Storage tank roof protection system

Abstract

A system and method for suspending and sealing a liner below the roof of a tank for protecting the liner from fluids contained within the tank. The liner is a geosynthetic membrane, which is impervious to fluids, and provide a continuous barrier between the fluids and the inner surface of the roof. The liner is suspended between compression seals at the periphery of the tank. Further, cables are attached at the walls of the tank above or below the liner to support the suspended liner. The liner is sealed about any discontinuities, such as ventilation openings or access to the inside of the tank in the roof. Optionally, ventilation is also provided to the space above the liner by providing vents in the roof which do not extend through the liner.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority of U.S. Provisional Patent application Ser. No. 60/528,492 filed Dec. 11, 2003, the entirety of which is incorporated herein by reference.

FIELD OF THE INVENTION

The invention involves methodology and apparatus for providing protection of interior roof surfaces in structural enclosures such as tanks, more particularly for sealing inner roof surfaces and discontinuities in the roof of the tank from the gases or condensates that emanate from the fluids and gases contained in the vessel.

BACKGROUND OF THE INVENTION

This invention relates to storage tanks that contain a variety of fluids that emit gases or condensates and that have overhead roof structures to cover and protect the containment vessel and its contents. The interior surfaces on the roofs of such vessels are subject to corrosion and deterioration through contact with the gases or condensates that emanate from the fluids and gases that are contained in the vessel.

The prior art methodology for protecting the inner surface of the roofs from gases or condensates is to apply a coat of paint, chemicals or other materials to the inner surface of the roof and/or to any structures that support the inner surface of the roof. The paint, chemicals or other materials are resistant to corrosion and deterioration from the gases or condensates. The preparation of roof surfaces for coating is difficult, time consuming and costly, particularly as the supporting structures for such roofs can be complex and inaccessible. As a result the application of coatings to interior roof surfaces and their supporting structures are prone to failure from peeling, cracking, or other deterioration.

A second approach is to remove and replace the corroded roof 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.

A third approach is to inject a gas blanket inside the tank that prevents or minimizes the escape of gases or condensates from the fluids in the tank. This approach requires special construction of the tank, and has limited application to certain fluids and gases.

A fourth approach is to attach a continuous layer of geosynthetic membrane to the roof, and/or supporting structures of roof, using sealing systems for floors and walls as described in Provisional Patent Application 60/462,301 around the perimeter of the membrane and discontinuities. Structural support to the membrane is provided by attaching the membrane directly to the interior surface of the roof, or to the structures supporting the roof. This method proves to be a costly and difficult process. Inherent in this approach is the creation of many discontinuities in the membrane increasing the risks of permeability and functional failure.

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 roof surfaces around inner roof perimeters and discontinuities in the roof of the tank from the gases or condensate that emanate from the fluids and gases are contained in the vessel, and which is not susceptible to the costs and failures associated with prior art.

SUMMARY OF THE INVENTION

Embodiments of the invention provide systems for suspension of prior art geosynthetic membranes and related technologies used to seal said membranes to tank surfaces so as to protect the interior surfaces of the tank roof from the gases or condensate that emanate from the fluids and gases contained in the vessel.

The objects of the invention are achieved through a liner system that creates an impermeable barrier of geosynthetic material that is suspended or upheld 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 of the tank so as to form an impenetrable layer to liquids, or gases or condensates that may emanate from the vessel to the interior surfaces and structures of the roof of the tank.

Embodiments of the roof seal comprise a geosynthetic membrane, fabricated and suspended in such a way as to provide a continuous, impermeable layer that completely and continuously separates the lower internal environment of the storage vessel containing fluids and gases from the upper internal environment of the storage vessel and the roof, the layer that separates the lower region of the structural envelope from the upper region of the structural envelope requiring a membrane that contains no discontinuities, and which extends at least to the extremities of the structural envelope; and a series of attachments to sealably attach the extremities of the membrane for forming a reliable continuous membrane liner.

More particularly, the outer extremities of the membrane are sealably attached to the inner surface of the structural envelope, while the inner surface can be attached, preferably to a center column of the tank, at some point below the roof of the structural envelope.

One potential method of perimeter attachment, among many, is an adaptation of mechanical attachments or seals described in Provisional Patent Application 60/462,301 to Applicants. In addition, tanks may contain other internal 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 geosynthetic membrane must be sealed to such penetrations so as to maintain an impenetrable barrier between the lower internal environment of the storage vessel containing fluids and gases, and the upper internal environment of the storage vessel and the roof. This may be achieved by any number of sealing methods.

A preferred embodiment of the invention further comprises a supporting structure that suspends the membrane above the lower internal environment of the structural envelope. Such supporting elements may consist of elements within the geosynthetic material itself that provide strength and integrity to the barrier, external supports such as tensioned filaments, cables, or rigid supports, capable of supporting or lifting the weight of the geosynthetic material. While some geosynthetic materials contain filaments or structures designed to provide the material itself with sufficient lateral strength to withstand the lateral forces of being suspended, the use of external structures, such as tension cables, or rigid supports, minimize stress on the material itself, and provide better control of the positioning and installation of the material within the tank environment.

Structures to support the material can be attached to the interior of the structural envelope, above or below the continuous synthetic membrane, and the membrane can rest on the supporting elements, or be supported by the supporting elements with various methods of attachment from above.

Another embodiment of the invention envisages a system of ventilating the upper region of the structural envelope above geosynthetic membrane from outside the tank, ensuring that minute permeations of gases or elements that pass through the geosynthetic membrane do not accumulate above the geosynthetic membrane, resulting in corrosion and deterioration of the interior surface of the roof. Such ventilation systems may be simply apertures in the upper regions, allowing the flow of air, or any variety of active ventilation systems as those used in rigid roof structures for homes or other commercial buildings requiring ventilation.

An alternate embodiment of the invention includes the use of a boot of liner material to seal discontinuities within the tank roof that penetrate the liner membrane. The boot is welded or similarly attached to the liner membrane at the penetration to the membrane, and is mechanically sealed or attached to the roof or discontinuity. This provides a continuously sealed liner membrane about the discontinuity preventing the discontinuity and upper tank region from corrosion or damage from tank liquids, gases, or condensates.

A system for installing a roof liner includes attaching and sealing a membrane adjacent an attachment or discontinuity on the roof, attaching support elements within the interior of the envelope, raising the support elements and membrane to the tanks periphery, securing the support elements to the tank's periphery and sealing the membrane to the tank.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a roof liner suspended according to an embodiment of the invention;

FIG. 2 shows a roof liner with suspended cables underneath for supporting the roof liner;

FIG. 3 is a view from underneath a roof liner suspended over tension cable supports, illustrating details of cable attachment;

FIG. 4a illustrates details of the sealing of the geosynthetic membrane to the perimeter of a tank by means of a mechanical compression system;

FIG. 4b illustrates details of the attachment of a cable directly to the mechanical compression system according to FIG. 4a;

FIG. 5 illustrates one embodiment of attachment of the geosynthetic liner to a discontinuity;

FIG. 6 illustrates a variation of the attachment of the geosynthetic liner to a discontinuity according to FIG. 5;

FIG. 7 illustrates an embodiment utilizing vents in the upper region of the tank to ventilate the region above the roof liner;

FIG. 8 is a upward perspective view of a plurality of supporting elements attached about a central support member at a roof in a tank, prior to suspending a membrane therein; and

FIG. 9 is an upward perspective view according to FIG. 8 following suspension of the membrane therein and attachment of the supporting elements to the inner surface of the tank.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Having reference to FIGS. 1-7, embodiments of unique systems are shown for suspension of prior art geosynthetic membranes 10 and related technologies used to seal said membranes 10 to inner tank surfaces 11 so as to protect an interior surface 12 of a tank roof 13 from the gases or condensate that emanate from fluids and gases contained in a storage vessel or tank 14.

A liner system creates an impermeable barrier using the geosynthetic material or membranes 10 by upholding or suspending the membrane 10 below the inner surface 12 of the roof 13 and around discontinuities in the structural envelope of the roof 13, if such exist. The liner system is sealed adjacent an upper perimeter 15 of the tank 14 so as to form an impenetrable layer to liquids, or gases or condensates that may emanate from the tank to the interior surfaces 12 and structures of the roof 13 of the tank 14.

Embodiments of the sealing system comprise the geosynthetic membrane 10, which is fabricated and suspended in such a way as to provide a continuous, impermeable layer that completely and continuously separates the lower internal environment L of the tank 14, containing fluids and gases, from the upper internal environment U of the tank 14 and the roof 13. Further, the membrane 10 extends at least to the extremities E of the structural envelope or tank 14. A plurality of attachments 20 sealably attach inner and outer extremities 21,22 of the membrane 10 to the extremities E of the tank 14 for forming a reliable continuous membrane liner.

More particularly, the outer extremities of the membrane 22 are sealably attached to the inner surface 11 of the structural envelope or tank 14, while the inner extremities 21 are preferably attached to a center column 30 of the tank 14, both at a point below the roof 13 of the tank 14.

As shown in FIGS. 1, 2 and 4a,b-7, one method of attaching the extremities 21,22 of the membrane 10 to the inner surfaces 11 of the tank 14, among many, is an adaptation of mechanical attachments or seals 40 as described in co-pending U.S. patent application Ser. No. 10/740,409 and claiming priority of Provisional Patent Application 60/462,301 to Applicants, the entirety of which is incorporated herein by reference.

As shown in FIGS. 5 and 6, in addition, tanks 14 may contain other internal penetrations or connections 50 between the roof 13 of the tank 14 and the lower regions L of the tank 14, such as support columns, gage boards, or pipes and the like. The continuous geosynthetic membrane 10 is sealed to such penetrations or discontinuities 50 so as to maintain the impenetrable barrier provided by the membrane 10. This may be achieved by any number of sealing methods.

As shown in FIG. 4a, and in a preferred embodiment, the mechanical attachment or sealing system as incorporated above is used to further compress and seal the extremities 21, 22 of the membrane 10 therein at either the inner surfaces of the tank 14 or at a discontinuity 50 formed therein.

In a preferred embodiment of the invention, as shown in FIGS. 2-7, the system further comprises supporting elements 60 to support the suspended membrane 10 above the lower internal environment L of the tank 14. Such supporting elements 60 may consist of elements formed within the geosynthetic material of the membrane 10 itself that provide strength and integrity to the barrier, or external supports such as tensioned filaments, cables, or rigid supports, capable of supporting or lifting the weight of the geosynthetic membrane 10. While some geosynthetic materials contain filaments or structures designed to provide the material itself with sufficient lateral strength to withstand the lateral forces imposed when suspended, the use of external supporting elements 60, such as tension cables, or rigid supports, minimize stress on the material itself, and provide better control of the positioning and installation of the membrane 10 within the tank 14.

As shown in FIGS. 2, 3, 4b and 7, supporting elements 60 can be attached to the interior 11 of the tank 14, above or below the continuous membrane 10, using attachments means such as D-rings 61, eye bolts 62 and anchors 63 and the like, and the membrane 10 may either rest on the supporting elements 60, or be supported by the supporting elements 60 with various methods of attachment (not shown) from above. Optionally, cables 60 can be encased in protective sleeves 64, such as PVC pipes to protect the membrane 10 supported thereby and in contact therewith.

In another embodiment, shown in FIGS. 5-7, ventilation of the upper region U of the tank 14, above the geosynthetic membrane 10 and having access from outside the tank, ensures that minute permeations of gases or elements that pass through the geosynthetic membrane 10 do not accumulate above the geosynthetic membrane 10, resulting in corrosion and deterioration of the interior surface 12 of the roof 13. Such ventilation systems 70 may be simply apertures in the upper regions of the roof 13, allowing the flow of air, or any variety of active ventilation systems 70, such as those used in rigid roof structures for homes or other commercial buildings requiring ventilation.

An alternate embodiment, as shown in FIG. 6, further comprises a boot 80 typically made of liner material, to seal discontinuities 50 within the tank roof 13 that penetrate the membrane 10. The boot is welded or similarly attached to the membrane 10 at the penetration to the membrane 10, and is mechanically sealed or attached to the roof 13 or discontinuity 50. The boot 80 provides a continuously sealed membrane 10 about the discontinuity 50, preventing the discontinuity 50 and upper tank region U from corrosion or damage from tank liquids, gases, or condensates.

In use, as shown in FIG. 8 and 9, the system for installing a roof liner of membrane 10 comprises attaching and sealing the membrane 10 adjacent the roof 13 at an attachment 40 on the inner surface of the tank 14 or around a discontinuity 50 on the roof 13, attaching supporting elements 60 within the interior of the tank 14 and typically at one extremity E or about a center support 30, raising the support elements 60 and the membrane 10 to the tanks opposing extremity E or to the periphery at the inner surface 11, securing the supporting elements 60 to the tank's extremity and sealing the membrane 10 to the tank's inner surface 11.

Claims

1. A system for protecting an interior surface of a roof of a structural envelope from fluids contained within a lower region of the structural envelope comprising:

a continuous and impermeable geosynthetic membrane suspended within the structural envelope to separate the roof from the lower region of the structural envelope; and

a plurality of attachments positioned adjacent the roof and at the inner surface of the structural envelope for sealingly attaching the membrane thereto.

2. The system as described in claim 1 further comprising:

supporting elements attached to the inner surface of the structural envelope for supporting the membrane suspended therein.

3. The system as described in claim 2 wherein the supporting elements are cables.

4. The system as described in claim 2 wherein the supporting elements are positioned below the membrane.

5. The system as described in claim 2 wherein the supporting elements are positioned above the membrane and the membrane is attached thereto.

6. The system as described in claim 1 further comprising vents formed in the roof for providing ventilation to an upper portion of the structural vessel formed above the membrane.

7. The system as described in claim 1 wherein the membrane further comprises inner and outer extremities and wherein the plurality of attachments are positioned at the inner surface of an extremity of the structural envelope adjacent the roof and at a center column for sealably attaching the inner and outer extremities of the membrane thereto and for suspending the membrane therebetween.

8. The system as described in claim 7 further comprising:

supporting elements attached to the inner surface of the extremity of the structural envelope and at the center column for supporting the membrane suspended therebetween.

9. The system as described in claim 8 wherein the supporting elements are cables.

10. The system as described in claim 8 wherein the supporting elements are positioned below the membrane.

11. The system as described in claim 8 wherein the supporting elements are positioned above the membrane and the membrane is attached thereto

12. The system as described in claim 7 further comprising vents formed in the roof for providing ventilation to an upper portion of the structural vessel formed above the membrane.

13. A method of protecting an interior surface of a roof of a structural envelope from fluids contained within a lower region of the structural envelope comprising the steps of:

providing a continuous and impermeable geosynthetic membrane;

providing a plurality of attachments positioned adjacent the roof and at the inner surface of the structural envelope for sealingly attaching the membrane thereto; and

suspending the membrane from the attachments within the structural envelope to separate the roof from the lower region of the structural envelope.

14. The method as described in claim 13 and prior to suspending the membrane from the attachments, further comprising the steps of:

providing supporting elements for supporting the membrane;

attaching the supporting elements to the inner surface of the structural envelope at least one extremity of the envelope;

raising the supporting elements and the membrane for attachment to at least the opposite extremity of the envelope for suspending and supporting the membrane therein.

15. The method as described in claim 13 wherein the membrane further comprises inner and outer extremities and wherein the plurality of attachments are positioned at the inner surface of an extremity of the structural envelope adjacent the roof and at a center column for attaching the inner and outer extremities of the membrane thereto and for suspending the membrane therebetween.