As a result of studying this section you will learn the working principles of the
standard model of the rotary vane actuator to working principles of the
IMO model of the rotary vane actuator how the IMO system reacts to a leakage
the working principles of the RAM type actuator
basically there are two types of electro hydraulic steering gear working
principles the RAM type and the rotary vane type the working principles of the
two are very similar a strong slow movement of a mechanical surface is
created by the use of high oil pressure ram type uses cylinder pistons rotary
vane uses pressure working on the side of a vane on the RAM type the piston is
connected by a ram to a tiller and the tiller is fixed to the rudder stopped
creating the rotating movement on the rotary vane the vane is fixed to a boss
that is fixed directly to the stock the principles as described for the rotary
vane steering gear can easily be transformed to the RAM type typical for
RAM type steering gears is that they work with a much higher hydraulic
pressure they need an external rudder stock bearing and the working angle is
limited compared with the rotary vane steering gear the standard model is used
on all vessels except tankers with single rudder installation above 100,000
deadweight tons safety safety against single failure on the hydraulic system
according to sonís rules the IMO model is specially designed for tankers with
single rudder installation above 100,000 deadweight tons to comply with the
soleus rules it can also be used for other ships and/or rudder arrangements
where extraordinary safety is wanted safety safety against single failure on
the hydraulic system according to Solace rules
this is a schematic drawing of the standard steering gear you can click on
the buttons marked Porsche or starboard to see how it works and click on the
different parts for more information the model shows a normal operation situation
with one pump running using both pumps will double the speed of the rudder
you
this is a schematic drawing the IMO steering-gear you can click on the
buttons marked port or starboard to see how it works and click on the different
parts for more information the model shows a normal operation situation with
one pump running using both pumps will double the speed of the rudder
you
you will now be shown how the IMO system reacts on a leakage
you
to view how this situation is displayed on the wheelhouse panel click the link
you
the iro steering-gear is redundant for leakage over the vein seals so if the
oil can bypass one of the veins for any accidental reason the leaking vein can
be put out of function and the steering gear will operate on the other vein only
however if a leakage should occur over one of the stoppers both veins will be
inoperable a situation like this is not covered by the soleus class requirements
the double IMO will protect against accidental bypass over one of the
stoppers as well the double IMO is designed for ship owners who want the
most ultimate safety further than required by the sonís or class rules
the purpose of the locking device is to fix the rudder in any position and may
be used during maintenance of steering gear
anchoring
or towing