Pressure vessel

The present disclosure provides a pressure vessel 10 (sometimes known as a composite overwrapped pressure vessel or “COPV”) comprising carbon fiber 20 (such as carbon fiber 20 filaments) wrapped around a tank liner 30.

FIELD OF THE DISCLOSURE

The present disclosure pertains to vessels for the transport of pressurized gases and liquids. More specifically, in one embodiment, the present disclosure pertains to vessels for the transport and storage of compressed natural gas (“CNG”), propane, methane, alcohol, helium, hydrogen or argon.

BACKGROUND

The desire to supply more environmentally friendly (so called “green”) fuels for automobiles and other uses has greatly increased the demand for pressure vessels that can both store and be used in the transport of the fuels. Once of the most promising fuels today is CNG, and the need for cost effective ways of producing pressure vessels for CNG vessels has arisen.

Generally, the two most expensive features of a CNG pressure vessel are the carbon fibers and the tank liners (around which the carbon fibers are wrapped). The cost of the carbon fibers is largely driven by the free market and thus pressure vessel manufacturers can do little to control or reduce the cost of the carbon fibers. Accordingly, reducing the cost of the tank liners is desirable.

The most common types of pressure vessels used are: type 3 (metal lined) and type 4 (plastic lined) vessels. There is also a new type 5 vessel being considered by industry. The type 5 vessel is considered to be all-composite (no metallic or non-metallic liner). It may also be considered to be a type 5 vessel if it has a very thin permeation barrier on the inside if it is also non-loadbearing. This disclosure can be applied to a type 4 and/or a type 5 vessel. The common type 3 vessel tank liner is aluminum, but there are also some tank liners produced by welded steel assemblies. The aluminum tank liner size limit is controlled by the diameter of available tube forgings. The diameter size usually stops around 18″. There are new emerging markets for trucks and bulk storage systems that need 25″ diameter tank liners or larger. This need for the larger diameters has been one of the reasons that more type 4 vessels are being developed. The manufacturing methods for the larger type 4 liners can be costly if there are frequent design changes because the molds and tooling are expensive. The new type 4 vessels however are lighter and cheaper than the aluminum liners for type 3 vessels.

The production of tank liners however, is not straight forward as it requires specialized tooling and other equipment, and the costs of the required equipment present a significant entry barrier in the industry.

The present disclosure provides a pressure vessel useful in the transport and storage of gases and liquids, such as CNG that comprises a tank liner with segments that can be bonded together. The pressure vessel of the present disclosure allows for modular manufacturing that is cost effective and readily adaptable to change, more robust end fittings and domes.

DETAILED DESCRIPTION

The present disclosure provides a pressure vessel10(sometimes known as a composite overwrapped pressure vessel or “COPV”) comprising fibers20(such as carbon fiber20filaments) wrapped around a tank liner30. The fibers20can also be used with embedded layers of fabric or other textiles to enhance performance as needed as would be recognized by one of skill in the art.

Any fiber20known in the art can be used with the pressure vessel10disclosed herein. For example, typical carbon fiber20for pressure vessels10have a tensile strength about 700 kilo pounds per square inch (ksi) and a tensile modulus of about 33 million pounds per square inch (msi) or higher, so any material with similar characteristics may be used. Other fibers20overwraps include, but are not limited to, glass fiber, basalt fiber, jute twine, Zylon®, high-density polyethylene, polypropylene, polyethylene, nylon, Vectran® and high strength metal wire. In some embodiments, a carbon fiber20overwrap may also include an epoxy or a resin that acts to strengthen and harden the carbon fibers20. The present disclosure is not limited to a pressure vessel10comprising a single type of fiber20, accordingly, it is to be understood that the pressure vessel10may be wrapped (or overwrapped) with a plurality of different types of carbon fibers or other fibers20, depending upon intended use and size of the pressure vessel10. One example of a tank liner30having been overwrapped and showing some of the carbon fibers20overwrapped onto the tank liner30is shown inFIG. 1. The fibers20may be wrapped at a continuous “depth” around the tank liner30, or certain segments of the tank liner30may be wrapped with thicker layers of fiber20. For example, an area known to be subject to greater pressure may have more fibers20overwrapped than a section under less pressure. Alternatively, different types of fibers20may be used on different areas of the pressure vessel subject to different pressures. Additionally, layering patterns may be used in connection with the present disclosure, including without limitation, fibers20wound in helical layers, polar layers or hoop layers. Additionally, individual fibers20may be wound the same or differing angles relative to the tank liner depending upon the desired traits of the pressure vessel10.

There are many suitable epoxies or resins that can be used in connection with the present disclosure. Some such resins are EPON® 828 and 862 and Dow 383, and there are a variety of different curing agents and additives that can be used to adjust the epoxy performance as needed. Additionally, the epoxy or resin can be impregnated onto the fibers20before winding or the fibers20can be “wet wound” where the epoxy or resin is added as the fibers20is wound about the tank liner30. Epoxy is the common resin matrix, but others can be used such as urethanes, polyureas, epoxy vinyl ester, bismaleimide and benzoxazine.

The present disclosure also provides a pressure vessel10with a novel tank liner30. The tank liner30may have a variety of shapes (thus imparting a similar shape on the pressure vessel10) including spherical, cylindrical or conical. Of course, combinations of the aforementioned shapes are also within the scope of this disclosure. In one embodiment, the tank liner30acts as a mandrel/tooling that holds the metal end fittings (discussed below) in place and it provides the surface for the application of the permeation barrier. The composite mandrel tooling can rely on the permeation layer50(discussed below) to contain the gasses and the mandrel can be viewed as fly-away tooling.

In one embodiment, the tank liner30comprises a plurality of segments40that are bonded together. In an alternate embodiment, the tank liner30is an integral structure comprising only one segment40. The segments40can be molded or shaped into a number of configurations. For example, as shown inFIG. 2, the tank liner30may comprise a plurality of segments40wherein one segment42forms the cylindrical body of the tank liner and two other segments44form the ends or dome caps of the tank liner. Alternatively, as shown inFIG. 3, the cylindrical body of the tank liner30may be comprised of several segments42a,42bthat are bonded together.

Depending upon the intended use of the pressure vessel10, one or both end segments44may comprise an end fitting46(typically but not exclusively, a hole drilled in the apex of the tooling for the cap segments that is then fitted with a metal fitting that interfaces with the valve connection of a gas system) that is adapted to be connected to a valve or other mechanism useful for allowing the CNG to be vented from the pressure vessel10. The metal end fitting can also be cast or wound in place with mandrel materials. Any end fitting known to those of skill in the art should be considered with the scope of this disclosure. Additionally, the type of end fitting may be varied depending upon the use of the pressure vessel10.

The segments40comprising the tank liner30may comprise many different materials. In one embodiment, the tank liner30may be comprised of a single material while in other embodiments the tank liner30may be comprised of a plurality of materials (for example, the end segments44may be comprised of a different material than the segments42forming the body of the tank liner30). The composition of the tank liner30may be varied depending upon the intended use of the pressure vessel10. In one application, the segments42and44may comprise glass fiber reinforced plastics. In an alternate embodiment the segments42and44may comprise carbon fiber reinforced plastics. In alternate constructions, the segments42may comprise a glass fiber reinforced material while the end segments44are metallic. If weight is critical, the composite tooling mandrel can be made with a carbon fiber and an epoxy matrix resin, or other resins. The composite end segments44and metal end fittings46can also be outfitted with an-o-ring or sealant material in the metal and non-metallic interfaces. An all-metallic end fitting46and end segment44is especially useful in extremely high pressure situations as the end fittings46are not bonded to the end segment44but are rather an integral part of the end segment44.

In the embodiments where the tank liner30comprises more than one segment40, the segments must be bonded to one another. The segments40can have an overlapping joint allowing for a thin bond layer of adhesive to bond the segments40together.

The tank liner30may be overwrapped directly by the carbon fiber20or it may first be covered by a permeation barrier50as shown inFIGS. 1B and 1C. The permeation barrier50can be on the inside, outside or both side of the composite mandrel tooling depending on the application. The permeation barrier50may comprise a polymer such as polyurea or polyurethane or other flexible materials. The permeation barrier50can also contain various fillers and additives to enhance the gas permeation properties. In one embodiment the permeation barrier50may also comprise an additive such as nanoparticle that helps enhance its performance, such nanoparticles could include, but not be limited to, exfoliated clays or carbon nanotubes. This permeation barrier50typically does not add strength to the structure it helps to keep the contents of the pressure vessel10from leaking out. One of the main functions of the permeation barrier50is to contain the gasses within the tank liner30. The permeation barrier50can have several layers of different materials that are used to reduce the diffusion of the gasses. Once the permeation barrier50is added over the tank liner30, the carbon fiber10may be overwrapped using a traditional filament winding machine. In one embodiment, the permeation barrier50may be interior to the tank liner30, then the tank liner30may be overwrapped with carbon fiber10. In yet another alternate embodiment, there may be two (2) permeation barriers50, one interior to the tank liner30and one exterior to the tank liner30.

The pressure vessel10of the present disclosure may be used in a number of applications such as CNG powered automobiles, shipping CNG (by land or sea) or in rockets. Additionally, one or more of the pressure vessels10disclosed herein may be included within, or surrounded by, a protective enclosure60if the pressure vessels10are being used to ship CNG. For example, four pressure vessels10may be surrounded by a protective enclosure60as shown inFIG. 4.

Although particular embodiments of the present disclosure have been described, it is not intended that such references be construed as limitations upon the scope of this disclosure except as set forth in the claims.