Preventing corrosion-induced deterioration in distillation columns is key to helping refineries remain productive and competitive. One of the world's top integrated energy companies recently experienced corrosion issues on several units at its refinery complex in Spain. Sulzer's automated weld overlay capabilities provided an economical and efficient solution to debottleneck the different columns and extend their service lives.
When the crude processing refinery, one of the largest in Spain, noticed extensive corrosion within the column shells of three main separation towers, it sought to resolve the problem. In particular, the column showing higher levels of corrosion was the vacuum distillation unit (VDU).
The structure of the VDU consisted of one wash bed and three pump-around circuits. The tower's shell was made of carbon steel coupled with a 3-millimeter bonded plate to prevent corrosion. Over time, the plate started to corrode and lost its ability to protect the underlying column shell. Based on the plate's visible damage, the surface area of the damage was estimated to be 65 m2.
The refinery turned to Sulzer, whose Tower Field Services group has supported it in the past with routine maintenance and field services. Sulzer performed an in-depth visual inspection by removing the bonded plate to expose the carbon steel shell. This examination revealed the extent of column shell corrosion was almost double that of the initial estimate, covering approximately 110 m2.
Sulzer offered a long-lasting solution: weld overlay. This in situ process makes it possible to cover large column surfaces with corrosion-resistant alloys. Sulzer is highly experienced in this technique and has developed state-of-the-art, fully automated weld overlay equipment to support its operations.
Its automated process can quickly perform welding with high accuracy. In this case, Sulzer could complete the overlay of the 110-m2 corroded surface in the time allocated to 65 m2. The VDU column shell was overlaid with layers of austenitic stainless steel type 316 alloy to avoid carbide precipitation. In addition, the presence of molybdenum and nickel makes the alloy suitable for applications in harsh conditions.
Sulzer also performed weld overlay on the corroded surfaces of the other two towers. Column internals, such as trays and packings, were replaced to further improve the performance of the entire oil distillation system.
Sulzer performed the weld overlay process in two weeks, while the entire revamp was concluded in 25 days without any delays. Since the revamp, the refinery has operated smoothly at full capacity, and Sulzer's solution could support its shift toward different crudes without affecting the columns' corrosion resistance. The customer was so pleased with the team's work, it has offered to provide a positive reference to any potential customers of Sulzer.
Andrew Petticrew, business development manager at Sulzer Tower Field Services, commented, "The ability of Sulzer's experts to resolve unexpected issues, coupled with our automated weld overlay capabilities, was crucial to ensure the timely repair of the corroded column shells. In addition, the customer benefitted from a one-stop-shop for the revamp project."
For more information, visit www.sulzer.com or call (281) 540-2555.
