Selection of materials for sulfur-containing light hydrocarbon pipelines

When selecting materials for pipelines transporting sulfur-containing light hydrocarbons, factors such as the corrosiveness of the medium, operating pressure, operating temperature, and safety requirements must be considered primarily. Sulfides are corrosive agents that can attack many commonly used pipe materials; especially in the presence of water or moisture, sulfides accelerate the corrosion process. Therefore, for sulfur-containing light hydrocarbons, materials with good corrosion resistance should be selected. According to the “Code for Fire Protection Design of Petrochemical Enterprises” (SH 3059), the term “high-quality steel” generally refers to steels that possess better mechanical properties and corrosion resistance compared to ordinary carbon steel. This may include types such as low-alloy steels and stainless steels. The specific type of high-quality steel to be used should be determined based on the particular medium, operating conditions, safety requirements, and design standards. For light hydrocarbon media containing 200 PPM of sulfur, the following commonly used corrosion-resistant materials can be considered: 1. Stainless steel: Stainless steel grades such as 304, 304L, 316, and 316L exhibit good corrosion resistance and are widely used in light hydrocarbons and other petrochemical media. 2. Alloy steels: such as 9Cr-1Mo (P91), Cr-Mo-V, etc., which exhibit better resistance to high temperatures, high pressures, and corrosion. 3. Duplex stainless steels: Duplex stainless steels (such as 2205, 2507, etc.) exhibit good mechanical properties and corrosion resistance, making them suitable for use in relatively harsh service environments. When selecting pipe materials, it is necessary to evaluate the possible types of corrosion (such as sulfide stress corrosion cracking [SSCC], chloride stress corrosion cracking [CLSCC], and ordinary sulfate-reducing bacteria corrosion [SRB]) based on the specific composition of the light hydrocarbons and operating conditions. This evaluation should be carried out in conjunction with considerations of cost-effectiveness and safety risks. Regarding the method of piping connection, flanges conforming to the HG20592 standard can be used to connect pipes. However, it is essential to ensure that the material and pressure rating of the flanges meet the corrosion resistance requirements as well as the pressure and temperature conditions associated with sulfur-containing light hydrocarbon media. When designing and selecting materials, it is possible to refer to the recommendations of SH standards, while also taking into account the specific requirements of HG standards, in order to ensure the overall compatibility and safety of the system. It is recommended to consult with professional materials engineers or relevant experts before deciding on the final material; they can provide more specialized advice tailored to the specific application conditions. At the same time, it is also necessary to consider whether corrosion tests on different materials are required, or to consult experienced material suppliers to confirm that the selected materials can meet long-term usage requirements. .