WPS QW-407 PWHT

ASME Section IX WPS : QW-407 Postweld Heat Treatment Example

ASME Section IX Welding Variables for a WPS : QW-407 PWHT

• QW-407.1 - Change in PWHT

  • From no PWHT to with PWHT

  • There are also 4 categories of PWHT types that need to be considered regarding lower and upper transformation temperature which apply to P-1 thru P-15F (Except P-8)

• QW-407.2 - Change in PWHT Time & Temperature

  • A change to the PWHT temperature and time range

  • What is meant by “A change to the PWHT temperature and time range”?

    • The details in QW-407.1 provides the time and temperature categories

  • The PQR PWHT shall be essentially equivalent to that being performed in production

  • At least 80% of aggregate time and temperature

  • Exceptions provided for materials Austenitic Stainless Steel P-8, Aluminum Alloys P-21 thru 26, or Nickel Alloys P-41 thru 49

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Essential Variable: Variables for which a change is considered to affect the mechanical properties (other than notch toughness) of the joint. Essential variable changes that fall outside their qualified range requires re-qualification. 

Supplementary Essential Variable: Variables for which a change is considered to affect the toughness properties of the joint, heat-affected zone (HAZ), or base material.

Supplementary essential variables become additional essential variables in situations where toughness testing is required. When toughness testing is not required supplementary essential variables are not applicable. 

Non-Essential Variable: Variables for which a change is considered to not affect the mechanical properties of the joint. This allows for editorial revisions to procedures within that permitted by Section IX without the need to requalify the procedure. Nonessential variables shall be documented on the procedure. 

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