Steps of Making WPS

8/4/2019 Steps of Making WPS

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The Welding Procedure and its Qualification


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I. Welding procedure specificationsA. Is to define and document the details that are to be carriedout in welding specific materials

B. Contentssufficiently, detailed to ensure that the welding will meet allrequirements of the applicable code, standard, C. Base Metals and applicable specifications 1- Give the chemical composition. 2- Indicate condition of base metal before welding

(Normalized, annealed, quenched and tempered, solution treated) .

3.The fabricator must know the identity of all materials

Full plates or sections can beID

by the mill numbers.

small portions cut from plates marked with the samenumbers.The rolling direction of plate should be identify.


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D. Welding process (partial listing)1. Oxyacetylene OAW

2. Brazing3. SMAW 4. GMAW

5. FCAW 6.GTAW 7. SAW 8. ESW 9. SWE. Type, classification, composition of filler metal

1. Composition, classification designation of the filler metal must beincluded 2. Also included in specifications

a. Size of electrode or filler metal For

varying ( positions, metal thickness)

b. Storage requirements Low hydrogen electrodes require a dry(120oC)


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F. Type of current and current rangAC or DC (DCRP or DCSP). Current range should be listed for each of the welding

variables (position, thickness, electrode size).G. Welder qualification requirements welding operator qualification.Make reference to applicable welder qualification specifications

H. Joint designs and tolerances.Indicate joint design details as well as welding sequence.Use crops sectional sketches that show the thickness ofmaterial and details. of the joint or refer to standard drawingsor specifications.Give tolerances for all dimensions.Joint preparation and cleaning of surfaces for welding(Before or after welding or cutting ).Joint welding details, give details for (i.e. amps, electrodesize, sequence of passes, weave limitations, etc.).


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I. Preheat and inter pass temperaturesmeasured by touching the work piece close to the weld jointwith .

J. PeeningIf peening is to be used, give details of its applicationAnd verify the results during qualification test welding Peening the middle layer of a weld distributes and balancesdistortion.

K. Heat inputheat-treated alloy steels, must not heat above the finaltempering temperature used by the steel mill.Specify the preheat and inter pass temperature rangemaximum.. Arc voltage range maximum.. Welding current range maximum.. Travel speed minimum.


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L. Root preparation prior to welding from second side

Describe how (Chipping, grinding, air carbon arc gouging,oxyacetylene gouging, or whatever).

M. Removal of weld section for repairMay be the same procedure used for preparing the root from

the second side .

N. Repair Welding

Give details of any repair welding methods andprocedures .

O. Examination

Type of examination for each joint will receive (i.e.

radiography, magnetic particle, etc.).Visual inspection of every weld is routinely required .


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P. Post heat treatment

Give a full description or reference drawing, or document.

heat-treated alloy steels should not exceed the final

tempering temp that was given the base metal.If a full reheat treatment is intended, do the weldingwith the metal in the annealed condition.

Q. Marking

Require that welder identification marks be made on or neareach weld.

. Maintaining a record of welds made by the welders.

I.D. marking made with low stress steel die stamps.

R. Records

Indicate detailed records of the welding joints.


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II. Welding procedure qualification

A. There are four steps in the qualification of awelding procedure (all or none).

1. Preparation and welding of suitable samples.

2. Testing of representative specimens.3. Evaluation of overall preparation, welding, testing,

and end results.

4. Approval (if the results are favorable).B. Preparation of Procedure Qualification sample joints

1.The size, type, and thickness are related to the type andthickness of material to be welded in production and thenumber, type and size of specimens to be removed for testing.


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C. Testing of procedure qualification welds1.The type and number of specimens to be removedfor destructive tests will depend upon the

requirements specification (. Usually include tensilestrength , ductility, soundness, and NDT).2 Be sure that your records show how the

procedure qualification test welds were made andtested.D. Evaluation of test results

1. These results will be analyzed by the responsibleparties to determine whether the test details andresults meet the requirements specifications.


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E. Approval of qualification tests andprocedure specifications

1. Qualification is accomplished when the required tests havebeen completed and approval has been obtained.

2. Documentary evidence must be available to show that the

results were indeed satisfactory.

3 .You should witness the welding and testing of allspecimens; because you will gain knowledge will help in

inspection..


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III. Code qualification requirementsA. AWS structural welding code D1.1

1. Paragraph 5.5 sets forth the requirements for qualifying

those welding procedures, which do not meet the pre-qualifiedstatus of paragraph 5.1 of that code2. The type and number of specimens that must be tested toquality a welding procedure are given in paragraph 5.10

a test results required are in 5.12 B. ASME boiler and pressure vessel code1. Section IX is the basic document Welding and brazingqualifications

2. All sections of the ASME code required welding procedures

to be qualifiedin accordance with section IX

3. Section III on nuclear components for powerplantsSection VIII division I on pressure vessels


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IV. Changes in a qualified procedureRe-qualification is necessary when any one of

the essential variables listed in thegoverning standard or code is changedV. Welding inspector responsibilitieA. Welding procedure qualification

1. It is your duty to verify that welding procedureshave been established they will2-You should witness the welding and testing of thequalification weld specimens

3-You must have available authentic documentaryevidence that joints were satisfactory


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B. Welding Inspection1. Passing of a qualification test does not ensure proper application of theprocedure.2. Verify how the qualified procedure is being applied.

3.Checklist for Yourself for each procedure specification to guide you .4. It is your duty to obtain a good job, properly fabricated

a-not to impose your preferences on the fabricator. Until yourexperience as an inspector covers many shops.

b. Inspect as promptly and quickly as possible.

c. Interfere as little as possible with production.5. Make sure that weldments needing repair are correctly and adequatelymarked.

a.Everyone should have a clear understanding about the markingsystem you will use to indicate any repairs.

b-You must approve the repair procedure and inspect the repaired

weld.


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d. Joint fit-up1. Edge preparation (including root face and beveling)2. Dimensions 3. Cleanliness4. Root opening 5. Tacking

6. Backing (where required)C. Special setups used for assembly and fabrication (to seethat uniform practices are used)1. Jigging and bracing2. Pre-stressing or pre-cambering

2. Inspection during weldinga. Preheat and interpass temperature b. Root passc. Root preparation prior to welding second sided. Cleaning between passes e. Appearance of passes (sometimes

in comparison with workmanship standard)f.Variations from approved welding procedure (materials, electrodes,

currents, etc.)


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3. Inspection after weldinga. Post heat treatment b. Surface finishing of welds4. Preparation of inspection reports and related

correspondenceE. Acceptance inspection1. Method of cleaning for inspection2. Nondestructive testinga. Visual inspection

b. Surface appearance of weldsc. Conformity of welds with drawingsd. Liquid penetrate testse. Magnetic particle tests

f. Radiographyg. Ultrasonic testsh. Proof testingi. Other suitable methods


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3. Destructive testing

a. Chemical

b. Mechanical

c. Metallographic

4. Repairs

a. Marking for acceptance or refection

b. Inspection of preparations for repair

c. Inspection after repair

5. Inspection of loading prior to shipment

6. Preparation of inspection reports and relatedcorrespondence


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How to formulate a welding procedure - a guide tobest practice

Requirements, considerations & essential steps tosuccess

Introduction this guide is based around carbon steels, much of the information

it contains can be related to other materials,. many welding procedures fail to meet their objectives due to

communication problems. Welders, inspectors and supervisors needprocedures, which give essential information clearly and in enough

detail The layout of a welding procedure can be just as important as thecontent itself: information should be presented in a manner, which

is visually clear and easy to follow.

make sure that you either use the latest revision of a Code orStandard, or, what the contract specifies regarding weldingprocedures.


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Step1Establish the class of work

WP can be applied to a variety of different products. Eachproduct have different requirement from qualityfor example, a garden gate. not required wps

Conversely, if a product is regarded as 'safety critical', thewelding procedure (or procedures) will have to contain moreinformation and require approval testing to ensure that it will

work in practice and that certain mechanical, metallurgical andphysical properties can be achieved.

many of the details will be established at the design stage inconjunction with company quality assurance/quality controlrequirements.

It is also essential to establish. technical details ofproduction: for example, facilities available, i.e. weldingequipment (power sources, manipulators or positioners)

because have an influence on the WP requirements.

Step 2


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Step 2Determine if the product is to be manufactured to a

Code of PracticeIn general terms, the code will include:

1- Design requirements. 2- Materials for construction3- Workmanship requirements. 4-Inspection and Testing5- Acceptance levelsTypical codes of practice, which could be specified,

are:

BS5500 : Unfired fusion welded pressure vesselsASMEVIII: American boiler and pressure vessel codeBS 2633 :Class 1 arc welding of pipe for carrying fluidsBS4515: Process of welding steel pipelines on land and

offshoreAWS D1.1 : Structural welding codecodes of practice very different requirements for welding procedures.For example, BS5500 specifies that WP must be in accordance withBSEN 288. This compares with AWS D1.1, which allows the use of

'standard WP'.details are established before proceeding: failure to recognize specific


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Step 3Establish customer or contract requirementsDetails stipulated within contracts are varied. It is difficult to

be specific about details of this nature but for guidance thefollowing examples are provided -

Example AIn BSEN 288 Part 3, details the requirements for wpapprovals, for all positional approval that a pipe test piece will

be required to be welded (pipe axis at 45 degrees during thetest).Welders find this welding position easier compared with atest with the pipe in the fixed pipe axis horizontal and fixedpipe axis vertical.,

therefore, important to first satisfy the welding procedurerequirements, rather than the welder approval.It may be the customer would insist on two test pieces foreach welding procedure approval and this will obviouslyincrease costs.


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Example B

As mentioned in Step 2, BS5500 specifies that weldingprocedures are required to be approved to BSEN288. The

code of practice also insists on further requirements inaddition to BSEN288, including the need for furthermechanical testing. For this reason it is essential that as manyfacts relating to specific contractual and code requirements

are established beforehand to minimize future problems.


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Step 4

Rationalize approval testing of the welding)procedure(s

Because many welding procedures are required toundergo approval testing, it is important that the weldingprocedure meets the standard specified.

It is also possible in many instances, to approve weldingprocedures to different standards simultaneously, e.g. toBSEN288 and ASME IX. It should, however, berecognized that both standards must be met in relation totechnical requirements.

The project leader should investigate the possibility ofjoint approval as this approach could satisfy furtherprojects and save costs associated with future approvals.


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Step 6

Investigate range of approvalThe term 'range of approval' initially relates to the production

details of the project or product.Production details often relate to the following items:

Welding process to be used .

Material types used in the project .

Different thickness of material used. Pipe or plate applications (or both) .

Weld joint type .

Welding positions encountered .

For the above items, wp (and welder approval) standardsoften provide a working tolerance for each individualfactor in production. These are known as the range of

approval,


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for example:A fabrication of high strength steel, using the MMAW process,in a thickness range of (5 - 25mm). The fabrication requires

use of pipe in a range of diameters from (100 to 300mm), andplate materials. The welding will involve

all welding positions except vertical down, and the joint typesare butt joints made from one or two sides, and fillet weldedjoints.

To prepare WP for each detail,, would be extremely time-consuming and costly.

Therefore, approval standards often apply a range of toapproval ,increase the working range of individual welding

procedures.For the above example fabrication, the following is providedas general guidance (for approval, details must be obtained byreferring to the appropriate standard or standards):


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Welding processThe welding process plays a major role in the quality and

performance of the welded joint,

MaterialBecause the material is a high strength steel, the range ofapproval could include all materials with similar weldability

and/or mechanical properties. So, it may be that one materialwill approve the other types used.

Thickness of componentsThe range of approval may be from half to twice the mean

thickness. 0.5 - 2t., if a joint was 10mm, the range of approvalwill be from 5 to 20mm.

For pipes, the diameter will be based on half to twice thediameter. If a pipe in 200mm diameter will satisfy diameters

ranging from 100 to 300mm. also approve plate weldsJoint type

joint welded from one side is much more difficult than a jointwelded from both sides, This single-sided joint, welded from

one side, will therefore approve most other


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Step 7Consider essential variables

varies from code to code (or standard to standard). However,

the definition largely has the same implication.In BSEN 288, the term is defined as 'a variable which willinfluence or change the mechanical or metallurgical

properties of the welded joint'. Other codes/standards usethe definition 'changes that affect approval'.

Essential variables may include: Material grade or group (material thickness range, form

(pipe or plate), joint type ,details ). Welding process (AC, DC), polarity,A, V, speed, number

of weld runs and sequence.

Consumable details (manufacturer's name, size, shieldinggases, flow rates).Other essential variables are based around these three

essential variables.


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Step 8Select the method of approval

involves welding test pieces, which to production requirements.correct method is established before proper formulation of the

welding procedure is carried out this may have an impact on mostof the previous steps. BSEN 288 Part 3 to Part 8

Step 9Formulate the welding procedure

the most difficult task. depend on the outcome of each of the previous

eight steps. Unless you are a welding expert you will probablyhave to involve expertise from other sources which may include: A qualified welding consultant Use of reference books from welding consumable or welding

equipment manufacturers Dedicated welding procedure information Codes and standards Pre-approved weld procedures Historical records of previously approved welding procedures


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Example one-a general purpose fabrication

the contract requires only the welders to be approved to BS4872 PartOne: 'Approval Testing of Welders when Welding Procedure Approval isnot Required'.Assumptions for this example

Material type: Low carbon steel

Material thickness: 10mm

Material form: Plate

Welding process: Manual metal arcConsumable details: to be confirmed by consumable manufacturer

Current type: Alternating current

Welding position: Vertical up

Joint type: Fillet weld onlyWithin the standard there is not a requirement for amperage, voltage ortravel speed. Nor is there a requirement for preheat or post weld heattreatment, or specific techniques regarding the number of weld passes orsequence of weld passes.


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Example two - a safety-critical piping systemThe relevant code of practice in this example is BS2633 'Class 1 arc

welding of pipe for carrying fluids'.The following provides an example of how a welding procedure would

be formulated.Assessment of materials

Mechanical/physical properties of the parent material (strength,toughness, hardness, corrosion resistance, weldability)

Chemical analysis of the material - percentages of carbon,

manganese, etc for ferritic steels and in addition chromium,nickel, molybdenum, etc for stainless steels. This may beestablished from the materials certification provided by thematerials supplier or manufacturer and should relate to thematerials used for testing or fabrication

Material thickness, length, width, diameter for pipes, etc Joint design, butt joints, fillet welded joints, etc

economics is also necessary so effective production methodscan be decided. This will require appropriate joint details angle,root gap and root face. edge preparation tolerances .


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Assessment of weldabilitythe carbon equivalent value (CEV) in this case is 0.48% which

means that the material could be susceptible to hydrogen inducedcold cracking (H.I.C.C.). Appropriate precautions must be taken

which may include requirements for preheat/heat input control andpost weld heat treatment (PWHT).Preheat & weld hydrogen

The amount of preheat required is based on other factors such asthe expected hydrogen level of the welding process. the objective is

to bring the hydrogen potential down as low as possible.based on the weld metal having less than 15ml of hydrogen in 100g

of weld metal.Selection of consumables

Because the material is regarded as 'crack sensitive' it is importantto select a welding consumable which exhibits low hydrogen

potential. the consumable type is dependent on the process choice., some arc welding processes having a low hydrogen potential, e.g.TIG and MIG. But flux-based processes, such as (MMA) and (SAW),

require correct selection of the consumable flux and appropriatecontrols to ensure hydrogen is at an acceptable level.


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Size of consumableIn order to establish the correct consumable size, several points mustbe taken into consideration : Productivity requirements. Welding positions encountered . Joint designs encountered . Welder competence . Acceptance levels or quality requirementsa small diameter electrode will be preferred so that the welder has

greater control over the weld pool. For all welding positiona 2.5mm diameter electrode could be used for the root pass and

a 3.25mm could be used for the fill and capping passes.If the material was relatively thin (less than 8 - 10mm), it may

be necessary to use a 2.5mm electrode throughout.

It may also be necessary to contemplate using TIG welding forthe root pass and completing the remainder of the weld with MMA,If TIG was chosen, a suitable shielding gas and filler wire size andtype will also need to be included in the welding procedure, alongwith other details that relate to the TIG process. .


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Welding parametersThe main welding parameters associated with arc weldingprocesses are: Amperage ( 1 mm = 40 amps ) in MMA

Voltage Travel speed

the final run to be made with a 2.5mm diameter electrode to avoidproblems with undercut at the weld toe.In the MMA, arc voltages are dependent on the consumables being

used. For MMA with a basic electrode, 20 to 24V. For rutile coverings,

18 - 22V, and for cellulosic coverings, typically 28 - 32V.For TIG welding using argon, arc voltage will typically be 10 - 12V.

Arc voltage is much more difficult to establish when specifyingcontinuous wire-fed processes such as MIG/MAG or SAW.The consumable manufacturer information may be available from

the shop floor.the travel speed is left to the welder's experience.

Inter pass temperature & post-weld heat treatment controlFor some types of material, the inter pass temperature and post-weld heat

treatment must be specified in order to achieve certain weldmentproperties. temperature measurement, heating/cooling rates,


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Requirements for specific processes

Different welding processes require certain additional featuresto be specified. Reference to BSEN288 Part 2 will provide

specific details for each welding process.TIG welding, for example, it will be necessary to specify thetungsten electrode designation and diameter. In addition, thenozzle diameter and gas flow rate are also required. For otherwelding processes,

Step 10

Evaluate information gatheredThe information which has been acquired for (pWPS) shouldbe evaluated before any approval test is carried out. by thesame welders who will be carrying out the approval testing

become familiar with the WPS and provides feedback tovalidate recorded information


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Step 11

Approve the welding procedure

A suitably competent person should carry out approval of thewelding procedure (and welder). It may also be necessary tohave the test witnessed by a third party inspectorate, such asan insurance company representative. In addition, subsequent

visual inspection, non-destructive testing and destructive

testing will require, in most cases, personnel to have(CertificationCSWIPappropriate qualifications such as

Scheme for Welding and Inspection Personnel),

To reduce costs, it is possible to carry out multi-standard

approval from one test. approval to BSEN, ASME

Step 12
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Step 12

Establish documentation requirementsFor many people, this is the most important part of the process of

formulating and approving welding procedures.

Definitions to BSEN288/287

Pwps - Preliminary Welding Procedure SpecificationWPS - Welding Procedure Specification (welders, inspectors, supervisors, etc).WPAR- Welding Procedure Approval Record (by the company's quality control

department )WATR- Welder Approval Test Record

All of the above records - which will in addition include inspectionreports, NDT reports and destructive testing reports - are kept aspart of a quality control system.

It will also be necessary for a responsible person to sign off thewelder approval test records/certificates on a regular basis -otherwise the approval may lose validity and re-approval ofwelders may be required.


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Step 13

Monitor production welds

. It is important to ensure that the correct welding procedures

are available for specific production welding details and thatappropriately qualified personnel monitor the welding.

Step 14

Consider cost implications

The costs involved with successfully addressing all the issues,implications and requirements connected with each of theprevious 13 steps could range from a few hundred pounds fora relatively simple welding procedure to many thousands ofpounds for a large number of approved welding procedures.

and thequalificationsplus appropriatetrainingHigh qualityright practical experience are essential for successful

formulation of welding procedures.

Q S O S
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QUESTIONS

TO START ??


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What is "to manage welding procedure"? Explain it concretelyaccording to the four-step circle method of 'Doming Circle'PDCA proposed by W. E. Deming to explain statisticalquality control activities.

(Answer)

P : Planning the welding procedure specifications

D : Preparation and manage of welding procedure followingthe welding plan

C : Check and evaluation of welding procedure

A : Go / Stop or correction of the welding procedure by checkstep's evaluation


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Mention three items composing welding quality managementactivities (comprehensive quality management).

(Answer)

Three major factors that constitute quality managementactivities are

1) Quality assurance

2) Quality control (quality control in the narrow sense

such as SQC statistic quality control)

3) Quality improvement


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The tasks and responsibilities required for the Welding Coordination arespecified in ISO14731. What activities are specified in this standard forWelding Engineer(s)? Give five items.

(Answer)Select five items among the followings :

(1) Contact review(2) Design review(3) Materials and Weldability (Traceability)(4) Welding consumables (Suitability, Requirements)

(5) Subcontractor (Profitability)(6) Fabrication plan(7) Equipments and facilities(8) Preparation works(9) Welding procedures

(10) Measuring and visual examination(11) Destructive and Non-destructive testing(12) Acceptance of welds (Repair)(13) Documentation (including document control)


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Part 2 to 4 of ISO 3834 corresponds to ISO 14731"Welding coordination - Tasks and responsibilities"and relates to ISO 9000s series standards- Mentionconcisely the title and contents of the ISO 3834

standard.

(Answer)

1) The title of the standard : Quality requirements for welding -Fusion welding of metallic materials

2) Outlines of the standard : This standard consists of Part 2through Part 4 corresponding to ISO 9001 through 9003. Theseare "Comprehensive quality requirements", "Standard

quality requirements", "Elementary quality requirements"respectively, in which welding-related quality requirementsregarding various activities from contract, delivery, throughafter-sale service are covered.


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In order to assure welding quality, it is important toestablish WPS (Welding Procedure Specification). To makeWPS, to conduct welding and related jobs in accordancewith WPS and to maintain WPS shall be a responsibility of

Welding Engineer. What items shall be given and specifiedin WPS. Give at least five items.(Answer)

Select five items among the followings:(1) Classification of base material

(2) Classification and size of welding consumables(3) Welding process(4) Preheating and interpass temperature(5) Groove geometry and tolerance(6) Polarity, Number of electrodes and flow rate of shielding gas

(7) Number of layer and deposition sequences(8) Welding position(9) Welding parameters(10) Qualification of welder(11) PWHT and its conditions


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Answer the following questions regarding to the fabrication by welding inaccordance with the ASME Code. Choose and mark the correct one among five.Then, put the related chapter number of ASME Code in [ ].Example : [ UW-12-c ]

(1) When spot radiographic examination is adopted, one spot shall be examined in

the first (a.3m, b. 6m, c. 10m, d. I2m, e. 15m) of welding in each vessel. [ ]

(2) According to the Standard for Spot Radiographic Examination, welds in whichthe radiographs show slag inclusions or cavities shall be unacceptable if the lengthof any such imperfection is greater than ( a. 1/4 T, b. 1/3 T, c. 1/2 T, d. 2/3 T, e.3/4 t), where t is the thickness of the thinner plate welded. [ ]

(3) In case of performing PWFT, heating the vessel in more than one heat in afurnace, provided the overlap of the heated sections of the vessel is at least ( a.0.3 m, b. 1.0 m, c.1.5m, d.2.0m, e.3.0m). [ ]

(4) Each welder and welding operator shall stamp the identifying number, letter or

symbol at interval of not more than ( a. 0.3 m, b. 1.0 m, c. 1.5 m, d. 2.0 m, e. 5 m) along the welds which he makes in steel plates 6 mm and over in thickness. []

(5) The surface of the part to be welded shall be clean and free of scale, rust, oil,grease and other deleterious foreign materials for a distance of at least ( a. 13 mm,b. 26 mm, c. 51 mm, d. 76 mm, e. 100 mm ) of welding in each vessel. (]


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(Answer)

(1)e. 15 (UW-52-b]

(2)d.2/3T (UW-52-c(2) ]

(3) c. 1.5m [UW-40-a(2)3

(4)b. 1.0m [UW-37-f(l)]

(5) a. 13 mm [ UW-32 ] Note : No prescription inASME-2000


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The following sentences are relating to the fabrication bywelding in ASME Code Sec. VIII,Div.l. Choose the correct number in the parenthesis and mark

0 its letter. Further put thenumber or letter of the chapter and section which is specifiedin the Code.(Example [UW-31-a]).(1) When spot radiographic examination is carried out, the

sampling rate is one shot per every(a. 10, b.20, c.30, d. 40, e. 50 ) feet of weld length. [ ]

(2) The maximum allowable reinforcement height ofcircumferential welding joint whosethickness is 26mm, is ( a. 3S2, b. 1/8, c. 3/16, d. 1/4, e. 5/16)inch, [ ]

(3) In the butt welded joint of Category "B" of 2 inches plate

thickness, the maximum allowable "misalignment", that is"offset", is ( a. 1/4, b.1/8, c. 3/16, d. 1/16, e. 3/4 ) inch. [

(4) I i d d h l f l


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(4) It is recommended that at low temperature, for example at20 F, the surface of all areas

within 3 inches of the point where a weld is to be startedshould be heated to a temperature atleast (a. 36, b. 50, c. 60, d. 70, e. 80 ) F before welding isstarted. [(5) Each welder and welding operator shall stamp theidentifying number, letter or symbol

assigned the Manufacturer, on or adjacent to and at intervalsof not more than ( a. 1, b- 3,c. 5, d. 7, e. 10 ) feet or lessalong the welds which he makes in steel plates 25 mm inthickness.

(Answer)

(1)e.50 [UW52-b](2)d.l/4 [UW-35-d](3) a. I/4 [UW-38-a]

(4) c. 60 [ UW-30 ]

P h ti i ti i d ldi


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Preheating is sometimes required on weldingprocedure. Describe the objectives at least 3items and their detail explanations on each.

(Answer)(1) Prevent of cold cracks in the weld metal and HAZ(2) Improvement of the ductility and notch toughness of weldmetal and HAZ(3) To avoid lack of fusion and poor penetration at weld root

pass in welding heavy plate or in welding metals having higherthermal conductivity1. Preheating effects welding cooling rate down, so that itinduces to make softened HAZ and weld metal.2. The above slower welding cooling rate will reduce the

diffusible hydrogen content in weld metal.The above 1. and 2. effect will be avoid probable welding coldcracking.Softened HAZ and weld metal due to preheating may improvetheir notch toughness and ductility,

E l i th fi it f i t t ti th d i d


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Explain the five items of important cautions on the design andprocedure to prevent brittle fracture of welded structures

(Answer)Give five items out of the followings:(1) Use of the material with excellent toughness. Select the material

with sufficient notch toughness, paying due to attention to the servicetemperature, service conditions, etc.(2) Use of the material with better weldability. Select the material thathas excellent weldability.Excellent performance of the weld and little possibility of weld defectsare required in a weld structure.

(3) The design shall be such as to avoid the stress concentration. Thedesign shall be such as to avoid the stress concentration due to theshape of the structural elements (open holes, comers. etc.) as well asthe configurationally discontinuity and concentration of weld lines.(4) Elimination and control of welding defects (imperfections) .Eliminate the welding defects by adopting the non-destructive test, and

control under the distinct assumption as to what percent of weldingdefects still remain-(5) Establishment and control of welding condition.(6) Reduction of welding deformation by taking particular care toreduce angular distortion, off-set of

butt welding, etc.7 Relieve the residual stress de endin on necessit .


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Steps of Making WPS