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Патент USA US3024627

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March 13, 1962
w. 1.. MILLER
3,024,61 7
REDUCTION OF TANK CORROSION
Filed June 16, 1959
IN VEN TOR.
M44 727? L Mauve
BY
‘arena thee
3,?24,6l7
Patented Mar. 13, 1962
2
3,024,617
REDUCTION OF TANK CORROSION
Walter L. Miller, 160 Hendrickson Ave, Lynbrook, FLY.
Filed June 16, 1959, Ser. No. 820,831
17 Claims. (Ci. 62—54)
(Granted under Title 35, US. Code (1952), see. 266)
of water, but it should be cooled by the unit 4 to a tem
perature which will cause the heat exchange element 3 to
cool the adjacent air or ambient vapors to about 50° F.
or lower. Frosting of the element 3 may be prevented
by using large cooling surfaces of element 3 at tempera
tures above freezing temperatures, or by periodic de
frosting of the element 3 whenever it is necessary to use
temperatures below freezing for e?icient cooling.
The invention described herein may be manufactured
A tray 8 is disposed in the tank 1 beneath the heat ex
and used by or for the Government of the United States
of America for governmental purposes without the pay 10 change element 3 to catch ambient vapors condensed by
ment of any royalties thereon or therefor.
’
This invention relates to the reduction in the corrosion
of walls of large tanks that are used to store or convey
the element 3 and dropping therefrom. The element 3
is exposed for contact by ambient vapors in the upper part
of the tank, and the condensation of some of the ambient
vapors will set up convection currents that cause more
vaporizable cargo liquids which are immiscible with water.
Various procedures have been used heretofore to re 15 ambient vapors to come in contact with the element 3
and be condensed thereby. A sump 0r casing 9 is dis
duce corrosion of the walls of large tanks, particularly in
posed in the tank and supported in the upper air space
tanker ships, by drying air or gas and then circulating it
thereof in any suitable manner such as by suspending it
through the air spaces of the cargo tanks. This requires
from the top wall 2 of the tank.
means for cleaning and drying the air or gas, and elabo
A pipe 10 connects the tray 8 to the sump 9' and drains
rate circulating equipment. Very large volumes of air or 20
into the sump by gravity the condensation from element
gas must be circulated in order to remove moisture from
3 that is collected in tray 8. The sump has an over?ow
initially wet walls, bottoms and seepage. Another attempt
passage or pipe 11 in its side wall intermediate of its top
to solve this problem was to place drying agents in closed
and bottom edges, and no higher than the opening of pipe
spaces, but such agents must, at ‘frequent intervals, either
be replaced or regenerated. Drying agents are impracti 25 10 at the tray. The condensed vapors of water and of
the cargo liquid stored in the tank, when deposited in the
cal in large spaces which must be used in carrying liquid
cargos.
Objects of the invention are to provide an improved
means and method for reducing the corrosion of walls of
large tanks, which require no moving parts or equipment
except to compress, cool and circulate the cooling medium
or refrigerant, which employs small diameter piping, which
sump will stratify into layers, according to the speci?c
gravities of the water and stored cargo liquid. The liquid
of higher speci?c gravity will settle to the bottom, and the
lighter liquid will ?oat on the lower layer of liquid. In
the case of petroleum products the products will ?oat as
a layer on the water layer.
In the drawing, a possible upper level of a layer of
the water in the sump is shown by dot and dash line A,
desiccants, which has a minimum of loss of volatiles 35 and a possible upper level of a layer of gasoline ?oating
on the water layer in the sump is shown by the dot and
through conventional breather valves on tanks, which re
dash line B. When the level B rises to or beyond the
duces corrosion of tank walls beyond that caused by a
over?ow 11, the gasoline or condensed cargo liquid form
reduction in humidity by virtue of lowered tank tempera
ing the upper layer will pass out of the sump through the
tures, which is independent of the nature of the air or
over?ow 11 and be returned to the body of cargo liquid
gas in the tank and reduces the corrosion through lowered
in the tank.
humidity and temperature, and which is simple, and prac
Before the level A of water reaches the over?ow 11,
tical, uses compact and relatively inexpensive apparatus,
causes no contamination of cargo and no loss of volatile
portions of the cargo liquid, which employs no chemical
and requires little servicing attention.
Other objects and advantages will be apparent from
it should be withdrawn and isolated ‘as necessary to pre
vent level A from reaching the over?ow. For this pur
the following description of one example of the inven 45 pose, a pipe 12 may depend into the sump to near the
bottom thereof, and at its upper end have means to with
tion and the novel features will be particularly pointed
draw the water from the sump. For example a pump
out hereinafter in connection with the appended claims.
13, ‘operated by ‘a motor 14 may be disposed outside‘
In the accompanying schematic drawing a sectional
of tank 1, such as above the tank top 2, and connected
elevation of the upper part of a cargo tank is illustrated,
having applied thereto apparatus for reducing the cor 50 at its intake side to the upper end of pipe 12, The
motor is operated, as needed, through operation of
rosion of the tank walls in accordance with this invention.
switch 15, to keep the water level below the over?ow.
In the illustrated embodiment of apparatus useful for
The sump is preferably placed within the top zone of
reducing corrosion in accordance with this invention, the
the tank interior, but it can, if desired, be placed at the
cargo tank includes side walls 1 and a top wall 2. This
tank, in this example, is used to store and transport a 55 bottom of or even outside of the tank. The sump may
advantageously have an aperture 9a near its top. This
liquid lighter than water, such as a petroleum product
will permit any cargo liquid which enters the sump
and such tanks are seldom, if ever fully ?lled with the
through condensation or splashing to be returned to the
cargo liquid, and have an air or vapor space at the top to
cargo space by over?ow 11. In order that one may know
allow for expansion of the liquid during temperature
when water level A closely approaches the over?ow,
changes in the cargo liquid. In this air space at the top
making advisable the removal of some of the water from
of each such cargo tank, and above the maximum ex
the sump, a tube 16 extends from near the bottom of
pected liquid level therein, a heat exchange element or
the sump upwardly through the top 2 of the tank. With
unit 3 is disposed and mounted in any suitable manner.
in this tube 16 is con?ned a ?oat 17 which ?oats in water
A refrigeration unit 4 operated by a motor 5 or other
source of power is disposed exteriorly of the tank and 65 but sinks in the lighter cargo liquid such as gasoline.
This ?oat has a rod-like stem 18 extending upwardly in
connected by pipes 6 to the ends of the heat exchange
the tube 16 and above its top, which stem by its position
unit 3 so as to pass through the unit 3 a suitable cooling
or extent of projection above the upper end of tube 16,
medium. One of the pipes 6 may have a motor operated
indicates the level of water in the sump.
pump or circulator 7 therein to circulate the cooling
It is important that the element 3 and tray 8 be located
medium through element 3. It is not necessary that this
within and at the top of the vapor space inside the tank
cooling medium be cooled below the freezing temperature
3,024,817
,4
3
.
and above the maximum expected liquid level therein.
This makes it possible to have a continuous condensing
plying thereto a cooling medium and forming therewith
a complete refrigerating unit independent of and sepa
action on the mixed vapors of water and the cargo liquid,
accompanied by separation in the sump of the con
rate from said tank and said storage liquid, a collector
tray in said tank and disposed beneath said element and
also above said maximum expected level, and opening
densed vapors of the water and the cargo liquid with iso
lation and removal of the condensed water. This action
upwardly beneath all of the overall horizontal area oc
cupied by said element for receiving condensations by
is independent of the vapor pressure within the vapor
space of the tank, and there is a continuous cycling of
the ambient vapors within the vapor space past and under
the condensing influence of the cooling element. The
said element of ambient vapors in the space of said tank
above said maximum level, said element being unen
closed and fully exposed for continuous contact there~
with of said ambient vapors, a sump, means for conduct
cooled dry air and vapor at the element 3 is heavier
than the warmer humid air and vapor at the liquid sur
face, and this causes a continuous movement downwardly
tray, said sump having an outlet for removal of said
of the air and vapor past the element 3, during which the
vaporizable liquid which separates by strati?cation from
water and cargo liquid vapors are condensed and other
the water in said sump, and means for removing con
densed water vapors from the lower part of said sump.
3. Apparatus ‘for application to a closed tank con
taining a liquid immiscible with water, for reducing cor
rosion of interior tank walls by ambient water vapor in
the tank, which comprises a heat exchange element to
be supported in the interior of the full open space in the
ing into said sump any condensed vapors collecting in said
air and vapor replaces the downwardly moving air and
vapor.
The convection currents thus established are
forti?ed, when the ship having the cargo tanks, is moving,
through movement of the cargo liquid in the tank.
While this method and apparatus are particularly use
ful in tanks carrying a vaporizable cargo liquid, they are
also very useful in tanks carrying non-vaporizable cargo
liquids, in which latter case the coil 3 will condense
water vapors in the air that is present above the stored
main body of said tank above the maximum expected
level of said liquid therein and fully exposed for contact
therewith continuously by ambient vapors in the tank to
liquid and thus reduce possible corrosion of the tank walls
that might be caused by the presence of water vapors in
the tank above the liquid cargo. While it is advantageous
condense them, means forming with said element a com
water vapors from any of the cargo liquid whether con
densed vapors of the cargo liquid or just spray from
mum liquid level a sump disposed to receive said con
plete refrigeration system independent of and separate
from said tank and its contents, and delivering a cooling
medium to said element, means having a fully open upper
to have the sump 9 within the upper part of the tank, it
face for collecting condensations by said element of am
can be placed elsewhere in the tank or even outside of it.
The sump is also useful in separating the condensed 30 bient vapors in the space of said tank above said maxi
densations and in which the condensations may stratify
into separate layers of water and said liquid, said sump
having an outlet through which any of said stored liquid
condensed water and other vapors.
It will be understood that various changes in the de 35 therein may be removed and returned back into said
tank, and means connected to the interior of said sump
tails, materials and arrangements of parts, which have
for removing therefrom condensed waters vapors from
been herein described and illustrated in order to ex
the layer of water as necessary.
plain the nature of the invention, may be made by those
4. Apparatus for reducing corrosion in a relatively
skilled in the art within the principle and scope of the
invention as expressed in the appended claims.
40 large closed storage tank containing liquids lighter than
and immisicible with water, which comprises the combi
I claim:
nation with such tank of a heat interchange unit sup
1. Apparatus for reducing corrosion in a closed ship’s
ported in the top space in the main body of said tank
cargo storage tank under atmospheric pressure and con
above the maximum expected liquid level therein, means
taining a stored liquid immiscible with, and of different
speci?c gravity from, water, which comprises the combi 45 outside of said tank for supplying a cooling medium con
tinuously to said unit and forming therewith a complete
nation with said tank of a heat exchange element sup
refrigerating unit independent of and separate from said
ported in the full open space in the main body of said
tank and said storage liquid, a tray with an open
tank above the maximum expected liquid level therein,
upper face disposed within said tank beneath said unit,
means connected to said element and supplying thereto
the cargo liquid, that may get into the tray 8 along with
a cooling medium and forming therewith a complete re
frigerating unit independent of and separate from said
tank and said storage liquid, a collector member in said
tank disposed beneath said element, also above said maxi
mum expected liquid level, and having an upwardly open
face at least coextensive in area with the overall hori
zontal area occupied by said element, for collecting con
densations by said element of ambient vapors in the at
mosphere above said maximum level, said element being
unenclosed and fully exposed for continuous contact
therewith of said ambient vapors, a sump disposed with
a portion below the level of said collector member,
means for draining condensed vapors and any spray of
the stored liquid created by motion of the tank and col
50
also disposed above the maximum expected liquid level
in the tank, for receiving and collecting vapors con
densed by said unit, said unit being unenclosed and fully
exposed for continuous, direct contact therewith of ambi
ent vapors in the top portion of said tank, a sump having
a chamber separate from said tank, means connecting
said tray with said sump for conducting condensed vapors
from said tray to said sump, means connected to the
lower part of said sump for removing water therefrom,
means for discharging into said tank liquids from a se
lected zone of said sump, whereby when the Water and
condensed vapors from said stored liquid and splash
from the liquid separate into separate layers, the water
may be removed before it reaches said discharging means
and the other condensed vapors and liquid can return to
lected by said member into said sump where they may
stratify and separate the condensed water from said stored
liquid, means for returning the condensed said stored
liquid from said sump to said stored liquid in said tank,
means for supplying said cooling medium to said ex
and means for removing excess water from said sump.
change element is disposed outside of the liquid storage
the unvaporized liquid in said tank.
5. The apparatus according to claim 1, wherein said
2. Apparatus for resisting corrosion in a closed tank
space of said tank.
6. The apparatus according to claim 1, wherein said
containing a vaporizable liquid lighter than and immis 70
sump is disposed at a level above said maximum ex
cible with Water, which comprises the combination with
pected level, and has a gravity drain from the part thereof
said tank of a heat exchange element supported in the
occupied by the strati?ed condensed vapors of the stored
full open space in the main body of said tank above the
liquid into said tank below said sump.
maximum expected level therein of said liquid, means
7. The apparatus according to claim 2, wherein said
outside of said tank connected to said element and sup 75
8,024,617
5
6
sump is located within said tank and above said maximum
level.
8. The apparatus according to claim 1, and means con
nected to said sump and operable to indicate the level of
store a liquid that is immiscible with and of different
speci?c gravity from water, and vapon'zes to some extent
under atmospheric pressure, which comprises the com
bination with said tank of a heat exchange element sup
water in said sump.
9. The apparatus according to claim 3, and means con
ported in the top portion of the main body of said tank
above the maximum expected level of stored liquid there
nected to said sump and operable to indicate exteriorly
of the tank and sump the position of the strati?ed di
vision between the water and said liquid in the sump.
10. Apparatus for reducing corrosion in a closed tank 10
containing a stored liquid which is immiscible with water
and incompletely ?lling said tank which comprises the
in and exposed to continuous direct contact with ambient
vapors in said top portion for heat exchange therewith,
means for supplying a cooling ?uid located exteriorly of
said tank and connected to said element for circulating
said cooling ?uid through said element and forming with
the latter a complete refrigeration unit independent of
and separate from said tank and said stored liquid, an
combination with such tank of means disposed in the
upwardly opening tray disposed in said tank immediately
open space in the upper part of the main body of said
tank and unenclosed and fully exposed for continuous 15 below said element and also above the said maximum
expected level of stored liquid in said tank, and of a
contact with all ambient vapors in the upper part of
size to collect substantially all of the ambient air and
the tank, for condensing out the condensible part of
vapors condensed by said element and any spray and
ambient vapors from the air in the space between the
splash therein of the stored liquid due to motion of the
maximum liquid level in said tank and the top of the
tank, means having an upwardly opening collector also 20 tank, -a sump connected to said tray to receive from the
tray any liquid collecting in said tray and in which sump
in said space in the upper part of said tank and im
the condensed vapors of said stored liquid and water
mediately below said condensing means disposed to re
ceive the condensed vapors, means connected to said
vapor may stratify and separate into superposed layers,
a level indicator connected to said sump for indicating
receiving means and operable to separate from the col—
lected condensation the condensed water, means by which 25 the upper level of one of the said strati?ed layers, means
connected to said sump by which a desired part of the
the separated water may be removed and discarded, and
layer of condensed vapors of the stored liquid in said
means by which the balance of the condensed vapors
sump may be progressively removed from the sump and
may be returned to the tank.
returned to said tank, and means also connected to said
11. The method of reducing corrosion in a closed
liquid storage tank containing a liquid immiscible with 30 sump for removing to the exterior of said tank and dis
carding any part of the condensed water layer.
water, and having a maximum level below the top of
15. The apparatus according to claim 14, wherein said
said tank, which comprises continuously condensing with
sump is located in the upper part of said tank also above
in the tank, in the space thereof above the liquid level
said maximum expected level of stored liquid, and the
therein, the ambient vapors in the space between said
maximum liquid level and the top of said tank, continu 35 means connected to said sump enabling removal of con
densed vapors of the stored liquid includes a gravity drain
ously collecting the condensed vapors within the tank
into said tank for such condensed vapors of the stored
and causing them to stratify into separate layers of water
liquid.
and said liquid, removing said layer of said liquid and
16. The apparatus according to claim 14, wherein said
returning it to the body of said liquid in said tank, and
removing said water of said water layer sufficiently to 40 heat exchange element has a closed passage therethrough
for the passage of a cooling ?uid therethrough, and an
prevent its return to said body of liquid in said tank with
outer exposed surface in the space of said tank above
said removed layer of said liquid.
said maximum expected level of stored liquid, whereby
12. The method of reducing corrosion in a closed ship’s
the condensation of ambient vapors in the tank is con
cargo storage tank containing a liquid lighter than and
immiscible with water, and having a maximum level be 45 tinuous.
17. The method of reducing corrosion in a storage tank
low the top of said tank, which comprises continuously
for volatile liquids that are immiscible with water and
condensing within the tank in the space above the liquid
which has a vapor space in the upper part thereof above
level therein, the ambient condensible vapors in the space
the maximum expected liquid level therein, which com
between said maximum liquid level and the top of said
tank, causing the condensed vapors and any splash of the 60 prises continuously exposing all ambient vapors in said
space while con?ned in said space to an exposed and un
said liquid that may be caused by the motion of the ship,
covered cooled surface at a temperature that condenses
and becoming mixed with the condensed vapors to stratify
from such ambient vapors the vapors of said stored
into separate layers of water and said liquid, draining
liquid and water vapors, continuously collecting all of
off and isolating the strati?ed layer of condensed water,
and returning the layer of condensed liquid to said tank. 55 said condensed vapors in said space, and separating the
water condensation from the condensation of the stored
13. The method of reducing corrosion in a closed tank
liquid, continuously returning the condensation of the
under variable atmospheric pressure containing a stored
stored liquid to said tank, and discarding the water
liquid immiscible with water, and having a maximum
condensation.
level below the top of the tank, comprising continuously
condensing out within the tank in the space above the 60
References Cited in the ?le of this patent
liquid level therein, the condensible part of ambient
vapors from the air in the tank space between said maxi
UNITED STATES PATENTS
mum level and the top of said tank, separating out and
2,059,942
Gibson _____________ .. Nov. 3, 1936
discarding the water from said condensed vapors, and
2,321,964
Zieber _______________ _... June 15, 1943
returning the balance of the condensed vapors to the tank 65 2,344,765
Dana et al ____________ __ Mar. 21, 1944
interior.
2,379,215
Brinkmann _________ __ June 26, 1945
14. Apparatus for reducing corrosion in closed, ship’s
cargo tank under atmospheric pressure that is used to
2,449,688
2,577,598
Brinkoeter ___________ __ Sept. 21, 1948
Zwickl ______________ __ Dec. 4, 1951
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