System and method for charging and sealing pressure vessels

Abstract

A redundant sealing system includes a seal assembly for a vacuum or pressurized gas or liquid container, where the container has a fill port opening and a boss extending from a surface of the container. The boss has a passage aligned with the opening, and the passage has a threaded portion. The seal assembly includes a port plug having a nose portion with a surface shaped to mate with the fill port opening in the container and a set screw portion with external threads for engaging the threaded portion of the passage through the boss to press the nose portion into the fill port opening to form a first seal. The seal assembly further includes a weld plug sized to close the distal end of the passage through the boss, the weld plug is welded to the boss to form a second seal.

We claim: 
     
         1 . A seal assembly for a pressurized container, the container having a fill port opening and a boss extending from a surface of the container, the boss having a passage aligned with the opening, the passage having a threaded portion, the seal assembly comprising a port plug having a nose portion with a surface shaped to mate with the fill port opening in the container and a set screw portion with external threads for engaging the threaded portion of the passage through the boss to press the nose portion into the fill port opening to form a seal. 
     
     
         2 . A seal assembly as set forth in  claim 1 , where the nose portion is a malleable material. 
     
     
         3 . A seal assembly as set forth in  claim 2 , where the nose portion is brass. 
     
     
         4 . A seal assembly as set forth in  claim 1 , where the nose portion has a cone-like shape with a proximal end that is smaller than the opening and a distal end that is larger than the opening. 
     
     
         5 . A seal assembly as set forth in  claim 1 , where the set screw portion has a drive means at a distal end for engaging the set screw portion and advancing or retracting the set screw portion in the passage relative to the boss. 
     
     
         6 . A seal assembly as set forth in  claim 1 , where the seal is a first seal and further comprising a weld plug sized to close the distal end of the passage through the boss, the weld plug being welded to the boss to form a second seal. 
     
     
         7 . A seal assembly as set forth in  claim 6 , where the container and the weld plug are steel. 
     
     
         8 . A seal assembly as set forth in  claim 6 , where the weld is one of an axial weld and a radial weld or a combination of the two. 
     
     
         9 . A seal assembly as set forth in  claim 1 , where the boss is generally tubular. 
     
     
         10 . A seal assembly as set forth in  claim 1 , where the boss has a circular cross-section. 
     
     
         11 . A pressurized container, comprising a fill port opening and a boss extending from a surface of the container, the boss having a passage aligned with the opening, the passage having a threaded portion; and a seal assembly as set forth in  claim 1  for sealing the opening and the passage. 
     
     
         12 . A method of charging a container with gas or liquid and then sealing the container, comprising the following steps:
 (a) providing a container having an opening therein and a boss extending from a surface of the container adjacent the opening, the boss having a passage aligned with the opening in the container, the passage being at least partially threaded with internal threads, a port plug that includes a nose portion for closing the fill port opening in the container and a set screw portion with external threads for engaging the threaded portion of the boss;   (b) inserting the port plug in the passage with the nose portion closer to the opening than the set screw portion;   (c) charging the container with a pressurized gas or liquid via the passage;   (d) torquing the threaded port plug to advance the port plug in the passage until the nose portion engages the surface of the container adjacent the opening to create a first seal;   (e) installing a weld plug into an outer end of the boss to close the passage through the boss; and   (f) welding the weld plug to the boss to create a second seal.   
     
     
         13 . A method as set forth in  claim 12 , where the torquing step includes deforming the nose portion to mate with a surface of the container adjacent the opening. 
     
     
         14 . A method as set forth in  claim 12 , where the welding step includes forming at least one of a radial weld or an axial weld or a combination of the two. 
     
     
         15 . A method as set forth in  claim 12 , where the charging step occurs before the inserting step. 
     
     
         16 . A method as set forth in  claim 12 , where the installing step and the welding step are the last two steps, and the installing step occurs before the welding step. 
     
     
         17 . A method as set forth in  claim 12 , comprising the step of testing the integrity of the first seal before the step of installing the weld plug. 
     
     
         18 . A method as set forth in  claim 17 , where if the testing step shows that the first seal is inadequate, removing and replacing the port plug and then repeating the testing step until an adequate seal is obtained. 
     
     
         19 . A gas container with a seal assembly, the container having an opening therein and a boss extending from a surface of the container adjacent the opening, the boss having a passage aligned with the opening in the container, the passage being at least partially threaded with internal threads; means for sealing the opening in the container, adjacent the opening at a proximal end of the passage through the boss; and means for sealing the passage through the boss, adjacent a distal end of the passage through the boss. 
     
     
         20 . A container and seal assembly as set forth in  claim 19 , where the opening-sealing means includes a port plug having a nose portion with a surface shaped to mate with the fill port opening in the container and a set screw portion with external threads for engaging the threaded portion of the passage through the boss to press the nose portion into the fill port opening to form a seal, and the passage-sealing means includes a weld plug sized to close the distal end of the passage, the weld plug being welded to the boss to form a second seal.