Steps to be prepared a pWPS and PQR (ASME IX)
A. Knowledge and understand the specifications
Firstly, we need to identify the welding process, application, and understanding the specification. The WPS must be described all variables in the table QW-252 through 269, which welding process is selected to apply. Each table has detailed the limitation of welding variably by the symbol “>, <, +, -, etc.”, it easy to understand and found explanations at the subdivided variables (QW-400).
Welding Engineer writtes pWPS (preliminary Welding Procedure Specification) for each test coupon.
Ex: for SMAW process as Table QW-253, subdivide QW-402.1 stated change Groove design means a change in the type of groove (V-groove, U-groove, single-bevel, double-bevel, etc.)."
B. Material, tools and equipment
All materials, tools, equipment to be used the test, I recommend to prepare in a checking list for monitoring such as:
B.1 Welding machine and tools
- Multi-amps, welding gauges, tape/square steel, weld purge monitoring (for stainless steel), flashlight, temperature device, etc. are in good condition and calibrated.
B.2 Base material and welding consumables
- Available for review and verification.
- Check: material specification, chemical composition, mechanical properties, NDE, actual dimension, type of inspection certificate, etc.
- If PQR require hardness survey, see NACE MR0175 part 2 & 3.
- If classification society involve, we recommend to invite ASB, DNV, LR classification.
- Test coupon preparations are either select plate or pipe for qualification.
- If qualification on pipe and CVN test, we strongly recommend to set up at 6G position. In case of qualification on pipe OD. less than 100 mm, 2 test coupons must be prepared.
- If any combination procedure, thickness subject to test at latest 13 mm and over.
- Who make the test coupon in accordance with the pWPS.
C. Official running the test coupon
PQR shall be recorded as actual values, true records. Third party inspection should invite to monitor and endorse procedure qualification, we recommend 3 TPIs ABS, DNV-GL, BV
Sequences to be checked as following:
C.1 Before wedlding
- Position: properly tack welding.
- Welding machine: calibrated and ready for using.
- PQR template: ready for recording.
- Welding consumable: had baked and dry out.
- Skilled welder: available with ID for checking by Thirdpaty (if any).
- Inspection tool: certified and ready for using
- Fit-up inspection: as per pWPS.
- Preheat temperature: minimum preheat temperature check and crosscheck by Tempilsik.
C.2 During welding
- Welding parameter: such as voltage, amperage, current & polarity, travel speed, time, gas, backing gas, follow rate within range allowed in pWPS.
- Material: filler metal on each process, gas compositions (%).
- Weld bead: check thickness of weld metal deposit, run out length within range allowed in pWPS.
- Cleaning each weld pass/layer: properly clean by brushing, grinding.
Priority, root layer must be carefully inspected full weldment, any imperfections of lack of root fusion, incomplete penetration, burnout, etc, are cause of rejection.
Rest layers continue deposition as per welding parameter within the pWPS.
C.3 after welding
- Visual inspection after welding, to make sure no crack, complete penetration and complete fusion of base metal and weld metal. After successful welding, test coupon is subjected to non-destructive test and destructive test.
- Based on the proposed WPS, test coupon is prepared, and the coupon is welded as per the values (or range) provided in the pWPS. All the real time data (observed during the welding of test coupon) are recorded.
D. Non-destructive test
- Volumetric NDE are not essential in PQR, but we may perform RT/UT make sure sound weld and no defects are presented of porosity, lack of fusion, slag inclusions etc. Acceptance criteria as per QW-191 (for welder qualification).
E. Destructive test
A lab test body should be used a qualified ISO 17025. All test specimens are required in QW-202
E.1 Essential variables
QW-150 Tension test: 2 samples (either transverse or longitudinal).
Acceptance criteria: Based on a minimum specified tensile of base metal, and matching strength of welding consumable. The tensile strength of joint/specimens shall not less than:
- The minimum specified tensile strength of base metal, or
- The minimum specified tensile strength of the weaker of the two, if base metal of different tensile strength are used, or,
- If the specimens breaks in the base metal outside of weld, the tensile strength shall not less than 95% of the minimum specified tensile strength of the base metal.
QW-160 Guided-bend test: 4 samples (4 - side bends or 2 face bends; 2 root bends).
Acceptance criteria: no open discontinuity in the weld ir HAZ exceeding 3mm.
E.2 Supplementary essential variables
QW-170 Toughness test (CVN): 9 samples or more samples.
Acceptance criteria: lower temperature and absorbed values as specified in contracting project or code application.
Hardness test and macro test: 01 sample, it should subject to test on your PQR, It may conduct on the same sample.
Acceptance criteria: NACE MR0175 (if applicable)
Chemical analysis: stainless steel, alloy should conduct the test, especial type of low carbon content such as type 316/316L, 304/304L, Duplex, Inconel, Monel, Hastelloy, etc.
F. Summary and development WPS
Supporting document for endorse PQR, WPS, Welder performance qualification include MTC (base metal & weld metal), actual PQR recorded, Official PQR, Lab test report, NDE report, official WPS(s).
Format WPS, PQR may be used a suggested format form QW-482, QW-483.
We are recommended a development WPS/PQR format to meet QW-250 and contents of WPS shall be provided all variables for each welding process.