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1 - PRODUCT DESCRIPTION
1.1 Operation of a hydraulic steering system
The hydraulic systems
standards P21.
The steering systems
-18°C (0°F) and +77°C (+170°F), all of their components were specifically manufactured for the marine
environment, using materials and applying processes that offer great durability and safety even in
extreme conditions.
The hydraulic steering system mounted on a
boat schematically consists in:
• a pump placed on the dashboard;
• a cylinder positioned at the stern and
connected to the motor or to the helm;
• pair of connection hydraulic tubes (see
figure).
The rotation of the steering wheel causes
the pumping of the oil that, depending on the
direction of rotation, flows into the cylinder
through the tubes.
The consequent movement of the cylinder makes
the oil flow towards the pump through the tubes
and at the same time moves the engine or the
helm of the boat connected to the cylinder itself.
The pumps are equipped with a non-return
valve, which has the function of preventing the
flow of oil to the pump if the latter is not running. In unbalanced cylinders the two chambers have different
capacities, and therefore require, considering the same displacement in the two directions, a different
number of turns of the steering wheel and a different rotation torque on the steering wheel. The balanced
cylinders require the same number of turns of the steering wheel to move the helm from the centre to the
end of stroke in the two opposite directions.
A balanced and easily manoeuvrable steering system requires a proper choice of the type of pump to be
coupled to the cylinder.
of oil handled at each turn of the steering wheel) and for the type of installation. While choosing the pump
you must consider the capacity of the cylinder: the number of steering wheel turns from left to right is in
fact determined by the ratio between the volume of the cylinder and the pump flow.
Example: if the pump has a flow rate of 18 cm3 [1.2 cu.in.] and the cylinder has a capacity of 81 cm
[5.7cu.in], then the following formula applies: 81/18=4,5. Therefore the steering wheel will rotate about
4 and a half times before the cylinder is completely shifted from side to side. Couplings with less than
4 turns are not recommended as they require excessive driving strength, neither those with more than
8 turns are advisable as they make the board slow in responding to the steering gear. The maximum
operating pressure is equal to 5,5MPa (55 bars) (800 psi).
8
page
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CYLINDRE HYDRAULIQUE POUR MOTEUR HORS BORD
are designed in accordance with UNI EN ISO 10592 rule and A.B.Y.C.
are able to operate in an ambient temperature ranging between
pump
builds different models of pumps, which differ for the flow rate (cm3
Installation and Maintenance Manual
motor
cylinder
hydraulic tubes
example of application
3
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