Receptacles – Closures – Floating closure
Reexamination Certificate
1998-12-18
2001-06-19
Newhouse, Nathan J. (Department: 3727)
Receptacles
Closures
Floating closure
C220S222000, C220S224000, C220S226000, C277S569000, C277S652000, C277S936000
Reexamination Certificate
active
06247607
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to seals for sealing the space between a floating roof and an inner tank wall within a storage tank for petrochemical or other liquid products.
2. History of the Prior Art
It is standard practice in the field of large storage tanks such as oil storage tanks having floating roofs to provide the floating roof with one or more seals. Such seals act to seal the space between the outer rim of the floating roof and the inner tank wall while at the same time allowing the floating roof to rise or drop as the height of the liquid product within the storage tank varies. Such seals are necessary in order to prevent harmful hydrocarbon vapors from escaping through the space between the floating roof and the inner tank wall and entering the atmosphere. For some applications, a single seal is installed on the floating roof so as to seal the space between the roof and inner tank wall. For other applications, a primary seal provides the main sealing function while a secondary seal disposed above the primary seal traps any vapors that may escape through the primary seal.
Seals for floating roofs within storage tanks can assume a variety of different configurations. Examples of the different possible configurations of floating roof seals are provided by U.S. Pat. No. 4,308,968 of Thiltgen et al., U.S. Pat. No. 5,078,293 of Lippiello, U.S. Pat. No. 5,103,992 of Lippiello et al. and U.S. Pat. No. 5,301,828 of McKay. Such patents are commonly assigned with the present application. The seals depicted by these patents assume various configurations, and typically utilize vapor barrier fabrics in conjunction with other materials. Several of the configurations utilize shoe seals which are suspended from the outer edge of the floating roof for disposition adjacent and biasing against the inner tank wall. A further example of a floating roof seal is provided by copending application Ser. No. 09/082,028 of Richard P. King et al., “Seal For Floating Roof Of Storage Tank”, which application is commonly assigned with the present application.
The floating roof seals described in the above-mentioned patents and application are capable of sealing the space between the floating roof and the inner tank wall effectively. However, there is a continuing need for floating roof seals that provide other options and alternatives in terms of design, fabrication and installation. Seals of relatively simple design and low cost may present particular advantages for many installations.
In the case of secondary seals mounted above primary seals for the floating roof, it would be desirable to provide such a seal of limited height so as to extend only a relatively small distance above the floating roof. This would provide the tank with increased storage capacity by increasing the maximum height to which the floating roof can rise. Such seals should be of relatively simple construction, and the light in weight. At the same time, such seals should be made of highly durable materials so as to require a minimum of maintenance and to provide a long service life. The seals must be water tight so as to keep rain water out of the liquid product within the tank. Where a vapor barrier fabric forms a part of the seals, the fabric should be disposed for ease of inspection and replacement when necessary, and should be oriented so as to shed rainwater which might otherwise collect thereon.
BRIEF DESCRIPTION OF THE INVENTION
The foregoing and other objects and features in accordance with the invention are accomplished by providing an improved secondary seal of low profile which is simply constructed of relatively few parts which are highly durable in nature. Such seals include the use of materials which are compatible with all products normally stored in floating roof tanks. The design of the seal is such as to keep rainwater out of the liquid product and to prevent collection of rainwater on the vapor barrier fabric which forms a part of the seal. The vapor barrier fabric is disposed for easy inspection, and replacement when necessary. The seal is light in weight and provides a long service life with a minimum of maintenance.
In low profile secondary seals according to the invention, a plurality of support plates are mounted in spaced-apart relation along the outer rim of the floating roof so as to extend outwardly from first ends thereof to opposite second ends which are coupled to an elongated, continuous wiper assembly disposed at the inner tank wall. The support plates are resilient in nature, and are preferably made of material such as full hard stainless steel which has a memory such that it tends to assume and maintain a predetermined shape. As a result, the support plates resiliently bias the wiper assembly against the inner tank wall. The space between the outer rim of the floating roof and the wiper assembly is covered over and sealed by a vapor barrier fabric having a first edge coupled to the floating roof and an opposite second edge coupled to the wiper assembly. The vapor barrier fabric is supported by and is maintained in a desired orientation by a plurality of support straps mounted in spaced-apart relation along the outer rim of the floating roof between the support plates and so as to extend outwardly from first ends thereof at the floating roof to opposite second ends which coupled to the wiper assembly. Like the support plates, the support straps are preferably made of resilient material with a memory such as full hard stainless steel.
The first ends of the support plates, and the first edge of the vapor barrier fabric, are coupled to the outer rim of the floating roof by a holddown channel and bolts extending through the holddown channel and through the outer rim of the floating roof. The opposite edge of the vapor barrier fabric is clamped to the upper surface of the wiper assembly by an upper clamping angle secured to the wiper assembly by bolts extending through the wiper assembly. An opposite clamping angle is located at the underside of the wiper assembly.
In accordance with the invention, the second ends of the support plates are coupled to the wiper assembly to permit pivoting movement thereof relative to the wiper assembly. This maintains the wiper assembly in a desired orientation relative to the inner tank wall as the support plates move to different positions. The pivoting movement is provided for by portions of the bolts in the wiper assembly which extend below the wiper assembly and which are not threaded. These unthreaded portions of the bolts extend through slots in the support plates to enable pivoting movement of the wiper assembly relative to the slotted second ends of the support plates.
Movement of the wiper assembly along the inner wall of the tank is facilitated by a plurality of skid plates of angled configuration which are mounted in spaced-apart relation along the wiper assembly. Some of the skid plates are mounted on the top of the wiper assembly and extend upwardly therefrom, while still other skid plates are mounted at the underside of the wiper assembly and extend downwardly therefrom. The skid plates are coupled to the wiper assembly by the bolts extending through the wiper assembly. The skid plates are preferably made of resilient material having some memory, such as quarter hard stainless steel.
In accordance with the invention, the elongated wiper assembly is constructed so as to engage the inner tank wall in effective sealing fashion, and so as to resist wear so that maintenance thereof is minimized and the seal is provided with a long service life. The wiper assembly is comprised of a foam element which is wrapped in highly durable PTFE Teflon (Petro Flex) fabric. The foam element is a low density polyethylene foam of closed cell construction and which has a memory. The foam element has the outer surface thereof wrapped in the PTFE Teflon (Petro Flex) fabric which is very durable and which is chemically compatible with all products normally stored in the tank.
REFERENCES:
patent: 2790574 (1957-04-01),
HMT Inc.
Hogan & Hartson LLP.
Newhouse Nathan J.
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