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Variable on Welding procedure specification (WPS) Refer to ASME sec IX

 

Welding procedure specification (WPS) ASME sec IX

A welding procedure specification is a written document providing direction to the welder (or welding operator). It contains all the necessary parameters viz. joints, base metals, filler metals, positions, preheat, PWHT, gas etc. (including ranges, if any) under which the welding process must be performed. These parameters are known as variables (as per ASME Section IX). Three types of variables are mentioned in the code, these are;

  1. Essential Variable
  2. Non essential Variable
  3. Supplementary Essential variable

Essential Variables (For WPS – QG-105.1 & QW-251.2): A change in essential variable is considered to affect the mechanical properties (other than toughness) of the welded joint. Hence the WPS must be requalified, if the essential variable is changed.

Note: QG-105.2 is for Welder.

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Supplementary Essential Variables (QG-105.3 & QW-401.1): 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.

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Nonessential Variables (QG-105.4 & QW-251.3): 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).

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