HAMILTON WATER JETS - PowerPoint PPT Presentation

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HAMILTON WATER JETS

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HAMILTON WATER JETS Nature Newton s Third Law of Motion Every action has an equal and opposite reaction . Water jet - Main parts Cast aluminium pump unit and ... – PowerPoint PPT presentation

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Title: HAMILTON WATER JETS


1
HAMILTON WATER JETS
2
(No Transcript)
3
Nature
  • Newtons Third Law of Motion
  • Every action has an equal and opposite
    reaction.

4
Water jet - Main parts
  • Cast aluminium pump unit and intake transition
    duct
  • Stainless steel impeller
  • Astern deflector
  • Steering nozzles

5
Water Jet Advantages
  • Supreme manoeuvrability
  • Turn around axle without touching the wheel
  • Speed zero possible, without switching gears
  • While steering capability is kept
  • Simplicity
  • Better low speed manoeuvrability and better
    acceleration
  • Precise steering control.

6
Water Jet Advantages
  • Safe for persons in water
  • No moving parts extending under boat

7
The Waterjet
Position of the bucket for Ahead
Neutral Astern
8
Steering a Water Jet
  • By changing direction of water stream as it
    leaves the jet unit

Waterflow
9
Going Astern
  • By lowering an astern deflector into the jet
    stream
  • reversing the direction of the force generated

10
Emergency Crash Stop
  • Warn crew to hold on
  • Move Astern Deflector to Reverse position while
    at speed (at full revs)
  • Notes
  • Emergency stop should only be used in extreme
    situations.
  • Engine damage can occur because of lubricating
    oil moving to front of carter

11
Zero Speed
  • By lowering the astern deflector partially in the
    jet stream so ahead and astern thrust is equal

12
Waterjet Operation
  • A waterjets control functions can be used
  • in combination
  • separately
  • to create precise vessel control and
    manoeuvrability in all low and high speed
    situations

13
Throttle
  • Increasing rpms results in
  • increased acceleration
  • increased maneuverability

14
Comparison between jets and outboards
  • Waterjet seems to react slowly
  • Activate steering by giving quite a bit of rudder
    and turning back to central position straight
    afterward
  • Activate stopping by buckets full astern and back
    to neutral position straight after

15
Backing up
  • Steers other way round, compared with outboard
    motors / cars etc.
  • No banana-ing
  • During turn no turning of wheel when changing
    from ahead to astern

16
Steering
17
Moving sideways(multiple jet installations only)
18
Debris Problems
  • Blockages and Debris
  • Any debris caught in the Intake Screen, Impeller
    or Tailpipe stator vanes can affect the Jet
    Units performance

19
Detecting Debris
  • Vibrations
  • Noise in the jet (sometimes)
  • Increased rpms, but less power
  • Loses grip on the water
  • Less speed at high revolutions

20
Unblocking a Jet Unit
  • Backflush the blocked Jet
  • if a reversible gearbox is used
  • Slow or stop engine driving the blocked Jet
  • Bucket up
  • Reverse on other engine (if fitted) to create
    backflow

21
Unblock Jet Unit
  • Operate the manual Intake Screen Rake (if fitted)
  • Remove Inspection Cover on Intake
  • Clear manually

22
Vessel not stopping
  • Boat goes ahead, unless buckets in reverse
    (double jet)
  • One of buckets is not moving, due to broken cable
  • Solution
  • Stop motor at side of broken bucket
  • Unclutch jet unit

23
Cavitation
Cavitation causes a loss of performance and
results in serious damage to the waterjet
components.
24
Cavitation
Cavitation can be caused by Hump
Conditions Overload Weight too far aft
Bad weather or sea conditions Blocked intake
screen Blunt or damaged impellers
Excessive impeller tip clearance Poor
installation
25
Cavitation
Cavitation can be prevented by 1 Increasing the
jet intake pressure i.e. Increase boat speed
but do not increase power 2 Reduce rpm less
throttle coarser impeller, i.e.. less rpm
(steeper pitched blades) 3 Reduce flow plus fit
a smaller nozzle
26
Shallow Water Operation
Avoid pumping stones, sand and debris through the
Jet Unit as this will blunt and wear the
Impeller. The following diagrams illustrate good
and bad practice
27
Shallow Water Operation
28
Shallow Water Operation
  • At high planing speeds, shallow water operation
    is not a problem until the vessel is nearly
    grounded.
  • At slow displacement speeds, avoid using high
    RPM in shallow water.

29
Shallow Water Operation
  • Idle over a shallow area into deep water before
    accelerating.
  • If any debris has been picked up in the intake
    screen, momentarily stopping the engine should
    allow the debris to drop away from the screen.
  • Do not run the Jet if the vessel has run aground.
    Damage may occur to impellers.
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