welding & pipe inspection training manual

TRAINNING ON VISUAL

INSPECTION

ContentsContents

1. General guideline for visual Inspection

2. Visual Defects in Steel

3. Visual Defects in Welding

General guideline for

Visual Inspection

Definition of Visual Inspection

Visual inspection is the monitoring of specific parameters by visual and optical assessments of test objects and surfaces.

Inspection may be by the use of the eye alone or can be enhanced using optical systems such as magnifiers and microscopes. A variety of equipment is available to the visual inspector including mirrors and gauges.

Conditions for visual inspection

Visual inspection must take place in a clean, comfortable environment with adequate lighting. There should be reasonable access to the parts to be inspected and attention should be paid to safety, working position, and atmospheric conditions. The test piece should be clean and free from protective coatings. Any equipment to be used should be checked for accuracy and its operation understood by the inspector.

1.Sufficient Illumination2.Correct eye distance from object

and correct angle between eye & object

3.Mirror, magnifying glasses to use if required

General guideline for Visual Inspection

1. Sufficient Illumination :

No vision without illumination At least 300 lux as per API 5L, 44th

edition At least 1000 lux as per ASME Sec V

General guideline for Visual Inspection

Near Vision Examination

The applicant is capable of reading a minimum of Jaeger No.2 or equivalent type and size of letter at a distance of not less than 12 inches on a standard Jaeger test chart. The ability to perceive an Ortho-Rater minimum of 8 or a similar test pattern is also acceptable. This test should he administered annually. Candidates must also he capable of differentiating different shades of colors - this color vision must be tested every 3 years.

This is specified in ASNT document number SNT-TC-1A.

Viewing angles and distances

It is recommended that direct vision testing should be carried out between 250 mm and 600mm and the angle between the eye and test surface not less than 30°.

Rules Thin steel rules are used by the visual

inspector for accuracy, i.e. less parallax error, good dimensional stability and small width of graticules. Measurement markings may he metric, imperial or both. The smallest increment is usually 0.5 mm or 1/64 inch.

Visual Defects in

Steels

Arc Burns Blister Cracks Dents Hard Spot Inclusion Lamination Tong mark

Visual Defects in Steels

Lap Pitting Roll Mark Rolled-in-Scale Scab Seam Sliver Seam line

+ + + And So many


Arc Burn

Localized point of the surface melting caused by the arcing between electrode/ground and pipe surface

Arc burnArc burn


Blistering

A raised spot on the plate surface caused by the pocketing of the gas within the plate wall

BlisteringBlistering


Cracks

Internal ruptures in steel caused by stresses which arise

from the combination of several factors, such as volume

changes due to transformation, brittleness due to the

presence of hydrogen, and the arrangement of the micro-

structure, resulting from hot working.

Cracks


Dents

A local change in the surface contour caused by mechanical impact, but not accompanied by the material loss.

DentDent


Hard Spot

Area of the pipe having hardness level considerably high as compare with surrounding metal usually due to localized quenching.


Gauge mark

Elongated grooves or cavities caused by removal of metal

Gauge MarkGauge Mark

Chisel MarksChisel Marks


Inclusion

Foreign material or non metallic particle entrapped within the metal during solidification

InclusionsInclusions

InclusionInclusion


LaminationInternal metal separation creating layers

generally parallel to surface

LaminationLamination


LapFold of metal which has been rolled or otherwise

worked against the surface of the rolled metal , but has not fused into sound metal

LapLap


PittingDepression resulting from the removal of foreign

material rolled into the surface during the manufacture.

And

Depression resulting from impression of foreign material into the plate surface during the manufacturing.

Pitting


Roll MarkA term applied to the surface imperfection

caused by improper rolled alignment or roll surface damage.

Roll Mark


Roll in-slugA term applied to the surface imperfection

caused by improper rolled alignment or roll surface damage.

Roll In-Slugs


SliverA extremely thin elongated piece of metal that has been

rolled into the surface of the parent metal to which it is attached usually by the one end.

Sliver is caused by the poor rolling mill practices, billet defects, improper biller conditioning, high rolling speed etc

Sliver


ScabImperfection in the form of a shell, generally attached to

the surface by sound metal.

Scabs are irregularly shaped, flattened protrusions caused by splash, boiling or other problems from teeming, casting, or conditioning


Seam

Crevice in the rolled metal which has been more or less closed by rolling or other work but has not been fused into sound metal.

Visual Defects in

Pipes Body(Due to Process and poor workmanship)

Improper GrindingImproper Grinding

Deep GrindingDeep Grinding

Chips MarkChips Mark

Visual Defects in

Welding

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welding & pipe inspection training manual

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