How to Control Temporary Scaffolding Loads on Tower Internals During Turnarounds

Tower internals are designed for specific process, maintenance, and upset loads. They are not automatically qualified to support scaffold legs, suspended platforms, stacked materials, hydroblasting equipment, or groups of workers during a turnaround. A tray that safely carries distributed liquid load can be permanently distorted by a concentrated scaffold reaction applied between support beams.

Temporary works inside a tower should therefore have an engineered load path. Before entry, the owner, scaffold contractor, internal specialist, and inspection team must agree where loads may be applied, how they reach the vessel structure, and how the internals will be protected and checked afterward.

Why Temporary Loads Are Different

Process loads are often distributed over a deck, grid, or support ring. Scaffold standards transfer load through a few small base plates. Toolboxes, hoses, pumps, removed packing, and replacement panels add concentrated or uneven loads. Dynamic effects arise when workers climb, equipment starts, a hose whips, or material is lowered onto a platform.

A scaffold may also introduce horizontal force. Bracing against panels, downcomers, distributors, or the shell can impose unconsidered loads. Hanging scaffolds place tension and local bending on members intended mainly for downward load.

The risk increases when internals are corroded, cracked, incompletely assembled, or partly removed. A beam that shared load through several panels in operation may behave differently after one section is opened for access. Deposits can hide damage and make a weak deck appear continuous.

Establish an Allowable-Load Map

Start with current drawings, support reactions, materials, thicknesses, span directions, and inspection condition. Identify shell support rings, primary beams, secondary beams, tray decks, collector plates, distributor troughs, packing grids, downcomers, and nonstructural accessories.

Create a plan showing approved bearing points, prohibited zones, maximum reactions, required spreader beams, and any limitations on concurrent loads. The map should distinguish primary structural members from panels that only close hydraulic gaps. Color markings may help in the field, but they must correspond to an approved drawing.

If existing calculations do not cover temporary loads, evaluate the actual scaffold reactions. Include personnel, platforms, stored materials, equipment, hoses containing water, impact allowance, and rescue loading. Consider load combinations during erection and dismantling, when the scaffold may be least braced.

Do not credit a corroded support ring or beam without current condition data. If capacity is uncertain, use a temporary load path attached to verified vessel features or an independently supported system rather than placing unquantified load on the internal.

Use Load-Spreading Details Correctly

A timber board under a scaffold leg spreads load only if it is sufficiently stiff, spans appropriate supports, and remains stable. A flexible plank resting on a thin tray deck may still concentrate most of the reaction near the leg. Spreader beams or grillages should be designed to deliver load to verified structural members.

Protective pads should be compatible with the internal material and service cleanliness. Carbon-steel scaffold parts can contaminate stainless surfaces; timber may retain chemicals, shed debris, or introduce treatment compounds. Rubber pads may leave residues or create unstable bearing.

Secure temporary members without welding, drilling, or cutting unless an approved engineering procedure permits it. Clamps can crush thin flanges or damage coatings. Tying scaffold to distributor laterals, downpipes, demister frames, or valve hardware is unacceptable unless those parts were specifically assessed.

Maintain drainage and emergency access. Temporary platforms should not trap cleaning water or block ventilation, gas testing, ladders, manways, and rescue routes. The scaffold arrangement must remain safe as internals are removed and the load path changes.

Control Loads During Maintenance Work

The scaffold calculation is only part of the problem. Define where removed tray panels, valves, packing, deposits, and replacement parts may be stored. A small pile of wet packing can exceed the intended distributed load. Debris bags placed at one edge can overload a clip or cantilevered panel.

Hydroblasting introduces hose weight, nozzle reaction, vibration, and water accumulation. Vacuum hoses can pull laterally or collapse thin components if they seal against a surface. Lifting devices attached to scaffold members add forces that may not appear in the original scaffold design.

Use a lift and material-handling plan that identifies maximum piece weight, routes, temporary laydown areas, and attachment points. Maintain housekeeping so loose bolts, abrasive, and broken packing do not accumulate on decks or fall to lower internals.

Any field change to scaffold position, height, bracing, or loading should be reviewed by the responsible temporary-works authority. Workers should not move a standard from an approved beam to a convenient tray panel without reassessment.

Failure Consequences

Temporary overloading may cause immediate collapse, but permanent deformation is more common. A tray deck can dish, opening panel joints and changing liquid depth. A distributor can lose levelness and later produce maldistribution. A packing support can deflect, allowing bed settlement or local crushing.

Clips and bolt holes may yield without obvious fracture. Ceramic grids can develop hidden cracks that fail after restart. Coatings and linings can be crushed beneath base plates, creating corrosion sites. Damage to one internal may remain unnoticed until the tower experiences pressure differential or liquid load in service.

Personnel risk is direct: failure of an internal supporting scaffold can produce a fall through multiple tower levels. Temporary-work control is therefore both a process-reliability and confined-space safety requirement.

Inspection and Release Checkpoints

Before erection, inspect approved bearing points and record existing distortion, corrosion, cracks, and coating condition. Verify scaffold component cleanliness, base dimensions, spreaders, and load tags. The installed scaffold should be checked against the approved arrangement before work begins.

During the turnaround, inspect after major load changes, internal removal, impact events, or reports of movement. Stop work if panels dish, fasteners loosen, supports move, or unusual noise occurs.

After scaffold removal, inspect contact points, adjacent welds, panels, clips, holes, coatings, and internal levelness. Remove all temporary materials and debris. Where a liquid distributor or tray was loaded, dimensional survey or water testing may be justified before closure.

The final release record should identify temporary-load locations, observed damage, repairs, examinations, and acceptance. A scaffold tag proves the scaffold was suitable; it does not by itself prove that the tower internals supporting it were suitable.