Session: DA-15-02 Coke Drum Materials Considerations

Paper Number: 152632

152632 - Evaluation of Low Cycle Fatigue (Lcf) in Pre-Welded Nickel Alloy 625 to Carbon-Molybdenum Alloy Steel Explosion Clad Plates Detaclad for Coke Drum Applications 

Abstract: 

Coke drums are critical components in the delayed coking process, which converts heavy residual oils into lighter hydrocarbons through thermal cracking. These drums undergo extreme thermal cycling, alternating between high-temperature coking and rapid quenching phases. This cycling subjects the materials to significant cyclic thermal stresses, leading to Low Cycle Fatigue (LCF) behavior, which can result in cracking and structural failure, particularly in vulnerable areas.

Welds in coke drums are especially prone to LCF-induced damage due to residual stresses from welding, differences in mechanical properties between the weld metal and base material, and potential welding defects such as inclusions or porosity. These factors create stress concentrators, particularly around circumferential seam welds, support skirts, and nozzle connections, with the highest multi-axial stresses.

Among cladding technologies used to apply corrosion-resistant metallic layers onto steel bases, the explosion welding process, particularly DetaClad™, is regarded as a reliable and cost-efficient solution. The DetaClad process produces the largest-sized cladder plates available on the market, bringing significant value for coke drum applications. One of its key benefits is the reduction in the number of circumferential welds, which not only lowers CAPEX by simplifying installation but also reduces the risk of fatigue-induced cracks, leading to OPEX savings through decreased maintenance and extended operational life.

In some instances, to produce these larger cladder plates, smaller corrosion resistance alloy (CRA) plates must first be pre-welded before undergoing the explosion cladding process to a larger steel base plate. While this method offers operational benefits, it raises concerns about the LCF resistance of the pre-welded joints. Customers are particularly cautious about whether these pre-welded sections can endure the same stresses as fully non-prewelded clad materials, especially given the extreme thermal cycling in coke drum operations. Rigorous testing is required to validate the fatigue resistance of pre-welded cladder plates and address these concerns.

This paper presents findings from an LCF testing program on pre-welded Nickel Alloy 625 CRA (Ni-625) EXW to Carbon-Molybdenum alloy steel cladded plates. Test specimens, prepared using NobelClad’s proprietary explosion welding procedures, were subjected to cyclic thermal loading at elevated temperatures to simulate real-world service conditions. The results demonstrate that Ni-625 cladder pre-welds exhibit superior fatigue resistance, with failures occurring consistently in the steel base metal rather than at the cladder interface or weld seams. These findings offer reassurance that pre-welded Ni-625 clad plates can withstand severe operating conditions, addressing customer concerns and providing significant advantages in both CAPEX and OPEX.

Presenting Author: olivier sarrat NobelClad

Presenting Author Biography: Olivier Sarrat, with a 28-year tenure at NobelClad, is the Business Development Manager specializing in the oil and gas sector. He holds an MS in Mechanical Engineering and another in Strategy & Management of International Business. His extensive expertise is deeply rooted in explosion welding manufacture and control. Sarrat's technical proficiency includes overseeing complex contract and operations management within NobelClad. He is actively engaged in addressing technical challenges and advancements in explosion welding, particularly in applications related to oil and gas, alternative energies, and carbon capture. His deep knowledge and hands-on experience make him a valuable resource for insights into the latest trends and solutions in metal cladding for the energy industry.

Authors:

olivier sarrat NobelClad
Chris E. Wilson Nobelclad
Tim Delahanty NobelClad