Exotic arrangement for Tropical newbuilds

Four MAN B&W 6S60ME-C8.5 main engines will power Tropical Shipping's four 1,100 teu container ships
Four MAN B&W 6S60ME-C8.5 main engines will power Tropical Shipping's four 1,100 teu container ships
Propeller with fairing cone, stern tube and shaft system including clutch coupling for connection to main engine
Propeller with fairing cone, stern tube and shaft system including clutch coupling for connection to main engine
Electric propulsion powered by gensets is one of three operating modes available using the versatile arrangement on Tropical Shipping's newbuilds
Electric propulsion powered by gensets is one of three operating modes available using the versatile arrangement on Tropical Shipping's newbuilds

A series of MAN propulsion packages ordered for Caribbean freight operator Tropical Shipping’s new container vessels, to be built in China, are unusual in their inclusion of hybrid propulsion capability.

The company has ordered four 1,100 teu container vessels, each equipped with a MAN B&W 6S60ME-C8.5 main engine, complete with TCA66-21 turbocharger and an selective catalytic reduction (SCR) module to achieve IMO NOx Tier III compliance. The propulsion package also features three MAN 6L23/30 Holeby gensets with MAN TCR14 turbochargers, as well as the latest generation of controllable pitch (CP) propeller - the VBS1550-5 Mk 5, a five-bladed design combined with MAN Alpha rudder-bulb. The vessels’ propulsion systems are ice-prepared and classed to Bureau Veritas ice class 1C.

Tropical Shipping has also ordered two 300 teu container vessels, each powered by a MAN 27/38 engines, with TCR turbochargers. The ships are due to enter service from June 2018.

Bjarne Foldager, vice president, promotion & sales, two-stroke business, MAN Diesel & Turbo, says: “The marine market is currently very challenging but, in winning orders like this, we see some green shoots of recovery. Tropical Shipping has chosen to expand its fleet with proven technology from our portfolio and I am confident they will be served well by it.”

MAN Diesel & Turbo initially introduced electronic, fuel injection control on its large bore, ME-C engines, which are a more compact form of their ME-B counterparts. The ME-C range’s electronic controls are characterised by:

  • Fully integrated electronic controls;
  • Low specific fuel oil consumption;
  • Superior performance parameters;
  • Appropriate fuel injection pressure and rate shaping at any load;
  • Much improved emission characteristics;
  • Smokeless operation at any load;
  • Lower NOx on command.

These advantages are gained by the use of variable, electronically controlled timing of fuel injection and exhaust valves during operation. Additionally, all software and hardware are upgradable for the lifetime of the engine.

MAN Diesel & Turbo describes the 23/30 engine genset as one of its most successful workhorses, with a half-century history of operational experience and over 12,000 sales to date. The engine is popular with shipowners for its reliability and ‘forgiving’ service demands, the engine designer notes.

Applications for the engine include tankers, bulk carriers and product tankers as auxiliary engines. It is for the most part HFO-driven with gas and marine oil also used in special environmental areas.

The 23/30 engine is optimised for part-load operation, typically at 40-65%, and features a mean effective pressure of less than 20 bar. As a result, the engine experiences reduced operative stress compared to similarly sized engines, meaning a decreased demand for spare parts and significantly reduced running costs over its lifetime.

The 1,100-teu container vessels are equipped with the latest generation of CP propellers, the VBS1550-5 Mk 5 unit. This 5-bladed design (6,200mm diameter), combined with the MAN Alpha rudder bulb and fairing-cone concept, offers high efficiency over a wide operating range, and low noise and vibration levels.

For environmental protection and elimination of the risk of stern tube oil leakages, a water-lubricated stern-tube system has been specified. The system includes a water supply/water quality package to ensure a steady flow of non-abrasive water to the stern tube bearings. The steel propeller-tail shaft is fitted with bronze liners, coated in between with an anticorrosion epoxy.

For auxiliary power generation, a 2,000kW shaft alternator/motor, driven via a Renk SHH tunnel gear, provides for the ship’s electrical power in normal seagoing operation. To comply with the Bureau Veritas AVMAPS notation for alternative propulsion, the plant is also equipped with a Renk KAZ shaft clutch for engine disconnecting. Accordingly, the propeller can be driven via the tunnel gear and shaft motor at reduced propeller speed to maintain the required minimum vessel speed of seven knots in APS-mode. Electrical power for propulsion in auxiliary propulsion system (APS) mode is supplied by the gensets.

The various operation modes are controlled by the Alphatronic 3000 propulsion control system and, combined with the integrated fuel-saving speed pilot, this ensures the optimum plant operation and at the lowest operational costs. The normal operating modes are accordingly:

  • Combinator mode – with automatically controlled optimum relation between propeller pitch and rpm speed setting;
  • Constant speed mode at shaft-alternator operation – for the propeller running at fixed speed;
  • APS mode (auxiliary propulsion system/power take-home) where the shaft alternator operates as an electric drive motor at reduced speed – driving the propeller with the main engine clutched out.

The Alphatronic 3000 propulsion control system is delivered with maneuvering, control and display panels for control consoles at the main bridge, starboard and port bridge wings, along with the engine-control room.

Tropical Shipping has operated its freight-shipping service between Canada or South Florida and the Caribbean and Bahamas for over a half-century. The company delivers cargo-transportation services including dry, refrigerated, and less than container load. With its fleet of 15 vessels, Tropical Shipping provides direct services to Florida, the Bahamas, and the Caribbean.

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