Shark helps thruster manufacturer move in right direction


When a new large vessel is put to sea, it is usually equipped with a tunnel thruster which acts as a side propeller system to enhance maneuverability at berth and in open waters.

Tunnel thrusters, sometimes called bow thrusters, provide captains with increased control and can help to quickly turn a ship around. 

Brunvoll AS is a global manufacturer of seaworthy motion systems with headquarters in Molde, Norway. The company has supplied more than 8,000 complete side propeller systems mounted on more than 5,000 different cruise ships, supply boats and navy vessels.


Brunvoll’s offer consists of five different types of tunnel thrusters, with each available in a variety of sizes, including between 3 to 10 feet in diameter and a single engine power between 150-4500hp.
Roy Unhjem, Machine Tool Maintenance Lead at Brunvoll, said “In a normal year we deliver about 350 tunnel thrusters in different variants. In addition to the standard variant, we have a tunnel thruster with extra shock absorption. It reduces sound and vibration, so is mainly sold to cruise ships.

“The actual tunnel thrusters - besides software and control systems – are manufactured in three different materials. The outside of the tunnel which surrounds the propeller is made of steel sheets, cut, rolled and welded. The housing is cast iron. The rotor plug and propeller blade are cased in an alloy of nickel, aluminum and bronze. In extreme cases, we have needed to produce components in acid-proof steel.”

Machining of the propeller is conducted mostly unmanned and at night due to the fragile and brittle nature of the nickel-aluminum bronze alloy. This demands a highly accurate and dependable manufacturing processes and cutting tools.

The Dormer Red Shark tap is a high performance tap primarily designed for use with steel alloys. The versatility of the Red Shark tap allows for it to be used in different dimensions and at different torque levels, for example, when threading the propeller at the attachment to the rotor.

Red Shark increases tapping ability and service life, providing users with reliability and tool economy at high cutting speeds.

To ensure optimal productivity and safety, the unmanned machines are lowered to cutting speed of 82 SFM. The ideal cutting speed in the nickel-aluminum bronze was 115 SFM. In tests, Brunvoll ran the Red Shark up to 164 SFM – exactly double the required rate.

Besides the additional productivity of the Red Shark, it offers the flexibility to be used with other materials other than just steel alloy.

Click here for more information about Dormer Pramet’s range​ of S​hark Line taps.