US3900127A

US3900127A - Sealing assembly in tank

Info

Publication number: US3900127A
Application number: US420538A
Authority: US
Inventors: Karl Schwarz
Original assignee: Voestalpine AG
Current assignee: Voestalpine AG
Priority date: 1972-12-06
Filing date: 1973-11-30
Publication date: 1975-08-19
Anticipated expiration: 1992-08-19
Also published as: AT319145B; GB1428514A; DE2358636C3; DE2358636B2; IT1001046B; FR2210992A5; DE2358636A1

Abstract

The sealing assembly serves to seal an annular gap between a tank wall and a floating top of a tank. A flexible sealing skirt is sealed to the periphery of the floating top and bridges the annular gap. A resilient cover slopes down toward and is tightly secured to the top rim of the floating top. A plurality of peripherally spaced leaf springs are secured to the periphery of the floating top. Each of said leaf springs has diverging upper and lower resilient legs, which extend upwardly and downwardly, respectively, from said floating top toward said tank wall. Said upper legs have free ends, to which said resilient cover and an upper resilient profiled sealing member are secured and by which said upper profiled sealing member is forced into sealing engagement with said tank wall along a peripheral line thereof. Said lower legs have free ends, to which said sealing skirt and a lower resilient profiled sealing member are secured and by which said lower profiled sealing member is forced into sealing engagement with said tank wall along a peripheral line thereof.

Description

United States Patent 1191 Schwarz 1451 Aug. 19, 1975 SEALING ASSEMBLY IN TANK [75] Inventor: Karl Schwarz, Linz, Austria [73] Assignee: Vereinigte Osterreichische Eisenund Stahlwerke Alpine Montan Aktiengesellschaft, Linz, Austria [22] Filed: Nov. 30, 1973 [21] Appl. No.: 420,538

[30] Foreign Application Priority Data Dec. 6, 1972 Austria 10399/72 52 US. Cl. 220/216; 222/338 [51] Int. Cl. 865d 87/18 [58] Field of Search... 220/26 R, 26 E, 26 S, 26 SA, 220/216-222, 224, 227; 222/338, 342

Primary Examiner-Leonard D. Christian Attorney, Agent, or F irm-Kurt Kelman [57] ABSTRACT The sealing assembly serves to seal an annular gap between a tank wall and a floating top of a tank. A flexible sealing skirt is sealed to the periphery of the floating top and bridges the annular gap. A resilient cover slopes down toward and is tightly secured to the top rim of the floating top. A plurality of peripherally spaced leaf springs are secured to the periphery of the floating top. Each of said leaf springs has diverging upper and lower resilient legs, which extend upwardly and downwardly, respectively, from said floating top toward said tank wall. Said upper legs have free ends, to which said resilient cover and an upper resilient profiled sealing member are secured and by which said upper profiled sealing member is forced into sealing engagement with said tank wall along a peripheral line thereof. Said lower legs have free ends, to which said sealing skirt and 'a lower resilient profiled sealing member are secured and by which said lower profiled sealing member is forced into sealing engagement with said tank wall along a peripheral line thereof.

5 Claims, 5 Drawing Figures 3,9OUil27 ATENTED AUBI 91975 SiiIZT 2 OF 3 WJENTEU AUG 1 9 SHEET 3 0f m GI SEALING ASSEMBLY IN TANK This invention relates to an assembly for sealing an annular gap between a tank wall and a floating top of a large tank for mineral oil or the like, which assembly seal is resiliently urged against the tank wall and comprises a flexible sealing skirt which bridges the annular gap, and a cover, which has a profiled sealing portion contacting the tank wall and slopes down toward the top edge of the floating top and is secured there.

An assembly for sealing the annular gap between the floating top and the wall of a large tank for mineral oil or the like must prevent an ingress of precipitated water into the large tank and must prevent losses resulting from an evaporation of the stored liquid. The fulfilment of these requirements is rendered more difficult because the floating top can move laterally so that the annular gap cannot be expected to be constant. An additional difficulty is involved in the requirement that precipitated water must not collect directly at the tank wall in order to prevent a freezing of the sealing assembly to the tank wall. Such freezing of the sealing assembly to the tank wall would prevent the floating top from sliding up and down in response to fluctuations of the level of the stored liquid and might result in a destruction of the seal.

To alleviate these difficulties and to better fulfil the requirements to be met by such sealing assembly, the use of the known sealing assemblies having sheet metal elements in sliding contact with the tank wall has been discontinued. The inevitable inaccuracies in the manufacture, temperature changes and the inherent stiffness of the slidable sheet metal elements permit of a formation of gaps up to about millimeters between the tank wall and the slidable sheet metal elements associated with the floating top. These gaps adversely affect the dual seal and may permit high-viscosity stored material adhering to the tank wall to pass between the tank wall and the slidable sheet metal elements as the floating top subsides so that the floating top will be soiled when it rises thereafter. For this reason it has been attempted to provide a sealing assembly which is resiliently urged against the tank wall and which in case of an increase in the size of the annular gap between 'the tank wall and the floating top as a result of temperature changes or lateral movements of the top can adapt itself to the changed width of the gap so that a sealing contact with the tank wall is always ensured. These sealing assemblies comprise a foam member, which is urged against the tank wall as a result of the resiliency of the foam member itself or by leaf springs, and is surrounded by a sealing skirt, which is tightly joined to the floating top and urged into sealing contact with the latter by the foam member. To ensure a particularly effective and uniform pressure contact, leaf springs are used which comprise two diverging spring legs which extend upwardly and downwardly, respectively, from the floating top toward the tank wall, and a web, which connects the spring legs and is firmly secured to the periphery of the floating top. To enable an adaptation to changes in the width of the gap, only one leg of each spring is firmly joined to the sealing member, which is urged into surface contact with the tank wall, whereas the other spring leg is freely slidable on the sealing member. In such known sealing assemblies, the surface contact between the sealing member and the tank wall does not entirely prevent a soiling of the sealing means by stored material adhering to the tank wall, and a freezing of the sealing skirt to the tank wall cannot be prevented because water may accumulate between the tank wall and the edges of the sealing member when the same have been flexed away from the tank wall to facilitate the sliding movement. As a result, the seal may be destroyed by a movement of the floating top.

It has been attempted to avoid this disadvantage by the provision of a separate cover for the annular gap. This cover has a profiled sealing portion in contact with the tank wall and slopes down toward and is secured to the top edge of the floating top and is mounted on the floating top for a limited angular movement and is urged by its own weight against the tank wall even during a movement of the floating top. Whereas this known design reduces the danger of a freezing of the seal to the tank wall, it cannot entirely preclude such freezing because the force by which the sealing portion at the outer edge of the cover is urged against the tank wall is determined only by the relatively light weight of the cover. Besides, the design is highly expensive and does not permit of an adjustment or readjustment of the forces by which the cover and the seal are urged against the tank wall.

In another known design the annular gap between the floating top and the tank wall is covered by spring steel plates, which are secured to the floating top and extend upwardly and downwardly, respectively, from the floating top toward the tank wall in accordance with conical frustums and are interconnected by elastic connectors in a ring. The outer edges of these plates are bent back away from the tank wall in order to facilitate the sliding on the tank wall. This design results in the formation of an undesired trough, in which precipitated water can collect, and the plates which are inherently. stiff as a result of their shape are further stiffened so that they cannot well adapt themselves to changes in the width of the gap.

To avoid particularly an ingress of water between the slidable sheet metal elements of the sealing assembly and the tank wall, it has already been attempted to secure a profiled sealing member to the top edge of the slidable sheet metal elements and to provide a large number of leaf springs, which urge the top edge portion of said profiled sealing member against the tank wall. The main disadvantage of said arrangement resides in that the leaf springs bear on the slidable sheet metal elements which constitute the main seal so that the leaf springs reduce the contact pressure force and the sealing action of these slidable sheet metal elements. Besides, the contact pressure forces of the additional and main seals cannot be adjusted. To facilitate the sliding of the profiled sealing member over protruding horizontal seam welds, joints between tank wall sections or the like, slidable fingers formed of wire are secured to the profiled sealing member on that side thereof which is remote from the tank wall. These fingers protrude beyond the profiled sealing member and their free ends protruding toward the tank wall are similar to a skid. These known slidable fingers have the disadvantage that they cannot always easily slide over seam welds or joints because a re-entrant recess exists between that surface of the profiled sealing member which contacts the tank wall and the skids formed by the slidable fingers and because in case of an angular movement of the profiled sealing member caused by a movement of the top the fingers disengage the profiled sealing member from the tank wall owing to the vertical distance between the skid protruding toward the tank wall and the profiled sealing member.

It is also known to provide a profiled sealing member having horizontal ribs extending toward the tank wall, to urge said profiled sealing member against the tank wall be radially displaceable, spring-loaded backing arms, and to provide a flexible skirt, which covers the gap between the profiled sealing member and the floating top. The backing arms carry backing rollers, which roll on the tank wall and limit the contact pressure applied to the profiled sealing member because they prevent an approach beyond a minimum clearance Be cause the sealing member extends horizontally and the backing arms are exposed to the weather, the tightness of the seal may be strongly reduced by a formation of ice. Besides, a comparatively large, undesired gas space exists between the sealing means, the floating top, the tank wall, and the stored liquid.

It is an object of the invention to avoid these disadvantages and to provide an assembly which enables a sealing of the annular gap between a tank wall and a floating top of a large tank and which with simple means ensures the required tight seal also in case of changes of the annular gap and precludes a risk of damage by a freezing of the seal to the tank wall. Besides, the contact pressure force exerted on the tank wall should be adjustable and readjustable so that the cover can be adapted to existing conditions. It is also desired to eliminate the risk of a catching of the seal on protruding horizontal seam welds or the like whereas the sealing action should be preserved.

In an assembly of the kind described first hereinbefore, this object is accomplished in that a large number of leaf springs are secured to the periphery of the floating top and comprise upper and lower diverging resilient legs, which extend upwardly and downwardly, respectively, from the floating top toward the tank wall, the cover and an upper resilient profiled sealing member are secured to the free ends of the upper resilient legs, and the latter urge said upper profiled sealing member against the tank wall along a peripheral line thereof, and the sealing skirt and a lower resilient profiled sealing member are secured to the free ends of the lower resilient legs, and the latter urge said lower profiled sealing member against the tank wall along a peripheral line thereof. The prestressed leaf springs, which force the resilient endless profiled sealing members against the tank wall, easily compensate changes in the width of the annular gap so that a tight seal is always ensured. This seal is particularly effective because each profiled sealing member is forced against the tank wall along a peripheral line, different from the surface contact in the known arrangements. Because the cover also tightly contacts the tank wall and owing to its flexibility can easily follow the movements of the floating top, precipitated water cannot enter the annular gap so that the sealing assembly cannot freeze to the tank wall. Precipitated water will be diverted toward the floating top by the cover, which slopes down toward the top edge of the floating top.

According to a further feature of the invention, each leaf spring has a web, which connects the two diverging legs and has a portion which is slightly spaced from that surface of the floating top to which the spring is secured, and a readjustable fixing screw is inserted into said web portion. These leaf springs according to the invention facilitate an adjustment and readjustment of the initial stress of the legs of the leaf springs because the fixing screw may be used to stress that web portion which is spaced from the mounting surface of the floating top so that the initial stress of the leaf spring can be adjusted. The closer this web portion is forced toward the mounting surface, the higher will be the initial stress.

To ensure a contact of each resilient profiled sealing member with the tank wall along a peripheral line, it is a feature of the invention that the profiled sealing members are strip-shaped and comprise jawlike portions, which embrace the ends of the resilient legs and the outer edge of the sealing skirt or of the cover and are provided on their outside in known manner with protruding longitudinal ribs or the like. Because the profiled sealing members have jawlike portions which embrace the ends of the resilient legs and the outer edge of the sealing skirt or the cover, the profiled sealing members have a curved surface facing the tank wall and provided with longitudinal ribs or the like, at least one of which is forced against the tank wall regardless of the position assumed by the resilient legs in dependence of the position of the floating top. Whereas changes of the width of the annular gap will result in a rotation of the legs of the leaf springs and in a rotation of the profiled sealing members, these rotations will not influence the effectiveness of the seal because the longitudinal ribs or the like are provided.

In a further embodiment of the invention, at least part of the diverging resilient legs of the leaf springs carry slidable fingers, known per se, which are disposed on that side of the profiled sealing member which faces the tank wall and tightly engage that portion of the profiled sliding member which contacts the tank wall and are bent away from the tank wall at least by an angle which corresponds to the largest angular movement of the resilient legs. When a horizontal floating movement of the top causes a pivotal movement of the resilient legs about a substantially horizontal axis, the profiled sealing member and the slidable fingers will necessarily follow this pivotal movement but the profiled sealing member will always remain in contact with the tank wall because the slidable fingers snugly hug and contact the profiled sealing member where it contacts the tank wall. I

Particularly simple and desirable slidable fingers will be obtained if that portion of the slidable fingers which is bent away from the tank wall and around the profiled sealing member has a straight sub-portion which extends from the profiled sealing member and an end portion which is further bent away from the tank wall. When the resilient legs have performed their largest angular movement, the straight sub-portion of the slidable fingers will just contact the tank wall so that the end portion which is further bent away from the tank wall forms the skids which facilitate the sliding over protruding horizontal seam welds or the like. In case of a smaller inclination of the resilient leg relative to the tank wall, the straight sub-portion of the slidable finger will protrude from the tank wall at a corresponding angle and said straight sub-portion will then form the skid. It is thus ensured in all position of the spring legs that the profiled sealing member contacts the tank wall and the sliding fingers enable a sliding of the profiled sealing member over protruding seam welds or the like during a vertical movement of the roof.

An embodiment of the invention is shown diagrammatically and by way of example on the accompanying drawings, in which I I i FIG. 1 is a transverse sectional view'sho'wing an assembly according to the invention for sealing an annularlgap between a tank wall and a floating top of a large tank,

FIG. 2 is a top plan view showing said assembly with thecover partly removed,

FIG. 3 is a transverse sectional view showing on a larger scale a profiled sealing member according to the invention, i

FlG.,4 is a transverse sectional view showing a profiled sealing member provided with slidable fingers arranged in accordance with the invention, and

FIG. 5 is a view taken in a horizontal direction and showing a profiled sealing member provided with a slidable finger.

A large number of leaf springs 2, of which only one is shown in FIG. 1 for the sake of clarity, are secured to the periphery of a floating top 1 of a large tank. Each leaf spring 2 has two diverging

resilient legs

4 and 5, which extend upwardly and downwardly, respectively, and toward a wall 3 of the tank. The upper resilient legs 4 carry at their free ends a cover 6 and an upper resilient profiled sealing member 8, which is urged by the leaf springs 2 against the tank wall 3. The lower resil ient legs 5 carry at their free ends a sealing skirt 7 and a lower resilient profiled sealing member 9, which is urged by the leaf springs 2 against the tank wall 3. Each profiled sealing member 8 is strip-shaped and has jawlike portions which embrace the ends of the

spring legs

4 or 5 and the outer edges of the cover 6 or of the sealing skirt 7 so that tight joints between the respective elements are ensured. Rivets 9 are provided to hold the elements together. Each profiled sealing member 8 is provided on its outside with protruding longitudinal ribs 10, which enable a pressure contact with the tank wall along a peripheral line thereof so that a particu larly good seal is ensured. Besides, the ribs 10 will scrape off any stored material which may adhere to the tank wall 3 so that the sealing member is not likely to be soiled. To reliably avoid such soiling, additional scrapers, known per se, could be secured to the floating top for a coarse cleaning of the tank wall whereas the profiled sealing members would then provide for an aftercleaning.

Each leaf spring 2 has a web, which connects the diverging

legs

4 and 5 and comprises a portion 11, which is spaced from that surface of the floating top to which the spring is secured. A readjustable fixing screw 12 is inserted in said web portion and can be tightened to move the web portion 11 closer to the mounting surface of the floating top so that the initial stress of the

leaf spring legs

4 and 5 is increased. The fixing screws 12 thus permit of an easy adjustment and readjustment of the initial stress in adaptation to different conditions.

The flexible cover 6 slopes down from the tank wall 3 to the top edge of the floating top 1 and is tightly secured there and diverts any arriving precipitated water to the floating top so that precipitated water cannot enter the annular gap between the floating top 1 and the tank wall 3. The effective seal which is always required for this purpose will be ensured even in case of changes of the annular gap because a rotation of the leaf spring legs due to a change of the annular gap will be followed by the profiled sealing member so that the protruding longitudinal ribs 10 always ensure that at least one of the longitudinal ribs contacts the tank wall regardless of the angular position of the profiled sealing member and the resilient leg.

The profiled sealing members may be made, e.g., of hard rubber, the hardness of which must be selected so that they resist abrasion which is due to the roughness of the tank and to welded or riveted joints in the tank wall. i v i i i To facilitate a sliding over any protruding horizontal seam welds 13 or the like, at least some resilient legs are provided with slidable fingers 14, which are secured by the rivets 9 to the profiled sealing member on that side thereof which faces the tank wall These slidable fingers consist preferably of thin sheet, metal or wire and are bent away from the tank wall 3 and around the profiledsealing member 8 by an angle which corresponds to the largest angular movement of the spring legs 4 and with their bent portion tightly contact the profiled sealing member. Because theslidable fingers consist of thin sheet metal, they prevent adisengagement of the profiled sealing member from the tank wall adjacent ot the fingers because the resiliency of the profiled sealing member enables the fingers to be forced into the profiled sealing member by means of the rivets.

That portion of each slidable finger 14 which is bent away from the tank wall 3 and around the profiled sealing member 8 has a straight sub-portion 15, which extends from the profiled sealing member 8 and an end portion 16, which is further bent away from the tank wall.

When the floating top moves horizontally away from the wall 3 of the large tank, the

legs

4 and 5 of the leaf spring will be pivotally moved relative to each other under the initial stress. This pivotal movement will be followed by the profiled sealing members 8 and by the slidable fingers 14 whereas the profiled sealing members will not disengage the tank wall. During a vertical movement of the floating top, the straight sub-portion 15 of each slidable finger shown in FIG. 4 will act as a skid whereas after the largest angular movement of the resilient leg this portion 15 will engage the tank wall 3 and the end portion 16 which is further bent away must perform this function.

A forcing of the slidable fingers 14 into the profiled sealing member 8 by the rivets 9 to an excessive depth would result in a gap in the sealing assembly. To prevent a forcing to such excessive depth, the slidable fin gers 14 are provided adjacent to the rivets 9 with thrust washers 17, which ensure that the clamping forces will be distributed as required.

What is claimed is:

1. In a large tank having a tankwall and a floating top which has a top rim and defines an annular gap with said tank wall, the provision of an assembly for sealing said annular gap, which assembly comprises a flexible sealing skirt, which is sealed to the periphery of said floating top and bridges said annular p a flexible cover, which slopes down toward and is tightly secured to the top rim of said floating top, upper and lower resilient profiled sealing members,

and

a plurality of peripherally spaced apart leaf springs,

which are secured to the periphery of said floating top,

each of said leaf springs having diverging, upper and lower resilient legs, which extend upwardly and downwardly, respectively, from said floating top toward said tank wall,

said upper legs having free ends, to which said cover and said upper profiled sealing member are secured and by which said upper profiled sealing member is forced into sealing engagement with said tank wall along a peripheral line thereof,

said lower legs having free ends, to which said sealing skirt and said lower profiled sealing member are secured and by which said lower profiled sealing member is forced into sealing engagement with said tank wall along a peripheral line thereof.

2. An assembly as set forth in claim 1, in which each of said leaf springs has a web which connects said two legs and bears on a surface portion of said floating top,

said web has a web portion spaced from said surface portion, and

an adjustable fixing screw extends through said spaced web portion and is adjustably fixed to said surface portion.

3. An assembly as set forth in claim 1, in which each of said profiled sealing members is strip-shaped and has jawlike portions,

said jawlike portions of said upper profiled sealing member embrace said free ends of said upper resilient legs and the outer edge of said cover,

said jawlike portions of said lower profiled sealing member embrace said free ends of said lower resilient legs and the outer edge of said sealing skirt, and

said profiled sealing members are provided on their outside with protruding longitudinal ribs.

4. An assembly as set forth in claim 1, in which said resilient legs are pivotally movable up to a predetermined angle, and

at least part of said resilient legs carry slidable fingers, which are disposed on that side of the associated profiled sealing member which faces the tank wall and have a portion which is angled from said tank wall at an angle which is at least as large as said predetermined angle and extends around and tightly contacts the associated profiled sealing member where it is nearest to the tank wall.

5. An assembly as set forth in claim 4, in which said portion of each of said slidable fingers has a straight sub-portion extending from the profiled sealing member and an end portion which is angled from said subportion toward said profiled sealing member.

Claims

1. In a large tank having a tankwall and a floating top which has a top rim and defines an annular gap with said tank wall, the provision of an assembly for sealing said annular gap, which assembly comprises a flexible sealing skirt, which is sealed to the periphery of said floating top and bridges said annular gap, a flexible cover, which slopes down toward and is tightly secured to the top rim of said floating top, upper and lower resilient profiled sealing members, and a plurality of peripherally spaced apart leaf springs, which are secured to the periphery of said floating top, each of said leaf springs having diverging, upper and lower resilient legs, which extend upwardly and downwardly, respectively, from said floating top toward said tank wall, said upper legs having free ends, to which said cover and said upper profiled sealing member are secured and by which said upper profiled sealing member is forced into sealing engagement with said tank wall along a peripheral line thereof, said lower legs having free ends, to which said sealing skirt and said lower profiled sealing member are secured and by which said lower profiled sealing member is forced into sealing engagement with said tank wall along a peripheral line thereof.

2. An assembly as set forth in claim 1, in which each of said leaf springs has a web which connects said two legs and bears on a surface portion of said floating top, said web has a web portion spaced from said surface portion, and an adjustable fixing screw extends through said spaced web portion and is adjustably fixed to said surface portion.

3. An assembly as set forth in claim 1, in which each of said profiled sealing members is strip-shaped and has jawlike portions, said jawlike portions of said upper profiled sealing member embrace said free ends of said upper resilient legs and the outer edge of said cover, said jawlike portions of said lower profiled sealing mEmber embrace said free ends of said lower resilient legs and the outer edge of said sealing skirt, and said profiled sealing members are provided on their outside with protruding longitudinal ribs.

4. An assembly as set forth in claim 1, in which said resilient legs are pivotally movable up to a predetermined angle, and at least part of said resilient legs carry slidable fingers, which are disposed on that side of the associated profiled sealing member which faces the tank wall and have a portion which is angled from said tank wall at an angle which is at least as large as said predetermined angle and extends around and tightly contacts the associated profiled sealing member where it is nearest to the tank wall.

5. An assembly as set forth in claim 4, in which said portion of each of said slidable fingers has a straight sub-portion extending from the profiled sealing member and an end portion which is angled from said sub-portion toward said profiled sealing member.