The IIWEI is the focal point for welding and NDT
in Ireland.
BACKGROUND
The Institute was set up in 1996 by interested groups from
Engineering Industry, Service Inspection companies, Aerospace
Industry, Insurance
Industry, Institute of Technology, Training Institutions and
Semi-state Organisations. The IIWEI
acquired legal status in 1998.
AIMS AND OBJECTIVES
The object of the Institute is to promote and advance the science
and practice of welding and Non-Destructive Testing, condition
monitoring, diagnostic engineering and all other materials
and quality testing disciplines.
The Institute serves the needs of the welding and Inspection/NDT
community through its wide range of activities, and by acting
as a professional body for technologists engaged in welding
and inspection
activities.
The IIWEI is a recognised certifying body for approval of
personnel in welding technology, inspection and Non-Destructive
Testing.
What is welding?
Welding Introduction and
Utilisation.
Many of the textbooks that exist today describe
the events leading to the invention of welding using a stick
electrode as far back
as the 1890s. It was almost half a century later when the technique
of stovepipe welding for pipelines was developed in the USA.
The
technique is still used to the present day, with only minor
variations. Structural welding on a large scale began with the
construction of Liberty ships and T2 tankers in the Kaiser shipyards
during World War 11. Whilst the method of manufacture could be
said to be revolutionary for that period, it was regarded as
a
major success. There were of course some catastrophic failures,
with ships breaking in two as a result of brittle fracture. But
such problems were soon overcome, and more importantly, fusion
welding became the method of joining material, in the fabrication
of ships, pressure vessels, boilers, bridges and structural steelwork.
It is described as a welding method that is capable
of providing a high strength joint in metallic components. It does
this by melting the metal to form a bridge between the parts to
be joined.
From a metallurgical view point, the definition of weldability
is elastic, in that it can range from the ability to tack two pieces
of metal together without having them come apart, to meeting the
sophisticated needs of modern specifications. For example, from
very basic constructions, to high temperature components and pressure
vessels for nuclear, petrochemical and other applications.
The most common forms of welding are carried out
by manual techniques by a person referred to as a ‘welder’.
An electric arc or gas flame is used to melt the metal in the
joint. The welder
is in full control of the process and the quality of the finished
weld is depended on how well the operational technique has been
applied. The welding processes widely used are Manual Metal Arc
(MMA), Tungsten Inert Gas (TIG), Metal Inert Gas (MIG) and Oxy-acetylene
(OA).
With the exception of (OA), the heat source is supplied by a welding
transformer/rectifier, which can be a multi-operational unit capable
of producing alternating current (AC) or direct current (DC). Each
process has its own field of application and the welding plant
is often purpose built to meet specific requirements.
The demands of an ever-changing industry have brought
about welding mechanised systems for high volume production and
specialised applications.
In everyday life we use a whole range of equipment fabricated from
sheet metal. Items such as cars, refrigerators and washing machines
which are mass-produced to satisfy basic requirements. Welding
robots play a major role in this repetitive type of production.
The term ‘welding’ covers a large number of welding
techniques for all known materials and thickness, which the design
and production engineers carefully consider before selecting the
best method of joining. Each method has its own attributes, and
a number of aspects must be evaluated in order to achieve desired
results. Consideration of factors such as strength, ease of manufacture,
cost, permanency, corrosion-resistance, and appearance depends
very much on the specific application.
Welding Standards and Construction
Joints
Welding standards have been around for a very long time and were
drawn up by national and international professional institutions.
The objective was to enable fabricators to produce components to
the quality, which was depicted by the standard. The designer of
a welded structure bases his calculations on the properties of
the parent metal that he has chosen. The assumption is made, therefore,
that the weld will have properties at least equal to those of the
parent metal. Where this is not so, there must be a clear understanding
of the effects of welding on the strength of the joint.
There are four basic types of joints used in fabrication: butt,
fillet, corner and lap. The butt used when joining lengths of pipe
and plates. The fillet is probably the most common joint and can
be a partial or full penetration; plates set up as a ‘T’.
The corner joint can be butt or fillet – welded to service
requirements. Finally, the lap joint can be used in butt, ‘T’ and
corner joints.
Checking and Controlling Weld Quality
It is mainly subject to the welding application and laid down
standards, as to whether defects in the completed welds are permissible.
In most situations welding of test pieces will be carried out on
the chosen material, simulating the joint configuration, process,
position, parameters, consumables and type of gas been used in
production. This information is given to the welder in the form
of a weld test procedure. The tests are conducted and witnessed
usually by and independent third party inspector. An approved test
house will subject the welds to the requirements of the chosen
standard. The test house issues reports. If the weld passed all
of the tests required, then a certificate is issued to that effect.
This information proves the design and method capabilities, but
more importantly it demonstrates a level of welding quality. In
the production cycle the welding Inspector can carry out visual
examination, gauge checks on fillet weld leg length and throat
thickness, as well as other forms of non-destructive tests (NDT)
as may be required.
Company Certification IS09001/2
Member countries of the EEC have formed a committee through their
accredited welding Institutions, which has brought about EN Welding
Quality Standards, that has become the norm for manufacturers irrespective
of state. Companies who have not yet aspired to, or achieved ISO9001/2
would be well advised to conform without delay. Many companies
have achieved ISO9001 or 9002 with respect to their quality management.
But where significant use is made of a special process like welding,
such certification is unlikely to provide the required demonstration
of the capability of the company to manufacture products of the
required quality. EN729 (which is also published as ISO3834) can
overcome these, entitled, Quality Requirements for Welding.
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What is Non-Destructive Testing?
Background:
Non-Destructive Testing (NDT) is normally performed to verify the
quality of materials being tested and their compliance with requirements
of codes, standards, regulatory bodies, clients or others. It
is also performed to satisfy the rules of safety governing the
fabrication and testing of such materials.
Factors affecting NDT performance.
In general, three elements are involved in non-destructive testing.
These elements are the procedures, equipment and personnel involved
in performing the test.
Procedures are normally required to be in accordance with the requirements
of the applicable codes, standards or specifications and are considered
controllable. However, approved procedures does not necessarily
mean proper compliance in its implementation.
Equipment is normally controllable and its performance is verifiable.
As with procedures, however, appropriate equipment does not necessarily
indicate proper utilization and performance.
The operator, is the deciding factor that determines whether the
non-destructive test is successful and serves the intent and purpose
of performing it.
What is NDT:
Non-destructive testing is the branch of engineering
concerned with all methods of detecting and evaluating flaws
in materials.
Flaws can affect the serviceability of the material or structure,
so NDT is important in guaranteeing safe operation as well
as in quality control and assessing plant life. The flaws may be
cracks
or inclusions in welds and castings, or variations in structural
properties which can lead to loss of strength or failure in service.
Non-destructive testing is used for in-service inspection and
for condition monitoring of operating plant. It is also used for
measurement of components and spacings and for the measurement
of physical properties such as hardness and internal stress.
The subject of NDT has no clearly defined boundaries; it ranges
from simple techniques such as visual examination of surfaces,
through the well-established methods of radiography, ultrasonic
testing, magnetic particle crack detection, to new and very specialised
methods such as the measurement of Barkhausen
noise and positron annihilation.
NDT methods can be adapted to automated production processes as
well as to the inspection of localised problem areas.
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