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
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