The HSP is not familiar with this particular fitting or its potential application in H2 service but can offer engineering judgment. Many similar compression-type swaged fittings are used in H2 service. These fittings must be used within the manufacturer recommendations for pressure, temperature, and fluid service. Deformation is also introduced into stainless steel tubing in other ways, such as creating bends, but these locations are not reported to be more vulnerable to failure in H2 service provided that they are within an acceptable range.   

This is probably 300-series stainless steels, particularly 316, that are resistant to hydrogen embrittlement under static stress, although cyclic stresses add the potential for hydrogen-assisted fatigue cracking. One area of caution when applying the fitting to 304 piping is the potential to form strain-induced martensite (phase with magnetic signature) in the stainless steel. The martensite phase is more susceptible to hydrogen embrittlement than the surrounding matrix, and a widely recognized best practice is to limit the formation of these phases with magnetic signature for stainless steels in hydrogen gas service.

As with all compression-style fittings, there is a significant risk of incorrect or incomplete installation. Examples include failure to install the ferrules, installation of the ferrules in the wrong order or backwards, incomplete insertion, and incomplete tightening to reach the proper swaging of the tubing to ensure the necessary grip at high pressure. Fittings should always be inspected, either visually or with appropriate tools, and pressure tested prior to putting into service.