Propeller Polishing at Sèmè Terminal
Mirror finish, measurably lower fuel burn
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Tell us the vessel, the port and the window. Scoped reply, usually the same working day.
Cleanship Marine carries out underwater propeller super polishing at Sèmè Terminal, Ouémé. Divers work the blades through a multi-stage sequence to a Class A mirror finish, removing fouling, calcareous deposits and accumulated surface roughness while the vessel lies at the anchorage.
The propeller is the highest-leverage surface on any vessel calling at Sèmè: it runs at high relative velocity, so roughness there costs disproportionately more than the same roughness spread over the hull. For the crude oil tankers, mooring and terminal support vessels, offshore supply and crew boats working this port, polishing is the shortest route to a measurable fuel saving.
The voyage out of Sèmè is the one that matters for propeller condition: a fully laden crude tanker on a long passage to her discharge port, where every point of propeller efficiency is paid for in fuel for weeks. Polishing in the waiting area before she loads puts the smoothest possible blade on for exactly that leg. The window is set by the loading schedule rather than by a berth, so we plan against the terminal's nomination and the swell forecast together, and polish the moment both line up.
What it gets you
- Blade roughness removed where it costs the most, at the highest-velocity surface on the vessel
- Propeller efficiency restored between dockings without off-hire
- Cavitation erosion and edge damage documented before it becomes a repair item
- A finish record that supports hull and propeller performance monitoring
Working conditions at Sèmè
Sèmè has no harbour at all. Tankers load offshore at a single point mooring, so every vessel here lies in open Gulf of Guinea water with nothing between her and the long-period Atlantic swell that runs onto this coast. That swell, not visibility, decides whether a dive goes ahead. The water itself is warm and — away from the lagoon outflows further west at Cotonou — clearer than the harbour ports, which helps inspection work on the days the sea allows it. No work is ever done at the buoy or while a tanker is connected.
- Where we work
- Tanker waiting area off the terminal · Sea area outside the SPM safety zone
- Vessels we see here
- Crude oil tankers · Mooring and terminal support vessels · Offshore supply and crew boats
What we do at Sèmè
- Blade condition assessment covering both faces, the leading and trailing edges and the tips
- Multi-stage polishing sequence worked down to a Class A mirror finish
- Boss, hub and fairing cone cleaned, with rope guard and seal area inspected
- Edge damage, cavitation erosion and any deformation photographed and reported rather than polished over
- Diving permission cleared with WAPCO, the terminal operator, and the shaft confirmed immobilised with the master before the dive
- Before-and-after video and a written finish record for the performance file
Planning the window at Sèmè
The combination of Atlantic swell and rain governs the calendar at Sèmè Terminal, with the heaviest rain from May to October and swell running year-round. The swell here is long-period Atlantic ground swell rather than wind-driven sea, so it reaches the anchorages on days that look calm from the bridge and it is the single biggest cause of a lost in-water window on this coast. The buoy itself is off limits, so hull work is done with the tanker in the waiting area off the terminal, before she is called to the SPM or after she is released; the dive plan is built around the loading schedule and the swell.
Work is taken at the tanker waiting area off the terminal and sea area outside the SPM safety zone, and which of those a vessel ends up at changes the dive plan more than the season does. Teams mobilise via Cotonou (COO), so give us the ETA as early as you have it — the travel is the flexible part, the approvals and the working window are not.
What we typically find at Sèmè
Liquid and gas tonnage here spends long stretches at the terminal or waiting for a slot, so growth tends to be even and well established across the hull rather than patchy — heavier than the trading pattern suggests, and further along than a speed report alone would indicate.
Tankers coming to Sèmè have usually crossed from their last discharge in ballast and may then wait offshore for their loading slot, and it is that waiting in warm Gulf of Guinea water that adds growth fastest. A clean done before loading removes it before the laden voyage, where it would cost the most.
Standard scope of work
Included as standard on every propeller polishing attendance, wherever the vessel is. Anything outside it is quoted separately and flagged before mobilisation, never added afterwards.
- Deposit removal
- Calcareous growth, shell and hard deposits removed from both blade faces without gouging or scoring the blade surface.
- Progressive polishing
- Successive abrasive grades work the blade from rough to fine, finishing at a Class A mirror surface across the full blade area.
- Edge finishing
- Leading and trailing edges dressed to restore profile and remove the roughness that seeds cavitation.
- Boss and hub
- Boss, hub and rope guard cleaned, with stern tube seal condition inspected and reported.
How we deliver it at Sèmè
- 1
Scope and vessel details
Tell us the vessel, her particulars, the coating specification and the window at Sèmè. We come back with a defined scope, a crew size and a duration we will stand behind. Where the conditions here will not support what has been asked for, we say so at this stage rather than after mobilisation.
- 2
Permits and approvals
Access at Sèmè Terminal is the terminal operator's decision as much as WAPCO, the terminal operator's, so both are in the approval chain from the start — a berth-side refusal discovered at the gangway costs the whole attendance. Diving permission, terminal approval and any environmental clearance for in-water work are handled by us, not left with the agent to chase.
- 3
Mobilisation to Sèmè
Divers, compressors, brush carts and cameras mobilise via Cotonou (COO). Where a vessel is also calling at Cotonou, one mobilisation is normally sized to cover both.
- 4
Safety setup and the dive
The vessel is secured for diving — main engine, shaft and thrusters immobilised, sea suctions confirmed shut, permit agreed with the master. Teams work under surface supervision with continuous diver communications and video throughout.
- 5
Report and handover
A completion report covering propeller polishing is issued with before-and-after imagery, coating and anode condition and anything found that you should know about. The findings are discussed with the vessel rather than emailed and forgotten.
Sèmè Terminal at a glance
- UN/LOCODE
- BJSEM
- Port type
- Private Port
- State
- Ouémé
- Country
- Benin
- Water body
- Bight of Benin, Gulf of Guinea
- Port authority
- WAPCO, the terminal operator
- Main cargoes
- Crude oil
- Crew mobilisation
- Cotonou (COO)
- Services here
- Hull Cleaning
Frequently asked — Propeller Polishing at Sèmè
Do you provide propeller polishing at Sèmè Terminal?
Yes. Cleanship Marine works Sèmè Terminal (BJSEM) in Ouémé, Benin, covering the tanker waiting area off the terminal and sea area outside the SPM safety zone. Teams mobilise via Cotonou (COO) with the full spread.
When should the propeller be polished on a tanker loading at Sèmè?
Before loading, while she waits to be called to the buoy — so the freshly polished propeller is working for the whole laden voyage out, which is where it saves the most fuel. We plan it against the loading nomination and the swell forecast, and it is never done while the vessel is connected.
Can propeller polishing be done while the vessel works cargo at Sèmè?
No — nothing is done while a tanker is connected to the buoy and loading. Hull work is done in the waiting area off the terminal before she is called in, or after she is released, which at Sèmè is usually time she is spending waiting anyway. The vessel stays on hire throughout, and there is no diversion and no dry dock. We scope against the conditions at Sèmè and tell you honestly whether the window you have is enough.
Do you need a diving permit from WAPCO, the terminal operator?
Yes, and we obtain it. Diving permission from WAPCO, the terminal operator, terminal approval where the berth requires it, and any environmental clearance for in-water work are arranged as part of the job rather than left with the agent. The master's permit to work and the immobilisation of machinery are agreed on board before anyone enters the water.
What is underwater visibility like at Sèmè?
Visibility at Sèmè Terminal is good for this coast — open sea water, away from the lagoon outflows at Cotonou — so the limit here is the swell rather than what a diver can see, and the combination of Atlantic swell and rain sets the outer limits of the calendar. How the tide and sea state shape the dive plan is set out in full in the working-conditions section on this page.
Which vessels do you carry out propeller polishing on at Sèmè?
Crude oil tankers, Mooring and terminal support vessels, Offshore supply and crew boats — the traffic at Sèmè Terminal runs to crude oil, so those are the profiles we see most. The scope is sized to the vessel, not to a standard package.
How quickly can a team mobilise to Sèmè?
Divers and equipment mobilise via Cotonou (COO). Give us the ETA and the window and we will confirm what is achievable rather than promise a date we cannot hold. Where the vessel also calls at Cotonou or Lomé, one mobilisation is often sized to cover both.
What does propeller polishing at Sèmè cost?
It depends on the vessel's dimensions and wetted area, the fouling state found, the coating specification and the working window available at Sèmè. We would rather scope it properly and give you a specific figure than quote a headline rate that changes once the work starts. Send the details and the window at Sèmè and you get a scoped price, usually the same working day.
Propeller Polishing at Sèmè Terminal.
Tell us the vessel, her ETA at Sèmè and the window. You get a scope, a crew size and an honest duration — usually the same working day.