Improvements in the Means and Appliances for Temporarily Decreasing the Draft of Vessels.
Year: 1894

page_text: Date of Application, 29th June, 1894
Complete Specification Left, 29th Mar., 1895-Accepted, 29th June, 1895
Improvements in the Means and Appliances for Temporarily
Decreasing the Draft of Vessels.
We WILLIAM PIRRIE, Marine Superintendent, and NORMAN PIRRIE, Marine
Engineer, both of No. 9 Sanderson Road in the City and County of Newcastle
upon Tyne do hereby declare the nature of this invention to be as follows:-
This invention relates to the means and appliances for temporarily decreasing the
draft of vessels for the purpose of enabling them to cross a bar or shoal or of
entering or leaving a dock (in the case of steamers with the use of their own engines)
without the necessity of having to lighten by the discharge of a portion of their
cargo, or non shipment of a complete cargo, or of waiting till spring tides.
We purpose to accomplish this in the following manner.
We construct one or more metallic pontoons or buoyancy chambers for each side
of the vessel, starboard and port. These pontoons or chambers are attached
together by wire ropes hereafter called the "slings," or other suitable means,
passing under the vessel's bottom.
By having a number of pontoons we obtain flexibility so that the pontoons may
conform closely to the shape of the vessels' lines and not occupy much width, but
the use of a single pontoon strong and of sufficient buoyancy on each side of the
vessel and which will bear against the comparatively straight sides of the vessel,
will answer equally as well, where width is not an object.
Each pontoon is in communication with a chamber in which air or other suitable
medium is stored under pressure during the period the appliance is idle. These
compression chambers may form part of the pontoon or otherwise as may be most
convenient.
When the buoyancy chambers have been sunk to the required depth by the
admission of water, and the slings are underneath the vessels bottom, communication
is opened between the pontoons and the storage chambers, whereupon the
compressed air or other medium will drive out the water from the pontoons through
openings for the purpose; the buoyancy thus gained will raise them in the water,
carrying the vessel with them by means of the slings under her bottom; or the air
may be forced direct to the buoyancy chambers from the air pumps without being
previously stored or the requisite buoyancy may be obtained by simply pumping
out the water in the usual method.
To each pontoon is attached an iron strain bar to which the several slings are
This
attached and through which the strains are transmitted to the pontoon.
strain bar may be hollow and used as the chamber for storage of the compressed
air, and also for additional buoyancy purposes.
The strain bar may be constructed to revolve on its own axis in the manner of a
winch barrel, or may have drums revolving on it for the purpose of tightening up
the slings in a quick and convenient manner and also to sink further down the
pontoon so that when the vessel is raised to the required height the upper surface
of the pontoons may not rise above the surface of the water-"Grips" or
"compressors for holding the slings may be used to assist the strain bar. Other
well known mechanical means may be used for tightening and heaving in the
slings for instance an engine or series of rams working by the compressed air.
"
Fenders of any suitable material, pneumatic or other principle are attached to
the side of the pontoons.

page_text: When single pontoons are used they may have propelling and other machinery
and engines or pumps fixed on board and be navigable and independent in their
working.
This system of floating lifts may be also used for lifting the sterns of steamers
to allow of the propeller being shifted or repaired without the expense and necessity
of docking or for lifting the bow of a vessel in event of damage by collision.
K. HADDAN,
Agent for the Applicants.
Improvements in the Means and Appliances for Temporarily
Decreasing the Draft of Vessels.
We, WILLIAM PIRRIE, Marine Superintendent, and NORMAN PIRRIE, Marine
Engineer, both of 9 Sanderson Road, in the City of Newcastle-on-Tyne and
County of Northumberland, 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 :-
This invention relates to the means and appliances for temporarily decreasing
the draft of vessels for the purpose of enabling them to move at a diminished draft,
for instance in order to cross a bar or shoal or of entering or leaving a dock (in
the case of steamers with the use of their own engines) without the necessity of
having to lighten by the discharge of a portion of their cargo or non-shipment of a
complete cargo or of waiting till spring tides.
We purpose to accomplish this in the following manner :-
B
We construct one or more metallic pontoons or buoyancy chambers for each side
of the vessel, starboard and port. These pontoons or chambers are attached
together by wire ropes hereinafter called the slings, or other suitable means, passing
under the bottom of the vessel to be lifted.
When the buoyancy chambers have been sunk to the required depth by the
admission of water, and the slings are underneath the vessel's bottom, and have
been automatically brought to the same tension as hereinafter described, the requisite
buoyancy is obtained by simply pumping out the water from the buoyancy
chambers.
Fenders of any suitable material, pneumatic or other principle, are attached to the
side of the pontoons.
When single pontoons are used they may have propelling and other machinery
and engines or pumps fixed on board and be navigable and independent in their
working.
This system of floating lifts may also be used for lifting the sterns of steamers to
allow of the propeller being shifted or repaired without the expense and necessity
of docking, or for lifting the bow of a vessel in event of damage by collision.
In lifting ships for the purpose of temporarily decreasing their draught of water
to allow them to cross a bar or shoal as distinguished from lifting ships from
the bottom of the sea, commonly called "wreck raising," it is necessary to form
a cradle either of solid formation, as is done in the case of floating docks where the
ship is raised entirely out of the water, or of flexible formation such as
hereinafter described; the object being that the bottom of the ship should not
suffer any injury or undue strain in the act of lifting, which is so commonly the case
in wreck raising where the chief and only object to be gained is to recover the
vessel from the depths of the sea and where any such damage is of sinall importance
in view of the end to be attained.
For this purpose therefore we construct and arrange the aforesaid slings so that
they form a cradle of broad bands of flexible steel wire rope each band sufficiently

page_text: wide to always cover one of the frames of the ship. The ends of these bands (hereafter
called the slings) are led up to the pontoon or camel barge placed on each side of
the ship, these pontoons or camels being constructed as described with reference
to the drawings.
In attaching the slings to each pontoon they are led up through the tubes to the
drums or winches placed on the deck of the pontoons.
Owing to the shape of a vessels bottom, the length of each sling will be different
each becoming less as the ends of the ship are approached; for this reason therefore
each and every drum or winch must have an independent action, but at the same
time act simultaneously and with exactly the same power, for the slightest
difference in length-or-strain-on-any-one-sling-would either-cause damage-to-the
ship at the point of contact or would throw such an extra strain on the gear as to
carry same away.
For this reason we prefer to use hydraulic power for tightening in the slings as
being more under control and as maintaining a steady and uniform pressure, although
with great care and trouble other well known means may be used. We therefore
attach to each winch or drum a three cylinder hydraulic engine the whole working
off the one supply or communication pipe from the hydraulic pumps which have
relief valves loaded to the required strain to which it is desired that the slings
shall be hove tant. The hydraulic gear of the winches is set in motion and
controlled by one valve worked by the captain or other officer from the bridge, or
other convenient position.
To relieve the hydraulic winches of the heavy strain which they have to bear
when lifting the ship, compressors are fitted on underneath each winch in the
following manner. On special beams (which are hereafter described) two
strong solid iron bed plates are secured between which the flat sling passes
before being led round the winch. The faces of these bed plates are inclined
to cach other at a slight angle and into this space a steel wedge is carefully
fitted. This wedge is attached to one end of a lever and the other end of the
lever is connected to an hydraulic ram, so that when this ram is set in motion the
wedge is forced close home thereby compressing the flat wire sling between it and
one of the faces of the bed-plate. All these hydraulic rams are worked from the
same pipe conveying the hydraulic power, the controlling valve of which is placed
on the bridge beside the controlling valve of the hydraulic winches, so that the
entire set of compressors can be closed or secured simultaneously. Other well
known means of gripping or securing the slings may be used if desired.
Before coming alongside the ship the pontoons are steered apart and sufficient
slack is payed out on the slings to allow of the bight passing freely under the
vessel's keel as the pontoons steam up, one on each side.
When the pontoons have been placed amidships alongside of the vessel to be
lifted, the controlling valve being opened from the bridge, causes each one of the
winches to haul in the slack of the sling attached to it until it has become
taut and as the power of each winch is the same, the strain or pull on each
sling will be the same. When all have ceased working and before any strain is
released the hydraulic cylinders working the wedges of the grips or compressors
for holding the slings are put in motion, and being also worked and controlled
by a single valve from the bridge are therefore moved simultaneously, the result
being that each and all of the slings are gripped or locked with the same strain or
tension on each, the whole forming a uniform level cradle on which the ship may be
lifted without injury.
To lift the vessel, the water chambers in each of the pontoons are emptied, when
a lifting power will be obtained equal to the water displaced.
The water chambers may be emptied by means of compressed air or by means of
pumps of various kinds. We prefer centrifugal pumps which may be worked from
the main engines or by independent engines attached to each pump, the size and
number of pumps being regulated by the speed at which it is desired the lift shall
work.

page_text: When lifted, the vessel may be moved across the bar or shoal; if it be a
steamship by the use of her own engines and propeller having the assistance of the
engines of the lifts (one at each side) for steering and guiding in narrow waters as
also of relieving the ship of any resistance due to the resistance of the lifts
themselves. In the case of a sailing vessel the lifts will supply the necessary
propelling power dispensing with the necessity for a tug in most cases.
The pontoons being entirely self contained, navigable and seaworthy, can be
taken out to sea to lift ships over a bar outside the harbour, or they may be moved
from port to port as their services may be required.
In addition to the ordinary rubbing fenders or wooden belting on the sides of the
pontoons, elastic or resilient fenders are fitted to the sides of the pontoons
projecting beyond the wooden belting. These resilient fenders are preferably
strong rubber tubes charged with air and fitted with relief valves, the object being
that when coming alongside a vessel for the purpose of attachment, should there be
any sea to cause either the vessels or pontoons to roll, no damage may be sustained
by either the ship or pontoons, and that as the full strain of the lifting power
being exerted and the pontoons are pressing against the sides of the vessel, the
pneumatic fenders will collapse and lie inside of the wooden belting. To further
obviate any damage by rolling the top sides of the pontoons are constructed with a
considerable round as shown in the drawing of the cross section; the rails are also
constructed to fall down inboard if necessary.
In the design and construction of the pontoons, special beams are fitted with a
considerable round (or the frames may be carried across in this form) for the purpose
of carrying the compressors, which are specially placed below the drums or winches
which heave in the slings. This is the strongest form of construction for the
purpose and has the advantage of lowering the point of suspension of the slings and
thereby increasing the stability of the pontoons.
In lifting vessels for the purpose of diminishing their draught to allow of their
erossing a bar or shoal, the time occupied in the operation becomes a matter of the
utmost importance.
In many cases there may be only sufficient depth of water over the bar or shoal
to allow of vessels being taken across during the period of high water and there
may be several vessels desiring to cross at the same tide. Also should there be any
sea on, the time during which the lifts have to be alongside during the process of
attachment must be as short as possible to prevent opportunity for damage,
notwithstanding the precautions taken to obviate same.
To effect this, the lifts have been designed and constructed so that they may be
quickly attached to the vessel in a rough and ready manner without requiring any
accurate adjustments of trim or position; and that once in position the whole of the
slings can be tightened in and secured simultaneously, the hydraulic gear adjusting
each to the same strain automatically, thus allowing longer time for the discharge
of the water from the chambers, which latter is done as quickly as possible whereby
the pontoons become so securely bound to the vessel as to act and move only
conjointly with her.
In the annexed sheet of drawings;-
Fig. 1 is an elevation of a pontoon barge for use in lifting ships.
Fig. 2 is a plan of the upper deck.
Fig. 3 is a section thereof amidships (on an enlarged scale) looking forward,
showing elevation of lifting gear.
Fig. 4 is a side elevation of lifting gear.
Fig. 5 is a plan of lifting gear.
Fig. 6 is a section amidships showing a ship and pontoons in position lifting the
same; in this figure the dotted line shows the draught of ship when loaded, the full
water line shows the draught when lifted by pontoons.
A is a water space or water spaces connected by suitable pipes and valves with
Bis
the centrifugal or other pump at C, and provided with inlet and relief valves.
the boiler, D engine room, E officers' quarters, F crews quarters, G space or

page_text: chamber for stores, H winches, each consisting of casing, bearings and drum J worked
through gearing by a three cylinder or other hydraulic or air engine K fitted with
controlling valves. L is the sling led through a tube or passage way S in the
pontoon to each winch over drum J. M is a hydraulic cylinder for working
through level M a grip or compressor wedge M² for holding the sling L and thus
relieving the strain on the winch, while the ship is being lifted and is held lifted.
The slings L are each of sufficient width to always cover one of the frames of the
ship thereby bringing the strain or weight on the slings always over the ship frames.
N, N, are hardwood rubbing rails or fenders running nearly the whole length of
the pontoon. P is a compressible-fender shown on the drawing as a tube in one
or more lengths made of indiarubber or other suitable material and charged with
compressed air. On the pipe Q connecting these fenders P with the air
compressing apparatus, a relief valve or valves is fitted; the tubes P may be of
any suitable shape. R is a space at the bottom of the pontoon for water ballast.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, we declare that what we
clain is:-
In means for enabling steamships and other vessels to move at a diminished
draught,
1. The combination of two or more pontoons with a plurality of slings extending
from the one to the other, means for severally and simultaneously tightening said
slings to an equal tension beneath the hull of a vessel between said pontoons, means
for gripping or locking said slings when tightened and means for thereupon
displacing water from the chamber or chambers of said pontoons whereby to
lighten their draught and lift and support the vessel between them for the purpose
set forth.
2. The combination of the pontoons with slings for supporting and lightening
the draught of vessels and means for simultaneously tightening to an equal
tension and securing said slings together, with a propeller or propellers and engines
whereby said pontoons may be navigated in conjunction with or separate from said
vessels.
3. The combination of a pontoon shaped as illustrated in cross section with a
series of hydraulic winches along the deck thereof, slings Land passage ways for
said slings extending obliquely to the lower edge of the vertical side of the pontoon.
for affording support to a vessel in immediate continuation of that afforded by the
side of the pontoon.
4. A pontoon having water ballast space R, spaces or chambers A, A, means for
filling said spaces A, A, with water and displacing said water therefrom, slings L,.
means for simultaneously and equally tightening said slings L, and grippers such
as M2 for securing said slings, the whole for the purpose herein described.
Dated this 28th day of March 1895.
R. HADDAN,
Of the Firm of Herbert Haddan & Co.,
18, Buckingham Street, Strand, London, W.C., Agent for the Applicants.