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ROV's FOR BEGINNERS
Propulsion Systems
Propulsion systems come in a few different types, Electrical, Hydraulic and
ducted jet propulsion.
The different types have developed to suit the size of vehicle and type of
work expected to be performed in some cases the actual location of the work task
has dictated the type of propulsion used.
The main goals of all designs for a propulsion system are high thrust to
physical size and power input ratio.
The development of each type has been progressing slowly due to the inherent
conservative attitude of most ROV operators and technicians, the call word seems
to be " let well alone if it works "
The main force in the change has been the desires of the Operating companies
and the Users of the ROV's to extend the operating window of the equipment. (
i.e. The more powerful the propulsion of the ROV the stronger sea currents the
ROV can operate in and consequently extend the revenue making yearly season.)
One other factor has been to extend the reliability of the Propulsion system
and it's associated sub components so that the catastrophic failure rate
decline. In the early development of the ROV a general practice was to replace
and refit electric motor units every 50 to 100 hours of operations, which
increased the inventory of parts required offshore and the possibilities of
errors by the technicians in reassembling the motors.
The last section in the previous statement would also be true for Hydraulic
propulsion systems.
The propulsion system has to be a trade off between what the ROV requires to
perform a work task and what the practical dimensions of the ROV is allowed to
be, typically the more power required the heavier equipment on the ROV and
subsequently all parts of the ROV system will grow exponentially bigger and the
requirement for more power increases again.
This is why a majority of ROV's are restricted to a few work tasks only
without major modifications.
The subject of the choice of the Propulsion system is a very touchy subject
in the ROV industry because most of us have one or other opinion that we will
not budge from.
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