The requirement for
weld procedures and the coding of welders is specified in application standards
such as:
-
BS 2971 Class 2 Arc Welding of Carbon
Steel Pipework {Gas Pressures less than 17 barg}
-
BS 2633 Class 1 Arc Welding of Carbon
Steel Pipework
-
BS 4677 Arc Welding Of Austenitic Steel
Pipework.
-
BS 806 Boiler Pipe Work (Refers to
BS 2971 and BS 2633)
-
PD 5500 Unfired Pressure Vessels (Formally
BS5500)
-
BS 2790 Shell Boilers
-
BS 1113 Water Tube Boilers
-
BS 5169 Air Receivers
|
Application Standards
All the above application standards
require welding procedures to EN ISO 15614 Part 1 (Formerly BSEN 288-3)
and welders coded to BSEN 287 Part 1. Some applications of BS 2971 and BS
5169 permit welders to be qualified without procedures to BS
4872, a less stringent standard. |
| The application standard may require
tests in addition to those required by welding standards, for example most
UK boiler and pressure vessel codes require all weld tensile tests for
plate qualification above 10mm.
UK pressure systems regulations
Items that come under the UK pressure
systems regulations must be 'properly designed and constructed so as to
prevent danger', and items that are repaired or modified should not give
rise to danger. The Health and Safety Executive Guidance Booklet to the
regulations interprets this statement as meaning the manufacture or repair
of any item should be carried out to suitable codes and recommends the
use of British Standards or other equivalent National Standards.
European Pressure Equipment Directive
For inspection category 2 and above
all welding procedures and welder qualifications have to be approved by
a Notified Body (an Inspection Authority Notified by a European member
country under the Directive), or a Third Party Organisation similarly approved
under the Directive. All qualifications approved by these organisations
have to be accepted by all parties for work carried out under the directive
providing they are suitable for the application and technically correct.
Welding Procedure Specifications
This is a simple instruction sheet
giving details of how the weld is to be performed, its purpose is to aid
the planning and quality control of the welding operation. EN ISO 15609 (formerly EN288 Part 2)
specifies the contents of such a specification in the form of a list of
items that should be recorded, however only relevant information need be
specified, for example only in the case of a procedure requiring heat input
control would there be a necessity to quote travel speed or run out length
for manual processes. |
| A weld procedure specification
may cover a range of thicknesses, diameters and materials, but the range
must be specified and be compatible with the rest of the parameters on
the document. I suggest that you produce a new WPS for each type of joint
and keep to the ranges of thickness and diameters specified in the welding
procedure standard. |
Welding Procedures
Welding procedures are required
when it is necessary to demonstrate that your company has the ability to
produce welds possessing the correct mechanical and metallurgical properties. |
| A welding procedure must qualified
in accordance with the requirements of an appropriate welding procedure
standard such as EN ISO 15614 Part 1 as follows:- |
-
Produce a welding procedure specification
as stated above.
-
Weld a test piece in accordance with
the requirements of your specification. The joint set up, welding and visual
examination of the completed weld should be witnessed by an Inspection
Body. The details of the test such as the welding current, pre-heat etc.,
must be recorded during the test.
-
Once the welding is complete the test
piece must be subject to destructive and non destructive examination such
as radiography and mechanical tests as defined by the welding procedure
standard. This work can be carried out in any laboratory but the Inspection
Body may require to witness the tests and view any radiographs.
-
If the test is successful you or the
test body complete the appropriate documents which the test bodies surveyor
signs and endorses. The necessary documents are as follows:-
|
| E1 |
Welding Procedure Approval Test
Certificate
This is the front sheet and only
gives details of what the procedure can be used for. i.e. its range of
approval. |
| E2 |
Details Of Weld Test
This gives details of what actually
took place during the test weld it is similar to a WPS but should not include
ranges of welding parameters. |
| E3 |
Test Results
Details of NDT and Mechanical testing
Results |
| E4 |
Welder Approval Test Certificate.
This is the welder approval part
of the qualification. |
|
| Note The E1, E2, E3, E4
designations are used by some Inspection Authorities to refer to the individual
forms. Examples of these forms are given in annexes of EN ISO 15614 and EN287.
Forms E1, E2, E3 may be referred
to as the WPAR (Welding Procedure Approval Record) or WPQR (Weld Procedure
Qualification Record). |
| In general a new welding procedure
must be qualified for each of the following changes subject to the individual
requirements of the appropriate standard used:- |
-
Change in parent material type.
-
Change of welding process
-
The diameter range for pipe given by
the welding standard is exceeded. Typically 0.5xD to 2xD.
-
The thickness range is exceeded. Typically
0.5xt to 2xt.
-
Any other change required by the welding
standard.
|
Welder Approval
Once the procedure is approved
it is necessary to demonstrate that all your welders working to it have
the required knowledge and skill to put down a clean sound weld. If the
welder has satisfactorily completed the procedure test then he is automatically
approved but each additional welder must be approved by completing an approval
test to an appropriate standard such as EN 287 part 1 as follows:- |
Complete a weld test as stated
in 2) above. The test should simulate production conditions and the welding
position should be the position that the production welds are to be made
in or one more severe
For maximum positional approval
a pipe inclined at 45 degrees (referred to as the 6G position) approves
all positions except vertical down.
Test the completed weld in accordance
with the relevant standard to ensure that the weld is clean and fully fused.
For a butt weld this is normally
a visual examination followed by radiography.
Once the test is completed the E4
form has to be completed by you or the test body and signed by the test
bodies surveyor.
Note The above changes that require
a new welding procedure may also apply to the welders approval, refer to
the standard for precise details.
|
ASME 9
ASME 9 as far as the pressurised
systems regulations are concerned can be considered as equivalent to EN ISO 15614-1
/EN 287. However it may not be contractually acceptable. The
advantage in using ASME is that generally fewer procedure tests are required particularly when
welding pipework.
Welder Approval Without A procedure
BS 4872 is for the qualification
of welders where a weld procedure is not required either by the application
standard that governs the quality of production welds or by contractual
agreement. Typically applied per BS2971 for welding of boiler pipework
less than 17 bar g and 200°C. Basically the same rules mentioned above
for the welder approval apply.
Acceptance Standards
In general welds must show a neat
workman like appearance. The root must be fully fused along the entire
length of the weld, the profile of the cap should blend in smoothly with
the parent material and the weld should be significantly free from imperfections.
Reference should be made to the acceptance standard for precise details. |
| Its a good idear to ensure that
you can achieve the appropriate standard before you call in an Inspection
Body. Penetration defects and lack of fusion can often be easily detected
by sectioning welds and bending them. |