Thruster Cleaning & Polishing at Sèmè Terminal
Full thrust restored when you need it most
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Tell us the vessel, the port and the window. Scoped reply, usually the same working day.
Cleanship Marine cleans and polishes bow and stern thrusters at Sèmè Terminal, Ouémé. Divers clear the full tunnel bore, polish the blades and hub, and clear the gratings, restoring the manoeuvring thrust that quietly disappears while a vessel sits idle.
Thruster tunnels are the worst fouling trap on a hull — sheltered, still and almost never inspected. Growth builds on the tunnel walls, blades and gratings without anyone noticing until manoeuvring performance drops, and at Sèmè — the offshore crude buoy at the end of the Niger–Benin pipeline — that tends to show at exactly the moment the thrust is needed.
Many large crude tankers that load at Sèmè are not fitted with a bow thruster at all — they are brought onto the buoy with the help of the terminal's support craft. So thruster cleaning here is mostly for the vessels that keep the terminal running: the mooring and support boats that work the buoy day after day, and the smaller tankers that do carry a thruster. The support craft in particular sit in warm water between jobs and depend on their thrusters for close-quarters work at the buoy, which is where a fouled tunnel shows first.
What it gets you
- Manoeuvring thrust restored ahead of a berthing or a pilotage that needs it
- Tunnel and grating flow cleared, not just the visible blade faces
- Seal, boss and anode condition documented while the divers are already down
- Reduced reliance on tug assistance where thrust had quietly degraded
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
- Full tunnel bore cleaned end to end, both openings, including the areas behind the gratings
- Blade and hub polished, with seal and boss condition inspected and reported
- Tunnel gratings cleared of growth and debris so flow is restored, not just the visible face
- Anodes inside the tunnel checked and wastage recorded
- Diving permission cleared with WAPCO, the terminal operator, with the thruster confirmed isolated and tagged out before the dive
- Video record of tunnel and blade condition before and after
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 thruster cleaning attendance, wherever the vessel is. Anything outside it is quoted separately and flagged before mobilisation, never added afterwards.
- Tunnel cleaning
- Fouling removed from the full length of the tunnel bore, including the areas behind gratings where growth is heaviest.
- Blade cleaning and polishing
- Propeller blades and hub cleaned and polished to restore surface finish and reduce cavitation-inducing roughness.
- Grating and guard clearance
- Gratings and rope guards cleared of growth, netting and debris that restrict flow or risk fouling the unit.
- Condition inspection
- Blade edges, seals and visible gearcase condition inspected and recorded, with any damage reported immediately.
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 thruster cleaning 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 — Thruster Cleaning at Sèmè
Do you provide thruster cleaning 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.
Do tankers loading at Sèmè need thruster cleaning?
Only if they are fitted with one, and many large crude tankers are not — they are assisted onto the buoy by the terminal's support vessels. Thruster cleaning at Sèmè is mainly for those support and mooring craft, and for the smaller tankers that do have a thruster.
Can thruster cleaning 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 thruster cleaning 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 thruster cleaning 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.
Thruster Cleaning & 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.