Steering Gear is equipment provided on ships to change the direction of the ship during sailing or maneuvering. The Steering Gear works only when the ship is in motion and, does not work when the ship is stationary.
What are the different types of Steering Gear systems?
- Elector hydraulic system
- Ram type system (2 ram or 4 ram)
- Rotary Vane type system
- All electric system
- Ward Leonard system
- Single motor system
What is Non follow up system?
When steering gear is set to the required position, the rudder is moved & when the rudder reaches the required position, the steering gear must be set to the off position. This system uses three solenoid valves.
What is Follow up system?
When steering gear is set to the required position, the rudder is moved & when the rudder reaches the set position, the steering gear still remains at that position. This system uses the hunting gear arrangement.
What is a hunting gear mechanism?
The hunting gear mechanism is a feedback mechanism of steering gear that repositions the floating lever of the hydraulic pump as the tiller moves to the desired position.
What are the Safety devices for the steering gear system?
- Hunting gear
- Buffer spring
- Angle adjusting stop (Hand over position limit switch)
- Double shock valve
- Relief valve
- Tank level alarm (oil)
- Over load alarm
What are the Indications of air in the steering gear system?
- Jumping pressure gauges
- Jerky operation
- Defective steering
What are the types of pumps used in hydraulic steering systems?
Motor-driven constant speed variable stroke delivery pumps. There are two types.
- Radial piston type (hele-shaw pump)
- Axial piston type (swash plate pump)
- Radial piston pump:-The variable stroke pump having radial piston is driven by a constant speed electric motor. Its output is controlled by a simple push pull rod attached to the floating ring in the pump. Without stopping the pump the output can be moved from zero to maximum delivery in both directions. The fluid pressure increases without any shock load on pipeline
- Axial piston pump:-The axial piston pump is driven by a constant speed electric motor. The rate of delivery and the direction of oil flow are varied by the angular movement of the swash plate. Step less changes of pump delivery from zero to maximum in either direction is achieved through lever or servo controls.
What are the advantages and disadvantages of rotary vane type over ram type?
Advantages:
- Smaller space required
- Law installation cost
- Low in weight
- Smaller power required, for the same load, because it can transmit pure torque to the rudder stock.
Disadvantages
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 K-Nm and less torque generated by two rams is 120 to 160 K-Nm and for four rams 250 to 10,000 K-Nm.
In four rums type steering gear system, what unit do you make in service when one cylinder is damaged?
If one cylinder is damaged, 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 the two-cylinder inlet.
One cylinder is defective and another one, but they are not in a diagonal position. Open the vent at that cylinder.
What are the properties of telemotor hydraulic fluid?
Good quality mineral lubricating oil is used. Its properties are-
- Low pour point (-50°C)
- Low viscosity ( to reduced fractional drag, but not too thin to mate gland sealing, 30 Redwood Secs at 60°C)
- High viscosity index (110)
- High flash point (150°C closed)
- Non sludge forming
- Non corrosive
- Good lubricating properties
- Specific gravity 0.88 at 15.5°C
What are the Maintenance and checks of Steering Gear?
Daily checks
- Lubrication of sliding or moving parts inspection
- Check greasing mechanism for proper functioning.
- Inspect all linkages.
- Inspect seals, connectors, pipelines for leaks
- Oil level checks
- Check temperatures & pressures.
- Check ammeter reading of pump
- Check level of replenishing tanks.
Weekly checks
- Check alarms & emergency changeovers.
- Check bridge to steering room communication on portable devices and sound powered phone.
Monthly checks
- Check & clean hydraulic oil filters or replace
3 Monthly checks
- Try out emergency steering from local control station in steering & log down in logbook.
6 Monthly checks
- Samples of oil for shore analysis.
