Marine Engineering Study Materials

 What are the types of telemotor system in steering gear on ships ?

1. Hydraulic system
2. Electric system

 What are the types of steering system ?

•  Electro hydraulic system 

a) Ram type system (2 ram or 4 ram)

b) Vane type system

• All electric system

                a) Ward Leonard system

b) Single motor system

What is meant be non follow up system in steering gear ?

• When steering gear set to required position, rudder is moved & when rudder reach the required position, steering gear must be set to off position. This system uses the three solenoid valve.

What is meant be follow up system in steering gear ?

• When steering gear set to required position, rudder is moved & when rudder reaches the set position, steering gear still remains at that position. This system uses the hunting gear arrangement.

What is hunting gear ?

• It is a feed back mechanism of steering gear which repositions the floating lever of hydraulic pump as the tiller moves to the desire position.

What are the safety devices for steering system ?

1. Hunting gear
2. Buffer spring
3. Angle adjusting stop (Hand over position limit switch)
4. Double shock valve
5. Relief valve
6. Tank level alarm (oil)
7. Over load alarm

What is the indication of air in the steering system ?

• Jumping pressure gauges
• Jerky operation 
• Defective steering

What is the effect of air in the steering system ?

• Air being compressible gives incorrect balance between units, time lags and irregular operation. ( which can be dangerous )

Emergency steering gear operation?

• In the case of Telemotor failure, by switching the change over pin, emergency steering can be carried out by isolating the receiver cylinder and directly controlling the connecting rod of the main steering power unit’s pump lever.
• The emergency rudder angel indicator and communication system to bridge being provided at the emergency station.

Action in case of electrical telemotor failure ?

• Put bridge control to manual 
• Emergency steering gear system is operated by (solenoid button) whether port or starboard.
• Rudder angle indicator and communication system between steering room and bridge must be provided.

 How to operate emergency steering gear ?

1. Disconnect auto pilot system.
2. Take out change over pin from attachment with telemotor receiver & fit to the hand gear.
3. Use communication system with telephone from steering gear room to bridge.

What are steering gear tests & maintenance ?

Control test

• Just prior to 1 hour before departure of vessel.

12 hour before departure

• Operation of main & auxiliary steering gear.
• Operation of remote control system.
• Operation of emergency power supply.
• Alarm test.
• Actual rudder angle & indicator.
• Communication system.(Bridge, Engine room & Steering gear room)

Every 3 months interval

• Emergency steering gear drill at steering gear room to bridge with sound communication system.

Types of pump used in hydraulic steering system ?

• Motor driven constant speed variable stroke delivery pumps. There are two types.

1. Radial piston type ( hele- shaw pump )
2. Axial piston type ( swash plate pump )

What are the advantages of rotary vane type over ram type ?

• Smaller space required
• Low installation cost
• Less weight
• Smaller power required, for the same load, because it can transmit pure torque to the rudder stock.

What are the disadvantages of rotary vane type over ram type ?

• Synthetic rubber backed steel sealing strips at vane tops are not strong enough for large ship gear.
• Can be used for rudder stock ratings of about 1700 KNm and less torque generated by two ram is 120 to 160 KNm and for four ram 250 to 10,000KNm.

Steering tests required before departure ?

1. Steering gear should be checked at least one hour prior to departure.
2. Telemotor transmitter oil level to be checked
3. Oil level of actuating system tank should be checked and replenished if necessary.
4. Rudder carrier bearing and bottom sea gland checked and greased.
5. Start pump and check response of the gear
6. Check abnormal noise and heat 
7. Check load carrying and running of the gear  ( swing from port 35° to stbd 30° within 28 sec )

What are the properties of telemotor hydraulic fluid ?

• Good quality mineral lubricating oil is used. Its properties are-

1. Low pour point (-50°C)
2. Low viscosity ( to reduced fractional drag, but not too thin to mate gland sealing, 30 Redwood Secs at 60°C)
3. High viscosity index (110)
4. High flash point (150° C closed)
5. Non sludge forming
6. Non corrosive 
7. Good lubricating properties  
8. Specific gravity 0.88 at 15.5° C

What is the purpose of buffer spring ?

• To prevent the damages of the control system.

What are the requirements for steering gear ?

• To move the rudder in either direction instantly when required
• Should come to reset immediately in the position corresponding to that shown on indicator on the bridge.
• Provision must be made to protect the steering gear from damage should a heavy sea strike the rudder.
• The design should be sample, the construction robust and its performance reliable at all times.

Purpose of swivel block in steering gear ?

• To control linear movement of the rams to the rotary movement to the tiller arms and rudder stocks.

Explain ward leonard system ?

• It is the one types of electrical steering gear system. Which control the speed of DC motor from zero to maximum in either directions.

In four rams type steering gear system, what unit you make in service when one cylinder damage  ?

• If one cylinder damage, four rams steering gear can be used as two rams type steering gear.
• First place the rudder at mid position.
• Isolate the circuit valves of two cylinder inlet.
• One cylinder is defective and another one, but they are not in diagonal position. Open the vent at that cylinder.

Purpose of buffer spring ?

• Absorb the difference between the steering order speeds and follow up speed.
• Absorb the movement of steering wheel if it is mishandled when the hydraulic pump stop in.
• Absorb the movement of the control lever when rudder drift
• Absorb the vibration and shocks from the rudder.

When carry out emergency steering system ?

• Every voyage (UHA)
• Once at least within 3 Months (SOLAS)
• During Survey

What are daily check in steering gear room ?

• Pressure gauge of steering pump.
• Motor ampere on the steering switch board & motor hand touch feeling
• Noise and vibration.
• Oil level in tank
• Oil leakage in system
• Grease in rudder carrier bearing
• Check the bottom seal gland whether good or not.

What are steering system regulations ?

1. Every ship shall be provided with a main steering gear and an auxiliary steering gear.
2. The failure of one of them will not render the other one inoperative.
3. Relief valves shall be fitted to any part of the hydraulic system.
4. The main steering gear and rudder stock shall be:
5. (a) of adequate strength and capable of steering the ship at maximum ahead service speed. (b) capable of putting the rudder over from 35′ on one side to 35′ on the other side with the ship at its deepest sea going draught and running ahead at maximum ahead service speed and, under the same conditions, from 35′ on either side to 30′ on the other side in not more than 28 seconds. (c) So that they will not be damaged at maximum astern speed.
6. The auxiliary steering gear shall be: (a) of adequate strength and capable of steering the ship at navigable speed and of being brought speedily into action in an emergency. (b) capable of putting the redder over from 15′ on one side to 15′ on the other side in not more than 60 seconds with the ship at its deepest seagoing draught and running ahead at one half of the maximum ahead service speed or 7 knots, whichever is the greater.
7. In every tanker, chemical tanker or gas carrier of 10,000 gross ton and upwards and in every ships of 70,000 gross ton and upwards, the main steering gear shall comprise two or more identical power units.

Reference:

Oral Guide by – MIN ZAR TAR