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WO1996008427A1 - Joint d'etancheite souple pour toits flottants de cuves de stockage - Google Patents

Joint d'etancheite souple pour toits flottants de cuves de stockage Download PDF

Info

Publication number
WO1996008427A1
WO1996008427A1 PCT/US1994/013814 US9413814W WO9608427A1 WO 1996008427 A1 WO1996008427 A1 WO 1996008427A1 US 9413814 W US9413814 W US 9413814W WO 9608427 A1 WO9608427 A1 WO 9608427A1
Authority
WO
WIPO (PCT)
Prior art keywords
seal
elastic member
sealing surface
fluoropolymer film
floating roof
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/US1994/013814
Other languages
English (en)
Inventor
James G. Vana, Jr.
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
WL Gore and Associates Inc
Original Assignee
WL Gore and Associates Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by WL Gore and Associates Inc filed Critical WL Gore and Associates Inc
Priority to AU12988/95A priority Critical patent/AU1298895A/en
Publication of WO1996008427A1 publication Critical patent/WO1996008427A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
    • B65D88/00—Large containers
    • B65D88/34—Large containers having floating covers, e.g. floating roofs or blankets
    • B65D88/42—Large containers having floating covers, e.g. floating roofs or blankets with sealing means between cover rim and receptacle
    • B65D88/50—Large containers having floating covers, e.g. floating roofs or blankets with sealing means between cover rim and receptacle with resilient foam or stuffed seal

Definitions

  • the present invention relates to sealing devices, and more particularly seals used in sliding junctions between components, such as between an inner tank wall of a storage tank and a floating roof.
  • Storage tanks of chemicals and petroleum products are often designed with a floating roof that covers the surface of the product in order to reduce the loss of product through evaporation and to prevent product contamination from ambient weather conditions.
  • the floating roof is typically a rigid metal platform with an outer diameter smaller than the inner diameter of the tank resulting in an annular space, or "rim space,” between the floating roof and the inner tank wall. It is common practice to provide a seal for the rim space, which otherwise could be a major source of evaporation loss. Evaporation loss is a particular concern in large tanks used to store volatile chemicals and petroleum products.
  • sealing devices are generally made of polymeric members or a combination of thin metallic and polymeric members since they are flexible and will easily conform to the curved surface of an inner tank wall.
  • the ability of a polymeric member to conform to the inner tank wall to prevent gaps and paths for vapor leaks under harsh chemical and environmental conditions is the primary challenge in the design of the seals. Difficulties inherent in developing an effective seal under these conditions has resulted in a wide variety of seal designs.
  • One existing sealing device includes a flexible metal shield that is mounted to the upper perimeter of the floating roof and extends diagonally upwardly toward the inner wall of the tank, as described in United States Patent 4,308,968.
  • This device employs a yieldable polymeric member, or "wiper blade,” mounted on the end of the shield and cantilevered for engaging and pressing against the inner tank wall.
  • the wipers are designed to be relatively free flexing so as to conform to the continuous inner tank wall of a welded tank. This is accomplished by providing breaks in each wiper which are spaced apart along the length thereof and yet staggered relative to the breaks in the other wiper seals to seal the rim space.
  • the present invention comprises an improved flexible seal for use in sliding junctions, such as those found in the space between a floating roof of a storage tank and an inner periphery of the tank wall.
  • the seal comprises an inner sheet of a thin, flexible, elastic member that provides the elastic forces necessary for proper sealing between the seal and the inner tank wall.
  • the inner elastic member is covered with, and bonded to, a thin layer of a conductive fluoropolymer member, which provides the chemical resistance to a wide range of chemical additives.
  • the thin layer of conductive polymer may or may not also cover the edges of the inner elastic member.
  • the fluoropolymer used in the present invention is conductive so as to dissipate any buildup of static electrical charges caused by friction between the seat and the inner tank wall during normal operation.
  • static drain strips may be provided around the circumference of the roof structure to provide metal-to-metal contact from the floating roof to the electrically grounded tank wall.
  • the seal may be mounted directly to the upper portion of the roof structure and pushed up against the inner periphery of the tank wall in a cantilevered position.
  • the seal may also be mounted to an intermediate spring member which allows greater spring forces to be applied to the seal, as well as allowing a larger rim space between the floating roof and the inner tank wall.
  • the dimensions of the seal are designed such that the seal will remain flexible to conform to the tank inner tank wall yet maintain structural rigidity to provide a satisfactory force against the inner tank wall when in a cantilevered position. Since the frictional forces between the seal of the invention and the inner tank wall are significantly lower than presently available seals, the seal of the present invention is able to contact a larger surface area of the tank wall by increasing the span dimension of the seal relative to the dimension of the rim space. This larger area of surface contact allows the seal to remain cantilevered in one vertical direction, sliding against the inner tank wall independent of the direction of the movement of the floating roof. This eliminates the highly stressful flipping action which occurs with current seals.
  • Figure 1 is an isometric view of a seal of the present invention, showing the outer thin fluoropolymer layer covering two sides of the inner elastic member;
  • Figure 2 is an isometric view of a seal of the present invention, showing the outer thin fluoropolymer layer covering two sides and one edge of the inner elastic member;
  • Figure 3 is an isometric view of a seal of the present invention, showing the outer thin fluoropolymer layer covering two sides and two edges of the inner elastic member;
  • Figure 4 is a cross-sectional view of a seal of the present invention mounted directly to a floating roof by bolting;
  • Figure 5 is a cross-sectional view of another embodiment of a seal of the present invention mounted to an intermediate spring member
  • Figure 6 is an isometric view of still another embodiment of a seal of the present invention, showing a modified, enlarged outer edge.
  • the present invention is an improved seal for mounting in a sliding connection between two components, such as a flexible seal mounted between a floating roof and a side wall in a chemical storage tank.
  • Figure 1 shows an isometric view of a seal 10 of the present invention.
  • the seal 10 comprises an inner elastic member 12 covered with and bonded to a thin conductive fluoropolymer layer 14 on its first surface 16 and its second surface 18.
  • the preferred inner elastic member 12 comprises a polyurethane membrane bonded directly to the conductive fluoropolymer film 14 by applying heat and pressure.
  • the composite material so formed provides flexible elastic properties and resistance to chemical attack.
  • the inner elastic member preferably comprises a sheet of polyester-type polyurethane measuring between 25 and 1 mm or less in thickness (and more preferably between 1 and 3 mm), and between 17 and 38 cm in width.
  • the inner elastic member 12 may comprise any other suitable form of an elastic polymer material, such as natural rubber, polyester elastomer, or foamed polyurethane.
  • a thin sheet of metal with elastic properties may likewise be used.
  • the precise thickness of the elastic member 12 and the fluoropolymer layer 14 are chosen to provide the necessary cantilevered force when deflected against a sealing surface, yet remaining flexible to conform to any curvature or irregularities in the sealing surface in order to provide a tight seal.
  • a suitable fluoropolymer film 14 is a polytetrafluoroethylene film, such as that made in accordance with United States Patent 3,953,566 to Gore, incorporated by reference. More preferably, the film comprises a densified polytetrafluoroethylene material in accordance with United States Patent Application Serial Number 932,441, filed August 19, 1992, allowed, incorporated by reference.
  • the film should have the following characteristics: a high tensile strength, ideally on the order of about 68.9 MPa or above; tear resistance; fatigue resistance; and low permeability to water and gases.
  • the preferred film 14 comprises a thickness of between 0.1 and 0.5 mm.
  • the film 14 may be mounted to the elastic member 12 in any suitable manner, including bonding under a heat of about 190 to 210°C and a pressure of between 0.680 to 1.7 MPa.
  • Other suitable bonding methods may include use of an adhesive layer.
  • An important additional property of this material is its very low coefficient of friction, allowing the seal 10 to slide freely along its contact surfaces.
  • the seal 10 electrically conductive so as to dissipate static electrical charges that can be generated by the sliding movement of the seal within the joint.
  • the tanks are grounded for the safe dissipation of such charges, but an electrical path is still needed to ground charges generated in the floating roof structure.
  • the fluoropolymer film 14 includes electrically conductive elements therein to form this electrical pathway. For instance, a high strength
  • PTFE film may be form that is carbon filled, as described in co-pending United States Patent Application No. 932,441.
  • This material comprises a redensified in addition to carbon, other electrically conductive fillers may include various metal particles, and metal oxides.
  • Other conductive fluoropolymer materials suitable for use in the present invention may include films of conductive ethylenetetrafluoroethylene, conductive perfluoroalkoxy, or conductive fluorinated ethylene propylene.
  • FIG. 2 Another embodiment of the seal 10 of the present invention is shown in Figure 2.
  • the inner elastic member 12 is covered with the thin conductive fluoropolymer layer 14 on both sides 16, 18 and along at least one edge 20.
  • This preferred form of the present invention provides a more complete sealing of the elastic member 12 by protecting the elastic member from chemical attack along its edge. Additionally, due to the low coefficient of friction of the fluoropolymer coating of the present invention, the seal of the present invention slides easily along a sealing surface and is not prone to
  • FIG. 4 This embodiment of the seal 10 of the present invention is shown in a mounted orientation in Figure 4. As is shown, the seal 10 is attached to a floating roof structure 22 by conventional means, such as with a series of bolts 24 placed through openings 26, 28 in the seal. Reinforcement plates 30 and nuts 32 may be used to retain the seal in tight contact with the roof structure
  • the seal 10 is cantilevered against an inner surface 34 of a tank wall 36 in the manner shown as the roof structure 22 moves in a downward direction.
  • the covering of fluoropolymer layer 14 over the seal's edge 20 protects against attack from chemicals and vapors in vapor space 38.
  • the preferred method of manufacture of this embodiment of the present invention is to fold the film of conductive fluoropolymer 14 in half over the elastic member 12, around the fluoropolymer edge 20.
  • the film 14 is sealed in this position by applying heat and pressure to bond both flat surfaces 16, 18 and the long edge 20 to the elastic member 12.
  • the seal of the present invention 10 is formed under a vacuum while pressure and the heat is applied so as to remove any outgassing volatiles. This provides a more homogenous inner elastic member.
  • Another preferred construction of the present invention is also illustrated in Figure 2. In this instance, there is provided a gradient thickness of the inner elastic member 12, whereby the thickness decreases approaching outside edge 20. This produces a seal 10 with a thicker section 40 on the bolt side of the seal and a thinner section 42 on the outside edge 20 side of the seal. As is shown in Figure 4, the thicker section 40 attaches to the floating roof 22 to provide a larger cantilever force against the wall 36, while the thinner section 42 provides flexibility to conform against the curved inner tank wall 34.
  • the seal 10 comprises an inner elastic member 12 covered with a thin fluoropolymer layers 14a, 14b on surfaces 16, 18.
  • the fluoropolymer layers 14a, 14b extend off the elastic member 12 on at least one side edge 44 to directly attach to each other along section 46, as shown.
  • the outer edge 20 is again sealed by wrapping the fluoropolymer layer 14 around edge 20 of the elastic layer 12. The advantage of this construction is that the side edges of the elastic layer 12 are likewise protected from chemical attack.
  • Figure 4 is mounted directly to a floating roof 22.
  • the seal 10 bends into a radius as it is pushed up onto the inner tank wall 34, the elastic forces provided by the inner elastic member 12 allow the seal 10 to adequately press against the inner tank wall 34, forming an effective barrier against evaporating volatiles as well as shielding the fluid in the tank from outside environmental influences, such as moisture.
  • the span of the seal of the invention is defined as the distance from one long edge 20 to the other long edge 48 of the seal 10 when laid flat.
  • the span of the seal 10 can be made sufficiently large so as to allow for large variations in the distance "R" 50 between the inner tank wall 34 and the floating roof 22.
  • Figure 5 shows another method of mounting the seal 10 of the present invention.
  • the seal 10 is mounted to an intermediate spring member 52.
  • a continuous flexible film 54 is provided on either the interior or exterior of the spring member 52.
  • Spring member 52 is generally a thin gage metal shield that is attached to a periphery floating roof 58 and is bent in a diagonal towards inner tank wall 60 wherein seal 10 will be attached and forced against the tank wall by the spring properties of the member 52.
  • the relatively free flexing of the spring member or members 52, conforming to the continuous inner tank wall 60, is provided by breaks in each spring member spaced apart along the length thereof and yet staggered relative to the breaks in the other spring member components to seal the rim space.
  • Flexible film 54 is typically a thin non-permeable film which is continuous around the rim space to seal the gaps created by the staggered metal spring members 52. This method of mounting of the seal 10 allows even greater distances "R" 62 between the floating roof 58 and the inner tank wall 60. In addition, this method of mounting provides an additional positive force of the seal 10 against the tank wall 60.
  • the seal 10 shown in Figure 5 may be mounted to spring member component 52 by using any of suitable clamp means known in the art or through the use of high-strength adhesives or similar materials.
  • the spring member 52 and film 54 may be mounted to the floating roof by bolting, clamping, or adhesion as well.
  • Figure 6 is still another embodiment of the seal 10 of the present invention.
  • the seal 10 includes an outer edge 64 that is enlarged to form a "bulb" along its length. This outer edge 64 is mounted in contact with the sealing surface so as to more easily move over welded seams and other protrusions along a sealing surface.
  • the sealing of a tank may be accomplished by using a number of seals of the present invention. It may be desirable to space each seal so as to provide an overlap with the adjacent seals. The complete rim space may then be effectively sealed without danger of the seals flipping and allowing openings for vapors to escape.
  • the fluoropolymer layer gives superior chemical resistance to prevent degradation due to chemical additives, while being conductive to prevent dangerous buildup of electrostatic charges between the inner tank wall and the floating roof.
  • the seal of the present invention may have applicability to a wide variety of sealing needs, particularly where a dynamic seal must be produced between components parts that move relative to one another.
  • Other suggested uses for the seal of the present invention where the seal mounts in dynamic contact against a sealing surface include: rotary vane pumps, sewage treatment slurry tanks, etc.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Gasket Seals (AREA)

Abstract

Joint d'étanchéité amélioré (10) destiné à être utilisé pour prévenir les fuites dans une variété d'applications où deux composants se déplacent l'un par rapport à l'autre dans une relation de coulissement. Le joint d'étanchéité (10) de la présente invention comporte un élément interne élastique (12) recouvert d'un film en fluoropolymère (14) résistant aux produits chimiques. Ledit film protège l'élément élastique interne de l'attaque chimique et présente également un faible coefficient de friction pour un joint d'étanchéité coulissant amélioré. Le joint d'étanchéité de la présente invention est particulièrement utile dans des applications tels que les toits flottants sur des cuves de stockage de produits chimiques.
PCT/US1994/013814 1994-09-12 1994-12-02 Joint d'etancheite souple pour toits flottants de cuves de stockage Ceased WO1996008427A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU12988/95A AU1298895A (en) 1994-09-12 1994-12-02 Flexible seal for floating roofs of storage tanks

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US30475394A 1994-09-12 1994-09-12
US08/304,753 1994-09-12

Publications (1)

Publication Number Publication Date
WO1996008427A1 true WO1996008427A1 (fr) 1996-03-21

Family

ID=23177849

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1994/013814 Ceased WO1996008427A1 (fr) 1994-09-12 1994-12-02 Joint d'etancheite souple pour toits flottants de cuves de stockage

Country Status (2)

Country Link
AU (1) AU1298895A (fr)
WO (1) WO1996008427A1 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111186649A (zh) * 2018-11-14 2020-05-22 中国石油化工股份有限公司 外浮顶储罐用超双疏表面的浮盘边缘密封装置及使用方法
TWI701201B (zh) * 2020-01-08 2020-08-11 璟鎧企業有限公司 內浮頂之環向密封裝置
CN111534030A (zh) * 2020-06-03 2020-08-14 河北澳科中意环保科技有限公司 一种聚四氟乙烯纤维膜及含有其的密封系统

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4308968A (en) * 1980-06-03 1982-01-05 H.M.T., Inc. Secondary seal for tank having floating roof
JPS5841076A (ja) * 1981-08-28 1983-03-10 横浜フオ−ムラバ−株式会社 タンクの浮屋根のシ−ル

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4308968A (en) * 1980-06-03 1982-01-05 H.M.T., Inc. Secondary seal for tank having floating roof
JPS5841076A (ja) * 1981-08-28 1983-03-10 横浜フオ−ムラバ−株式会社 タンクの浮屋根のシ−ル

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
DATABASE WPI Week 1683, Derwent World Patents Index; AN 83-37688 *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111186649A (zh) * 2018-11-14 2020-05-22 中国石油化工股份有限公司 外浮顶储罐用超双疏表面的浮盘边缘密封装置及使用方法
CN111186649B (zh) * 2018-11-14 2022-02-25 中国石油化工股份有限公司 外浮顶储罐用超双疏表面的浮盘边缘密封装置及使用方法
TWI701201B (zh) * 2020-01-08 2020-08-11 璟鎧企業有限公司 內浮頂之環向密封裝置
US11352201B2 (en) 2020-01-08 2022-06-07 Jing Kai Industrial Co., Ltd. Peripheral sealing assembly for an internal floating roof
CN111534030A (zh) * 2020-06-03 2020-08-14 河北澳科中意环保科技有限公司 一种聚四氟乙烯纤维膜及含有其的密封系统

Also Published As

Publication number Publication date
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