GB2054020A

GB2054020A - Flexible structure for the separation of phases inside containers for storing fluids and process for obtaining that structure

Info

Publication number: GB2054020A
Application number: GB8013370A
Authority: GB
Original assignee: Industrie Pirelli SpA; Pirelli SpA
Current assignee: Industrie Pirelli SpA; Pirelli and C SpA
Priority date: 1979-05-30
Filing date: 1980-04-23
Publication date: 1981-02-11
Also published as: NL8002864A; JPS55163169A; FR2458010A1; IT1121069B; DE3020299A1; IT7923115A0; LU82490A1; BE883513A

Abstract

The invention provides a separator membrane (2) of cylindrical form. This can be of size not smaller than the internal container dimension, closed at one end (8) and sealed at its other end (7) around the circumference of the container. The membrane is made by winding flexible vulcanizable material around a mandrel to form a tube (9), applying external pressure to the windings (10) and vulcanizing under pressure. The membrane may be used to provide storage in the legs of offshore platforms. <IMAGE>

Description

SPECIFICATION Flexible structure for the separation of phases inside containers for storing fluids and process for obtaining that structure This invention relates to a flexible structure for the separation of phases inside containers for the storage of fluids and to a process for obtaining the said structure, and in particular the present invention relates to a separator membrane for containers, preferably cylindrically shaped, flexible or rigid, suitable for storing fluids.

Flexible separator membranes for containers for storing fluids are known.

The said known flexible separator membranes consist of a membrane of flexible material, the edge of which is secured between the two halves of the container. The two halves of the container are interconnected along a continuous line lying on a plane of symmetry of the container, the said plane being parallel to the larger dimension of the container itself. In this way, the membrane divides the internal volume of the container into two separate portions. Therefore, a different fluid can be introduced into each section without risk of the two fluids becoming contaminated.

The flexible separator membranes described above have numerous disadvantages.

One of these, valid in the case of large containers, is a consequence of the said large dimensions which the corresponding membranes must also assume. This creates considerable problems regarding the manufacture of the said separator membrane. In fact, the said membranes being normally of rubberized fabric, create vulcanizing problems in that presses of sufficient size to vulcanize the entire membrane in a single operation do not exist, as a result of which it is necessary to vulcanize the membrane, already produced, section by section, with all the ensuant problems.

If, however, the smaller strips are vulcanized, the vulcanizing operation can be carried out simply, but then there is the problem of joining the said strips so that they are leak-tight, in order to produce the membrane. These joins are very important because the said membrane is subjected to flexion and if the joins are not perfectly made, the life of these is very limited in the course of time.

The aim of this invention is to obviate or ameliorate the problems of the said known membranes and in particular to provide a separator membrane which is easy to produce, which is reliable and durable and which, finally, reduces the possibility of pollution of the outside atmosphere, even of the case of breaks in the walls of the container.

A further aim of the present invention is to provide a process for manufacturing a separator membrane of the desired size which does not create vulcanizing problems.

The subject of the present invention is a flexible separator membrane for a container for storing fluids, characterized by the fact that the said separator membrane is in the form of a cylindrical membrane.

A further subject of the present invention is a process for manufacturing a flexible separator membrane, consisting of a cylindrical membrane, which includes the following steps: (a) forming a tube by winding a strip of flexible, unvulcanized material onto a mandrel; (b) applying pressure to the external surface of the tube obtained in step (a); (c) vulcanizing the tube while still applying pressure to the external surface.

The present invention will be more clearly understood from the following detailed description which is given as an example and is therefore not limitative, with reference to the accompanying drawings in which: Figure 1 shows a section of a container for storing fluid provided with a separator membrane in accordance with the present invention; Figure 2 shows a perspective view of a section of a separator membrane in accordance with the present invention; Figure 3 shows an enlarged view of a detail of an embodiment in accordance with the present invention.

In one broad aspect, the flexible separator membrane to be inserted in a container, preferably cylindrical in shape, for storing fluids, consists of a cylindrical membrane designed to contact the internal walls of the container, without being placed under tension.

Figure 1 illustrates the section of a container 1 provided with flexible separator membrane 2 in accordance with the present invention.

Container 1 illustrated in Figure 1 is a rigid container, which can be used as a tank for motor vehicles or as a fixed container, to be placed on the sea bed for example.

(The separator membrane in accordance with the present invention can also be used for nonrigid containers.) The said container 1 consists of a metal case having a cylindrical shape.

The end 3 of the said container is hemispherical, whereas the opposite end 4 is provided with a circular flange 5 to which a cover 6 is connected in a known manner, e.g. by means of nuts and bolts (of which only the axis is illustrated in the said figure by means of a chain line).

Separator membrane 2 consists of a cylindrical membrane of flexible material, one end of which (indicated by reference number 7) is attached to container 1 itself by insertion of the said end 7 between the said cover 6 and said flange 5, with or without the interposition of suitable seals (not illustrated in the drawing) in accordance with methods well known in the field.

In accordance with an embodiment illustrated in Figure 3, separator membrane 2 is connected to container 1 by placing a rigid ring 2' (consisting of a single piece or of several independent segments) against the internal surface of container 1, by placing end 7 of membrane 2 between the said rigid ring 2' and the said internal surface of container 1, and by connecting the said rigid ring to the container by means of bolts 2".

Obviously, seals may also be placed between rigid ring 2' and container 1, in order to improve or guarantee the seal.

The opposite end 8 of the said cylindrical membrane is sealed with known means, preferably mechanical, or by means of adhesive, stitching and/or clinching or vulcanization.

The dimensions of the said cylindrical membrane are in the same order of size and preferably not less than the internal dimensions of container 1.

In addition, the cylindrical membrane, obviously when it is not collapsed, is installed in container 1 so that it is co-axial with the container itself.

The said cylindrical membrane consists of a tube of flexible material, such as, for example, rubberized fabric.

The structure of the said tube is illustrated in Figure 2.

Figure 2 illustrates a perspective view of portion 9 of the tube.

The said tube is obtained by helicoidally winding at least one strip 10 of rubberized fabric, with the edges 11 of each coil superimposed on the edges of the adjacent coil (shown in dotted line).

The particular elastomeric mixture used for separator membrane 2 can be any known suitable mixture of elastomeric material, but able to withstand the fluids for which container 1 is to be used.

Container 1 is also provided with at least one aperture 1 2 (see Figure 1) connected to the inside of separator membrane 2, where the particular fluid to be stored in the container is introduced.

In order to facilitate the removal of the fluid contained in the separator membrane 2, at least one further aperture 13 is provided in order to allow any fluid present in the atmosphere outside the container to enter when it is desired to empty the container.

In the case of a submerged tank, the fluid is the water which surrounds the container.

The present invention also relates to a process for manufacturing a separator membrane in accordance with the present invention.

Thus in a further broad aspect in accordance with the present invention for manufacturing a separator membrane consisting of a cylindrical membrane as described above, the process comprises a first step in which a tube is formed by winding a strip of flexible material around a mandrel, a second step during which pressure is applied to the external surface of the tube formed during the previous step and a third step during which the tube is vulcanized whilst pressure is still applied to the external surface.

In view of the considerable dimensions which the separator membrane may have in accordance with the present invention, it is preferable to use mandrels provided with means designed to supply heat from the inside in order to avoid the use of autoclaves.

A particular process for manufacturing a separator membrane in accordance with the present invention is as follows.

At least one strip of rubberized fabric, not yet vulcanized, is wound helicoidally on to one of these mandrels, in order to obtain a tube.

The edges of each coil of the said strip wound helicoidally on the mandrel are superimposed on the edges of the adjacent coil in order to make the wall of the tube continuous.

Also, in some cases, it will be possible to wind at least two strips, superimposing one on top of the other, also with the weft and the warp of the fabric incorporated in each strip inclined in a known manner in relation to the weft and the warp of the other strip in order to obtain a stronger tube.

The elastomeric material of the strip or various strips is still in a crude state at this point and before proceeding to vulcanize it, it is necessary to appiy to the outside a binding of a suitable material (e.g. a fabric) treated in a known manner so that it will not adhere to the elastomeric material constituting the tube itself.

This binding is carried out in order to apply an adequate pressure to the tube, particularly during the subsequent vulcanization stage.

Preferably, the binding also fulfills the task of thermally insulating the tube during the subsequent vulcanization stage, when the heat will be supplied from the inside to vulcanize the said tube.

It is only advantageous in the case of small tubes to vulcanize in autoclaves, in which case the bonding no longer has the further function of thermally insulating the tube.

In particular, in the case of tubes having large diameters, for which it is not possible to use an autoclave, it is particularly advantageous to use strips consisting of a textile material having heat shrinkage characteristics, to make the binding.

In fact, with the action of the heat supplied from inside the mandrel, at the same time the elastomeric material of the tube expands and the binding formed from the strip of material which shrinks in heat, contracts.

In this way, a pressure is applied to the zone between the mandrel and the binding which guarantees a perfect weld between the coils of rubberized fabric in the zones where they overlap and vulcanization of the elastomeric material, avoiding the formation of bubbles and/or porosity.

Once the tube has been vulcanized, the binding is removed and the tube removed from the mandrel by jets of compressed air supplied in the zone separating the mandrel and the tube.

One end of the tube is squeezed to bring the internal surface of the tube in contact along a line.

The said end of the tube is sealed along the said line and made leak-tight by the use of preferably mechanical means or by means of adhesives and/or metal clips or stitching.

At this point, by inserting the tube in a container and attaching the open end, opposite to the closed end, in one of the ways previously described, inside the said container, a flexible separator membrane is obtained consisting of a cylindrical membrane which divides the internal volume of the container into two perfectly sealed parts.

With the process, described above, for producing a flexible separator membrane consisting of a cylindrical membrane in accordance with the present invention, it is easy to see how separator membranes having large dimensions, both of diameter and of length, can be obtained and vulcanized in a single operation.

Therefore, it is possible to eliminate the danger arising from cracks found in the known separator membranes where the joins are made between the various pieces forming the membrane of the separator membrane itself.

It is easy to see how the predetermined aims are achieved with a separator membrane in accordance with the present invention.

In fact, the flexible separator membranes consisting of a cylindrical membrane in accordance with the present invention create a further barrier in addition to the one formed by the case of the container itself between the liquid stored and the outside atmosphere.

Consequently, even if the case for the container is accidentally perforated, the stored fluid will not escape and there will be no subsequent contamination of the external atmosphere.

In addition, as it is possible to construct cylindrical containers in which the connection between the separator membrane and the container itself is made at one end of the cylinder instead of along a perimeter lying in a plane of symmetry, as in the state of the art, the possibilities of leaks in the area where the separator membrane joins the container are considerably reduced, in relation to the dimensions of the container.

In fact, the area of the join of the two halves of the known containers extends along a perimeter lying in a plane of symmetry of the container itself over a length equal to twice the length and twice the diameter or width of the container, whereas when using a separator membrane in accordance with the present invention, the length of the connecting area of the separator membrane is only equal to the circumference of the cylinder.

Finally, the particular cylindrical form of the separator membranes in accordance with the present invention could make it possible also to use the volumes inside the support columns of oil rigs in order to be able to store in these columns considerable quantities of fluid without having to construct suitable containers.

Although particular embodiments of a flexible structure for the separation of phases inside containers for storing fluids and of a process for obtaining the said structures have been described and illustrated, it is understood that all the possible variations accessible to an engineer in this field are included within their scope.

Claims

1. A flexible separator membrane for a container for storing fluids, in which the said separator membrane is in the form of a cylindrical membrane.

2. A flexible separator membrane according to claim 1, in which the cylindrical membrane has a sealed end along a line, whereas the opposite end is attached, so that it is leak-tight, to the container around its circumference.

3. A flexible separator membrane according to claim 1 or 2, in which the said cylindrical membrane comprises at least one strip of flexible material which is wound round with the edges of each coil overlapping the edges of the adjacent coil.

4. A flexible separator membrane according to claim 1, 2 or 3, in which the said cylindrical membrane is co-axial with the container.

5. A flexible separator membrane according to any one of the preceding claims, in which the dimensions of the said cylindrical membrane are not smaller than the internal dimensions of the container.

6. A process for manufacturing a flexible separator membrane in the form of a cylindrical membrane, which includes the following steps: (a) forming a tube by winding a strip of flexible non-vulcanized material round a mandrel; (b) applying pressure to the external surface of the tube obtained in step (a); (c) vulcanizing the tube while still applying pressure to the external surface.

7. A process according to claim 6, in which the pressure on the external surface of the tube to be vulcanized is applied by means of a binding.

8. A process according to claim 6, in which the pressure applied to the tube during vulcanization is that resulting from the action of thermal expansion of the elastomeric material of the tube and of the thermal contraction of the strip forming the binding.

9. A cylindrical flexible separator membrane substantially as hereinbefore described with reference to and as shown in the accompanying drawings.