Gas Cylinder Gasket Melted Due To Reaction with Anhydrous Hydrogen Chloride

Key Learnings

Watch for incompatible materials in all chemical processes.  

Effects of incident 

Injury-free event: Anhydrous hydrogen chloride under high pressure could have been released into the laboratory.  

Description

A researcher used a re-configured stainless steel regulator for an upcoming experiment. The reconfiguration consisted of changing out a 350 CGA fitting with a 330 CGA fitting for anhydrous hydrogen chloride (HCl) service. The Regulator Shop performed the change-out of the CGA and supplied a white plastic gasket to seal the high-pressure fitting. After the pressure safety check, the researcher used the regulator to fill a small chamber with a small amount of HCl. Following the filling, the regulator and the filling system were evacuated.

When the HCl lecture bottle was taken off line, it was noted that the white plastic gasket had reacted with the anhydrous hydrogen chloride and melted . Apparently, the white gasket was not an inert material such as Teflon, but actually a plastic that de-polymerized when in contact with HCl.  

Causation

Inattention to compatibility of materials in contact with a toxic and corrosive gas.

Corrective Actions to Prevent Reoccurrence

  • Teflon is compatible with anhydrous hydrogen chloride, and Teflon CGA gaskets were made available to staff and users.

  • The regulator shop verified material compatibility for all gases in service.

  • Research project safety documents were revised to specify the person responsible for reviewing the compatibility between gases and materials of construction, including the gasket.

  • The incident report was shared with all researchers who use compressed gas cylinders