Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
--`` 1136495
SPILL OVERFLOW PREVENTION SYSTEM FOR TANKER VESSELS
The present invention relates to an auto-
matic system for preventing external cargo spillage from
tanker vessels resulting from the overflow of cargo from
the cargo compartments of the vessel during loading ~here-
of.
Presently~cargo~comprising fluid ohemical and
petroleum products~,~;such as,~for;examp~le, oil, is~loàded
into tanker vessels~by~means of~transfer hoses and aargo
pipelines which~are~coupled~to~lnléts communicative~with
the cargo compartments of~the~ves8el. It~sometimqs oc-
curs during loading;~or transfer~of cargo that the fluid
and chemical products~continue~to flow~after the~dompart-~
ments~are~full.~ As~a~rèsult,~càrgo~overflows through~ul~
lage~openings,~gas~vents~or;~other deck apertures communi-
15 ~ cative~with~the co~partm~nts~, over~the~dèck~of the~ves9el~
and~into~the water, ther by~causi ;a Jplll a d prod cin
water contamination,~atmospheric~pollution, as well as a
fire~ and~explos~io~hazard. ~
Cargo spill8 are~the n sult of a variety of t
20 ~ ~eaUses.~ One,~;for~èxample,~ls négligenQe~on the part of
personnel in charge~of loàding~the cargo compartments of
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the vessel. ~nother is a faulty loading valve, for
example, a leaky valve or a foreign substance wedged
under the valve gate. Others are a leaking line under
pressure within the cargo compartments; an increase,
without notice, of the vessel loading rate; and a broken
valve reach rod or other control segment during closing
of an inlet valve after a cargo compartment has been
filled. Such cargo overflows can cause significant pol-
lution of coastal waterways, particularly when the cargo
being loaded is crude oil. For example, depending upon
the size of the vessel and the flow rate of the cargo
during loading and the duration of the overflow before
it is discovered, anywhere from several barrels to
several thousand barrelo of oil may be lost from a single
cargo spill caused by an over10w.
Cargo tank overflll aontrol systems have been
devised to prevent overflows~from cargo compartments of a
- ~ tanker vessel during loading. High level alarms and con-
tinuous tank cargo level indicators, for example, are used
to monitor cargo~tank }~evels ln a vessel during loading.
While such devlces are helpful, they are sub~ect to mal-
functions, are dependent on human monitors, and do not
automatically prevent pollutlon, and these characteristics
make such devices unacaeptabIe for vessels carrying car-
goes such as crude oil having the potential of creating
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serious environmental pollution in coastal waterways andports in the event of spillage from the vessel caused by
an overflow during loading. Remotely-actuated, quick-
closing shut off valves have been used in such vessels to
help reduce overflows but it has been found that such
valves can create excessive surge pressures in the cargo
transfer hoses and pipelines used to load the vessel which
are great enough to rupture the hoses and line thereby re-
sulting in the spillage of cargo. Such valves are, more-
over, still dependent on human attention for effectiveoperation.
It is therefore an object of the present inven-
tion to provide an automatic spill overflow prevention
system for tanker vessels which overcomes the aforemen-
tioned disadvantages of prior tank fill indicators andoverflow handling systems and automatically prevents the
spillage of fluid chemical and petroleum products during
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~ loading operation:s~or cargo transfer operations in the
:~ vessel without~the danger of causing a rupture of the
20~ hoses and pipel~ines used to load the vessel or the bulk-
heads of the vessel.
It is also an ob~ect of the present invention
to provide an improved spill overflow prevention system
for tanker vessels which will reduce the pollution of the
natural environment, partlcularly the pollution of coastal
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and intercoastal waterway areas and ports.
These and other objects of the invention are
achieved in a tanker vessel for the transportation of
fluid chemical and petroleum products in water. The
vessel includes a hull comprising a bottom and sides, a
top deck, a plurality of watertight cargo compartments
disposed within the hull between the top deck and the hull
bottom for receiving the fluid chemical and petroleum pro-
ducts, and means coupled to the cargo compartments for
filling the compartments with the fluid chemical and
petroleum products. The improvement of the invention com-
prises longitudinally disposed trunk line means, branch
line means coupled at one end to the trunk line means and
at the other end to the cargo compartments, valve means
coupled to the branch line means~lntermediate the~ends
thereof for permitting the free flow of fluid chemical
and petroleum products from the cargo compartments to the
trunk line means through the branch line means, the branch
; line means being dimensioned so as to prevent overpressuri-
zation of the cargo compartments during the flow of fluid
chemical and petroleum products from the compartments to
the trunk line means, and retention tank means disposed in
the vessel and coupled to the trunk line means for receiv-
ing fluid chemical and petroleum products from the trunk
line means. Fluid chemical and petroleum products over-
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flowing from the cargo compartments during filling there-
of are directed from the cargo compartments through the
branch line means and the trunk line means to the reten-
tion tank means thereby preventing the spillage of the
fluid chemical and petroleum products externally of the
cargo compartments.
The improved spill overflow system of the
present invention will significantly reduce safety haz-
ards, cargo loss, and the pollution of coastal waterways
and ports caused by tank overflows during loading opera-
tions, transfers, discharge or cargo expansion in a tan-
ker vessel. This is achieved by utilizing a retention
tank, specifically one or more empty tanks, such as a
cofferdam, void space or ballast tank or other suitable
vessel space, as a plenum, and directing any overflows
from the cargo compartments into such a retention tank.
These and other novel features and advantages
of the present invention will be described in greater de-
tail in the following detailed description.
fn~the drawings, wherein similar reference
numerals denote similar elements throughout the several
views thereof:
FIGURE 1 is a perspeative view, partially in
cross-section, of a ta~ker vessel incorporating an im-
proved spill overflow prevention system constructed ac-
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cording to the present invention;
FIGURE 2 is a partial, cross-sectional view
of the improved spill overflow prevention system illus-
trated in FIGURE 1 showing the construction of the trunk
line, branch line and control valve of the system; and
FIGURE 3 is a partial, cross-sectional view
of the improved spill overflow prevention system illus-
trated in FIGURE 1 showing the construction of the reten-
tion tank.
1~ Referring now to the drawings, there is shown
a tanker vessel generally identified by the reference
numeral 10 which lncludes a hull comprising a bottom 11
and sides 12, a top or main deck 13, and a plurality of
watertight cargo compartments 14.~ The cargo compartments
are disposed within the hull between top deck 13 and hull
bottom 11 for receiving cargo comprising fluid ohemioal
and petroleum products, for example~,~ crude oil, from a
:~ land storage tank 15. Cargo expansion trunks 16 are cou-
~ ~.
~: pled to and open downwardly into each of oargo compart-
-20 ments 14. A cargo pipeline 17 i8: ooupled to each of the
: : cargo compartments 14 for filling the compartments with
cargo from land storage tank 15.
~:~. . Vessel 10 inoludes a longitudinal trunk line
~; 18, which can be dis~osed either above or below top deok
~25 13, and a plurality:of branch lines 19 which are coupled
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at one end to trunk line 18 and at the other end to
cargo expansion trunks 16. A plurality of valves 20,
which may comprise either non-return clapper valves,
weighted or spring-controlled to produce the required
back pressure for vapor venting, or positive type closure
valves, the latter preferably being butterfly-type valves,
are coupled to the branch lines 19 intermediate the ends
thereof for permitting the free flow of fluid chemical
and petroleum products, i.e., the liquid cargo, from cargo
expansion trunks 16 to trunk line 18 through branch lines
19. If non-return clapper valves are used, the valves
permit the free flow of the liquid cargo only from cargo
expansion trunks 16 to trunk line 18 through branch lines
19. A cargo retention tank 21, which may comprise either
a wing tank or a plurality of interconnected tanks of the
vessel, is coupled to trunk line 18 for receiving cargo
from the trunk line. An overflow pipe 22 is disposed with-
in the retention tank 21 for directing the cargo overflow
within the retention tank and has an enlarged opening 23
at one end thereof which is disposed below the end of
trunk line 18. The latter extends downwardly and opens
into the retention tank 21 ~ust below top deck 13. ~he en-
larged opening 23 of pipe 22 receives cargo overflow from
trunk line 18 and is spaced slightly apart from the end
of the trunk line in tank 21 in order to permit gases, for
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example, hydrocarbon gases and the like to escape from
the trunk line into the retention tank 21. A plurality
of apertures may also be disposed about the periphery of
opening 23 to permit gases to escape into retention tank
21. The retention tank is provided with an exhaust vent
24 which includes a flame screen 25 and a pressuretvacuum
relief valve 26 for venting gases from the retention tank
to the atmosphere. Gases are vented from the cargo
compartments 14 to the atmosphere during filling of the
compartments through trunk line 18 and branch lines 19 to
retention tank 21. A plurality of bypass lines 27 are
coupled to branch lines 19 intermediate the ends thereof
and in parallel relationship therewith, each including a
pressure/vacuum relief valve 28, which preferably com-
prises a closed type pressure/vacuum relief valve, coupled
.
to the bypass line intermediate its ends, for ventinggases from cargo~compartments 14 to retention tank 21
through trunk line l8 and branch lines 19 when valves 20
are positive type closure valves and are closed, i.e.,
during all operations on the vessel except when filling any
cargo compartments or tranæferring~cargo between the com-
partments. When valves 20 comprise non-return clapper
valves, the bypass lines 27 and valves 28 permit vacuum
relief in the cargo compartments 14. It should be noted
that the bypass lines 27 are not required if the vessel is
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3~i~95
retrofitted with the spill overflow prevention systemof the invention and already has an existing venting
system which is retained.
Branch lines l9 are dimensioned, i.e., have
a diameter which is large enough to prevent overpressuri-
zation of the cargo compartments dur1ng an overflow while
loading or transferring cargo. The term "overpressuriza-
tion" means a pressure build-up in the cargo compartments
due to the pumping of cargo into the compartments at high
pressure which would cause structural damage to the bulk-
heads of the vessel. Such a pressure build-up is re-
lieved by sizing the branch lines l9 so that the lines
have a diameter which is greater than the diameter of the
filling lines or plpes us-d to load the compartments to
such an extent that the pressure~in the cargo compartments
ls reduced to a~lével~below the~maximum the vess;el bulk-
~ heads can withatand before sustaining damage. It should
: ~ ~ be~noted that~both~trunk llne~18~and branch lines l9 may
comprise rectangular or~square-shaped ducts, or partially
20~ ~ cir~ular pipes,~as~we11 as~the~circular pipes illustrated
in the drawings, and aan be disposed either above or below
the deck of the vessel. The diameter of trunk line 18, as
a general rule, will always be;aonsiderably greater than
that of the branch~lines 19 and for that reason usually
is not a faotor in overpressurization of the aargo com-
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partments 14. If,however, for some reason a back pres-
sure were produced by the trunk line for example if the
trunk line had a diameter which was less than that of the
branch lines, this pressure would have to be considered
along with the pressure produced by the branch lines in
determining the dimensions of the lines which will keep
the pressure in the compartments 14 below the maximum al-
lowable overpressure.
: A line flow alarm 29 is coupled in series with
trunk line 18 for indiaating the flow of cargo in the trunk
line. In addition, retention tank 21 preferably comprises
a side compartment of vessel 10 in order to provide an ad-
ditional indication of the flow of cargo through the trunk
line and of an overflow by causing the vessel to heel over
slightly. This provides an:additional level of protection
: in the event that the~l:ine~flow~alarm fails to indicate
and/or crewmen working on the vessel are inattentive or are
not present and fail to detect an overflow from the com- :
partments through~the trunk line.~ ~
In operation,~in:the~:event that the volume of
cargo loaded into one~or more of the cargo compartments of
the vessel exaeeds the aapacity of the compartments and
:; overflows, the excess~aargo is direated through cargo ex-
: pansion trunk 16 and branch line 19 to the trunk line 18
and flows throuqh the trunk line into retention tank 21.
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If valves 20 comprise positive-type closure valves,
the valves are opened prior to commencem~nt of the loading
operation. If non-return clapper valves are used, the
valves will automatically open when an overflow occurs.
The flow through the trunk line 18 is indicated by the
flow alarm 29, which produces an audible and/or visible
alarm. Cargo entering the retention tank is received by
enlarged opening 23 of overflow pipe 22 and is directed by
the pipe within the tank to the tank bottom. Gases pre-
sent in cargo compartments 14, for example, hydrocarbongases produced by petroleum products, are expelled from
the compartments during loading or cargo transfer and
flow through branch lines 19 into trunk line 18 and es-
cape from the end of the trunk line in retention tank 21.
The gases are then vented under pressure to the atmosphere
through exhaust vent 24. The exhaust vent 24 is prefer-
ably designed so that it terminates at its open upper end
at a level above the vessel's deck which is well clear of
personnel areas and any hazard of ignition on the vessel.
It should be noted that a closed tank loading system is re-
quired during loading or transfer operation- on the vessel.
This system can be either an automatic or manual closed
ullage system or a simple glass visor having an internal
wiper device fitted in eaoh ullage opening. The spill
overflow system of the present invention may also be used
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1136495
12
for bunker tanks, chemic,al tanks, etc., to prevent over-
flow loss and hazard in the same manner as with cargo
compartments.
In the foregoing specification, the invention
has been described with reference to specific exemplary
embodiments thereof. It will, however, be evident that
various modifications and changes may be made thereunto
without departing from the broader spirit and scope of the
invention as set forth in the appended claims.~ The speci-
fication and drawings are, aocordingly, to~be~regarded ln
;~ ~ an illustrative`rather than in a~restrictive sense.
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