Supply Ships – High Tech Helps Vessels Weather Stormy Seas

How do supplies reach off-shore drilling rigs when the seas are too rough to set sail? Until now drilling equipment and other goods simply weren't delivered, often leading to production stoppages and millions of dollars in lost revenue. But now the Voith Turbo company has developed an intelligent propulsion system equipped with propellers to keep ships on course during high seas. Our reporter Hagen Tober took a ride on a high-tech supply ship setting sail from Aberdeen, Scotland. ______________________________________________________ We're underway at sea - east of the Shetland Islands. This prototype supply ship is heading to an oil platform in the North Sea. Dirk Jürgens is head of development at German mechanical engineering company Voith. On this trip he's testing a new propulsion system. Jürgens tells us about the new drive - which is a quite a novelty for a ship this size. "We've prepared an animation of it. Here we see the "Edda Fram" - and this is what the ship looks like underwater. Now we'll see the secret of the ship. These are the two Voith Schneider Propellers with their very long blades - they're three meters long - and that's what drives the ship." Now the boat will be delivering supplies to seven different drilling platforms in the space of just four days. The first stop lies somewhere between Iceland and Norway. The weather is remarkably good. But the crane operator has a difficult task... unloading containers from the bobbing ship onto the platform and back again. The new propellers are designed to keep the ship steady even in rough water. Dirk Jürgens: "We call this roll stabilization - we adjust the drive to reduce the rolling motion and stabilize the ship. This is a recent invention - and only the Voith Schneider Propeller enables the ship to hold its position dynamically and minimize the rolling motion. No other drives perform like this." At two million euros the propulsion system is twice as expensive as conventional propellers. But it makes the ship considerably more maneuverable - and lowers fuel costs. So far, all the measurements are looking good. Now that night has fallen, it's time for a special test. Dirk Jürgens is trying to see how the freighter will behave at different rotor speeds. All inside lights are turned off on the bridge and the captain revs up the engine. Suddenly the ship starts shaking violently. Dirk Jürgens, VOITH Development Manager: "The entire ship is oscillating back and forth kind of like this. My pen is the deckhouse - it swings up and down like crazy - and we're the best sensor up here." 'Natural resonance' is the term experts use to describe the phenomenon. The problem can be quickly solved with a software update to adjust the propeller's rotational speed. The next morning the sea is rough. These are ideal conditions to continue testing the roll stabilization. Just a change to the Voith Schneider propellers' direction of thrust - and suddenly the ship is lying quite still on the water. On the bridge we don't feel any rocking motion at all. So unloading freight at the drilling station should be easy. Dirk Jürgens: "Although what we had was mainly stamping and not rolling motion, we turned on the roll stabilization briefly, and it was a lot better. After the small problem we had yesterday - which is not unusual during these tests - everything's running fine now." The new drive has passed with flying colors. Even the normally camera-shy captain Dagfinn Thorbjönsen is enthusiastic: "It makes it much easier to position. We're contending with a swell of up to 2 or 3 meters. You could draw a ring one meter around the ship and you'd see - we'd now be able to stay inside that ring." For the engineers, the test is over. Weather reports say a storm is coming up - but thanks to the new propellers, deliveries are expected to go smoothly.

DW-World | November 25, 2008

Tags:. .stoppages. .shetland. .propulsion. .hagen. .fram