EP0080130B1 - Sealing means for the annular space between a container wall and the floating roof of a large storage container - Google Patents

Description

The invention relates to a device for sealing the annular gap between the vertical container wall and the floating cover of a large-capacity container, in particular a floating roof tank or a fixed roof tank with an internal floating cover, consisting of a large number of narrow spring bands attached to one another at uniform intervals next to one another on the circumference of the floating cover and having their free ends resilient are directed against the tank wall, span the ring gap with elastic deflection and press an elastic sealing profile attached to their free ends along a circumferential line against the tank wall, the ring gap being closed by a sealing apron that runs around the entire ring gap between the sealing profile and the floating cover.

Such annular gap seals are mainly used for the storage of volatile, liquid refinery products and chemicals to avoid evaporation losses and the accumulation of dangerous vapors. The annular gap between the vertical tank wall and floating ceiling required for the vertical movement of the floating cover must be closed by an elastic sealing element, which is able to compensate for operational changes in the annular gap width as well as severe out-of-roundness and bulges in the tank wall and thereby the escape of product vapors or the Prevent rainwater from entering as far as possible.

Another important task of the annular gap seal is to ensure that the free-floating cover is adequately centered, which is to ensure trouble-free vertical movement without local overloading or tilting. However, especially for use on lightweight floating ceilings with less buoyancy, the frictional forces emanating from the annular gap seal must not become so great that there is a risk of the floating cover getting caught or being flooded by stored product.

Ideally, the annular gap seal should be able to exert a uniformly strong centering effect over the entire circumference of the tank, be able to easily compensate for deviations in the annular gap width by means of eccentricity, out-of-roundness and bumps with the help of sufficient spring travel, cover even smaller imperfections and unevenness of the tank wall by means of wide-area and elastic adjustment and as wear-resistant as possible have an outer shell. In addition, the materials used should be extremely resistant, both to the storage media and to weather conditions.

In practice, one tries to meet these complex requirements by attaching an elastic sealing element to the outer edge of the floating cover, which is adapted to the respective annular gap width by spring forces (DE-OS 2730546), by gravity (Bulletin No. 3200 from 1976 the company Chicago Bridge & Iron Company), by internal tension (US Pat. No. 3,795,359) or by hydraulic forces (US Pat. No. 4,773,291) and the gap by a circumferential, flexible sealing apron or an elastic hose filled with liquid or plastic foam closes.

Annular gap seals for floating roof tanks are usually subdivided into a primary seal and a secondary seal today, whereby the primary seal facing the stock product is intended to retain the majority of the product vapors and the secondary seal directed against the atmosphere, in addition to improving the overall sealing effect, is intended in particular to prevent the ingress of rainwater. In contrast, annular gap seals for indoor floating ceilings in fixed roof tanks only have the task of limiting product emissions.

The following basic designs are known among the newer secondary seals for floating roof tanks: spring-loaded lip seals (US Pat. No. 4116358), spring-reinforced rubber aprons (DE-OS 2 832 978), lip seals made of polyurethane elastomer (publication EKT 0028-3-79 from Elastogran) and spring-loaded foam pads with abrasion-resistant covering.

Lip seals have the disadvantage that they only seal along a narrow and relatively stiff lip, with sharp bumps, e.g. B. vertical welds, can not be sealed and often the danger of everting, z. B. on horizontal welds. Spring-reinforced rubber aprons are also relatively stiff, so they cannot adequately seal vertical weld seams and are also at risk of being turned inside out. Resiliently pressed foam pads with an abrasion-resistant covering have the best chance of guaranteeing a seal with particular effectiveness and operational safety thanks to their high deformability, wide sealing surface and well-rounded outer shapes. Unsatisfactory in known designs of this type is the often insufficient corrosion resistance and long-term durability of the spring elements used and the resulting limitation of the possible spring travel.

So far, no optimal solutions have been known for sealing light indoor floating ceilings in fixed roof tanks. The known primary seals for floating roof tanks are too heavy for this application and result in excessive frictional forces. The frequently used lip seals made of polyurethane elastomer do not offer a sufficient sealing surface and cannot guarantee complete sealing and even centering of the floating cover due to the risk of being turned inside out give, especially since the seal is usually not turned over the entire circumference of the tank.

In a known annular gap seal of the type mentioned at the beginning (DE-AS 2 358 636), leaf springs are provided as spring bands, which are arranged at large mutual distances, which necessitates the use of thick spring bands. These thick spring bands are relatively stiff, offer considerable resistance to the elastic deformation and press the sealing profile at points onto the container wall. The rigidity of the spring bands makes the assembly of this known annular gap seal very difficult. The outer ends of the spring bands are pointed at an acute angle to the tank wall, which means that the hard sealing profile, which is only of relatively small cross-sectional dimensions, can get caught more easily when the floating cover moves vertically. In addition, the known annular gap seal is designed only for the simultaneous primary and secondary sealing of a floating roof tank, the prestressing of the leaf spring legs lying up and down should be adjustable by a central fastening screw engaging in a vertical wall of the floating cover. The attachment of the mounting holes required for this in the vertical wall of the floating cover is undesirable because such holes can cause leaks in the floating body. In addition, the attachment points are no longer accessible after the sealing apron has been attached, so that later spring adjustments only appear possible after the apron has been removed.

In another known annular gap seal (DE-A 3 007 389), the annular gap between the tank wall and the floating roof is covered in the manner of conventional weather protection plates by rectangular spring plates with mutual lateral overlap and with elastic deflection. At the ends of the spring plates, curved sliding block strips made of hard plastics are provided as contact elements to the tank wall.

This type of annular gap cover does not meet today's requirements for improved sealing of the annular gap and is merely to be regarded as an improvement of the already known weather plates for deriving the precipitation falling into the annular gap. In order to achieve a higher sealing effect, the sealing apron that spans the entire annular gap is missing. The overlapping spring plates are neither steam-proof nor watertight at their floating roof connection. The sliding bodies made of solid plastics only form a narrow line of contact with the tank wall and cannot adapt to fine bumps (e.g. weld seams). The mutual overlap of the spring plates also results in mutual hindrance, which prevents optimal adaptation to the tank wall.

Stainless steel sheets with the required width and spring hardness are not available. Stainless steel sheets without spring hardness are unsuitable for this task. The spring plates shown are too short. In the case of the enlargement of the annular gap that occurs in practice due to the tank being out of roundness, the spring plates are pulled down and kinked when the floating roof moves upwards and strikes sliding obstacles.

In another known annular gap seal (GB-A 1 445 996), trapezoidal foam blocks made of semi-rigid polyurethane foam with a hard outer compression zone are arranged as the primary seal in the annular gap between the tank wall and the outer wall of the floating roof. The deformation forces of these foam blocks are so high that the free floating position of the floating roof is endangered. The elements for holding and supporting the foam blocks protrude far into the annular gap, allow only a slight deviation in the annular gap widths and place high demands on the roundness of the tanks. In order to achieve a good sealing effect, the lower part of the foam blocks is immersed in the storage medium, penetrates into the foam and has the effect that the tank cannot be made <gas-free> even after emptying, since the foam releases the absorbed storage liquid only slowly. The described primary seal cannot hold back the precipitation falling into the annular gap.

The invention has for its object to provide a preferably usable as a secondary seal for floating roof tanks and as an annular gap seal for indoor floating ceilings of fixed roof tanks, which avoids the disadvantages of the known designs, especially with relatively low frictional forces and uniform centering effect for the floating cover a maximum of flexibility, sealing effect and operational reliability with low corrosion sensitivity of the components used.

On the basis of the type described at the outset, this object is achieved by the present invention in that a plurality of adjacent spring bands are connected at their free ends to a receiving profile piece which is open toward the tank wall to form a spring unit, and that the sealing profile is formed from a plurality of soft foam elements which lie against one another, around which the sealing apron is knocked against the tank wall, and that each soft foam element is pressed against the tank wall by a plurality of receiving profile pieces sitting closely next to one another.

The annular gap seal according to the invention has a permanently high spring elasticity and extremely good shape adaptation, as well as a uniform centering effect for the floating cover. The extreme shape adaptation is thereby achieved that the spring bands and mounting profile pieces combined into separate spring units can adapt the soft-elastic outer sealing profile to the locally existing tank contour in a segment-independent manner, independently of the adjacent spring units, the soft-elastic outer sealing profile being able to bend in the spaces between the mounting profile pieces in every horizontal direction.

The wide and soft elastic pressure of the outer sealing body ensures a high sealing effect with low frictional forces. Due to the spring bands that run practically parallel to the tank wall due to their deflection and the voluminous, soft and rounded outer sealing body, the danger of everting is eliminated. The individual spring straps are easily accessible without dismantling the sealing apron.

Advantageous embodiments are characterized in claims 2-9.

The arrangement is advantageously such that the receiving profile pieces have a substantially C-shaped cross-section and a flange which is approximately perpendicular to the profile opening and to which the free ends of the spring strips are fastened, and that the receiving profile pieces have a profile bend opposite the flange for claw-like mounting of the soft foam elements. The cross-sectional design of the receiving profile pieces allows easy attachment of the individual soft foam elements to be joined into a ring, the flange which adjoins the profile opening approximately vertically allowing attachment to the free ends of the spring bands in such a way that the spring bands are aligned with these free ends practically parallel to the tank wall, whereby a considerable radially directed elasticity of the annular gap seal is achieved without the risk of being turned inside out or getting caught. The claw-like holder is advantageous for attaching the soft foam elements.

To achieve a defined abutment of the soft foam elements on the container wall, the soft foam elements for use on a secondary seal, viewed in cross section, are chamfered on their side facing the tank wall in such a way that they have the shape of an upward-looking blunt wedge when not pressed. The chamfer ensures that even when the gap narrows, the upper edge of the outer sealing body is always pressed firmly onto the tank wall and a sufficiently wide sealing surface is created.

The lateral spacing of the receiving profile pieces is to be dimensioned such that, on the one hand, the soft foam elements are pressed against the tank wall as seamlessly as possible and that, on the other hand, mutual interference between the receiving profile pieces is avoided and the soft-elastic outer sealing body can bend freely at the spaces between the receiving profile pieces.

The free ends of two to six adjacent spring bands are expediently fastened to a receiving profile piece. Here, two to six spring bands and a receiving profile piece form a spring unit.

In pursuit of the inventive concept, it is provided that the spring strips are made of stainless spring steel sheet and the receiving profile pieces are made of stainless steel sheet.

Further details are explained in more detail below with reference to the drawings illustrating the exemplary embodiments.

• Fig. 1 eine perspektivische Schnittansicht einer Ringspaltabdichtung als Sekundärdichtung eines Schwimmdachtanks.
• Fig. 2 einen Schnitt durch eine Ringspaltabdichtung an einer Innenschwimmdecke eines Festdachtanks und
• Fig. 3 einen Querschnitt durch das in Verbindung mit der Sekundärabdichtung gem. Fig. 1 verwendete Schaumstoffelement.

It shows:

• Fig. 1 is a perspective sectional view of an annular gap seal as a secondary seal of a floating roof tank.
• Fig. 2 shows a section through an annular gap seal on an inner floating ceiling of a fixed roof tank and
• Fig. 3 shows a cross section according to the in connection with the secondary seal. Fig. 1 used foam element.

1 shows the vertical container wall 1 of a floating roof tank, which bears the annular gap seal, generally designated by the reference number 2, which bridges the annular gap 3 between the container wall 1 and the floating roof 4. The annular gap seal 2 is used above a conventional primary seal, not shown. On the horizontally inward flange 5 of the floating roof 4, the thin and closely spaced spring straps 6 are fastened by means of screws 7 and with the interposition of a terminal block 8. The sealing apron 9, which runs endlessly around the entire annular gap, is fastened on the one hand to the receiving profile pieces 10, is knocked against the tank wall around the foam elements 14 and is fastened at the other end to the horizontal flange 5. The spring strips 6 consist of approximately 1 mm thick and approximately 100 to 200 mm wide sheet metal strips made of stainless spring steel.

In the example shown, three spring bands 6 are combined to form a spring element by a receiving profile piece 10 with a C-shaped cross section. The receiving profile pieces 10 have a flange 11 which is approximately perpendicular to the profile opening and to which the free ends of the spring strips 6 are fastened at 12 from the outside. The spring strips 6 are connected to the receiving profile pieces 10 in such a way that a short end piece 13 of the spring strips protrudes into the C-profile and holds the foam elements 14 in a claw-like manner in cooperation with an opposite profile fold 15.

The foam elements 14, each passing through a plurality of receiving profile pieces 10 and made of a flexible polyurethane foam, have an approximately square, rectangular or rhombic cross section, for example the cross section shown in FIG. 3. As can be seen from Fig. 3, the foam elements 14 are at their court against the tank wall tete side with a chamfer 16, so that the shape of an upward blunt wedge is formed. This ensures that the outer sealing body always lies with its upper edge against the tank wall 1 even when the gap has narrowed and that the water running down the tank wall when it is raining is pushed away from the tank wall without a larger storage space being able to form above the seal.

The sealing apron 9 consists of a fabric-reinforced rubber material or plastic with high flexibility and abrasion resistance. The sealing apron 9 is, in addition to the attachment to the floating roof 4 already described, attached to the rear of the receiving profile pieces 10 by means of terminal strips 17 at 18.

2 shows the annular gap seal 2 'between the vertical container wall 1' and the inner floating ceiling 4 'of a fixed roof tank, the fill level of which is indicated by the level line 19. Comparable components are designated by the reference numerals used for FIG. 1, which, however, are provided with an index line. The spring bands 6 'are bent downwards against the tank wall 1'. The foam elements 14 'have an approximately square cross section in the unpressed form. In this example, the sealing apron 9 'is clamped in at the connection point between the flange 11' and the spring strips 6 'by means of terminal strips 17', folded down around the foam elements 14 'and below the spring strips 6' on the outer edge flange 5 ' Inner floating ceiling 4 'fastened by screws 7' and terminal strips 8 '.

Claims (9)

1. Device for sealing the annular gap (3, 3') between a vertical container wall (1, 1') and a floating cover (4, 4') of a large storage container, especially of a floating roof tank or of a fixed roof tank with internal floating cover, consisting of a plurality of narrow spring strips (6, 6'), fixed at uniform intervals adjacent to one another to the periphery of the floating cover (4, 4'), which are orientated with their free ends resiliently against the tank wall (1, 1'), bridge across the annular gap (3, 3') while bending elastically and press an elastic sealing profile (14, 14') fixed to their free ends onto the container wall along a circumferential line, the annular gap being closed by a sealing apron (9, 9'), extending around the entire annular gap between the sealing profile (14, 14') and the floating cover (4, 4'), characterized in that,

a plurality of adjacent spring strips (6, 6') are connected at their free ends to a seating profile member (10, 10'), open towards the tank wall (1), to form each spring unit,

that the sealing profile is formed of a plurality of soft foam elements (14, 14') bearing against one another, around which the sealing apron (9, 9') is wrapped against the tank wall, and

that each soft foam element (14, 14') is pressed onto the tank wall by a plurality of seating profile members (10, 10') situated closely against one another.

2. Device according to Claim 1, characterized in that the seating profile members (10, 10') have a substantially C-shaped cross-section and a flange (11, 11') adjoining the profile opening approximately perpendicularly, to which flange the free ends of the spring strips (6, 6') are fixed, and that the seating profile members possess a turned- over edge (15, 15'), opposite to the flange, for holding in the manner of a claw the soft foam elements (14, 14').

3. Device according to Claims 1 and 2, characterized in that the soft foam elements (14), for use at a secondary seal, are chamfered (16) as viewed in cross-section at their side towards the tank wall (1) in such a manner that, in the uncompressed state, they have the form of an upwardly orientated truncated wedge.

4. Device according to one of Claims 1 to 3, characterized in that the free ends of from two to six adjacent spring strips (6, 6') are fixed to one seating profile member (10, 10').

5. Device according to one of Claims 1 to 4, characterized in that the spring strips (6, 6') are manufactured from stainless spring steel sheet and the seating profile members (10, 10') from stainless steel sheet.

6. Device according to one of Claims 1 to 5, characterized in that the sealing apron (9) wrapped around the soft foam elements (14) is fixed, at the rear side of the seating profile members (10), by means of clamping strips (17).

7. Device according to one of Claims 1 to 5, characterized in that the sealing apron (9'), wrapped around the soft foam elements (14'), is clamped, at the connection point between the spring strips (6') and the seating profile members (10'), by means of clamping strips (17').

8. Device according to one of Claims 1 to 7, characterized in that the soft foam elements (14, 14') are of polyurethane having a generally square, rectangular or rhombic cross-section.

9. Device according to one of Claims 1 to 4 and 8, characterized in that the soft foam elements are held force-transmittingly in the seating profile members by interference fit.

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