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Course: Quality Assurance
This project has been funded with support from the European Commission. This publication reflects the views only of
the authors, and the Commission cannot be held responsible for any use, which may be made of the information
contained therein.
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List of content
MODULE 1.......................................................................................................................................... 4
Activity Based Training .................................................................................................................. 4
Normative references ...................................................................................................................... 7
MODULE 2.......................................................................................................................................... 9
Summary comparison of ISO 3834, Parts 2, 3 and 4 .................................................................... 14
The European Welded Product Standards ..................................................................................... 15
MODULE 3........................................................................................................................................ 16
The work ....................................................................................................................................... 16
Hours and Environment ................................................................................................................ 17
Skills and Interests ........................................................................................................................ 17
Accredited and none-accredited certification ................................................................................ 19
Maintenance and prolongation of certificates ............................................................................... 19
Essential variables for the certificates ........................................................................................... 19
MODULE 4........................................................................................................................................ 21
Routes to welding procedure approval ..................................................................................... 21
Welding operator approval ....................................................................................................... 23
Welding symbols according ISO 22553 ........................................................................................ 28
Types of butt welds ....................................................................................................................... 29
Types of fillet welds ...................................................................................................................... 30
Supplementary symbols ................................................................................................................ 30
MODULE 5........................................................................................................................................ 33
Surface inspection on cracks and other surface imperfections by visual testing ......................... 34
MODULE 6........................................................................................................................................ 38
Preheating, interpass and post heating to prevent hydrogen cracking .......................................... 50
Preheat ...................................................................................................................................... 50
Interpass and post heating......................................................................................................... 51
MODULE 7........................................................................................................................................ 52
Visual Inspection (VT) ............................................................................................................ 52
Defects/imperfections in welds - porosity ......................................................................................... 54
Identification ................................................................................................................................. 54
Cause and prevention .................................................................................................................... 54
Distributed porosity and surface pores ..................................................................................... 54
Fig. 1. Uniformly distributed porosity ................................................................................. 54
Fig. 2. Surface breaking pores (T fillet weld in primed plate) ............................................. 55
Prevention ................................................................................................................................. 55
Wormholes .................................................................................................................................... 56
Elongated pores or wormholes ............................................................................................ 56
Prevention ................................................................................................................................. 56
Crater pipe ..................................................................................................................................... 56
Prevention ................................................................................................................................. 56
Porosity susceptibility of materials ............................................................................................... 57
Principal gases causing porosity and recommended cleaning methods .............................. 57
MODULE 8........................................................................................................................................ 58
Delivery of the product. ................................................................................................................ 58
Identification and traceability........................................................................................................ 59
This project has been funded with support from the European Commission. This publication reflects the views only of
the authors, and the Commission cannot be held responsible for any use, which may be made of the information
contained therein.
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Quality records .............................................................................................................................. 59
This project has been funded with support from the European Commission. This publication reflects the views only of
the authors, and the Commission cannot be held responsible for any use, which may be made of the information
contained therein.
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MODULE 1
Objective:
Have an overview of the course structure and the course methodology for the education and training.
Scope:



Role and responsibilities of the welding personnel
Know the most relevant standards for Quality Assurance
Understand the fundamental ideas behind Activity Based Training (ABT)
Expected results:


Perform the Quality Assurance tasks related to the job
Understand the relevance of Quality Assurance and Quality Control
Activity Based Training
Instead of utilizing the traditional methodology whereby the student moves through a traditional education
with theoretical content from A to Z, followed by hands on training, this course will use an Activity Based
Training (ATB). With ATB it is understood that the training follow the production activities according the
production path of a predefined structure or product. The course will also exploit a blended approach
whereby different delivery technologies for the content itself will be used.
The course has been divided into 9 different modules and three of these are modules where the major part of
the hours will be utilized for practical work. This means that the students have to participate together in a
workshop or laboratory.
This is an important aspect of the methodology itself. When working in an industrial environment the student
has to work together with other personnel in order to meet the requirements in quality, time schedules and so
forth. The team building effort, its importance for the final product and its importance for the total quality of
the production environment must be stressed during the educational process.
In a welding environment today the students will work together with other persons from different cultures,
with different educational backgrounds and with different practical experience, which will require a
profound focus on flexibility and open minded attitude towards other people. Few if any other educational
routes will demand such flexibility to the student itself and to the students behaviour on a short and long term
basis.
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the authors, and the Commission cannot be held responsible for any use, which may be made of the information
contained therein.
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The course will consist of several job-elements. The figure shows how one work-package is built up of
different elements, some are pure theory elements and other is a mixture of theory and hands-on training.
The training will be carried out in the workshop, shop, or in a laboratory. Video streaming and/or
videoconferencing will be used in Shop/Theory packages.
Work Package.
A work package might contain several job elements. A work package is a complete documentation package
of specific activities that must be mastered in the welding industry in order to handle the whole production
process. It contains at least the following information:
i.
ii.
iii.
iv.
v.
vi.
vii.
viii.
ix.
x.
Drawing of the structure to be fabricated
Work description with which methods shall be used in the production
Work description with process description of the work process for reaching the target and the
knowledge required
Quality assurance requirements for the ingoing elements
Quality assurance description of the outgoing elements
Work package description for the work to be done
Reference to available resources for the work
Reference to environmental resources or requirements or restrictions
Requirements for knowledge, prerequisite or knowledge that has to be obtained
Cooperation strategy with other in a defined group or to related groups
However, some basic prerequisite knowledge must be mastered by the production staff in order to follow the
knowledge requirements. The knowledge and competence requirements include:
Ability to work in a multicultural environment with the colleagues due to exchange of mobile personnel
across borders and among mechanical industry companies
Ability to understand and communicate the content in the job packages to the colleagues in a multilingual
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the authors, and the Commission cannot be held responsible for any use, which may be made of the information
contained therein.
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working environment
Ability to understand his/her responsibility in the production chain and to communicate the need for
knowledge.
Ability to search for relevant learning and training material when needed.
To understand how a process plan might be visualized by utilizing a project plan.
A general design of a learning element. This element consists of both theoretical content as well as practical
work. We can also see that the practical task, when completed shall be verified by the student as well as by a
3-part. This will both ensure that the student feel responsible for the part itself, but also be aware of the
quality assurance aspect which is very important withing the welding activities. This is a simplified design
where no loops are included in the process flow.
A central philosophy within fabrication is that the person who produce a product shall not be the one
carrying out the quality control of the same product. To establish the same methodology in education one
aims at introducing an alternative production flow whereby the product alternate between students or student
groups.
This project has been funded with support from the European Commission. This publication reflects the views only of
the authors, and the Commission cannot be held responsible for any use, which may be made of the information
contained therein.
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A product is alternating between students during the fabrication process. When produced by student A at a
certain stage then student B will carry out the quality control of the part. Student B will then use the part
from A in his own production and then transfer it back to A for the following quality control.
This means that the students shall be familiar with and use the definitions and actions that are common in the
industry. It will consequently be mandatory to switch the objects for this purpose in order to avoid that a
person verifies himself. If defects or non-conformance is found then the necessary corrective actions have to
be carried out by the student.
The use of objects should reflect the typical industry environment that is domination in the area where the
course is held in order to create a more relevant training domain. But when this is done, then he other
examples and references in the material should be selected from a similar industrial background in order to
make tis relevant fro the student .
Delivery.
The structure described here is a structure that can be used in different environments. The structure has not
been designed for a special delivery method. However, when that has been said, it is possible to use a highly
structured an d rigid structure whereby you may control an verify all steps of the student,
If that is the correct way of carrying out the course is of course another question.
The structure that follows is a an idea of which elements that a course should contain, if its running as a web
course or if its running as a face-to face course without having access to the web itself.
Normative references
In the following table is a list of some of the European (EN) standards within the welding sector. This list is
not complete.
Bold documents are of special importance
Year
DokNo
Name
EN ISO 3834
Welding coordination - Tasks and responsibilities
2005
EN ISO 3834-1
Quality requirements for welding - Fusing welding of metallic
materials - Part 1: Guidelines for selection and use
2005
EN ISO 3834-2
Quality requirements for welding - Fusing welding of metallic
materials - Part 2: Comprehensive quality requirements
2005
EN ISO 3834-3
Quality requirements for welding - Fusion welding of metallic
materials - Part 3: Standard quality requirements
2005
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the authors, and the Commission cannot be held responsible for any use, which may be made of the information
contained therein.
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EN ISO 3834-4
Quality requirements for welding - Fusion welding of metallic
materials - Part 4: Elementary quality requirements
2005
EN 1011-1
Welding - Recommendations for welding of metallic materials Part 1: General guidance for arc welding
1998
EN ISO 4063
Welding and allied processes - Nomenclature of processes and
reference numbers (ISO 4063:1998)
2000
Page
Title
Comment
Table with reference literature to be read in addition to the course documentation for the individual modules.
This table to be compiled according to the national availability of reference literature.
This project has been funded with support from the European Commission. This publication reflects the views only of
the authors, and the Commission cannot be held responsible for any use, which may be made of the information
contained therein.
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MODULE 2
Objective:
Have knowledge about the function of Quality Assurance (QA) in welding.
Scope:




Role of inspection and Quality control
Key role of welders in assuring weld Quality
Introduction of ISO 3834: Quality Requirements for Welding
Introduction of ISO 14731: Welding Co-ordination and relationship to IIW qualifications
Expected results:


Explain the need for quality assurance in welding.
Identify the position of ISO 3834 in connection with the standards for welding personnel and welding
procedures.
Quality
The word quality comes from Latin and means state or nature. Quality is a word that describes the
characteristics of a product or service. The meaning of the word quality differs depending on who you ask
and which product or service that is being referred to. The right quality is when the demands put on a product
or service is fulfilled. Substandard quality is only when the demands put on a product or service are not
fulfilled. Above standard quality is when a product or service fulfils more than what is demanded.
As an example....... The demands put on a car used for short trips between your home and your place of work
is, for most people, that is reliable and cheap to run. A Rolls Royce fulfils the demand on reliability by a long
way and is also very comfortable. In this particular case, the quality of a Rolls Royce is above standard.
However, it does not fulfil the requirement of being cheap in mileage costs as the initial purchase price, fuel
consumption and insurance together will give a high mileage cost. On the other hand a car that is 15 - 20
years old and has gone more than 200.000 km can be very charming but could not be called reliable and will
therefore represent substandard quality. A car buyer's choice, that is to say the one with the right quality in
this case, would probably be a small car, perhaps just a few years old but reliable and inexpensive in fuel
consumption.
A standardized definition of quality is: " All the combined characteristics and properties of a given
product that gives it the ability to satisfy expressed or implied needs"
Another definition could be: "The quality has two dimensions: "must-be quality" "Conformance to
specifications" or "fitness for use" (defined by the customer) or and "attractive quality". The latter is what the
customer would love, but has not yet thought about. "
Quality policy
A quality policy describes the company's aims and intentions with regard to quality. The executive
management of a company establishes and signs the company's quality policy. This is a requirement
specified in the ISO 9000 quality system. A company's quality policy is often briefly described using one or
more phrases. For example:

We will abide by principles resulting from valid legislation and develop the applied system of quality
control at all activities, which are connected with the implementation of company products.
This project has been funded with support from the European Commission. This publication reflects the views only of
the authors, and the Commission cannot be held responsible for any use, which may be made of the information
contained therein.
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We will use up-to-date experience and methods, which ensure quality and reliability increase of supplied
products to ensure permanent improvement of the system of quality control. Further we will use feedback
as regards information of the quality of operated products and plants, acquired from customers and
employees of ZVVZ a.s.
A company's quality policy is the foundation and guideline of its quality operations.
Definitions
Quality control
A system for verifying and maintaining a desired level of quality in a product or process by careful planning,
use of proper equipment, continued inspection, and corrective action as required.
The operations of a company are controlled to give products the right level of quality. This means that the
daily activities follow the company's quality system, applying the directions contained in the quality manual
and the instructions that are to be available at each workplace.
Quality assurance
A standard definition is that quality assurance is " all planned and systematic activities to give sufficient
confidence that a product will fulfil given demands on quality"
Quality Assurance covers all activities from design, development, production, installation, servicing and
documentation, this introduced the rules: "fit for purpose" and "do it right the first time". It includes the
regulation of the quality of raw materials, assemblies, products and components; services related to
production; and management, production, and inspection processes.
Quality system.
A company's quality system gives guidelines to how the business should be organized, managed and
controlled as well as how responsibility is to be distributed. The objective of a company's business is to
provide products or services with the right level of quality. A quality system describes the procedures,
methods and processes that are to be applied.
Quality manual
All the documents describing the quality system in a company must be entered into a quality manual. The
contents and appearance of the quality manual usually varies from company to company. The quality manual
describes everything from the company's quality policy to the procedures and processes used to attain the
quality objectives.
Certification
Company.
In order to prove they have a working quality system, a company can apply to be certified. A certification
involves an inspection to ensure that the requirements applying to the quality concerned are fulfilled. Such an
inspection is called quality audit.
Certifications may be perpetual, may need to be renewed periodically, or may be valid for a specific period
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the authors, and the Commission cannot be held responsible for any use, which may be made of the information
contained therein.
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of time (e.g. the life-time of the product upon which the individual is certified).
Certifications are offered through a certification body. This is usually a business organization. Sometimes,
the organization's business is directly related to the certification, In other cases, an organization (often a notfor-profit organization) exists wholly, or in large part, to offer a particular certification. Whatever its nature,
the certifying body determines the policies of the certification program. Potential consumers of a
certification wish to understand the nature of the certifying body and the certification process.
Personnel
The ability to follow verbal or written instructions and testing of the skill are important factors in ensuring
the quality of a welded product. Testing of the skill will be done according the relevant standard or guideline.
Such a test will then lead to a certificate or a diploma.
Although it is common in regards to certificates and diplomas, sometimes as part or whole of the renewal of
an individual's certification, the individual must show evidence of continual learning — often termed
continuing education or life-long-learning.
Accredited certification
Certification carried out according an accredited certification body. An accredited certification body has
received an accreditation from the National accreditation body.
Inspection.
To ensure that a product has the right level of quality, some form of inspection is often required. This can
involve such things as measuring the dimensions of a welded part, destructive or none-destructive testing and
so forth.
A standard definition of Inspection is: " Measurement, investigation, testing or other classification of one or
more characteristics or properties of a product and the comparison of the results with the set requirements to
determine whether they are fulfilled."
Welding coordination
ISO 14731 " Welding Coordination - Tasks and Responsibilities" is the standard that covers supervision of
welding processes and thereby the role and competence of the welding coordinator.
Welding is a special process which requires the coordination of welding operation in order to establish
confidence in welding fabrication and reliable performance in service. The tasks and responsibilities of
personnel involved in welding and related activities, e.g. planning, executing, supervising and inspection,
should be clearly defined.
For all tasks assigned, a welding coordination personnel shall be able to demonstrate adequate technical
knowledge to enable such tasks to be performed satisfactorily. The following factors should be considered:
-
general technical knowledge
special technical knowledge relevant to the assigned tasks. This may be attained by a
combination of theoretical knowledge, training and/or experience.
The extent of required manufacturing experience, education and technical knowledge should be decided by
the manufacturing organization and will depend on the assigned tasks and responsibilities.
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the authors, and the Commission cannot be held responsible for any use, which may be made of the information
contained therein.
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Authorized welding coordination personnel should normally be allocated from one of the following groups.
This will depend on the nature and/or complexity of the production. Adequate manufacturing experience
need not necessarily be longer than three years.
ISO 3834
For welded constructions to be effective and free from serious problems in production and in service, it is
necessary to provide controls, from the design phase, through material selection, into fabrication and
subsequent inspection.
For example, poor design for welding may create serious and costly difficulties in the workshop, on site, or
in service. Incorrect material selection may result in welding problems, such as cracking. Welding
procedures have to be correctly formulated and approved to avoid imperfections. Supervision needs to be
implemented to ensure that the specified quality will be achieved.
For the manufacturing industries a set standards, ISO 3834, with appropriate guidelines have been
developed. These guidelines are intended to be used for the following purposes:
a)
standards, as a
system related to
providing interpretation of the requirements in the EN ISO 9000 series of
guideline for specification and establishment of the part of the quality
control of welding as a "Special Process".
b)
providing guidelines to establish specifications and welding quality requirements
quality system according to EN ISO 9001 and EN ISO 9003 is not involved
c)
assessment of the welding quality requirements mentioned in a) and b) above.
where a
The applicable party of ISO 3834 (2, 3 or 4) for stand alone assessment and certification of welded
operations and activities will depend on the nature of the welding activities required to meet the agreed
specifications and influenced by how critical the welding operations are to the quality and fitness of the final
product.
Common to all three levels of ISO 3834;

All welders must take a welding test in compliance with EN 287 or EN ISO 9606 series of standards.

All welding operators must take a welding test in compliance with EN 1418.

Welding Inspectors for NDT must be qualified in compliance with EN 473

Demands on description (not ISO 3834-4) and maintenance of equipment such as welding power sources
and heating chambers

A WPS ( Welding Procedure Specification) or a WI (Welding Instruction) is used to control the welding
process( Not ISO 3834-4)

Filler material must be handled in accordance to the manufacturer's instruction.
As can be seen above, even quality control of welding process in compliance with the simplest and least
comprehensive standard, ISO 3834-4, demands the application of the most important parts of the new
European standards.
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the authors, and the Commission cannot be held responsible for any use, which may be made of the information
contained therein.
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Summary comparison of ISO 3834, Parts 2, 3 and 4
Note: Being certified gives a company a competitive edge. The fact that a company is certified is often used
when marketing different products or it may be a prerequisite in order to deliver products. Some customers
believe that a certificate is a guarantee of good quality. This is a misconception. A certificate does not say
anything about the quality of the product or services, only that the company possesses a quality system that
fulfils the requirements of the standard. Nevertheless, a working quality system does help to attain the
desired product quality.
This project has been funded with support from the European Commission. This publication reflects the views only of
the authors, and the Commission cannot be held responsible for any use, which may be made of the information
contained therein.
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The European Welded Product Standards
It is up to the Manufacturer to decide which way to go through to fulfil the Directives’ essential
requirements, giving evidence of such a fulfilment. The simplest way, often from contractual point of view,
is that of the European standards, either harmonised or not.
The European harmonised standards, provide a direct presumption of conformity to the corresponding
Directives’ essential requirements.
The European non harmonised standards, are however an agreed tool that can assure transparency and
common understanding; consequently they are becoming a more and more applied reference in
manufacturing contracts.
The most important applicable European standards, dealing with welding fabrication, are shown in the table:
Directive
87/404/EEC
(SPVD)
97/23/EC
(PED)
99/36/EC
(TPED)
89/106/EEC
(CPD)
01/16/EC
(CRSD)
96/48/EC
(HSRD)
Product
Standard
EN 286
EN 13445
EN 13480
EN 12952
EN 12953
EN 13530
Standard Title
Simple unfired pressure vessels designed to contain air or nitrogen
Unfired Pressure Vessels
Metallic Industrial Piping
Water-Tube Boilers and Auxiliary Installations
Shell Boilers
Cryogenic Vessels – Large transportable vacuum insulated vessels
Tanks for transport of dangerous goods
EN 14025
pr EN 1090
Execution of steel and aluminium structures
pr EN 15085
Welding of railway vehicles and components
All these standards, when facing the welding fabrication process control, mention directly or indirectly the
EN ISO 3834.
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the authors, and the Commission cannot be held responsible for any use, which may be made of the information
contained therein.
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MODULE 3
Objective:
Know the basics of welder qualification according to ISO 9606.
Scope:



The scope of work for welders (Definition of the responsibilities)
Objectives of qualification tests
Welders qualification standard (ISO 9606)
Expected results:


Identify the range of qualification in a welder's certificate.
Outline the essential variables for a welder qualification test.
Key roles of welders in assuring weld Quality. Authority and responsibility.
The roles, authority and responsibilities is depending on the job specification and the company. However the
following job description form UK may be used as a general overview of what a welder may face.
The work
Welders, often known as welder fabricators, cut, shape and join materials to make products and components
in a wide variety of industries including construction, shipbuilding, engineering, transport, power,
automotive, aerospace, and offshore oil and gas. They also work in these industries carrying out repair and
maintenance of equipment and machinery.
Although welders primarily work with metals and alloys, they can also cut and join composite materials.
Welders use a range of welding and cutting techniques in their role. Some common methods include:
oxyacetylene – technique using a mixture of oxygen and acetylene
MIG (metal inert gas) / MMA (manual metal arc) – also known as arc welding, is basic hand
welding/cutting using electric arc equipment and a welding rod
 TIG (tungsten inert gas) – welding with nitrogen or carbon dioxide, in a tightly controlled manner,
using the inert gas to shield the welding process and protect the strength of the metals being joined
 laser welding – using laser tools to produce very precise cuts/joins
 ultrasonic welding – using high frequency sound waves to melt composites or thermoplastic
components, often found in automated assembly processes.


Typical tasks include:

selecting, laying out and positioning materials to be cut or joined, paying close attention to
engineering drawings, templates and specifications
 using the appropriate methods outlined above to produce sections or make repairs
 inspecting and testing cuts, joins and tolerances using callipers, micrometers and other precision
measuring instruments
 operating mechanised welding equipment, usually on high volume production lines.
Welders would not be expected to be proficient in every type of weld, as different methods suit different
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the authors, and the Commission cannot be held responsible for any use, which may be made of the information
contained therein.
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industries and companies.
Hours and Environment
Welders normally work 37 to 40 hours a week. Shiftwork is common and overtime may be necessary to meet
deadlines.
Many welders work in factory workshops, however, some working conditions may be cramped, for example,
in the bottom of a ship’s hull. Outdoor work may be required if welding sections of pipeline or processing
plant.
Protective clothing including head-shield, overalls, apron and gloves are worn. In some situations they
might need to use specialist safety equipment, for example breathing apparatus for underwater work, or
safety harnesses if working at heights.
Skills and Interests
To be a welder you should:








have good hand-to-eye coordination
be able to work very accurately and have good concentration levels
have the ability to work without direct supervision
have excellent technical knowledge and awareness of material properties under different conditions
be able to understand technical plans and specifications
have good near vision
have good numeracy skills to calculate tolerances and measurements
be aware of safe working practices.
However if we combine the above general description with what has been said about quality assurance, then
some basic responsibilities and authorities emerge:
The welder shall be able to:

Review the work order and verify if this is correct

Verify if the welding drawings are correct and complete with reference to weld details

Identify possible cooperation and dependencies with other personnel or departments

Verify and understand if I have the correct competence for the work, and if not, apply for required
training and skills upgrade

Verify if the welding equipment is maintained correctly and that it can be operated in a safe manner

Identify if the work order contains correct WPS and time schedules

Identify if the work requires special documentation or identifications or traceability

Identify requirements for heat treatment and relevant heat treatment methods and control equipment

Identify requirements for inspection and the consequences for the work

Know how to identify non-conformance and how to carry out corrective actions

Be able to work in a team with people with different backgrounds, knowledge and cultural heritage
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the authors, and the Commission cannot be held responsible for any use, which may be made of the information
contained therein.
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Documentation of knowledge
A welder may document his/her qualifications through certificates or diplomas.
EWF Diplomas
European Federation for Welding, Joining and Cutting, better known as EWF - European Welding
Federation, established as an international non-profit association. The objective is to:
Act as the representative of the welding and joining community in Europe





Prepare harmonised rules for the education and training of personnel involved in welding, joining
and related technologies
Liaise with Standardisation Bodies
Provide for the exchange of scientific and technical information
Encourage projects for co-operative research and contribute to the removal of technical barriers
Facilitate technology transfer through "Eurojoin" Conferences
ANB
EWF designates an ANB (Authorised National Body) in each country that has the main responsibility for the
welder training in that country (and also other welding personnel). The training is conducted by training
bodies that are independent from the ANB itself. before a training organiser can start the EWF training
course, the ANB must ensure that the curriculum, instructors, study material, premises and equipment fulfil
EWF requirements. Recurrent audits are also carried out. The ANB is also responsible for the examinations
that are conducted during and after each course.
The ISO 9606- series of International Standards provides a scheme for qualification testing of welders, to
evaluate their skill for limited ranges of welding conditions. It serves for quality assurance for a specific job,
but does not provide an education and training programme. However, the industry needs welders with more
skill for the sake of flexibility in production and this Guideline (IAB-089-2003/EWF-452-467-480-481/SV01) provides a combination of comprehensive theoretical knowledge and high practical skills, assessed by
tests of increasing difficulty, including ISO 9606 qualification tests and by theoretical examinations.
The IIW Harmonized Guideline takes care of both requirements and gives methods for practical training and
theoretical education of fillet, plate and pipe welders. Where in this Guideline reference to ISO 9606 is
made, EN 287 or any other equivalent regional standard may be used instead, upon decision of the ANB.
Certification according international standards
The testing of a welder's skill in accordance with EN 287-1 and the ISO 9606 series of standards depends on
welding techniques and conditions used in which uniform rules are complied with, and standard test pieces
are used.
The principle of EN 287-1 standard is that a qualification test qualifies the welder not only for the conditions
used in the test, but also for all joints which are considered to weld easier on the presumption that the welder
has received a particular training and/or has industrial practice within the range of qualification.
The qualification test can be used to qualify a welding procedure and a welder provided that all the relevant
requirements, e.g. test piece dimensions, are satisfied.
Accredited and none-accredited certification
Within the European system, there are a number of standards (EN 45000 series) that include regulations for
testing the ability of inspection organs to act as third party Body. Its aim is to ensure that the inspection
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organs acting in Europe carry out equivalent assessments so that the results can be approved by all the
member countries. The inspection organs that are approved according to these requirements become
accredited for a certain certification task.
A Manufacturer may be certified by a Accredited or a non-accredited Certification Body (national or
international). Both accreditations are valid but the certification realized by an Accredited Certification Body
has a much larger recognition.
Maintenance and prolongation of certificates
The welder's qualification test certificate issued is valid for a period of two years. This is providing that the
welding coordinator or the responsible personnel of the employer can confirm that the welder has been
working within the initial range of qualification. This shall be confirmed every six months.
Welder's qualification test certificates according to EN 287-1 (and 9606) standard can be prolonged every
two years by an examiner/examining body.
Before prolongation of the certification takes place, 9.2 needs to be satisfied and also the following
conditions need to be confirmed:
a) All records and evidence used to support prolongation are traceable to the welder and identifies the WPS
that have been used in production;
b) Evidence used to support prolongation shall be of a volumetric nature (radiographic testing or ultrasonic
testing) or for destructive testing (fracture or bends) made on two welds during the previous six months.
Evidence relating to prolongation needs to be retained for a minimum of two years;
c) The welds satisfy the acceptance levels for imperfections as specified in clause 7;
d) The test results shall demonstrate that the welder has reproduced the original test conditions, except for
thickness and outside pipe diameter.
Essential variables for the certificates
The qualification of welders is based on essential variables. For each essential variable a range of
qualification is defined. All test pieces shall be welded using the essential variables independently.
If the welder has to weld outside the range of qualification a new qualification test is required.
The essential variables are:
- welding process,
- product type (plate and pipe),
- type of weld (butt and fillet),
- material group,
- welding consumable,
- dimension (material thickness and outside pipe diameter),
- welding position,
- weld detail (backing, single side welding, both side welding, single layer, multi layer, leftward welding,
rightward welding).
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the authors, and the Commission cannot be held responsible for any use, which may be made of the information
contained therein.
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MODULE 4
Objective:
Know how to work to a WPS, knowing the use of welding parameters.
Have basic knowledge about the harmonised system of International Standards.
Scope:









Welding Procedure Specifications (ISO 15609-1).
Welding parameters, welding positions (ISO 6947).
Types of welds and joints: characteristics, size, surface finish.
Welding symbols according to ISO 2553.
Qualification of WPSs
Essential variables; range of qualification; validity; test pieces and assessment of the welder.
Role and operation of CEN and ISO; relationship with National Standards Organisations
Product Standards which contain welding requirements
Standards for Quality and Co-ordination in welding
Expected results:







Read welding details on a drawing and interpret welding symbols (ISO 2553).
Identify the welding positions per ISO 6947.
Identify the types of welded joints: “T”, lap, corner, etc.
Identify in the fillet weld: size, shape, tack weld, and excess weld metal.
Identify the use of a WPS in the production.
Describe how to get the required parameters.
Name the most important International and national standards for welding.

For a given application, the main way of ensuring adequate weld quality is to specify the procedure and the
skill level of the welding operator. Here, the alternative routes for welding procedure approval are described
together with the requirements for welder or welding operator approval.
Routes to welding procedure approval
The key document is the Welding Procedure Specification (WPS) which details the welding variables to be
used to ensure a welded joint will achieve the specified levels of weld quality and mechanical properties.
The WPS is supported by a number of documents (eg, a record of how the weld was made, NDE, mechanical
test results) which together comprise a welding approval record termed the WPAR (ISO 15614) .
In the European standards, there are a number of 'essential variables' specified which, if changed, may affect
either weld quality or mechanical properties. Therefore, a change in any of the essentials will invalidate the
welding procedure and will require a new approval test to be carried out. The essential variables are detailed
in the relevant specification but include material type, welding process, thickness range and sometimes
welding position.
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the authors, and the Commission cannot be held responsible for any use, which may be made of the information
contained therein.
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Stages in welding and welder approval
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The route followed to produce a WPS in ISO15614
and the responsibilities of the manufacturer and the
Examiner/Examining Body are shown in the figure
The most common method of gaining approval is to
carry out an approval test as described in ISO 156141 (steels) and 15614-2 (aluminium and its alloys).
The manufacturer initially drafts a preliminary
welding procedure (pWPS) which is used by one of
the manufacturer's competent welders to prove that it
is capable of producing a welded joint to the
specified levels of weld quality and mechanical
properties. The welding procedure approval record
(WPAR) is a record of this weld. If the WPAR is
approved by the Examiner, it is used to finalise one
or more WPSs which is the basis for the Work
Instructions given to the welder.
It is noteworthy that the welder carrying out a
satisfactory welding procedure approval test is
approved for the appropriate range of approval given
in the relevant standard .
The following options for procedure approval are also possible:





Welding procedure test (ISO 15614)
Approved welding consumable (ISO 15610)
Previous welding experience (ISO 15611)
Standard welding procedure (ISO 15612)
Pre-production welding test (ISO5613)
The conventional procedure test (as specified in ISO 15614) does not always need to be carried out to gain
approval. But alternative methods have certain limits of application regarding, for example, welding
processes, materials and consumables as specified in the appropriate application standard or contract
agreement.
The welding procedure test method of approval is often a mandatory requirement of the Application
Standard. If not, the contracting parties can agree to use one of the alternative methods. For example, a
welding procedure specification can be approved in accordance with the requirements of ISO 15611
(previous experience) on condition that the manufacturer can prove, with appropriate documentation, that the
type of joint has previously been welded satisfactorily.
Welder approval
The welder approval test is carried out to demonstrate that the welder has the necessary skill to produce a
satisfactory weld under the conditions used in production as detailed in the approved WPS or Work
Instruction. As a general rule, the test piece approves the welder not only for the conditions used in the test
but also for all joints which are considered easier to weld.
As the welder's approval test is carried out on a test piece which is representative of the joint to be welded, it
is independent of the type of construction. The precise conditions, called 'essential variables', must be
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specified in the approval test, eg material type, welding process, joint type, dimensions and welding position.
The extent of approval is not necessarily restricted to the conditions used for the test but covers a group of
similar materials or a range of situations which are considered easier to weld.
It is important to note that a number of Amendments and Corrigenda have now been issued which affect the
range of approval (see list of Relevant Standards).
In EN 287/EN 9606, the certificate of approval testing is issued under the sole responsibility of the
Examiner/Examining Body. The welder approval certificate remains valid subject to the requirements of the
application standard. In EN 287/EN 9606, it can be extended at six monthly intervals by the employer for up
to two years provided the welder has been successfully welding similar joints. After two years, prolongation
of the welder's qualification will need approval of the Examiner who will require proof that his or her
performance has been of the required standard during the period of validity. As the Examiner will normally
examine the company's records on the welder's work and tests as proof that he has maintained his skill, it is
essential that work records are maintained by the company.
It should also be noted that EN 287/EN 9606 requires records of tests, ie half yearly documentation about Xray or ultrasonic inspections or test reports on fracture tests must be maintained with the welder's approval
certificate (tests on production welds will satisfy this requirement). Failure to comply will necessitate a
retest.
American standards have similar requirements although the extent of approval of the welding variables are
different to those of EN 287/EN 9606.
Welding operator approval
When required by the contract or application standard, the welding operators responsible for setting up
and/or adjustment of fully mechanised and automatic equipment must be approved but the personnel
operating the equipment do not need approval. In clarifying the term 'welding operator', personnel who are
using the equipment (loading and unloading robotic equipment or operating a resistance welding machine)
do not require approval.
As specified in EN 1418, approval of operators of equipment for fusion welding and resistance weld
equipment setters can be based on:



welding a procedure test
pre-production welding test or production test
production sample testing or a function test.
It should be noted that the methods must be supplemented by a functional test appropriate to the welding
unit. However, a test of knowledge relating to welding technology which is the equivalent of 'Job knowledge
for welders' in EN 287/EN 9606 is recommended but not mandatory.
Prolongation of the welding operator approval is generally in accordance with the requirements of EN
287/EN 9606. The welding operator's approval remains valid for two years providing the employer/welding
co-ordinator confirms that there has been a reasonable continuity of welding work (period of interruption no
longer than six months) and there is no reason to question the welding operator's knowledge.
The validity of approval may be prolonged for further periods of two years by the examiner / examining
body providing there is proof of production welds of the required quality, and appropriate test records
maintained with the operator's certificate.
Welding procedures and instructions.
The Manufacturer shall prepare the Welding Procedure Specification(s) (WPS) and shall ensure that these
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are used correctly in production.
The welding procedures applied during production shall be as specific as possible, in order to clearly identify
actions and parameters to be used for the required joint. However, if the relevant WPS contains data too
detailed and not useful for the welder, dedicated work instructions may be used directly derived from such a
WPS containing only the necessary data. These instructions have to refer directly to the welding procedure
specification they derived from, e.g. by referring to the relevant WPS number.
Considering that welding is a special process and that the quality of the welded joint cannot be properly
controlled only by final tests, the welding procedures significant for the final product quality shall be
qualified precisely prior to production. As a consequence, those Welding Procedure Specifications should be
prepared in accordance with a Welding Procedure Approval Record (WPAR). Normative references to the
specification and to the qualification of welding procedures are given in the table.
Welding
process
Standard
ISO 15607
All fusion
welding
processes
ISO 15610
ISO 15611
ISO 15612
ISO 15613
ISO 15609-2
Gas Welding
Arc welding
ISO 15614 - 1
ISO 15609-1
ISO 15614 1
ISO 15614 2
ISO 15614 3
ISO 15614 4
ISO 15614 5
ISO 15614 6
ISO 15614 –
7
ISO 15614 –
8
Material
Scope Field of application
WPS,
General Rules
WPAR
Qualification based on tested welding
consumables
Qualification based on previous welding
All
experience
WPAR
Qualification by adoption of a standard
welding procedure
Qualification based on pre-production
welding test
WPS Compiling
Steels
Qualification based on welding procedure
WPAR
test – Steels
All
WPS Compiling
Steels and
Qualification based on welding procedure
WPAR
Nickel alloys
test
Aluminium,
Qualification based on welding procedure
WPAR
Magnesium
test
Qualification based on welding procedure
Steel castings WPAR
test
Aluminium
Qualification based on welding procedure
WPAR
castings
test
Titanium and
Qualification based on welding procedure
WPAR
zirconium
test
Qualification based on welding procedure
Copper
WPAR
test
Qualification based on welding procedure
All applicable WPAR test – corrosion resistance overlay,
cladding restore and hardfacing
Qualification based on welding procedure
All applicable WPAR
test - Welding of tubes to tube-plate joints
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contained therein.
Quality Assurance version 1.0
Electron beam
welding
Laser Welding
Underwater Arc
Welding – Wet
Hyperbaric
Underwater Arc
Welding – Dry
Hyperbaric
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ISO 15609 –
All
WPS Compiling
3
ISO 15614 –
Qualification based on welding procedure
All applicable WPAR
11
test
ISO 15609 –
All
WPS Compiling
4
ISO 15614 –
Qualification based on welding procedure
All applicable WPAR
11
test
ISO 15614 –
9
All applicable WPAR
Qualification based on welding procedure
test
ISO 15614 –
10
All applicable WPAR
Qualification based on welding procedure
test
Standards for the qualification of welding procedures
Different methods for the qualification of welding procedures are available:
-
welding procedure test – this method consists in welding a standardised test piece on which destructive
and non-destructive tests are carried out in order to verify the achievement of required properties;
- use of approved welding consumables - this method of approval may be used if the welding consumables
and the base material are not particularly affecting the welding quality, provided that heat inputs are kept
within specified limits;
- previous welding experience - a welding procedure may be qualified by referring to previous experiences
in welding if the Manufacturer is able to prove, by appropriate authentic documentation of an
independent nature, that he has previously satisfactorily welded the same joint with reliable results;
- use of a standard welding procedure – a procedure is qualified if it is issued as a specification in the
format of a WPS or WPAR based on appropriate qualification (e.g based on the relevant part of EN ISO
15614), not related to the Manufacturer and qualified by an examiner or examining body;
- Pre production Test - this method is the only reliable method of qualification for those welding
procedures in which the resulting properties of the weld strongly depend on certain conditions such as:
components, special restraint conditions, heat sinks etc., which cannot be reproduced by standardised test
pieces; it is mostly used when the shape and dimensions of standardised pieces do not adequately
represent the joint to be welded.
Even if different qualification methods are considered, the most commonly used are qualification by welding
procedure test and pre-production test; however the applicable method of qualification is generally specified
in either manufacturing codes, standards or contracts.
In order to demonstrate the achieved quality of the welded product, all the welding related documents shall
be properly controlled.
This involves the preparation and maintenance of a procedure for the management of such documents, in
order to identify issuance responsibilities, distribution methods, availability, and method for withdrawing
obsolete documents. Even if it is not a normative requirement, a commonly adopted method to control
documentation is the production of a written procedure, produced or approved by the welding coordinator, to
be kept by the Manufacturer quality assurance department or directly by the welding coordinator himself.
In the next page a typical WPS form is reported, produced according to EN ISO15609-1.
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the authors, and the Commission cannot be held responsible for any use, which may be made of the information
contained therein.
Quality Assurance version 1.0
COMPANY NAME OR
LOGO
Welding
process(es)
Type(s)
JOINTS –
Joint Type
Backing
Backing material
Weld preparation
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Rev
.
Date
WPS n°
WELDING PROCEDURE
SPECIFICATION (WPS)
Supp. WPQR
a)
b)
c)
a)
b)
c)
Method of preparation & Cleaning
PARENT METAL
Group n°
To group n°
Spec. Type & grade
To Spec. Type & grade
Thickness
Outside Diameter
Other
WELDING CONSUMABLE
Joint drawiing
GAS(ES)
a)
Specification n°
Designation
Size
Trade name
Manufacturer
Flux design. EN
Flux Trade name
Weld deposit
Other
WELDING POSITION
Position
Welding Progression
Other
PREHEAT
Preheat Temperature
Interpass Temperature
Preheat maintenance
Other
b)
c)
Gas(es) Mixture
Plasma
Shielding a)
Shielding b)
Trailing
Backing
Other
ELECTRICAL CHARACTERISTIC Current
Polarity
Mode of Metal
Transfer
Tungsten Electrode Type &
size
Electrode wire feed speed
range
Other
TECHNIQUE
String or weave beads
Orifice or gas cup size
Initial & interpass cleaning
Method of back gouging
Flow Rate
l/min
l/min
l/min
l/min
l/min
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PWHT and/or AGEING
Temperature Range
Time Range (hour)
Heating rate
Cooling rate
Other
Weldin
Run(s)
g
or
proces
Layer(s)
s
Filler metal
EN designation or
trade name .
Size
(mm)
2009.01.30
Oscillati
Amplitud
on
e
Distance contact tube – work
piece
Multiple, single pass (for
side)
Single or multiple electrodes
Torch angle direction of
welding
Other
Current
Voltag Travel
Amperag
e
Speed
Type &
e
V
mm/min
polarity
A
MANUFACTURER
Fre
q.
Heat
input
KJ/mm
Other
APPROVED BY
Welding Procedure Specification
Welding symbols according ISO 22553
The weld joint is where two or more metal parts are joined by welding. The five basic types of weld joints
are the butt, corner, tee, lap, and edge.
Special symbols are used on a drawing to specify where welds are to be located, the type of joint to be used,
as well as the size and amount of weld metal to be deposited in the joint.
A standard welding symbol consists of a reference line, an arrow, and a tail. The reference line becomes the
foundation of the welding symbol. It is used to apply weld symbols, dimensions, and other data to the weld.
The arrow simply connects the reference line to the joint or area to be welded. The direction of the arrow has
no bearing on the significance of the reference line. The tail of the welding symbol is used only when
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necessary to include a specification, process, or other reference information.
The term weld symbol refers to the symbol for a specific type of weld: fillet, groove, surfacing, plug, and slot
are all types of welds. Some of basic weld symbols are shown in the next figures.
Types of butt welds
Single V preparation
preparation
Double V
Types of fillet welds
The leg length of a fillet weld is located in front of the weld symbol (triangle). The dimension is in
millimeters preceded with the letter Z or by the letter ”a”.
In addition to basic weld symbols, a set of supplementary symbols may be added to a welding symbol.
Some of the most common supplementary symbols are shown in the following figure.
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Supplementary symbols
Weld this joint on site
Inspect by NDT, Weld, Paint, etc.
ISO
ISO is a network of the national standards institutes of 157 countries, on the basis of one member per
country, with a Central Secretariat in Geneva, Switzerland, that coordinates the system.
ISO is a non-governmental organization: its members are not, as is the case in the United Nations system,
delegations of national governments. Nevertheless, ISO occupies a special position between the public and
private sectors. This is because, on the one hand, many of its member institutes are part of the governmental
structure of their countries, or are mandated by their government. On the other hand, other members have
their roots uniquely in the private sector, having been set up by national partnerships of industry associations.
Therefore, ISO is able to act as a bridging organization in which a consensus can be reached on solutions that
meet both the requirements of business and the broader needs of society, such as the needs of stakeholder
groups like consumers and users.
The national delegations of experts of a technical committee meet to discuss, debate and argue until they
reach consensus on a draft agreement. This is then circulated as a Draft International Standard (DIS) to ISO's
membership as a whole for comment and balloting. Many members have public review procedures for
making draft standards known and available to interested parties and to the general public. The ISO members
then take account of any feedback they receive in formulating their position on the draft standard. If the
voting is in favour, the document, with eventual modifications, is circulated to the ISO members as a Final
Draft International Standard (FDIS). If that vote is positive, the document is then published as an
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International Standard.
CEN
CEN, the European Committee for Standardization, was founded in 1961 by the national standards bodies in
the European Economic Community and EFTA countries.
CEN supports the policies of the European Union and EFTA, in particular for free trade, but also the safety
of workers and consumers, interoperability of networks, environmental protection, exploitation of research
and development programmes, and public procurement.
Standardization diminishes trade barriers, promotes safety, allows interoperability of products, systems and
services, and promotes common technical understanding.
All standards help build the 'soft infrastructure' of modern, innovative economies. They provide certainty,
references, and benchmarks for designers, engineers and service providers.
In addition, regional or European Standards are necessary for the Single Market and support the Union's
policies for technical integration, protection of the consumer, and promotion of sustainable development.
CE Marking is the symbol as shown. The letters "CE" are the abbreviation of French phrase "Conformité
Européene" which literally means "European Conformity". The term initially used was "EC Mark" and it
was officially replaced by "CE Marking" in the Directive 93/68/EEC in 1993. "CE Marking" is now used
in all EU official documents. "CE Mark" is also in use, but it is NOT the official term.
1. CE Marking on a product is a manufacturer's declaration that the product complies with the essential
requirements of the relevant European health, safety and environmental protection legislations, in
practice by many of the so-called Product Directives.*
*Product Directives contains the "essential requirements" and/or "performance levels" and
"Harmonized Standards" to which the products must conform. Harmonized Standards are the
technical specifications (European Standards or Harmonization Documents) which are
established by several European standards agencies (CEN, CENELEC, etc).
CEN stands for European Committee for Standardization.
CENELEC stands for European Committee for Electro technical Standardization.
2. CE Marking on a product indicates to governmental officials that the product may be legally placed
on the market in their country.
3. CE Marking on a product ensures the free movement of the product within the EFTA & European
Union (EU) single market (total 28 countries), and
4. CE Marking on a product permits the withdrawal of the non-conforming products by customs and
enforcement/vigilance authorities.
Along with more directives' becoming effective, more and more products are required to bear the CE
Marking for gaining access to the EFTA & European Union market.
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the authors, and the Commission cannot be held responsible for any use, which may be made of the information
contained therein.
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MODULE 5
Objective:
Know the principles of basic NDT methods used in welding.
Scope:






Revision of weld imperfections (ISO 6520-1)
Revision of quality levels (ISO 5817)
Checking dimensions, surface and distortion
Surface inspection of cracks and other surface imperfections by visual testing (VT), penetrant testing
(PT) and magnetic particle testing (MT)
Detectability of internal imperfections of welds by radiographic testing (RT) and ultrasonic testing
(UT)
Destructive tests to measure mechanical properties of weld
Expected results:


Perform simple visual inspection of welds to EN 970 and subsequently evaluate to ISO 5817.
Identify the following destructive and non-destructive methods: bend tests, hardness tests, tensile tests
and impact tests, VT, MT, PT, RT and UT.
Inspection and testing
Applicable inspections and tests shall be implemented at appropriate points in the manufacturing process to
assure conformity with contract requirements. Location and frequency of such inspections and/or tests will
depend on the contract and/or product standard, the welding process and the type of construction.
Inspection and testing before welding
Before the start of welding, the following shall be checked:
- suitability and validity of welders’ qualification certificates;
- suitability of welding-procedure specification;
- identity of parent material;
- identity of welding consumables;
- joint preparation (e.g. shape and dimensions);
- fit-up, jigging and tacking;
- any special requirements in the welding-procedure specification (e.g. prevention of distortion);
- arrangement for any production test;
- suitability of working conditions for welding, including environment.
Inspection and testing during welding
During welding, the following shall be checked at suitable intervals or by continuous monitoring:
- essential welding parameters (e.g. welding current, arc voltage and travel speed);
- preheating/interpass temperature;
- cleaning and shape of runs and layers of weld metal;
- back gouging;
- welding sequence;
- correct use and handling of welding consumables;
- control of distortion;
- any intermediate examination (e.g. checking of dimensions).
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the authors, and the Commission cannot be held responsible for any use, which may be made of the information
contained therein.
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Inspection and testing after welding
After welding, the compliance with relevant acceptance criteria shall be checked:
- by visual inspection;
- by non-destructive testing;
- by destructive testing;
- form, shape and dimensions of the construction;
- results and records of post-weld operations (e.g. post-weld heat treatment, ageing).
Inspection and test status
Measures shall be taken, as appropriate, to indicate, e.g. by marking of the item or a routing card, the status
of inspection and test of the welded construction.
Calibration and validation of measuring, inspection and testing equipment
The manufacturer shall be responsible for the appropriate calibration or validation of measuring, inspection
and testing equipment. All equipment used to assess the quality of the construction shall be suitably
controlled and shall be calibrated or validated at specified intervals.
Surface inspection on cracks and other surface imperfections by visual testing
Visual examination is a simple, accessible low - cost inspection method, and it is an excellent processcontrol tool to help avoid subsequent fabrication problems and evaluate workmanship.
Visual inspection only identifies surface discontinuities. Consequently, any conscientious quality control
program should include a sequence of examinations performed during all phases of fabrication.
Visual Inspection is performed in three phases.
I.
II.
III.
Prior to Welding.
During Welding.
After Welding.
I.
Prior to Welding.
Some typical action items requiring attention should include the followings:

Groove angle.

Root openings.

Joint alignment.

Backing.

Consumable insert.

Joint cleanliness.

Tack welds

Preheat (if required)

Identification of filler material

Identification of base material

Verification of competence

Verification of the suitability of the equipment

Verification of Health, Safety and Environment factors
II.
During Welding.
Some typical action items requiring attention by those responsible for weld quality should include the
followings:

Check preheat and interpass temperatures.
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
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Check conformance to Welding Procedure Specification or Weld Schedule.
Examine weld root pass.
Examine weld layers.
Examine second side prior to welding
Any of these factors, if ignored could result in discontinuities that could cause serious degradation.
III.
After Welding.
Following welding, some typical action items requiring attention by the visual inspector should include
followings:

Examination of weld surface quality.

The typical discontinuities found at the surface are as:

Porosity

Lack of fusion

Incomplete joint penetration

Undercut

Underfill

Overlap

Cracks

Metallic and non-metallic inclusions

Excessive and negative reinforcement

Off set

Arc Strikes

Suck back

Overlay

Burn through

Discoloration

Verifying weld dimensions

Verifying dimensional accuracy

Reviewing subsequent requirements
Non destructive evaluation of welded joints
The application of non-destructive testing is highly dependent on the geometrical conditions of the
component, the configuration and accessibility of the joint. This is particularly true for volumetric methods,
radiographic and ultrasonic testing.
The methods for surface testing visual, magnetic particle, penetrant and eddy current are primarily dependent
on the surface conditions and accessibility.
In order to guarantee the application of all the fabrication procedures and the required properties for the
product, appropriate inspections and tests shall be implemented during the manufacturing process
Location and frequency of such inspections and/or tests will depend on the contract and/or product standard,
on the welding process and on the type of construction. As a general rule the state of inspection and testing
of the welded product have to be indicated in some way. Such a means shall be adequate to the type of
product; as an example, a Fabrication and Control Plan may be required for big products (on which the
testing activities are marked); while routing cards or confined space inside the manufacturing plant shall be
sufficient for small series product to indicate the inspection and testing status. The following table reports a
typical chart for tests to be carried out before, during and after welding operations.
In some situations, the signature of the inspector1 shall be required in order to enhance the traceability of the
welding and related process activities. Moreover, the reference number of the relevant test report shall be
1
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included, if required.
All the procedures or instructions relevant to inspection and testing shall be made available to the inspection
personnel, and properly controlled.
As to NDT, testing activities (method, technique and extension) shall be carried out in consideration of and
in accordance with the quality level of the product. Some of those parameters are reported in the
manufacturing codes, where the designer chooses the class of the weld taking into consideration all of the
above mentioned factors. All these aspects should be considered during the design review phase by the
welding coordinator.
Table of verification topics.
TEST
Tests before welding operations
Reference
procedure
Checked Signature of
(date)
the inspector
Reference
report
Suitability and validity of welders
qualification certificates
Suitability of welding procedure
specification
Identity of parent material
Identity of welding consumables
Joint preparation (e.g. Shape and
dimensions)
Fit-up, jigging and tacking
Special requirements in the
welding procedure specification
(e.g. Prevention of distortion)
Arrangement for any production
test
Suitability of working conditions
for welding, including
environment
Tests during welding operations
Preheating / interpass
temperature
Welding parameters
Cleaning and shape of runs
and layers of weld metal;
Back gouging;
Welding sequence;
Correct use and handling of
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welding consumables;
Control of distortion;
Dimensional check
Tests after welding operations
Compliance with acceptance
criteria for Visual Testing
Compliance with acceptance
criteria for other NDT
examinations (e.g.
Radiographic or Ultrasonic
Testing)
Compliance for destructive
testing (when applicable)
Results and records of postwelding operations (e.g.
PWHT)
Dimensional checking.
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MODULE 6
Objective:
Know the effect of welding in terms of shrinkage, residual stresses and distortion. And know how to
minimise distortion before, during and after welding.
Scope:
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




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The thermal cycle in welding
Development of residual stresses due to solidification, cooling and shrinkage
Effects of restraint on residual stress
Significance of residual stress
Preheating, postheating
Relationship between heat input and shrinkage, residual stress and distortion.
Development of distortion; effect of heat input, weld size, penetration, and number of runs single- and
double-sided fillet welded joints and in butt welds.
Corrective measures, procedure, welding technique, sequence, joint preparation, pre-setting
Correction of distortion after welding
Expected results:


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Describe the thermal cycle during welding.
Describe distortion resulting form shrinkage.
Describe residual stresses.
Name measures to minimise distortion.
Describe the main causes for weld shrinkage.
Outline the main effects on a weld due to residual stresses.
Control over the weld distortion
Beginning welders and even those that are more experienced commonly struggle with the problem of weld
distortion, (warping of the base plate caused by heat from the welding arc). Distortion is troublesome for a
number of reasons, but one of the most critical is the potential creation of a weld that is not structurally
sound. This paper will help to define what weld distortion is and then provide a practical understanding of
the causes of distortion, effects of shrinkage in various types of welded assemblies and how to control it, and
finally look at methods for distortion control.
Distortion in a weld results from the expansion and contraction of the weld metal and adjacent base metal
during the heating and cooling cycle of the welding process. Doing all welding on one side of a part will
cause much more distortion than if the welds are alternated from one side to the other. During this heating
and cooling cycle, many factors affect shrinkage of the metal and lead to distortion, such as physical and
mechanical properties that change as heat is applied.
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If we cut through a welded connection and investigate the material, we can, when simplifying, say that the
connection contains three zones:
A. The parent metal which is not influenced by the welding, here shown in brown colour.
B. The heat affected zone, here shown in light blue colour
C. The weld metal, here shown in blue colour.
Zone B and C are of course not so clearly defined in reality because the mixing of molten material takes
place and the structural transfer is a gradual change of structure, but for the understanding of the heat
distortion itself this does not play a major role.
When a metallic material is heated it will expand in all directions. We can illustrate this as shown in figure 1.
The material elements can be visualized as a cube. Before the heating the cube will have a dimension/size as
shown in blue. After heating the dimension /size will expand to the yellow boundaries.
Fig 1. A material with a given dimension/size is heated and it will expand in all directions. If a steel bar is
uniformly heated while unrestrained, it will expand in all directions and return to its original dimensions on
cooling.
However, in welding the heating will be locally causing the surrounding cold material to limit the free
thermal expansion. In figure 2 this is illustrated by showing blue arrows, or forces , that will limit the free
movement of the material.
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Fig 2. The material will try to expand in all direction during heating. However the cold surrounding material
will try to limit the expansion. It is restrained, during heating, and will have a limited expansion. On
cooling, the deformed bar contracts uniformly, and is permanently deformed.
The forces of the surrounding material will cause the internal material structure to be pressed together during
the heating process. Or we may say that the distance between the smallest structural material elements will
be reduced. When the material then cool down, the distance between the smallest structural elements will be
kept, causing the cube to be shortened as shown in the white cube in figure 3.
Fig 3. When cooling down the original material will be shortend of the external forces from the cold material
which press the expanded material together. The resulting cold dimension/size is here shown in white.
However, during the cooling process, the hot material will will shrink and try to drag the surrounding cold
material in the direction it shrinks. The surrounding material must then follow , unless it cracks, causing
deformations to appear.
In a welded joint, these same expansion and contraction forces act on the weld metal and on the base metal.
As the weld metal solidifies and fuses with the base metal, it is in its maximum expanded from. On cooling,
it attempts to contract to the volume it would normally occupy at the lower temperature, but it is restrained
from doing so by the adjacent base metal. Because of this, stresses develop within the weld and the adjacent
base metal. At this point, the weld stretches (or yields) and thins out, thus adjusting to the volume
requirements of the lower temperature. But only those stresses that exceed the yield strength of the weld
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metal are relieved by this straining. By the time the weld reaches room temperature - assuming complete
restraint of the base metal so that it cannot move - the weld will contain locked-in tensile stresses
approximately equal to the yield strength of the metal. If the restraints (clamps that hold the workpiece, or an
opposing shrinkage force) are removed, the residual stresses are partially relieved as they cause the base
metal to move, thus distorting the weldment.
The result will be that very strong forces appears and “drag” the cold material in the direction of the heated
zone and we will consequently get a heat deformation.
Fig 4. The figure shows how much steel will expand when it is heated from 0 degree to 600 degrees.
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Fig 5. Fillet weld. During heating the forces will go in the direction of the yellow arrows. However the
reaction forces from the cold material will cause the molten structure to shrink. The cold material gives
reaction forces as shown with the blue arrows. Cooling down causes the material to bend as shown in figure
6. V
Fig 6. The geometrical form of the fillet weld after cooling down.
A butt weld gives the same problem as we had in a fillet weld. When heating the molten material will try to
expand in the direction of the yellow arrows. Due to the reaction forces from the cold material the size of the
molten material will shrink during the cooling process. The final result when the material cools down is that
the surrounding cold material will be bent in the direction of the blue arrows.
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Fig 7. A butt weld. During the cooling process the material will bend in the direction of the blue arrows. The
design of the bevel causes more molten metal in the top of the bevel than in the bottom of the bevel, resulting
in stronger contracting forces at the top.
If we draw this in another perspective, the plate will look like this.
Fig 8. We see a straight surface, indicated by the dotted line. We also clearly see how the edges of the plate
have been moved upwards caused by the forces earlier described..
In more complex designs and structures, you have to evaluate the heat distortion of each element and see
how these elements fits together.
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Fig 9. In this T-joint we see that the flange is bent as shown in the previous figures. In addition the leg will
get a separate heat distortion and bed as shown. The resulting forces will create a structure as shown here in
this drawing.
Fig 10. The figure shows the results of the heating of the material just at the end of the welding process. We
see that the root opening has increased dramatically due to the heat influence.
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Fig 11. This photo is the same as fig 10, but show the joint connection after the cooling. We see that the
bevel opening has been completely closed. This is due to the contracting forces during the cooling process.
For buttering and cladding the forces will be the same as for a standard butt weld. After welding with heat
input followed by the cooling process, the material will be bent in the direction of the blue arrow.
Fig 12. A cold weld where we see that the heat from the welding process goes in the direction of the white
arrow. The consequtive cooling process causes the material to bend in the direction of the blue arrows.
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Fig 13. A photo of a clad weld as described above. A 3 mm rod has been rolled under the plate which has
bent upwards.
How can we prevent heat distortion ?
To prevent or minimize weld distortion, methods must be used both in design and during welding to
overcome the effects of the heating and cooling cycle. Shrinkage cannot be prevented, but it can be
controlled. Several ways can be used to minimize distortion caused by shrinkage:
Do not overweld.
The more metal placed in a joint, the greater the shrinkage forces. Correctly sizing a weld for the
requirements of the joint not only minimizes distortion, but also saves weld metal and time. The amount of
weld metal in a fillet weld can be minimized by the use of a flat or slightly convex bead, and in a butt joint
by proper edge preparation and fitup. The excess weld metal in a highly convex bead does not increase the
allowable strength in code work, but it does increase shrinkage forces.
When welding heavy plate (over 25 mm thick) bevelling or even double bevelling can save a substantial
amount of weld metal which translates into much less distortion automatically.
In general, if distortion is not a problem, select the most economical joint. If distortion is a problem, select
either a joint in which the weld stresses balance each other or a joint requiring the least amount of weld
metal.
Use intermittent welding
Another way to minimize weld metal is to use intermittent rather than continuous welds where possible. For
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attaching stiffeners to plate, for example, intermittent welds can reduce the weld metal by as much as 75
percent yet provide the needed strength.
Use as few weld passes as possible.
Fewer passes with large electrodes, are preferable to a greater number of passes with small electrodes when
transverse distortion could be a problem. Shrinkage caused by each pass tends to be cumulative, thereby
increasing total shrinkage when many passes are used.
By creating a heat balance in the material.
Fig. 14. During the welding process heating can be added in order to create a heat balance from both sides.
Place welds near the neutral axis
Distortion is minimized by providing a smaller leverage for the shrinkage forces to pull the plates out of
alignment. Both design of the weldment and welding sequence can be used effectively to control distortion.
Balance welds around the neutral axis
This practice offsets one shrinkage force with another to effectively minimize distortion of the weldment.
Here, too, design of the assembly and proper sequence of welding are important factors.
Fig 15. A bad design where the forces will be unsymmetrical, causes a wrong heat balance. The weld is
shown in white.
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Fig 16. A different design solution giving symmetrical heat balance. The weld is shown in white.
Use backstep welding
In the backstep technique, the general progression of welding may be, say, from left to right, but each bead
segment is deposited from right to left As each bead segment is placed, the heated edges expand, which
temporarily separates the plates at B. But as the heat moves out across the plate to C, expansion along outer
edges CD brings the plates back together. This separation is most pronounced as the first bead is laid. With
successive beads, the plates expand less and less because of the restraint of prior welds. Backstepping may
not be effective in all applications, and it cannot be used economically in automatic welding.
Anticipate the shrinkage forces
Presetting parts (at first glance, before welding can make shrinkage perform constructive work. Several
assemblies, preset in this manner. The required amount of preset for shrinkage to pull the plates into
alignment can be determined from a few trial welds.
Pre bending, presetting or pre springing the parts to be welded, is a simple example of the use of opposing
mechanical forces to counteract distortion due to welding. The top of the weld groove - which will contain
the bulk of the weld metal - is lengthened when the plates are preset. Thus the completed weld is slightly
longer than it would be if it had been made on the flat plate. When the clamps are released after welding, the
plates return to the flat shape, allowing the weld to relieve its longitudinal shrinkage stresses by shortening to
a straight line. The two actions coincide, and the welded plates assume the desired flatness.
Another common practice for balancing shrinkage forces is to position identical weldments back to back,
clamping them tightly together. The welds are completed on both assemblies and allowed to cool before the
clamps are released. Pre bending can be combined with this method by inserting wedges at suitable positions
between the parts before clamping.
Be aware of the heat distortion during assembly and assemble the parts so that you work together with the
heat distortion.
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Fig 17. The connection is pre-bent before welding. When the joint has cooled down then the connection will
be flat.
Plan the welding sequence
A well-planned welding sequence involves placing weld metal at different points of the assembly so that, as
the structure shrinks in one place, it counteracts the shrinkage forces of welds already made. An example of
this is welding alternately on both sides of the neutral axis in making a complete joint penetration groove
weld in a butt joint. Another example, in a fillet weld, consists of making intermittent welds according to the
sequences. In these examples, the shrinkage in weld No. 1 is balanced by the shrinkage in weld No. 2.
Clamps, jigs, and fixtures that lock parts into a desired position and hold them until welding is finished are
probably the most widely used means for controlling distortion in small assemblies or components. It was
mentioned earlier in this section that the restraining force provided by clamps increases internal stresses in
the weldment until the yield point of the weld metal is reached. For typical welds on low-carbon plate, this
stress level would approximate 45,000 psi. One might expect this stress to cause considerable movement or
distortion after the welded part is removed from the jig or clamps. This does not occur, however, since the
strain (unit contraction) from this stress is very low compared to the amount of movement that would occur
if no restraint were used during welding.
Minimize welding time.
Since complex cycles of heating and cooling take place during welding, and since time is required for heat
transmission, the time factor affects distortion. In general, it is desirable to finish the weld quickly, before a
large volume of surrounding metal heats up and expands. The welding process used, type and size of
electrode, welding current, and speed of travel, thus, affect the degree of shrinkage and distortion of a
weldment. The use of mechanized welding equipment reduces welding time and the amount of metal
affected by heat and, consequently, distortion. For example, depositing a given-size weld on thick plate with
a process operating at 175 amp, 25 volts, and 75mm/min requires 87,500 joules of energy per linear 25 mm
of weld (also known as heat input). A weld with approximately the same size produced with a process
operating at 310 amp, 35 volts, and 200mm/min requires 81,400 joules per linear 25mm. The weld made
with the higher heat input generally results in a greater amount of distortion.
A Check-list to Minimize Distortion
In summary, follow the check-list below in order to minimize distortion in the design and fabrication of
weldments:
 Do not overweld.
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Control fit up.
Use intermittent welds where possible and consistent with design requirements.
Use the smallest leg size permissible when fillet welding.
For groove welds, use joints that will minimize the volume of weld metal. Consider double-sided
joints instead of single-sided joints.
Weld alternately on either side of the joint when possible with multiple-pass welds.
Use minimal number of weld passes.
Use low heat input procedures. This generally means high deposition rates and higher travel speeds.
Use welding positioners to achieve the maximum amount of flat-position welding. The flat position
permits the use of large-diameter electrodes and high-deposition-rate welding procedures.
Balance welds about the neutral axis of the member.
Distribute the welding heat as evenly as possible through a planned welding sequence and weldment
positioning.
Weld toward the unrestrained part of the member.
Use clamps, fixtures, and strongbacks to maintain fit up and alignment.
Pre bend the members or pre-set the joints to let shrinkage pull them back into alignment.
Sequence sub assemblies and final assemblies so that the welds being made continually balance each
other around the neutral axis of the section.
Following these techniques will help minimize the effects of distortion and residual stresses.
Preheating, interpass and post heating to prevent hydrogen cracking
There are three factors which combine to cause cracking in arc welding:



hydrogen generated by the welding process
a hard brittle structure which is susceptible to cracking
tensile stresses acting on the welded joint
Cracking generally occurs when the temperature has reached normal ambient. In practice, for a given
situation (material composition, material thickness, joint type, electrode composition and heat input), the risk
of hydrogen cracking is reduced by heating the joint.
Preheat
Preheat, which slows the cooling rate, allows some hydrogen to diffuse away, and prevents a hard, cracksensitive structure being formed. The recommended levels of preheat for carbon and carbon manganese steel
are detailed in EN 1011-2: 2001. The preheat level may be as high as 200°C for example, when welding
thick section steels with a high carbon equivalent (CE) value.
Interpass and post heating
As cracking rarely occurs at temperatures above ambient, maintaining the temperature of the weldment
during fabrication is equally important. For susceptible steels, it is usually appropriate to maintain the
preheat temperature for a given period, typically between 2 to 3 hours, to enable the hydrogen to diffuse
away from the weld area. In crack sensitive situations such as welding higher CE steels or under high
restraint conditions, the temperature and heating period should be increased, typically 250-300°C for three to
four hours.
Post-weld heat treatment (PWHT) may be used immediately on completion of welding, i.e. without allowing
the preheat temperature to fall. However, in practice, as inspection can only be carried out at ambient
temperature, there is the risk that 'rejectable,' defects will only be found after PWHT. Also, for highly hard
enable steels, a second heat treatment may be required to temper the hard micro structure present after the
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first PWHT.
Under certain conditions, more stringent procedures are needed to avoid cracking. C2 of EN 1011-2. Section
C.2.9 of this standard mentions the following conditions:
a. high restraint, including welds in section thickness's above approximately 50mm, and root runs in
double bevel joints
b. thick sections ( approximately 50mm)
c. low carbon equivalent steels (CMn steels with C 0.1% and CE approximately 0.42)
d. 'clean' or low sulphur steels (S approximately 0.008%), as a low sulphur and low oxygen content
will increase the harden ability of a steel.
e. alloyed weld metal where preheat levels to avoid HAZ cracking may be insufficient to protect the
weld metal. Low hydrogen processes and consumables should be used. Schemes for predicting the
preheat requirements to avoid weld metal cracking generally require the weld metal diffusible
hydrogen level and the weld metal tensile strength as input.
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MODULE 7
Objective:
Know about imperfections in welds.
Scope:
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

Origin of imperfections: parent metal; welding process; welder; joint preparation
Survey of specific weld imperfections and their cause
Influence of weld imperfections on product performance
Influence of the weld geometry on the fatigue life of the product
Expected results:

Identify and describe the cause of: gas pores, incomplete penetration, lack of fusion and cracks (see
also the specific modules “S” on welding processes .
Non destructive examination (NDE) methods of inspection make it possible to verify compliance to the
standards on an ongoing basis by examining the surface and subsurface of the weld and surrounding base
material. Five basic methods are commonly used to examine finished welds: visual, liquid penetrant,
magnetic particle, ultrasonic and radiographic (X-ray). The growing use of computerization with some
methods provides added image enhancement, and allows real-time or near real-time viewing, comparative
inspections and archival capabilities. A review of each method will help in deciding which process or
combination of processes to use for a specific job and in performing the examination most effectively.
Visual Inspection (VT)
Visual inspection is often the most cost-effective method, but it must take place prior to, during and
after welding. Many standards require its use before other methods, because there is no point in
submitting an obviously bad weld to sophisticated inspection techniques. The ISO 5817 states,
"Welds subject to non-destructive examination shall have been found acceptable by visual
inspection." Visual inspection requires little equipment. Aside from good eyesight and sufficient
light, all it takes is a pocket rule, a weld size gauge, a magnifying glass, and possibly a straight edge
and square for checking straightness, alignment and perpendicularity. Before the first welding arc is
struck, materials should be examined to see if they meet specifications for quality, type, size,
cleanliness and freedom from defects. Grease, paint, oil, oxide film or heavy scale should be
removed. The pieces to be joined should be checked for flatness, straightness and dimensional
accuracy. Likewise, alignment, fit-up and joint preparation should be examined. Finally, process and
procedure variables should be verified, including electrode size and type, equipment settings and
provisions for preheat or postheat. All of these precautions apply regardless of the inspection method
being used.
During fabrication, visual examination of a weld bead and the end crater may reveal problems such
as cracks, inadequate penetration, and gas or slag inclusions. Among the weld detects that can be
recognized visually are cracking, surface slag in inclusions, surface porosity and undercut.
On simple welds, inspecting at the beginning of each operation and periodically as work progresses
may be adequate. Where more than one layer of filler metal is being deposited, however, it may be
desirable to inspect each layer before depositing the next. The root pass of a multipass weld is the
most critical to weld soundness. It is especially susceptible to cracking, and because it solidifies
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quickly, it may trap gas and slag. On subsequent passes, conditions caused by the shape of the weld
bead or changes in the joint configuration can cause further cracking, as well as undercut and slag
trapping. Repair costs can be minimized if visual inspection detects these flaws before welding
progresses.
Visual inspection at an early stage of production can also prevent underwelding and overwelding.
Welds that are smaller than called for in the specifications cannot be tolerated. Beads that are too
large increase costs unnecessarily and can cause distortion through added shrinkage stress.
After welding, visual inspection can detect a variety of surface flaws, including cracks, porosity and
unfilled craters, regardless of subsequent inspection procedures. Dimensional variances, warpage and
appearance flaws, as well as weld size characteristics, can be evaluated.
Before checking for surface flaws, welds must be cleaned of slag. Shot-blasting should not be done
before examination, because the peening action may seal fine cracks and make them invisible.
Visual inspection can only locate defects in the weld surface. Specifications or applicable codes may
require that the internal portion of the weld and adjoining metal zones also be examined. Nondestructive examinations may be used to determine the presence of a flaw, but they cannot measure
its influence on the serviceability of the product unless they are based on a correlation between the
flaw and some characteristic that affects service. Otherwise, destructive tests are the only sure way to
determine weld serviceability.
Visual Inspection should be carried out by the welder itself as a part of the own approval of the
work.
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However due to industrial and stand requirements that it also is a special task for the Visual
Inspector verifying that the job done by the welder is appropriate.
The ISO 5817:2003 provides quality levels of imperfections in fusion-welded joints (except for beam
welding) in all types of steel, nickel, titanium and their alloys. It applies to material thickness above 0,5 mm.
This standard is a reference standard used within the scope of the Visual Inspection.
Three quality levels are given in order to permit application to a wide range of welded fabrication. They are
designated by symbols B, C and D. Quality level B corresponds to the highest requirement on the finished
weld. The quality levels refer to production quality and not to the fitness-for-purpose of the product
manufactured.
ISO 5817:2003 applies to:
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unalloyed and alloy steels;
nickel and nickel alloys;
titanium and titanium alloys;
manual, mechanized and automatic welding;
all welding positions;
all types of welds, e.g. butt welds, fillet welds and branch connections;
the following welding processes and their defined sub-processes in accordance with ISO 4063:
 11 metal-arc welding without gas protection;
12 submerged-arc welding;
13 gas-shielded metal-arc welding;
14 gas-shielded welding with non-consumable electrodes;
15 plasma arc welding;
31 oxy-fuel gas welding (for steel only).
In addition the ISO 6520 Welding and allied processes -- Classification of geometric imperfections in
metallic materials -- Part 1: Fusion welding gives an in depth specification of the welding defect and the
accept criteria.
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Defects/imperfections in welds - porosity
The characteristic features and principal causes of porosity
imperfections are described. Best practice guidelines are given so
welders can minimise porosity risk during fabrication.
Identification
Porosity is the presence of cavities in the weld metal caused by the
freezing in of gas released from the weld pool as it solidifies. The
porosity can take several forms:
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distributed
surface breaking pores
wormhole
crater pipes
Cause and prevention
Distributed porosity and surface pores
Distributed porosity (Fig. 1) is normally found as fine pores throughout the weld bead. Surface breaking
pores (Fig. 2) usually indicate a large amount of distributed porosity
Fig. 1. Uniformly distributed porosity
Fig. 2. Surface breaking pores (T fillet weld in primed plate)
Cause
Porosity is caused by the absorption of nitrogen, oxygen and hydrogen in the molten weld pool which is then
released on solidification to become trapped in the weld metal.
Nitrogen and oxygen absorption in the weld pool usually originates from poor gas shielding. As little as 1%
air entrainment in the shielding gas will cause distributed porosity and greater than 1.5% results in gross
surface breaking pores. Leaks in the gas line, too high a gas flow rate, draughts and excessive turbulence in
the weld pool are frequent causes of porosity.
Hydrogen can originate from a number of sources including moisture from inadequately dried electrodes,
fluxes or the workpiece surface. Grease and oil on the surface of the workpiece or filler wire are also
common sources of hydrogen.
Surface coatings like primer paints and surface treatments such as zinc coatings, may generate copious
amounts of fume during welding. The risk of trapping the evolved gas will be greater in T joints than butt
joints especially when fillet welding on both sides. Special mention should be made of the so-called weldable
(low zinc) primers. It should not be necessary to remove the primers but if the primer thickness exceeds the
manufacturer's recommendation, porosity is likely to result especially when using welding processes other
than MMA.
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Prevention
The gas source should be identified and removed as follows:
Air entrainment
- seal any air leak
- avoid weld pool turbulence
- use filler with adequate level of deoxidants
- reduce excessively high gas flow
- avoid draughts
Hydrogen
- dry the electrode and flux
- clean and degrease the workpiece surface
Surface coatings
- clean the joint edges immediately before welding
- check that the weldable primer is below the recommended maximum thickness
Wormholes
Characteristically, wormholes are elongated pores (Fig. 3) which produce a herring bone appearance on the
radiograph.
Elongated pores or wormholes
Cause
Wormholes are indicative of a large amount of gas being formed which
is then trapped in the solidifying weld metal. Excessive gas will be
formed from gross surface contamination or very thick paint or primer
coatings. Entrapment is more likely in crevices such as the gap beneath
the vertical member of a horizontal-vertical, T joint which is fillet
welded on both sides.
When welding T joints in primed plates it is essential that the coating
thickness on the edge of the vertical member is not above the
manufacturer's recommended maximum, typically 20µm, through overspraying.
Prevention
Eliminating the gas and cavities prevents wormholes.
Gas generation
- clean the workpiece surfaces
- remove any coatings from the joint area
- check the primer thickness is below the manufacturer's maximum
Joint geometry
- avoid a joint geometry which creates a cavity
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the authors, and the Commission cannot be held responsible for any use, which may be made of the information
contained therein.
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Crater pipe
A crater pipe forms during the final solidified weld pool and is often associated with some gas porosity.
Cause
This imperfection results from shrinkage on weld pool solidification. Consequently, conditions which
exaggerate the liquid to solid volume change will promote its formation. Switching off the welding current
will result in the rapid solidification of a large weld pool.
In TIG welding, autogenous techniques, or stopping the wire before switching off the welding current, will
cause crater formation and the pipe imperfection.
Prevention
Crater pipe imperfection can be prevented by removing the stop or by welder technique.
Removal of stop
- use run-off tag in butt joints
- grind out the stop before continuing with the next electrode or depositing the subsequent weld run
Welder technique
- progressively reduce the welding current to reduce the weld pool size
- add filler (TIG) to compensate for the weld pool shrinkage
Porosity susceptibility of materials
Gases likely to cause porosity in the commonly used range of materials are listed in the Table.
Principal gases causing porosity and recommended cleaning methods
Material
Gas
Cleaning
C-Mn steel
Hydrogen, Nitrogen and
Oxygen
Grind to remove scale coatings
Stainless steel
Hydrogen
Degrease + wire brush + degrease
Aluminium and alloys Hydrogen
Chemical clean + wire brush + degrease +
scrape
Copper and alloys
Hydrogen, Nitrogen
Degrease + wire brush + degrease
Nickel and alloys
Nitrogen
Degrease + wire brush + degrease
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the authors, and the Commission cannot be held responsible for any use, which may be made of the information
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MODULE 8
Objective:
Have knowledge about identification and traceability
Scope:
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Introduction of ISO 3834: Quality Requirements for Welding
Implication of failure; product liability
ISO 3834 and product documentation
Expected results:
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Introduction of ISO 3834: Quality Requirements for Welding
Identify the key documents for identification and traceability
Identify actions to maintain identification and traceability through the production process
Delivery of the product.
Manufacturing processes such as fusion welding are widely used to produce many products, and for some
companies, these are the key production features. Products may range from simple to complex; examples
include pressure vessels, domestic and agricultural equipment, cranes, bridges, transport vehicles and other
items.
These processes exert a profound influence on the cost of manufacture and on the quality of the product. It is
therefore important to ensure that these processes are carried out in the most effective way and that
appropriate control is exercised over all aspects of the operation. In general, ISO 9001 standard has been
developed in order to apply a consistent Quality Management System.
However, surface coating, painting, composite manufacture, welding and brazing are considered as “special
processes” because the quality of the manufactured product cannot be readily verified by final inspection. In
the case of welded products, quality cannot be inspected directly in the product, but has to be built in during
fabrication, as even the most extensive and sophisticated non-destructive testing does not improve the quality
of the product.
For this reason quality management systems alone may be insufficient to provide adequate assurance that
these processes have been carried out correctly. Special controls and requirements are usually needed, which
require adequate competence control before, during and after operation. For products to be free from serious
problems during production and in service, it is necessary to provide controls from the design phase through
material selection, into manufacture and subsequent inspection. For example, poor design may create serious
and costly difficulties in the workshop, on site, or in service; incorrect material selection may result in
problems, such as cracking in welded joints.
To ensure sound and effective manufacturing, the management needs to understand and appreciate the
sources of potential problems and to implement appropriate procedures for their control.
The EN ISO 3834,is more process oriented and attentive to the technical aspects; in fact:
- not only the quality manual is unneeded as before,
- but even the unwritten praxis, rooted on a specific technical competence, tend often to replace, with
an equal value, the documented procedures.
Even the non-conformances appear to be primarily evaluated depending on whether they affect or not (and if
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yes, in what extent) the product real quality (instead of to be only a breach to the quality system), leading
therefore to a process oriented assessment.
Identification and traceability
Identification of pieces and parts, and the possibility to retrace their position during the manufacturing stages
and when delivered to the customer is one of the most effective way to achieve quality of the product and to
have feedback about its functionality.
However, it shall be noted that identification and traceability can imply expensive procedures and are
therefore not required by the ISO 3834 standard. However, they can be required by standards, fabrication
codes or by the customer himself.
Whenever required, it shall be maintained during the manufacturing process, which means that for every
piece or component it shall be possible to retrieve its history by marking the parts and controlling the
relevant documentation. Documented systems to ensure identification and traceability of the welding
operations shall include:
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identification of production plans;
identification of routing cards;
identification of weld locations in construction;
identification of non-destructive testing procedures and personnel;
identification of welding consumable (e.g. designation, trade name, Manufacturer of consumables and
batch or cast numbers);
identification and/or traceability of parent material (e.g. type, cast number);
identification of location of repairs;
identification of location of temporary attachments;
traceability for fully mechanised and automatic weld-equipment for specific welds;
traceability of welder and welding operators of specific welds;
traceability of welding procedure specification of specific welds.
Quality records
Quality records shall be retained for a minimum period of five years in the absence of any other specified
requirements.
Quality records shall include, when applicable:
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record of requirement/technical review;
material certificates;
welding consumable certificates;
welding procedure specifications;
equipment maintenance records;
welding procedure approval records (WPAR);
welder or welding operator qualification certificates;
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production plan;
non-destructive testing personnel certificates;
heat treatment procedure specification and records;
non-destructive testing and destructive testing procedures and reports;
dimensional reports;
records of repairs and non-conformance reports.
Non-conformance and corrective actions
Measures shall be implemented to control items or activities, which do not conform to specified requirements
in order to prevent their inadvertent acceptance. When repair and/or rectification is undertaken by the
manufacturer, descriptions of appropriate procedures shall be available at all workstations where repair or
rectification is performed. When repair is carried out, the items shall be re-inspected, tested and examined in
accordance with the original requirements. Measures shall also be implemented to avoid recurrence of nonconformances.
This project has been funded with support from the European Commission. This publication reflects the views only of
the authors, and the Commission cannot be held responsible for any use, which may be made of the information
contained therein.