Part 1 Steering Gear

University of Stratchclyde Faculty of Engineering Department p of Naval Architecture and Marine Engineering g g

Marine Engineering I Part 1: Steering Gear Course no.: NM 315

Hossein Ghaemi Sem. I, 2010/11

Contents

PART ONE g Gear Steering PART TWO Auxiliary Power Machinery PART THREE Deck Machinery PART FOUR Roll Stabilzers Part 1: Steering Gear

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References „

Lewis E. V. (ed. by), Principles of Naval Architecture, Second Revision, Volume III, Motions in Waves and Controllability, SNAME, 1989.

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Morgan N. (ed. by), Marine Technology Reference Book, Butterworths, 1990, ISBN 0 0-408-02784-3. 408 02784 3.

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Smith D. W., Marine Auxiliary Machinery, 6th Edition, Butterworths, 2005, ISBN 0 0-408-01123-x 408 01123 x

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Taylor, D.A., Introduction to Marine Engineering, Revised 2nd Edition, Elsevier Butterworths-Heinemann, Butterworths-Heinemann 2003 2003, ISBN 07506 25309 25309.

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Shaft Generators for the MC and ME Engines, MAN-B&W Diesel A/S, Copenhagen 2010 Copenhagen, 2010. Part 1: Steering Gear

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Contents

1.1. Requirements 1.2. Control Unit 1.3. Power Units 1 3 1 Ram Type 1.3.1. 1.3.2. Rotary Vane Type 1 3 3 Actuator Type 1.3.3. 1 4 Calculation 1.4. C l l ti off Steering St i Gear G Torque T

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Role and Elements

Control equipment „ Power unit „ Transmission to the rudder stock „

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Types „ „ „

Ram type R t Rotary vane type t Actuator steering gear

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

Ships must h Shi have a main i and d an auxiliary ili steering i 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 speed, d and d att th the ship’s hi ’ d deepestt service i d draught, ht off putting tti 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 15° on one side to 15 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 maximum i service i speed d or 7 kknots. t Part 1: Steering Gear

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Requirements – cont. 4.

It must be possible to bring into operation main and auxiliary steering gear power units from the navigating bridge 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, where the main steering gear comprised two or more identical power units there must be two independent control systems both operable from the bridge bridge.

6.

Tankers, chemical carriers and gas carriers of 10 000 GT or 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 etc.), ) or seizure of the rudder actuators, must be regained in not more than 45 seconds. Part 1: Steering Gear

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Control Unit

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 p pressure Part 1: Steering Gear

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Control Unit – cd. Q1 (t ) = Q2 (t ) Q (t ) = APS ⋅ y& (t ) Q (t ) = α ⋅ A(t ) ⋅

2

ρ

⋅ Δp

Δp = pup − plow

p0 p1 (t ) = p2 (t ) = 2 ⎛ α ⋅π ⋅ b y& (t ) = ⎜⎜ ⋅ ⎝ APS Part 1: Steering Gear

p0 ⎞ ⎟ ⋅ x (t ) = K S ⋅ x (t ) ρ ⎟⎠ 11

Y ( s) K S GS ( s ) = = X ( s) s Marine Engineering I

Control Unit

(cont.)

Conventional:

deg & deg < δ max < 7 2.3 s s

Based on Rules

δ&

Newlyy built fast hips: p Part 1: Steering Gear

min

v = 132,9 L

deg s

& < 20 deg 15 deg < δ max s s 12

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Ram Type 1. Two-ram 2. Four-ram

Arm forks

Arms

Swivel crosshead h d

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

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Arm forks

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Variable displacement pumps

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Part 1: Steering Gear

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Safety control „

A bypass valve is combined with spring-loaded shock valves which open in the event of a very heavy sea forcing the rudder over.

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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

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A spring-loaded return linkage on the tiller will prevent damage to the control gear during a shock movement

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Operational aspects „

Moving g the floating g ring g or slipper pp p pad of the p pump, p causes a p pumping p g action. Fluid will be drawn from one cylinder and pumped to the other, thus turning the tiller and the rudder.

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During normal operation one pump will be running. 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. transmitter

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A return linkage or hunting gear mounted on the tiller will reposition the floating lever so that no pumping occurs when the required rudder angle l iis reached. h d

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During normal operation the steering gear should be made to move at east o once ce e every e y ttwo o hours ou s to e ensure su e se self lubrication ub cat o o of tthe e moving o g least parts.

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No valves in the system, except bypass and air vent, should be closed.

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The replenishing tank level should be regularly checked and, if low, refilled and the source of leakage found.

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In port, port the steering motors should be switched off off. Part 1: Steering Gear

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Rotary Vane Type „ „ „

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A vaned rotor is fastened onto the rudder stock 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 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 chambers on the right, the rudder stock can be made to turn CCW. Three vanes are usual and permit an angular movement off 70°: 70° the th vanes also l actt as stops t li iti rudder limiting dd movement. The hydraulic fluid is supplied by a variable delivery pump and control will be electrical electrical. A relief valve is fitted in the system to prevent overpressure and allow for shock loading of the rudder.

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Vane-type steering gear. (Red indicates pressurised oil.Green indicates excess oil.) Part 1: Steering Gear

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Steering gear room Part 1: Steering Gear

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Steering Gear

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Actuator Type

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The gear is made redundant on one rudder by means of two actuator systems. systems Cost-effective and reliable solution. F Fewer i t f interface surfaces f on board b db because th the actuator's anchor brackets can be welded directly on to the hull cartridge cartridge. This means that actuator steering gear is less tolerance-critical for installation. Part 1: Steering Gear

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Capacity Comparison

„Brown Brothers – Rolls Royce” Production Part 1: Steering Gear

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Part 1: Steering Gear

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Part 1: Steering Gear

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Calculation of Steering Gear Torque

ƒ homogeneous h flflow ƒ α: angle of attack ƒ s: span width (s>>c) ƒ Ar : projected rudder area ƒ V: constant velocity of fluid far before the rudder 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), - decomposed in: normal force N and a tangential force T Part 1: Steering Gear

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Rudder forces are made dimensionless by the stagnation pressure 1 ρV 2 2 and the projected area A : r

L CL = 1 2 ρ V Ar 2

N CN = 1 2 ρ V Ar 2

D CD = 1 2 ρ V Ar 2

T CT = 1 2 ρ V Ar 2

P = L2 + D 2 = N 2 + T 2 i α ⎧ N = L cos α + D sin ⎨ ⎩C N = C L cos α + C D sin α

⎧T = D cos α − L sin α ⎨ ⎩CT = C D cos α − C L sin α Part 1: Steering Gear

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Ar : projected rudder area: 2 ⎡ ⎛ B ⎞ Dr ⋅ L pp ⎟ ⎢1 + 25 ⋅ ⎜ Ar = ⎜L ⎟ 100 ⎢ ⎝ pp ⎠ ⎣

⎤ ⎥ ⎥ ⎦

Dr : draft Lpp : 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 any other For th rudder dd arrangementt an increase i iin th the rudder dd area b by - at least – 30% is required.

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Me: Moment about the front (or nose) of the rudder

CM e

Me = 1 2 ρ V Ar ⋅ c 2

CM e

N ⋅e e = 1 = CN ⋅ 2 c 2 ρV Ar ⋅ c

Me = N ⋅e

N CN = 1 2 ρ V Ar 2

e CMe = c CN Part 1: Steering Gear

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Mrs: Moment about the rudder stock

M rs = N ⋅ ( e − a )

Geometrical aspect ratio

Part 1: Steering Gear

s AR = c Ar c= s

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s2 AR = Ar

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The lift, drag and moment coefficients (CL, CD and CM) of symmetrical NACA (National Advisory Committee for Aeronautics) wing sections for 0.06 ≤ t ≤ 0.18

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V i ti off lift Variation lift, d drag and d momentt coefficients ffi i t 1.4 CL CD CM

12 1.2

Coe efficients

1

0.8

0.6

0.4

0.2

0

0

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10

15 20 Angle of attack, deg.

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25

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