WO2021220305A1

WO2021220305A1 - Non-metallic end cap for a composite pressure vessel

Info

Publication number: WO2021220305A1
Application number: PCT/IN2021/050419
Authority: WO
Inventors: Janardhanan THIRUMALAI VINCHIMOOR
Original assignee: Thirumalai Vinchimoor Janardhanan
Priority date: 2020-04-29
Filing date: 2021-04-29
Publication date: 2021-11-04

Abstract

The present invention is intended to present a solution to weight reduction and mass production needs without compromising strength, fatigue performance and level safety of the liner (2) of the composite pressure vessel (11). The present invention achieves the above object by strengthening the seamless transition region (12) of the liner (2) through mass production feasible non-metallic end cap (1) which is made of weightless non metallic material. The end cap (1) is having a contoured inner surface region (8), contoured outer surface region (9) and seamless fluid port covering region (10). The contoured inner surface region (8) slidably engaged with a seamless outer dome region of the liner (2) and allow a fluid flow port (3) through the end cap's (1) fluid port covering region (10) thereby strengthening the seamless transition region (12).

Description

TITLE: "NON-METALLIC END CAP FOR A COMPOSITE PRESSURE VESSEL"

FIELD OF INVENTION

This invention pertains generally to pressure vessel, and in particular to a structural component which provides additional strength and improves fatigue performance and level safety of composite pressure vessels. The subject patent relates to added non-metallic structural component such as, end cap that is precisely attached at the composite pressure vessel dome end to provide strength and stiffness.

BACKGROUND OF THE INVENTION

Pressure vessels are often designed and constructed in a spherical shape or cylindrical shape and ends closed with end domes with spherical, elliptical, or other shapes including isotensoid configuration for composite overwrapped pressure vessels.

Among the primary causes of even adequately designed pressure vessel failure is due to fatigue crack initiation and growth to critical level. In this aspect, welded joints, and the dome regions are susceptible. Over past decades, composite cylinders with load sharing metallic liners have been in use for a variety of applications including, aircraft, aerospace and hazardous materials transportation applications.

Generally, the metallic liner is a load sharing component and is required to withstand all service-related loads. The liners are generally seamless fabricated starting from a thick-walled forge formed cap and ends closed by either forging or metal forming method. In order to mitigate the fatigue failure possibility complex spin forming process is required to build sufficient thickness in the dome region. The process is time consuming, and expensive and not conducive to fast mass production. The composite overwrapped pressures vessels (COPV- Type III) are now a preferred motor vehicle on-board gaseous fuel storage tanks for CNG and Hydrogen Fuel Cell applications.

An alternate COPV design method is to use non-load bearing nonstructural liner, such as blow molded HDPE or equivalent material used to make a shell with adhesive bonded metallic fittings s for inlet /outlet valves etc.

These type tanks are designed and manufactured to national and international standards and specifications, and compliance with the government regulations.

The proposed patent is focusing on the improvement over the recently issued patent, (Indian Patent NO: 329981) wherein the innovative method of adding end cap to thin walled metallic liner ends provided and extensive advantage over prior art, in that it provided added level of safety, relatively easier and more efficient manufacturing process, versatility of end uses and this reduced product costs.

Because of significant need and growth of alternate fuel storage systems, the use of compressed gas storage at high and ultra- high pressures has become a viable solution. Fiber-reinforced polymer composite pressure vessel technology, used well over 100 years, has provided lightweight components for aircraft, aerospace, automobile and other applications. As the need for storage at higher pressures for hydrogen, mixtures of natural gas and hydrogen (Hythane) etc., Type 3 composite cylinder with non-permeable metallic liner is one of the preferred solutions for on board fuel storage. Until recent Indian granted patent 329981, for new entrants to composite tank industry manufacturing process of metallic seamless liner for Type 3 cylinders has been a difficult hurdle cost because of complexity, and cost to overcome. The patent 329981 alleviated this hurdle by adding complimentary structural component namely the metallic end added to the end domes.

The cited patent preferentially focused on COPV Type III composite cylinders because of the need of the times, and to obtain a product that will meet international and national regulations.

The proposed patent is focusing on taking advantage of the fact that by adding load sharing component to a primary structure, the product performance, ease of product manufacturing process and reduced costs.

Not only COPV, many of the complimentary load bearing components are manufactured by a variety of materials and methods provide added value to a primary structure such as, for example, automobile crash bumper, aircraft and aerospace weight sensitive parts. These kinds of structural members must bear substantial load sharing, such as those used in automobile bodies or frames, machinery, building construction, etc., commonly must be formed into complex shapes. Many manufacturing processes for axis symmetric components such as the subject end cap provide substantial ease of manufacturing method and cost reduction.

The granted patent 329981 added over previously available technology,

1. Enhanced performance, 2. Simplified manufacturing process and

3. Significant manufacturing cost reduction.

Figure 1 illustrates one of the embodiments of the granted patent 329981 which shows the metallic end cap configuration in the liner. Part no 110 depicts the metallic end cap, 103 depicts the seamless side wall, 102 depicts the entire top end, 101 depicts the entire bottom end.

Now, the proposed patent will utilize "non-metallic end cap" instead of metallic end cap 110 shown in figure 1 to enable; faster production rate and further cost reduction compare with the above granted Indian patent no 329981.

OBJECT OF THE INVENTION

An object of the invention is to overcome the disadvantages of existing "metal end caps".

Another object of the invention is to replace the metallic end cap with ceramic and non-metallic composite end cap to achieve faster production rate, multiple strengthening process in the seamless transition region and further weight and cost reduction.

Yet another object of the invention is to further simplify the manufacturing process of end cap.

Yet another object of the invention is to reduce the overall cost of the composite overwrapped pressure vessel. Yet another object of the invention is to achieve labor-saving and high-speed automated techniques.

Yet another object of the invention is to provide a solution for manufacturing complex shaped end caps and components.

Yet another object of the invention is to replace the requirement of metal end caps for liner without compromising strength and safety requirements.

Yet another object of the invention is to make this end cap is capable also for fitting with non metallic liner.

Further object of the invention is to provide a pressure vessel end cap which is non- metallic and, thus, eliminates the coating requirement and corrosion problems often encountered when metallic fittings are used.

SUMMARY OF THE INVENTION

The present invention is intended to present a solution to weight reduction and mass production needs without compromising strength, fatigue performance and level safety of the liner of the composite pressure vessel. As such, and for purposes of clarity in describing the structural features of many of the preferred embodiments, the present invention is directed to an end cap for strengthening seamless transition region of the liner of the pressure vessel by means of non metallic end cap. The liner includes a seamless cylindrical tube comprising a top and bottom ends contoured into a dome at both ends, wherein the dome seamlessly transitions from the seamless cylindrical tube, a closeable fluid port seamlessly transitions from any one or both ends of the dome for communication with fluid source external to the vessel. Particularly, the non-metallic end cap is structured to slidably engage its inner contoured region around the outer contoured region of a dome of the liner thereby strengthening seamless transition region.

BRIEF DESCRIPTION OF THE INVENTION

Figure 1 illustrates one of the embodiment of the granted Indian patent no 329981. Figure 2 illustrates embodiment of the proposed invention.

Figure 3 illustrates the embodiment of the invention particularly shows the contoured inner and outer surface region.

Figure 4 illustrates the evolution of proposed invention, figure 4a illustrates conventional thick-walled liner, figure 4b illustrates the liner along with metal end caps of the Indian patent no 329981 and figure 4c illustrates the liner and proposed non metallic end cap configurations and

Figure 5 illustrates formation of pressure vessel by using proposed non-metallic end cap.

The above drawing illustrates the details given and will be provided with respect to certain specific embodiments. It is to be understood that the scope of the disclosure should not be limited to such embodiments but that the same are provided simply for enablement and best mode purposes. The breadth and spirit of the present disclosure is broader than the embodiments specifically disclosed and encompassed within the claims eventually appended hereto.

DETAILED DESCRIPTION OF THE INVENTION

One of the preferred embodiments of the invention discloses an end cap (1) for strengthening seamless transition region (12) of a liner (2) of a pressure vessel (11) by means of mass production feasible and weightless non metallic end cap (1). The end cap (1) comprises of a contoured inner surface region (8), contoured outer surface region (9) and seamless fluid port covering region (10), wherein the contoured inner surface region (8) slidably engaged with a seamless one (6 or 7) or both (6 and 7) outer dome region of the liner (2) and allow the fluid flow port (3) through the fluid port covering region (10) of any one or both of the end cap (1) thereby strengthening seamless transition region (12).

Another embodiment of the invention discloses about the liner (2) of the pressure vessel (11). The liner capable of being a metallic or non metallic material. The non metallic end cap can be engaged with any types of liner irrespective of materials. Yet another embodiment of the invention discloses the non metallic end cap (1) is made of HDPE or Carbon Fiber or Glass Fiber or Kevlar or Basalt or Bio-Fibers or Hybrid Fiber or ceramic or combination thereof.

Yet another embodiment of the invention discloses about the properties of the non metallic end cap (1). The present invention provides a structural composite end cap (and a representative method by which it may be manufactured) which has required isotropic or quasi isotropic mechanical properties, and which can be manufactured in a continuously contoured shape capable of supporting loads. The methods permit manufacture of such structural composites using labor-saving, high-speed automated techniques.

Yet another embodiment of the invention discloses about non-metallic end caps which can be manufactured using a variety of materials and their combination and manufacturing processes.

The feasible manufacturing methods are

1. Filament winding,

2. Compression molding,

3. Vacuum compression molding,

4. Resin Transfer molding,

5. Vacuum Resin Transfer molding,

6. Magnetic Resin Transfer molding,

7. Injection molding and

8. Reaction Injection molding.

Yet another embodiment of the invention discloses about another manufacturing method is called 3D- printing. The 3D printing is an additive manufacturing method thus support to achieve the non-metallic end cap manufacturing process with the following benefits:

1. Faster production rate,

2. Assorted raw materials usage and

3. less waste.

Those advantages further simplify the non-metallic end cap manufacturing process.

Yet another embodiment of the invention discloses about resins / binders used in the manufacturing process of the non metallic end cap (1), the possible resins / binders are thermosetting and thermoplastic.

Yet another embodiment of the invention discloses about the evolution of proposed invention, figure 4a illustrates conventional thick walled liner (2), figure 4b illustrates the liner (2) along with metal end caps of the Indian patent no 329981 and figure 4c illustrates the liner and proposed end cap configurations.

Wherein, XI, X2 and X3 represents wall thickness of different liner.

XI denotes wall thickness of conventional liner,

X2 denotes wall thickness of liner, patent no 329981 and

X3 denotes wall thickness of liner of proposed patent. In one embodiment of the invention, the wall thickness of XI is always greater than the thickness of X2 and X3.

Yet another embodiment of the invention discloses about mass reduction due to non metallic end cap (1) in the liner (2) of the pressure vessel. Generally, sheet metal forming is a process where pieces of sheet metal are modified to its geometry rather than removing any materials. The applied process generates a force that stresses the material to deform. To compensate the impacts exerted on the deformed regions, there is a requirement for multiple strengthening processes. The granted patent eliminates the multiple strengthening processes by means of metallic end caps, which reduces the strengthening process and achieves the desired thickness and safety aspects. But those metallic end caps again need forming process and mass production feasibility is low, the proposed patent replaces the end cap with non metallic end cap which further reduces the mass and simplify the manufacturing process. Refer the figure 4a, 4b and 4c which represents the mass differences of end caps. Wherein, M is a mass of conventional liner's dome region (refer figure 4a). Mia is a mass of patent no 329981 liner's dome region M2a is a mass of metal end cap (Refer figure 4b). While comparing the mass of conventional and patent no 329981 liner's dome region, conventional dome mass is greater than or equal to the prior art 329981 mass. But, comparing the mass of the metal end caps (Mlb), the proposed patent's end cap mass (M2b) (Refer figure 4c) is lesser than the mass of prior art mass (Mlb).

Yet embodiment of the invention discloses about the manufacturing method of the composite high-pressure vessel using non metallic end cap (1) of the liner (2) (Refer figure 5). The method comprises the steps of; obtaining the liner from the farming process, in this first stage aluminium thin walled extruded tubes were used. Next stage, the non-metallic end caps being obtained from moulding or additive 3D manufacturing or filament winding. In this stage, the proposed patent eliminating the need of metallic end cap and replacing the same with non metallic end cap (1). Prior to final stage, Slidably engaging the non metallic end cap (1) with the outer dome region of the liner (2). Final stage, carrying out filament winding with carbon fiber or glass fiber of Kevlar to obtain composite pressure vessel. Yet another embodiment of the invention discloses about the end cap (1) retrofit option, the end cap (1) can be retrofit with any existing liner to provide additional strength and stiffness thereby achieving the desired standards or permeability or passing the safety level.

Further embodiment of the invention discloses about the end cap (1), plurality of end cap (1) sequentially arranged either one (6 or 7) or both end (6 and 7) of the dome to provide additional safety and stiffness with respect permeability of the gas and pressure level of the composite pressure vessel (11). Once the liner is standardized, the end cap only altered to achieve desired safety and permeability levels. The used end cap (1) may be obtained from same or different manufacturing process and the materials used in the end cap (1) may be same or different materials.

ADVANTAGES

• Light weight with further reduction to overall liner weight.

• Ease of manufacture and can get into high volumes to meet growing demand.

• Significant reduction in manufacturing process, time and costs.

• Can work with different configurations for different high-pressure applications- Viz cylinders store a range of pressures.

• Depending on application we can work with thickness variations and reduce overall weight and cost.

• Stops multiple strengthening processes required to strengthen the liner,

• Compensate the mechanical conversion losses of the liner as well as existing metal end caps. • Easy to adapt with any existing liner and

• Flexible to use same or different manufacturing process and materials with respect to safety standards and permeability of the gas used in the composite pressure vessel.

So that the manner in which the features, advantages and objects of the invention, as well as others which will become apparent, may be understood in more detail, more particular description of the invention briefly summarized above may be had by reference to the embodiment thereof which is illustrated in the appended drawings, which form a part of this specification. It is to be noted, however, that the drawings illustrate only a preferred embodiment of the invention and is therefore not to be considered limiting of the invention's scope as it may admit to other equally effective embodiments.

Claims

1. An end cap (1) for strengthening seamless transition region (12) of a liner (2) of a pressure vessel (11) by means of mass production feasible and weightless non metallic end cap (1), the end cap (1) comprises of;

• a contoured inner surface region (8), contoured outer surface region (9) and seamless fluid port covering region (10),

• wherein the contoured inner surface region (8) slidably engaged with an seamless one (6 or 7) or both (6 and 7) outer dome region of the liner (2) and allow the fluid flow port (3) through the fluid port covering region (10) of any one or both of the end cap (1) thereby strengthening seamless transition region (12).

2. The end cap (1) as claimed in claim 1, wherein the liner (2) is a non-metallic liner.

3. The end cap (1) as claimed in claim 1, wherein the non metallic end cap (1) is made of HDPE or Carbon Fiber or Glass Fiber or Kevlar or Basalt or Bio-Fibers or Hybrid Fiber or ceramic or combination thereof.

4. The end cap (1) as claimed in claim 1, wherein the end cap (1) being obtained through molding or additive 3D manufacturing or filament winding.

5. The end cap (1) as claimed in claim 1, wherein the end cap (1) is retrofit with any existing liner to provide additional strength and stiffness.

6. The end cap (1) as claimed in claim 1, wherein plurality of end cap (1) sequentially arranged either one (6 or 7) or both end (6 and 7) of the dome to provide additional safety and stiffness with respect to permeability of the gas and pressure level of the composite pressure vessel (11).