U.S. patent application number 12/075229 was filed with the patent office on 2009-09-10 for welded full contact floating roof and method.
This patent application is currently assigned to HMT,Inc.. Invention is credited to Michael J. Doxey, Richard King.
Application Number | 20090223957 12/075229 |
Document ID | / |
Family ID | 41052536 |
Filed Date | 2009-09-10 |
United States Patent
Application |
20090223957 |
Kind Code |
A1 |
Doxey; Michael J. ; et
al. |
September 10, 2009 |
Welded full contact floating roof and method
Abstract
A sealed floating roof for a storage tank, comprising a frame
and roof panels, in which the frame provides a guide for directing
an automatic welder along said structure to allow for automated
welding of the roof panels to the frame, and a method of forming
such a roof.
Inventors: |
Doxey; Michael J.; (Houston,
TX) ; King; Richard; (Tomball, TX) |
Correspondence
Address: |
R. PERRY MCCONNELL, P.C.
9001 FOREST CROSSING, SUITE F
THE WOODLANDS
TX
77381
US
|
Assignee: |
HMT,Inc.
|
Family ID: |
41052536 |
Appl. No.: |
12/075229 |
Filed: |
March 6, 2008 |
Current U.S.
Class: |
220/216 ; 29/521;
29/530 |
Current CPC
Class: |
B23K 31/02 20130101;
Y10T 29/49616 20150115; Y10T 29/49936 20150115; B23K 2101/12
20180801; B65D 88/34 20130101; Y10T 29/49968 20150115; Y10T
29/49993 20150115; Y10T 29/49629 20150115 |
Class at
Publication: |
220/216 ; 29/530;
29/521 |
International
Class: |
B65D 88/34 20060101
B65D088/34 |
Claims
1. A method of forming a sealed floating roof for a storage tank,
comprising the steps of forming roof panels, forming a roof by
interconnecting said roof panels, guiding an automatic welder
essentially parallel to the interconnections of said roof panels,
and welding said roof panels together with said automatic
welder.
2. The method of claim 1, wherein the step of providing roofpanels
additionally comprises the steps of extruding formed frame
segments, and assembling said roof panels using said frame
segments.
3. The method of claim 2, wherein the step of extruding formed
frame segments additionally comprises the step of forming a
depression in an upper surface of said frame segments.
4. The method of claim 2, wherein the step of guiding an automatic
welder essentially parallel to the edges of the roof panels
additionally comprises the step of guiding said automatic welder by
tracking said automatic welder in said depression.
5. The method of claim 3, wherein the step of forming a depression
in an upper surface of at least some of said frame segments
additionally comprises the step of forming said depression along an
upper edge of said frame segments.
6. The method of claim 5, wherein the step of interconnecting said
roof panels additionally comprises the step of forming a walled
trough along an upper surface of said roof by joining said frame
segments with said depressions adjacent.
7. The method of claim 6, wherein the step of guiding a automatic
welder essentially parallel to the edges of the roof panels
additionally comprises the step of guiding said automatic welder by
tracking said automatic welder in said trough.
8. A sealed floating roof for a storage tank, comprising a
plurality of coupled frame segments comprising an upper surface,
and a plurality of roof sheets welded to said frame segments to
form a sealed surface, wherein said frame segments comprise a guide
for controlling the movement of a automatic welder.
9. The sealed floating roof for a storage tank of claim 8, wherein
said frame segments are extrusions.
10. The sealed floating roof for a storage tank of claim 8, wherein
said frame segments are aluminum extrusions.
11. The sealed floating roof for a storage tank of claim 8, wherein
at least some of said frame segments comprise a depression in said
upper surface.
12. The sealed floating roof for a storage tank of claim 11,
wherein at least some of said frame segments are shaped so that
coupling of adjacent frame segments forms a walled trough in said
upper surface.
Description
FIELD OF THE INVENTION
[0001] The invention pertains to sealed floating roofs for storage
tanks.
BACKGROUND OF THE INVENTION
[0002] Above ground storage tanks are frequently used to store
hydrocarbon fluids. Because the stored fluid is volatile, the
storage tank is often equipped with a floating roof under the fixed
roof. The floating roof which floats above the stored fluid and
moves up and down with the fluid level. Floating roofs greatly
reduce fluid evaporation, preventing loss of the stored fluid and
reducing pollution due to hydrocarbon evaporation into the
atmosphere.
[0003] Additionally, it is desirable to provide floating roofs that
are full-contact roofs, allowing the roof structure to be in direct
contact with the fluid surface. Such roofs do not allow an air gap
between the bottom of the roof surface and contained fluid. When
air gaps exist, they allow an evaporation zone over the top of the
fluid that increases the risk of leakage around the floating roof
structure. However, full contact floating roofs must be tightly
sealed to prevent direct vapor leakage or evaporation through small
gaps in the roof structure. Such leakage or evaporative losses can
create unwanted pollution as well as the economic loss of stored
product.
[0004] However, typical floating roofs are large and must be
assembled on site. The structure typically comprises a framework of
segments that are assembled to form and open lattice, and a
plurality of roofpanels or sheets that are then attached to the
framework to form the upper surface of the roof. Roof panels or
sheets are typically attached by bolting them in place, and
sometimes sealed with sealants that are generally known in the
industry.
[0005] Such construction can prevent the desired sealing
effectiveness of the roof from being achieved. Sealants can degrade
over time due to environmental conditions, and may be attacked by
contact with the stored fluid or by vapors. Bolted connections are
not vapor tight. Effecting repairs can require draining the storage
tank, resulting in lost revenue, and may require workers to operate
in a hazardous environment. Accordingly it is desirable to provide
a seal between the roof panels and the framework that is highly
resistant to degradation over time, and that will provide a strong,
durable roof over its life expectancy.
[0006] One possible approach is to weld the edges of the roof
panels to the framework, so that every seam between the roofpanels
and the framework is permanently sealed. However, if welding were
to be done by hand, the large size of the typical floating roof
would require a large expenditure of man hours, and the work would
often have to be done in an extremely uncomfortable
environment.
[0007] Accordingly, it is desirable to provide a floating roof,
especially one intended for full contact, with welded construction
so that the roof panels are welded to the framework. It is further
desirable to accomplish this welding with an automatic welder.
SUMMARY OF THE INVENTION
[0008] The invention comprises a floating roof comprising frame
segments and roof panel top and bottom sheets that are shop welded
to the frame segments to form fully sealed roof panels. These
roofpanels are then assembled and welded together in the storage
tank to form a fully welded, full contact floating roof. In a
preferred embodiment, the frame segments are aluminum extrusions,
which allow strong, yet relatively light-weight construction and
high resistance to corrosion over time. Individual, fully welded
roof panels may be constructed and pre-tested at a factory
location, then shipped to the job site for final assembly. It is
generally desirable to assemble the roof panels into a staggered
rectangular grid. In this manner, standard-sized rectangular roof
panels may be used to complete almost the entire roof, with
differently shaped panels only required to form the outer, circular
circumference of the roof.
[0009] For example, a typical rectangular panel of a preferred
embodiment of the invention would be framed using four lengths of
an extruded aluminum frame segment, with top and bottom sheets
edge-welded around their entire perimeters to the frame segments,
forming a fully sealed roof panel. These roof panels can then be
tested at the factory for seal and weld integrity, and modified as
desired for a particular installation. For example, sniffers or
other test equipment may be inserted into a panel through its top
sheet, allowing a customer to operate real-time test equipment once
the roof is placed in operation. The completed roof panels may then
be shipped to the job site for assembly.
[0010] Once at the job site, the roof panels may be supported on
legs or temporary supports, and frame segments of adjacent panels
riveted together, preferably using a self-piercing rivet gun such
as Model #ESN50. Those of skill in the art will recognize that,
during this assembly process, the roof panels must be supported in
a way that insures that they are properly leveled with respect to
each other. Once the roof panels have been riveted together to form
the overall roof structure, the roof structure is completed by
welding the roof panels together.
[0011] To weld the roof panels together, a self-propelled automatic
welder, such as Model #BUGHDT1010 by HMT, Inc., using components
manufactured by Bug-O Systems and Lincoln Welding Equipment may be
used. However, it is necessary to properly guide the welder so that
the track of the weld is correctly positioned along the contact
seam between the adjacent roof panels. Accordingly, it is desirable
to provide a guide to correctly position the automatic welder.
[0012] To accomplish this goal, the frame segments are preferably
extruded with a formed depression in an upper edge of the frame
segment. Due to the nature of the construction, a single form of
frame segment may be used, leaving a flat side turned outward from
the roof panels. When the roof panels are riveted together, these
flat sides form the outer wall of the roof panel, and are riveted
to the flat sides of the adjacent roof panels' frame segments, with
two such frame segments mechanically coupled "back-to-back." When
correctly positioned, the depressions in the upper edges of two
such joined segments will be adjacent, and will formed a walled
trough in the upper surface of the beam.
[0013] As those of skill in the art will recognize, many
alternatives to such construction may exist. For example, an entire
beam could be extruded as a single piece, with a depression formed
in its upper surface, without departing from the spirit of the
invention. However, such an extrusion would be heavier and harder
to position and control during assembly of the roof. Further, such
a construction method would essentially require top and bottom
sheets of the roof panels to be welded into place at the job site,
increasing the complexity of the on-site construction, and making
testing of individual cells in the roof much more difficult.
[0014] With a roof thus assembled, each walled trough between roof
panels acts as a directional guide for the automatic welder, and an
automatic welder thus controlled will maintain an appropriate path.
It is therefore desirable to modify the aforementioned stock
automatic welder by attaching a guide wheel to its carriage to
insure that it follows the guide track in the upper surface of the
framework. In a preferred embodiment, guide wheels are attached to
both the front and rear of the automatic welder's carriage, to
insure that one end does not skew during transit.
[0015] Completion of the floating roof can thus be accomplished by
positioning the automatic welder to transit along the walled
troughs, using the walls for guidance and forming a continuous
welding bead in the trough. Those of skill in the art will
recognize that, without departing from the spirit of the invention,
guidance of the automatic welder may be accomplished by a variety
of alternate methods, such as providing multiple parallel troughs
for guide wheels, radio or light frequency remote controls, direct
linkage remote controls, or computer driven programmable controls
integrated into the welder itself. While functional, such
alternatives may increase the complexity of the assembly
operation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1A is a cross section of a frame segment extrusion of
one embodiment of the present invention.
[0017] FIG. 1B is a cross section of two adjacent roof panels of
one embodiment of the present invention.
[0018] FIG. 2A is a top view of a roof panel of one embodiment of
the present invention.
[0019] FIG. 2B is a bottom view of a roof panel of one embodiment
of the present invention.
[0020] FIG. 3 is a side schematic view of an automatic welder
operating to weld roof panels together in an assembled roof.
[0021] FIG. 4 is a schematic view of an assembled full contact
floating roof of one embodiment of the present invention.
DETAILED DESCRIPTION
[0022] Referring to FIG. 1A, an extruded frame segment 10 of a
preferred embodiment of the present invention is seen in
cross-section. Referring also to FIG. 1B, a cross-section of two
adjacent assembled roof panels 12, 14 employing multiple frame
segments 10 is shown. Frame segments 10 of FIGS. 1A, 1B comprises
an upper lip 16 which supports upper roof sheet 18 and which is
placed into sealing contact with upper roof sheet 18 by welding
along the perimeter 20 of upper roof sheet 18. Similarly, frame
segment 10 comprises a lower lip 22 that is placed into sealing
contact with lower roof sheet 24 by welding along the perimeter 26
of lower roof sheet 24. When so assembled, frame segments 10 and
upper and lower roof sheets 18, 24 form a sealed cavity 28 that
forms a component of a full contact floating roof.
[0023] Roof panels 12, 14 are preferably constructed and initially
tested at a factory before being shipped to a job site for assembly
into a full contact floating roof. (Such as depicted in FIG. 4)
When placed adjacent to each other for assembly into a roof, roof
panels 12, 14 are first leveled and properly aligned, then
mechanically joined together, as by use of stainless steel rivets
30.
[0024] Frame segment 10 additionally preferably comprises a first
top depression 32 and a second top depression 34. When joined in
complementary orientation, as shown in FIG. 1B, the first top
depressions 32 of two frame segments 10 combine to form a walled
trough 36. Similarly, the second top depressions 34 combine to form
a weld seam 38.
[0025] Referring now to FIGS. 2A and 2B, top and bottom views of
assembled roof panels 212 are shown respectively. Frame segments
210 are angle-cut at the corners to provide squared-off corners
215. Upper roof sheet 218 is fully welded to frame segments 210
along its perimeter 220, and lower roof sheet 224 is fully welded
to frame segments 224 along its perimeter 226. Frame segments 210
are also welded at corners 214 to provide a completely sealed roof
panel. Although roof panels 212 are preferably rectangular in
shape, those of skill in the art will recognize that this shape is
a matter of engineering preference, and that panels with curved
edges will be required to form the perimeter of a circular floating
roof as shown in FIG. 4. If desired, one or more portals 228 may be
opened in the upper roof sheet 218, to provide access to the
interior of the roof panel 212 for the insertion of leak sniffers
or other instrumentation.
[0026] Referring now to FIG. 3, a schematic view of an automatic
welder 310 for use in completion of the floating roof is shown. The
automatic welder 310 comprises a carriage 312 mounted on wheels
314, allowing it to roll across the upper surface 316 of the
floating roof. A weld head 320 is held in position by control arm
318, allowing weld head 320 to be positioned to form a weld along
weld seam 38 of FIG. 1B. Guide wheels 322, 324 are attached to the
automatic welder 310, and are fitted into walled trough 36 of FIG.
1B, controlling the line of motion of the automatic welder 310, and
allowing the automatic welder 310 to track each weld seam in the
floating roof under assembly to completely seal the roof.
[0027] Those of skill in the art will recognize that other means of
guiding the automatic welder, such as (without limitation) radio
frequency controls, directly connected steering controls, or
alternate guide lines formed in the roof under construction could
be used without departing from the spirit of the invention.
Additionally, guidance could be accomplished without using multiple
guide wheels.
[0028] Referring now to FIG. 4, a schematic top view of a welded,
full contact floating roof of the present invention is shown.
Floating roof 410 preferably comprises a plurality of rectangular
roof panels 412 and perimeter curved roof panels 414. Those of
skill in the art will recognize that panels 412 and 414 are
constructed in the same fashion, with curved panels 414 requiring
curved frame segments along one side. Further, if the floating roof
is of square or rectangular configuration, curved roof panels will
be unnecessary.
[0029] One or more panels, for example 416, may be provided with
man-way access, to allow personnel to access the lower portion of
the roof if needed. Each of the seams 418 between adjacent roof
panels 412, 414 is welded by use of the automatic welder as
discussed above, providing a full contact floating roof that is
fully sealed against evaporation by welds.
[0030] Those of skill in the art will also recognize that the
floating roof of this invention may be fitted with a sliding edge
seal (not shown) around its perimeter as known in the art.
Additionally, the roof may be equipped to be held at a particular
height, for example, for maintenance operations, by providing it
with non-penetrating cable attach points (non-shown) on its upper
surface, or by providing non-penetrating leg supports (not shown)
on its lower surface. Thus, these attachments can be made without
penetrating the roof, preserving its sealing integrity.
[0031] The above examples are included for demonstration purposes
only and not as limitations on the scope of the invention. Other
variations in the construction of the invention may be made without
departing from the spirit of the invention, and those of skill in
the art will recognize that these descriptions are provide by way
of example only.
* * * * *