Pressure vessels that are designed and manufactured as per ASME BPVC codes needs qualification of welding procedure as per ASME Sec. IX to ensure the quality of deposited welds. During fabrication it is important to ensure welding operators in the field are maintaining the same quality of welds that is required standards across the board. Moreover The mechanical properties of a weld cannot be verified in production welds after welding so control of the welding process using a WPS is critical. Each organization shall prepare written Welding Procedure Specifications and procedure qualification records to ensure quality of welds.
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ASME BPVC SEC – IX Welding, Brazing, and Fusing Qualifications
The scope of ASME Section IX is the qualification of welders and the welding procedure specifications that are employed in welding according to the ASME Boiler and Pressure Vessel Code and the ASME B31 codes for pressure piping.
The first edition of this safety code was published in 1914 (Boiler Code). 5 X 8 format, 119 pages . The Boiler Code was expanded to include pressure vessels in 1928 (P&PV Code). Section IX (Welding) was added in 1941 to consolidate welding requirements in the construction codes.
ASME Sec. IX Parts
- Part QG – General Requirements.
- Part QW – Welding
- Article 1 – Welding General Requirements
- Article 2 – Welding Procedure Qualifications
- Article 3 – Welding Performance Qualifications
- Article 4 – Welding Data
- Article 5 – Standard Welding Procedure Specifications (SWPSs)
- Part QB – Brazing
- Part QF – Plastic Fusing
let us get familiar with types of VARIABLES
Essential Variables . Essential variables are conditions in which a change, as described in the specific variables, is considered to affect the mechanical properties (other than toughness) of the joint. Before using a procedure specification whose essential variables have been revised and fall outside their qualified range, the procedure specification must be requalified. Procedure qualification records may be changed when a procedure qualification test supporting the change has been completed, or when an editorial revision is necessary to correct an error, as permitted by the rules of the Part applicable to the material-joining process.
Supplementary Essential Variables. Supplementary essential variables are conditions in which a change will affect the toughness properties of the joint, heat-affected zone, or base material. Supplementary essential variables become additional essential variables in situations where the referencing code, standard, or specification requires toughness testing for procedure qualification. When procedure qualification does not require the addition of toughness testing, supplementary essential variables are not applicable.
Nonessential Variables. Nonessential variables are conditions in which a change, as described in the specific variables, is not considered to affect the mechanical properties of the joint. These variables shall be addressed in the procedure specification. A procedure specification may be editorially revised to change a nonessential variable to fall outside of its previously listed range, but does not require requalification of the procedure specification.
Special Process Variables. Special process variables are conditions that apply only to special processes that are described in the Part that addresses those processes. When these special processes are used, only the applicable special process variables shall apply.
WHAT is WPS
As defined in ASME Sec. IX of BPVC a WPS (Welding Procedure Specification) is a written qualified welding procedure prepared to provide direction for making production welds to Code requirements. The WPS or other documents may be used to provide direction to the welder or welding operator to assure compliance with the Code requirements.
What are Contents of the WPS?
The completed WPS shall describe all the essential, nonessential, and, when required, Supplementary essential variables for each welding process used in the WPS. These variables are listed for each Process in QW-250 and are defined in Article IV, Welding Data ASME Sec. IX of BPVC.
The WPS shall reference the supporting Procedure Qualification Record(s) (PQR) described in QW-200.2. ASME Sec. IX of BPVC. The organization may include any other information in the WPS that may be helpful in making a Code weldment.
Can we make Changes in a WPS?
Changes may be made in the nonessential variables of a WPS to suit production requirements without requalification provided such changes are documented with respect to the essential, Nonessential, and, when required, supplementary essential variables for each process. This may be by amendment to the WPS or by use of a new WPS.
Changes in essential or supplementary essential variables require requalification of the WPS (i.e., new or additional PQRs to support the change in essential or supplementary essential variables).
Is there any format for making a WPS?
The information required to be in the WPS may be in any format, written or tabular, to fit the needs of each organization, as long as every essential, nonessential, and, when required, supplementary essential variables outlined in QW-250 ASME Sec. IX of BPVC. is included or referenced.
ASME BPVC Sec IX. Form QW-482 (see Nonmandatory Appendix B) has been provided as a guide for the WPS. This Form includes the required data for the SMAW, SAW, GMAW, and GTAW processes. It is only a guide and does not list all required data for other processes. It also lists some variables that do not apply to all processes (e.g., listing shielding gas which is not required for SAW). The guide does not easily lend itself to multiple process procedure specification (e.g., GTAW root with SMAW fill).
What is PQR?
As defined in ASME Sec. IX of BPVC The PQR (Procedure Qualification Record) is a record of variables recorded during the welding of the test coupons. It also contains the test results of the tested specimens. Recorded variables normally fall within a small range of the actual variables that will be used in production welding.
What are Contents of the PQR?
The completed PQR shall document all essential and, when required, supplementary essential Variables of QW-250 ASME Sec. IX of BPVC. for each welding process used during the welding of the test coupon.
Nonessential or other variables used during the welding of the test coupon may be recorded at the organization’s option. All variables, if recorded, shall be the actual variables (including ranges) used during the welding of the test coupon. If variables are not monitored during welding, they shall not be recorded. It is not intended that the full range or the extreme of a given range of variables to be used in production be used during qualification unless required due to a specific essential or, when required, supplementary essential variable.
ASME Sec. IX of BPVC requires The PQR shall be certified accurate by the organization. The organization may not subcontract the certification function. This certification is intended to be the organization’s verification that the information in the PQR is a true record of the variables that were used during the welding of the test coupon and that the resulting tensile, bend, or macro (as required) test results are in compliance with ASME Sec. IX of BPVC.
One or more combinations of welding processes, filler metal, and other variables may be used when welding a test coupon. The approximate thickness of weld metal deposited, excluding weld reinforcement, shall be recorded for each set of essential and, when required, supplementary essential variables. Weld metal deposited using each set of variables shall be included in the tension, bend, toughness, and other mechanical test specimens that are required.
Can we make Changes in a PQR?
Changes to the PQR are not permitted except as described below. Editorial corrections or addenda to the PQR are permitted. All changes to a PQR require recertification (including date) by the organization.
Is there any format for making a PQR ?
ASME BPVC Sec IX. Form QW-483 (see Nonmandatory Appendix B) has been provided as a guide for the PQR. The information required to be in the PQR may be in any format to fit the needs of each organization. Every essential and, when required, supplementary essential variable described in QW-250 shall be included in the PQR. Also, the type of tests, number of tests, and test results shall be listed in the PQR. Form QW-483 ASME Sec. IX of BPVC does not easily lend itself to cover combinations of welding processes or more than one F‐Number filler metal in one test coupon. Additional sketches or information may be attached or referenced to record the required variables.
Note 1 : The PQR shall be available for review but need not be made available to the welder or welding operator.
Note 2 : Multiple WPSs With One PQR or Multiple PQRs With One WPS.
Several WPSs may be prepared from the data on a single PQR (e.g., a 1G plate PQR may support WPSs for the F, V, H, and O positions on plate or pipe within all other essential variables).
A single WPS may cover several sets of essential variable ranges as long as a supporting PQR exists for each essential and, when required, supplementary essential variable [e.g., a single WPS may cover a thickness range from 1/16 in. (1.5 mm) through 11/4 in. (32 mm) if PQRs exist for both the 1/16 in. (1.5 mm) through 3/16 in. (5 mm) and 3/16 in. (5 mm) through 1 1/4 in. (32 mm) thickness ranges].
References
- ASME BPVC Sec. IX
- nationalboard.org
- Feature Image : Photo by Pete Wright on Unsplash