Purpose and Scope of Welding Inspection

Weld inspection is a technical evaluation performed to determine whether a welded joint (seam) meets design and standard requirements. The aim is to verify the integrity of the weld seam and to detect discontinuities early on that could affect the safety of load-bearing or compression-bearing structures.

This page specifically focuses on weld seam quality, welding procedures, and welder qualifications. A general explanation of non-destructive testing methods used in weld inspection, as well as equipment integrity and suitability for use (FFS) assessments such as API 510/570, are covered on separate pages on our website.

  • Verification of suture integrity and continuity.
  • Determining the type, size, and location of discontinuities (defects).
  • Linking welding procedure (WPS) and welder qualifications to records.
  • Evaluation of acceptance criteria according to the relevant standard/code.

Common Welding Defects

Welding discontinuities are divided into various types, each stemming from different causes and evaluated according to the acceptability limits defined within the relevant code. Whether a discontinuity is considered a defect (unacceptable) depends on the acceptance criteria in the applicable standard.

  • Cracks (including cold/hot cracks)
  • Pores (porosity) and gas voids
  • Slag residue (slag trap)
  • Lack of fusion
  • Lack of penetration
  • Burning groove (undercut) and profile defects

Relevant Standards and Scope

Weld inspection procedures and personnel qualifications are governed by different families of standards. The following distinction is to clarify which standard serves which purpose; it is important to emphasize that the standards are not interchangeable. For example, a welder qualified under ASME Section IX is not automatically qualified under AWS D1.1; vice versa.

  • AWS D1.1 (Structural Steel Welding Code): Covers the fabrication, assembly, and inspection of welded steel structures made from carbon and low-alloy steels. Typically used for structural steels 3 mm and thicker; allows for prequalified procedures for certain common connections. It is a US standard.
  • ASME BPVC Section IX (Boiler and Pressure Vessel Code, Part IX): Regulates welding and soldering procedures and the qualification of personnel (welder/operator). It is used in pressure-bearing equipment and does not accept pre-approved procedures; each WPS must be supported by a tested PQR. It is a US standard.
  • TS EN ISO 9606 (Welders' Qualification Test): Defines the requirements for the certification of welders performing fusion welding through examination. Widely used in the context of Türkiye and the EU.
  • TS EN ISO 15614 (Welding Procedure Qualification / WPQR): Regulates the test-based validation (WPQR) of welding procedures for metallic materials; it is used as a basis for the preparation of WPS together with TS EN ISO 15609.

Key Concepts: WPS, PQR/WPQR, and Welder Competency

Quality assurance in welded fabrication rests on three fundamental elements: an approved welding procedure, verification of this procedure through testing, and the competence of the welder performing the procedure. These concepts are defined with similar logic, but with different terminology and details, in both the ASME and EN ISO standard families.

  • WPS (Welding Procedure Specification): A written instruction defining parameters such as welding method, joint preparation, filler metal, current/voltage, position, and number of passes.
  • PQR / WPQR (Procedure Validation Record): A record showing that a WPS has been applied to actual test specimens and validated through destructive/non-destructive testing.
  • Welder Qualification: Proof, through examination, that a welder can perform welding of acceptable quality within a specific range of methods, material groups, and positions. According to TS EN ISO 9606-1, the certificate is generally valid for three years and requires periodic confirmation/renewal.

Inspection Methods and Acceptance Criteria Used in the Source

Various non-destructive testing methods are used in the evaluation of weld seams. The methods are listed here only; for the principles, application areas, and limitations of each method, please refer to the non-destructive testing page on our website.

Whether a seam is acceptable is determined by comparing the type, size, and location of the detected discontinuity to the acceptance criteria of the relevant code. Acceptance limits vary by code; for example, AWS D1.1, ASME BPVC Section IX, and TS EN ISO standard families may include different thresholds and evaluation approaches. Therefore, inspection should always be carried out with reference to the standard/specification applicable to the project.

  • Visual inspection (VT)
  • Liquid penetrant testing (PT)
  • Magnetic particle inspection (MT)
  • Radiographic examination (RT)
  • Ultrasonic examination (UT / phased array UT: PAUT)
  • For methodological principles, see our non-destructive testing page.

Areas of Application and the International Context with Türkiye/EU

Weld inspection and procedural/welder qualification assessments are commonly required in steel structures (structural steel), pressure vessel and pipe manufacturing, and industrial buildings. The applicable standard is determined according to the nature of the project and customer/specification requirements.

In Turkey and the EU context, standards such as TS EN ISO 9606 (welder) and TS EN ISO 15614 (procedure) are widely used. AWS D1.1 and ASME BPVC Section IX are US-originated standards and do not constitute mandatory legislation in Türkiye; however, evaluation according to these standards is frequently requested in export projects, multinational works, or as required by customer/main contractor specifications. Which standard will be applied should be clarified in the contract and specifications.

  • Steel structures and structural steel: often according to AWS D1.1 or EN standards.
  • Pressure vessel and piping manufacturing: often according to ASME BPVC Section IX or EN ISO 15614/9606
  • Industrial buildings and plant assembly.
  • Export/international project: May be required according to AWS/ASME specifications.

Information Note

This page is for informational purposes only and provides a general technical overview; standard selection, inspection plan, and acceptance criteria for a specific project should be evaluated separately in each case according to the relevant code and specification.

AES Innovation provides standard-referenced technical assessment and information on welding inspection and WPS/welder qualification; the results are presented as a technical report by an authorized engineer (mechanical engineer). AES's accreditation scope is limited to the 6.1 Electrical Installation area; the welding inspection and personnel/procedure qualifications described on this page are not covered by this accreditation. AES does not issue welder certificates or personnel certificates, nor does it provide accredited inspection or personnel certification services; welder and procedure certification is carried out by accredited and authorized certification bodies under TS EN ISO/IEC 17024.

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Frequently Asked Questions

What is WPS?

A WPS (Welding Procedure Specification) is a written instruction that defines how a weld should be performed. It includes parameters such as the welding method, joint preparation, filler metal, current/voltage values, weld position, and number of passes. The validity of a WPS is based on a PQR/WPQR record verified by experiment.

What is the difference between AWS D1.1 and ASME BPVC Section IX?

AWS D1.1 primarily covers the fabrication, assembly, and inspection of structural steel welded structures and allows for prequalified procedures for certain common connections. ASME BPVC Section IX, on the other hand, regulates welding/soldering procedures and personnel qualifications for pressure-bearing equipment and does not accept prequalified procedures; each WPS must be supported by a tested PQR. Qualification under one does not automatically validate the other.

Are AWS D1.1 and ASME standards mandatory in Türkiye?

AWS D1.1 and ASME BPVC Section IX are US-based standards and do not constitute mandatory legislation in Türkiye. In the Turkish/EU context, standards such as TS EN ISO 9606 and TS EN ISO 15614 are commonly used. AWS/ASME implementation is generally required for export, international projects, or customer specifications; which standard will be used is determined by contract.

How to get a welder's certificate?

A welder's qualification certificate (e.g., according to TS EN ISO 9606-1) is issued after successfully welding a test piece and passing the necessary inspections under the supervision of an authorized certification body accredited under TS EN ISO/IEC 17024. The certificate is generally valid for three years and requires periodic confirmation/renewal. AES does not issue this certificate; this process is carried out by authorized certification bodies.

When does a discontinuity count as a defect?

Not every discontinuity in the resource warrants rejection. Whether a discontinuity is considered an unacceptable defect is determined by comparing it to the acceptance criteria of the applicable code (e.g., AWS D1.1, ASME BPVC Section IX, or the relevant TS EN ISO standard) based on its type, size, and location. Acceptance limits vary depending on the code.

Does AES conduct this assessment?

AES Innovation provides standard-referenced technical assessment and information on welding inspection and WPS/welder qualifications, and communicates the results as a technical report by an authorized engineer (mechanical engineer). However, AES does not provide accredited inspection or personnel certification services, nor does it issue welder certificates/personnel certifications; AES's accreditation is limited only to the 6.1 Electrical Installation field.