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Visual Inspection of Weld

Visual inspection, or visual testing (VT), is the primary and required method for inspecting welds according to welding codes. VT should always be performed before other non-destructive evaluation methods to identify any discontinuities on the weld surface. If other methods like radiographic testing are used without first doing VT, it requires extra time and cost to go back and inspect the weld surface if discontinuities are found. VT can be used to inspect welds before, during, and after welding to check for issues with the joint configuration, welding process, and surface discontinuities. Proper tools and knowledge of limitations are important for effective VT.

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576 views1 page

Visual Inspection of Weld

Visual inspection, or visual testing (VT), is the primary and required method for inspecting welds according to welding codes. VT should always be performed before other non-destructive evaluation methods to identify any discontinuities on the weld surface. If other methods like radiographic testing are used without first doing VT, it requires extra time and cost to go back and inspect the weld surface if discontinuities are found. VT can be used to inspect welds before, during, and after welding to check for issues with the joint configuration, welding process, and surface discontinuities. Proper tools and knowledge of limitations are important for effective VT.

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fallalovaldes
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just

the facts The First Step: Visual Inspection of Welds


BY LYNDSEY DECKARD
The terms visual examination and visual testing are used interchangeably for the visual method of testing or inspection (VT). As identified in D1.1: 2004, Structural Welding Code Steel, Sections 6.9, 6.10, and 6.11, VT is the prerequisite inspection method required to be used for welds prior to investing the time and effort in other methods. If a weld cannot pass VT, no further nondestructive evaluation (NDE) methods should be applied until the VT discontinuities are corrected and accepted. Visual testing is, generally speaking, the fastest and most economical method of NDE. I have seen instances where VT was skipped and the required radiographic testing (RT) was performed first because the visual inspector was busy at another location at the time. When this occurs, the RT films will indicate any existing discontinuities on the surface. It then becomes necessary to go back to the weld (sometimes in a very difficult-to-access location on a bridge or other structure) to prove the indication is actually on the surface, grind it out, possibly repair weld, and RT again to verify the interior of the weld. The added cost in time and equipment in these cases should have been avoided by performing VT initially. Visual inspection or visual testing is a reliable weld inspection method that should be applied to all welds. Like all other NDE methods, VT has specific limitations. Knowledge of the limitations is critical to the effective application of any inspection method. There are three important times to employ VT during welding: Prior to welding, visual inspection of the joint configuration and its compliance with the weld procedure specification (WPS) should be verified. During the welding process, proper weld pass cleaning, interpass temperature, and maximum width can be confirmed visually. After welding, VT can identify discontinuities on the weld surface. The welding inspector should never begin any inspection without his/her basic tools. At a minimum these include a light source, applicable weld gauges (i.e., fillet, hi-lo, undercut), a steel tape, the WPS, and access to the contract specification and the applicable welding code. Also required are corrective lenses if indicated on the inspectors latest visual acuity record. Some of the more common surface discontinuities to be found by careful visual inspection are shown in Figs. 1 and 2.O

LEGEND: 1. CRATER CRACK 2. FACE CRACK 3. HEAT-AFFECTED-ZONE CRACK 4. LAMELLAR TEAR 5. LONGITUDINAL CRACK 6. ROOT CRACK 7. ROOT SURFACE CRACK 8. THROAT CRACK 9. TOE CRACK 10. TRANSVERSE CRACK 11. UNDERBEAD CRACK 12. WELD INTERFACE CRACK 13. WELD METAL CRACK

Fig. 1 Types of weld discontinuities.

Fig. 2 Types of cracks. (Note: No. 4, lamellar tear, cannot be detected with VT.)

Excerpted from AWS A3.0:2001, Standard Welding Terms and Definitions. LYNDSEY DECKARD (Deckard@pbworld.com) is Quality Manager of the Vehicle Division of Parsons Brinckerhoff Transit & Rail Systems Inc. He is an AWS Senior Certified Welding Inspector, an ASQ Certified Quality Auditor, and a member of the AWS Certification Committee, the Examination Question Bank Subcommittee, and chairman of the Ethics Subcommittee. 38 INSPECTION TRENDS

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