Visual Testing

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VISUAL TESTING

• COMPILED BY ZAHEER SAJID
• OCTOBER 31, 2016 Revision-0
• NOT FOR COMMERCIAL USE

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CONTENT
SLIDE-3 WHY TEST SLIDE-4 WHEN TO
TEST SLIDE-5 QUALITY INSPECTION SLIDE -6 NON
DESTRUCTIVE INSPECTION SLIDE-7 BASIC NDT
TECHNIQUES SLIDE-8 MATERIAL APPLICABLE NDT
METHODS SLIDE-9 COST COMPARISION OF VARIOUS NDT
METHODS SLIDE-10 INTRODUCTION TO VISUAL TESTING
(VT) SLIDE-11 CLASSIFICATION SLIDE-12 APPLICATIO
N SLIDE-13 BASIC REQUIREMENT SLIDE-14 ATTRIBUTES
SLIDE-15 LIMITATION SLIDE-16 DEFECT SLIDE-17 S
URFACE DEFECTS SLIDE-18 STANDARDS SLIDE-19 ASME
REQUIREMENTS (GENERAL) SLIDE-20 ASME
REQUIREMENTS (SPECIFIC) SLIDE-21 BS
REQUIREMENTS SLIDE-22 BS REQUIREMENTS SLIDE-23 O
PTICAL SYSTEMS / TOOLS SLIDE-24 WELDING
DEFECTS SLIDE-25 FABRICATION / INSTALLATION
TOLERANCES SLIDE-26 FABRICATION / INSTALLATION
TOLERANCES SLIDE-27 DEFECTS (ROLLING, FORGING
PAINTING) SLIDE-28 AFTERWORDS
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WHY TEST
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WHEN TO TEST
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QUALITY INSPECTION
Quality Is defined as the fitness of the
product to do the job required if it by the
user. A modern definition of quality derives
from famous Juran's "fitness for intended use." 
This definition basically says that quality is
"meeting or exceeding customer expectations." 
Deming states that the customer's definition of
quality is the only one that matters. In other
words Quality means conformance to requirements.
QA/QC is the combination of QUALITY ASSURANCE,
the process or set of processes used to measure
and assure the quality of a product, and QUALITY
CONTROL, the process of meeting products and
services to consumer expectations.
QA for short, refers to a program for the
systematic monitoring and evaluation of the
various aspects of a project, service, or
facility to ensure that standards of quality are
being met. QC emphasizes testing of products to
uncover defects, and reporting to management who
make the decision to allow or deny the release,
whereas QA attempts to improve and stabilize
production, and associated processes, to avoid,
or at least minimize the defects.
An inspection is, most generally, an organized
examination or formal evaluation exercise. In
engineering activities inspection involves the
measurements, tests, and gauges applied to
certain characteristics in regard to an object or
activity. The results are usually compared to
specified requirements and standards for
determining whether the item or activity is in
line with these targets, often with a Standard
Inspection Procedure in place to ensure
consistent checking. Inspections are usually
non-destructive
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NON DESTRUCTIVE INSPECTION
Non-destructive testing (NDT) is a wide group of
analysis techniques used in science and industry
to evaluate the properties of a material,
component or system without causing damage.
The terms Nondestructive examination (NDE),
Nondestructive inspection (NDI), and
Nondestructive evaluation (NDE) are also commonly
used interchangeably to describe this technology.
However, technically, NDE is used to describe
measurements that are more quantitative in
nature. For example, an NDE method would not only
locate a defect, but it would also be used to
measure something about that defect such as its
size, shape, and orientation
It is important that NDT personnel have good near
visual acuity and color vision. Therefore, an eye
test must be taken to insure that natural or
corrected near distance acuity is acceptable.
Depending on which specification the company uses
for certification, an individual must be able to
read a Jaeger Number 1 (or equivalent) type and
size letter at no less than 12 inches (for one
eye). Determining contrast of color or shades of
gray is also generally required.
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BASIC NDT TECHNIQUES
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MATERIAL APPLICABLE NDT METHODS
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COST COMPARISION OF VARIOUS NDT METHODS
A LOWEST D HIGHEST
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INTRODUCTION TO VISUAL TESTING (VT)
VISUAL TESTING (VT) also know as Visual
Inspection, is the 1st. Inspection to perform
and can be applied at any stage. It is the most
widely used, oldest and reliable, quickest
NDT method used extensively to evaluate the
condition or the quality of an item. 
Visual inspection (abbreviated VT) by the
American Society for Non-destructive Testing
(ASNT) This test method is applied to almost
every product as a quality assurance tool. It is
easily carried out, inexpensive and usually
doesnt require any special equipment. It is a
most cost effective exercise and can be used to
identify areas that require further NDT
applications. It is also a fact that all defects
found by other NDT methods ultimately must be
substantiated by visual inspection. Time has
proved that visual inspection is the most
effective technique of all. Other techniques can
be employed if and when the welds or parts to be
examined are considered visually acceptable to
specification requirements.
Visual Testing may be carried out by eye alone,
this is called DIRECT INSPECTION Can be
enhanced by the use of optical systems, this is
called INDIRECT INSPECTION.
A variety of equipment/tools is available
including Magnifiers, Microscopes.  Mirrors,
Gauges, Fiberscope, Borescopes, Endoscopes,
Robotic crawlers, Camera, Video / Computer
enhancement systems
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CLASSIFICATION
Direct Visual Testing Simplified analysis of the
direct visual test sequence allows us to consider
individual stages. This process of consideration
is vital in procurement of successful test
procedures. A prime consideration is to that of
light. Surface finish, profile, color, contrast
and nature of inspection dictate the necessary
illumination for adequate reflected energy to
reach the eye. Codes and standards cannot
adequately address all combinations of surface
reflectivity or contrast and they only offer
basic guidance with rudimentary mandates on
minimum values. Visual acuity and adaptation
control the ability to receive quality images on
the retina whilst mental preparation, past
experience and educated knowledge facilitate
perception. Physical fatigue contributes to
misperception, therefore careful consideration of
work cycles should not be excluded when planning
visual tests. Concise written instructions or
criteria can be used to aid the application of a
technique improving probability of detection and
assisting reliable interpretation
Indirect Visual Testing Indirect / Remote visual
testing combines many facets of direct visual
testing with simple or complex imaging devices.
The same features that dominate direct visual
tests affect light reflected from the test
surface in the form of luminous flux. However
during remote visual testing the eye is separated
from receiving unimpeded visual information by a
series of optical or imaging devices. Lenses are
used to focus luminous energy onto optical or
imaging devices within the test system. In turn
an imaging device or camera transfers data to a
processor before formatting it into a visual
display. Only then do we return to the full
sequence of direct visual testing thus
compounding sources of image transfer error prior
to reliance of human perception and
interpretation. Consideration has also to be
given to the variety of applications the visual
tester is frequently expected to perform. Such
tests are not only in the form of nondestructive
observations, but often require scrutiny of
destructive test coupons analysis of fracture
surfaces from component failures.
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APPLICATION
This process often eliminates the need for
further types of testing. Some of the industries
that use VT include structural steel, automotive,
petrochemical, power generation, and aerospace.
According to a report from the U.S. Department of
Transportation Federal Aviation Administration,
Visual Inspection Research Project Report on
Benchmark Inspections, "Visual inspection is the
process of examination and evaluation of systems
and components by use of human sensory systems
aided only by mechanical enhancements to sensory
input such as magnifiers, dental picks,
stethoscopes, and the like. The inspection
process may be done using such behaviors as
looking, listening, feeling, smelling, shaking,
and twisting. "It includes a cognitive component
wherein observations are correlated with
knowledge of structure and with descriptions and
diagrams from service literature.
As specifications and tolerances become closer,
mechanical and optical aids can help improve the
precision of an inspectors vision.

• Despite the advancement in NDT technology, visual
  testing will continue to be a technique many
  industries rely on to ensure that the highest
  quality examination takes place.

APPLICATION OF VT INCLUDES Checking Of Surface
Condition OF Component, Alignment Of Mating
Surfaces, Color/Size/ Quantity/function/ Shape
Of The Component, Evidence Of Leaking,
Internal Side Defects Etc.
OTHER NDT METHODS RELY ON VT Even though a
component is to be inspected by using other
testing methods, it is given a good VT. Other NDT
methods require visual intervention to interpret
images obtained while carrying out the
examination. At some point, all NDT methods fall
back on VT. Liquid penetrant testing, for
example, uses dyes that rely on the inspectors
ability to visually identify surface indications.
Magnetic particle testing falls into a similar
category. Radiographic techniques require that
the technician use visual judgment to determine
the soundness of the object being tested. Visual
testing often locates areas where other NDT
techniques need to be applied, or areas where
mechanical and optical aids may provide improved
inspection.
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BASIC REQUIREMENT
Much of the success of VT depends on the surface
condition and the lighting arrangements. Surface
preparation such as cleaning and etching is often
used. VT requires adequate illumination of the
test surface and proper eye-sight of the tester.
To be most effective VT does however, merit
special attention because it requires training
(knowledge of product and process, anticipated
service conditions, acceptance criteria, record
keeping, for example) and it has its own range of
equipment and instrumentation.

• In its paper on visual testing, the American
  Welding Society (AWS) said that requirements for
  visual testing typically pertain to three areas
• The inspector's vision
• The amount of light falling on the specimen,
  which is measured using a light meter and
• Whether the area being inspected is obstructed
  from view.

EXPERIENCE KNOWLEDGE
Experienced knowledge inspector knows where
when are likely the defects occur. Orientation of
defects relative to various stages of
manufacturing welding at various areas and zones
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ATTRIBUTES
Why rely on Visual Testing? It comes to mind why
on earth do people rely on visual testing, as
this certainly is far more complex than
originally understood? Well this test method has
many attributes offering a broad potential for
many applications. VT when controlled correctly
will perform as efficiently as any other method.
Images obtained are frequently non-intrusive
requiring minimal disruption to plant operation.
Remote applications allow safe working distances
to be maintained in hazardous environments
extending working hours due to reduces exposure
times
To summarize, VT can be as simple or complex as
the job demands whilst retaining cleanliness and
so minimizing contamination, yet allowing images
to be recorded by a range of media to offer
permanent records for inspection history.
While VT is limited to materials surface-only
examination, it often detects the most damaging
defects. It may be of great assistance as a
guide in other test, e.g. VT of weld bead may aid
in deciding upon the angle of incidence of an
x-ray beam when examining the weld for cracks not
visible at the surface. VT, by the American
Society for Non-destructive Testing (ASNT) of
welded components requires inspectors to have a
broad knowledge of many technologies, including
welding, destructive testing, non-destructive
testing, and metallurgy, as well as the correct
terminology for each.
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LIMITATION
Generally, its application is limited to the
surface defects only. However, it may be
performed by optical aids for examination of
difficult areas which are not visible directly by
the eyes or accessible directly by human senses.
Application of VT is not limited to the metals,
metallic parts jointing/welding only. It is
applicable to all the manufacturing process at
almost all stages. E.g. at a project site it
starts with earth work and ends with the surface
treatment/paintwork of not just concrete
structures but mechanical installations also.
It is usually more rapid than other NDI
techniques, and has considerable flexibility.
Although it is usually defined with reference to
the eyes and visible spectrum, in fact VT
includes most other non-machine-enhanced methods,
such as feel or even sound. It is perhaps best
characterized as using the inspectors' senses
with only simple job aids such as magnifying
loupes or mirrors. As such, VT forms a vital part
of many other NDI techniques where the inspector
must visually assess an image of the area
inspected, e.g. in PT, MT RT. An important
characteristic of VT is its flexibility, for
example in being able to inspect at different
intensities from walk-around to detailed
inspection. From a variety of industries,
including aviation, Oil Refineries we know that
when the reliability of visual inspection is
measured, it is less than perfect. Visual
inspectors, like other NDT inspectors, make
errors of both missing a defect and calling a
non-defect (misses and false alarms respectively).
,
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DEFECT
As per E-1316 Defect One or more flaws whose
aggregate size, shape, orientation, location,
or properties do not meet specified acceptance
criteria and are rejectable. Discontinuity ?A
lack of continuity or cohesion an intentional or
unintentional interruption in the physical
structure or configuration of a material or
component. Flaw? An imperfection or
discontinuity that may be detectable by
nondestructive testing and is not necessarily
rejectable. Imperfection ? A departure of a
quality characteristic from its intended
condition.
TYPES OF DEFECTS
Inherent Defects- Present during initial
production of raw material Processing Defects-
Resulted from the manufacturing process Service
Defects- Occurred during the operation
EXAMPLES OF CAUSES OF DEFECTS
Blowholes- Gas trapped during
solidification process Segregation- During
solidification of allow Scale-
Oxide formation on the surface of a metal heated
to high temperature Stress-
Residual stress after cold working or rapid
cooling
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SURFACE DEFECTS
WELDING Slag, Surface Cracks,
Distortion/Warpage, Incorrect Or Bad Bead
Profile, Dimensional Deviation/Incorrect Weld
Size, Overlaps Or Rolls, Undercuts,
Underfill/Suckback, Excess Penetration/ Excess
Reinforcement, Start-stop Points,
Interruptions, Unfilled Craters, Burn Through.
Surface Porosity, Surface Oxidation, Unevern
Coarse Ripples, Pock Marks/Flat Spots,
Excessive Spatters, Arc Stike
IN STEEL Weld Spatters, Weld Ripple/Profile,
Weld Slag, Undercut, Weld End Crater, Weld
Porosity, Rolled Edges, Edges-punch/Shear/Saw/Dril
l, Pits Craters, Thermally Cut Edges,
Shelling/Sliver/Hackles, Roll Overs/Cut
Laminations, Rolled-in Extraneous Matter,
Groves Gauges, Indentation Roll Marks
PAINTING Alligatoring(cross Hatch Pattern Of
Surface Cracking), Bubbles, Cracking ,
Cratering, Delamination/Peeling, Dry Spray,
Flatting/Water Spotting, Framing,
Hiding/Shadowing, Holidays, Lapping, Mud Craking,
Orange Peel, Overspray, Pinholes, Roller
Tracks, Runs/Sags, Sandy, Solvent Trap,
Streaking, Wrinkling
GALVANIZING Ungalvanised Weld Areas, Dark
Staining Adjacent To Welds, Dull Gray or Mottled
Coatings, Dross Pimples/Inclusions, White
Storage Staining, Ash Staining, Striations and
General Surface Irregularities, Runs, Drainage
Spikes Puddling
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STANDARDS
Currently there are only a few Internationally
recognized codes and standards that address VT.
They vary in degrees of content ranging from
brief guidelines for general scrutiny or to
extended considerations when addressing finite
analysis of many product forms.
One new standard, which has just completed the
formal vote stage prior to issue, is the General
Principles Document prEN13018 that addresses
requirements for the application of VT. This
document details many factors required to fulfill
a successful VT is one of the more
comprehensive general documents to date. Other
globally recognized documents specific to VT are
ASME boiler pressure vessel code sections V
,XI, EN 970 and AWS codes for welding,
Euronorms EN763, EN1370, EN12454 . ASME V for
many years has included VT as a recognized NDT
method requiring training certification of
personnel to the recommendations of SNT-TC-1A.
ASME XI relies upon VT as a main method of
pre-service in-service inspection mandating
training certification of personnel in
accordance with CP189.
Product standards also address the necessity for
VT of materials components endeavoring to
ensure quality control /or condition monitoring
of in-service components. Typical examples
include, pressure vessels boilers, power
generation equipment, chemical process plant,
structural engineering including steels and
concrete
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ASME REQUIREMENTS
ASME SECTION V GENERAL REQUIREMENTS
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ASME REQUIREMENTS
ASME SECTION V SPECIFIC REQUIREMENTS
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BS REQUIREMENTS
BS EN 13018 2001 REQUIREMENTS
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BS REQUIREMENTS
BS EN 13018 2001 REQUIREMENTS
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OPTICAL SYSTEMS / TOOLS
SOME ARE PRESENTED BELOW
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WELDING DEFECTS
SOME ARE PRESENTED BELOW
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FABRICATION/INSTALLATION TOLERANCES
SOME ARE PRESENTED BELOW
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FABRICATION/INSTALLATION TOLERANCES
PIPING
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(No Transcript)
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• AFTERWORDS
• With no previous working on this , reading
  various article on internet, browsing through
  hundreds of relevant web sites and available hard
  copies of books notes, this presentation is
  developed or better to say as compiled in total
• 8 (eight) days time (on part time basis).
• I am thankful for the people web sites for
  making various data posted at their sites.
• The sole purpose of this document is to make not
  just an informal but also a more useful
  comprehensive guide for Visual Test., which was
  yet to be available on internet (with free
  access) before this (in my opinion).
• All comments will be appreciated welcome.
• Please do not hesitate to contact
  zaheerahmedsajid_at_yahoo.com
• Thanks.