Section IX of the ASME BPVC




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Section IX of the ASME BPVC

ASME P-Numbers

Structural Welding







Section IX of the ASME Boiler and Pressure Vessel Code


The forms listed below form the basis for verifying welding procedures and welder performance:

  •   WPS    - welding procedure specification

  •   PQR     - procedure qualification record

  •   WPQ    - welder performance qualification 

There are three steps in qualifying welders and welding procedure specifications to Section IX of the ASME Boiler and Pressure Vessel Code (BPVC).  

First, prepare a welding procedure specification (WPS). The WPS must contain the minimum requirements that are specified by the code. The WPS provides guidance for welding by specifying ranges for each variable.

Second, a procedure qualification record (PQR) is used to verify the WPS.  The WPS is qualified by welding procedure qualification test coupons. The variables and tests used are recorded on a PQR.

Third, the performance of the welders is verified by welding performance qualification test coupons. The variables and tests used with the particular  variable ranges qualified are recorded on a welders performance qualification (WPQ) record.

Another way of conceptualizing these requirements is shown below:

Variable ranges
Essential variables
Nonessential variables
Actual variables
Essential variables
Tests and results
Actual variables
Specify Ranges Qualified
Tests and results

Outline of Articles in ASME Section IX 

An abbreviated summary of items covered in ASME Section IX is provided below 

Article I - Welding General Requirements QW-100

Article I covers the scope of ASME Section IX, the purpose and use of the WPS, PQR and WPQ, responsibility, test positions, types and purposes of tests and examinations, test procedures, acceptance criteria, visual examination, and radiographic examination.

Article II - Welding Procedure Qualifications QW-200

Article II covers the rules for the preparation of WPS and PQR.  Each process is listed separately in QW-250 with the essential, supplementary essential, and nonessential variables.  

The WPS shall specify a value or range for each essential, nonessential and, when necessary, each supplementary essential variable listed for each welding process.  The PQR shall record the value for each essential and, when necessary, each supplementary essential variable used.

When a change is made in an essential variable, the WPS must be revised, and requalified with a new PQR, unless the revision can be supported by an existing PQR.

Similarly, when the code requires notch-toughness, supplementary essential variables become additional essential variables.  When a change is made in a supplementary essential variable, the WPS must be revised, and requalified by a new PQR, unless the revision can be supported by an existing PQR for notch-toughness applications.

Article III - Welding Performance Qualifications QW-300

Article III covers the preparation of WPQ records.  Each welding process is listed separately in QW-350 with the essential variables for welding performance. The WPQ form must record a value for each essential variable used and must list a range qualified for each of these essential variables. 

Article III covers responsibility, type of tests, records, welder identification, positions, diameters, expiration and renewal of qualifications.  Welders and Welding Operators may be qualified by visual and mechanical tests, or by radiography of a test coupon, or by radiography of the initial production weld.

Article IV - Welding Data QW-400

Article IV covers welding variables that are used in the preparation and qualification of the WPS, PQR or the WPQ as applicable. Some of the welding variables are listed below:

  •   Joints

  •   Base Materials

  •   Filler Materials

  •   Positions

  •   Preheat

  •   Postweld Heat Treatment

  •   Gas

  •   Electrical Characteristics

  •   Technique

Article IV also includes assignments of P-Numbers (ASME base materials), S-Numbers (other materials), F-Numbers (grouping of filler metals) and A-Numbers (weld metal chemical analysis).

Tables for WPS qualification thickness limits and tables for WPQ thickness and diameter limits are also included.  There are tables for welding positions signifying that a welder who qualifies in a particular position is qualified to weld within a range of positions as appropriate. Furthermore, test coupons, the removal of test specimens, and the test jig dimensions are identified.

Article V - Standard Welding Procedure Specifications (SWPS) QW-500

Article V covers rules for the adoption, demonstration, and application of the Standard Welding Procedure Specifications, (SWPSs).


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Copyright 1999 Robert McCabe                    
Last modified: February 17, 2015