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Visual & Optical Testing (VT) of Welded Joints

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Module 1 of 4 12 min read

Weld Terminology & Joint Geometry

💬 In Plain Terms: The anatomy of a weld seam: how joints are prepped and glued together with molten metal
Everyday Analogy (How to Picture This)

Think of welding like hot-gluing two heavy pieces of metal together. If you just touch the flat edges and glue the surface, it snaps off easily. That's why welders grind bevel angles (V-grooves) so the liquid metal penetrates all the way through. As a visual inspector, your job is checking the joint before, during, and after welding.

Engineering Principles & Technical Theory

1. Anatomy of Groove & Fillet Welds

Groove Welds: Welds made in a groove between two members (Single-V, Double-V, J-groove, U-groove). Crucial dimensions: Root Face (flat land), Root Opening (gap), Bevel Angle (e.g. 30°), Included Angle (e.g. 60°).

Fillet Welds: Welds of roughly triangular cross-section joining two surfaces at right angles (T-joints, lap joints). Crucial dimensions: Leg Length, Theoretical Throat, and Effective Throat.

Step-by-Step Practical Field Procedure

1

Pre-Weld Fit-Up Inspection

Ref: AWS D1.1 Clause 5.22

Check root gap with tapered wire gauge (standard 2.5 mm to 3.5 mm). Verify bevel angle is within ±2.5° of WPS specification.

Target Defect Identification & Morphology

Root Gap Too Wide / Narrow

Critical / Reject

💬 Pipes pushed too close or spread too far apart before welding.

Instrument Signature: Narrow gap causes incomplete penetration; excessive gap causes burn-through.
Key Concepts to Memorize for Exams
✓Fit-up inspection prevents 70% of weld defects before arc strike.
✓Included angle equals both bevel angles combined (e.g. 30° + 30° = 60°).

Module Knowledge-Check Quiz

Question 1: What is the dimension of the flat face left on a beveled plate edge called?
Module 1 of 4