RE: [MW:15166] Regarding HIC TEST requrement FOR WET SOUR SERVICE

Dear,

 

REQUIRED

 

because,

 

Sulfide stress cracking (SSC) is a form of cracking that involves hydrogen embrittlement of the metal by atomic hydrogen that is produced by the corrosion reaction of wet H2S with the metal. SSC is typically intergranular with little branching, and some times may contain some transgranular portions. SSC is more likely to occur in high strength (high- hardness) materials or in hard weld deposits or hard heat- affected zones (HAZs) of welds in lower- strength material.

 

SSC is very much dependant on the degree of hydrogen charging in the material, which is primarily associated with the process environmental parameters like pH and sulfide content of the water. The lowest hydrogen flux in steels typically results from corrosion in near natural pH solutions (pH 5.5-7.5). The hydrogen flux resulting from wet sulfide corrosion increases both as the pH increases and as the pH decreases from this near neutral range. Corrosion at the lower (more acidic) pH values is caused by higher concentrations of dissolved H2S in the water whereas corrosion at the higher (more alkaline) pH values is caused by higher concentrations of the bisulfide ion in the water

The sulfide content of the water is generally related to the H2S partial pressure in the gas phase associated with the water. In acidic sulfide environments, SSC is likely to occur when the H2S partial pressure exceeds 0.0003 MPa absolute or 3 mbara (0.05 psia). This corresponds to approximately 1-3 ppm of H2S dissolved in the water. The likelihood of SSC increases with increasing sulfide application in the water. At sulfide to concentrations greater than 1,000 ppm the likelihood of SSC is considered to be high. Presence of significant levels of cyanides (>20ppm) in the water at pH values above 7.5 increases the hydrogen charging of the steel and can produce a high likelihood of SSC at lower sulfide concentrations
 

SSC is related to two materials parameters- hardness and tensile stress level. The hardness of the base metal is its strength level. Materials with a high hardness are more susceptible to SSC is generally considered a concern for materials with a tensile strength that exceeds 620 MPa (90 ksi). Therefore, SSC is highly likely to occur in the low- alloy steel and other more highly alloyed materials whose tensile strengths exceed this level. SSC of the typical carbon steel base metals used for pressure vessels and piping in wet H2S service in oilfield, gas and refining facilities is not a concern because of their low hardness levels. However, weld deposits and heat affected zones (HAZs) in welded carbon steel may contain local areas of high hardness due to the presence of non- tempered martensite and high residual stresses associated with the welding that could increase susceptibility to SSC.

 

Wet H2S system, low sulphur steel is to be used with qualified HIC resistant properties (CSR, CLR, CTR). During fabrication, recommended weld hardness with PWHT shall be maintained for SSC resistant steel. Wet H2S system is to be periodically re-inspected even if made of HIC resistant steel because these steel may not be total resistant in actual refinery operation. For any major operational changes, total system shall be critically reviewed with respected to Carbonate cracking also.

Thank & Best Regards,

 

M Veera SAMY- Bureau Veritas.

Coimbatore

 

 

 

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Date: Thu, 30 Aug 2012 10:58:38 +0530
Subject: [MW:15162] Regarding HIC TEST requrement FOR WET SOUR SERVICE
From: ahmedmech77@gmail.com
To: pgoswami@quickclic.net
CC: pgoswami@sympatico.ca; materials-welding@googlegroups.com

Dear Sir,

 

I need your Help regarding HIC Test required or Not

 

Ques: Shell & tube heat exchanger , KJO PROJECT,Saudi ARAMCO, IN Datasheet Notes points menstion as

 

1)all materials in wet,sour service shall be resistant to SSC & HIC and shall meet the requirment of MRO175/ISO15156

2)CORROSION /EROSION is due to H2S & CO2 Content are 0.115 mole% & 0.024 respectively

 

 

 

our service is Sour service , hot oil at shell side & wet crude tube side our material is SA516gr70

 

pls refer aramco spec rgarding wet sour , CAN U ELABORATE ME REGARDING HIC TEST REQ OR NOT

 

 

Aramco Spec 32-SAMSS-007

 

Wet Sour HIC Services: Hydrogen Induced Cracking (HIC) resistant steel qualified in

accordance with 01-SAMSS-016 shall be specified for the following environments with

normal operating temperatures between 0°C (32°F) and 150°C (302°F):

Sour water service with a hydrogen sulfide (H2S) concentration above

2 mg/L (2 ppm) and a total pressure of 450 KPa absolute (65 psia) or greater.

Hydrocarbon services meeting the definition of sour environments in SAES-A-301,

where the H2S concentration of 2 mg/L (2 ppm) or more in the water phase is equivalent

to H2S partial pressure of 0.05 psia.

A hydrocarbon system exposed to an environment with a H2S concentration above

50 mg/L (50 ppm) in the water phase, regardless of H2S partial pressure.

Commentary Note:

HIC resistant steel is not required in caustic services, lean amine systems and rich amine

DGA systems.

 

regards,

 

Shaikh Ahmed

Inspection

08082560014

 

 

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