Guide for Welding Procedure Specification (WPS) qualification for weld overlay Application

Welding Procedure Specification- WPS

In this post we have detailed out, how to qualify a welding procedure specification-WPS for weld metal overlay / cladding / surfacing , for both corrosion resistance overlay and wear resistance overlay welding. The Welding Variables differ for weld overlay applications and are specified in ASME Section IX under Special Process Variables. See below Variables in ASME Section IX for SMAW weld overlay qualification (Table QW 253.1). The variables are not same what is being considered in general SMAW WPS qualification as listed in Table QW-253.

Click here to Learn about Essential, Non-Essential & Supplementary Essential Welding Variables.

The reference code selected for the purpose of qualification of cladding procedure and welder qualification is ASME BPVC (Boiler and Pressure Vessel Code) section IX.

Click here to Learn How to write a WPS.

Step by step procedure for WPS preparation:

Welder Qualification

  • For the welder performed the PQR qualification test prepare the Welder certificate.
  • For additional welders , ask them to perform welding as per qualified WPS
  • Perform the NDT & Mechanical test on the welded coupons as per the requirements of ASME Section IX.
  • After successful completion of tests, prepare the Welder performance Record.

Selection of  PQR Test coupon thickness

Tube sheet: tubesheet sample should have  a thickness = minimum thickness of production or 50mm (2” ) whichever is lesses.

Plate: Plate sample shall have thickness = minimum thickness of production joint or job requirements. The thickness limit qualified Table QW-453.

Preparation of Test Sample:

A test sample of same grade, or same P Number or similar chemical composition is selected for test coupon. The dimensions of the test specimen is as given in below figure..

150mm x 150mm x minimum thickness of production, overlay for a width of 38mm minimum.

Weld the Overlay as shown below

wps for welding

Tests as per standard (ASME BPVC Section IX)

welder qualification test

Example: For Corrosion resistant overlay

  • Liquid Penetrant Test as per ASME BPVC Section V article 6,

Acceptance Criteria for Liquid Penetrant Testing

Relevant indications: indications with major dimensions greater than 1/16 in. (1.5 mm)

  • Chemical Analysis at a depth of overlay thickness for which WPS to be qualified, refer Figure 2 below
wps in welding
  • 4 bend tests (2 transverse and 2 longitudinal ) or (4 Transverse).


The weld and heat‐affected zone of a transverse weld bend specimen shall be completely within the bent portion of the specimen after testing.

The guided‐bend specimens shall have no open discontinuity in the weld or heat‐affected zone (HAZ) exceeding 1/8 inch (3 mm), measured in any direction on the convex surface of the specimen after bending.

Open discontinuities occurring on the corners of the specimen during testing shall not be considered unless there is definite evidence that they result from lack of fusion, slag inclusions, or other internal discontinuities.

For corrosion‐resistant weld overlay cladding, no open discontinuity exceeding 1/16 in. (1.5 mm), measured in any direction, shall be permitted in the cladding, and no open discontinuity exceeding 1/8 in. (3 mm) shall be permitted along the approximate weld interface.

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