In our period as Van De Graaf we invented the bow coupling, which became the standard world-wide. With our bow coupling, also known as bow discharge installation, a quick connection can be made between the ship and the floating pipe line.

Bow couplings

Bow couplings are designed for efficient beach and land reclamation. Quick connection and low maintenance ensure safe working under most  circumstances and tough weather conditions. We guarantee exchangeability between our systems.

The bow discharge installation consists of the following main parts:

  • Construction: guide ring and gantry construction for integration into the bow section.
  • Bow coupling: female part and loose male part with floater for the connection with the floating pipe line.

Technical specifications

  • For inside pipe diameters: ø 350 – ø 1.100 mm.
  • Maximum swivel angle male part: 15°
  • Turning angle male part: > 360°
  • Maximum operating pressure: 10 – 30 Bar

Parts of the bow coupling

The bow coupling realizes the connection between ship and floating pipe line. The coupling itself consists of a female- and male part. The female part is fixed to the bend of the discharge pipe and the loose male part has to be mounted to the floating hose. The female part is provided with hydraulic operated cylinders for opening/closing of the retaining ring and securing the lock pins. The retaining ring clamps or releases the male part when it is positioned in the female part. Heavy lock pins secure the retaining ring when the male part is connected. The floater of the male part is a heavy duty construction and standard foam filled. The male part of the flexible coupling has an unlimited rotation.

Bow Coupling

Video: connecting the floating pipe line

This movie shows the principle function of making the connection between the male part with floater and the female part of the bow coupling. By using a deck winch and a custom made bridle, the male part is lifted up to the female part. After a clean fit the male part is locked by retaining rings, operated by hydraulic cylinders.

Bow discharge installation options

In addition to our standard design the bow discharge installation can be executed with a wide range of options:

  • integrated service frame (stainless steel) for inspection and maintenance purposes of the female part;
  • rainbow unit (fixed or insert type);
  • flange connections in discharge pipe;
  • casted bend;
  • reducing bend or ring (adapter / insert) in guide ring for using a smaller bow coupling size;
  • wear resistant liners in: discharge pipe, female- and male part;
  • extra chain guides on female part of the coupling;
  • hot dip galvanized railing and stair(s);
  • bridle (2-leg chain sling with swivel) for hoisting the male part;
  • specially designed deck foundation for split hopper dredgers.
Rainbow unit bow coupling dredger

Special dredging equipment

With more than 30 years of experience in designing and producing bow discharge installations, we have gained a high level of innovative and customized solutions.

For the trailing suction hopper dredger “Reimerswaal” we have delivered a special bow coupling installation with an in height adjustable hoisting wire sheave construction in order to make it possible to create space for the conveyor belt.

Besides that the gantry construction is completely integrated in the bow and the bow coupling is executed with an insert type rainbow nozzle.

Bow Coupling


Recent Straatman Dredging Equipment projects:

What to expect from our Straatman team

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