Carbon Steel

Stress Orientated Hydrogen Induced Cracking (SOHIC) is a potential problem found in steel pressure vessels, boilers and pipes deployed in sour service, primarily within the oil and gas industry.  So what exactly is SOHIC, what damage can it cause and what measures can be taken to avoid it happening in the first place?

SOHIC Explained

Stress orientated hydrogen induced cracking occurs in sour service installations.  Sour service is a working environment where there are significant levels of hydrogen sulphide present, and such environments are common in the oil and gas industry.  Steel boilers and pressure vessels used in sour service can corrode from the inside due to the build up of hydrogen sulphide.  Similar to hydrogen induced cracking (HIC), stress orientated hydrogen induced cracking is different due to the fact that it effects the heat affected zone (HAZ) of welds since this is the weak point in the pressure vessel or pipe.  Failure to detect corrosion in this area could cause the pipe of pressure vessel to fail with potentially dangerous consequences.

It is therefore important that the steel procured has been tested for susceptibility to the effects of hydrogen sulphide corrosion in some way.  Whilst a specific SOHIC susceptibility test has not been standardised within the industry as of yet, HIC testing is available for particular steel grades used in this instance.

The testing procedure essentially involves the evaluation of resistance of pressure vessel, boiler and  pipework steels to hydrogen induced cracking caused by hydrogen absorption from aqueous sulfide corrosion. An unstressed steel sample is exposed to a solution at ambient temperature and pressure. After a designated period, the sample is removed and assessed. The results of this test determines the materials suitability for the purpose intended.  This will provide the customer with confidence as to how long the material is likely to last before replacement is required.

Steel grades of this type can be tested by the mill, by a UKAS approved testing agency or a specific test criteria can be provided by the customer.

To obtain further information reqarding stress orientated hydrogen induced cracking (SOHIC) or to receive a competitive quotation for HIC tested steel, contact Masteel UK limited by clicking here.

Cleaning a Carbon Steel Sword

[affmage source="ebay" results="10"]Carbon Steel[/affmage]