Offshore submerged seawater intakes with velocity-cap headworks, risers and tunnelled pipelines for the largest desalination, cooling and industrial duties.
Engineering Excellence for Marine Environments
Open-ocean intakes draw seawater offshore, below the wave-action and high-turbidity zone, through a submerged intake head connected to shore by a buried pipeline or tunnel. They suit the highest-capacity duties — SWRO desalination trains, once-through cooling and large industrial supply — where subsurface intakes cannot deliver the flow.
Headworks, conveyance and protection
Horizontal-flow cap converts vertical rise to low horizontal velocity (<0.15 m/s) that fish detect and avoid.
Vertical riser from the seabed pipeline to the intake head, with debris cage and marine-grade screens.
Bored tunnel and seabed riser for surf-exposed coasts — no trenching, minimal seabed disturbance.
Multiple offshore inlets share the duty, balancing velocity and giving redundancy during maintenance.
Cylindrical screens with airburst cleaning for fine, low-velocity, fish-friendly screening at the head.
Forebay / pump sump with coarse and fine screening before the transfer pumps.
Typical engineering envelope
| Parameter | Typical Value | Notes |
|---|---|---|
| Through-cap velocity | 0.10 – 0.15 m/s | Fish-protective; sets cap area |
| Pipeline velocity | 1.5 – 2.5 m/s | Self-scouring, acceptable head loss |
| Head depth | 5 – 30 m | Below wave base & turbidity zone |
| Minimum submergence | >2 × pipe dia. | Prevents air entrainment / vortexing |
| Pipeline material | GRP, HDPE or concrete | Ballasted / buried for stability |
| Screen material | 90/10 Cu-Ni, super duplex | Antifouling & corrosion resistance |
| Storm design | 100-year wave & current | DNV / EN 1993 structural basis |
Continue across the seawater intake engineering series
Beach wells and infiltration galleries for naturally filtered, low-SDI feed.
Read MoreChlorination, antifouling alloys and UV to keep intakes clear.
Read MoreSuper duplex, Cu-Ni, titanium and cathodic protection for marine service.
Read MoreMulti-stage screening for debris, seaweed and jellyfish.
Read More316(b) fish protection, velocity caps and low-entrainment design.
Read MoreThe full seawater intake hub — challenges, configurations and specifications.
Read MoreIntake design integrated with SWRO pre-treatment trains.
Read MoreOur raw-water intake engineering service across all source types.
Read MoreBar, band and drum screens for intake debris removal.
Read MoreComplete SWRO desalination plant solutions.
Read MoreTalk to our marine engineering team about open ocean intakes and a complete, compliant intake package — survivable, low-fouling and built for decades of service.
Our expertise spans multiple industries with sector-specific water treatment solutions.
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