MIL-STD-3040A: In-Process Welding Inspection

bginnard
2 days ago
3 min read

A Technical Requirement - Not A Best Practice

(Need To Know Article: 5 of 7)

In military fabrication, adherence to specification isn't just about quality—it's about performance, safety, and mission success. For weld engineers and quality assurance personnel responsible for compliance under MIL-STD-3040A, one of the most essential (and sometimes overlooked) requirements is the execution and documentation of ongoing and in-process welding inspections.

In-Process Inspection: A Core Requirement Under the Standard

In-process inspection under MIL-STD-3040A can take two primary forms

1. Required NDT (Nondestructive Testing) inspection

2. Conformance with applicable WPS documentation

Section 5.9.1 Nondestructive testing (NDT) requirements outlines the ongoing inspection requirements under MIL-STD-3040A to detect the presence of weld discontinuities. In addition to the inspection method types by weld class shown in table XXI below, this military standard also provides details about required NDT practices such as:

· NDT written instructions

o Must be certified by an applicable NDT Level III inspector

· Hold time prior to NDT inspection for certain base materials

· Surface preparation

· Frequency of NDT examination

o All welds shall be visually inspected at 100% frequency without deviation.

· NDT examination reporting requirements

Integration with Welding Procedure Specifications (WPS)

In-process inspection goes hand-in-hand with the WPS. MIL-STD-3040A’s Section 4.2.2 emphasizes that all production welding must adhere to a qualified WPS, and it’s up to the engineer or quality personnel to verify that welders and inspectors are referencing the correct procedures. Deviations—such as use of unapproved techniques or filler materials—must be documented and addressed via corrective action protocols.

Section 5.10.2 of MIL-STD-3040A is clear about the need for in-process checks of adherence to and conformance with the approved WPS:

“The entity shall have an established system to ensure that the supervision of any welder or welding operator properly applies the parameters of the applicable WPS to any fabrication done in accordance with this document.”

This isn't a suggestion—it's a directive that applies across all fabrication activities subject to this standard.

The purpose is twofold:

Ensure process control – Variables such as preheat/interpass temperature, joint cleanliness, filler material traceability, and weld bead geometry must remain within WPS limits.
Enable early detection – Discontinuities such as arc strikes, undercut, or incomplete fusion can often be caught during the weld process, not just afterward.

The weld engineer or quality assurance personnel are responsible for defining and documenting the means and methods of monitoring these variables, ensuring that inspection criteria align with approved WPSs and are clearly communicated to weld inspectors and supervisors.

Section 5.10.2 states that the frequency and percentage of workforce checks shall be “pragmatic and prudent as fits the entity’s ability to have and prove reassurance that WPS’s are being adhered to.” In other words, this WPS check routine is required, but not specifically defined by the specification, so military fabricators need to determine their own best practices to meet this requirement.

The Documentation Imperative

Per Section 5.5.1, inspection results must be recorded. The standard requires that:

“Welds shall be inspected during fabrication and after completion, and inspection records shall be maintained as part of the weld documentation package.”

This includes:

In-process inspection logs
Personnel qualifications (inspectors and welders)
- Per Section 5.8.2: “Certified visual inspectors (CVI) and authorized visual inspectors (AVI) shall be used for visual verification of weld quality”
- All NDT personnel must be qualified and certified in accordance with ANSI/ASNT CP-189 or AIA/NAS NAS410 and a certified NDT Level III inspector shall be responsible for the validity of the examinations and overall personnel qualification and certification.
Environmental monitoring data (e.g., ambient and preheat temps)
Verification of critical variables (CVs and EVs) identified per Table I of the standard

In short, engineers and quality personnel must develop an inspection framework that is not only technically sound but audit-ready.

Engineering Takeaways

For weld engineers supporting MIL-STD-3040A programs, in-process inspection is not simply a QA/QC activity—it’s a critical engineering control. It ensures weld quality, maintains traceability, and provides the defense program office with confidence that contract and technical requirements are being met.

Our team at United Technical Inc. can help military fabricators meet these in-process inspection requirements in multiple ways such as:

· Providing qualified and certified NDT inspection personnel including Level III inspectors

· Training welders, supervisors and inspectors

· Developing control plans for WPS verification

· Assisting fabricators with document traceability and retention

· Providing mock-audits to test QA systems