Dynamic Oval Towing System

by: P.P.A. Snijders MSc. B.Eng.

DOT® is a registered trademark of Mampaey Offshore Industries B.V.The DOT system is protected by patents.

Agenda:• Introduction to Mampaey• 360° all around towing evolution• Benefits of the system• Development• How we work• DOT® 30 for Harbor Tug Application• Future Developments• Conclusion

Mampaey Offshore Industries B.V.• Over 100 Years experience in towage

industries• Designer of the Quick Release Towing Hook• Designer of the Quick Release Mooring Hook• Market leader in safe Towing & Mooring

Solutions

Early Mampaey

Towing Hook

Quick Release Disk Type Towing Hook

• For towing with all towing materials• Ranging from 5 to 250 tons SWL

Radial support• Widely applied on tugs• Safety measure against capsizing • 180 degree support

….. and further

Mampaey DOT® System360° all around towing platform

How does it looks like?

A Tug equipped with a DOT

Can do anything a conventional tug can!

And in addition to that the DOT enhances the: • Safety, since it can not capsize anymore• Efficiency, since it makes use of the

hydrodynamic forces• Flexibility, since it integrates all towing

operations into one system with a continuous towline connection

• Controllability, even at higher speeds

Without any restrictions to any other operation

The DOT-system:

• Safety

• Efficiency

• Flexibility

• Controllability

Safety• Stability is significantly increased by a

movable towline attachment– Capsizing due to towline forces is

prevented

The DOT-system:

• Safety

• Efficiency

• Flexibility

• Controllability

Stability increases Safety

The DOT-system:

• Safety

• Efficiency

• Flexibility

• Controllability

Stability Fixed Towing Point

The DOT-system:

• Safety

• Efficiency

• Flexibility

• Controllability

Reasonable risk of capsizing due to towline forces is unlikely!

Stability with 360° towingLikeliness of capsizing due to towline forces is unlikely!

The DOT-system:

• Safety

• Efficiency

• Flexibility

• Controllability

Efficiency• Taking advantage of forces

– Since the tug can not capsize anymore, the tugs’ resistance in all directions can be used for generating steering and breaking forces.

– Use of Dynamic forces instead of straight propulsion power saves fuel

The DOT-system:

• Safety

• Efficiency

• Flexibility

• Controllability

Hydrodynamic ForcesSince the tug can not capsize anymore….

The DOT-system:

• Safety

• Efficiency

• Flexibility

• Controllability

Full FlexibilityFull scope of towing operations

integrated in one single system:

• Standard conventional towing over the stern (unchanged)

• Dynamic escorting over the bow• Dynamic braking and steering from the

sides

Smooth operation with continuous towline connection.

The DOT-system:

• Safety

• Efficiency

• Flexibility

• Controllability

Conversion to a DOT-tug

The DOT-system:

• Safety

• Efficiency

• Flexibility

• Controllability

Remember, a tug equipped with a DOTCan do anything a conventional tug can!

The DOT-system:

• Safety

• Efficiency

• Flexibility

• Controllability

And much more, like dynamic breaking and steering from the sides

The DOT-system:

• Safety

• Efficiency

• Flexibility

• Controllability

and dynamic escorting over the bow

The DOT-system:

• Safety

• Efficiency

• Flexibility

• Controllability

Full Controllability• Controllability in all directions

The oval shape matches the towline force with the tugs’ resistance in one towing system for all directions.

The DOT-system:

• Safety

• Efficiency

• Flexibility

• Controllability

Full Controllability

• Is achieved with minimal use of propulsion power when the towline force is matched with the hydrodynamic forces.

The DOT-system:

• Safety

• Efficiency

• Flexibility

• Controllability

When towline forces are not alignedTug will rotate….

The DOT-system:

• Safety

• Efficiency

• Flexibility

• Controllability

When towline forces are not aligned

until the forces are aligned Tug will rotate….

The DOT-system:

• Safety

• Efficiency

• Flexibility

• Controllability

Controlling direction of tugOption 1: Conventional “Solving” Solution; Engine Power

The DOT-system:

• Safety

• Efficiency

• Flexibility

• Controllability

limited to a certain speed and propulsion power!

Controlling direction of tugOption 2: “Dissolving” the Problem; Aligning Towline Force

The DOT-system:

• Safety

• Efficiency

• Flexibility

• Controllability

In control without engine power at any speed!

Controllability when:

• Full controllability is achieved with minimal use of propulsion power when the towline force is matched with the hydrodynamic forces.

BUT……

• The position of the center of lateral resistance is different when the direction of the tug changes.

The DOT-system:

• Safety

• Efficiency

• Flexibility

• Controllability

That’s why current tugs have two towing installations:

1 2The DOT-system:

• Safety

• Efficiency

• Flexibility

• Controllability

The changing of the hull forces How to align the towline with the forces acting upon the

hull for all directions into one towing system?

Only an OVAL can do this!

The DOT-system:

• Safety

• Efficiency

• Flexibility

• Controllability

An oval with moving carriages

The DOT-system:

• Safety

• Efficiency

• Flexibility

• Controllability

is always matching the towline with the hydrodynamic forces!

An oval with moving carriages

The DOT-system:

• Safety

• Efficiency

• Flexibility

• Controllability

is always matching the towline with the hydrodynamic forces!

An oval with moving carriages

The DOT-system:

• Safety

• Efficiency

• Flexibility

• Controllability

is always matching the towline with the hydrodynamic forces!

That’s why an Oval• High speed assistances are as safe and

controlled as low speed assistances!

• An oval is the only shape that can integrate all towing points into one towing system.

• Full control in all directions with minimal use of propulsion power!

• Sufficient space available for superstructure

DOT Rail system• Towline force is evenly distributed into

tug’s deck structure– Minimal structural material required

• Easy to integrate with new and existing tug structures

Rail system• Modular design for various towing

applications • Minimal number of (moving) parts• Insensitive to wear due to high

tolerances• Easy to assemble and interchange

components

Development• Structural design was performed by

IMC based upon state of the art Finite Elements Calculations

• Optimized for strength and cost efficiency

Testing• Scale testing for concept validation• Full scale testing for strength validation

Production• The System will be produced, as all

Mampaey products out of first quality components with class approval

First DOT15-system Sold

Owner: Peterhead Port Authority

Designer: Macduff Ship Design

Dimensions: 13 m x 5,40 m x 2,80 m

Engines 2 x 300 bhp Scania

Bollard Pull:

Delivery:

8,5 tons

April 2008

Delivered to Macduff

How can we facilitate the integration?

We can provide the following services:• A simple drawing of the system• Determining position of system• Analyzing proposed solution

What we did1. A design was sent to Mampaey

What we did2. The towing points of the tug were

determined.

What we did3. Preferred Hydrodynamic Position and

Shape was determined.

What we did4. Users profile and structural support

were taken into account.

What we did5. an AutoCAD file with the preferred

oval and position was returned.

What we did6. The designer integrated the DOT

system into the design.

What we did7. The proposed design was structurally

analyzed by an external consultancy firm IMC.

What we did8. The result meets users profile and a

high level of quality.

DOT 30 on Harbor Tug

DOT 30 on Harbor Tug

Awards• Maritime Vietnam 2006 Innovation Award• Mampaey; the most innovative SME in the

Netherlands!We have received the nr. 1 position in the Dutch Innovation Top100 organized by innovation network Syntens & bizz magazine for entrepreneurs.

• Seawork 2007 most innovative vessel design award for Macduff Ship Design by installing the first DOT system on a tug.

• Innovation Complement Award2007 of the Government of South-Holland

ConclusionThe DOT system meets the demand for the

optimal tug

The DOT system is an attribute that is:• Easy to integrate into a tug design• Simple to install and maintain• Durable in the most severe circumstances• Improving the overall performance of the tug!

Are there any Questions?