Asme Sec Ix - Short Notes

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.

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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.

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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.

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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.

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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.

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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.

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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.

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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

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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

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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.

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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.

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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.

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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.

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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

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