Manway relief for a tank car

A method of servicing an inner tank of a cryogenic tank car comprising an outer tank and the inner tank positioned within the outer tank, the method comprising:

• removing a vacuum from a first space defined by an interior surface of the outer tank and an exterior surface of the inner tank, wherein:
• an outer manway plate was secured to an outer nozzle by a differential pressure that was generated by the vacuum between the first space and a space external to the outer tank, wherein the outer nozzle defines an opening in the outer tank, the outer nozzle extending away from the outer tank and terminating at an upper edge of the outer nozzle:
• in response to removing the vacuum:
• removing the outer manway plate from the outer nozzle, wherein:
• the outer nozzle is positioned above an inner nozzle, the inner nozzle defining an opening in the inner tank;
• and
• an inner manway plate is coupled to the inner nozzle, such that the inner manway plate covers the opening in the inner tank:
• accessing the inner manway plate through the outer nozzle;
• removing the inner manway plate from the inner nozzle;
• and
• accessing the inner tank through the inner nozzle.

A cryogenic tank car comprising:

• an outer tank:
• an inner tank positioned within the outer tank;
• an inner nozzle defining an opening in the inner tank:
• an inner manway plate covering the opening in the inner tank, the inner manway plate welded to the inner nozzle:
• an outer nozzle defining an opening in the outer tank, the outer nozzle positioned above the inner nozzle, such that the inner manway plate is accessible through the outer nozzle, the outer nozzle extending away from the outer tank and terminating at an upper edge of the outer nozzle:
• an outer manway plate coupled to the upper edge of the outer nozzle, such that the outer manway plate covers the opening in the outer tank, wherein:
• a space defined by an interior surface of the outer tank and an exterior surface of the inner tank is configured to hold a vacuum;
• and
• in response to applying the vacuum to the space, a differential pressure between the space defined by the interior surface of the outer tank and the exterior surface of the inner tank and a space external to the outer tank secures the outer manway plate to the outer nozzle;
• and
• a set of wheel assemblies, wherein the outer tank is coupled to the set of wheel assemblies.