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Stress-Oriented Hydrogen Induced Cracking (SOHIC)

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Stress-Oriented Hydrogen Induced Cracking (SOHIC) is a common, insidious form of wet H2S cracking made up of a series of hydrogen induced cracking (HIC) cracks that are stacked perpendicularly in the direction of through-wall cracks and driven by high residual or applied stresses. Because this damage can easily lead to mechanical integrity failures, facility owners should take measures to prevent or mitigate SOHIC when possible.

Areas Susceptible to SOHIC

Pressure equipment operating in environments with above 50 ppm of H2S content, at or below 180ºF temperature in aqueous sour water is more susceptible to wet H2S cracking, incuding SOHIC. Cyanides in overhead systems of cat crackers and cokers can also significantly increase susceptibility.

SOHIC Prevention/Mitigation

All systems susceptible to SOHIC should be inspected and maintained according to the latest edition of NACE RP0296. Susceptible quipment should also be post weld heat treated (PWHT) or alloyed up when possible. HIC resistant steels and polymeric coatings have been successfully applied to reduce the risk of SOHIC, as well as stainless steel clad materials in more aggressive environments.

References

  1. Prueter, P., 2021, “Damage Control: Wet H2S Damage Detection,” Inspectioneering Journal, 27(5), pp. 45-52.

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Articles about Stress-Oriented Hydrogen Induced Cracking (SOHIC)
January/February 2022 Inspectioneering Journal

Within one unit, TriLat combines the power of two probes containing three angle beam sets to identify and quantify cracking at early stages. The result is inspection speeds up to ten times faster than traditional AUT systems, depending on probe size.

January/February 2022 Inspectioneering Journal

This edition of Damage Control will offer practical steps to mitigate different forms of wet H2S damage and help to minimize long-term inspection and maintenance costs related to wet H2S damage.

November/December 2021 Inspectioneering Journal

This issue of Damage Control offers a perspective on how to assess the different forms of wet H2S damage using modern FFS and computational analysis techniques with the safe operation of damaged pressure vessels, piping, and associated components.

September/October 2021 Inspectioneering Journal

This article summarizes the fundamentals of wet H2S-related damage mechanisms, offers some practical inspection guidance, and reviews a notable industry failure caused by different forms of wet H2S damage.

November/December 2003 Inspectioneering Journal

There are a variety of forms of wet H2S cracking. In this short article I will focus on two of the most common forms: hydrogen induced cracking and stress-oriented hydrogen induced cracking (HIC/ SOHIC). HIC is often fairly innocuous (but not...

Authors: John Reynolds
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May/June 1995 Inspectioneering Journal

Exposure of carbon steel equipment to wet H2S service environments can lead to various forms of attack, e.g. hydrogen blistering and hydrogen induced cracking (HIC), stress oriented hydrogen induced cracking (SOHIC) and sulfide stress cracking...

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