What is hydrogen induced stress cracking?
Overview of Hydrogen Stress Cracking Hydrogen Stress Cracking is a form of Hydrogen Embrittlement that occurs when corrosion from acids like wet hydrogen sulfide and hydrofluoric acid cause atomic hydrogen to penetrate hardened or higher strength steels and cause stress cracking.
How do you prevent sulfide stress cracking?
Sulphide stress cracking is prevented by minimising the hardness and strength of the alloys used for wet H2S systems.
What is sulfide stress cracking test?
Element performs Sulfide Stress Cracking (SSC) testing of metals subject to cracking under the combined action of tensile stress and corrosion in the presence of water and H2S, in compliance with NACE TM0177/ ISO 15156 standards.
What causes hydrogen cracking?
Cracking usually occurs at temperatures at or near normal ambient. It is caused by the diffusion of hydrogen to the highly stressed, hardened part of the weldment.
Why HIC testing is required?
HIC testing is recommended to evaluate the resistance of pipeline and pressure vessel plate steels to hydrogen induced cracking corrosion caused by hydrogen absorption from aqueous sulfide corrosion. Unstressed test specimens are exposed to a solution at temperature of 25deg cent with continuous H2S gas flow.
How can avoid SSC?
Sulfide Stress Cracking can be prevented through:
- Control of stress level (residual or load) and hardness.
- Apply post-weld heat treatment (PWHT). Computer software ACE – Apps for Corrosion Engineers has a module to determine when PWHT or Pre-Heating is required.
- Avoid the hydrogen source.
What causes stress corrosion cracking?
Tensile Stress This involves a material experiencing stress or strain from either residual stress or the direct application of stress or pressure. In the case of stress corrosion cracking, crack propagation is caused by mostly static stress.
What is SSC testing?
SSC (Sulfide Stress Cracking Test) Test standards describe many different procedures to simulate and evaluate the reaction of the material to the double effect of mechanical strenght and corrosion attack. Various H2S solutions and chloride content solutions may be used to simulate sour environments.
What is HIC resistant material?
HIC Resistant Steel is carbon steel which is tested to demonstrate the plate’s resilience to the long term effects of hydrogen induced cracking, tested according to NACE.
When does hydrogen induced cracking occur?
2 Hydrogen induced cracking (HIC) HIC occurs in carbon or low-alloy steels when atomic hydrogen diffuses into it and forms molecular hydrogen. Formation of molecular hydrogen may be facilitated by inclusions or trap sites. Therefore HIC can occur in the absence of any stress.
What is SSC in welding?
Sulfide stress cracking (SSC) is the failure of steel caused by the simultaneous action of stress and hydrogen absorbed from corrosion by aqueous hydrogen sulfide. Because welding can induce high hardness and residual stresses, weldments often are particularly susceptible to SSC.
What kind of cracking is caused by hydrogen sulfide?
The catastrophic cracking of steels in hydrogen sulfide (H 2 S) environments referred to as sulfide stress cracking is a special case of hydrogen stress cracking. The microstructure at the HIC fracture of a mild carbon steel. The white hairlines in the photo are the HIC fracture zone.
What kind of steel does hydrogen induced cracking fail?
These metals includes carbon steel, alloy steel, and nickel & nickel alloy, etc. The hydrogen-induced cracking failure of an API 5L X60 line pipe. For many steels, a threshold stress exists below which hydrogen induced cracking does not occur.
Is there a threshold for hydrogen induced cracking?
For many steels, a threshold stress exists below which hydrogen induced cracking does not occur. This threshold is a function of the strength level of the steel and the specific hydrogen-bearing environment. Therefore, threshold stress or stress intensity for HIC is not considered a material property.
What are the risks of sulfide stress cracking?
Uncontrollable downhole failures due to sulfide stress cracking (SSC) of higher strength carbon steel and alloy steel tubing and equipment are a major safety risk in well streams producing more than 0.3 kPa (0.05 psi) partial pressure H 2 S. SSC failures often occur rapidly with little prior warning.
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