Hamilton Jet HJ241, Manual

Page: 19 / 202

1.3
1 INTRODUCTION & PRODUCT DESCRIPTION
1.1 T
HE
H
AMILTON
W
ATER
J
ET
S
YSTEM
HJ-241 / HSRX
TAILPIPE:— Aft of the Impeller is the Tailpipe
section containing a water lubricated marine
bearing to support the rear of the Mainshaft. The
Tailpipe contains a stator section that has vanes to
remove the rotational component of the flow so that
a uniform axial flow is presented to the Nozzle.
NOZZLE:— After the water flow passes the pump
(Im Stator), it is at a higher pressure and
relatively low velocity. At the Nozzle outlet, the
pressure is at atmospheric. This difference in flow
pressure is converted to flow velocity in the Nozzle.
The correct Nozzle sizing is critical to the correct
operation of the pump in a given application.
STEERING (JT TYPE STEERING NOZZLE):— The
Steering assembly is attached to the rear of the
Tailpipe. It consists of a Steering Housing, Nozzle
Insert and Steering Nozzle (which incorporates the
Nozzle described above). The Steering Nozzle is
mounted inside the Steering Housing on vertical
pivot pins and is rotated to port or starboard by
linkages attached to an inboard Steering Cylinder.
The Insert inside the Steering Housing ensures that
the flow exiting the Stator section reaches the final
Steering Nozzle outlet without being disturbed by
the steering mechanism, thus maximising steering
efficiency.
REVERSE DUCT:— The Reverse Duct is attached by
horizontal pivot pins to the Tailpipe and can be
positioned up or down by the inboard Reverse
Cylinder. The ahead / astern function of the Reverse
Duct is an integral part of the Hamilton Jet package.
The split deflector type Reverse Duct is designed to
provide maximum astern thrust under all conditions
of vessel speed, water depth and throttle setting. A
splitter is incorporated to divide the flow and angle
the astern jet stream downwards and to the side, to
clear the vessel Transom and Intake opening. This
prevents recycling of flow through the Jet Unit
(which may be aerated or contain sediment) and
also excessive disturbance of the bottom of the
waterway. The result is very high reverse efficiency
that contributes to the excellent manoeuvrability
afforded by a Hamilton waterjet.
TRANSOM SEAL:— The Transom Seal serves to seal
the hole in the vessel Transom through which the
waterjet passes. It is bolted to the vessel Transom
and incorporates a flexible element which contacts
and seals around the Intake.
SCREEN RAKE:— The HJ-213 to HJ-403 Jet Units
may be fitted with a Screen Rake as an accessory
item. The Screen Rake is a foot-operated rake
mounted in the lower half of the Intake, designed to
clear any debris that may be caught by the Intake
Screen. The spring return foot pedal for operating
the Screen Rake is mounted on the port side of the
Intake casing.
OVERFLOW PREVENTER OR HATCH EXTENSION
(OPTIONAL EXTRA):—
Hamilton Jet Units are not
fitted with Overflow Preventers as standard - this is
an optional extra.
The Overflow Preventer / Hatch Extension is used
where the static waterline (vessel fully laden) is
above the level of the Inspection Cover. It is
attached to the top of the Intake outside the
Inspection Hatch.
DRY RUN KIT (OPTIONAL EXTRA ON HJ-212 TO
HJ-362 JET UNITS):—
Hamilton Jet Units are not
fitted with the Dry Run Kit as standard - this is an
optional extra.
The Dry Run Kit is a simple solution to the problem
of starting the engine before putting the vessel in the
water, where there is no gearbox fitted. It is
particularly useful for Man-Overboard boats and
Lifeboats where it is important to ensure that the
engine will start before the vessel is in the water.
The Dry Run Kit consists of a special bearing, which
can be run dry for short periods and run for long
periods with water lubrication.