; and (independently of her framing) her sides and bulkheads be
of one inch plating, the two sides and one bulkhead contain a sectional area
of 1800 sq. inches.
Taking the joints as 50 per cent. of the strength of the plate, the latter is
equivalent to 900 sq. inches, which, at 5 tons per sq. inch gives a tensile strength
of 4500 tons.
(45) But, the pressure below the crown, (being, say 12 lbs. per sq. inch, upon an

page_text: -
area of 502, 2500 sq. feet) is 1928 tons. 1928 2.14 tons per sq. inch; which
may be still further reduced by shortening the distance between bulkheads; or,
the addition of partial bulkheads, diaphragms, or curtains (for carrying longitudinal
girders).
(46) The load line may be viewed as the maximum height of the crown, above the
bottom. A half, or two thirds of that height may be more convenient.
(47) With the duplicate displacement, and buoyancy, the ship has two "lives."
(48) Under Condition B, the compartments may be entered by air-locks; and,
no leakage of water could occur.
(49) Ships with protective decks, and high freeboard may be adapted to this
method.
(50) In view of the roll of disaster during the past forty years; the increasing
size, and competitive speeds of Ocean passenger steamers call for the maximum of
security.
(51) The object, therefore, is to make sudden sinking impossible, and the
possibility of sinking, in any case, very remote.
(52) 2ly, as relates to collision. Here, generally, the crown deck would afford no
immunity from the flooding of the compartments.
(53) But, in a ship of ample beam-say 45 ft. and upwards, and under condition B,
-the result of collision, as relates to the quantity of water admitted, may be largely
reduced, by a curved bulkhead x, Fig. 3, upon each side of the middle line, and
running from the crown to the bottom, the bulging being towards the sides of the
ship, and the fore and after ends fastened to the transverse bulkheads; thus
dividing each main compartment into three sub-compartments, the middle one of
which, like the whole main compartment, is capable of bearing an internal pressure
per sq. inch, equal to that exerted by the sea, on the ship's bottom.
(54) In the event of collision, on one side of the ship, the said middle sub-
compartment, and the opposite side sub-compartment, form a reserve of buoyancy,
as they would there were no internal pressure.
(55) The distance of the middle sub-compartment from either side of the ship, is
dictated by the probable penetration of a ship's bow-the greater that distance is,
the greater being the chance of the middle sub-compartment remaining intact, but
the less the reserve when the ship's side is struck, and opened. The two sides, or
wing sub-compartments, are primarily collision compartments.
(56) When under buoyancy pressure, the compartments are fed by the air first
entering the side, or collision sub-compartments, and passing, under check-valves,
into the middle sub-compartment, the pressure in all three, being, practically the
same.
(57) If collision occur, and either side be crushed into, the air, from that side
escapes, and the check-valve on that side, remains closed.
(58) But, the middle, and the opposite collision sub-compartment retain their
pressure, as before.
(59) And, the curved bulkhead x which forms the side of the middle sub-
compartment, next to the flooded one, having taken the function of the ship's side
(where it has been opened) has now, the buoyancy (air) pressure upou its inner, or
concave side, and the sea pressure upon its outer, or convex side.
(60) Having now particularly described, and ascertained the the nature of my
said Invention, and in what manner the same is to be performed, I declare that what
I claim is
(61) 1. Covering main compartments of ships by an air-tight crown-deck,
running from side to side, and from end to end of such compartments;
(62) The said crown deck being built in such manner, and of such strength as
shall enable it to sustain, below it a pressure per sq. inch, equal to that of the sea
upon the bottom of the ship, when at load draught."
(63) The object, and purposes of the said crown-deck, is to limit, or prevent the

page_text: sinking of the ship-due to any opening, below the water-by transferring the
sustaining, or buoyancy pressure, from the sea, outside the bottom of the opened
compartment, to the air inside, under the crown of that compartment.
(64) 2. Pumping air into any such compartment, for the purpose, either, of
expelling the sea water, or preventing its admission.
Dated this 24th day of June A D 1897