How to prevent SCCC in LPG storage tanks
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Considering the background regarding sulfide stress corrosion cracking (SSCC) in liquefied petroleum gas storage tanks at refineries mentioned earlier, targeted preventive measures can be implemented from multiple perspectives: First, select materials appropriately by giving priority to low-carbon steel; the lower the carbon content in the steel, the less sensitive it is to sulfide stress corrosion cracking. Avoid using high-strength, high-hardness steels in order to reduce the risk of cracking at the material level. II. Elimination of residual stresses: Through processes such as post-weld heat treatment and aging treatment, the residual tensile stresses in the weld areas of storage tanks as well as in the areas that have undergone cold working are reduced. The hardness of these weld areas is kept below the safety threshold for SSCC, thereby preventing stress concentration. III. Improve the medium environment by carrying out advanced desulfurization of liquefied petroleum gas, strictly control the hydrogen sulfide content in the medium, reduce the corrosivity of wet hydrogen sulfide environments, and thereby minimize the factors that lead to cracking at the source. IV. Protection and operation control: An anti-corrosion coating is applied to the inner wall of the storage tank, and a combined cathodic protection system consisting of a coating on the bottom plate inside the tank along with high-efficiency aluminum sacrificial anodes is used to isolate corrosive agents from the steel substrate. Formulate a regular inspection plan for fixed-point thickness measurement and non-destructive testing, with a focus on checking for cracks in welds and areas prone to stress concentration; comprehensive inspections of storage tanks should be carried out every 3–6 years.
I’ve read the original poster’s share; it’s very comprehensive! Proper material selection and the elimination of residual stresses are indeed key to preventing SCC. I would like to add a detail that is often overlooked in practice: in addition to material and stress factors, controlling the medium environment is also important. For example, it is essential to strictly regulate the hydrogen sulfide concentration and moisture content in liquefied petroleum gas in order to prevent localized acidification. Additionally, online monitoring devices can be installed to regularly check for changes in the hardness of the tank walls, allowing for prompt action in case any abnormalities are detected. Of course, these measures need to be determined in accordance with specific operating conditions and standard specifications; it is recommended to engage a qualified professional agency to conduct a risk assessment to ensure everything is covered.