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ASME Section 9 Short Notes
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INDEX
1. INTRODUCTION TO ASME CODES
2. WPS AND PQR
3. GUIDELINES FOR MAKING WPS AND PQR
4. WELDING VARIABLES
5. SOME IMPORTANT CLAUSES RELATING TO
THE WPS.
Page 1 of 29
1. INTRODUCTION TO ASME CODES: -
In industries, a number of equipments like power boilers,
pressure vessels exist which are operational at extreme conditions
such as high pressure, temperature etc. extreme caution has to be
taken to ensure that such equipments work properly and safely in
the required operating conditions. Hence, construction of boilers,
pressure vessels, and other components in a manufacturing plant
is not carried out directly but is done in a methodical fashion
following certain codes and specification.
In order to manufacture, considering safety and optimum cost
of such industrial equipments various codes, standards &
specification are available as reference guidelines. Numbers of
industries have published guidelines to be followed in fabrication
of equipment to obtain best result at maximum safety and
economy. These guidelines act as assurances of high standards of
quality as well as safety in construction and use. Some of the
sundry of codes established are BS, DIN, ASME, IS codes etc.
Out of these, the ASME codes are most widely used due to its
winder applicability and wealth of experience involves in its
preparation. It is important to note that the codes established only
serve as guidelines for safety and ease of construction but are not
a compulsion on the manufacturer who has the freedom to out for
a method of his choice or liking.
The ASME codes are standard rules established as a result
of setting of a committee of American Society of Mechanical
Page 2 of 29
Engineering in 1911 for the purpose of formulating standard rules for
the construction of steam boilers and other pressure vessel. ASME
codes are guidelines covering the safety of design, fabrication, and
inspection during the construction of pressure vessels and boilers.
The codes serve as guidelines for care and good practice for the ease
and safety of construction only and they do not limit the freedom of
the manufacturing firm to choose any method or design of
manufacture of its liking.
The ASME codes are subjected to constant review and are
regularly updated with change in technology, new researches taking
place and new developments.
ASME boiler and pressure vessel codes used in
manufacturing of pressure vessels are made up of number of section
relating to various aspects of the fabrication of boilers and vessels.
Following are the section of ASME code for boiler and pressure
vessels.
Section I : Power Boilers
Section II : Material specification
Part A : Ferrous materials.
Part B : Non ferrous material.
Part C : Welding Rods, Electrodes and Filler Metals.
Section III : Nuclear power plant components.
Section IV : Heating Boilers.
Section V : Non-destructive examination.
Section VI : Care and operation of heating boilers. Page 3 of 29
Section VII : Care of power boilers.
Section VIII : Pressure vessel.
Div. I : Rules for construction of pressure vessel.
Div. II : Alternative rules for construction of pressure vessel
Section IX : Welding and brazing qualification.
Section X : Fiber glass reinforced plastic pressure vessel.
Section XI : In service inspection of nuclear reactor coolant
system.
All these sections of ASME codes impose control on the
construction of the various production equipment but are mainly
concerned with safety, ease and economy of construction.
Page 4 of 29
2. WPS AND PQR: -
2.1 WELDING PROCEDURE SPECIFICATION: -
The purpose of welding procedure specification and procedure
qualification record is to determine that weldment proposed for
construction is capable of having the required properties for its intended
application. It is presupposed that the welder or welding operator
performing the welding procedure qualification test is a skilled
workman. The welding procedure qualification test establishes the
properties of the weldment, not the skill of the welder or welding
operator. In addition to this general requirement, other section of the
code requires special consideration for notch toughness.
Briefly, a WPS lists the variables, both essential and non –
essential, and the acceptable range of these variables when using the
WPS. The WPS is like a manual which gives direction for the welding
operator / welder.
The WPS lists the various parameters of the joints required during
welding such as base metal used, filler wire, gas, electrical
characteristics, post weld heat treatment, position, technique, etc.
Page 5 of 29
2.2 PROCEDURE QUALIFICATION RECORD: -
Procedure qualification record lists the parameters used in
qualification of the WPS and also records the test results. It records the
actual parameters used during the qualification of the test piece. It also
records the results of the various tests such as tensile test, bend test,
toughness tests, etc. depending on the requirements as mentioned in
various clauses of the section IX. It is a proof of the quality of the
weldment – whether it is to the required standard or not.
Page 6 of 29
3. GUIDELINES FOR MAKING WPS / PQR.
3.1 STEPS FOR MAKING A WPS: -
Some guidelines for making a WPS are as follows: -
Refer the appropriate P – Number and Group – Number
and / or S – Number of the parent metals to be welded as
given in QW – 422.
Choose the appropriate filler metal (wire, electrode, flux,
cored wire etc.) according to the mechanical and
chemical properties required to specifications or section
II part C of ASME codes for pressure vessels and boilers.
Note the SFA classification and AWS class of the
required filler metal if given.
Take reference of the F – Number according to the SFA
classification as given in QW – 432 (For ferrous
materials only).
For non – ferrous metals the F – Number specifications is
not required.
According to the chemical composition designate the A –
Number according to that given in QW – 442.
Page 7 of 29
Note down the post weld heat treatment conditions for
the use in production welds in accordance with the
conditions listed in QW – 407.
Mention about the various electrical parameters to be
used in weldment considering the restrictions given in
QW – 409.
Enter the details about the gas (shielding, trailing,
backing) along with its composition and flow rate (for
GTAW / FCAW) in accordance with the restrictions of
QW – 408.
Enter the information about the technique used such as
single / multiple pass, single / multiple electrode,
cleaning required, method of backing gouging, peening
required, etc.
Mention the details of the deposited welded thickness
and thickness range qualified as follows:
a) In case of procedure qualification the thickness qualifies
is according to QW – 450 and QW – 451 for groove and
fillet welds.
b) In case of performance qualification the thickness
qualified is according to QW – 452 for groove and fillet
welds.
Page 8 of 29
c) For hard – facing and corrosion resistant overlays the
qualification is according to QW – 453.
The details of alternate F – Numbers qualified by the
welder for use in production welding is given in QW –
433.
Mention the details of the process, layer, filler metal,
current, voltage, polarity, travel speed, etc. as used the
weldment in the WPS.
3.2 STEPS FOR MAKING A PQR: -
The PQR contains the record of the actual variables used in the
weldment during testing.
Most of the parameters in PQR are same as that present
in the WPS. However, some point to be taken care of
while making a PR are as follows: -
a) A detail about the joint being welded is a must;
hence the dimensions of the test coupon must be
mentioned. The dimensions of the test piece for
procedure qualification shall be according to QW –
202, for 302 for performance qualification.
Page 9 of 29
b) The PQR must contain the exact parameters such
as current, voltage, filler wire size, etc. that has
been used in qualification of the test coupon.
c) It should contain the results of the various tests
carried out in weldment according to the code.
d) In case of procedure qualification the various tests
shall be done in accordance with QW – 202 for
various joints like fillets, grooves, etc. while that
for performance qualification the tests will be in
accordance with QW – 302.
Page 10 of 29
4.0 WELDING VARIABLES: -
As mentioned earlier there are number of parameters which affect
the chemical and mechanical properties of the weldment. Also the weld
– joint prepared by the welder also is affected by change in the
parameters such as position, etc. hence the various welding variables for
procedure and performance qualification are subdivided into essential
variables, supplementary essential variables, and non – essential
variables.
4.1 ESSENTIAL VARIABLES: -
Essential variables are those in which a change, as described
in the specific variables, is considered to affect the mechanical
properties of the weldment, and shall require requalification of the WPS.
It is a change in welding condition, which may affect the properties of
the weld or may affect the soundness of the weld deposit made by the
welding operator / welder.
E.G. change in P – Number or F – Number, welding process, filler
metal, deletion or addition of backing, change in shielding / trailing /
backing gas etc.
4.2 SUPPLEMENTARY ESSENTIAL VARIABLES: -
A change in weld condition, which will affect the notch
toughness properties of a weldment, is a supplementary essential
variable. It is required for metals for which other section specify notch
Page 11 of 29
toughness tests and are in addition to the essential variables for each
welding process.
E.G. change in welding process, uphill or down vertical welding etc.
4.3 NON – ESSENTIAL VARIABLES: -
A change in a welding condition, which will not affect the
mechanical properties of a weldment, is a non – essential variables. A
change in such variables does not requalification of the WPS.
The various essential and non – essential variables affecting
the WPS and PQR for different processes are listed in QW – 250 to QW
– 264.1 for procedure qualification and QW – 350 to QW – 382 for
performance qualification
Page 12 of 29
5. SOME IMPORTANT CLAUSES RELATING TO
THE WPS: -
Following are a few details of few clauses which explain the
variables to be considered for specification / qualification /
requalification for a WPS, WPQ or PQR.
5.1 FILLER METAL ( QW – 404 ): -
QW 404 states about the filler metal used in welding the
joints. It shows the changes in filler metal characteristics in
the weld joint.
It states that:
A change in F – number requires re-qualification except as
permitted in QW- 433.
Also a change in SFA specification requires re-
qualification.
When a filler metal conforms to an SFA specification
classification, re- qualification is not required if a change is
made in any one of the following:
Page 13 of 29
a) From a filler metal which is designated as moisture-
resistant to one that is not designated as moisture –
resistant and vice versa e.g. E 7018R to E7018.
b) From one diffusible hydrogen level to another e.g. from
E7018-H8 to E7018-H16.
c) For carbon, low alloy, and stainless steel filler metals
having the same minimum tensile strength and nominal
chemical composition, a change from one low hydrogen
coating type to another low hydrogen coating type e.g.
EXX15, 16 or EXXX15, 16 or 17 classification.
d) From one position-usability designation to another for
flux cored electrodes e.g. E 70T-1 to E 71T-1 or vice
versa.
e) From a classification which requires impact testing to
the same classification which has a suffix which
indicates that impact testing was performed at a lower
temperature or exhibited greater toughness at the
required temperature or both, as compared to the
classification which was used during procedure
qualification e.g. E 7018 to E 7018-1.
Page 14 of 29
f) From the classification qualified to another filler metal
within the same SFA specification when the weld metal
is exempt from impact testing.
Designation of the nominal composition may be given
by reference to AWS classification or A-number
designation.
A change in weld deposit made beyond the range
qualified again requires re-qualification.
NOTE: - QW-433 lists the qualification range for F-
number during qualification testing.
5.2 JOINTS (QW- 402 ): -
QW-402 states about the variation in the various types of
grooves, backing gas/material used and the various other
parameter \s affecting the characteristics of the welded joint.
A change in type of groove (Vee- groove, U – groove,
Single – bevel, Double – bevel, etc.).
The addition or deletion of a backing.
A change in the nominal composition of the backing. Page 15 of 29
The deletion of the backing in single – welded groove
welds. Double – welded groove welds are considered
welding with backing.
The addition of a backing or a change in its nominal
composition.
An increase in the fit – up gap, beyond that initially
qualified.
The addition backing.
A change in nominal size or shape of the stud at the
section to be welded.
In stud welding, a change in shielding as a result of
ferrule or flux type.
A change in the specified root spacing.
The addition or deletion of nonmetallic retainers or
nonfusing metal retainers.
The welding procedure qualification test shall duplicate
the joint configuration to be used in production within Page 16 of 29
the limits listed, except that pipe or tube to or tube may
be used for qualification of a pipe or tube to other
shapes, and solid round to solid round may be used for
qualification of a solid round to other shapes:
a) Any change exceeding +/- 10 degree. In the angle
measured for the plane of either face to be joined, to
the axis of rotation;
b) Change in cross – section area of the weld joint
greater than 10%.
c) Change in the outside diameter of the cylindrical
weld interface of the assembly greater than +/-10%;
d) Change from solid to tubular cross – section at the
joint or vice versa regardless of (b) above.
A change in the joint from spot to projection to seam or
vice versa.
A decrease in the center – to – center distance when the
welds overlap. An increase or decrease of more than 10%
in the spacing of the welds when they are within two
diameters of each other.
Page 17 of 29
A change in the size or shape of the projection in projection
welding.
A decrease in the distance between the weld fusion line and
the final surface of the production corrosion – resistance or
hard – facing weld metal overlay below the minimum
thickness qualified as shown in QW – 462.5. There is no
limit on the maximum thickness for corrosion – resistance
or hard – facing weld metal overlay that may be used in
production.
An increase in the thickness of the production spray fuse
hard – facing deposit above the thickness deposit on the
procedure qualification test coupon.
5.3 BASE METAL (QW – 403): -
QW – 403 states the requirements of the base metals that
constitute the weldment.
A change from a base metal listed under one P – number in
QW – 422 to a metal listed under another P – Number or to
any other base metal. When joints are made between two
base metals that have different P – Numbers, a procedure
qualification shall be made for the applicable combination
of P – Numbers, even though qualification tests have been
made for each of the two base metals welded to itself. Page 18 of 29
The maximum thickness qualified is the thickness of the
test coupon.
Where the measurement of penetration can be made by
visual or mechanical means, re – qualification is required
where the base metal thickness differs by 20% from that of
the test coupon thickness when the test coupon thickness is
1 in. and under, and 10% when the test coupon thickness is
over 1 in. Where the measurement of penetration can’t be
made, re – qualification is required where the base metal
thickness differ by 10% from that of the test coupon when
the test coupon thickness is 1 in. and under, and 5% when
the test coupon thickness is over 1 in.
Welding procedure qualification shall be made using a base
metal of the same type or grade or another base metal listed
in the same group (See QW – 422) as the base metal to be
used in production welding. When joints are to be made
between base metals from two different groups, a
procedure qualification must be made for the applicable
combination of base metals, even though procedure
qualification tests have been made for each of the two base
metals welded to itself.
Page 19 of 29
Welding procedure qualification shall be made using a base
metal of the same type or grade or another base metal listed
in the same group (See QW – 422) as the base metal to be
used in production welding. When joints are to be made
between base metals from two different groups, a
procedure qualification must be made for the applicable
combination of base metals, even though procedure
qualification tests have been made for each of the two base
metals welded to itself.
Welding procedure qualification shall be made using a base
metal of the same type or grade or another base metal listed
in the same P – Number and Group – number (See QW –
422) as the base metal to be used in production welding. A
procedure qualification shall be made for each P – Number
and Group – Number combination of base metals, even
though procedure qualification tests have been made for
each of the two base metals welded to itself. If, however,
the procedure specification for welding the combination of
base metals specifies the same essential variables,
including electrode or filler metal, as both specifications
for welding each base metal to itself, such that base metals
is the only change, then the procedure specification for
welding the combination of base metals is also qualified. In
addition, when base metal s of two different P – Number
and Group Number combinations are qualified using a Page 20 of 29
single test coupon, that coupon qualifies the welding of
those two P – Number to themselves as well as to each
other using the variables qualified. This variable does not
apply when impact testing of the heat-affected zone is not
required by other section.
NOTE: - QW – 422 lists the P – Numbers and S – Numbers
of ferrous and non-ferrous base metals for qualification.
The minimum base metal thickness qualified is the
thickness of the test coupon T or 5/8 in., whichever is less.
However, where T is less than ¼ in., the minimum
thickness qualified is ½ T. this limitation does not apply
when a WPS is qualified with a PWHT above the upper
transformation temperature or when an austenitic material
is solution annealed after welding.
For the multipasss processes of shielded metal – arc,
submerged – arc, gas tungsten – arc, and gas metal – arc,
the maximum thickness qualified for 11/2 in. and over
thickness T of the test coupon of QW – 451.1 shall be 8 in.
for the conditions shown in QW – 451.1. For thickness
greater than 8 in. the procedure test coupon thickness of the
joint to be welded in production divided by 1.33 and the
maximum thickness of base metal and deposited weld
metal qualified is 1.33T or 1.33t, as applicable. Page 21 of 29
NOTE: - QW – 451 specifies the procedure qualification
thickness limits and test specimens.
A change in base metal thickness beyond the range
qualified by QW – 451, except as otherwise permitted by
QW - 202.4 (b).
5.4 POSITIONS (QW – 405 ): -
QW – 405 enumerates the requirements in the positions used
during welding joints.
Qualification in horizontal, vertical or overhead position
shall also qualify for flat position.
Qualification in horizontal fixed position, 5G shall qualify
for flat, vertical and overhead position.
Qualification in inclined fixed position 6G shall qualify for
all position.
The angular deviations permitted in the inclination of weld
axis and rotation of weld face are as defined in QW – 461.1.
Page 22 of 29
A test specimen shall be taken from the test coupon for
qualification in each special orientation.
A change in progression of travel from uphill to downhill, or
vice versa in vertical position requires no re- qualification.
The various positions put to use during welding are as shown
below.
5.5 PREHEAT (QW – 406): -
It describes the preheat requirements.
Minimum temperature for preheat shall be specified in the
WPS.
The minimum temperature for welding shall also be
specified in the WPS.
An increase of more than 100 F in maximum interpass
temperature recorded on PQR requires requalification. This
need not be true in case of PWHT above the upper
transformation temperature or when as austenitic material is
solution annealed after welding. Page 23 of 29
5.6 POSTWELD HEAT TREATMENT (QW – 407):
It states about the requirements of post weld heat treatment.
For P – No. 1, P – No. 4, P – No. 5, P – No. 6, P – No. 9, P
– No. 10, and P – No. 11 materials, the following post weld
heat treatment conditions apply:
a) No PWHT.
b) PWHT below the lower transformation temperature.
c) PWHT above the upper transformation temperature
e.g. normalizing.
d) PWHT above upper transformation followed by heat
treatment below the lower transformation temperature
e.g. quenching followed by tempering.
e) PWHT between the upper and lower transformation
temperature.
For all other materials, the following PWHT conditions
apply:
a) No PWHT.
b) PWHT within a specified temperature range.
A change in PWHT conditions requires a new PQR to be
raised. Page 24 of 29
The procedure qualification test shall be done in accordance
with the post weld heat treatment conditions encountered in
the fabrication of production weld.
For a change of more than 10% in number of post heating
cycles following the welding intervals a new PQR has to be
raised.
A new PQR has to be raised if heat treatment is performed
separately from the welding operation.
A change in post weld heat condition of 25% in the total
time at post weld heat treating temperature requires a new
PQR to be made.
5.7 GAS (QW – 408): -
QW – 408 states the requirements of the gases
(trailing, backing, shielding) used in the welding the
joints.
A separate PQR is required for each of the following
condition: -
a) A change from one shielding gas to another.
b) A change from single shielding gas to a mixture of
gases.
c) A change in percentage composition of the mixture of
shielding gas.
d) The addition or omission of shielding gas. Page 25 of 29
A change in oxygen or fuel gas pressure beyond the range
qualified requires requalification.
A change of more than 5% in the flow rate of the plasma –
arc gas or powdered gas or powdered metal feed gas
recorded on the PQR requires a new PQR.
A change in nominal composition of the powdered feed gas
or (plasma – arc spray) plasma gas qualified requires
requalification.
5.8 ELECTRICAL CHARACTERISTICS (QW – 409): -
QW – 409 states the requirements of the various electrical
parameters used in welding.
A change in the polarity i.e. EN to EP and vice versa, in
DC welding or from AC to DC; requires a change in PQR.
An increase in heat input or an increase in volume of weld
metal deposited per unit length of weld, over that qualified
requires requalification. This is not required when the WPS
is qualified with a PWHT above the upper transformation
temperature or a solution annealed after welding austenitic
materials.
Page 26 of 29
A change in the power source model requires no separate
PQRs provided the parameter used remain the same.
A change of more than 5% in the electrode pressure, the
welding current, or the welding time from that qualified
requires requalification, except that requalification is not
required if there is a change of not more than 10% in either
the electrode pressure or the welding time cycle, provided
the remaining two variables remain at the values qualified.
A change in beam current of more than 5%, voltage of
more than +/-2%, gun – to – work distance of more than
+/-5%, or a change in oscillation length or width of more
than +/-20% from those qualified requires requalification.
A change of more than 10% in the range of amperage or
voltage qualified requires requalification.
5.9 TECHNIQUE (QW – 410): -
QW – 410 states the technique to be used during welding.
A change from multipass per side to single pass per side
requires requalification. This limitation does not apply when
a WPS is qualified with a PWHT above upper transformation Page 27 of 29
or when an austenitic material is solution annealed after
welding.
Requalification is required for a change from single
electrode to multiple electrodes, or vice versa, for machine or
automatic welding only. This limitation does not apply when
a WPS is qualified with a PWHT above the upper
transformation temperature or when an austenitic material is
solution annealed after welding.
Addition or deletion of peening requires requalification.
A change from manual to automatic and vice versa raises a
need for requalification.
When there is addition or deletion of an electrode-cooling
medium a new PQR must be raised.
A change of more than 15% in the travel speed range
recorded on the PQR require requalification.
A change of more than 15% in spray – torch to workpiece
distance qualified requires a new PQR.
A change of more than 10% in oscillation motion as
recorded on the PQR requires a new PQR. Page 28 of 29
Page 29 of 29