Note: Descriptions are shown in the official language in which they were submitted.
CA 02454084 2003-12-23
1 ST~ E T~.N~~F RTECTIN IfSTE
2
3 ~IELi3 C~~ THE INVENTIC>N
4 The invention, involves methodology ,and apparatus for providing
protection of interior roof :surfaces in structural enclcasures such as tanks,
more
6 particularly for sealing inner roof surfaces and disconitinuities in the
roof of tfie tank
7 from the gases or condensc~tes that emanafe from the fluids and gases
contained in
8 the vessel.
9
BACI~~R(~IJN~ ~F THE INVEI~ITif3N
~ 1 This invention relates to storage tanks that contain a variety o~f fluids
12 that emit gases or condensates and that have overheG~d roof structures to
cover and
13 protect the containment vessel and ifs contents. The interior surfaces on
the roaofs of
14 such vessels are subject to corrosion and deteriorailion the°ough
contact with the
gases or condensates that emanate from the fluids an~o' gasE:S that are
contained in
16 the vessel.
17 The prior art methodology for protecting the inner surface of thE: roofs
18 from gases or condensates is to apply a coat of paint;, chemicals or other
materials
19 to the inner surface of the roof andlor fo any structures that support the
inner surface
of the roof. The paint, chemicals or other materials ere resistant to
corrosion and
21 deterioration from the gases or condensates. The prf:paration of roof
surfaces for
22 coating is difficult, time consuming and costly, particularly as the
supporting
23 structures for such roofs can be complex and inaccessible. As a result the
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CA 02454084 2003-12-23
1 application of coatings to interior roof surFaces and their supporting
structures are
2 prone to failure from peeling, cracking, or other deterioration..
3 A second alaproach is to remove ar'd replace the corroded roof
4. structure with a new roof structure. Again, this approach is very costly,
and results in
the tank remaining out of operation for considerable periods of time.
6 A third approach is to inject a gas blanket inside the tank that prevents
7 or minimizes the escape of gases or condensates from the fluids in the tank.
This
8 approach requires special construction of the tank, and has limited
application to
9 certain fluids and gases.
A fourth approach is to attach a continuous layer of geosynthetic
11 membrane to the roof, andlor supporting structures of roofs a sing sealing
systems for
12 floors and walls as described in Provisional Patent Application 60/462,301
around
13 the perimeter of the membrane and discontinuities. Structural support to
the
14 membrane is provided by attaching the membrane directly tf~ the interior
surFace of
'15 the roof, or to the structures supporting the roof. This method proves to
be a costly
16 and difficult process. Inherent in this approach is the creation of many
17 discontinuities in the membrane increasing the risks ~of perrneability and
functional
18 failure.
19 There is a need for a system which protects and seals interior roof
surfaces in structural enclosures such as tanks, morE; particularly for
sealing inner
21 roof surtaces around inner roof perimeters and discontinuities in the roof
of the tank
22 from the gases or condensate that emanate from the fluids and gases are
contained
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CA 02454084 2003-12-23
1 in the vessel, and which is not susceptible to the costs and failures
associated with
2 prior art.
3 This invention involves the use of geosynthetic membranEa, and
4 technologies used to seal such membranes to tank surfaces as described in
prior
patent applications along with a system of suspending the membranes in tree
tank,
6 so as to protect the interio~° surfaces of the tank roof from the
gases or condensate
that emanate from the fluida; and gases contained in the vessel.
3
CA 02454084 2003-12-23
1 SUMMARY OF THE INVENTICJN
2 The objects of the invention are achieved through a liner system that
3 creates an impermeable be~rrier of geosynthetic material that is suspended
or' upheld
4 below the inner surface of the roof and around discontinuities in the
structural
envelope of the roof, if such exist. The liner system is sealed to the upper
perimeter
6 of the tank so as to form an impenetrable layer to liquids, or gases or
condensates
a that may emanate from the. vessel to the interior surfe~ces and structures
of the roof
8 of the tank.
9 The roof seal invention consists of two main elements. The first
1a element consists of a geosynthetic membrane, fabric=~ted and suspended in
such a
11 way as to provide a continuous, impermeable layer that completely and
contirmously
12 separates the lower internal environment of the storage vessel containing
fluids and
13 gases, from the upper internal environment of the storage vessel and the
roof. The
14 formation of a layer that separates the lower region c~f the structural
envelope from
'15 the upper region of the structural envelope requires ;a membrane that
contains no
16 discontinuities, and which extends at least to the extremities of the
structural
17 envelope.
18 The second element consists of a series of attachments to sealably
19 attach the extremities of the membrane. The outer exi:remities of the
membrane are
20 sealably attached to the inner surface of the structural envelope, while
the inner
21 surface can be attached to a center column of the tank, at some point below
the roof
22 of the structural envelope. By sealing at the extremities ofi the liner, a
reliable
23 continuous membrane liner is the result.
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1 ~ne potential method of perimeter attachment, among many, is an
2 adaptation of mechanical attachments or seals dEacribed in Provisional
Patent
8 Application 601462,301 to applicants. In addition, tanks may contain other
internal
4 penetrations or connections between the roof of the tank and the lower
regions of
the tank, such as support columns, gage boards, or pipes. The continuous
6 geosynthetic membrane must be sealed to such penetrations so as to maintain
an
7 impenetrable barrier between the lower internal environment of the storage
vessel
8 containing fluids and gases, and the upper internal environment of the
storage
9 vessel and the roof. This may be achieved by any number of sealing methods.
A preferred embodiment of the invention add s a supporting structure
11 that suspends the membrane above the lower internal environment of the
structural
12 envelope. Such supporting elements may consist of elements within the
13 geosynthetic material itself that provide strength and integrity to the
barrier, external
14 supports such as tensioned filaments, cables, or rigid supports, capable of
'I5 supporting or lifting the weight of the geosynthetic material. Ullhile
some geosynthetic
16 materials contain filaments or structures designed to provide the material
itself with
17 sufficient lateral strength to withstand the lateral forces of being
suspended, the use
18 of external structures, such as tension cables, or rigid supports, minimize
stress on
19 the material itself, and provide better control of the po:~itioning and
installation of the
material within the tank envir onment.
21 Structures to support the material can be attached to the interior of the
22 structural envelope, above or below the continuous synthetic membrane, and
the
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1 membrane can rest on the supporting elements, or be supported by the
supporting
2 elements with various methods of attachment from above.
3 Another embodiment of the invention envisages a system of ventilating
the upper region of the structure! envelope above geosynthetic membrane from
outside the tank, ensuring that minute permeations of gases or elements that
pass
6 through the geosynthetic membrane do not accumulate above the geosynthetic
7 membrane, resulting in corrosion and deterioration of the interior surface
of the roof.
8 Such ventilation systems may be simply apertures in the upper regions,
allowing the
9 flow of air, or any variety of active ventilation systems as those used in
rigid roof
1Q structures for homes or other commercial buildings requiring ventilation.
11 An alternate embodiment of the invention includes the use of a boot of
12 liner material to seal discontinuities within the tank roof that penetrate
tPee liner
13 membrane. The boot is welded or similarly attached to the liner membrane at
the
14 penetration to the membrane, and is mechanically sealed or' attached to the
roof or
discontinuity. This provides a continuously sealed liner membrane about the
16 discontinuity preventing the discontinuity and upper 'tank region from
corrosion or
17 damage from tank liquids, gases, or condensates.
A system for installing a roof liner includes attaching and sealing a
19 membrane adjacent an attachment or discontinuity on the roof, attaching
support
2~ elements within the interior of the envelope, raisirn~ the support elements
and
membrane to the tanks periphery, securing the supporfi elements to the tank's
22 periphery and sealing fihe membrane to the tank.
23
6
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1 E~RIEF ~ESCRIPTION OF ThIE C~ IPVII~GS
2 Figure 1 is a sectional view of a roof liner showing the main elements
3 of the roof liner;
4 Figure ~ shows a roof liner with suspended cables undet-neath for
supporting the roof liner;
8 Figure 3 shows a view from underneath a roof finer suspended over
7 tension cable supports, along with detail on cable attachment;
8 Figure 4 shov~rs details of the sealing of the geosynthetic membrane to
9 the perimeter of a tank by means of a mechanical compression system, and
details
of the attachment of a cable directly to the mechanical compression system;
11 Figure 5 shows one form of attachment of the geosynthetic liner to a
12 discontinuity;
13 Figure 6 shows a variation of Figure 6, attachment of the geosynthetic
14 liner to a discontinuity;
Figure 7 shows a form of the invention utilizing vents in the upper
'~ 6 region of the tank to ventilate the region above the roof liner.
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DETAILED DE~CRIPTI~N t7F THE PREFEIRRED EMB~DIMENT
2
8
