What Is Floating Roof Tank Inspection?
A floating roof storage tank has no fixed roof over the product. Instead, a buoyant steel roof floats directly on the surface of the stored liquid and rises and falls with the level, so the vapour space above the product is kept to a minimum. That design is used across refineries, terminals and tank farms precisely because it cuts evaporative and emission losses on volatile stocks such as crude, gasoline and naphtha. Floating roof tank inspection is the systematic assessment of that moving roof and the components that keep it afloat, sealed and drained.
The inspection concentrates on the parts that are unique to a floating roof: the pontoons — the sealed buoyancy compartments around the perimeter (or across the whole deck on a double-deck roof) that provide flotation; the roof deck itself; the primary and secondary rim seals that close the gap between the roof and the shell; the roof drains that carry rainwater off the deck; and the roof-support legs and rolling ladder that let the roof land safely and give access when the tank is low. This work sits within the broader tank inspection discipline but demands its own focus because none of these features exists on a fixed-roof tank.
Both external floating roof (EFR) and internal floating roof (IFR) tanks fall under this scope. On an EFR the deck is open to the weather; on an IFR a lightweight cover floats inside a fixed-roof tank. Either way, the condition of the pontoons, deck and seals governs whether the roof floats level, keeps vapour in, and sheds rain — and those are the questions a floating roof inspection has to answer.
Why Floating Roofs Are a Distinct Inspection Risk
What sets a floating roof apart is that the traditional way to inspect it — walking on the deck — is one of the more hazardous tasks in a tank farm. The roof sits low in the shell, directly on a large volume of flammable product, so an inspector on the deck is standing above the stored liquid, close to rim-seal vapour, on a surface that is uneven, sometimes coated in product, and often carrying standing rainwater. A pontoon that has quietly corroded can be weaker than it looks underfoot. The confined space between the roof and the shell adds a vapour and access hazard on top of the work-at-height exposure.
The failure modes are serious in their own right. Rim-seal gaps and deteriorated primary or secondary seals let product vapour escape continuously — a direct source of VOC loss, wasted product and a flammable-vapour hazard at the rim that also carries an ignition and fire history across the industry. Pontoon corrosion or a punctured compartment can flood with product or water and sink one side of the roof, tilting the deck and jamming it against the shell. Drainage failure — blocked or cracked roof drains, or a stuck drain valve — lets rainwater pond on the deck, adding load the roof was never meant to carry and, in the worst case, overwhelming its buoyancy. Each of these develops slowly and out of sight, which is exactly why regular condition monitoring matters.
How Drone Floating Roof Inspection Works
A drone surveys the entire floating roof from above, so the condition data is gathered without a single person walking the deck. The aircraft flies a planned grid across the roof at a controlled standoff, imaging every pontoon top, the full deck surface, the rim-seal ring, the drain sumps and the support legs at a consistent resolution. What would take a manned team hours of hazardous deck time — if the roof is even safe to walk — is captured in a fraction of the time and with no work-at-height or confined-space exposure.
Two capabilities run together. High-resolution visual imaging resolves the detail that governs roof condition: corrosion and pitting on pontoon plates, coating breakdown, deck buckling and weld condition, tears and hardening in the primary and secondary seals, visible rim-seal gaps against the shell, and standing water or product pooling on the deck or in the drain sumps. Radiometric thermal imaging adds a second layer — it can reveal vapour escaping through a seal gap, liquid product sitting on the deck, and cool patches that betray liquid inside a pontoon compartment that should be dry.
The advantages over manned roof access are decisive:
- No one on the roof — the deck is never loaded by inspectors, removing the work-at-height, confined-space and flammable-vapour exposure of walking a floating roof.
- Complete coverage — every pontoon, the full deck and the entire rim-seal ring are imaged, not just the areas an inspector can safely reach on foot.
- Hidden-condition detection — thermal imaging flags seal-gap vapour and liquid inside pontoons that a visual-only walk would miss.
- Traceable evidence — every finding is imaged and located, giving your inspector and API 653 authorised inspector a precise, auditable record.
After capture, the imagery is compiled into a roof-condition package: pontoon-by-pontoon condition, deck and weld findings, a rim-seal gap map, drain and leg condition, all annotated and located so your engineering and inspection team can act on it and plan the next out-of-service scope.
What We Inspect on a Floating Roof
Our survey is structured around the components that determine whether a floating roof stays afloat, sealed and drained.
Pontoons & Buoyancy
Top plates and pontoon-to-deck welds imaged for corrosion, pitting, coating breakdown and ponded water. Thermal checks flag liquid inside a compartment that should be dry — an early sign of lost buoyancy.
Roof Deck
The full deck surface assessed for corrosion, buckling, weld condition, product pooling and standing rainwater that adds unplanned load to the roof.
Primary & Secondary Rim Seals
The seal ring surveyed for tears, hardening, missing sections and gaps against the shell — the findings that drive vapour loss, emissions and rim fire risk.
Roof Drains & Legs
Drain sumps, drain hoses and support legs checked for blockage, standing water, corrosion and damage, plus the rolling ladder condition where visible.
Where the Survey Fits in Your Tank Programme
A drone floating roof survey works at two points in the tank lifecycle. As an external in-service survey, it images the roof from the top of the shell or from above while the tank stays live — an ideal screening and condition-monitoring tool that extends the interval between costly shutdowns and catches deterioration early. During an out-of-service inspection, when the tank is emptied and gas-freed, the same drone can survey the roof internally in far greater detail, feeding directly into the statutory examination.
The floating roof survey is one part of a complete tank picture. It complements shell UT thickness measurement on the tank wall and floor MFL scanning on the tank bottom, so that roof, shell and floor condition are assessed together. Because rim-seal condition drives fugitive vapour loss, the seal-gap findings also tie directly into any LDAR and fugitive-emission survey on the facility. Across a refinery or terminal, this work forms part of our wider oil & gas drone inspection and industrial inspection capability.
We carry out this work against the recognised tank standards. API 653 governs the inspection, repair, alteration and reconstruction of aboveground storage tanks and sets the framework for out-of-service and in-service examination. API 575 covers the inspection practices for atmospheric and low-pressure storage tanks, including floating-roof components. The seal and vapour-loss context draws on the industry practice captured in API 2517 and API 2519 for external and internal floating-roof seal evaluation. Our drone data is built to support the assessment your API 653 authorised inspector or engineering team is responsible for.
Why Choose SG Drone Inspections
We are a specialist industrial drone inspection provider in Singapore, focused on gathering complete, well-located tank condition data that your inspection and engineering teams can act on.
CAAS-Permitted Operations
Our drone operations run under the required CAAS operator and activity permits, and we handle the airspace and site coordination for flights over live tank farms and process areas.
Visual + Thermal in One Flight
High-resolution visual capture and radiometric thermal imaging on the same sortie, so pontoon corrosion, deck condition, seal gaps and vapour loss are read together.
Standards-Aligned Data
Survey planning and reporting are built around API 653 and API 575 so the roof-condition package slots straight into your tank inspection programme.
We Work With Your Inspector
We deliver defect-mapped roof data in the format your API 653 authorised inspector and engineering team need to make the assessment and plan the next shutdown scope.
Frequently Asked Questions
Get a Floating Roof Tank Inspection Quote
Send us your tank details — diameter, roof type and whether it is in or out of service — and we will reply with a survey scope within 24 hours, no obligation.