2_Actuator Working Principles

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Marine Auxiliary

MachineryChapter 8 Lesson 2

Actuator Working Principles

By Professor Zhao Zai Li

05.2006


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The working principles of the standard

model of the rotary vane actuator

The working principles of the RAM model

actuator

Learning objectives


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Basically there are two

types of electro

hydraulic steering gearworking principals:

The ram (or cylinder)

type and the rotaryvane type.

Ram Actuator


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Ram Actuator1 The working principles

of the two are verysimilar. A strong slow

movement of amechanical surface iscreated by the use ofhigh oil pressure.

Ram type uses cylinder

pistons Rotary vane uses

pressure working on theside of a vane (or wing)


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Ram Actuator2 On the ram type the

piston is connected by

a ram (or rod ) to a

tiller, and the tiller is

fixed connected to the

rudder stock, creating

the rotating movement.

On the rotary vane thevane is fixed to a boss

(hub) that is fixed

directly to the stock.


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Ram Actuator3 The principles as described for

the Porsgrunn rotary vane

steering gear can easily bi

transformed to the ram type.

Typical for ram type steering

gears is that they work with a

much higher hydraulic pressure,

they need an external rudderstock bearing and the working

angle is limited, compared with

the rotary vane steering gear.


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Standard Model

The standard model is used on:

All vessels except tankers with single

rudder installation above

100,000DWT

Safety:

Safety against single failure on the

hydraulic system, according toSOLAS rules.


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Working principle of thestandard model1

We will now show you a schematic

drawing of the steering gear.

The model shows a normal operation

situation, with one pump running. Using

both pumps will double the speed of the

rudder.


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Working principle of thestandard model2


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Assessment Test

Question 1 of 5

When shall both power units be in use?

A) All the time

B) When navigation demand special caution

C) When the ship is less than four nautical miles fromshore

D) I dont know


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Assessment Test

Question 2 of 5

What is the limit in size for tankers to use only

one standard steering gear?

A) 10,000GT (gross tonnage)

B) 100,000DWT(deadweight tons)

C) 100,000NT (net tonnage) D) I dont know


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Assessment Test

Question 3 of 5

What is the purpose of the safety valve?. A) To protect against leakage between the pressure

chambers

B) To protect the actuator against too high oil

pressure.

C) To protect the vanes from breaking

D) I dont know


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Assessment Test

Question 4 of 5

One of the statements below is not correct, which

one? A) Both rotary vane and ram steering gears are of electro

hydraulic type.

B) The ram type must have a separate external rudderstock upper bearing. This is not necessary for a rotaryvane type

C) The ram type steering gears generally work with alower oil pressure than a rotary vane

D)I dont know


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Assessment Test

Question 5 of 5

How is the movement of the actuator created? A) By starting the motors on both power units

B) By actuating the direction valve and the safety

C) Start at least one power unit and actuate the direction

valve D) I dont know

2_Actuator Working Principles

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