Rudders turn a ship as and when required. Rudders are the principal system for the motion and control of the vessel. But we must remember that the rudder action is dependent on another pivotal system called the Steering Gear.
Steering Gear integrated with the rudder system defines the ‘turning mechanism’ for every ship irrespective of size, type and operation.
ATZ with our partner Aegir Marine have the parts, service and experience to overhaul many Steering Gear types.

Steering Gear

There are certain requirements that must be met by steering gear. These basic requirements to be invariably met by all steering gears are guided by rules set out by classification societies. They can be briefly defined as:

  • The steering gear should be capable of steering the ship from 35 degrees port to 35 degrees starboard and vice-versa with the vessel in forward motion at a steady head-on speed for maximum continuous rated shaft rpm. This should be at summer load waterline within a time frame of a maximum of 28 seconds.
  • With one of the power units inoperative, the rudder shall be capable of turning 15 degrees port to 15 degrees starboard (and vice-versa) within a time frame of a maximum of 60 seconds with the vessel moving at half its rated maximum speed, or 7 knots (whichever is greater). This should be at summer load waterline.
  • The major power units and the control systems are to be duplicated. This is so that if one of them fails, the substitute can be used as a standby.
  • The steering gear system is to be provided with an additional power unit (hydraulic pump etc.) connected to the emergency power supply from the Emergency Generator, which shall be capable of turning the rudder from 15 degrees from one side to other side within a maximum of 60 seconds with the vessel moving at a maximum service speed or 7 knots, whichever is greater.

Steering Operations

The main control of the steering operations is given from the helm of the ship. The ‘control force’ for turning is triggered from the wheel at the helm, which reaches the steering gear system. The steering gear system then generates a torsional force which is then, in turn, transmitted to the rudder stock that turns the rudder.

The rudder system generally consists of the following pieces of equipment

  • The rudder actuators
  • Hydraulic power units, usually one per rudder steering gear
  • Hydraulic pumps and valves, normally this equipment is doubled up for redundancy.
  • Other auxiliary equipment needed to apply turn the rudder by applying torque

Maintenance Requirements

Different steering gear types have different maintenance requirements but the typical planned maintenance for a rotary vane type arrangement would be:

Five-year maintenance (often described as a minor overhaul):

  • Removal of rotary vane cover for inspection
  • Replacement of internal seals
  • Replacement of internal and upper gland seals
  • Renewal of hydraulic oil
  • Power pack filter replacement
  • Pump shaft seals and flexible couplings
  • Checking and calibration of control system and rudder positioning

10-year maintenance (often described as a major overhaul)

  • All the items normally carried out during a 5-year maintenance
  • Liners
  • Thrust Bearings
  • O ring for the hydraulic nut
  • Pressure valves
  • Seal kit for the valves

ATZ with our partner Aegir Marine have extensive experience with most steering gear types are in position to meet your parts and service needs. 


FAQ’s

Can the steering gear system be repaired whilst afloat?

Yes, the equipment can be accessed from the steering gear machinery space inside the vessel. Consideration must be given to the its connection to the rudder itself and make sure that the rudder rotation is in control

I have excessive noise from my steering gear, what could it be?

Excessive noise and vibrations from the steering gear may indicate entrapment of air in the system. Due to the air bubbles in the oil, pumps and pipework are subjected to air hammer leading to vibration and noise. 

The Rudders are moving within or beyond the limit, what could be wrong?

SOLAS states that the system must be capable of 35 degrees on one side to 35 degrees on the other side, at its deepest seagoing draught and running at maximum ahead service speed. It may happen that the maximum angle reached by the rudder is less or the rudder is overshooting the 35-degree angle limit.

One of the main reasons for this problem is a malfunction of the limit switch fitted on the repeat back unit or on the auto pilot. Replace the malfunctioned limit switch or adjust the limit switch to the correct maximum rudder angle limit.

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