The safety of navigation depends to a large extent on the reliable operation of its controls. To ensure works of the steering device, full duplication of the power complex (electric motors, pumps) and the use of other energy sources is practiced. Often, auxiliary steering vehicles of lower power are installed.
In case of failure of the main and spare steering machines, it is possible to shift the steering wheel using tiller hoists.
Thus, the maneuvering of the vessel can be provided by three virtually independent steering machines.
Given the reliability of modern steering machines, it is not necessary to install tiller hoists. The transition to using a spare steering gear should be made as quickly as possible. This usually takes no more than two minutes.
For electric and hydraulic steering machines, spare engines and pumps are installed, and various energy sources are used to power the main and spare sets. So for a hydraulic steering machine, a manual pump is sometimes installed in case of a power source failure.
In the absence of a spare set of engines and pumps for the steering machine, an auxiliary steering drive is provided, which can only have one element in common with the main steering drive, a sector or tiller.
The spare-drive steering machine must ensure that, at a forward speed equal to half the maximum speed (but not less than seven knots), the steering wheel is shifted from twenty degrees for no more than a minute.
Most of the new original steering drives are some kind of hydraulic machine. Most often, they are from the tiller or sector, and the necessary moment is transmitted directly to the shafts, which in this case turns into an element of the hydraulic engine. The advantage of using hydraulic systems in steering devices is that large forces can be transmitted with minimal loss of power. The possibility of creating compact hydraulic systems determines the further wide application of hydraulics in steering devices.
Paddle Steering gear
Consider a vane steering mechanism and a steering drive that uses the principle of a hydraulic joint.
The rotor is fixed to the balloon cone using a key. The cylinder is mounted on a Foundation located on a deck or platform. Fixed blades fixed to the inner surface of the cylinder and blades fixed to the rotor form two groups of chambers in the annular space between the rotor and the cylinder. The chambers of each group are connected by a collector. When the working fluid in one of the groups of chambers, the rotor rotates clockwise and shifts the steering wheel on the left side, and when the liquid flows into another chamber – starboard.
The main advantage of the blade mechanism is simplicity, compactness and low weight. It lacks the tiller and working cylinders required in other hydraulic mechanisms. Therefore, the specific mass of the blade mechanism is much less than that of electric hydraulic plunger steering machines.
Steering gear that uses the principle of a hydraulic joint
When the working fluid is fed into one of the cavities between the housing and the nut, the nut moves along a fixed screw under the influence of liquid pressure, making a rotational movement. The rotational movement of the nut is transmitted to the shafts. The combination of the hydraulic joint with the shafts makes the steering device very compact and allows you to virtually abandon the tiller compartment.