Non SEAPA Slesinger Flashcards
What are the four components of steering a ship’s systems?
CHAPTER 4 PROPULSION AND STEERING
1. Power Source, Power Transfer & Control System, Hydrodynamic Driver, & Thrust Directional Control Mechanism.
Each component plays a crucial role in the overall operation and efficiency of the ship.
What is the purpose of the power transfer and control system?
- To transfer and control rotative force to the tug’s hydrodynamic driver (typically a propeller).
To manage the distribution of power from the engine to the propulsion system
This system ensures that the ship can maneuver effectively and respond to control inputs.
What effect has the diesel engine had on the design of tugs?
- Allowed smaller, more powerful tugs to be built, increased the range and power of tugs.
Increased efficiency and power output
Diesel engines have allowed for more compact designs and improved performance in tugs.
Describe the DR system of engine control.
The DR system is the simplest system of maneuvering. The engine is directly connected to the propeller shaft, and the direction of its rotation is the same as that of the engine. The engine must be stopped between maneuvers or when changing maneuvers from ahead to astern and vice versa. The engines are started by compressed air injected into a reservoir cylinder.
These engines may be fitted with wheelhouse controls so that they need not be tended by an engineer.
Directly regulates engine speed and power output
This system involves a straightforward mechanism for controlling engine performance.
What made the DR system obsolete?
- Limited number of maneuvers, engine speed may not permit a propeller of the most efficient size, vulnerability to mishap (i.e., failure to start, or starting up in wrong direction).
Advancements in technology leading to more efficient systems
The introduction of digital controls and automated systems replaced the DR system.
Describe the DE system of engine control.
- The DE system consists of engine-driven generators that supply current to the electrical-drive motors connected to the propeller
Digital Engine control system that enhances performance and efficiency
DE systems allow for precise control over engine functions.
What are the advantages of DE drive?
- A wide range of speeds available from stop to full speed ahead or astern. The fact that the main engine (or engines) runs at a constant speed.
- Improved fuel efficiency
- Enhanced control
- Reduced emissions
These advantages contribute to better environmental performance and operational cost savings.
What are the principal disadvantages of DE drive?
High costs, vulnerability to salt, and dampness.
- Higher initial cost
- Complexity in maintenance
While DE drives offer many benefits, their complexity can be a barrier.
How does an SCR system differ from the conventional DE drive?
- The SCR system employs an AC generator whose current is then converted by silicon control rectifiers (SCRs) to DC current for driving the propulsion motors.
SCR systems use silicon-controlled rectifiers for power management
This allows for better control of electric propulsion compared to conventional systems.
Are there any particular advantages to the SCR system?
- The SCR system is a more modern development of the DE drive. It is less costly than DC installations, and the main engine generators can furnish current for ship supply.
- Greater efficiency
- Flexible control options
- Reduced wear on components
SCR systems provide significant operational benefits in marine applications.
Describe the CPP system.
- The controllable pitch propeller is not only an energy converting (rotative force to thrust), but it is also a transmission since it changes the direction of thrust by reversing the pitch of the propeller blades. The amount of thrust is also regulated by reducing or increasing the pitch as required by the circum-stances. Stopping is achieved by flattening the pitch so that it is in neutral and does not develop thrust ahead or astern even though the propeller continues to turn. The pitch is controlled by an inner shaft inside the drive shaft that engages cams on the propeller blades in the hub of the drive shaft.
Controllable Pitch Propeller system that allows for adjustable blade angles
This system enables better maneuverability and efficiency in various conditions.
What maneuvering function is housed in CPP?
- Amount of thrust and reversing mechanism.
Thrust control and direction adjustment
CPP systems enhance a vessel’s ability to maneuver in tight spaces.
How does a reverse reduction gear change propeller shaft rotation?
- Through sets of additional gears and clutches; one for reverse and one for ahead.
This mechanism is crucial for tugs and vessels needing to maneuver backwards.
What are the disadvantages of a SPS?
- Reversing thrust requires rotating the drive unit 180 degrees; the SPS may be constantly thrusting while shifting thrust direction.
- Increased mechanical complexity
- Potential for higher wear and tear
While advantageous, steerable propeller systems may require more maintenance.
The tow hook is an alternative to:
A. A staple
B. A H Bitt
C. A bollard
D. None of the above
B. A H-bitt can be tripped to prevent capsizing or girting
One of the primary differences in layout between the conventional tug and ASD or tractor tug is the location of the staple. The Staple functions as the tugs _______ point.
Towing
Which way does an ASD Tug tend to undock?
A. Bow first
B. Stern first
C. Laterally with both ends coming off at once
B. Stern first
A tractor tug will steer ________ a turn.
Into
Why is it necessary to have a high approach speed when docking a VSP tractor tug?
When holding the tug’s bow off the dock the wheel-induced transfers thrust may prematurely retardant the tugs way.
What hydrodynamic pressure zones are caused by the ship’s passage through the water?
- High pressure at the bow, lower pressure alongside the ship and suction at the stern.
High-pressure zones, low-pressure zones, and wake turbulence
These zones affect the tug’s handling and stability.
What are the hydraulic effects on the tug as it makes an approach close to a ship underway?
- It draws the tug toward the ship by the suction aft and it pushes the tug away from the ship forward.
Tug power, tug position, and the ship’s movement
Suction effects, lateral forces, and changes in water flow
These effects can significantly influence the tug’s maneuverability.
How should the tug handler compensate for these effects?
- By pacing the ship long enough to see how the tug is affected and then gently easing the tug in alongside. An experienced operator lets the tug be drawn in slowly by the suction aft with the helm turned slightly away from the ship, works the tug in against the hydraulic forces forward
Adjusting speed, altering heading, and maintaining distance
Proper compensation is necessary to ensure safe operations.
Should a tug ever back its engine when coming alongside a ship?
- The tug operator should avoid backing when the tug is overtaking the ship to get into position to push or pull. When the tug backs its engine, the tug may not respond and can cause damage to itself and to the ship.
No, it can lead to loss of control
Backing the engine can destabilize the tug and create dangerous situations.
What may happen when a tug crosses a vessel’s wake?
- The propeller may cavitate.
It may experience sudden changes in stability and control.
This can lead to accidents if not navigated carefully.
How can cavitation endanger a tug crossing a ship’s wake?
- If the tug is overtaking the ship and backs its engine, the tug may not respond and can cause damage to itself and to the ship.
Cavitation can cause propeller damage and loss of thrust.
This phenomenon occurs when low pressure forms around the propeller.
Vertices clearances of bridges and overhead cables are in:
A. Feet above low water.
B. Feet above high water.
C. Meters above high water.
D. Feet above mean high water.
US Coast Pilot #8
D. Feet above mean high water.
S – 102
Barometric surface
S – 104
Water level information for surface navigation
S – 111
Surface currents
S – 121
Maritime limits and boundaries
S – 122
Marine protected areas
S – 123
Marine radio services
S – 124
Navigational warnings
S – 125
Navigational services
S – 126
Physical environment
S – 127
Marine traffic management
S – 128
Catalog of nautical products
S – 129
Under keel clearance management This deals with the exchange of information between an under Cleo clearance management system, and an onboard navigation system.
S – 201
Aid to navigation this provides a common structure for the exchange of information about aids to navigation (ATON)
S – 211
Port call message form
S – 240
DGNSS station almanac
S – 401
Inland ENC
S – 402
Bathymetric contour overlay for inland ENC
S – 411
See Ice information
S – 412
Weather Overlay
