Thermoplastic liner for and method of overwrapping high pressure vessels

• US 5,499,739 A
• Filed: 01/19/1994
• Issued: 03/19/1996
• Est. Priority Date: 01/19/1994
• Status: Expired due to Fees

• Current Assignee: Aerojet-General Corporation (L3Harris Technologies, Inc.)
• Original Assignee: Atlantic Research Corporation (L3Harris Technologies, Inc.)
• Inventors: Greist, Darton III, Figge, Irving E. Sr.
• Primary Examiner(s): MOY, JOSEPH MAN
• Application Number:
  US08/183,452
• Time in Patent Office: 790 Days
• Field of Search: 220/414, 220/589, 138/30, 138/109
• US Class Current: 220/589
• CPC Class Codes: B29C 53/602 for tubular articles having closed or nearly closed ends, e.g. vessels, tanks, containers
• CPC Class Codes: B60K 15/03006 Gas tanks B60K15/07 takes precedence
• CPC Class Codes: F17C 1/06 built-up from wound-on bands or filamentary material, e.g. wires
• CPC Class Codes: F17C 2201/0109 with exteriorly curved end-piece
• CPC Class Codes: F17C 2201/035 with substantially horizontal main axis
• CPC Class Codes: F17C 2203/0604 Liners
• CPC Class Codes: F17C 2203/0607 Coatings
• CPC Class Codes: F17C 2203/0665 radially wound
• CPC Class Codes: F17C 2203/067 helically wound
• CPC Class Codes: F17C 2205/0397 on both sides of the pressure vessel
• CPC Class Codes: F17C 2209/2154 Winding
• CPC Class Codes: F17C 2221/033 Methane, e.g. natural gas, CNG, LNG, GNL, GNC, PLNG
• CPC Class Codes: F17C 2223/0123 gaseous, e.g. CNG, GNC
• CPC Class Codes: F17C 2223/036 Very high pressure (>80 bar)
• CPC Class Codes: F17C 2260/011 Improving strength
• CPC Class Codes: F17C 2270/0168 by vehicles

Abstract

A pressure vessel liner for fuel tanks used to store high pressure gasses including methane or compressed natural gas includes thermoplastic materials exhibiting low permeability and mechanical properties resistant to thermal and pressurization strains over the operating cycle of the fuel tanks. The pressure vessel liner is made from a material selected from the group consisting of modified nylon 6 or nylon 11. The present invention also discloses a method of forming a reinforced composite fuel tank wherein the pressure vessel liner is overwrapped with both low-angle helical and high-angle helical filament windings. The high-angle helical windings are overwrapped around the liner across at least the cylinder-to-dome transition region at angles between 60° and 88° with respect to the longitudinal axis of the liner. High angle helical filament windings at these angles eliminate excessive composite windings typically added to account for weak transition points in these regions. The high-angle helical windings can be effectively wound without slippage, thereby providing a simplified overwrapping process and improved reinforced liner construction.

Claims

1. In a high pressure vessel liner made of a thermoplastic material, said high pressure vessel liner forming a chamber with at least one opening therein for storing highly pressurized gas, the improvement comprising said thermoplastic material being a material selected from the group consisting of a modified nylon 6 and nylon 11, said high pressure vessel liner exhibiting low permeability to pressurized hydrocarbon gases and acceptable ductility over a temperature range of about -40°

F. to 140°

F.

2. The high pressure vessel liner of claim 1 wherein said thermoplastic material is modified nylon 6.

3. The high pressure vessel liner of claim 1 wherein said thermoplastic material is nylon 11.

4. The high pressure vessel liner of claim 1 wherein said thermoplastic material exhibits a permeation coefficient of no greater than 6 cc mil/atm day 100 in² to methane.

5. The high pressure vessel liner of claim 1 wherein said thermoplastic material exhibits an ultimate strain at -40°

F. of no less than 7.94%.

6. In a high pressure vessel liner for containment of highly pressurized gases wherein said high pressure vessel liner comprises a cylindrical portion and at least one dome portion, said cylindrical portion separated from said dome portion by a cylinder-to-dome transition region and wherein a high,pressure vessel liner is overwrapped with filaments in both a helical orientation to react the axial stress and a high angle helical orientation to react the radial stress, the improvement comprising a portion of said filaments being overwrapped around said high pressure vessel liner at least in said cylinder-to-dome transition region in a high angle helical orientation wherein an angle between each said filament of said portion of overwrapped filaments and a longitudinal axis of said high pressure vessel liner is about between 60°

and 88°

, such that each said filament of said portion of overwrapped filaments can be wound past the tangent point and is retained in place without slippage in said cylinder-to-dome transition region when overwrapped wherein said pressure vessel liner is made of a thermoplastic material selected from the group consisting of a modified nylon 6 and nylon 11, said high pressure vessel liner exhibiting low permeability to pressurized hydrocarbon gases and acceptable ductility over a temperature range of about -40°

F. to 140°

F.

7. The high pressure vessel liner of claim 6 wherein said thermoplastic material is modified nylon 6.

8. The high pressure vessel liner of claim 6 wherein said thermoplastic material is nylon 11.