Engineering Coke Drum Structural Stability

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360° Skirt Replacement Under Sustained Load

When full circumferential cracking develops at a coke drum skirt-to-shell junction, the issue is no longer localized fatigue repair, but a structural stability challenge. 

A major Central European refinery identified advanced cracking and skirt dislocation on two coke drums. Inspection confirmed that less than 50% of the original support structure remained structurally effective. 

The skirt is the primary load path transferring the drum’s operating weight, thermal expansion forces, and dynamic loads into the foundation system. Compromise at this junction directly affects structural integrity. 

A full 360° skirt replacement was required, under sustained load conditions, within a defined 60-day turnaround. 

 

Why Skirt Integrity Matters

Coke drums operate in a severe cyclic thermal environment. Daily heating to elevated temperatures followed by rapid quenching generates expansion and contraction forces that concentrate stress at restrained junctions, particularly the skirt-to-shell weld. 

Over time, fatigue cracking at this interface can: 

  • Propagate circumferentially 
  • Cause progressive separation between skirt and shell 
  • Redistribute stresses unpredictably 
  • Compromise vertical load transfer 

When cracking reaches full circumferential extent, the repair strategy shifts from crack mitigation to structural reconstruction. 

In this case, restoration required the complete removal and rebuild of the skirt assembly while maintaining drum stability throughout. 

Scope of Work

  • Full skirt replacement on two coke drums 
  • Complete 360° weld joint rebuild 
  • Structural stabilization during removal 
  • Automated Gas Tungsten Arc Welding (GTAW) for rebuild 
  • 60-day turnaround execution 
  • 80+ personnel mobilized 

The work involved temporary load management, controlled disassembly of a compromised support structure, and precision reconstruction under strict metallurgical controls. 

 

“Automation helps clients meet very tight schedules,” Antoni explains. “With proper planning, productivity and inspection results become much more predictable.”

And in turnaround environments, predictability equals schedule and cost control.

Engineering Approach

  • Temporary Structural Support Design

Before removal of the damaged skirt sections, a dedicated temporary support system was engineered to prevent shell deformation and foundation overload. 

This step was critical. Removing a primary support element without controlled load redistribution can introduce distortion, misalignment, or secondary cracking. 

Load path stability was verified before any cutting began. 

  • Controlled Removal and Sequencing

The existing skirt was removed in carefully defined segments to maintain circumferential balance. 

Sequencing was engineered to: 

  1. Prevent uneven load redistribution 
  2. Avoid shell ovalization 
  3. Minimize residual stress concentration 
  4. Maintain dimensional control 

Structural rebuilds of this nature are as much about order of operations as they are about welding procedure. 

  • Automated GTAW for Metallurgical Consistency

Rebuilding a full 360° skirt weld demands consistency in: 

  1. Heat input 
  2. Penetration profile 
  3. Metallurgical properties 
  4. Residual stress management 

GTAW was selected to ensure uniform deposition and repeatable weld quality across the entire circumference. 

In heavy-wall structural applications, automation improves: 

  1. Weld profile consistency 
  2. Mechanical property uniformity 
  3. Inspection predictability 
  4. Reduced variability across shifts 

For fatigue-sensitive junctions such as skirt welds, consistency is fundamental to long-term performance. 

  • Reinforcement and Structural Rebuild Strategy

Prior to full reconstruction, reinforcement measures were implemented to stabilize transitional load paths. 

The rebuild restored: 

  1. Full circumferential structural continuity 
  2. Defined load transfer geometry 
  3. Controlled weld toe transitions 
  4. Improved fatigue performance characteristics 

The objective was to restore structural integrity in a way that supports continued cyclic service. 

 

Execution Governance 

  • 80+ personnel coordinated under a unified engineering framework 
  • Structural assessment integrated throughout execution 
  • Welding engineering oversight during critical phases 
  • QA/QC sequencing aligned with reconstruction milestones 

Work of this nature demands tight coordination between structural engineering, welding execution, inspection teams, and project controls. The risk profile is inherently high when primary load-bearing elements are removed and rebuilt under schedule constraint. 

A Global Project in One of the World’s Largest LNG Facilities

Currently, Antoni’s team is completing a major weld overlay project for one of the world’s largest LNG producers.

The scope includes overlay application on more than 150 pipe ends.

The environment itself presents challenges:

  • Dust and wind
  • High humidity
  • Construction sequencing managed by a general contractor
“Environmental conditions in the Middle East can significantly affect welding,” Antoni explains. “Our crew had to use their experience to mitigate these factors and ensure flawless quality.”

Daily coordination with the general contractor, forward planning, and continuous communication with the asset owner have kept the project on track.

From Antoni’s perspective, the deployment is a success:

  • No quality issues
  • Strong crew morale
  • Effective coordination
  • Transparent progress reporting

Building Automated Field Welding at IGS

What excites Antoni most about building this capability at IGS is the combination of deep technical experience with global reach.

IGS teams include professionals from the U.S., Poland, the Czech Republic, South Africa, and beyond, coming together to execute projects worldwide. “IGS is known for fast response times and global presence,” Antoni says. “Pairing that with specialized welding expertise allows us to deliver more value, especially in urgent or unexpected situations.”

The LNG project also demonstrated the power of hybrid solutions, combining weld overlay with other IGS technologies such as High Velocity Thermal Spray (HVTS).

This integration is where Antoni sees the future: “Combining automated welding services with other IGS solutions allows us to design smarter, more efficient protection strategies for our clients.”

 

 

Experience Over Theory

Perhaps the most important takeaway from Antoni’s perspective is this:

IGS is not building its automated field welding capability from theory but from real project experience. Lessons learned in oil & gas, petrochemical, and power environments directly inform planning, safety integration, and execution workflows.

And in high-risk, high-pressure turnaround environments, experience is what separates smooth execution from costly disruption.

View Antoni’s profile

 

 

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