Part 1 Steering Gear

University of Stratchclyde Faculty of Engineering

Department of Naval Architecture and Marine Engineeringp g g

Marine Engineering I

Marine Engineering I

Marine Engineering I

Marine Engineering I

Part 1: Steering Gear

Course no.: NM 315

Contents

PART ONE

PART ONE

Steering Gear

g

PART TWO

PART TWO

PART TWO

PART TWO

Auxiliary Power Machinery

PART THREE

PART THREE

Deck Machinery

PART FOUR

PART FOUR

Roll Stabilzers

Roll Stabilzers

References

„ Lewis E. V. (ed. by), Principles of Naval Architecture, Second Revision,

Volume III, Motions in Waves and Controllability, SNAME, 1989. Volume III, Motions in Waves and Controllability, SNAME, 1989.

„ Morgan N. (ed. by), Marine Technology Reference Book, Butterworths,

1990, ISBN 0-408-02784-3. 1990, ISBN 0 408 02784 3.

„ Smith D. W., Marine Auxiliary Machinery, 6th Edition, Butterworths, 2005,

ISBN 0-408-01123-x ISBN 0 408 01123 x

„ Taylor, D.A., Introduction to Marine Engineering, Revised 2nd Edition,

Elsevier Butterworths-Heinemann 2003 ISBN 07506 25309 Elsevier Butterworths-Heinemann, 2003, ISBN 07506 25309.

„ Shaft Generators for the MC and ME Engines, MAN-B&W Diesel A/S,

Copenhagen 2010 Copenhagen, 2010.

Contents

1.1. Requirements

1.2. Control Unit

1.3. Power Units

1 3 1 Ram Type

1.3.1. Ram Type

1.3.2. Rotary Vane Type

1 3 3 Actuator Type

1.3.3. Actuator Type

1 4 C l

l ti

f St

i

G

T

Role and Elements

„

Control equipment

„

Power unit

„

Power unit

Types

„

Ram type

R t

t

„

Rotary vane type

Requirements

Shi

h

i

d

ili

i

International Convention for the Safety of Life at Sea (SOLAS), 1974 1.

Ships must have a main

and an auxiliary steering gear,

arranged so that the failure of one does not render the other

inoperative.

p

2.

The main

steering gear must be able to steer the ship at

maximum ahead service speed and be capable at this

d

d t th

hi ’ d

t

i

d

ht

f

tti

speed, and at the ship’s deepest service draught, of putting

the rudder from 35°

on one side to 30°

on the other side in

not more than 28 seconds.

3.

The auxiliary

steering gear must be capable of being

brought speedily into operation and be able to put the rudder

over from

15°

on one side to

15°

on the other side in not

over from 15

on one side to 15

on the other side in not

more than 60 seconds

with the ship at its deepest service

draught and running ahead at the greater of one half of the

i

i

d

7 k t

Requirements – cont.

4.

It must be possible to bring into operation main and auxiliary

steering gear power units

from the navigating bridge

steering gear power units from the navigating bridge.

5.

Steering gear control

must be provided both

on the bridge

and in the

steering gear room

for the main steering gear and

and in the steering gear room

for the main steering gear and,

where the main steering gear comprised two or more

identical power units there must be two independent control

systems both operable from the bridge

systems both operable from the bridge.

6.

Tankers, chemical carriers and gas carriers of 10 000 GT or

over require two or more identical power units

and the

over require two or more identical power units

and the

steering gear must be arranged so that loss of steering

capability due to a single failure in one of the power actuating

systems of the main steering gear (excluding tiller etc ) or

systems of the main steering gear (excluding tiller etc.), or

seizure of the rudder actuators, must be regained in not more

than 45 seconds.

Control Unit

Reaction of servo (and as a result reaction of rudder) depends on the: Reaction of servo (and as a result reaction of rudder) depends on the: 1. Dimensions of the servo (so-called step-volume),

2. Cross sectional area of connecting pipes between cut-off slider and servo 3. Feed oil pressurep

Control Unit – cd.

)

(

)

(

t

Q

t

Q

=

)

(

)

(

t

A

y

t

Q

=

⋅

&

p

t

A

t

Q

=

⋅

⋅

⋅

Δ

ρ

α

(

)

2

)

(

p

p

p

=

−

Δ

2

)

(

)

(

p

t

p

t

p

=

=

)

(

)

(

)

(

p

x

t

K

x

t

A

b

t

y

_⎟⎟

⋅

=

⋅

⎠

⎞

⎜⎜

⎝

⎛

⋅

⋅

⋅

=

ρ

π

α

&

s

K

s

X

s

Y

s

G

=

=

)

(

)

(

)

(

A

⎟

_⎠

⎜

⎝

ρ

X

(

s

)

s

Control Unit

(cont.)

s

s

deg

7

deg

3

.

2

<

δ

&

<

s

s

v

deg

9

,

132

=

δ

&

s

L

,

20

15

<

δ

&

<

Newly built fast hips:

s max

s

20

15

<

δ

<

Ram Type

1. Two-ram

2. Four-ram

forks

Arms

Tiller: a lever attached to Swivel _{h d}

Tiller: a lever attached to a rudder stock in order to provide the leverage to turn the rudder

„

A

bypass valve

is combined with

spring-loaded shock valves

which

open in the event of a very heavy sea forcing the rudder over.

Safety control

open in the event of a very heavy sea forcing the rudder over.

„

In moving over, the

pump is actuated

and the steering gear will

return the rudder to its original position once the heavy sea has

passed

passed.

„

A

spring-loaded return linkage on the tiller

will prevent damage to the

„

Moving the floating ring or slipper pad of the pump, causes a pumping

Operational aspects

g

g

g

pp

p

p

p

p

p g

action. Fluid will be drawn

from one cylinder and pumped to the other

,

thus turning the tiller and the rudder.

„

During

normal

operation

one pump

will be running If a faster response

During

normal

operation

one pump

will be running. If a faster response

is required, for instance in confined waters, both pumps may be in use.

The pumps will be in the no-delivery state until a rudder movement is

required by a

signal

from the bridge telemotor transmitter

required by a

signal

from the bridge telemotor transmitter.

„

A

return linkage

or hunting gear mounted on the tiller will reposition the

floating lever so that no pumping occurs when the required rudder

l i

h d

angle is reached.

„

During normal operation the steering gear should be made to move at

least

east

once every two hours

o ce e e y t o ou s

to ensure self lubrication of the moving

to e su e se ub cat o o t e o

g

parts.

„

No

valves

in the system, except bypass and air vent, should be closed.

The

replenishing tank level

should be regularly checked and, if low,

refilled and the source of leakage found.

„

In

port

the steering motors should be switched off

In

port

, the steering motors should be switched off.

Rotary Vane Type

„ A vaned rotor is fastened onto the rudder stock „ A vaned rotor is fastened onto the rudder stock.

„ The rotor is able to move in a housing which is solidly

attached to the ship's structure.

„ Chambers are formed between the vanes on the rotor „ Chambers are formed between the vanes on the rotor

and the vanes in the housing. These chambers will vary in size as the rotor moves and can be pressurized since sealing strips are fitted on the moving faces.

„ The chambers either side of the moving vane are

connected to separate pipe systems or manifolds. Thus by supplying hydraulic fluid to all the chambers to the left of the moving vane and drawing fluid from all the

of the moving vane and drawing fluid from all the

chambers on the right, the rudder stock can be made to turn CCW.

„ Three vanes are usual and permit an angular movement

f 70° th l t t li iti dd

of 70°: the vanes also act as stops limiting rudder movement.

„ The hydraulic fluid is supplied by a variable delivery pump and control will be electrical

pump and control will be electrical.

„ A relief valve is fitted in the system to prevent

Vane-type steering gear.

Actuator Type

„

The gear is made redundant on one rudder by

means of

two actuator systems

means of

two actuator systems

.

„

Cost-effective

and reliable solution.

F

i t f

f

b

d b

th

„

Fewer interface surfaces

on board because the

actuator's anchor brackets can be welded

directly on to the hull cartridge This means that

directly on to the hull cartridge. This means that

actuator steering gear is less tolerance-critical

for installation.

Capacity Comparison

Calculation of Steering Gear Torque

h fl

ƒ homogeneous flow

ƒ α: angle of attack

ƒ s: span width (s>>c)

ƒ A : projected rudder area

ƒ A_r: projected rudder area

ƒ V: constant velocity of fluid far before the rudder

ƒ L: lift force (perpendicular to the flow)

ƒ L: lift force (perpendicular to the flow)

ƒ D: drag force (in the direction of the flow)

ƒ P: total force (acts at about e~ 0.25c),

Rudder forces are made dimensionless by the stagnation pressure

and the projected area

:

2 2

1

ρ

_V

A

and the projected area

:

L

L

C

=

_C

=

N

A

D

C

A

V

ρ

T

C

A

V

C

ρ

=

A

V

C

ρ

=

A

V

C

ρ

=

T

N

D

L

P

=

+

=

+

⎧

N

L

D

i

⎩

⎨

⎧

+

=

+

=

α

α

α

α

sin

cos

sin

cos

C

C

C

D

L

N

⎨

⎧

T

=

D

cos

α

−

L

sin

α

⎩

⎨

₌

_α

₋

_α

sin

cos

C

C

C

⎤

⎡

_⎛

_⎞

A

: projected rudder area:

⎥

⎥

⎦

⎤

⎢

⎢

⎣

⎡

⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛

⋅

+

⋅

=

25

1

100

L

B

L

Dr

A

⎥⎦

⎢⎣

⎝

⎠

100

L

L_pp : ship’s length between perpendiculars B : beam

„

This can be applied only to rudder arrangements in which the rudder

is located directly behind the propeller.

F

th

dd

t

i

i th

dd

b

„

For any other rudder arrangement an increase in the rudder area by

e

N

M

_e

=

⋅

M

:

about the front (or nose) of the rudder

e

M

c

A

V

M

C

=

⋅

ρ

c

e

C

c

A

V

e

N

C

=

⋅

⋅

=

ρ

_V

_A

_c

_c

⋅

ρ

N

C

C

A

V

C

ρ

=

C

C

c

e

₌

M

: Moment about the rudder stock

)

(

e

a

N

M

_rs

=

⋅

−

c

s

AR

=

Geometrical aspect ratio

c

s

A

c

=

A

s

AR

=

s

A

The lift, drag and moment coefficients (C_L, C_D and C_M) of symmetrical NACA (National Advisory Committee for Aeronautics) wing sections for 0.06 ≤ t ≤ 0.18

V i ti f lift d d t ffi i t

1 2 1.4

Variation of lift, drag and moment coefficients

CL CD 1 1.2 CM 0.8 effi ci en ts 0.4 0.6 Co e 0.2 0 5 10 15 20 25 30 0