Page 48: of Maritime Reporter Magazine (April 1998)

PROPULSION UPDATE tion gear vibration requirements will be met.

The design phase of low noise gearing focus- es on the five areas noted below. In all cases, the basic design objective is to minimize vibra- tion stimuli. • Rotating Elements - maximize balance, roundness, concentricity; • Gear Casing - ensure rotating element support and parallelism; • Bearings - optimize stability; • Couplings - optimize arrangement and shafting system dynamics; and • Mesh Design - maximize uniformity of load transfer.

The benefits of these low noise gearing design features are realized through manufac-

The new generation.

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Combining these features, we provide profitability and total economy for offshore support operations. Our optimized supply vessel concept helps you to achieve the essential.

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Phone: +358 2 83791, Fax: +358 2 8378 4804.

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EXCELLENCE IN PROPULSION www.kamewagroup.com ^ Part of the Propulsion Technology Division of Vickers PLC

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Mounting System Design and

Performance

The ultimate objective of the mounting sys- tem design is to minimize the overboard radi- ated noise attributable to the reduction gear- ing. This is achieved by isolating the reduction gear from the ship foundation. Consider three typical mounting system configurations - hard mounted, metallic isolation and elastomeric isolation. Each of these configurations is shown schematically in Table 2, along with some of their performance comparisons.

The mounting system selection must consid- er the following:

Ship mission requirements; Performance comparison trade-offs; and level of isolation needed to satisfy the system noise performance (determined from noise performance evalua- tions).

System noise performance evaluations should be conducted throughout the reduction gear design phase to ensure that noise perfor- mance requirements are satisfied. (Continued on page 54)

Table 1

Table 1

Typical Propulsion System Noise Sources and Control Approaches

Prime Movers Reduction Gears System Resonance

Sources

Rotationals &

Harmonics • Blade Passing, Fluid

Stream

Crank-Effort

Pulsations

Electrical Tones,

Power Converter,

Pole/Slot Passing

Sources • Shaft Rotationals &

Harmonics • Mesh Tones • Undulation Tones

Sources • Casing & Support

Structures • Shafting System • Isolation System

Control • Dynamic Balance • Rotor / Stator /

Casing Design • Couplings / Bearings • Isolation System - Ship Foundation

Control - Dynamic Balance

Roundness &

Concentricity • Couplings / Bearings • Mesh Design

Manufacturing

Accuracy • Isolation System • Ship Foundation

Control

Resonance

Frequency Tuning • Stimulus Frequency

Avoidance

Component &

System Damping • Isolation System • Ship Foundation

Table 2

Table 2

Mounting System Comparisons

Hard-Mounted Compound Metallic Single Stagtomeric

System Complexity

Low Complexity • Gear Casing Bolted

Directly to Ship

Foundation • No Shock Snubbers ////////

Moderate

Complexity

Several Isolators

Required

Shock

Required

Snubbers

Noise Performance - Foundation Vibration

Higher Complexity

Numerous Mounts

Required

Shock Snubbers

Required

Periodic Mount

Replacement

Higher Overall

Vibration

No Gear-to-

Foundation Isolation • Non-Tunable Design for Given Ship

Foundation

Lower Overall

Vibration • Tunable Design —

Can Optimize to

Foundation and Ship

Mission

Significant

Attenuation Above

Isolator Resonances (Limited by High

Frequency Modes)

Lowest Overall

Vibration • Non-Tunable Design - Standard Application

Mounting Frequency

Significant

Attenuation Above

Mounting Frequency (Limited by High

Frequency Wave

Modes)

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