Guidelines for Witnessing Welding Procedure Qualification Testing

welding procedure qualification testingThe following is a guideline for witnessing and verifying qualification testing of Welding Procedure Specifications (WPS) according to the AASHTO/AWS D1.5-2015 Bridge Welding Code. The guidelines identify what the third-party inspector is required to do when witnessing a test, what the inspector can do to facilitate the process for the fabricator and the reviewer, and what to do with the WPS at the completion of the qualification testing.

PROCEDURE QUALIFICATION RECORDS
A Procedure Qualification Record (PQR) is required for qualifying all SAW, GMAW and FCAW electrodes/electrode fluxes and for qualifying all non-prequalified WPS’s. Following are four situations where a PQR test would need to be performed by the fabricator or contractor. The fabricator should seek preliminary approval from the Owner or Engineer before attempting to qualify a WPS that falls under any of conditions 2 through 4.
1. The fabricator is initially qualifying or requalifying WPS’s for a GMAW, FCAW or SAW process. Note, requalification is no longer required every 60 months for non-FCM WPS’s. They are valid indefinitely unless use of the WPS results in substandard welds. A change in an essential variable is cause for requalification as it has always been. FCM WPS’s are now valid for 60 months, not 36 months.
2. The fabricator intends to use a joint designation or backing that does not match any of the pre-qualified joint designations in Figures 2.4 or 2.5. This could include the angle of the groove, root opening, non-steel backing, position of welding, etc.
3. The fabricator intends to use a non-ASTM A709 (AASHTO M270) material specification or other material not listed in D1.5 (Clause 1.2.2).
4. The fabricator intends to use an electrode or electrode/flux classification not prequalified by D1.5 for the specific grade of steel being welded.
Qualification of WPSs to meet D1.5 – 2015 requires:
1. The third-party inspector to witness the test plate being welded.
2. The fabricator to document the test on the appropriate PQR form.
3. The third-party inspector to sign and put his CWI stamp on the PQR form.
4. The third-party inspector to witness the machining and testing of coupons at the testing facility (if required by the Engineer or Owner).
The fabricator has a variety of options for qualification. They include the following types of tests:
1. Maximum heat input test in accordance to 5.12.1 (this seems to be the most common).
2. Maximum-minimum heat input test in accordance to 5.12.2 (Typically to give the fabricator a wider heat input range).
3. Production procedure qualification test in accordance to 5.12.4 (used to qualify WPSs that use non-standard joint details, SAW with active fluxes for more than two-pass applications, HPS 100W steel with matching filler metals, and ESW or EGW WPSs from Clause 5.14).

The maximum heat input test determines the highest heat input the fabricator can run, and then uses standard tolerances to determine the lowest heat input. The maximum heat input test qualifies standard prequalified joints using prequalified base metal/filler metal combinations. This only requires one test plate to be welded, but it may limit the range of qualification.

The maximum-minimum heat input test requires the welding of two test plates. One test determines the highest heat input. The other test determines the lowest heat input. The advantage to this is the fabricator can qualify a lower minimum heat input than if they just used the standard tolerances.

The production procedure qualification method of 5.12.4 is used to qualify the atypical WPSs. It can also be used as an alternate to 5.12.1 and 5.12.2 using actual production parameters. The WPS is then based on using those production parameters and the limitation of variables from Table 5.4. If a fabricator intends to run a production welding PQR in lieu of 5.12.1, it might be to his advantage to discuss it with the reviewer before running the test. There is usually a controversy over the minimum preheat to be employed for this test. The values as contained in 4.2 are maintained for this test, which means that the fabricator would use the preheats required for the actual production welding, not the preheats required for qualifying to 5.12.1 and 5.12.2. It should also be noted that the allowable heat input range on Table 5.4 has been revised to +/- 20% of the test value. Previously, the range was +10/-30%. These are examples of items that the inspector can remind the fabricator of, to reduce the chance of having the PQR rejected by the reviewer.

Just an FYI, in all the other Code books (i.e. D1.1, D1.2, etc.) PQRs are run similar to the D1.5 Clause 5.12.4 production procedure qualification test.

Here are items the inspector should verify/address when witnessing qualification testing:
1. Verify:
a. Welding process including transfer mode for GMAW. GMAW-S shall not be used for welding bridge members without prior written approval from the Engineer (Clause 4.13.4). See Annex N for information on short-circuiting transfer.
b. Filler metal, flux, filler metal/flux combination and electrode size.
c. Shielding Gas composition and flow rate.
d. Test plate and backing bar material (fabricator must provide MTR’s).
e. Test plate is of the required size per D1.5 Figures 5.1, 5.2, or 5.3.
f. Position of welding.
g. Joint detail.
h. Test plates are properly grounded.
i. Interpass cleaning.
2. Preheat requirements:
a. For the maximum heat input test, the minimum preheat and interpass temperatures must be 210F (see 5.12.1.8).
b. The maximum interpass temperature shall be the upper limit to be used during production welding and shall be indicated on the WPS.
c. For the maximum-minimum heat input test, the preheat range shall be between 50F – 100F, and the maximum interpass temperature shall not exceed 125F (5.12.2.1).
d. For the production procedure test, the preheat shall be the same as the production preheat and shall be indicated on the WPS. Since the test plate is generally 1 to 1-1/4″ thick, the minimum preheat and interpass temperatures should be 70F for non-FCM material (Table 4.3). For FCM material see Tables 12.3, 12.4 or 12.5 for the applicable preheat temperature. If the fabricator is qualifying both FCM and non-FCM in the same test, check with the reviewer for pre-heat requirements. This seems to be a gray area in the code, so a mutual understanding needs to be reached between the reviewer and the fabricator.
3. Electrical parameters:
a. Current and polarity (be aware of amperage limits per Table 5.10).
b. Number of electrodes and orientation.
c. Electrode extension.
d. Current, voltage and travel speed for each pass.
4. A709 Gr. 50W material considerations:
a. Check the MTR for percentage of carbon.
b. To use 50W material to qualify welding of grades 36, 50, 50S and 50W, the test plate must have a minimum 0.15% carbon (Clause 5.4.2) or a minimum carbon equivalent (CE) of 0.45% with the carbon not less than 0.12%.
c. If the 50W material does not meet the carbon requirements, the testing will qualify WPS’s for welding of 50W material only.
5. Verify PQR Documentation to be submitted with the WPS to the reviewer:
a. All information is included on the PQR form including items 1-4 above.
b. Maximum and minimum heat input is documented.
c. Welder identification.
d. All mechanical tests and NDT have been conducted and results documented including:
i. All weld-metal tension
ii. CVN
iii. Macroetch
iv. Visual examination
v. Reduced section tensile (if required)
vi. Side bend (if required)
vii. Fillet weld soundness test (if required)
viii. RT
ix. UT if required
e. Verify MTR’s are included for:
i. Plate material (remember the 0.12% carbon content rule)
ii. Backing bar (remember the 0.12% carbon content rule)
iii. Filler metal and flux
iv. Shielding gas

This is essentially all the inspector needs to be concerned with regarding the PQR. Whether or not the actual values and parameters are within acceptable tolerances is the concern of the reviewer.

FILLET WELDS

Under the 2015 Bridge Code, single pass fillet weld WPS’s may be qualified solely by performing a Fillet Weld Soundness Test (FWST). No longer does the fabricator have to run a groove weld qualification first. The FWST must be run within the range of parameters expected to be used in production and the WPS written within the limitations of variables in Table 5.4. The WPS heat input range is to be +/-20% of the calculated FWST heat input.

Multi-pass fillet welds must be qualified by performing a groove weld qualification test in accordance with 5.12 first, then performing a FWST. The FWST must be run using production parameters that fall within the allowable ranges of the groove weld PQR for current, voltage, travel speed, and heat input.

An FWST must be run for each fillet weld size and position for which a WPS needs to be written. Also, joints with a dihedral angle of more than 10° from normal require a FWST for each position and weld size (see Table 5.4(28) and Fig. 5.8).

WELDING PROCEDURE SPECIFICATION CONSIDERATIONS
1. WPSs are based on the results of the PQR and shall be written with parameters that fall within the limitations of the PQR and Clause 5.12 or Table 5.4 as applicable.
2. The WPS must be on a form that conveys all the necessary information. Some owners, such as Florida and Pennsylvania Departments of Transportation, require the use of specific forms.
3. WPSs must be submitted for review and must have the reviewer’s acceptance stamp on the form prior to commencing use of the WPS. Some states such as Florida and Pennsylvania also require the fabricator to have a CWI sign and stamp the form.
4. When the WPS requires an expiration date (i.e. for FCM), the expiration date is based on the date that the PQR plate was welded, not from the date the WPS was written. WPSs and PQRs that expire after production welding has commenced on a project will be valid until the project is complete.
5. The WPS must show a detail of the joint.
6. WPSs can be written for multiple types and grades of steel, provided they are all qualified by the same PQR.
7. WPSs can have more than one welding process listed, provided each process has been qualified independently of the other. The operating parameters must be clearly delineated for each process and pass; e.g. GMAW root pass – SAW fill passes.
8. WPS’s may be acceptable based on qualification testing performed for other owners, but they still need to be submitted and reviewed for acceptance by the owner of the current project.
9. The third-party inspector is not responsible for comparing the WPS to the PQR. That is the reviewer’s job. However, if the inspector sees something he or she does not think is correct, he should contact the reviewer.
10. If a correction or change to an essential variable is required, the WPS will need to be revised, and may need to be requalified. The revised WPS, with supporting documentation, must be resubmitted for review and approval.
11. If the inspector has any questions about an approved WPS, he should contact the reviewer.

As each edition of the Bridge Welding Code is published, more of the ambiguities and misperceptions are cleared out; however, it is a work in progress that has yet to reach perfection. This guideline is an attempt to clear up some of the remaining confusion encountered with the AASHTO/AWS D1.5 2015 Bridge Welding Code as it relates to WPS qualification. The third-party inspector is in a unique position to aid the fabricator in making sure that qualification testing is performed properly, and to aid the reviewer in making sure the proper documentation is submitted. Qualification testing is not inexpensive, so it is most beneficial to get it right the first time, and not have to unnecessarily repeat the testing process.

 

 

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