Marine Auxiliary Machinery

1. Marine Auxiliary Machinery Chapter 8 Lesson 2 Actuator Working Principles By Professor Zhao Zai Li 05.2006

2. Learning objectives • The working principles of the standard model of the rotary vane actuator • The working principles of the RAM model actuator

3. Ram Actuator • Basically there are two types of electro hydraulic steering gear working principals: • The ram (or cylinder) type and the rotary vane type.

4. Ram Actuator （1） • The working principles of the two are very similar. A strong slow movement of a mechanical surface is created by the use of high oil pressure. • Ram type uses cylinder pistons • Rotary vane uses pressure working on the side of a vane (or wing)

5. Ram Actuator （2） • 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 the vane is fixed to a boss (hub) that is fixed directly to the stock.

6. Ram Actuator （3） • 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 rudder stock bearing and the working angle is limited, compared with the rotary vane steering gear.

7. 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 to SOLAS rules.

8. Working principle of the standard model （1） • 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.

9. Working principle of the standard model （2）

10. 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 from shore • D) I don’t know

11. 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 don’t know

12. 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 don’t know

13. 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 rudder stock upper bearing. This is not necessary for a rotary vane type • C) The ram type steering gears generally work with a lower oil pressure than a rotary vane • D)I don’t know

14. 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 don’t know