Welding Variables- Essential variable, Non- Essential Variables & Supplementary Essential Variables

What are Welding Variables?

It is important to remember that the requirements of various welding code and standards (E.g. ASME Section IX, AWS D1.1 or ISO 15614-1) have been tweaked to meet specific service requirements. Each welding code and standard defines essential, nonessential, and supplementary essential variables differently. Therefore, to properly develop welding documentation, the Welding Engineer or Welding Inspector must first review the applicable welding standard to determine which welding parameters are defined as essential, nonessential, and supplementary essential variables. Welding documents have to properly address the three types of variables in order to serve as the foundation of a successful welding program.

Watch this YouTube video for full classroom training on Welding variables, their types and practical Importance.

Watch the online video and learn:

  • What is the welding variable?
  • Types of welding variables?
  • Procedure and Performance variables?
  • What are essential, supplementary, Non-essential, and special variables?
  • Importance of welding variables?

What are Essential Variables?

ASME Section IX, QG-105.1 & QW-251.2, QW-401.1

A change in the essential variable is considered to affect the mechanical properties of the weldment and shall require the requalification of the WPS. Hence, the WPS must be required qualification, if any the essential variable is changed.

What are Supplementary Essential Variables?

QG-105.3 & QW-251.2, QW-401.3

A change in the supplementary essential variable will affect the toughness properties of the joint, heat-affected zone, or base material. Hence supplementary essential variables become additional essential variables in situations where procedure qualification requires toughness testing. When procedure qualification does not require the addition of toughness testing, supplementary essential variables are not applicable.

What are Nonessential Variables?

QG-105.3 & QW-251.3, QW-401.4

Nonessential variables are those in which a change can be made without requalification of the existing WPS since it is not considered to affect the mechanical properties of the joint. Though a change in the nonessential variable doesn’t require requalification of the WPS but still it should be properly addressed in the welding procedure specification (WPS).

What are Special Process Variables?

QG-105.4 & QW-251.4

Special process variables are conditions that apply only to special processes that are described in the Part that addresses those processes.

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