SEAWATER INTAKE AND DEEP SEA DISCHARGE SYSTEMS

Professional solutions for seawater intake and deep sea discharge systems, one of the most challenging areas of engineering
SEAWATER INTAKE AND DEEP SEA DISCHARGE SYSTEMS
Seawater intake and deep sea discharge systems are one of the most challenging areas of engineering. In these systems, both nature and technology must work in perfect balance. As PİLSAN, we design, manufacture and install seawater intake lines, cooling water transmission systems and deep sea discharge lines tens of kilometers long on a turnkey basis.
We carefully plan each project from geotechnical analysis to hydraulic design, from pipe selection and manufacturing to underwater installation, and thanks to our expertise in HDPE lines, we establish systems that are fully compatible with nature and long-lasting in these challenging conditions that require high strength and flexibility.

WATER INTAKE STRUCTURES

The success of seawater intake systems begins at the first point of contact: the intake structure. These structures determine the quality, flow rate and lifespan of the water drawn from the sea. Depending on project requirements, we design fixed reinforced concrete tower-type structures, submersible intake systems with HDPE body or floating platform systems.
The basic principle in every design is laminar flow, minimum turbulence and prevention of marine life entry. Intake velocity is usually limited to 0.15–0.3 m/s range. This both prevents harm to marine life and prevents sediment intake at the inlet.

  • Stainless steel or GRP screens, copper alloy antifouling cages and automatic backwash systems can be used in the system

  • Current direction, bottom profile and sediment movement in the area where water is drawn are examined; accordingly, intake mouth height and hydraulic balance plates are determined

  • All this data is verified with fluid dynamics analyses and the final design is optimized specifically for field conditions

TRANSMISSION LINES (MARINE PIPELINES)

In these lines, material selection is not only a technical but also an environmental and economic decision. The most suitable material for marine environment is HDPE. The flexibility, chemical resistance and weld integrity of high-density polyethylene provide significant advantages in underwater lines.
Our HDPE pipes are welded in accordance with DVS 2207, EN 12201 and ISO 4427 standards. Our pipe diameters reach 160 mm. Water velocities are optimized in the 1–2 m/s range according to project flow rate; both energy loss and cavitation risk are kept to a minimum.
Welding operations are performed in the field with special equipment. Butt welding, electrofusion or flanged floating-joining techniques are used. Thanks to the flexible structure of HDPE, long pipe segments are welded on land, then floated to sea with the help of buoys. The line is guided with GPS coordinate tracking, then a controlled sinking operation is performed.

  • Special concrete sinking blocks are designed for each pipe segment. The blocks both provide negative buoyancy and guarantee that the line remains stable without being affected by bottom currents

  • Anchoring calculations made by considering current and wave loads ensure that the line operates safely for many years

  • Bottom excavation, dredging, filling and ground improvement works are carried out during placement on the seabed

  • If ground bearing capacity is low, stabilization is done with geotextile covers or gravel fill layers

  • After the sinking operation is completed, the line is inspected with remotely controlled underwater robots; level, position and connection points are verified

DEEP SEA DISCHARGE AND DIFFUSER SYSTEMS

The aim in sea discharge systems is to deliver treated water to the marine environment at the right depth, at the right speed and in a controlled manner. The diffuser system is the key component of this work. Diffusers are usually located in the last 50–200 meters of the line.
Here, water is mixed with the sea at high speed through nozzles or slotted outlets. Outlet velocity is usually selected in the 3-6 m/s range; thus, water mixes with the surrounding seawater in a short distance, providing dilution. The direction and angle of diffusers are determined according to current velocity and seabed morphology; thus, discharge occurs without leaving a permanent impact on the marine ecosystem.
Single-sided or double-sided diffuser arms can be used depending on the project. HDPE diffuser arms offer a long-lasting solution with their flexible, corrosion-free and maintenance-free structure. The number, diameter and spacing of nozzles are optimized with CFD modeling and dilution analyses.

CONSTRUCTION, GROUND AND FIELD APPLICATIONS

Seawater intake and discharge lines require serious logistics planning in the field. Project-specific sinking platforms, buoy systems, crane floating lines and marine vehicles are planned.

  • During the installation phase, sea conditions, current direction, wind speed and wave height are continuously monitored

  • Bottom scanning is performed along the line route, seabed profile is mapped

  • When necessary, the line bed is prepared with seabed excavation and filling

  • In soft soils, load distribution is provided using geotextile underlays and gravel cushions

  • Sinking blocks and anchors are sized specifically for the project; long-term stability of the line is guaranteed

  • The coastal connection section of the line is usually made as a transition from shore to sea with micro tunnel or protective casing pipe. With this method, both the coastal ecosystem is protected and the line is isolated from wave effects

QUALITY, CONTROL AND COMMISSIONING

Every weld, every connection, every test made along the entire line is recorded. In our projects, hydrostatic tests, leak tests, flow measurements and post-sinking underwater imaging are standard practices. The coordinates, depth and slope of each segment are documented with GPS.
At the end of the entire process, not just a pipeline but a documented, controlled and traceable system is delivered to the customer. Both mechanical and hydraulic tests are performed during system commissioning; water intake and discharge functions are simulated. As a result, a system is obtained that will serve for years without harming the marine environment, operating efficiently and requiring no maintenance.
Seawater intake and deep sea discharge systems require excellent interdisciplinary cooperation. As PİLSAN, we not only manage this process; we measure, analyze and record every step. Establishing long-lasting, environmentally compatible and highly efficient lines without harming the nature of the sea is our area of expertise.