23931 version 1
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Demonstrate knowledge of heavy trailer systems
Level
4
Credits
2
Purpose
This theory-based unit standard is for people in the automotive heavy repair
industry. People credited with this unit standard are able to demonstrate
knowledge of: drawbar trailer and semi-trailer configuration and suspension;
trailer and semi-trailer air braking systems; and trailer steering and semitrailer self-steering systems.
Subfield
Motor Industry
Domain
Automotive Trailers
Status
Registered
Status date
21 September 2007
Date version published
21 September 2007
Planned review date
31 December 2012
Entry information
Open.
Replacement information
This unit standard and unit standard 23932 replaced unit
standard 2341.
Accreditation
Evaluation of documentation and visit by NZQA and
industry.
Standard setting body (SSB)
NZ Motor Industry Training Organisation (Incorporated)
Accreditation and Moderation Action Plan (AMAP) reference
0014
This AMAP can be accessed at http://www.nzqa.govt.nz/framework/search/index.do.
Special notes
1
Legislation and publications relevant to this unit standard may include but are not
limited to – Health and Safety in Employment Act 1992; Goods Service Vehicle
(Constructional) Regulations 1936; Heavy Motor Vehicle Regulations 1974; Traffic
Regulations 1976; Land Transport Rules: Heavy-vehicle Brakes 2006, Rule 32015;
Heavy Vehicles 2004, Rule 31002; Vehicle Repair 1998, Rule 34001; Vehicle
Standards Compliance 2002, Rule 35001/1; New Zealand Standards NZS 4711:1984
Qualification tests for metal-arc welders; NZS 5446:1987 Code of practice for heavy
motor vehicle towing connections: drawbar trailers; Vehicle Inspection Requirements
Manual (VIRM) – In-service certification.
 New Zealand Qualifications Authority 2016
23931 version 1
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2
Land Transport Rules are produced for the Minister of Transport by Land Transport
New Zealand. These rules are available online at
http://www.landtransport.govt.nz/rules/.
New Zealand Standards are available from Standards New Zealand, Private Bag
2439, Wellington; phone 04 498 5990; or website http://www.standards.co.nz.
The VIRM is published by Land Transport New Zealand and is available online at
http://www.landtransport.govt.nz/certifiers/virm-in-service/index.html.
3
Definition
Service information may include but is not limited to – technical information of a
vehicle, machine, or product detailing operation; installation and servicing
procedures; manufacturer instructions and specifications; technical terms and
descriptions; and detailed illustrations. This can be accessed in hard copy or
electronic format and is normally sourced from the manufacturer.
4
All trailer repairs and alterations must conform to the requirements of the Land
Transport Rules.
5
All welding to towbars, drawbeams and drawbars must conform to NZS 5446:1987
Code of practice for heavy motor vehicle towing connections: drawbar trailers and be
performed by a person holding a current NZS 4711:1984 Welding Certificate.
6
Brake equipment, repairs and alterations to equipment and replacement parts must
conform to the requirements of the Land Transport Rule, Heavy-vehicle Brakes 2006,
Rule 32015.
Elements and performance criteria
Element 1
Demonstrate knowledge of drawbar trailer and semi-trailer configuration and suspension.
Performance criteria
1.1
Tractor, semi-trailer and trailer configurations are described in accordance with
manufacturer specifications.
Range
1.2
Drawbar trailer axle systems are described in accordance with service
information.
Range
1.3
A Train, B Train.
two axle, three axle, four axle.
Semi-trailer axle systems are described in accordance with service information.
Range
single axle, two axle, three axle.
 New Zealand Qualifications Authority 2016
23931 version 1
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1.4
Drawbar trailer and semi-trailer suspension systems are described in
accordance with service information.
Range
1.5
single axle, close and wide-space tandem, close and wide-space
tri-axle.
Legislative requirements when repairing trailer and semi-trailer drawbars and
suspension is identified.
Element 2
Demonstrate knowledge of trailer and semi-trailer air braking systems.
Performance criteria
2.1
The operation of the trailer and semi-trailer air braking systems are described in
accordance with service information.
Range
air lines, air supply and storage, automatic drain valve, brake
chamber, slack adjuster, spring brake, relay-breakaway valve,
tractor protection valve, air operated trailer coupling, air operated
levelling system.
Element 3
Demonstrate knowledge of trailer steering and semi-trailer self-steering systems.
Performance criteria
3.1
Drawbar trailer towing and turning systems are described in accordance with
service information.
Range
3.2
friction turntables, drawbars.
Semi-trailer turntables are described in accordance with service information.
Range
friction type, anti-friction type;
semi-oscillating, compensating.
3.3
Semi-trailer kingpins and locking devices are described in accordance with
service information.
3.4
Semi-trailer turntable self-steering is described in accordance with service
information.
3.5
Semi-trailer castering axle self-steering is described in accordance with service
information.
Range
forward steering, steering control and damping, reverse locking.
 New Zealand Qualifications Authority 2016
23931 version 1
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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.
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 NZ Motor Industry Training Organisation (Incorporated)
janet.lane@mito.org.nz if you wish to suggest changes to the content of this unit standard.
 New Zealand Qualifications Authority 2016