Actually, there are two types of steering gear onboard. Such as Ram type steering gear and rotary vane type steering gear. let us discuss one by one.
1) Ram Type Steering Gear Onboard:
This is one of the types of steering gear onboard. The ram-type steering gear will use with considering the requirements of torque. Also, the ram type can again divide into two. Those are 2 Ram and 4 Ram types.
a) 2 Ram Type Steering Gear Onboard:
The ram-type steering gear consists of a hydraulic cylinder, tiller arms and a swivel crosshead. The ram that presents in the hydraulic cylinder activates the tiller arm with the help of the swivel crosshead. There is a delivery pump for each cylinder and always in working condition. Also, a slipper rings with a rod attaching to the spindle of the telemotor receiver. The delivery pump is attached to each cylinder help to pump the hydraulic oil to suction or discharge. For this, a replenishing tank with a non-return valve is there to help the oil pumping process. There is an arrangement with spring-loaded control on the tiller arm. This will help to prevent damage to the gearing system at the time of heavy shock moving.
Normally for the ordinary operation, only one from both will be in running condition. for getting fast movement and response, then we can activate both pumps such as moving through confined water. A telemotor signal from the wheel form the bridge will need to activate the pump or else it would be in no delivery condition. If we activate the signal from the bridge, then the cylinder of the receiver will activate and start moving. This movement will cause the movement of the floating lever. The floating lever movement will cause the movement of the floating ring.
Also, this will activate the pump. After this, the pump will take suction from one cylinder and pump to another cylinder with a force. This change will turn the tiller arm followed by the rudder. The hunting gear arrangement help to reposition the lever without pumping furthermore after the rudder reached the respective angle.
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b) 4 Ram Type Steering Gear Onboard:
The four ram-type steering gear will work as same as the two rams. But the working of the pump is slightly different. In the four ram-type steering gear, the pump will take suction from the two diagonally opposite cylinder and pump to the next opposite cylinder. By using the four ram steering gear, we will get high torque than the two rams. We can use both pumps or we can use the two-port side and two starboard side. For enabling this arrangement, we should open and close some particular valves. The valves used on the four ram steering are the rudder shore relief valve, bypass valve and isolating valves. By closing and opening, this will provide high flexibility for using the four ram steering system.
At the normal time, we need only one pump to operate the rams and if we have an emergency situation we should use both the pumps to control the four ram steering system. As we know there is a crosshead arrangement on the ram of the steering gear known as the Rapson slide. Also, this mechanism will help to provide the perfect movement of the rudder according to the angle.
At the normal working condition, the steering gear should move about 2 times in one hour. This will help with self-lubrication. Except for the bypass valve and the air vent, none of the other valves is supposed to be closed. Also, check the level of the replenishing tank. If it found as low, then top up it with the required amount. When the ship is at the port, the steering system should be in off condition. Also, check the coupling motors to ensure that it moving freely.
2) Rotary Vane type Steering Gear Onboard:
This is one of the types of steering gear onboard. In the rotary vane type steering gear, there is a vaned rotor that will lock to the stock of the rudder. Then the rotor will move freely in a housing. And that housing will be on the ship structure. There is some chamber in between the rotor vane and the vanes in the housing. This chamber will pressurise so that it may change the size. For then, the chamber covered with vanes at both sides is attached to the piping arrangement.
This will operate like supply the fuel at high pressure to the left chambers by taking the suction from the right chamber. This will cause the stock to turn in the anti-clockwise direction. And we can turn the rudder stock in a clockwise direction if the process is reversed. The hydraulic fluid will supply by the pump and it is an electrically controlling system. To prevent overpressure in the system, there is a setup of the relief valve.
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3) Electric Steering System Onboard:
This is one of the types of steering gear onboard. In the electrically operating steering gear, all the main controls will be electrically occupied such as electric power, electric transmission. And the electric steering can divide into two:
1. Ward-Leaonard System.
2. Direct single motor System.
In the ward Leonard system, there is a directly coupled exciter. That will produce sufficient field current for the generator. There is an exciter field and this field is considered as a control circuit part. Also, in some case, the control circuit will directly connect to the field current. And there will not be the exciter at that time. Also at the time, the control system may balance, then the exciter field, exciter output and generator output will not be there and it will be running continuously. Also, the motor that running the rudders not getting the input, thus it will be in static condition.
At the time we turn the wheel, then the contact of the rheostat will move. Then there will be a unbalance in the control system. This will cause the production of the voltage in the exciter, exciter field and also in generator. Because of this voltage, the generator will make the power t operate the rudder motor and this will turn the rudder. While the rudder moves to a position, then it makes the rheostat to move to the old position. This will make the system into a balance condition and stop the flow of current.
Conclusion: So far we were discussing the working and the construction of the different types of steering system onboard ship. Hope you understand everything. Please comment with your opinion and any queries below so that we can make an improvement in the coming articles.
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