Visual Inspection of Steel pipes/ Plates

TRAINNING ON VISUAL

EXAMINATION OF STEEL

PRODUCTS

(Welded Pipes, Coils & Plates)

Contents

1.

General guideline for visual Inspection

2.

Visual Defects in Steel Plates & Coils

3.

Visual Defects in Welding

General guideline

for

Visual Inspection

Definition of Visual Inspection

Visual Inspection is the simplest, fastest, economical and most commonly used test for detecting defect on the surface of the weld and plate/pipe body.

Inspection may be carried out by the use of the eye alone or can be enhanced by using optical

systems such as magnifiers and other visual examination aids. A variety of equipments are

available for visual examination including mirrors, video scopes etc.

Conditions for visual inspection

Visual inspection shall 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, oil grease etc. Any equipment to be used should be calibrated and its operation should be understood by the inspector.

1.

Sufficient Illumination

2.

Correct eye distance from object and

correct angle between eye & object

3.

Magnifying glasses to be use if

required

Conditions for visual inspection

1.

Sufficient Illumination :

 At least 300 Lux as per API 5L, 45th edition

 At least 1000 Lux as per ASME Sec V/ API 5LD.

Conditions for visual inspection

Near Vision Examination

The applicant shall be 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 interpret an Ortho-Rater 8 or better or a similar test pattern is also acceptable. This test should be administered annually. Candidates must also be capable of differentiating different shades of colors - this color vision must be tested every 5 years.

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

General guideline for Visual

Inspection

2. Correct eye distance from object and

correct angle between eye & object :

Access and viewing distance

If unaided visual inspection is to be carried out accurately, observations must be made within 600 mm. (ASME Sec V, Article - 9)

Viewing angles and distances

The eye's resolving power is dependent on

the angle and distance from the test surface.

Direct visual examination observations may

usually be made within 600 mm of the

surface to be examined and and the angle

between the eye and test surface not less

than 30° (ASME Sec V Article 9).

MEASURING

EQUIPMENT

 Scale  Measuring Tapes  Vernier Calipers  Micrometers  Clock gauges  Pie Tape  Bevel Protector

 Bead Height Gauge

 Off Set Gauge

Measuring Equipments / Instruments

Visual Defects

in

Steels

 Sliver  Scab  Rolled-in-Scale  Roll Mark  Tong mark  Dents / Indentation  Pitting  Pit

Visual Defects in Steels

 Seam line  Lap  Lamination  Cracks  Arc Burn  Hard Spot  Excess Reinforcement  Under Cut

 Stretch Mill Indentation

+ + + And So many

Visual Defects in Steels

Sliver

An extremely thin elongated piece of

metal that has been rolled into the

surface of the parent metal to

which it is attached usually by only

one end.

Sliver

Visual Defects in Steels

Scab

An imperfection in the form of a

shell or veneer, generally attached

to the surface by sound metal. It

usually has its origin in an ingot

defect.

Scab

Visual Defects in Steels

Roll MARK

A term applied to surface

imperfections caused by improper

roll alignment or roll surface

damage.Such imperfections may be

periodic or continuous

Roll Mark

Roll Mark

Dents

A local change in surface contour

caused by mechanical impact, but not

accompanied by loss of metal.

Visual Defects in Steels

Pitting

. Pitting, is a form of extremely localized

corrosion that leads to the creation of small

holes in the metal.

Pitting

Pit

A depression resulting from the removal of

foreign material rolled into the surface

during manufacture.

Visual Defects in Steels

Seam

Crevice in rolled metal which has been more or

less closed by rolling or other work but has not

been fused into sound metal

Seam

Visual Defects in Steels

Cracks

A

stress-induced separation of the metal which,

without any other influence, is insufficient in

extent to cause complete rupture of the material.

Quench cracks in steel result from stresses

produced during the austenite-to martensite

transformation, which is accompanied by an

increase in volume

Cracks

Visual Defects

in

Pipes Body

(Due to Process and poor workmanship)

STRETCH MILL INDENTATION:

Localized thinning of the pipe body

wall - usually located on the inside

surface

EXCESSIVE REINFORCEMENT (EXCESSIVE OVERFILL):

prolongation of the original surface of the pipe (more than 1/8 in. for pipe having a thickness of 1/2 in. and under, and more than 3/16 in. for a pipe having a

thickness of over 1/2 in.

ARC BURNS:

Localized points of surface melting caused

by arcing between electrode or ground and pipe

surface.

 Improper Grinding  Deep Grinding  Roller Mark  Chip Mark  Scratches  Mechanical Damage

Visual Defects in Pipe Body

Improper Grinding

Deep Grinding

Chips Mark

Mechanical Damage

Chisel Marks Chisel Marks

Visual Defects

in

Weld

Visual Defects in Weld Under Cut:

Under-cutting on submerged-arc welded pipe is the reduction in thickness of the pipe wall adjacent to the weld where it is fused to the surface of the pipe

Visual Defects in Weld Porosity:

Voids in a metal, usually resulting from shrinkage or gas entrapment occurring during solidification of a casting or weldment

Visual Defects in Weld Under fill:

Visual Defects in Weld IR-REGULAR WELD:

Bead Out, Bead Bend ,Narrow Bead

Bead Out

Bead Bend

Visual Defects in Weld Crack:

A stress-induced separation of the metal which, without any other influence, is insufficient in extent to cause complete rupture of the material. Quench cracks in steel result from stresses produced during the austenite-to martensite transformation, which is accompanied by an increase in volume

Visual Defects

in

Coil

Visual Defects in Coil Telescopic:

Visual Defects in Coil Camber:

Visual Defects in Coil Fish Tail:

API 5L

45

th

EDITION

REQUIRMENTS

SURFACE CONDITIONS, IMPERFECTION AND DEFECTS

All pipes shall be free from defects in finished condition All pipes shall be free from cracks, sweats and leaks

UNDERCUT

 Undercuts in SAW pipes shall be investigated, classified, and treated as follows.

a) Undercuts that have a depth ≤ 0,4 mm (0.016 in) are acceptable, regardless of length, and shall be treated in accordance with Clause C.1.

b) Undercuts that have a depth > 0,4 mm (0.016 in) but ≤ 0,8 mm (0.031 in) are acceptable provided they are treated in accordance with Clause C.2 and provided that:

1) their individual lengths are ≤ 0,5 t,

2) their individual depths are ≤ 0,1 t, and

3) there are no more than two such undercuts in any 300 mm (12.0 in) length of weld.

ARC BURN



Arc burns shall be treated in accordance with Clause C.2, C.3 b) or C.3 c), except that they may be removed by

grinding, chipping or machining, provided that the resultant cavity is thoroughly cleaned and checked for complete

removal of damaged material by etching with a 10%

solution of ammonium persulfate or a 5% solution of nital.

LAMINATIONS

Lamination having visually determined length the

circumferential direction > 6.4mm shall be considered as defects

FLAT SPOTS AND PEAKING  3.2mm maximum in depth

Measured as the gap between the extreme point of the

deviation and the prolongation of the normal contour of the pipe, shall be considered defects and shall be

treated in accordance with C.3 b) or C.3 c).

HARD SPOT

Maximum 345 HV10 or 327 HBW in 50mm length in any direction shall be classified as a defect . Pipes that contain such defects shall be treated in accordance with C.3 b) or C.3 c).

OTHER DEFECTS

Maximum 0.125 x WT, but not exceed minimum wall

thickness. Pipes that contain such defects shall be treated in accordance with C.3

DENT

 For dents, the length in any direction shall be ≤ 0.5 D and the depth, measured as the gap between the extreme point of the dent and the prolongation of the normal contour of the pipe, shall not exceed the following:

a) 3,2 mm (0.125 in) for cold-formed dents with sharp-bottom gouges; b) 6,4 mm (0.250 in) for other dents.

Dents that exceed the specified limits shall be considered defects and shall be treated in accordance with C.3 b) or C.3 c).

STRAIGHTNESS

The total deviation from a straight line over the entire pipe length shall be ≤ 0,15 % of the pipe length. for sour service and/or offshore service

The total deviation from a straight line, over the entire pipe length, shall be ≤ 0,2 % of the pipe length For other than sour service or offshore service.

STRAIGHTNESS

The local deviation from a straight line in the 1,0 m (3.0 ft) portion at each pipe end shall be ≤ 3,0 mm (0.120 in) for sour service and/or offshore service.

The local deviation from a straight line in the 1,0 m (3.0 ft) portion at each pipe end shall be ≤ 4,0 mm (0.156 in). For other than sour service or offshore service

WALL THICKNESS

PIPE LENGTH

STRAIGHTNESS

OUT OF SQUARENESS:

PIPE ENDS

RADIAL OFFSET:

For SAW and COW pipes, the radial offset of the

strip/plate edges shall not exceed the applicable value given in Table

HEIGHT OF WELD BEAD

For ID weld Bead

At least 100 mm (4.0 in) from each pipe end.

Bead height removed by grinding such that it does not extend above the adjacent pipe surface by more than 0.5 mm.

For OD weld Bead If agreed,

At least 150 mm (6.0 in) from each pipe end.

Bead height removed by grinding such that it does not extend above the adjacent pipe surface by more than

0.5 mm (0.020 in).

HEIGHT OF WELD BEAD

For the remainder of the pipe, the inside weld bead and out side weld bead shall not extend above the adjacent pipe surface by more than the applicable value given in Table

MISALIGNMENT OF WELD BEAD

Complete fusion and penetration to be achieved Max. 3 mm for WT ≤ 20mm

Max. 4 mm for wt > 20mm

MESUREMENT OF PIPE LENGTH:

For convenience pipe length shall be measured from un-beveled end to un-beveled face.

Pipe Length

OUT OF ROUNDNESS:

The greatest distance from a surrounding circle of points on the actual cross-sectional profile of a cylindrical

surface

BEVEL ANGLE:

MASS

MASS

If the purchase order specifies a minus tolerance for wall thickness smaller than the applicable value given in Table 11, the plus tolerance for mass shall be increased by a percentage equivalent to the applicable percentage reduction of the minus tolerance for wall thickness.

For each order item with a mass of 18 tonnes (20 ton) or more, the mass of the order item shall not deviate from its nominal mass, determined by multiplying the

total length of pipe in the order item by its mass per unit length (as per above formula), by more than the

following:

a) for Grades L175, L175P, A25 and A25P: − 3,5 %; b) for all other grades: − 1,75 %.

Thank you