Visual Testing of Welds and Components, Direct and Remote

Visual testing is the oldest non-destructive method and still the one that finds the most defects. It is applied to almost every product as a quality assurance step, and the discontinuities it detects, those breaking the surface, are the ones most likely to propagate in service. itmad provides formal visual testing of welds, castings and components to ASME V Article 9, ISO 17637 and AWS D1.1, including remote and borescope examination, by ISO 9712 qualified inspectors. itmad operates across the Middle East, Asia and Europe. Last reviewed: October 2026.

More than looking

Visual testing is also the method most often done badly, because everyone assumes they can do it. Formal visual testing is a procedure with defined lighting, viewing distance, angle, surface preparation and acceptance criteria, carried out by a qualified inspector and recorded, which is a different activity from looking at a weld.

Techniques

In direct visual testing, the eye is within about 600 mm of the surface and at an angle of not less than 30 degrees, with illumination at the level that the standard specifies, and magnification and measuring aids are used as the acceptance criteria require. Remote visual testing uses borescopes, videoscopes and camera systems where the surface cannot be reached: internal bores, vessel interiors, confined spaces and areas that would otherwise need scaffolding or entry. Translucent visual testing is applied to translucent materials where light transmission reveals internal condition, and weld measurement uses weld gauges, fillet gauges and undercut gauges to verify profile, leg length, throat, reinforcement and undercut against the code limits.

What visual testing finds

Surface cracking in the weld, the heat-affected zone and the parent material; undercut, overlap and incorrect weld profile; surface porosity, blowholes and exposed slag; incomplete fill, excess reinforcement and incorrect leg length; arc strikes and weld spatter; misalignment, distortion and incorrect fit-up; corrosion, pitting, erosion and mechanical damage; incorrect or missing identification and marking; and surface condition that prevents valid examination by other methods.

Before, during and after welding

The value of visual examination depends largely on when it happens. Before welding, it verifies material identification, edge preparation, fit-up, root gap, alignment and cleanliness, and defects caught at this stage cost nothing to correct. During welding, it covers interpass cleaning, interpass profile and the condition of each run before the next one buries it, and after welding, it assesses the completed weld against the acceptance criteria. Most visual inspection is commissioned only for the last of those three, which means that preventable problems are found when they are expensive.

Conditions and their verification

A visual examination is valid only under the conditions that the standard specifies. Illumination at the surface is measured and not judged, and the level required rises where fine detail matters, viewing distance and angle are controlled, and the surface condition must permit examination, since scale, spatter, paint and dirt invalidate the result. Inspector vision is verified periodically, including near vision acuity.

Standards applied

ASME Boiler and Pressure Vessel Code Section V, Article 9, covers visual examination, with acceptance to the relevant construction code section, and ISO 17637 covers visual testing of fusion-welded joints. AWS D1.1 applies for structural steel welding and API 650, 653 and 510 where tank and vessel inspection codes govern, together with client, project and manufacturer specifications where they are more stringent.

The gate for other methods

Visual examination precedes and conditions every other NDT method. A surface that fails visual acceptance cannot be validly examined by penetrant, magnetic particle or ultrasonic testing: contamination blocks penetrant, spatter produces false magnetic particle indications, and poor surface condition prevents ultrasonic coupling. Where visual examination identifies a surface that must be prepared before the specified method can proceed, that is reported so that the preparation can be done first.

Personnel

Examination is carried out by inspectors qualified to ISO 9712 and ASNT SNT-TC-1A Level II, with CSWIP or AWS CWI welding inspection qualification where the work requires it, under Level III oversight.

What the client receives

A report identifying each item examined by weld number, part or drawing reference, with the technique applied, the illumination level, the viewing distance and any aids used. Findings are recorded with location, dimension and character, supported by photographs, and measurements are given against the code limits where profile or dimension is the criterion. The report assesses the findings against the acceptance criteria in the specification and includes the inspector's qualification and current vision verification record.

Frequently asked questions

What is formal visual testing?

A procedure with defined lighting, viewing distance, angle, surface preparation and acceptance criteria, carried out by a qualified inspector and recorded. It is a different activity from simply looking at a weld.

What techniques does visual testing use?

Direct visual with the eye within about 600 mm and at an angle of at least 30 degrees, remote visual with borescopes and camera systems, translucent visual, and weld measurement with gauges. Measuring aids are used as the acceptance criteria require.

When is visual testing most valuable?

Before and during welding as well as after it. Before welding it catches fit-up, root gap and cleanliness problems at no cost to correct, and most inspection is only commissioned for the completed weld, when problems are expensive.

Why does visual testing come before other NDT methods?

A surface that fails visual acceptance cannot be validly examined by penetrant, magnetic particle or ultrasonic testing. Contamination blocks penetrant, spatter gives false magnetic particle indications, and poor surface condition prevents ultrasonic coupling.

Which standards apply?

ASME Section V Article 9, ISO 17637 and AWS D1.1, with API 650, 653 and 510 where tank and vessel inspection codes govern. Client and project specifications apply where they are more stringent.

How are inspection conditions verified?

Illumination at the surface is measured and not judged, viewing distance and angle are controlled, and the surface must be fit for examination. Inspector vision, including near vision acuity, is verified periodically and recorded.