Matching propulsion packages makes sense

An integrated propulsion package represents a step forward from the European style of extensive and expensive tailoring towards competitively-priced high quality solutions meeting the demands of the Asian shipbuilding market, Wärtsilä suggests

True propulsion packages, such as the Wärtsilä Propac, dictate considerable effort in choosing the right components. The issue is not about merely choosing the products from a basket of ‘whatever happens to be there’ but actively developing a product portfolio in which technologies and performance match.

Unknown or contradictory component and package main dimensions can result in the following typical problems:

• inadequate space reservation for the shaft alternator

• collision between gearbox and engine charge air receiver

• total installation length versus engineroom length.

Such collisions can be avoided by carefully preselecting components and ensuring that design data is available at an early stage. Performance-related compatibility is a more demanding requirement, best secured through the feedback collected from a large number of propulsion packages built with the same in-house main components.

Building packages requires an in-depth knowledge of the particular application: the package requirements for a tug, for example, differ completely from those of a feeder container ship.

Suitable outline specifications must be prepared. Equipment must be pre-engineered so that components match, and integrated solutions meeting stringent performance requirements can be offered without extensive time-consuming negotiations, even though the enquiries received are brief and provide little detail.

Wärtsilä can package mainly in-house products from its various ship power knowledge centres. Its Propac integration work started with the Wärtsilä 20 and Wärtsilä 26 medium speed engines combined with Wärtsilä gearsets and Wärtsilä-Lips CP D-hub propellers, and Wärtsilä’s JMT seals and bearings. Steerable compact thrusters with either CP or fixed pitch propellers were also available.

Packages were subsequently developed for higher output installations based on Wärtsilä 32, 38 and 46 medium speed engines for applications such as general cargo and feeder container ships. Even more powerful systems can be created from the group’s Sulzer low speed engine programme.

Propellers can be fixed pitch or CP designs, with four or five blades and in aluminium bronze or stainless steel; Wärtsilä-Lips steerable thrusters and waterjets are also available as propulsors. Control systems may be tailored with various programmable logic controllers using conventional relay automation or based on distributed smart controls and bus communication.

Wärtsilä’s recent acquisition of Norway-based Aker Kvaerner Power and Automation Systems will enhance the group’s system integration capabilities in diesel-electric propulsion, power distribution and automation projects, especially in the offshore sector.

A number of benefits are offered by pre-engineered packages, Wärtsilä citing:

• improved accuracy of specification

• reduced pricing ‘safety margin’

• good technical support during project management; installation planning instructions made available instantaneously, with only a few final fine-tuned drawings supplied later

• little technical risk; reliable main dimensions and weights at the negotiation stage

• predictable performance, whether for ship’s speed, bollard pull or any other parameter

• well-managed commissioning with efficient use of resources

• high quality instructions, user manuals and spare parts books.

Wärtsilä acknowledges that standardisation is not always recognised as a positive feature by yards and owners, for whom every project is unique, but its Propac concept allows for project-specific engineering in key areas.

Shaft arrangements, for example, are always finalised according to the demand of the project. Detailed alignment and torsional and whirling vibration calculations are made, even though numerous references and experience from deliveries provide a good basis for component selection. Hydrodynamic optimisation of the propeller blades is also carried out for each project, tapping in-house expertise.

Extending monitoring and wiring diagrams to beyond the pre-configured platform dictates project-specific design but is easily accomplished because most of the package monitoring work is already well defined. Due consideration, however, is given to designing entirely new options not covered by the existing Propac platform.

Commissioning and project costs are always charged to the product, a fact sometimes ignored when looking for short term interest and accepting poorly defined areas of responsibility, according to Wärtsilä.

Pre-configured propulsion packages make it possible to specify commissioning in detail and to define clear responsibility limits. Reporting matches the initial plan defined in specific and clear work cards.

Due for handover in May to Bourbon Offshore Norway is an 83.6m-long anchor handling/towing/supply vessel from Ulstein Verft with a Wärtsilä package of main gensets, thrusters, control system and seals.

A speed of 17.5 knots and a minimum bollard pull of 180 tonnes are anticipated from a power plant based on four 6-cylinder Wärtsilä 32 and two 9-cylinder W20 diesel gensets supplying a propulsion and manoeuvring system comprising: two Lips CS3500/3500WN main steerable thrusters, a Lips CS250-250/MNR retractable bow steerable thruster and a Lips CT250M-D bow tunnel thruster.

Rated at 5,000kW apiece, each main thruster incorporates a 3.6m-diameter CP propeller running in a Lips HR nozzle. The 1,800kW bow steerable thruster has a 2.4m-diameter CP propeller and the 1,200kW bow tunnel thruster a 2.5m-diameter CP propeller. All four thrusters, equipped with JMT MkII Unnet shaft seals, will be controlled through a Lipstronic/T control system providing both joystick control for manoeuvring and full dynamic positioning.

Among recent projects booked by another prolific packager, MAN B&W Diesel is to supply twin-screw medium speed propulsion outfits for a pair of 65m-long offshore research vessels to be built by the Liao Nan Shipyard in China for BGP/CNPC (China National Petroleum Corporation). One will be equipped for seismic sourcing, the other for seismic recording.

“Very low levels of vibration and noise from propellers, engines and propulsion systems are key issues for the installations,” explains MAN B&W Diesel’s four-stroke propulsion sales manager Jorgen Vinde.

“A very soft resilient seating arrangement of baseframe and sandwich mountings has been applied for dampening structure-borne vibrations by up to 97 per cent. Additionally, the ducted propellers have been specially designed and shaped with high priority given to low levels of cavitation and noise emission.

“From an underwater viewpoint, an absolutely decisive factor for the customer is a very silent ship, with minimal noise emission and disturbance in relation to the seismic exploration equipment.”

Both vessels will feature a twin-screw Alpha propulsion system based on two MAN B&W 6-cylinder L23/30A-D engines, each developing 960kW at 900 rpm and driving an Alpha type VB560 four-bladed CP propeller via an Alpha AMG8 gearbox type 31VO8 with a speed reduction ratio of 900:292 rpm. The propellers will run in FD1930 type nozzles, also part of the supply package.

The 1.9m-diameter CPP systems will be supplied complete with tailshafts, intermediate shafts, bearings and sterntube equipment. Epoxy-coated tailshafts with bronze liners are specified for the water-lubricated sterntubes.

In addition to the twin main bridge control station, a complete Alphatronic IIA propulsion control and safety system will include a twin engineroom control station.

Also in the MAN B&W Diesel production backlog are twin-screw medium speed propulsion packages for six AHTS vessels ordered from Labroy Shipyard in Indonesia for operation by Swire Pacific Offshore. The 66m-long vessels were designed by UK-based IMT Marine Consultants and optimised for worldwide service with the Singapore-based operator.

According to MAN B&W Diesel’s international offshore group’s senior sales manager Steven Birdsall, three decisive factors influenced Swire Pacific’s selection:

• the ability to procure a total propulsion package from the same manufacturer, including the main engines, gearboxes, shafting, propellers, nozzles, and propulsion control and management system

• the capability of the same engine series to cover all the propulsion power requirements of AHTS vessels with varying sizes (60 to 120-ton bollard pulls), thus enabling interchangeability of spares and trained engineers who could be transferred between the vessels

• a willingness by MAN B&W to tailor-make an integrated package meeting Swire’s operational requirements for present and future projects.

An output of 6,570kW from the twin-screw Alpha propulsion package is expected to secure a bollard pull exceeding 120 tonnes and an optimised service speed of 13.5 knots. Each MAN B&W 9-cylinder L27/38 engine, developing 3,285kW at 800 rpm, will drive an Alpha type VBS980 four-bladed CP propeller via an Alpha AMG55 (type 57VO55EV) gearbox with a speed reduction ratio of 800:141 rpm.

Both engines will be fitted with a full power PTO and integrated journal bearing at the front end configured to drive a firefighting pump outfit; and each gearbox will be arranged to drive a 1,600 kVA shaft alternator from an 1,800 rpm PTO. The 3.8m-diameter ducted CP systems (with MAN B&W type AHT nozzles) will be supplied complete with tail and intermediate shafts and bearings, and sterntube equipment.

In addition to the engineroom control station, the Alphatronic 2000 monitoring, control and safety system will include a main bridge control station and an aft bridge slave control station. Propulsion control is interfaced to a joystick/Dyn Pos system which manages the overall ship manoeuvring via gyrocompass, rudders and thrusters.

Rolls-Royce taps group specialities to design and supply propulsion packages based on its Bergen medium speed engines, Kamewa Ulstein propellers and/or Ulstein Aquamaster azimuth thrusters. Its own-design portfolio also embraces Frydenbo and Tenfjord rotary vane steering gear, various rudder designs (including Ulstein Hinze flap types), deck machinery, Intering anti-roll stabilisation, and automation and control systems.

Propulsion packages are most commonly supplied to yards building the group’s popular UT700 series offshore supply and support vessels, but references are extending to mainstream cargo ships such as chemical tankers.

Two 15,000 dwt oil products/chemical tankers recently built for Turkish owners, for example, feature twin 8-cylinder Bergen B32:40 engines driving Ulstein Aquamaster azimuthing propulsors, with a 650kW Kamewa Ulstein bow thruster enhancing manoeuvrability. Rolls-Royce also supplied Rauma Brattvaag deck gear and UMAS automation systems.

A capability to optimise propulsion plant for the given operating conditions and planned deployment is stressed by Rolls-Royce, exploiting group expertise in design and hydrodynamics. Its test centre at Kristinehamn in Sweden can enhance the level of interaction between the individual systems and the hull to maximise operational efficiency and reliability. MP