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 manoeuvrability 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 three to ten 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-aluminium bronze alloy. This demands a highly accurate and dependable manufacturing processes and cutting tools.
The Dormer Red Shark tap is 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 feet/minute. The ideal cutting speed in the nickel-aluminium bronze was 115 foot/minute. In tests, Brunvoll ran the Red Shark up to 164 foot/minute – 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.
The Red Shark is one of several material specific taps available from Dormer Pramet. With its unique combination of substrate, coatings and design features, the popular application-based range offers high levels of process security and performance across a range of engineering materials.
Each tap features a color ring on the tool shank denoting material suitability, promoting quick and easy tool selection.
Dormer Pramet is set to add more tools to its assortment of Shark Line taps. This includes a range of yellow ring taps for structural, carbon and low alloy steels and blue ring for stainless steels. Both promote smooth and fast chip evacuation, making them ideally suited to threading deep blind holes up to 3xD.
For more information about the Dormer Shark Line of material specific taps visit www.dormerpramet.com or contact your local Dormer Pramet sales office.