Q1: What materials resist hydrogen embrittlement at elevated temperatures?
A1: Low-alloy steels like 1.25Cr-0.5Mo perform well above 200°C where hydrogen diffusion slows. Austenitic stainless steels (304H, 316H) maintain ductility across temperature ranges. These materials are selected based on Nelson curve compatibility. Special heat treatments optimize microstructure for hydrogen service.
Q2: How are hydroprocessing reactor effluent pipes designed?
A2: They incorporate corrosion allowances for high-sulfur streams. Thermal sleeves protect at temperature transition zones. These designs handle 400-450°C service with hydrogen partial pressures exceeding 100 bar.
Q3: What welding techniques prevent hydrogen cracking in hot pipes?
A3: Low-hydrogen welding processes with strict preheat requirements. Post-weld heat treatment relieves residual stresses. These controls prevent delayed hydrogen-assisted cracking.
Q4: Why are hot hydrogen pipes susceptible to decarburization?
A4: Hydrogen reacts with carbon in steel at temperatures above 200°C. This surface degradation reduces strength. Higher chromium content (5-9%) significantly slows the reaction rate.
Q5: How are hydrogen reformer transfer lines inspected?
A5: High-temperature UT crawlers monitor thickness loss. Replication metallurgy checks microstructural changes. These specialized methods assess damage without cooling the system.
