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Wps report
Wps report
Wps report
Wps report
Wps report
Wps report
Wps report
Wps report
Wps report
Wps report
Wps report
Wps report
Wps report
Wps report
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Wps report

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  • can u include file regarding what to study for field inspection for cwsip 3.1 welding inspector
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  • 1. 1.0 INTRODUCTION There are numerous welding process variables that should be described in a weldingprocedure. It is always desirable and often essential that the variables associated with thewelding be described in a welding procedure with sufficient detail to permit reproduction ofthe weld and to afford a clear understanding of the parameters for performing the productionweld. These variables are stipulated in two different documents: 1. Welding procedure specification (WPS) 2. Procedure qualification record (PQR)1.1 Welding procedure specification (WPS) Welding procedure specification is a document that describes how welding is to becarried out in production. They are recommended for all welding operations and manyapplication codes and standards make them mandatory. The WPS document providing therequired welding variables for a specific application to assure repeatability by properlytrained welders and welding operators. Generally, proposed welding procedures should beproven adequate by either procedure qualification tests or by sufficient prior use and serviceexperience to assure dependability. The purpose of a welding procedure specification is todefine those details that are to be carried out in welding specific materials or parts. To fulfillthis purpose effectively, a welding procedure specification should be as concise and clear aspossible or in other words it is a recipe of the welding.1.2 Procedure qualification record (PQR) Every welding to be carried out needs a report which detailed welding method, typeof material and welding material is in compliance according to standards and which itswelding is performed in compliance with ASME or other organization codes according toproject standards. The PQR should have several mechanical tests such as non-destructive testand destructive test which provide the result of the testing. All the test also required theendorsement from third party inspection bodies. The mechanical tests are conducted and its 1
  • 2. results are in compliance. Therefore, every WPS must require a supporting weldingprocedure qualification record (PQR). The PQR can support several WPS under validity areas. The PQR preparation andtests must be conducted and approved under supervision of Third Party Inspection Bodiessuch as Lloyd consultation and PQR must be in compliance with standard of the job carriedout. For jobs apart from ASME Code, related standard must be taken as a basis. The weldingterminology that will be used must be appropriate to manufacturing standard.1.3 Welder Qualification Record In the welded manufactures, welding must be performed by a welder who hasabsolutely this qualification. For certification of this, welders will be tested according toASME SEC. IX or other standard codes in compliance with project standard and will have acertificate and badge that covers the welding specifications. Tests of welders must beconducted under supervision of Independent Inspection Bodies, and then certificates must begiven by these bodies. Welders who do not have such a certificate or whose certificate isexpired, then before the project, they must be re-taken to test in supervision of authorizedinspection company. Badges that is submitted by Independent Inspection Body such LLoydand have also photograph on it must be present on the welder during work and qualitycontroller will check that welder is authorized to this welding and not by looking at thisbadge.1.4 WPS in industry Industry today uses two common types of welding procedure specifications. One is abroad, general type that applies to all welding processes of a given kind on a specificmaterial. The other is a narrower, more definitive type that spells out in detail the welding ofa single size and type of joint in a specific material or part. The narrower, more definitivetype is most frequently used by manufacturers for their own control of repetitive in-plantwelding operations or by purchasers desiring certain specific metallurgical, chemical, ormechanical properties. However, either type may be required by a customer or agency,depending upon the nature of the welding involved in charge. 2
  • 3. Welding procedure specifications (WPS) are sometimes required by the purchaser togovern fabrication of a given product in a fabricators workshop. Most often, however, thepurchaser will simply specify the properties desired in the weldment in accordance with acode or specification, leaving the fabricator to use a welding procedure that will produce thespecified results. In other cases, the purchaser will prescribe that the fabricator establishesdefinite welding procedure specifications and test them to prove that the resulting welds willmeet requirements specified by the purchaser. Figure 1 pressure use in many industries such as petrochemical, oleo chemical and heavy chemical industry. The pictures above show the almost complete of pressure vessel. 3
  • 4. 2.0 WPS DESCRIPTION In this section, the WPS provided will be given with description and justificationabout all content involve in WPS form that involve . The justification include the applicablecode and detail on welding process. This WPS only can be applied for carbon steel weld onfabrication of pressure vessel. This WPS can use for certain metal codes with thicknessbetween 15.3mm. Any metal part with that thickness can be joint with single vee and singbevel type. All the WPS is referred to ASME BPVC section 9.2.1 The codes In this fabrication of girth weld of nozzle accordance of WPS provided, the ASMEboiler and pressure vessel code (BPVC) section 9 was followed. The ASME boiler andpressure vessel code embraces its own QA system which revolves around satisfying the rulesof the code. This demonstrates that an accredited fabricator has some competenciespermitting them to perform a large amount of their own inspection without the involvementof an Independent Inspection Body, which would be required by other standards for similarinspections. However, there are no agencies or board stopping by using any of the rules of theASME code without being ASME approved. To prove the competence in welding, anIndependent Inspection Body is recommended to approve the WPS and the test.2.2 Welding process – gas tungsten arc welding According to the WPS, gas tungsten arc welding is use as their welding process.GTAW is one of welding process that provide good joining, good penetration and highquality weld. Actually GTAW or TIG usually applied on stainless steel but carbon steel alsoacceptable. Manual welding type mean the weld operation is done by hand weld without anyhelp from robot or machine. The process is used with shielding gas and without theapplication of pressure. The shielding gas used is argon. GTAW can be used with or withoutthe addition of filler metal. The polarity type can be used with either DC or AC, the choicedepends largely on the metal to be welded. For this application, DCEN is use by using 2% 4
  • 5. thoriated tungsten electrode. Direct current welding is typically performed with the electrodenegative (DCEN) polarity. DCEN welding offers the advantages of deeper penetration andfaster welding speeds. Alternating current provides a cathodic cleaning action (sputtering)that removes metal oxides from the surfaces of the weld joint, which is necessary for weldingaluminum and magnesium.2.3 Electrode – Thoriated tungsten 2.4 mm diameter with 7 inch length electrode was used to weld. The tungstenelectrode is made of 2% thorium tungsten that called thoriated tungsten. Thoriated tungstenelectrodes are widely used because they make good welds, deep penetration, long lasting andquite easy to use. These electrodes are normally sharpened by grinding like pencil pointed aspart of the standard procedure while preparing to perform gas tungsten arc welding (GTAW).2.4 Shielding gas - Argon Argon gas with 99.9% purity is use as shielding gas for this type of welding. Argon isa heavy gas that is obtained from the atmosphere by the liquidization of air. Depending on thevolume of use, argon may be supplied as a compressed gas or as a liquid. Furthermore, theargon gas can be purchased at much lower prices in the bulk liquid form compared to thecompressed gas form. This gas is the most widely used type of shielding gas for GTAW thanhelium. Actually there are several advantages by using argon rather than helium. a. Good arc starting b. Produce smooth arc c. Lower flowing rate than helium d. Easy on current setting when welding 5
  • 6. 2.5 Filler metal – ER70S-G The A-number and F-number are indicate 1 and 6. F-number is refer to electrodes andwelding rods to reduce the number of welding procedure and performance qualifications. A-number function is to minimize the number of welding procedure qualifications, steel andsteel alloy filler metals are also grouped according to ASME section 9 tables 3 in appendix.The F-number groupings are based essentially on their usability characteristics, whichdetermine the ability of welders to make satisfactory welds with a given process and fillermetal. The A-number is based on chemical composition of the deposited weld metal. The filler metal used to joint as added metal to joint the metal with base metalthickness 15.3 mm according to WPS. The filler metal code is design by AWS to show thespecification such as strength, type and chemical composition in the filler metal. „ER‟ lettermeans the electrode or filler rod. „70‟ show that the filler rod have tensile strength that canstand to 70000 psi and „S‟ is solid filler rod without any flux in it. Some filler rod havetubular shape contain with flux and „G‟ is chemical composition of the filler rod; 0.05% C,0.31% Si, 1.07% Mn and 0.05% P, 0.82% Ni (refer to Kobelco consumable table inappendix). This filler rod was categorized in high tensile steel and low temperature steel. Inaddition, the rod is suitable for DCEN polarity and shielded by argon gas.2.6 Base metal Carbon steel is use to fabricate the pressure vessel. According to WPS provide, P-Number is 1 and group number is 1 or 2. Base metals are assigned P-numbers in ASMESection IX (QW/QB-422 table at appendix) to reduce the number of welding procedurequalifications required. For ferrous base metals having specified impact test requirements,group numbers within P-numbers are assigned. These assignments are based on comparablebase metal characteristics such as composition, weldability, and mechanical properties. Thislist is an ascending sort based on specification numbers. 6
  • 7. Table 1 P- Number assignment (courtesy of ASME)2.7 Joint design – single vee and single bevel Welder can use this WPS for single vee and single bevel joint. If welder want to usethe specification for other joining type such as double vee, company need to produce newWPS for that joining. The root face at the both joining with gab 3 - 4.5mm produce excellentpenetration and reinforcement and normal practical variations in voltage, current, weldingspeed, and edge preparation cause minimum damage to the backing. For this joint, lowamount of filler wire is needed and also low current input can apply at the first pass of theweld. However single pass weld only can aaply when the thickness of the metal is 4mm andbelow.2.8 Preheating The minimum temperature for preheating is 26 degrees and maximum is 200 degreesCelsius. The temperature for preheating is depending on the thickness of the joint. If thickmaterial 15.3 mm accordance of WPS, maximum temperature of preheat is required.Preheating is important to reduce cooling rate of the metal after welding. In addition, thepurpose of preheat is to reduce risk of hydrogen cracking and reduce the hardness of the weldheat effected zone that contribute to cracking. Sometime the base metal contains moisturethat can produce porosity effect on weld after. So preheating will needed to reduce and givezero moisture to get high quality welding. Preheat method is flame heating on the base metalusing LPG. 7
  • 8. 2.9 Electrical characteristic The polarity in the WPS is direct current electrode negative or straight polarity forGTAW. This polarity is suitable for steel such as mild steel and stainless steel with using thethoriated tungsten as the electrode because the heat concentration is 70% on metal and 30%on electrode. According to ANSI/AWS standard, the electrode must be use in Direct CurrentElectrode Negative (DCEN) only. The polarity to use with a particular electrode isestablished by the electrode manufacturer. The current use actually is not constant. For this type of fabrication, the currentadjustment is depend on thickness of the metal to be joint. The welder should know hoe tocontrol their travel speed during welding to get proper heat input. Refer to WPS, the heatinput is quite slow because the limitation of the GTAW. Even though, GTAW with DCENpolarity produce good arc and deep penetration. According to AWS, the current range; 90 to200 A should use 2.4 mm diameter electrode. This parameter is important to follow to avoidthe electrode become melt due to high heat input.2.10 Welding technique Welder should do the weaving or string technique during the weld. With the stringbead method, weld beads are deposited in a straight line. With the weaving bead method,weld beads are deposited in a zigzag formation. The use of string beads reduces the amountof heat input, because the forward weld travel speed is faster. Therefore, the string beadtechnique should be used instead of the weave bead technique. The exception to the stringbead requirement occurs when welding in the vertical position. In this case, a partial-weavetechnique may be used to facilitate welding. However, the total weave shall not be greaterthan twice the electrode diameter. The cup size is 8mm in diameter. The cup size is depending on filler rod size and gasflow rate use for shielding the metal from oxidation. High flow rate of shielding gas needsuitable gas cup size to prevent metal oxidation and weld deposition such porosity and poorweld shape. This happen cause of the gas pressure concentration is too narrow and hit themolten filler rod and gas trapped in it. If gas cup size is too big, the oxidation will occur dueto gas separation and lack of pressure to shield the metal from air. 8
  • 9. Metal cleaning is very important before do any welding operation. Surface cleaningon weld area should be done to avoid any contaminant such as oil or grease, metal particle,paint or others that not the base metal component. Furthermore, the surface of the grooveneeds to be smooth and not too rough. All the contaminant may cause the welding defect anddiscontinuity such crack due to gas trapped, poor joining cause the oil and grease.3.0 PQR DESCRIPTION This is the justification of the WPS provided in this report. The justification is containthe detailed of the test involve and has third party inspector endorsement. Before the WPS isendorse, the welding coupon provided by fabricator need to be tested. The PQR is the testingreport that approves the pre-WPS is acceptable and can legal to use.3.1 Tensile test Since a large proportion of design is based on tensile properties, it is important thatthe tensile properties of the base metal, the weld metal, the bond between the base metal andweld metal, and the HAZ conform to the design considerations of the weld. Where butt jointsare used, the weld metal needs to develop the minimum tensile properties of the base metal.Tensile strength of weld metal or weld joints is obtained by pulling a specimen to failure. Theexample of the specimen can referred to tensile test speciment in appendix. According toASME section 9 for thicknesses up to and 25 mm, a full thickness specimen shall be used foreach required tensile test. The tension test specimen shall be pulled at two points undertensile load. The tensile strength shall be calculated by dividing the ultimate total load by theleast cross-sectional area of the specimen as calculated from actual measurements madebefore the load is applied. For tensile test have its acceptance range. In order to pass the tension test, thespecimen shall have a tensile strength over than ASME section 9 has decide. a. The tensile strength is not less than minimum tensile strength of the base metal. Refer to table 2 ASME section 9. 9
  • 10. b. The tensile strength is not less than the minimum specified tensile strength of the weaker of the two, if base metals of different minimum tensile strengths are used. c. If the specimen breaks in the base metal outside of the weld or weld interface, the test shall be accepted as meeting the requirements, provided the strength is not more than 5% below the minimum specified tensile strength of the base metal. For this report, two specimens, SA-333 grade 6 has been tested for this test.According to the PQR the ultimate total load 10500 kg approximately has been applied fortensile stress purpose. Refer to result record, the test is acceptable. The specimen was brokenat the base metal and the tensile strength is obtained with 515.11 MPa over than minimumtensile stress (415 MPa) provide by ASME section 9 . By refer to table 2 ASME section 9 atappendix this result have proved that the weld is stronger than base metal3.2 Guided bend test One of the most common tests used in the development of welding procedures is thebend test. The bend test is used to check the relative ductility of welded joint or weld testspecimen. The specimen is usually bent in a special guided test jig. The specimens aresubjected to strain at the outer fiber by bending the specimen to a specified radius that isbased on the type of material and specimen thickness. Codes generally specify a maximumallowable size for cracks in a bend specimen. Cracks and tears resulting from a lack ofductility or discontinuities in the weld metal are evaluated for acceptance or rejection to theapplicable code requirements. Guided-bend test specimens shall be prepared by cutting the test plate or pipe to formspecimens of approximately rectangular cross section. The cut surfaces need to design thesides of the specimen. There are two surfaces shall be called the face and root surfaces, theface surface having the greater width of weld. The specimen thickness and bend radius areshown in figure 3 courtesy of ASME section 9 at appendix. 10
  • 11. The transverse side bend test is use for thickness is less than 25mm according toASME section 9. The weld is transverse to the longitudinal axis of the specimen, which isbent so that one of the side surfaces becomes the convex surface of the bent specimen.Transverse side-bend test specimens shall conform to the dimensions shown in figure 4courtesy of ASME section 9 at appendix. To accept the test some requirement need toachieve before proceed to other test. a. The weld and heat-affected zone of a transverse weld bend specimen shall be completely within the bent portion of the specimen after testing. b. The specimen should have no open discontinuity in the weld or heat-affected zone exceeding 3mm measured at any direction of the convex surface. c. Eye contact discontinuities such as crack occurring on the corners of the specimen during testing shall not be considered unless there is record or evidence that proved from lack of fusion, slag inclusions, or other internal discontinuities.3.3 Hardness test This is a very common testing method and essentially characterizes the strengthproperties of the material. The test consists in applying a standard indenter placed on aground, polished and etched surface of the specimen for specified period. The specimenundergoes localized plastic deformation in the immediate vicinity of the indenter. A varietyof indenter geometry and material and corresponding loads have been standardized. In the Vickers hardness test, an indenter of a definite shape is pressed into the workmaterial, the load removed, and the resulting indentation measured. The full load is normallyapplied for 10 to 15 seconds. 3 major component need to test according to ASME section 9 ;base metal, HAZ and weld metal. The hardness number is calculated by dividing the load bythe surface area of the indentation. The indenter for the Vickers test is made of diamond inthe form of a square-based pyramid as figure 2. The depth of indentation is about one-seventhof the diagonal length. The Vickers hardness value is preceded by the designation (HV). TheVickers hardness number is the same as the diamond pyramid hardness number (DPH). 11
  • 12. Figure 2 The shape on the specimen surface after 10 second indented3.4 Charpy V-Notch impact test According to ASME section 9,charpy impact test is not necessarily unless it isrequired by other section or codes. The Charpy impact test is a pendulum type single-blowimpact test where the specimen is supported at both ends as a simple beam and broken by afalling pendulum as figure 4 in appendix. The energy absorbed, as determined by thesubsequent rise of the pendulum, is a measure of the impact strength or notch toughness of amaterial. The tests results are usually recorded in foot-pounds. The type of notch and theimpact test temperature are generally specified and recorded, in addition to specimen size (ifthey are sub-size specimens, smaller than 10 mm × 10 mm). 12
  • 13. 3.0 CONCLUSION In the development of WPS, the initial procedure test is required. The engineer mightbe consider testing a limited number of specimens to reassure both himself and the client thatthe materials are worthy of prequalification. Qualification is a significant factor in the cost ofmost fabrications; therefore, one must take advantage of prequalification wheneverpermissible. This is why engineers often will specify a desired procedure in terms of morethan one process, each of which is prequalified separately or they will combine the results ofseveral procedures into a single “hybrid” procedure, which can then be offered (withsupporting data) to considered WPS is readily qualified. 13
  • 14. 4.0 REFFERENCES 1. Welding Technology For Engineers edited by Baldev Raj, V Shankar and A K Bhaduri (2006). 2. ASME Boiler and Pressure Vessel Code (BPVC) Section 9 handbook (2007) 3. American Petroleum Institute (API) Recommended Practice 577 Welding Inspection and Metallurgy First Edition, (October 2004) 4. The Practical Welding Engineer Handbook by J. Crawford Lochhead and Ken Rodgers. 5. Welding Inspection Handbook by AWS Third Edition (2000) 6. http://www.ckworldwide.com/technical_specs.pdf 7. http://www.esabna.com/euweb/oxy_handbook 8. http://www.locknstitch.com/PreheatWeld.htm 14

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