Micks Distractions

One of the things I enjoy see­ing is big engi­neer­ing. That is: Engi­neer­ing on a big scale. I had the good for­tune to be offered a guided tour of a cable lay­ing ship. Which is a ship that lays cables, (fun­nily enough).

Read on.

You will have to excuse the qual­ity of these pho­tos — they were all taken with my Nokia cam­era phone and stitched together after­wards. The qual­ity is shock­ing, but at least you get the idea.

Lay­ing cables?

A cable lay­ing ship’s pri­mary job is lay­ing fibre cables in the ocean. When you type ‘google.com.au’ most likely, (if you’re not in the US), your traf­fic is passed along these cables via fibre. Voice calls are also car­ried over it. A whole tonne of traf­fic is car­ried over these lit­tle fibres.

Ile de Sein

This ship is big, but not mas­sive. It’s gross ton­nage is 13,978, and has the capac­ity to store 5000 tonnes of cable.

ile de sein

Docked in Sydney

Docked in Sydney

Cable bins

Cables are stored in mas­sive cable bins. The Lle de Sein has two bins, as pic­tured below. These two bins had deep water cable and shal­low water cable.

Deep water cable bin

Shal­low water cable bin

The dif­fer­ence between the two types of cable is that the shal­low cable needs to be armoured and strength­ened to avoid ships scrap­ing the cable, whereas the deep sea cable just needs to pro­tect the fibre cables.

The ship lays the deep water cable at around 10km/h. The cable will finally rest on the ocean floor some 20km behind the ship. Shal­low water cable is layed at 500m/h. The rea­son for the slow speed is that at shal­low depths they have to bury the cable to at least a metre below the ocean floor. To do this they use the.…

Trencher

Which is just a mas­sive plough that they drag behind the ship and it lays the cable in the trench as it goes. The trencher depth can be con­trolled from the bridge.

Trench­ing tool — side on

The lead­ing edge, which is on the left hand side of this photo has replace­able tita­nium blades. Appar­ently after a long haul the blades come up smooth and shiny and as sharp as a razor blade.

Trench­ing tool — closeup

Trench­ing tool — from it’s rear.

Roller feed­ers

Whether it’s deep water or shal­low water cable that’s being layed; the lay­ing speed has to be con­trolled accu­rately. To do this the cable is brought out of the bins .…

Cable run — from the cable bins

.… and fed through a series of rollers. In the back­ground of the fol­low­ing pic­ture you can see the series of rollers that feed the cable out. The fore­ground is the roller drum which is used dur­ing cable repair.

Cable feed­ers — lay­ing feeders

Cable feed­ers — repair feeder

Cable feed­ers — repair feeder

When cable has to be repaired, the ship will sever the cable on the ocean floor, pick up the cable and move back 6km. The rea­son is that the cable doesn’t have enough slack to pull it all the way up from the ocean floor, (5000km down). Cable to be repaired will be wrapped sev­eral times around the big drum and hauled from the ocean floor. A join will then be made on the cable.

Repeaters

Repeaters have the job of ampli­fy­ing the sig­nal every so often. There is usu­ally a repeater every 75km.

Repeater A/C unit

Unfor­tu­nately I didn’t get a chance to take a photo of one of them. But I took a photo of the A/C unit. The repeaters have to be kept cool and at a con­stant tem­per­a­ture. The rea­son is that tem­per­a­ture changes can affect them — and when you’re about to lit­er­ally sink $100k for each repeater you want to look after it. The seabed is roughly 2C.

Each repeater also has to be pow­ered which by a 5kV DC source. When the ship is lay­ing cable they actu­ally power up the cable and run the repeaters. This is so they can check the qual­ity of the layed cable and ensure there are no issues.

The Bridge

The Bridge is where all the action is.

The Bridge

Cable con­trol room

These days cable lay­ing ships are fully auto­mated. They have high accu­racy GPS that can enable them to lay cables pretty exactly. The ship is kept at a con­stant speed to ensure the cable doesn’t over-stretch or sag. There are two bridges one fac­ing for­wards for gen­eral oper­a­tions, (com­ing and going into port), and one fac­ing back­wards for cable laying.

You can down­load all these images by click­ing on the down­load image below:

Be Socia­ble, Share!

• 

No related posts.