CA2090622C - Insertable pressure tube - Google Patents

Abstract

A flexible collapsible tube is arranged in such a way that the inherent strengths of its fibreglass and polymer composites can be used for the transmission of gas and fluid at extreme pressures.
This invention is most commercially appropriate when used to transport massive gas and fluid volumes over long distances and includes a mechanical connection for joining together tube sections or tube and steel fittings.

Description

DISCLOSURES
The inventive tube comprises an interior elastic inner sleeve of polyvinylidene fluoride or other similarly functional polymer substantially impermeable to a gas or liquid which is re-inforced against internal pressure by a protective fabric in two or more double layers which are each in an opposing direction as helical wrappings.
This arrangement provides each fabric layer with insurance against lateral movement as the over-lapping and under-lapping fabric is composed of opposite directioned parallel cords which while working against the internal forces of compression within the tube, give each single fabric layer prevention of lateral movement, being bonded together both internally and to its opposing member layer in the manner as follows:
The protective fabric is a composition of twisted fibreglass cords of variable diameter bonded together by neoprene or by another suitable polymer in the form of separated stretchable particles into a mono-directional cord configuration or single layer, which in turn is .eimil~rly bonded to comprise a minimum of two sheets to ensure integrity and strength. The number of sheets in combination governs the resistance to internal tube pressure. The inner sleeve serves primarily as a membrane substantially fluid and gas proof while also providing a low friction surface and minimi7ing degradation due to hydrocarbon contact.
While no way limiting the use of the inventive m~teri~l, the tubeline is intended for the tr:~nsmission of major volumes of hydrocarbon gases and liquids. Owing to its inherent flexibility and collapsibility, the tubeline may be utilized both as a stand-alone pipeline and as a "liner" for steel pipelines that are either abandoned, downrated or simply too expensive to m~int~in otherwise.
For pressure in excess of (15 bar) 250 psi, current industry practice is to transport major volumes of hydrocarbon fluids via carbon steel pipelines. Such pipelines and pipeline systems tla~ve.
provinces, states, countries and even entire continents. While recognizable advances have been made in the manufacture of high strength steels, these have generally been associated with increased metallurgical problems and a greater requirement for technical sophistication during pipeline construction. Even high grade steels have severe strength limitations when compared to the inventive composite material, and to provide large diameter steel pipe for extreme pressure application is not practical either from a manufacturing, cost or safety perspective.
The related use of composite materials to-date has been in the manufacture of rigid tubes of limited strength which are in no way suitable for the formation of vast pipeline net~o.Ls as required for the transportation of hydrocarbon fluids. While the components of the pertinent composite materials are well known and their physical and chemical characteristics adequately documented, the method of arrangement of the composite components and subsequentmanufacture of tube to satisfy the requirements of great strength, low cost, handlebility and ease of installation has not previously been invented.

,~q The two typical impregnated strand glass fibres to be used in flextube manufacture are "E" glass fiber and S2 glass fiber whose tensile strengths under ASTM 2343 in pounds per square inch are 270,000 to 620,000 for E glass and 530,000 to 620,000 for S2 glass. Until now these characteristics have been only minimally exploited in pipeline construction.
The inventive tube, can be manufactured in a number of sizes such as to provide operating tubes with diameters ranging from 6" to 52", and capable of cont~ining intern~l pressures of at least up to 5000 psig (340 bar g). The lengths in which the Flextube is manufacture is limited primarily by weight and ability to handle and transport the product, but will generally be in the 200-1000 meter range according to diameter and wall thickness.
In a pipeline system it will be necessary to provide methods of jointing for the inventive Flextube, both tube-to-tube and tube to steel pipeline fitting. For the former, a nipple of the same materials as the outer casing, but in rigid form, and with an outside diameter equal to the inside diameter of the Flextube will be used together with contact cement to bond the matching surfaces.
For illustrations of jointing by steel for tube to steel and tube to tube, please refer to Figure 3 to 8.

-IN THE DRAWINGS WHICH ILLUSTRATE EMBODIMENTS OF THE INVENTION
Wl'llllN THE DISCLOSURES

Fig. 1 shows a cross section of the inventive tube showing as by designation No. lt the position of the interior polymer tube in its position under compression against the walls of the first interior fabric layer as No.2 which is under the next fabric layer as No. 3. This forms a minimum arrangement of layers to make up the protective fabric sheath, but can be made up of any practical number of these double layers.
Fig. 2 shows a side view illustration of the inventive tube. Design~tinn No. 1 shows again the position of the interior polymer tube under compression against the helical wrap of the first fabric layer as No. 2, it being under the next helical wrap of fabric layers as No. 3.
Here by the large numbers 1 adjacent to the arrows is the position taken for the cross section of Fig. 1.
Fig. 3. A l/2 section of the steel pipe Section X shown in Fig. 6 in a similar bird's eye view.
This illustrates how a covering circular steel plate V is welded as W onto the open end of X to form a sealed cap to end a tube line. To join to a valve, X is similarly welded onto a valve fitting.
Fig. 4. Flared flextube passes under and over machined ring Y, which is then drawn in tension against fixed machined ring Z.
Fig. 5. Formation of a pressure seal onto pipe section X which tightens with increasing pressure.
Fig. 6. A bird's eye view of a steel pipe section of diameter equal to the inside of the flextubes which it will join, showing the position prior to joining of the flextube fabric by machined steel.
Pipe section X joins 2 lengths of flextube with or without the tributary addition shown.
Fig.7. shows how the flextube fabric passes first under and then over the compression rings Y, to be then joined by stapling or other means back on to the fabric to form a loop enclosing ring Fig. 8. shows how the expansion of the flextube under internal pressure pulls the fabric enclosed ring Y back against the fixed machined steel flair ring Z, which is welded to pipe section X.
Thus sealing the fabric by pressure from Y against Z. It is thus illustrated how the greater the pressure induced pull of the fabric against Y, the tighter and more effective is the seal.

--rhe following illustrates the method used in this Invention to assemble the adhesive sheets of the outer fabric material so that the flexibility of the fabric can be widely varied without loss of tensile strength.
Fibreglass cords coated with neoprene or other suitable polymer and o.04 inch diameter, are produced and stored on hollow cylinders 10 inches diameter and 11 inches long.
These reels are then fixed upright on the shelves of mobile creels each containing a large number of reels and a slotted brake drum around which each outgoing cord passes in restraint when pulled from the creel. This action applies an equal tension to each cord, and hence a unified tensile strength in the lengthwise direction of the fabric sheets.
The cords are taken from the creels in sequence and automatically threaded through individually identified guide holes. They are then brought onto the braking drum and then secured in sequentially identified "combs" made of precision V-slots which bind the cords on a downward pull into firmly held positions.
Combs are arranged in 4 levels, with each level holding the exact number of cords required to make up the prerequisite sheet width (i.e. sheet width in inches divided by 0.04") subdivided into 2 sections, the first division taking even numbered cords and the second odd numbered cords. Thus, when complete in a taut position a full set of cords are closely arranged, side by side. When all 4 levels are similarly complete, a mechanical action brings the combs into a flat position with open ends facing forward and the 4 levels are brought into position, within close proximity above each other, and an overall depth not greater than 0.16".
The initial 4 inches is then sprayed with fast setting adhesives and the four levels pressed firmly together while maintaining the preset width. This combined portion is then seized by a gripperjack which moves forward through open die rollers where it is attached to winch operated hauling line. The gripperjack pulls the cords through the rolling die, where the sheet is formed, on through the drying/vulcanizing corridor, and finally onto a powered storage reel. On activation of this reel the tape assembly formation begins.
In passage to the die, the cords emerging from the braking drum are peppeled with a course spray of a water-based pressure sensitive adhesive. This does not coat the cords but applies a regulated system of single adhesive points to the cord surfaces so that the binding between the cords serves to hold them together but only partially inhibits the individual cord flexibility, thus providing the supple tube wall bending propel~ies as required during tube storage and field installation. These adhesive points form, under stress conditions, minute cords of stretchable synthetic rubber, the degree of flexibility varying with the density of controlled application.
For illustrations of this project, please refer to Figures 7 to 12.
Relating to Fig. 9, the "Sprayed on" liquid rubber droplets on the tape cords "TC" are vulcanized after bonding cords together to form tape "T" in the rolling dye. Thereafter tape deformation and re-formation can occur through the elasticity of the rubber droplets stretching to form bonding rubber threads tying together the tape cords. These threads replace the interwoven across fabric cords common to all woven cloth and permit the formation of the extreme lengthwise cord density of FBG tube.

On entering the "mouth of the die, the upper die roller is swung into position over the sprayed tape cords and clamped down by 1/2 bearings on its shaft so that the cords are compressed into a sheet with a thickness of 0.16". The roller die fulfills the functions of the compressive rectangular opening of a rigid die while elimin~ting the problems of adhesive build-up at the die entry. Since the adhesive, prior to vulcani7ing by drying, is water soluble, the adhesive is removed by water cleaning from the die rollers as they move out of contact with the sheet under manufacture.
As the sheet exits the roller die machinery it is pulled into and through a large drying unit which drives off the water and vulcanizes the rubber adhesive. The finished sheet is then wound onto the powered sheet-storage reel, which is then stored in preparation for the manufacture of the tube proper.
In order to produce the inventive tube the outer fabric material must comprise a minimum of two of the manufactured sheets in thickness.
The reinforced inner sleeve of high tensile strength poly-vinylidene-fluoride can be manufactured in a separate plant remote from the Flextube facilities. Its manufacture is by conventional, even if hitherto unexploited, processes and the finished sleeve in elastic, tubular form can be shipped to the Flextube facility on reels and in lengths corresponding to those of the finished Flextube, for insertion into the tube in a manner similar to an inner tube in an inflatable tire. Likewise, the matelial to be used as an outer environmental-protection layer for the tube (specifically chosen and differing for individual environmental scenarios) will be made available at the Flextube manufacturing plant.
Thus, with each of the required components on-hand, fabrication of the finished Flextube product can proceed in the following manner.
The main components of the assembly line are a large mandrel, precisely sized for the finished product internal diameter and around which the Flextube is formed, and the mechanism holding the sheet-storage reels (the number of which is dependant on the number of layers required to form the finished tube).
The mandrel itself is made up as any releasing cylinder, an example being one whose surface comprises forward moving belts the forward speed of which are synchronized with the rotating speed of the tape-storage reels. The reel holding mechanism is arranged such that the sheet-storage reels (a minimum of two in accordance with the specific diarneter and design pressure of the tube to be manufactured) rotate around the mandrel and sequentially deposit the preformed sheets onto it, each sheet making up a layer of the finished tube. The initial sheet layer is wound onto the mandrel at an angle of 45 degrees to its axis, and each subsequent sheet is applied perpendicular to the last.

~09~6~
- On commencing the manufacturing process, with the belt speed of the mandrel exactly synchronized to the feed speed of the sheets, the first sheet unwinds onto the mandrel in an helix formation in which the wrap edges match perfectly with neither separation nor overlap, and the upper surface of the sheet is sprinkled with adhesive. Concurrently, as the first sheet is being rotationally applied in a clockwise motion with its adhesive surface facing outward, the second sheet is being applied to cover the first but in an anticlockwise motion and with its helical seams perpendicular to the previous sheet. Further layers, or sheets, as necessary are added concurrently in an identical manner with adhesive always applied to matching surfaces. The finished tube is fed off the end of the mandrel by the moving belts and either folded onto transportable pallets or wound onto huge storage reels.
As this tube outer casing is being produced, the pre-manufactured poly-vinylidene-fluoride inner sleeve is fed through the hollow centre of the mandrel at the speed of outer casing production, thus providing a complete Flextube product as it exits the manufacturing line.
The outer coating or covering, when required to protect the tube from its surrounding environment, can be applied either during the final stages of manufacture or during installation.
The inventive tube, as described above, can be manufactured in a number of sizes such as to provide operating tubes with diameters ranging from 6" to 52", and capable of containing internal pressures of at least up to 5000 psig (340 bar g). The lengths in which the Flextube is manufactured is limited primarily by weight and ability to handle and transport the product, but will generally be in the 200-1000 meter range according to diameter and wall thickness.
It should be noted that, because of the complexity and high cost of production line plant and machinery, it is intended to fabricate the prototype tubes from sheets made up of the pre-requisite number of 2" wide tapes. These tapes will be made in an identical, but less automated, manner as the previously described sheets, requiring the handling of only 200 coated fibreglass cords simultaneously rather than the many thousands necessary to produce a wide sheet in a single process. To form the sheets required for the prototype, the 2" wide tapes will be layed side-by-side on a long flat surface and a fabric scrim applied under pressure over the entire area of the tapes. The scrim material is up to 12% flexible across the width and length of the sheets and, when combined with contact cement, acts as a cohesive bridge across the tapes. Prototype tubes for testing purposes will have a maximum length of 12 meters (40 ft.).
In a pipeline system it will be necessary to provide methods of jointing for the inventive Flextube, both tube-to-tube and tube to steel pipeline fitting. For the former, a nipple of the same materials as the outer casing, but in rigid form, and with an outside diameter equal to the inside diameter of the Flextube will be used together with contact cement to bond the matching surfaces.
For illustrations of jointing by steel for tube to steel and tube to tube, please refer to Figures 1 to 6.

Claims (5)

1. A flexible liner for a pipe comprising; a flexible tube of materials selected from the class including polyvinylidene fluoride, the material being impermeable to gas or liquid and surrounded by a fabric sheath wherein the sheath is constituted bytwisted fibreglass filaments in polymer coated parallel cords within sheets wound spirally around the interior tube in two or more layers, each succeeding layer wound in a direction opposing the direction of windings of the preceding layer with elastic adhesive rubber in solid separate droplets forming stretchable reciprocal links bonding together all contiguous surfaces of both cords and sheets thus forming the flexible fabric sheath.

2. The liner as defined on Claim 1 where an outer surface of the liner is covered by materials selected from the class including polyvinylidene fluoride, the material being flexible and impermeable to gas and liquid.

3. The liner as defined in Claim 1 or 2 wherein the liner is used as a free gas or liquid carrying tube, independent of the pipe.

4. A process for forming a flexible liner for a pipe comprising the steps of:
Providing a flexible tube of materials selected from the class including poly-vinylidene fluoride, the material being impermeable to gas or liquid; surrounding the flexible tube with a fabric sheath wherein the sheath is made by a process comprising the following steps:
a) providing twisted fibreglass filaments in polymer coated parallel cords to form a section, where a number of cords in a section is defined by a required preset thickness and width of a sheet;
b) spraying the cords with elastic adhesive rubber droplets;
c) bringing mechanically four sections of cords into close proximity, one above another into a flat position;
d) pressing the four sections firmly together to form a combined portion while maintaining the preset width;
e) pulling the portion through a rolling die where the sheet is formed;
and f) pulling the sheet through a drying and vulcanizing corridor and onto a storage reel;

winding helically the sheet on a round mandrel at an angle of 45° to the axis of the mandrel, forming a first layer; sprinkling an upper surface of the first layer with elastic adhesive rubber droplets;
winding helically second sheet to form next layer; where the next layer is beingwound in opposite direction, at right angles to the latter sheet;
applying the elastic adhesive rubber droplets to the upper surface of the next and each subsequent layer where the adhesive elastic rubber droplets are always applied to the upper surface of each sheet layer that is subsequently followed by next sheet layer, the number of layers being defined by required conditions;
vulcanizing the sheath thus formed, within a drying corridor with a radiation heat.

5. The process of claim 4 wherein the flexible liner is covered by a material selected from the class including poly-vinylidene fluoride, the material being flexible and impermeable to gas and liquid.