Union Rotorua
| History | |
|---|---|
| Name: | Union Rotorua |
| Owner: | USSCo 1977-1998 |
| Port of registry: | New Zealand |
| Route: | Trans Tasman |
| Builder: | Broken Hill Pty, Whyalla Steelworks |
| Cost: | $30 million |
| Yard number: | 60 |
| Launched: | 19 January 1976 |
| Completed: | 1976 |
| Identification: | IMO 7366221 |
| Fate: | Broken up Alang, India 1988 |
| General characteristics | |
| Type: | Container and Ro-Ro |
| Tonnage: | 23,971 GRT |
| Length: | 203.2m LOA |
| Beam: | 26.3m |
| Propulsion: | 1 x General Electric MM5262RB Gas Turbine |
| Speed: | 19kts |
Union Rotorua was a large ro-ro vessel operated on the trans Tasman route by the Union Steam Ship Company of New Zealand (USSCo.). Along with her sister ship Union Rotoiti, she was unusual in that she was originally powered by gas turbine / electric system.
Union Rotorua was built by Broken Hill Pty (BHP) at the Whyalla Steelworks in South Australia. She was launched on 19 January 1976. Delivery was delayed by a year and costs blew out by $8 million bringing the total cost to $30 million. It was subsequently acknowledge that Rotoiti and her sister ship Rotorua could have been built for half the price if they had been built outside of Australia.
Union Rotorua was unusual in that she was powered by gas turbine. The ship's main gas turbine / electric machinery consisted of a single General Electric MM5262RB gas turbine operating on a regenerative cycle. This was coupled to an A.C. generator to provide a maximum designed continuous rating of 18822 kW for a motor propeller speed of 200rpm. The turbine speed of 4670rpm was reduced to 1500rpm for the generator by a reduction gearbox. The generator output 6.6kV 3-phase at 50 Hz to the ships motors. There were four closed air circuit water cooled synchronous A.C. motors, arranged with two per shaft. Previous USSCo vessels had traditionally had twin outward turning fixed pitch propellers, however the Union Rotorua has twin inward turning controllable pitch propellers. This decision was made in the interests of maneuverability, since the center of thrust is in the outer part of the disk thus giving a larger turning moment arm. In normal running configuration the whole system could be controlled by a single lever from the bridge. The speed of the gas turbine was controlled by a solid state control and safety system integrated with the propulsion controls.
The Union Rotorua was also interesting in its use of ro-ro for the Trans Tasman route. The cargo did not necessarily just contain truck and trailer units, but was also cargo stacked in the decks using forklifts. This necessitated the vehicle decks of the ship being build to withstand the loading of up to 39t per axle that could be exerted by a heavy forklift. Union Rotorua was built with a large angled stern ramp that allowed her to unload her cargo at any wharf without the need for a specialist linkspan as required by most ro-ro ships. She also had a bow door which could be used if a linkspan was present in a port, thus allowing cargo to be worked both forward and aft speeding up turn around time.
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