Tech Briefs

This process is an alternative to a prior explosive welding process.

A special double-wall container and a process for utilizing the container are being developed to enable (1) acquisition of a sample of material in a “dirty” environment that may include a biological and/or chemical hazard; (2) sealing a lid onto the inner part of the container to hermetically enclose the sample; (3) separating the resulting hermetic container from the dirty environment; and (4) bringing that hermetic container, without any biological or chemical contamination of its outer surface, into a clean environment. The process is denoted “S3B” (separation, seaming, and sealing using brazing) because sealing of the sample into the hermetic container, separating the container from the dirty environment, and bringing the container with a clean outer surface into the clean environment are all accomplished simultaneously with a brazing operation. This container and process were conceived as a superior alternative to the double-wall container and process described in “Explosion Welding for Hermetic Containerization” (NPO-20868), NASA Tech Briefs, Vol. 27, No. 8 (August 2003), page 46. As in the previously reported case, the present container and process were originally intended to be used to return samples from Mars to Earth, but could also be used on Earth to store and transport material samples acquired in environments that contain biological and/or chemical hazards.

Figure 1. Before the S3B Process, the double-wall container and the sample inside it are in the dirtyenvironment.
Figure 1 depicts the configuration, prior to the S3B process, of the double-wall container and an interface assembly that includes a structure that holds the lid and serves as a barrier between the clean and dirty environments. The upper end of the container is sized and shaped to mate with the lid. For the S3B process, the outer wall of the double-wall container includes, near its upper end, integral portions in the form of three rings of a brazing material that melts at a temperature well below the melting temperature of the rest of the container. There is also a similar ring of brazing material on the upper surface of a flange that is part of, and near the upper end of, the outer wall. Inside the lid and on the structure that holds the lid are similar rings of brazing material positioned to mate with those on the double-wall container. The middle ring of brazing material on the cylindrical portion of the outer wall occupies the full thickness of the wall; similarly, the mating middle ring of brazing material in the cylindrical portion of the lid occupies the full thickness of that part of the lid. On the clean side, an induction-heating coil surrounds the lid. At the bottom end of the double-wall container, between the inner and outer walls, are springs poised to push the inner portion of the container lengthwise out of the outer portion.

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