Hydrogen Bake Out is a heat treatment process that drives out any hydrogen that may have occurred during welding or that has seeped into the parent metal of an in-service process pipe, vessel or structure. Hydrogen occurs in metals, such as steel, on a molecular level when hydrogen gets absorbed into the metal.
If this is left undetected, it can lead to hydrogen cracking and may lead to mechanical failure of the pipe, vessel, or component being welded. Some metals are more susceptible than others and allowing a certain timeframe to allow hydrogen to diffuse into the metal before any weld inspections are made is not unheard of in the industry. This type of cracking has many names in the industry, and is often called:
The process of dehydrogenization heat treatment involves heating the specific area plus a predetermined area close to where the welding will take place, a minimum of 2 feet on either side of the area to be welded is recommended in the codes and standards. This involves utilizing electrical resistance heating elements or induction coils around the area and heated to a range of 600 – 700 degrees. The area requires to be held at this hydrogen bake out temperature (soak) for a time sufficient to drive the excess hydrogen out of the metal, usually 4 to 6 hours. There are no set heat up and cool down rates specific to hydrogen bake-outs as the temperatures being used are below the critical metal transformation temperatures. Once sufficient time has elapsed, the heating elements/coils, thermocouples and insulation can be removed to allow access. Axiom’s ability to understand the nuances around Hydrogen Bake Out heat treatment and plan the work scope efficiently allows our customers to plan for their work accordingly. Axiom helps get you back to production quicker.