Inside the Asset
Illustrative inspection scene. The numbered anatomy reference below locates common components and inspection zones; actual equipment configurations vary.
What it is
A tall vertical vessel that separates a mixture through repeated vapor–liquid contact. Crude towers, fractionators, strippers, splitters and debutanizers perform related separations, with the configuration determined by the feed and desired products.
This guide covers tray and packed columns, with the numbered illustration serving as a location reference. Pressure containment and separation performance are different inspection questions: a tower may have intact walls and still suffer significant internal damage.
How it works
Feed and heat input. Feed enters at a selected elevation. Many columns use a reboiler and overhead condenser, while crude towers commonly receive heat through a fired feed heater. The process arrangement determines which connected equipment belongs in the scope.
Vapor–liquid contact. Rising vapor and descending liquid exchange components. More volatile components concentrate toward the top, while less volatile components collect lower down; product draws depend on the service.
Trays, weirs and downcomers. Tray openings permit vapor flow, weirs establish liquid behavior, and downcomers route liquid to the level below. The components work together, so a damaged section can affect performance beyond its own tray.
Packing and distributors. Structured or random packing provides contact area. Liquid distribution, packing supports and hold-down arrangements are as important to the inspection route as the packing itself. [1, 2]
Shell, nozzles and access. The pressure shell encloses the internals. Manways give access to particular elevations, but trays or packing can prevent a remote tool from reaching the next compartment.
Original tower component and inspection-zone illustration. Use actual tray numbers, elevations and manway locations; the drawing does not imply that every internal space is connected or remotely accessible.
Where it fails
Trays and supports. Corrosion, pressure upsets or fouling can bend or dislodge trays and damage their supports. Map observations by tray number and elevation to make repair planning practical.
Overhead system. Condensation and service chemistry can create localized corrosion in susceptible overhead sections. The tower top, reflux connections and connected equipment may need coordinated examination.
Feed and reflux zones. Impingement and localized attack may concentrate around inlet regions. Broad shell readings alone can miss the area most affected by the flow.
Hot lower sections. In susceptible refinery service, sulfidation or naphthenic acid corrosion depends on chemistry, metallurgy and operating conditions. Do not assume every distillation tower shares the same damage mechanisms.
Packing, weirs and downcomers. Fouling, coking or mechanical damage can impair separation without causing an external leak. Process history and internal observations help distinguish performance issues from pressure-boundary damage.
How it gets inspected
Plan the tower by elevation and compartment. Shell condition and internal performance require different evidence. List each tray space or packed section, the intended access opening and the actual coverage achieved. Carry blocked spaces forward as coverage gaps, not as inspected areas.
API 510 may provide the in-service framework for an applicable tower pressure boundary. Internal condition and process performance also require the owner’s equipment knowledge and inspection criteria. [3]
Equipment for the job
Select the method for the suspected damage, material, geometry and access, then choose a suitable instrument and configuration. These equipment examples support different parts of the job; no single tool establishes the condition of the entire asset.
Tray and packing internals. Flyability Elios 3 can inspect spaces reachable from suitable manways; trays and packing may block passage and require separate access. Elios 3 UT Payload provides accessible spot readings; assess Power Tether Unit routing and snag risk. Evident IPLEX GT supports close views of downcomers and draw-off sumps.
Overhead section and shell thickness. Olympus 38DL Plus / Cygnus 1 Ex at CMLs; Olympus HydroFORM corrosion mapping on the top courses; MFE HPX Wall Crawler for external thickness at elevation
Nozzle and seam welds. OmniScan X4 with appropriate probes and scanners; COBRA is an option only where its pipe-diameter and access envelope fit the connection.
CUI on the insulated shell. MFE PulsePro / Eddyfi Lyft on compatible walls and insulation systems; FLIR T640 for thermal anomalies that guide follow-up. Confirm suspect areas with an appropriate direct examination.
Externals, platforms and jacketing. DJI Matrice 350 RTK with a compatible Zenmuse H30-series payload, or Skydio X10; maintain separation from structures and operating equipment.
Materials. XRF / PMI analyzers to verify alloy upgrades in the overhead and bottoms sections
Field note. Build a coverage record by elevation and compartment. If a drone or camera cannot pass a tray or reach a packed section, that space remains unexamined until another access method provides the required evidence.
Why it matters
Damaged internals can reduce separation performance without an external leak. Planning access by compartment helps teams find damage and scope repairs during the turnaround.
Ask your inspection provider
Which tray spaces are actually reachable, and how will blocked compartments and missed coverage be documented?
Field card - record on every route
Identify. Tower ID, service, tray/packing drawing, elevation references and access openings.
Record. Compartment-by-compartment coverage, image references and shell reading locations.
Confirm. Connect suspected tray, packing or shell damage to a targeted follow-up examination.
Flag gaps. Blocked tray spaces, hidden supports, packed sections and tether or opening constraints.
Close the loop. Repair scope by elevation, follow-up owner and evidence that each coverage gap was addressed.
Support for the inspection
Review drawings and previous turnaround findings before selecting remote-access equipment. Agree the inspection sequence by manway and elevation, the plan for blocked compartments and how internal findings will be handed to the repair team.
Training, Repairs & Calibrations and Proof of Concept support are available through MFE Inspection Solutions.
Sources and equipment references
2. Sulzer - Packing configurations
3. API - Pressure vessel inspection framework
4. Eddyfi - Pulsed eddy current and probe footprint
5. Flyability - Elios 3 remote inspection platform
This educational guide does not replace an asset-specific inspection procedure. The author is an executive at MFE Inspection Solutions. Equipment and service links lead to MFE; cited manufacturer information supports method selection. Confirm instrument suitability and availability for the planned scope.