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Tug technology

AHEAD OF THE PACK

Rolls-Royce have the technology and the experience to keep you in front of the competition

RR Marine Tug Campaign Nov 2017.indb 1 21/11/2017 14:07

Foremost we are a supplier of equipment for tugs, from complete systems to individual

products. Our range runs from engines to propulsion systems, winches and other deck machinery, electrical systems and the expanding area of ship intelligence with remote and autonomous operation.

In these pages we highlight systems and product developments that are most relevant to today’s changing tug market. Many of the world’s tugs are old and technically outdated, and need to be replaced by more capable and efficient vessels with lower emissions. We work closely with owners, yards and designers to achieve this goal.

As ship sizes increase, so will the requirements for agile tugs with high bollard pull. Our azimuth thrusters are well-proven, efficient and available in a range of sizes up to 90 tonnes bollard pull, suiting the

vast majority of shiphandling tugs. They are supported by our global service organisation and our thruster exchange pool.

With growing focus on port emissions and fuel costs, hybrid battery solutions are increasingly attractive. We can provide full solutions including shore power connections.

We manufacture both diesel and gas engines that meet the latest emissions requirements and can be used with mechanical or electrical transmissions, or in hybrid installations.

Both diesel and pure gas engines are included in our range, so we can meet your requirements for varying tug operating profiles.

We provide both towing and escort winches. Depending on the application we can supply winches with four different types of drive and now an escort winch range featuring our permanent magnet technology.

m e e t i n g d e m a n dw e s u p p l y s y s t e m s a n d e q u i p m e n t f o r t h e c h a n g i n g t u g m a r k e t

Winches

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Bridge controls

Thrusters

Power electrics

Engines

tug technology

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This example of a detailed Rolls-Royce study of propulsion system choices for a notional 60-tonne bollard

pull shiphandling tug, considers the capital cost (CAPEX), operational cost (OPEX) and emissions picture in each case.

The baseline case for the study is a diesel engined stern drive thruster tug with high speed engines using MGO as fuel. A representative operational profile has been based on data from a major tug owner using measurements of two harbour tugs over a one-month period and assumes two back-to-back ship assists per day. All the alternatives considered have the same thrust, and a day schedule is assumed to allow for battery performance analysis in battery hybrid examples.

A breakdown of the data shows that 22% of time is spent on ship assist, 17% in transit, 7% on standby and the remaining 54% at the quay.

Several mechanical drive cases were examined. The baseline is two 1,920kW

engines coupled to two US205FP azimuth thrusters with small auxiliary gensets covering hotel loads.

Then there are PTO/PTI systems using two 1,460kW engines with mechanical transmission to US205FP thrusters plus a 1,460kW genset which can drive the props via a PTO/PTI electrical machine on each gearbox. Two further analyses consider the same system but with the addition of two small (215kWh) batteries, or 920kW engines supplemented by two 500kWh batteries.

The LNG-fuelled case uses two medium speed gas engines with mechanical transmission to the thrusters.

Three diesel electric cases considered are 3 x 1,380kW gensets and electric motors to drive the thrusters; the same but with two 215kWh batteries added; and a big battery solution with two 650kW diesel gensets and two 500kWh batteries.

Finally two purely battery systems were analysed, both with two batteries of 250kWh or 500kWh, but exploring the advantage of permanent magnet

propulsion motors against induction motors. Here the point is that while the full load efficiencies of the two machines are comparable, the PM motor maintains high efficiency down to very low loads whereas the induction motor efficiency drops away. Since tugs operate at an average of 15% MCR, the PM solution can save on battery capacity.

Three cases have been considered basing the energy consumption on the same operating profile and PM motors. One is for a battery large enough for the day’s operations. The other two assume that smaller batteries can be recharged two or three times in the course of 24 hours. In each case the daily energy consumption is the same, and battery sizing is conservative, discharging to 20% and rated for long-life.

To allow analysis, cost and price assumptions have to be made. Here, diesel fuel is assumed to cost 600 USD/tonne, industrial electricity 0.10 USD/kWh. Batteries are costed at 475 Euros/kWh. The tug capital loan period is

Our expertise in analysing data and understanding performance can deliver the best possible solution to meet your needs

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set at three years and a rate of 7.5%. The graph summarises the impact of the various options. The conclusion is that emissions can indeed be reduced, and zero emissions (assuming the grid electricity is clean) can be achieved – at a price. Hitherto capital cost has been the driver, with the diesel mechanical tug the winner. Mechanical PTI/PTO

systems provide better engine loading and reduction in emissions, with battery hybrids cutting emissions further but costing more. A reduced battery capacity can bring the no-emissions solution into closer price competition with other energy sources and propulsion systems, if the need to recharge during the working day is acceptable.

f i n d i n g t h e b e s t

s o l u t i o n

Transit17%

Standby7%

Dock54%

Ship Assist22%

ABOVE: Typical harbour tug operational profile.

LEFT: Shown here is Delta Billie, a good example of an efficient diesel mechanical thruster tug in operation.

Emission Reduction Costs1. MECH

2. MECH PTI

3. MECH PTI Small Battery

4. MECH PTI Large Battery

5. Full Battery

1 to 2: Reduce poor loading of ME

2 to 3: Reduce poor loading of ME and add transient smoothing

3 to 4: Eliminate poor loading of ME, transient smoothing and start to use electrical grid energy

4 to 5: Transition to full battery

1 23 4 51-LNG

0%

20%

40%

80%

% e

mis

sion

of M

GO TU

G

Increase in total annual cost (CAPEX + OPEX)

60%

100%

€0m €0.1m €0.2m €0.3m €0.4m €0.5m €0.6m €0.7m

––– CO2––– NOx––– PM_2.5

MECH_PTI

MECH_PTI_BAT1

MECH_PTI_BAT2 DE

DE_BAT1

DE_BAT2

BAT_1Rech

arge

BAT_2Rech

arge

BAT_3Rech

argeMECH

Annual Capital + Operation Cost

€4.0m€3.5m€3.0m€2.5m€2.0m€1.5m€1.0m€0.5m€0m

3 years at 7.5%

Annual equipment payments Energy+Maint

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There are many ways of getting power from the engines to the propellers. When hybrid

systems combining diesel or gas engines with batteries are relevant, the choice becomes even wider, which is where our knowledge and experience of systems becomes of value to our customers.

For electric and hybrid installations we have extensive experience in power systems architecture as well as a portfolio of equipment such as frequency drives, PM motors, charging systems and shore power connections handling variable

frequency and voltage supplies. Analysis of an owner’s actual or projected operating profile for a tug allows us to advise on a suitable system and choice of equipment to achieve the best balance between capital and operating costs.

Fuel efficiency is always important and a factor of increasing importance of deciding the energy source and power system for tomorrow’s harbour tugs is the cost of reducing emissions. This is not a theoretical problem: there is public and international pressure to reduce emissions in terms of CO2 and other greenhouse gases to tackle climate change,

and to cut NOx and particulates in the interest of improving local air quality and health. Tug emissions may be a tiny part of the total, but these are often vessels operating in confined ports in urban areas where local emissions are in focus.

Also in the equation is whether the tug’s emissions are taken in isolation, or is spending money on achieving low emissions from the tug fleet seen as a good way of cutting the environmental impact of the port as a whole. Our energy management systems enable tug emissions to be calculated, and reported as necessary.

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RIGHT: A full electric tug with diesel or LNG engines, with variable engine RPM for less fuel consumption and emissions, less noise and vibration. With or without batteries.

LEFT: A full electric tug with batteries only. Charging from shore power offers zero local emissions. Shown with the new L- drive US thrusters featuring PM motors.

RIGHT: An electric drive tug with fixed diesel or LNG gensets. Ideal for vessel with variable operational profiles with low load tasks, for example standby and idling.

LEFT: The hybrid mechanical/ electrical tug with diesel or LNG engines, with variable engines RPM for less fuel consumption and emissions, less noise and vibration. With or without batteries and/or auxiliary genset. Shown here with shore power connection and the new dual input (mechanical and electrical) US thrusters.

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latest technology

Today’s key tug propulsion product from the Rolls-Royce portfolio is the US range of

azimuth thrusters. About 10,000 azimuth thrusters of various sizes have gone into service with many more on the way for tugs under construction or on order. They are applied to both stern drive thruster tugs and to tractor tugs for shiphandling and escort duties. Twelve sizes cover a power range per unit up to 5,000kW and several of the intermediate sizes have been uprated so that a smaller unit will provide a higher bollard pull.

Our US-series azimuth thrusters are robust geared mechanical thrusters with nozzles providing a very high thrust per kW of power input, so cutting the tug’s fuel consumption and emissions, and are known for their manoeuvrability due to rapid response to steering inputs.

This year we introduced a twin input and a dual input solution on our US thrusters allowing mechanical or and electric power input to the same upper gearbox.

These developments open the way for free sailing in harbour with the electric motor, light duty operation with the main engine while the electric machine acts as a generator supplying for example hotel load, and full power operation with both engine and motor. The twin input is the most compact solution where space is limited.

For some port and towing operations the agility of azimuth thruster tugs is not required and conventional shaftlines and twin screws are a cost-effective solution. For these we supply reduction gears, FP or CP propellers, nozzles and high lift rudders.

The US thruster range is being extended by a L drive version, which is under development. This combines the well known virtues of the US series underwater unit with a vertical axis PM motor replacing the upper gearbox and separate electric motor. This will make the US thruster even more compact and efficient and will be available in the range of up to 5000 kW.

A new product for the tug market

is the AZ PM azimuthing permanent magnet thruster. Rotor magnets are mounted in a ring surrounding the fixed pitch propeller, their fields interacting to turn the propeller with those produced by the stator windings which are incorporated in the nozzle. The only components inside the tug are the slip rings that convey current to the thruster and the steering motors. Currently the AZ PM 1,900 rated at between 500 – 1,100 kW is available with units in service on the research ship Gunnerus. A larger size, the AZ PM 2600, rated at between 1,000 and 2,600 kW per unit is under development. Two thusters of this size will give a pull of 83 tonnes at zero speed.

The US thrusters with upper gearboxes are ideal for mechanical drive. All the electric powered units are suitable for both diesel electric tugs and hybrids combining gensets with batteries, where the very high efficiency of the thrusters maintained over the full speed range maximises pull per unit of energy consumed.

t h r u s t i n g a h e a d w i t h o u r p r o p u l s i o n p r o d u c t s

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Our US-series azimuth thrusters are known for their manoeuvrability due to rapid response to steering inputs

LEFT: The Baydelta Cathryn is operating in the bay of San Francisco propelled by two of our US 255 thrusters.


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latest technology

Many tugs are equipped for external firefighting with fire pumps and monitors, enabling them to tackle fires on other vessels at sea or in waterfront property. Monitors delivering jets of water to a long range require powerful fire pumps. For example the lowest FiFi rating calls for 2,400m3 of water per hour, and this can be provided either by pumps driven by the vessel’s main engines or by separate diesel engines. To do its job the firefighting vessel has to hold itself in position against wind, waves and current, and also against the strong recoil force from the jets thrown by the fire monitors.

Diesel engines driving azimuth thrusters with fixed pitch propellers through a mechanical transmission are a popular and effective propulsion system. Engine speed determines propeller thrust and vessel speed, but the simple system raises a question when a main engine also drives a fire pump; how to divide the power between thruster and pump in the right proportion? The pump wants a high and constant engine speed to give the required power, but the power to position the vessel, thus fixed pitch propeller speed, can be quite low and variable.

Popular Rolls-Royce US205 and US255 thrusters are now available with a simple and elegant answer; an integrated slipping clutch. Development was spurred by customer demand.

The attraction is the potential cost saving of not

needing to buy a separate slipping clutch, thrusters with CP propellers, or a separately engine-driven pump system, which are valid but more expensive solutions.

These US series thrusters incorporate as standard a multiplate clutch in the drive to the upper gearbox pinion. Hydraulically operated, its function is to provide a smooth engagement when the thruster is coupled in with the engine running at idling speed. Here the friction heat generated by the slipping clutch is small, about 25kW for a short period.

To provide control of propeller speed for long periods while running the engine at full speed involves the clutch in slipping away many times this amount of energy as heat. The solution was to include a multiplate hydraulically operated clutch with variable pressure to define the amount of slip. When slipping, the plates are less tightly clamped to allow a large flow of lubricating oil to flow from the inside to the outside of the clutch pack between the plates, the oil carrying with it the friction heat. Little modification to the thruster was needed, and the main external change is the provision of a much larger oil cooler to cope with the heat representing the power slipped.

The result is very good control over propeller revs when the fire pump is operating, and the clutch functions as before when the thruster is coupled in but the fire pump is not needed. The system is simple and the price competitive.

BLAZING A TRAIL TO BRING FIREFIGHTING UNDER FULL CONTROL

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BELOW: The new US L drive thruster is currently under development.


We provide engines, propulsion systems, power electrical systems and automation and controls with the operator

interface for all types of tug.Our engine range covers all the

relevant powers and the portfolio includes medium and high-speed engines for liquid or gas fuels.

Medium-speed engines under the Bergen label include the C-series spanning a power range from 1,800 kW to 3,000 kW as diesel engines, and from 1,460 kW to 2,430 kW as gas engines. The larger B engines give 600kW per cylinder in a very compact footprint.

All these diesels are well-proven units, robust and durable, giving a high fuel efficiency and low emissions and can be

specified for mechanical transmission or as gensets.

The gas engines use the established Rolls-Royce lean burn combustion system for LNG or CNG fuel, with reduced CO2 emissions, very low NOx and negligible particulates. This makes them ideal for ports where reduction in shipping emissions is a requirement. Over 700 gas engines have been delivered to date, including pioneering tug installations.

Medium-speed engines are now complemented by the MTU range of high speed diesel engines which are becoming a favoured power solution for tugs.

Now a high-speed gas engine is being introduced based on the 4000-series diesel, and its first application will be in a tug under construction at Damen for Svitzer. The V16 gas engine is rated at 1,500 – 2,000kW, using double wall gas supply lines to avoid additional complex safety precautions in the engineroom. Over 3,000 hours have been devoted to test bed development of this S4000 engine including simulation of real life tug manoeuvres, the result being that the gas engine’s transient load response is comparable with today’s S4000 M63 diesel engine.

Our engine range covers all the relevant powers and engines for liquid or gas fuels.

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tug technology

YOU’VE GOT TH E POWER

We have the engines to accelerate your business


Transient engine behaviour – gas vs. diesel

Time (s)

Mea

n ef

fect

ive

pres

sure

[bar

]

Identical performance characteristics

2000 kW @1800 rpm

Acceleration diesel engine Acceleration gas engine

RIGHT: High speed power. The new MTU 4000 series gas engine.

RIGHT: The load acceptance of the S4000 gas engine is comparable to

today’s S4000 M63 diesel engine.

Choosing your engines Medium or high speed engines both have their advantages. Which is the best choice depends on the type of tug operation and the owner’s balance between CAPEX and OPEX. Broadly speaking we feel that where diesel engines are concerned, for individual engine powers below 2MW high speed engines are the best choice. Between 2-2.5MW parameters are finely balanced with the medium speed engine winning in long-term ownership due to the lower OPEX. Above about 2.5MW per unit, the medium speed engine is favoured.

Where LNG is the fuel, gas engines would follow a similar pattern but at a lower unit power level: high speed for less than 1.4MW, MS and HS more or less equal for 1.4 – 2MW; MS best match for over 2MW. But for all fuels other factors in lifetime operational profiles can easily tip the balance.

Which engine is best for you?

High speed

High speed or medium

Medium speed

Power requirement per engine

Bolla

rd P

ull

Diesel < 2MW Gas < 1,4 MW

Diesel > 3,2MW Gas > 2MW

Diesel 2-2,5MW Gas 1,4-2MW

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The move to electric equipment on board continues, and to meet the demand from tug operators for more precise

control, we have now integrated next generation PM motor technology into the tug escort winch range.

Today’s ship-assist tugs are a closely integrated combination of hull configuration, propulsion system and winches, with performance demands particularly strict for escort tugs. Other types of tug focus more on long distance towing, or emergency towing and pollution prevention.

In a routine escorting operation,

the tug runs behind the ship being escorted, connected by a towline but not interfering with the ship’s steering. If informed of an emergency on the ship, the tug acts immediately to provide force in the direction required to steer and probably stop the ship. A second escort mode is ‘dynamic ship assist’, where the tug positions itself to act as an additional rudder.

All this places great demands on the tug’s escort winch, and we supply a range of specialised winches for this application. Up to now, they have been mainly hydraulically driven, but electric drive winches are also offered. The range

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WI NC H ES FOR ALL TYPES OF TUGFlexibility, reliability and strength are the keys to success in modern shipping


has recently been updated with the escort and towing winches benefiting from the introduction of the new Rolls-Royce permanent magnet (PM) motor technology.

The PM motor gives a very high torque at low speeds. This means that only a small reduction ratio is needed in a gearbox, leading to a very low system inertia, which in turn provides excellent dynamic performance and response, important in escort and other types of tug work.

The PM motor means a smaller winch footprint and also simplifies the winch, eliminating several components subject to wear and needing maintenance. The PMTW escort winch is rated at 100-150 tonnes with great dynamic sensitivity and a line speed up to 180m/min. With energy saving very much in focus for tug operators and ports, the PM winch has the regenerative capacity to feed up to 1,100kW of rendering energy back into the tug’s network if the vessel’s electrical system is designed to accept it.

Hydraulic escort winches have single or double drums and can be specified with anchor chainwheels and warping ends. The key point is sensitive operation. Towline can be paid out or hauled in under full control without the line going slack using the autotension system. Recovery force is adjustable in the range 0-120 tonnes, and rendering force adjustable

from 0-175 tonnes. The powerful brake can hold 420 tonnes.

For other towing operations we provide a wide range of winches of different configurations and sizes. They typically have a large line capacity and the focus is on pull and brake load and accurate spooling. Single drum, double drum and waterfall types are supplied to suit the requirements with a choice of hydraulic, AC electric or PM electric drive and either on/off or adjustable force brakes. High torque hydraulic motors plug into the gearcase and pipes and valves have been replaced by valve blocks, reducing the number of components and risk of oil leakage. Power for hydraulic winches can be supplied either from engine PTOs or separate powerpacks. Higher rope speeds are now available in both directions.

Towing winches range from small single drum units up to 50 tonnes pull for typical harbour tugs to the specialised anchorhandling/towing winches with up to 600 tonnes pull for large offshore AHTS vessels.

Tugs work with ropes and wires under high tension in rapidly changing situations. Safety of both crew and vessel is number one priority. Thus, Rolls-Royce towing winches can be optionally equipped with quick release systems enabling a safe and quick release process in three seconds at all operational conditions.

The range has recently been updated and benefits from new technology

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environmental footprint vessel efficiency remain main drivers now and going forward. We are proud to be partnering with Rolls-Royce in this high-level research and development of systems for remote operation.”

A year earlier Svitzer had identified Rolls-Royce as having the right expertise to help it reach its goals and a joint project team began work on designing, building and equipping the tug. The work included combining multiple off-the- shelf sensors such as high definition cameras, radar, LiDAR and a digital map of the harbour. Encrypted information from the tug appears on the bridge system which is secure in the Remote Operations Centre

Svitzer Hermod recently made a short trip in Copenhagen harbour, but one that brings

remote control and eventually autonomous operation of tugs significantly closer. Starting from the quay, the tug berthed again, moved away, turned through 360 degrees, then sailed to the Svitzer HQ, all under the command of an operator sitting at a state-of-the-art control station in the headquarters building. This exercise confirmed the

practicality of remote tug operation, together with the necessary communications and data security.

Following the test trip, Kristian Brauner, who is Chief Technology Officer for Svitzer, said: “As the largest global towage company, Svitzer is actively engaging in projects that allow us to explore innovative ways to improve the safety and efficiency of towage operations to benefit our customers and crews. With its direct impact on our customer performance, operational cost and

Remote control is now realistic from the technology point of view

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tug technology

ABOVE: The captain’s chair sits in front of the video wall at the heart of the remote operational centre (ROC).

REMOTE IS NO LONGER FAR AWAYWith a new generation of technology emerging, the future is closer than ever


(ROC) at Svitzer HQ. Svitzer Hermod is the first tug to be fitted with a Rolls-Royce dynamic positioning (DP) system, data from which appears on a screen at the ROC, and which maintains course and heading at much higher vessel speeds than normal DP.

The tug is remote controlled from the ROC where the captain sits in his chair between two consoles on which are the DP joystick and thruster control handles, facing a video wall showing the view from the tug’s wheelhouse. Radar and DP information is displayed on two screens on the consoles, with an ECDIS chart display on screens below the video wall.

Remote control is now realistic from the technology point of view, but the legal framework for constructing and operating such a vessel is still developing. So the closely supervised demonstration in Copenhagen was sanctioned by the Danish Maritime Authority with guidance from Lloyd’s Register on safety, including having the tug’s full crew on board during the test.

“A successful first test is only the beginning,” said Karno Tenuovo, SVP for Ship Intelligence in Rolls-Royce. “We intend to continue developing and testing the ROC whilst continuing our drive for more autonomy in ships.”

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The world’s first remote operated tug, Svitzer Hermod, owned by Svitzer and based in Copenhagen.

ABOVE: The captain’s chair is currently housed in a purpose-built secure room in Svitzer’s HQ.

REMOTE IS NO LONGER FAR AWAYWith a new generation of technology emerging, the future is closer than ever


© 2017 Rolls-Royce plcThe information in this document is the property of Rolls-Royce plc and may not be copied or communicated to a third party, or used for any purpose other than that for which it is supplied without the express written consent of Rolls-Royce plc. This information is given in good faith based upon the latest information available to Rolls-Royce plc, no warranty or representation is given concerning such information, which must not be taken as establishing any contractual or other commitment binding upon Rolls-Royce plc or any of its subsidiary or associated companies.

H ER E FOR YOUGlobal but local, we help you manage the vital balance between operational availability and cost

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Contacts www.rolls-royce.com/products-and-services/marine/contacts-and-service-locations.aspx

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Further information24/7 support

Services workshops

Services locations

Training centres

Rolls-Royce is committed to supporting our customers wherever they operate to ensure unscheduled downtime is minimised, safety is assured and optimum asset performance is achieved. We offer you:

• Spare parts and field service support backed by OEM warranty

• Equipment repair through our global network of ISO approved service centres

• 24/7 technical support services• Exchange and upgrade

programmes to improve efficiency, reduce emissions and ensure optimum asset performance throughout the life cycle

• Maintenance planning support to manage docking schedules and ensure rapid turnarounds

• A range of advanced life cycle management services designed around your operational needs


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