Marine Auxiliary Machinery

Chapter 8 Lesson 3

Actuator Main Parts

Learning objectives

Identify and understand the function of the main parts of the actuator: Housing Rotor Stoppers Cover Radial bearing Rudder carrier

Actuator basics

The actuator is situated on top of the rudder stock in the steering gear compartment. The rotor in the rotary vane actuator is mounted directly on the rudder stock.

The rudder stock connects the actuator with the rudder.

The Actuator (1)

Rudderstock Bearings

The Actuator (2)

Actuator housing Actuator complete

Actuator Main Parts

1.Angel indicator

This is fixed to the rudderstock and shows the rudder angel.

2. Expansion tank

This tank serves as an expansion tank for the system oil.

3. Rudder stock nut

This nut acts as a securing device for the friction connection between the rudderstock and the rotor.

4.Stoppers bolt nut

Making boundaries for the pressure chambers and also sets the limits for the rudder angle to each side.

5. Upper radial bearing

The upper radial bearing takes up radial forces in conjunction with lower radial bearing .It is made of brass . This bearing is lubricated by the system oil .

6. Rotor hub

This is the moving part of the actuator . It turns the rudderstock when the hydraulic pressure increases on either side of its vanes. It is fitted with spring loaded cast iron bars (dynamic seals). These are not exposed to wear.

7. Housing

Serves as the outer boundaries, side and bottom of the pressure chambers .

8. Rudder stock

This is the connecting shaft between the rotor and the rudder.

9. Lower Radial bearing

The lower radial bearing takes up radial forces in conjunction with upper radial bearing. It is made of brass. This bearing is lubricated by the system oil.

10. Rudder carrier

This bearing carries the weight of the moving parts of the steering gear including the rudder. It also takes up the axial forces that waves and propellers can make. This bearing is made of brass. This bearing is lubricated by the system oil.

11. Lower packing

This keeps the system oil from leaking down the rudderstock oil has lubricated the lower side bearing and the rudder carrier.

12. Ring jack

This is used during installation, to force the rotor onto the rudder stock.

13. Cover

The cover forms the top of the pressure chambers.

Assessment Test

Question 1 of 4

What are the bearing made of ? A) Steel B) Copper C) Brass D) I don’t know

Assessment Test

Question 2 of 4 What is the main purpose of the housing. stoppers

and cover? A) Making boundaries for the pressure chambers. B) Protecting the rotor. C) Interfacing between the steering system and the ships

hull structure. D) I don’t know

Assessment Test

Question 3 of 4 How is the rotor fixed to the rudderstock?

A). By two keys. B). Combination of one key and friction. C). By friction only. D).I don’t know

Assessment Test

Question 4 of 4 What are the bearings lubricated with?

A) Grease B) Separate oil system C) The system oil D).I don’t know