WO2009128818A1

WO2009128818A1 - High-pressure vessel fabrication method

Info

Publication number: WO2009128818A1
Application number: PCT/US2008/060297
Authority: WO
Inventors: Sergey V. Grigorovich; Sergey A. Koltsov; Ivan D. Chobit; Vladimir P. Shagurov
Original assignee: Midwest Research Institute
Priority date: 2008-04-15
Filing date: 2008-04-15
Publication date: 2009-10-22
Also published as: WO2009128818A9

Abstract

A high-pressure vessel fabrication and methods of fabrication are disclosed. An exemplary vessel includes a gas-tight inner liner fabrication, an outer structural overwrap fabricated by reinforcing a filament winding onto the gas-tight inner liner, and an overwrap polymerization. Prior to rotational molding of an inner seamless polymer liner, nozzles are manufactured for subsequent installation into a rotational mold that have grooves on both surfaces of embedded portions and a raised ring shoulder on the surface of a bore near an outlet of the nozzle.

Description

High-Pressure Vessel Fabrication Method

Contractual Origin The United States Government has rights in this invention under Contract No. DE-

AC36-99GO10337 between the United States Department of Energy and the National Renewable Energy Laboratory, a Division of the Midwest Research Institute.

Technical field The invention relates to equipment manufacturing, and in particular to a method for manufacturing high-capacity vessels to be operated under high pressures of 200 kgf/sq. cm and higher for use in all industrial applications, including gas-fueled (e.g., methane) vehicles.

Background A typical range without refueling for vehicles with high-pressure gas equipment usually does not exceed 30% to 50% of the range of conventional gasoline-fueled vehicles. This requires more frequent refueling, that is a greater number of high-pressure gas refueling terminals is needed, and imposes stringent requirements with regards to weight and dimensions of gas vessels for the vehicle to be refueled and for the refueling equipment. Universal availability of methane, its relatively low cost and environmentally safe combustion products makes it a very promising fuel for the near future, taking into account rapid depletion of global liquid hydrocarbon reserves and relatively compressible gaseous propane.

In spite of apparent simplicity and popularity of high-pressure vessels currently in use, abundance of designs, materials and fabrication technologies, and their widespread use in various industrial applications, the development of high-capacity (hundreds or thousands of cubic meters) high-pressure vessels with good performance combined with low cost that would be suitable for carrying methane remains a challenging task.

A method is known for fabricating a composite design cylinder for storing and supplying high-pressure liquids and gasses, wherein the cylinder is a shell consisting of an inner metal liner and outer composite overwrap. The shell design comprises an electrically welded thin- metal shell ring, boss and neck. The inner cavity of the metal liner is filled with granular material through the neck, and the filler is fully compacted (e.g., by vibration) to provide resistance to external pressure during subsequent composite overwrap winding. A plug is installed into the neck and is used as the backside support pin. The front-side support pin is installed into the boss. The metal shell with front and back support pins is installed on a winding machine, and composite material is applied to the outer surface by winding. The cylinder is placed into a heat-treatment chamber, where the composite material is polymerized. After polymerization, the cylinder is removed from the heat-treatment chamber. Additionally, to reduce cylinder weight, the ratio of metal liner thickness 8me_t to composite overwrap thickness δ _COm is set δ to 6_met.=(0.1 ÷ 0.2) δ_COm

The drawback of the above cylinder fabrication method is that, due to significant differences between elasticity modulus values of the metal liner and that of structural composite overwrap, it is not possible to optimize the cylinder design and fully use mechanical properties of both the liner and the overwrap. To achieve good vessel strength under pressure, the composite overwrap is pre-stressed. As a result, when pressure is released, the inner metal liner becomes overstressed, residual strains occur, and, therefore, the shell has low strength properties under cyclical loading conditions.

Another method is known for fabrication of high-pressure vessels from composite materials. Prior to winding of the structural overwrap onto the elastic gastight liner, an additional washer is placed over the nozzle. The washer's smooth surface is in contact with the liner, and flats in the bore of the washer are in contact with mating flats on the nozzle. Sharp pins are pressed into the washer with 1 to 2 mm pin projection above the surface of the washer in contact with the structural overwrap. During the winding process, high-strength filaments coated with polymer binder are placed layer-by-layer between the pins to achieve the design thickness, and since pins' height is less than the design thickness, they become fully covered and, after polymer hinder hardening, rigidly embedded into the structural composite overwrap. After structural overwrap winding is completed, and prior to polymerization in an electric oven, a spacer washer is placed over the nozzle, and a threaded nut is installed to force the gas-tight liner and the structural overwrap against the nozzle flange. Sharp pins rigidly embedded into the composite overwrap material prevent washer rotation under maximum torque conditions. Flats in the washer bore and mating flats on the nozzle prevents nozzle rotation under the same maximum torque applied to the nozzle.

The drawback of this method of large high-pressure vessel fabrication from composite materials is insufficient vessel strength for pressures of 200 kgf/sq.cm and above.

Another method of high-pressure vessel fabrication is known comprising prefabrication of a gas-tight liner with holes for nozzle installation, winding of the structural composite overwrap over the gas-tight liner, and polymerization. The gas-tight liner is made from two halves, each molded from a composite material using a negative and a positive die. Nozzles are glued in, halves are connected using locking glued joints, joints are reinforced by a composite material band, and the outer structural overwrap is formed by winding and additionally attached to the nozzle with a nut. The thickness of the gas-tight liner is selected so that it provides adequate rigidity and stability in the course of the structural composite overwrap filament winding.

The complexity of the technological process of high-pressure vessel fabrication, eventually results in its higher cost is a drawback. The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.

Summary The following embodiments and aspects thereof are described and illustrated in conjunction with systems, tools and methods that are meant to be exemplary and illustrative, not limiting in scope. In various embodiments, one or more of the above-described problems have been reduced or eliminated, while other embodiments are directed to other improvements. An exemplary high-pressure vessel fabrication and methods of fabrication of the inner gas-tight liner, fabrication of the outer structural overwrap by winding reinforcing filaments onto the inner liner, and polymerization of the shell are disclosed. Prior to rotational molding of the inner seamless polymer liner, nozzles are fabricated for subsequent installation into the rotational mold that have grooves on both surfaces of their embedded parts and an annular shoulder on the bore surface near the outlet of the nozzle. Then, the inner gas-tight liner is attached to one nozzle, so that it can be rotated, and dry reinforcing filaments winding begins at a point next to the nozzle by rotating the liner and using a filament applicator that goes around the free-end nozzle of the liner; after application of the first layer, the multi-layer overwrap winding is continued, and for each layer the liner rotation axis is shifted relative to the filament application axis of rotation by an angle 4) of no less than 2 degrees, and the number of coils in each layer and the thickness of each subsequent layer is decreased, the reinforcing filament impregnation by binder occurs in vacuum, and binder polymerization takes place at a temperature below that of softening of the inner liner material. The inner gas- tight liner is made of a polymer material, whose rigidity is sufficient to maintain the liner shape during reinforcing filament application and ensure gas-tightness when the vessel is filled and pressurized to its operating pressure.

In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the drawings and by study of the following descriptions.

Brief Description of the Drawings

Exemplary embodiments are illustrated in referenced figures of the drawings. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than limiting.

Figure 1 shows a cross-section of a high-pressure vessel fabricated using the disclosed method.

Detailed Description Exemplary embodiments described herein result in simplification of the procedure for fabrication of large high-pressure vessels that helps ensure maximum strength even under cyclical loading conditions.

Technically, the result in the method described herein is achieved by the novel characteristic in the process of high-pressure vessel fabrication involving fabrication of the inner gas-tight liner and outer structural overwrap by winding polymer filament over the inner liner, and polymerization. Prior to rotational molding of the inner seamless polymer liner, nozzles are manufactured for subsequent installation into the rotational mold that have grooves on both surfaces of their embedded parts and an raised ring shoulder on the surface of the bore near the outlet of the nozzle. Then, the inner gastight liner is attached to one nozzle, so that it can be rotated, and dry reinforcing filaments winding begins next to the nozzle by rotating the liner and using a filament applicator that goes around the free-end nozzle of the liner; after application of the first layer, the multi-layer overwrap winding is continued, and for each layer the overwrap rotation axis is shifted relative to the filament applicator axis of rotation by an angle ø of no less than 2 degrees, and the number of coils in each layer and the thickness of each subsequent layer is decreased, the reinforcing filament impregnation by binder occurs in vacuum, and binder polymerization takes place at a temperature below that of softening of the inner liner material.

The novel characteristic of the high-pressure vessel fabrication method according to claim 2 is that the inner gas-tight liner is made of a polymer material whose rigidity is sufficient to sustain the shape during reinforcing filament winding and ensure gas-tight seal when the vessel is filled and pressurized to its operating pressure.

Now consider how the above result of the disclosed method of high-pressure vessel fabrication is achieved. Pre-fabrication of nozzles that have grooves on both surfaces of their embedded parts, and an raised ring shoulder on the bore surface, and that are installed into the rotation mold allows us, due to an increased internal pressure in the vessel, to improve the tightness of the joint between the gas-tight liner and the nozzle, and to prevent parting of the inner gas-tight liner from the nozzle under cyclical loading conditions. Fabrication of the inner seamless gas-tight liner from a polymer material by using forming as described above enables us to reduced the number of operations in the course of inner liner fabrication to one, and, therefore, to simplify the method and to bring the cost down.

Fabrication of the outer structural overwrap by attaching the inner gas-tight liner on one nozzle, so that it can be rotated, and subsequent winding of dry reinforcing filaments as described above ensures that the vessel has equal strength properties at all points, even under cyclical loading conditions. Winding dry reinforcing filaments allows us to speed up their winding onto the gastight liner 20 times and more compared with wet impregnated filament winding. Impregnation of reinforcing filaments with binder in vacuum allows for full impregnation of the reinforcing layer by binder.

Binder polymerization at a temperature below the temperature of softening of the inner, liner material allows for the required vessel strength to be achieved without destroying the inner gas-tight liner. Inner gas-tight liner fabrication from a polymer material with sufficient rigidity to maintain the shape of the vessel throughout the reinforcing filament winding process ensures vessel gas-tightness under cyclic loading at operating pressure.

A cross-section of a high-pressure vessel fabricated using the disclosed method is shown in Fig. 1 including inner gas-tight liner 1, outer structural overwrap 2, nozzle 3, groove 4, and raised ring shoulder 5. Prior to fabrication of the inner gas-tight liner 1, nozzles 3 are fabricated, grooves 4 are formed on both surfaces of the embedded parts of said nozzles, and raised ring shoulder 5 is formed on the inner bore surface neat nozzle outlets. To fabricate the inner seamless gas-tight liner 1 by rotation molding, nozzles 3 are installed in a rotation mold, and polymer material is added. The mold is placed on a device that rotates in two planes perpendicular to each other, is heated in an oven until the polymer is fully melted, and than cooled by air. In the course of fabrication of reinforcing overwrap 2, inner gas-tight liner 1 is attached at one point using one nozzle 3, so that it can be rotated, and dry reinforcing filaments are wound on it, starting from a point next to nozzles 3 by rotating liner 1 and using a filament applicator that goes around the free-end nozzle 3 of liner 1. After the first layer winding is completed, the layer-by-layer winding on liner 1 is repeated. When winding each subsequent layer, the axis of rotation of liner 1 is shifted relative to the axis of rotation of the filament applicator by an angle 4) of at least 2 degrees. The number of coils and layer thickness is reduced for each subsequent layer. Dry reinforcing filaments are impregnated by binder in vacuum and binder polymerization takes place at a temperature that is lower than the temperature of inner liner material softening. The inner gas-tight liner may be made of a polymer material, whose rigidity is sufficient to maintain the shape during reinforcing filament winding and ensure gas-tightness when the vessel is filled and pressurized to its operating pressure.

The high-pressure vessel design has been developed taking into account that the seamless polymer liner sustains pressures from winding of the outer structural overwrap using reinforcing filaments and a winding device and single-side loading related to tensioning of reinforcing filaments that is placed on the mandrel. Based on said loads a material has been selected that has sufficient rigidity to retain the shape in the process of reinforcing filament winding and ensure gas-tightness after multiple filling of the vessel to its operating pressure. Additionally, the nozzle and neck of the vessel have been designed to withstand torques generated by opening and closing valves in the process of vessel operation.

Calculations show that a high-pressure vessel fabricated using the disclosed method is capable of withstanding high operating pressures of 25 MPa and higher and retaining gas- tightness after numerous loading cycles, up to 10,000 cycles or more.

The disclosed high-pressure composite vessel, due to its simplicity and ease of fabrication, combined with low cost, can be used for storing and transporting low-compressibility gasses and may be used, for example, as a tank for high-pressure gas refueling trucks.

While a number of exemplary aspects and embodiments have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions and sub combinations thereof. It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions and sub-combinations as are within their true spirit and scope.

Claims

1. A high-pressure vessel fabrication comprising a gas-tight inner liner fabrication, an outer structural overwrap fabricated by reinforcing a filament winding onto the gas-tight inner liner, and an overwrap polymerization, wherein prior to rotational molding of an inner seamless polymer liner, nozzles are manufactured for subsequent installation into a rotational mold that have grooves on both surfaces of embedded portions and a raised ring shoulder on the surface of a bore near an outlet of the nozzle.

2. The high-pressure vessel fabrication of claim 1, wherein the inner gas-tight liner is attached to one nozzle for rotating

3. The high-pressure vessel fabrication of claim 1, wherein dry reinforcing filaments winding begins next to the nozzle by rotating the liner and using a filament applicator that goes around a free-end nozzle of the liner

4. The high-pressure vessel fabrication of claim 1, wherein after application of a first layer, the multi-layer overwrap winding is continued, and for each layer the overwrap rotation axis is shifted relative to the filament applicator axis of rotation by an angle of no less than 2 degrees, and the number of coils in each layer and the thickness of each subsequent layer is decreased

5. The high -pressure vessel fabrication of claim 1, wherein reinforcing filament impregnation by binder occurs in vacuum

6. The high-pressure vessel fabrication of claim 1, wherein binder polymerization occurs at a temperature below that of softening of the inner liner material.

7. The high-pressure vessel fabrication of claim 1, wherein the inner gas-tight liner is made of a polymer material whose rigidity is sufficient to sustain the shape during reinforcing filament winding and ensure gas-tight seal when the vessel is filled and pressurized to its operating pressure.