ICGSMA Bulletin - Indian Coast Guard

ICGSMA BULLETIN (JAN - MAR 13)
direction which makes the ship turn. Most tunnel
thrusters are driven by electric motors, but some
are hydraulically powered. These bow thrusters
also known as tunnel thrusters may allow the ship
to dock without the assistance of tugboats, saving
the costs of such service. Ships equipped with
tunnel thrusters typically have a sign marked above
the waterline over each thruster on both sides as a
big cross in a red circle.
TUNNEL THRUSTER
Tunnel thrusters increase the vessel's
resistance to forward motion through the water,
but this can be mitigated through proper fairing
aft of the tunnel aperture. Ship operators should
take care to prevent fouling of the tunnel and
impeller, either through use of a protective grate
or by cleaning. During vessel design, it is
important to determine whether tunnel
emergence above the water surface is
commonplace in heavy seas. Tunnel emergence
hurts thruster performance and may damage the
thruster and the hull around it.
BOW AND TUNNEL THRUSTER
INTRODUCTION
D Singh, Adh (R)
ICGS C - 149
A bow thruster or stern thruster is a
transversal propulsion device built into or mounted
to either the bow or stern of a ship or boat to make
it more maneuverable. Bow thrusters make
docking easier since they allow the captain to turn
the vessel to port or starboard side without using
the main propulsion mechanism which requires
some forward motion for turning. A stern thruster
is of the same principle, fitted at the stern. Large
ships might have multiple bow thrusters and stern
thrusters. Large vessels usually have one or more
tunnels built into the bow, below the waterline. An
impeller in the tunnel can create thrust in either
BOW AND TUNNEL THRUSTER
An insight to trouble shooters 16