However good a floating raft looks, it depends on what you can't see — the pontoons under the water. When a pontoon leaks, corrodes or a weld cracks, the cost is more than a repair bill.
!The raft lists or sinks and has to close
!The whole raft must be lifted out — costing many times the price of the pontoons
!Safety risks to people and property
9 steps from fabrication to installation
Steps 1–6 fabricate and test the pontoons; steps 7–9 cover pre-assembly, transport and on-site installation.
1
Step 1
Rolling the steel shell
What we do
Steel plate is rolled into cylinders in three standard diameters — Ø510 / Ø770 / Ø950 mm — and fitted with end caps.
Why it matters
Roundness and plate thickness determine buoyancy and resistance to water pressure. Off-centre forming builds up stress at the welds — the starting point of future leaks.
Inspection criteria
✓Steel at least 3 mm thick per the Marine Department standard (Ø510 uses 4 mm)
✓Actual plate thickness measured for every lot before production
✓Roundness and alignment checked before welding
Videos from the factory
Steel plate passing through the rolling machine to form a cylinder · 23 secLifting a rolled steel cylinder with a hoist · 9 sec
26 real photos
2
Step 2
Double welding to AWS standard
What we do
Pontoons are welded in two layers — outside and inside — to American Welding Society (AWS) standards.
Why it matters
Single outside-only welds are the most common weak point: once cracked by impact or corrosion, water gets in. Double welding creates two barriers and adds strength.
Inspection criteria
✓Continuous full welds with no gaps or skips
✓Weld quality controlled to AWS standard
✓Every seam welded inside and outside
Videos from the factory
Grinding a circumferential weld on the pontoon · 14 secWelding team working a seam on a hoisted pontoon · 10 sec
10 real photos
3
Step 3
Weld inspection by PT-Test
What we do
Welds are inspected by penetrant testing: a liquid seeps into defects and is drawn out to show clearly on the surface.
Why it matters
Tiny cracks, pores and leaks are invisible to the eye but grow under load and corrosion. PT-Test catches them in the factory, before the pontoon goes into the water.
Inspection criteria
✓Welds tested at points set in the inspection plan
✓No surface-breaking cracks, pores or leaks
✓Any defect is ground out, re-welded and re-tested until it passes
Videos from the factory
Spraying penetrant on a weld (PT-Test) · 14 secChecking the penetrant result on a weld · 8 sec
9 real photos
4
Step 4
2-bar air leak test on every pontoon
What we do
Sealed pontoons are pressurised to 2 bar, checked for leaks along every seam, and monitored for stable pressure over a set time.
Why it matters
This is the final proof that the whole pontoon is watertight, so no water will collect inside and make the raft sink or list later.
Inspection criteria
✓Every pontoon tested — not sampled
✓Test pressure 2 bar
✓Pressure must hold with no leak bubbles anywhere
✓Any leak goes back for repair and a full re-test
Videos from the factory
Spraying soapy water on the welds under air pressure to find leaks · 22 secPressure gauge fitted to the pontoon during the test · 17 sec
5
Step 5
Sandblasting surface preparation
What we do
Abrasive is blasted over the entire steel surface to remove rust, oil and dirt before coating.
Why it matters
Removes rust everywhere — including corners and welds — and roughens the surface (anchor profile) so coatings bond firmly, extending pontoon life and cutting maintenance.
Inspection criteria
✓Surface clean and free of rust and contaminants
✓Surface profile suitable for primer adhesion
✓Coated within the set time after blasting to prevent flash rust
Videos from the factory
Sandblasting the pontoon surface before coating · 8 secSandblasting along the full length of the pontoon · 24 sec
4 real photos
6
Step 6
Coal tar epoxy coating ≥ 450 µm
What we do
Pontoons are coated in marine-grade coal tar epoxy, built up in layers to a dry film thickness of at least 450 microns.
Why it matters
Coal tar epoxy forms a dense, water- and corrosion-resistant film. Thickness is the key — thin films degrade quickly and let water reach the steel.
Inspection criteria
✓Dry film thickness measured with a digital coating thickness gauge
✓Dry film thickness at least 450 microns
✓Several points measured per pontoon, including welds and end-cap edges
✓Any reading below spec is recoated and re-measured
4 real photos
6.1
Optional extra
Option: hot-dip galvanizing
What we do
For projects needing extra-long service life, pontoons can be hot-dip galvanized, with zinc coating covering both the outside and inside.
Why it matters
An option on top of the standard coating system, suited to projects that want minimal long-term maintenance. We advise based on the water conditions and budget.
Inspection criteria
✓Galvanized coating checked for full coverage before delivery
✓Ask our team for details
8 real photos
7
Step 7
Pre-assembly layout at the factory
What we do
Pontoons are laid out to the actual raft plan in the factory, brackets are fitted, and every position is checked before dispatch.
Why it matters
Problems are solved in the factory, reducing rework on site and making installation faster and true to the design.
Inspection criteria
✓Pontoon positions and spacing match the raft plan
✓All mounting brackets fitted
✓Team inspection before release for delivery
Videos from the factory
Team fitting pontoon brackets to the layout · 13 secAerial: pontoons laid out to the raft plan in the factory · 26 sec
16 real photos
8
Step 8
Transport
What we do
Pontoons are crane-loaded, stacked and strapped securely, then delivered to site.
Why it matters
Inspected pontoons must arrive in perfect condition — no dents or coating damage.
Inspection criteria
✓Pontoons and brackets checked before loading
✓Pontoons stacked and strapped securely
Videos from the factory
Hoisting a pontoon in preparation for transport · 18 secWorker guiding a hoisted pontoon · 4 sec
20 real photos
9
Step 9
On-site installation
What we do
Our team assembles the raft, lowers it into the water by crane, and completes the installation on site.
Why it matters
We handle everything from fabrication to finished installation — one responsible party for the whole project.
Inspection criteria
✓Team in safety gear with a briefing before lifting work
At least 3 mm per Marine Department standard (Ø510: 4 mm)
Available lengths
Ø510: 1.80–12.00 m · Ø770: 2.40–12.00 m · Ø950: 3.00–12.00 m (standard length table)
Shape
Rolled cylinder with end caps
Welding
Double — inside and outside — to AWS standard
Weld inspection
PT-Test (penetrant testing)
Leak test
2-bar air pressure, every pontoon
Surface preparation
Full sandblasting
Coating
Marine coal tar epoxy, dry film ≥ 450 µm
Option
Hot-dip galvanizing
Quality control (QC) checklist
#
Check
Method
Pass criteria
Scope
1
Steel thickness
Thickness gauge
≥ 3 mm
Every material lot
2
Weld quality
Visual inspection to AWS
Full double welds, inside & out
Every pontoon
3
Weld defects
PT-Test
No cracks / pores / leaks
Per inspection plan
4
Leakage
Air leak test
2 bar holds, no leaks
Every pontoon
5
Surface cleanliness
Visual check after blasting
No rust / old paint / dirt
Every pontoon
6
Coating thickness
Coating thickness gauge
≥ 450 µm
Several points per pontoon
Documents delivered with the work
✓PT-Test report
✓Air leak test certificate
✓Coating thickness record
✓Photo record of the manufacturing steps
We can prepare procurement documents, technical specifications (TOR/Spec) and standard certificates as required by government agencies.
Frequently asked questions
Is 3 mm steel thick enough?+
Yes — the Marine Department standard requires at least 3 mm for floating pontoons. Long-term durability also depends on weld quality and corrosion protection, which is why we double-weld and coat to 450 microns. (Ø510 pontoons use 4 mm steel.)
How is PT-Test different from visual inspection?+
Visual checks only find large defects. PT-Test uses a liquid that seeps into tiny surface-breaking cracks and pores, then draws them out as clear marks — revealing defects invisible to the eye.
Why test every pontoon at 2 bar?+
A single leaking pontoon can make a whole raft list or settle, so sampling isn't enough. We test every pontoon before delivery.
Is sandblasting really needed? Can't we just paint over?+
Not recommended. Paint over rust or dirt won't bond and soon peels, while rust spreads unseen underneath. Sandblasting is what determines a pontoon's real service life.
What's the difference between 450 and 300 microns of coating?+
Film thickness is the armour that keeps water and moisture away from the steel. Thicker films resist abrasion and corrosion and age more slowly. The common benchmark for this work is 300 microns; ours is at least 450.
Do you provide inspection documents?+
Yes. We deliver the PT-Test report, air leak test certificate and coating thickness record, with a photo record of the manufacturing steps.
Can I get pontoon lengths outside the standard table?+
Tick "Special pontoon length" in the quote request form and our team will review it and get back to you.
Let us size the pontoons for your project
Start with the preliminary calculator and send us the results. Our engineers will size the pontoons and prepare a quotation with full manufacturing standard details.
