A WPS is a written qualified welding procedure prepared to provide direction for making production welds.
Completed WPS shall describe all of the essential, nonessential, and, when required, supplementary essential variables.
• Essential variables are those in which a change, as described in the specific variables, is considered to affect the mechanical properties of weldment, and shall require requalification of the WPS.
• Supplemental essential variables for a process are those conditions which, when changed, will affect the impact properties of the weld.
(If impact test is not required, supplementary essential variables are not be considered as a nonessential variables. In this case this supplementary essential variables are not needed to be recorded in WPS)
• Acceptable (i.e. qualified) ranges
Article II - Welding Procedure Specifications - WPS
Non-E ssent ial Variables
• Non-essential variables for a process are those conditions which, when changed, do not have a major impact on the weld. They must, however, be considered and addressed on the WPS.
• A change of nonessential variables will requires a change in WPS but not require a re-qualification.
The special process essential variables for corrosion-resistant and hard-
surfacing weld metal overlays are as indicated in the tables for the specified process.
(It means th at s eparate PQR /WPS in acco rd ance w it h QW-252.1/253.1…….. 264.1 plu s QW-453 for ov erlay s hall be pr epared. The P QR/WPS wh ic h were pr epared in accor dance w it h QW-252/253…….264 shall no t be us ed for overla y pro cess)
Welding
Steps of Preparing PQR/WPS<Sec.IX, QW-201, Sec VIII-1, UW-28>
Draft WPS Preparation of Test Coupon Preparation of Test Specimen Welding Test Record on PQR Certification Of PQR Qualification Of WPS Welding parameters Full supervision Mechanical Test (Tension, Bend etc.)
QW-463 QW-463 Welding Data Test Result Acceptance Criteria (QW- 150,160,170,180) Essential Variables
Supplement Essential Variables Non-essential variables other information
Legends
: May use subcontractor : Must be done by Manufacturer
Welding
Steps of Preparing PQR/WPS<Sec.IX, QW-201, Sec VIII-1, UW-28>
Things to Consid er When Pre paring a WPS.
1. Compatibility of the weld metal and base metal 2. Metallurgical properties
3. Heat treatment requirements 4. Design of joints and loadings 5. Desired mechanical properties 6. Service requirements
7. Welder’s ability 8. Equipment available 9. Location of welds 10. Economy
Welding
Steps of Preparing PQR/WPS<Sec.IX, QW-201, Sec VIII-1, UW-28>
Writi ng a WPS
When writing a WPS, you should first determine what the intended usage will be, the welding equipment available, and the ability of the welders using the procedure. There are four general considerations:
What base materials will be welded? What filler metals will be used?
What welding processes will be used?
Welding
Steps of Preparing PQR/WPS<Sec.IX, QW-201, Sec VIII-1, UW-28>
Writi ng a WPS
Once you have identified the base metals you intend to weld and identified their P-Nos. per QW-422, you should then select the most economical base metal from QW-424 to use for the test coupon.
Next, the appropriate filler materials are selected and their A-Nos. determined from QW- 432 and QW-442. You may also need to consider shielding gas or flux and any position restrictions that may apply.
Welding processes to be used should be determined and the required variables of QW- 250 addressed. It is also necessary to consider the types of production joints, welder techniques, and available equipment.
Finally, you need to consider the service or production restrictions. These include such things as Code / customer requirements, preheat / PWHT, corrosion, and notch toughness.
Welding
Steps of Preparing PQR/WPS<Sec.IX, QW-201, Sec VIII-1, UW-28>
Qualif yin g th e WPS
The basic steps for qualifying a WPS are (using the parameters of the unqualified WPS): Establish the test coupon size (QW-451, 462, 463).
Weld the test coupon following the parameters of the WPS (QW-210, 250, 260) : Monitor and document the specifics of the essential variables and, when
applicable, the supplemental essential variables (QW-200.2). It is recommended that all other specifics be measured, documented, and maintained on file.
Cut the coupon into the required test specimens (QW-462, 463). This may be performed by the testing laboratory.
Evaluate the test results per QW-150 to 180. This is the responsibility of the manufacturer.
If the results are acceptable, document them on the PQR and certify.
Compare the PQR with the parameters listed the WPS (essential and supplemental variables) to assure that the full range is supported by the PQR. If not, it may be necessary to supplement the ranges with an additional PQR, or reuse the ranges to within that which is supported.
The WPS may now be added to the certified list of qualified procedures required by QW-201.
Welding
Steps of Preparing PQR/WPS<Sec.IX, QW-201, Sec VIII-1, UW-28>
Perm it ted ch anges to a WPS
A WPS may be revised for several reasons. Among these reasons are: • A change in a non-essential variable. This would require revision but no
requalification.
• A change in an essential or supplementary essential and requalification. • Corrections or updates due to inadvertent errors or to Code Addenda.
A WPS may be revised by:
• Writing a new WPS, including revision number.
Article II - Welding Procedure Specifications - WPS
If “ x” is l oca ted only in the suppleme nta ry esse ntial va riable s, whe n impact test is not required, the se variable s are not consi dere d as n onesse ntial v ariables.
Article II - Welding Procedure Specifications - WPS
Manufacturer’s or Contractor’s Responsi bility
• Each manufacturer and con tracto r sh all q ualify t he WPS by th e welding of test coupons and t he te sting of s pecime ns, a nd t he record ing o f th e welding data and test results in PQ R.
• The weldme nts to b e tested for qualification of proc edures sha ll be welded e ith er by d irect employ ees or b y individuals enga ged by contract fo r th eir s ervices as we lders under the full supervision and contro l of the ma nufacturer or contractor.
• Supervision and cont rol of welding o f the test weldme nts p erform ed by another organiz ation is n ot p ermitted.
• If in an organiza tio n effe cti ve operational cont rol o f welding p roc edur e qualifica tion for two or m ore companie s of differe nt n ames e xists, the companie s in volved shall describe in their Qua lity Contro l
Syst em/Quality Assu rance Progr am. In thi s c ase sepa rate we ldi ng procedure qualifications are not required.
Article II - Welding Procedure Specifications - WPS
Manufacturer’s or Contractor’s Responsi bility
• If in an organiza tio n effe cti ve operational cont rol o f welding p roc edur e qualifica tion for two or m ore companie s of differe nt n ames e xists, the companie s in volved shall describe in their Qua lity Contro l
Syst em/Quality Assu rance Progr am. In thi s c ase sepa rate we ldi ng procedure qualifications are not required.
• When a manufactur er is a cqu ired by a ne w own er, the P QRs and
WPSs ma y be used by the ne w own er witho ut r equa lif ication , pro vid ed all of the foll owi ng are met :
(1) the new ow ner takes respon sib ili ty for the WP Ss and PQRs. (2) the W PSs r eflect t he name of th e new own er.
(3) the Q uality Control System/ Quality Ass urance Program r efle cts the source of the P QRs as being from the former ma nufacturer or
Article II - Welding Procedure Specifications - WPS
Vari ables are defined f or each pr oc ess in QW-250 th ro ug h QW-280
• Each v ariable shall b e addr essed, do n ot s tate N/A but f acts, yes, no , none or any other mea ningfu l definition.
Changes to WP S’s are allo wed, how ever
• Changes in esse nti al and sup plementa ry esse nti al variable s r equire requali fi catio n and a new WPS.
• Changes in no nessential variable s can be made wit hou t
requalificatio n, nee d t o b e docum ente d and t he WPS to be revised.
A WPS is a written qualified welding procedure prepared to provide
direction for ma king produ ction welds.
A WPS used for Code production welding shall be available for reference and review by th e AI at the fa bri cation s ite.
Article II - Welding Procedure Specifications - WPS
Completion of a WPS
• All variables to be addressed.
• Do not state single figu res but always ranges.
• Range s sho uld b e as br oad a s po ssib le but adequa te for t he process. • Joint d esign (nonesse ntial) : do n ot sho w only one joint design but
either make refe rence to jo ints as show n on worksh op dr awings or attach a se para te she et sho wing a variety of joi nts w hich c an be used for t he proce ss.
• QW – 424 : Base me tal used for procedure qualifica tion test coupo n versus range of ba se meta ls qualified.
Article II - Welding Procedure Specifications - WPS
Cont’d c omp letion of a WPS
No limitation in p osition s : qualification in one position q ualifie s the
procedure ( but no t th e welder !! ) for all (meaningfu l) positi ons,
QW-461 Posi tio ns o f gr oov e (G) and f ill et (F) welds in p late and pip e
• 1G, 2G, 3G, 4G for plate groove welds fl at - ho ri zon tal - vert ic al - ov erh ead • 1G, 2G, 5G, 6G f or pi pe gr oo ve weld s
fl at - ho ri zon tal - mu lt ip le
• 1F, 2F, 3F, 4F fo r pl ate fi ll et weld s fl at - ho ri zon tal - vert ic al - ov erh ead
• 1F, 2F, 2FR, 4F, 5F fo r pi pe f il let weld s
Article II - Welding Procedure Specifications - WPS
Cont’d c omp letion of a WPS
Thickn ess ra nge s : “ T“ for ba se metal, “ t“ for de posite d we ld me tal
• Thickness ranges to b e care ful ly co nsi dere d wh en GMAW short circui ting arc we lding is employed (GMAW, short cir cuiting arc welding, t< 13mm => “ T” qualifie d shall be be low 1. 1 time s of test coupon thickne ss.
Prehe at and po stw eld heat t reatment tempera tur es to be con sidered.
Prehe at decrease of 55 C becom e an essenti al variabl e. The meani ng o f pr eheat maintenance is main tenance prehea t upon c ompletion of welding prior to any require d post weld he at treatment.
Electric al cha racteristi cs and Te chn iqu e
Article II - Welding Procedure Specifications - WPS
Subcont racted W elding Proc edures (S ecti on I)
• Section I allows a unique method for “subcontracting” welding procedures for use on PP stamped pipe. The National Certified Pipe Welders Bureau
(NCPWB), a national organization made up of member companies, provides prequalified welding procedures to its members. These procedures can be used for PP stamped pipe by member companies without requalification. The member company must sign each WPS and PQR and accept responsibility for its use and compliance to Code requirements. Remember, these are permitted only for PP stamped boiler external piping
Article II - Welding Procedure Specifications - WPS
Combination of WPS’s
More than one WPS having different variables may be used in a single production joint.
• Each WPS may include one or a combination of processes, filler metals or other variables.
• Range of the deposited weld metal thickness qualified for each process to be considered.
More than one process may be recorded in one WPS
• All variables associated with each process to be applied and addressed. • Base metal and deposited weld metal thickness limits for each process to
be applied.