7/29/2019 Visual Inspection of Weld

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just

the facts

The terms visual examination andvisual testing are used interchangeablyfor the visual method of testing or inspec-

tion (VT). As identified in D1.1: 2004,Structural Welding Code Steel,Sections 6.9, 6.10, and 6.11, VT is the pre-requisite inspection method required tobe used for welds prior to investing the

time and effort in other methods. If aweld cannot pass VT, no further nonde-structive evaluation (NDE) methodsshould be applied until the VT disconti-

nuities 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 radi-ographic testing (RT) was performedfirst because the visual inspector was

busy at another location at the time.When this occurs, the RT films will indi-

cate any existing discontinuities on thesurface. It then becomes necessary to goback to the weld (sometimes in a very

difficult-to-access location on a bridge orother structure) to prove the indicationis actually on the surface, grind it out,possibly repair weld, and RT again to ver-ify the interior of the weld. The added

cost in time and equipment in thesecases should have been avoided by per-forming VT initially.

Visual inspection or visual testing is a

reliable weld inspection method thatshould be applied to all welds. Like allother NDE methods, VT has specific lim-

itations. Knowledge of the limitations is

critical to the effective application of anyinspection method.There are three important times to

employ VT during welding: Prior to weld-ing, visual inspection of the joint configu-

ration and its compliance with the weldprocedure specification (WPS) should beverified. During the welding process,

proper weld pass cleaning, interpass tem-perature, and maximum width can beconfirmed visually. After welding, VT canidentify discontinuities on the weldsurface.

The welding inspector should neverbegin any inspection without his/herbasic tools. At a minimum these includea light source, applicable weld gauges

(i.e., fillet, hi-lo, undercut), a steel tape,the WPS, and access to the contract spec-ification and the applicable welding code.

Also required are corrective lenses if

indicated on the inspectors latest visualacuity record.Some of the more common surface dis-

continuities to be found by careful visualinspection are shown in Figs. 1 and 2.O

The First Step: Visual Inspection of Welds

BY LYNDSEY DECKARD

LYNDSEY DECKARD (Deckard@pbworld.com) is Quality Manager of the Vehicle Division of Parsons Brinckerhof f Transit & Rail

Systems Inc. He is an AWS Senior Certified Welding Inspector, an ASQ Certified Quality Auditor, and a member of the AWSCertification Committee, the Examination Question Bank Subcommittee, and chairman of the Ethics Subcommittee.

38 INSPECTION TRENDS

Excerpted from AWS A3.0:2001, Standard Welding Terms and Definitions.

Fig. 1 Types of weld discontinuities. Fig. 2 Types of cracks. (Note: No. 4,lamellar tear, cannot be detected with VT.)

LEGEND:

1. CRATER CRACK2. FACE CRACK3. HEAT-AFFECTED-ZONE CRACK4. LAMELLAR TEAR5. LONGITUDINAL CRACK6. ROOT CRACK7. ROOT SURFACE CRACK

8. THROAT CRACK9. TOE CRACK10. TRANSVERSE CRACK11. UNDERBEAD CRACK12. WELD INTERFACE CRACK13. WELD METAL CRACK