Service équivalent carbone et acide
Tours de transmission d'énergie à haute résistance et résistantes au vent – Recherche et développement
janvier 31, 2026Service équivalent carbone et acide
3. Chemical Integrity: Service équivalent carbone et acide
For subsea pipelines, weldability is paramount. To ensure the heat-affected zone (Haz) does not become brittle, la Équivalent carbone (CE) is strictly limited.
We typically use the IIW Formula:
$$CE_{IIW} = C + \frac{Mn}{6} + \frac{Cr + Mo + V}{5} + \frac{Ni + Cu}{15}$$
For X65QO, $CE_{IIW}$ is usually kept below 0.39, ensuring that offshore welding can be performed with minimal preheating, speeding up the pipe-lay process.
En plus, because many offshore reservoirs contain $H_2S$, these pipes are often tested for HIC (Hydrogen Induced Cracking) et SSCC (Sulfide Stress Corrosion Cracking). This requires extremely low sulfur levels ($\leq 0.002\%$) and calcium treatment for inclusion shape control (converting elongated sulfides into spherical shapes).
