Welding Inspection NDT Visual Inspection

Abstract

Visual Inspection of Welded Connections

How To Inspect Welded Connections?

What Is Visual Inspection of Welded Connections?

Visual inspection is a non-destructive testing (NDT) weld quality check process. During the testing method, the weld is examined visually through the eyes to determine surface discontinuities. The process must be conducted by an experienced welding inspector. Visual inspection of welded connections is the most common weld quality testing methods. This type of inspection is probably the most underrated and often misused, method of welding inspection. Advantages of Visual Inspection

Visual inspection of welding can often be the easiest to perform and is usually the least expensive to conduct.

The welding inspection function is often divided into the below three areas:

First, and often the least utilized, is pre-weld inspection. This type of inspection can often provide us the opportunity to detect and correct unacceptable conditions before they develop into actual welding problems.

Second, inspection during the welding operation can often prevent problems in the completed weld through verification of the welding conditions and procedural requirements

Third, post-weld visual inspection is a relatively easy method of conducting completed weld quality evaluation.

Pre-Weld Inspection

This inspection is conducted prior to the start of the welding operation. This type of inspection is typically associated with checking the preparation of the welding joint and verification of parameters that would be difficult or impossible to confirm during or after welding procedure. This is the area of inspection where we can best introduce controls that may prevent defective welding.

Some areas of pre-weld inspection are joint preparation inspection/pre-weld setup. This may involve the dimensional inspection of root openings. Root openings that are too tight can cause inadequate root penetration. Root openings that are too large can cause over- penetration. Groove weld bevel angles, if too small, may cause a lack of fusion. If too large, can result in distortion of the weld joint from overheating and excessive shrinkage stress.

Joint alignment (misalignment of the weld joint) can result in difficulty in producing a sound weld and stress concentration at its location, resulting in a reduction of fatigue life. Plate surface condition and cleanliness, pre-cleaning prior to welding, can often be of extreme importance. Improper or inadequate cleaning can result in unacceptable levels of porosity in the completed weld. Other pre-weld inspections may include preheat verification, temperature and heating method, presence and location of heat treatment monitoring devices, and type and efficacy of gas purging, if applicable.

Inspection During Welding

This is the inspection that is carried out during the welding operation and is concerned mainly with the requirements of the welding procedure specification (WPS). This inspection includes such items as interpass cleaning methods, interpass temperature control, welding current settings, welding travel speed, shielding gas type, gas flow rate, and welding sequence, if applicable. Also, any environmental conditions that may affect the quality of the weld such as, rain, wind, and extreme temperatures.

Post-Weld Inspection

This inspection is typically conducted to verify the integrity of the completed weld. Many non-destructive testing (NDT) methods are used for post-weld inspection. However, even if the weld is to be subjected to NDT, it is normally wise to conduct a visual inspection first. One reason for this is surface discontinuities, which may be detected by visual inspection, can sometimes cause misinterpretation of NDT results or disguise other discontinuities within the body of the weld. The most common welding discontinuities found during the visual inspection are conditions such as undersized welds, undercut, overlap, surface cracking, surface porosity, underfill, incomplete root penetration, excessive root penetration, burn through, and excessive reinforcement.

Keywords: welding, Petroleum industry, pipeline