21070 version 2
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Demonstrate knowledge of seafood vessel stability
Level
4
Credits
20
Purpose
People credited with this unit standard are able to explain: the influence and
points of action of the forces acting on a static seafood vessel; changes in
the forces acting on a vessel during vessel movements, and the effect of
these changes on the size of the righting lever, and the stability of a seafood
vessel; vessel stability during transfer of loads using a seafood vessel’s
vessel-mounted crane or lifting equipment; the effects of a free surface on
the stability of a seafood vessel; and the interpretation of information
available to calculate the effects of changes in vessel loading on seafood
vessel stability.
Subfield
Seafood
Domain
Seafood Vessel Operations
Status
Registered
Status date
19 September 2008
Date version published
19 September 2008
Planned review date
31 December 2013
Entry information
Open.
Accreditation
Evaluation of documentation and visit by NZQA and
industry.
Standard setting body (SSB)
Primary Industry Training Organisation
Accreditation and Moderation Action Plan (AMAP) reference
0123
This AMAP can be accessed at http://www.nzqa.govt.nz/framework/search/index.do.
Special notes
Legislation relevant to this unit standard includes but is not limited to: Maritime Transport
Act 1994, Maritime Rules, and advisory circulars issued under the Rules.
 New Zealand Qualifications Authority 2016
21070 version 2
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Elements and performance criteria
Element 1
Explain the influence and points of action of the forces acting on a static seafood vessel.
Range
forces – gravity, buoyancy;
points of action – centre of gravity, centre of buoyancy, metacentre.
Performance criteria
1.1
The explanation identifies how the forces and their points of action act on a
stable, floating vessel.
1.2
The explanation identifies the metacentric height as a parameter indicating
vessel stability.
Element 2
Explain changes in the forces acting on a vessel during vessel movements, and the effect
of these changes on the size of the righting lever and the stability of a seafood vessel.
Range
forces – gravity, buoyancy;
movements – roll; movement caused by lateral, longitudinal, and vertical
changes in the position of cargo, ballast, or other mass;
points of action – centre of gravity, centre of buoyancy, metacentre.
Performance criteria
2.1
The explanation outlines vessel stability in terms of the relationship between the
centres of buoyancy and gravity, the metacentre of the vessel, and the length of
the righting lever.
2.2
The explanation identifies the causes of lists, lolls, and changes in roll period in
terms of changes in the points of action of the forces acting on the vessel and
the length of the righting lever.
2.3
The explanation outlines vessel stability in terms of stability changes that make
the vessel stiff or tender.
Element 3
Explain vessel stability during transfer of loads using a seafood vessel’s vessel-mounted
crane or lifting equipment.
Range
from rest to suspended, unloading, loading, relocating, during transfer.
Performance criteria
3.1
Vessel stability is explained in terms of the relationship between the centres of
buoyancy and gravity, and the metacentre of the vessel.
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3.2
Vessel stability during a lift is explained in terms of the movement of the centre
of gravity of the vessel during the transfer of a load.
3.3
Vessel stability during load transfer is explained in terms of strategies of
maintaining vessel stability.
Range
3.4
may include but is not limited to – ballasting, fuelling during
discharge, use of loading and unloading plans.
The explanation includes signs that indicate the vessel’s stability has been
reduced.
Element 4
Explain the effects of a free surface on the stability of a seafood vessel.
Performance criteria
4.1
The free surface effect is explained in terms of the movement of the points of
action of the forces acting on the centre of gravity of fluid in a tank, bilge, or on
deck, with a free surface, and on the vessel, as the vessel rolls.
4.2
The explanation outlines vessel stability while a fluid free surface exists aboard
in terms of the size and position of the fluid containers with the free surface.
4.3
The explanation outlines methods used to reduce or eliminate free surface
effects in terms of their application to fluids in enclosed tanks, fluid-like loads in
holds or on deck, water on decks and in bilges, and watertight integrity.
Element 5
Explain the interpretation of information available to calculate the effects of changes in
vessel loading on seafood vessel stability.
Range
one of – stability book, stability control computer programme.
Performance criteria
5.1
The explanation outlines the process of interpretation of the stability information
in terms of vessel behaviour.
Please note
Providers must be accredited by NZQA, or an inter-institutional body with delegated
authority for quality assurance, before they can report credits from assessment against
unit standards or deliver courses of study leading to that assessment.
Industry Training Organisations must be accredited by NZQA before they can register
credits from assessment against unit standards.
Accredited providers and Industry Training Organisations assessing against unit standards
must engage with the moderation system that applies to those standards.
 New Zealand Qualifications Authority 2016
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Accreditation requirements and an outline of the moderation system that applies to this
standard are outlined in the Accreditation and Moderation Action Plan (AMAP). The
AMAP also includes useful information about special requirements for organisations
wishing to develop education and training programmes, such as minimum qualifications for
tutors and assessors, and special resource requirements.
Comments on this unit standard
Please contact the Primary Industry Training Organisation standards@primaryito.ac.nz if
you wish to suggest changes to the content of this unit standard.
 New Zealand Qualifications Authority 2016