Pressure vessels operating under high-temperature and high-pressure conditions are widely used in industries such as chemical, petroleum, energy, and metallurgy. These vessels must withstand not only the thermal stresses of high temperatures but also the mechanical stresses of high pressures. Therefore, strict design and material selection principles must be adhered to to ensure operational safety and longevity.

First, the operating parameters must be fully considered during the design phase. The design pressure and temperature of high-temperature and high-pressure vessels are often higher than the actual operating parameters to ensure a safety margin. Design calculations should be conducted in accordance with standards to ensure sufficient strength and stability under the most severe operating conditions. Furthermore, stress concentration areas should be minimized, and reinforcement ribs, transition fillets, and support structures should be appropriately designed to reduce the risk of fatigue failure.

Second, the material selection must meet the high-temperature and high-pressure performance requirements. Commonly used materials include heat-resistant alloy steels (such as Cr-Mo steel), stainless steels (such as 316H and 321), and nickel-based alloys, which exhibit high creep strength and oxidation resistance at high temperatures. Materials must be selected based on the properties of the medium. For example, for acidic media, alloys with stronger corrosion resistance should be selected, while for hydrogen environments, resistance to hydrogen embrittlement should be considered. Furthermore, raw materials with authoritative certifications should be prioritized to ensure that their chemical composition and mechanical properties meet standards.

Third, welding processes and heat treatment must be strictly controlled. The weld joints of high-temperature and high-pressure vessels are the weakest link. Low-hydrogen welding consumables and multi-layer, multi-pass welding techniques should be used, and non-destructive testing (RT, UT, PT, etc.) should be performed to ensure weld quality. For thick-walled structures, post-weld heat treatment (PWHT) should be performed to eliminate residual stress and improve metallographic stability.

Furthermore, protection and monitoring are equally critical. Wear-resistant and corrosion-resistant linings or coatings can be added to the design to extend service life. During operation, pressure, temperature, and stress monitoring devices should be installed to promptly detect anomalies and prevent accidents.

The design and material selection of pressure vessels for high-temperature and high-pressure applications is a systematic project that requires comprehensive consideration of factors such as mechanical strength, temperature resistance, corrosion resistance, and manufacturing processes to ensure safe and stable operation in harsh environments.