19005 Demonstrate knowledge of electric welding principles and

							                                                                                19005 version 2
                                                                                    Page 1 of 4

Demonstrate knowledge of electric welding principles and applications

Level                              5

Credits                            3

Purpose       This unit standard is intended for the training and assessment of electricians
              beyond basic trade level. It covers the principles and applications of electric
              welding.

              People credited with this unit standard have demonstrated knowledge of:
              – the principles of electrical arc and resistance welding; and
              – applications in welding machines and industrial welding processes.


Subfield                           Electrical Engineering

Domain                             Electrical Installation and Maintenance

Status                             Expiring

Status date                        19 June 2009

Date version published             19 June 2009

This unit standard is expiring. Assessment against the standard must take place
before the expiry date set out below.

Expiry date                        31 December 2012

Entry information                  Recommended: National Certificate in Electrical
                                   Engineering (Electrician) (Level 4) [Ref: 0313] or
                                   equivalent trade qualification for electricians.

Accreditation                      Evaluation of documentation and visit by NZQA, industry
                                   and teaching professional in the same field from another
                                   provider.

Standard setting body (SSB)        ElectroTechnology Industry Training Organisation

Accreditation and Moderation Action Plan (AMAP) reference                    0003
This AMAP can be accessed at http://www.nzqa.govt.nz/framework/search/index.do.

Special notes

This unit standard has been designed for off-job training and assessment.




                                                                 New Zealand Qualifications Authority 2012
                                                                                19005 version 2
                                                                                    Page 2 of 4

Elements and performance criteria

Element 1

Demonstrate knowledge of arc welding principles.

Performance criteria

1.1       The basic principles of arc welding are described with the aid of a circuit
          diagram, and with reference to the parameters affecting the weld.

          Range         circuit diagram showing – energy source, cables, work-piece,
                        electrode and holder;
                        parameters – striking voltage, arc voltage, current, arc length, weld
                        penetration, constant current welding machines, drooping
                        characteristic.

1.2       Distribution of welding heat between electrode and base metal is explained in
          terms of type of supply and electrode polarity.

          Range         alternating current (ac), direct current (dc), reversed-polarity direct
                        current.

Element 2

Demonstrate knowledge of alternating current welding machines.

Performance criteria

2.1       The methods used to control the output of welding transformers are explained.

          Range         methods – tapped secondary, movable core, movable primary,
                        saturable reactor three-phase with regulator.

2.2       The methods used to achieve a drooping characteristic and to limit the short
          circuit current are stated.

2.3       The operation of a typical welding alternator is described with reference to
          output control.

Element 3

Demonstrate knowledge of direct current welding machines.

Performance criteria

3.1       The operation of a dc welding transformer/rectifier set is described with
          reference to circuit diagram and output control.




                                                                 New Zealand Qualifications Authority 2012
                                                                             19005 version 2
                                                                                 Page 3 of 4

3.2      The operation of dc welding generators is described with reference to output
         control and voltage versus current characteristics.

          Range        dc welding generators – constant current, constant voltage,
                       constant current and voltage.

Element 4

Demonstrate knowledge of arc welding processes.

Performance criteria

4.1      Welding processes are explained with reference to the method of arc shielding,
         type of supply, use of electrodes, and advantages of each process.

          Range        welding processes – manual shielded-arc, submerged-arc, gas-
                       shielded-arc, tungsten inert gas (TIG) welding, metal inert gas
                       (MIG) welding.

Element 5

Demonstrate knowledge of resistance welding.

Performance criteria

5.1      The principle of resistance welding is explained with reference to the heat
         energy formula, the formation of the weld, and typical current and voltage.

          Range        Heat = I2Rt joules.

5.2      The difference between lap and butt welding is explained.

5.3      The four stages in the operating sequence of resistance welding are described.

          Range        squeeze time, weld time, hold time, off time.

5.4      Lap welding processes are described with reference to the nature of the welds
         and how they are achieved.

          Range        processes – spot welding, seam welding, projection welding.

5.5      Butt welding processes are described with reference to the nature of the welds
         and how they are achieved.

          Range        processes – upset butt welding, flash butt welding.




                                                              New Zealand Qualifications Authority 2012
                                                                              19005 version 2
                                                                                  Page 4 of 4

5.6       Methods of control of resistance welding are discussed from the point of view of
          the welding current, and the advantages of each method are stated.

          Range         methods – slope control, pulsation control, synchronous control,
                        sequence timer control, primary current control using ignitron and
                        silicon-controlled rectifiers (SCRs).

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.




                                                               New Zealand Qualifications Authority 2012