How to Retrofit Tower Internals When Field Welding Is Prohibited
Tower-internals replacement becomes more difficult when welding to the vessel shell is prohibited.
Restrictions may exist because of pressure-vessel integrity, rubber or FRP lining, combustible residues, hot-work controls, limited shutdown time or the risk of damaging corrosion-resistant cladding.
The replacement design must therefore create a verified load path without assuming new shell welds.
Why Field Welding May Be Restricted
Common reasons include:
- Rubber-lined or coated tower shell
- FRP vessel construction
- Glass-lined equipment
- Corrosion-resistant cladding
- Hazardous process residue
- Hot-work permit limitations
- Vessel code restrictions
- Short turnaround schedule
- Inaccessible weld locations
- Risk of shell distortion
Grinding or drilling may also be prohibited, even if no welding is planned.
Start With Existing Attachment Points
The field survey should identify:
- Existing support rings
- Shell clips
- Beam pockets
- Bolted connections
- Nozzle flanges
- Manway frames
- Original hanger points
- Remaining thickness and corrosion condition
An existing ring should not be reused solely because it is present. Its dimensions, condition and allowable load must be verified.
Possible Non-Welded Arrangements
Depending on the vessel and load, the design may use:
- Internals resting on an existing support ring
- Segmented beams supported by existing clips
- Bolted panel assemblies
- Split support rings
- Adjustable jacking or clamping systems
- Hangers from approved existing attachments
- Self-supporting cartridge assemblies
These are design directions, not universal solutions. Their structural capacity and effect on the vessel must be confirmed for the project.
Load Path Must Be Clear
The load path should be identifiable:
Packing or liquid load → Internal panels → Beams → Existing attachment → Vessel shell
A clamp or jacking screw is not acceptable merely because it fits. It must resist the defined:
- Vertical load
- Horizontal movement
- Uplift
- Vibration
- Thermal movement
- Upset condition
Protect the Existing Lining
For lined towers, confirm:
- Lining material and thickness
- Permitted contact pressure
- Need for protective pads
- Chemical compatibility
- Risk of cutting or abrasion
- Existing lining damage
- Repair procedure
Metal edges and concentrated jacking forces can damage a lining even without welding.
Segmentation and Installation
A non-welded internal may require more components and connections.
Confirm:
- Manway clear opening
- Maximum segment size
- Segment weight
- Assembly sequence
- Bolt accessibility
- Tool clearance
- Orientation marks
- Prevention of loose parts
- Future removal method
Required Project Information
Provide:
- Tower construction material
- Lining or cladding details
- Original vessel drawing
- Existing attachment drawings
- Field measurements
- Internal photographs
- Design loads
- Operating temperature
- Corrosion environment
- Prohibited site activities
- Available installation time