Sisguide Wps & Pqt.docx

Guide to understanding Welding Procedure Specification (WPS), Procedure Qualification Record (PQR), & Welder Performance Qualification Record (WPQR)

CONTENTS Introduction............................................................................................................................. What is Welding Procedure Specification (WPS)?.................................................................. What is Procedure Qualification Record (PQR)?.................................................................... What information should they include?................................................................................... What is a Prequalified WPS?.................................................................................................. What are SWPSs?.................................................................................................................. What is Welder Performance Qualification Record (WPQR)?................................................ Acceptance Standards............................................................................................................ Documentation........................................................................................................................ PQR/ WPQR Testing.............................................................................................................. Weld Inspection and Testing...................................................................................................

Introduction Welding requires skill. Determining “how to weld” requires knowledge regarding the materials being welded and welding process, among numerous other factors. Because of huge number of variables involved, the knowledge of the welding engineer and the skill of the welder need to be validated by a series of tests. All this information is documented on Welding Procedure Specification (WPS), Procedure Qualification Record (PQR), Welding Procedure Qualification Record (WPQR), and associated Test Reports. What is Welding Procedure Specification (WPS)? A WPS is a document that describes how welding is to be carried out in production. Its purpose is to aid the planning and quality control of the welding operation. They are recommended for all welding operations and most application codes and standards make them mandatory. What is Procedure Qualification Record (PQR)? A PQR is required when it is necessary to demonstrate that your company has the ability to produce welds possessing the correct mechanical and metallurgical properties. A welding procedure must be qualified in accordance with the requirements of an appropriate welding procedure standard, such as ASME Sec IX, as follows: 1. Produce a welding procedure specification (WPS) as stated above.

2. Weld a test piece in accordance with the

requirements of your specification. The joint set up, welding and visual examination of the completed weld should be witnessed by a certified welding inspector such or an Inspection Body. The details of the test such as the welding current, pre-heat etc., must be recorded during the test. 3. Once the welding is complete the test piece must be subject to destructive and non destructive examination such as radiography and mechanical tests as defined by the welding procedure standard. This work must be carried out in a qualified laboratory but the Inspection Body may require witnessing the tests and viewing any radiographs. 4. If the test is successful you or the test body completes the appropriate documents which the test body’s surveyor signs and endorses. What information should they include? Sufficient details to enable any competent person to apply the information and produce a weld of acceptable quality. The amount of detail and level of controls specified on a WPS is dependant on the application and criticality of the joint to be welded. For most applications the information required is generally similar to that recorded on a Procedure Qualification Record (PQR), except that ranges are usually permitted on thicknesses, diameters, welding current, materials, joint types etc.

If a WPS is used in conjunction with an approved procedure qualification record (PQR) then the ranges stated should be in accordance with the approval ranges permitted by the PQR. However careful consideration should be given to the ranges specified to ensure they are achievable, so that these ranges represent good welding practice. What is a Prequalified WPS? Some codes, allow “Prequalified WPS”, whereby it is established that the WPS written per code will produce welds with correct mechanical and metallurgical properties. It is not necessary to prepare a PQR in such cases. However, the prequalified WPS have a specified range of parameters under which the weld must be produced. When welding variables fall outside these ranges, a WPS with supporting PQR must be prepared. What are SWPSs? In an effort to standardize and harmonize the process of WPS approvals, AWS started writing “Standard Welding Procedure Specifications (SWPSs)” with input from the pioneers and experts in the welding industry. An extensive testing program was undertaken whereby; these SWPSs were then supported by numerous PQRs. When the use of SWPSs is permitted by referencing code section, your company does not have to perform one or more procedure qualification tests. Welding Variables Variables used in a welding procedure test are divided into 3 categories :

Essential Variables Are variables that have a significant affect on the mechanical properties of a joint. They must not be changed except within the limits specified by this code. e.g. Material thickness range, Material Group etc.



Non-Essential Variables Are variables that have no significant affect on mechanical properties. They can be changed without re qualification of the PQR.



Supplementary Variables Are variables that have an affect on the impact properties of a joint. They are classed as Non-Essential if impact testing is not required

All variables listed as essential, non-essential or supplementary should be addressed on both the WPS and the PQR. If any of the variables do not apply to the particular application then they should be specified as not applicable. Joint Configuration Either plate or pipe can be used for the test piece (plate approves pipe and vice versa ref. QW211), any welding position approves all positions providing no impact tests are required ref. tables QW250 to QW265 and any joint geometry approves all geometry's, e.g. single V, double V, U prep, backed or unbacked.

A butt or groove weld approves branch and fillet welds but not the converse, ref. QW202. Non pressure retaining fillet welds in pipe or plate can be tested but they must be double sided if plate and at least the dimensions illustrated in QW462.4a, ref. QW202.2c. Pressure retaining branch welds must be qualified by groove (butt) welds. Material

Grouping

Materials are assigned P numbers in QW420; a test in one P number approves all materials listed under that P number, except where impact tests are required then approval is restricted to materials listed in the group number within the P number. Other P number groupings are permissible ref. QW424.1 for details. Ref QW 424.1 for further details. It is normally permissible if the material is not listed in QW422 to assign it to a P number which lists materials with the same metallurgical and mechanical properties although this is not in strict conformance with the code. Typically BS1501 151 430A low carbon steel could be regarded as P1 and stainless steels such as 316, 304 as P8. Note P5, 9 & 10 are divided into sub groups eg 5A,5B etc., Treat each sub group like a separate P Number Dissimilar materials are acceptable providing they are compatible. For example P1 to P8, but this does not cover P1 to P1 or P8 to P8. Note S numbers are for pipework to B31, a P number covers an S number but not the converse Consumables The ASME code uses its own specifications for consumables SFA. which is almost identical to the AWS specification. NOTE A change in consumable is only permissible providing it has the same F number and A number (if applicable) As

the

P.Q.R..

ThicknessLimits Thickness limits Groove welds. See QW451 for precise details. 

When Impact tests are required the minimum thickness approved is restricted. See QW403.6



More than one PQR may be required to qualify dissimilar thickness

The thickness little 't' of deposited weld metal for each process involved is approved from 0 to 2xt except:

MIG/MAG (GMAW/FCAW) dip transfer weld of deposited thickness less than ½" approves maximum thickness of 1.1 x t only Ref: QW255 (QW403.10)



If any Pass in a single or multipass weld > ½" then the thickness approval equals 1.1xT

Dissimilar Thickness QW202.4:- The thicker and thinner part must be qualified, Except P8 and P4X the thinner part can be qualified if no Impacts and test coupon > 6mm thick.

Thickness limits for fillet welds as per QW462.4a or QW462.4d qualify all fillet weld sizes on all base material thicknesses and all diameters in one test. Testing Requirements (Ref QW 463 for location of specimens) Unlike EN288 there is no requirement for any non-destructive testing such as radiography or MPI/DPI, although I would recommend radiography for butt welds. The testing requirement for groove welds are as follows:

Two Transverse tensile tests (QW150).



Two Root bends and Two face bends unless the plate thickness exceeds 3/8" then 4 side bends are required. All bend tests should be done to QW160 using the correct former ref. QW466 to an angle of 180 degrees. Longitudinal (all weld) bend tests are not recommended unless the base/weld materials differ markedly in bending properties. See QW 466 for exceptions and precise details.

The testing requirement for fillet welds on plate is 5 macro sections only, for Pipe fillet welds 4 macro sections. No fracture test required. The combination of welding processes and pipe diameters listed below were used for performance qualification:

(1) 2 in. Sch. 80 (.218) pipe with open butt using GTAW process. (2) 2 in. Sch. 160 (.343) pipe with consumable insert and fill pass using the GRAW process and the remainder welded with SMAW process. (3) 6 in. XXS (.864) using SMAW process with backing.

Multi Process Welding Procedures QW200.4 and QW451.1

Base Metal approval range for the above welded joint is 4.76mm To 52mm Ref QW451.1If the joint is made of more than one welding process then the maximum deposited thickness each process in the above example is (2 x Deposited Weld Metal t) :- GTAW 12mm and SMAW 52mm (This is because t = T for this process as t > 19.1mm QW451.1)

If the SMAW deposit in the above qualification was less than 19.1mm, assume 18mm and GTAW 8mm then to weld a joint 52mm thick with 8mm GTAW and 44mm SMAW is not permitted as maximum SMAW deposit would be 36mm You can delete the SMAW and qualify an all GTAW weld 4.76mm To 12mm thick or delete the GTAW and weld SMAW 4.76mm to 52mm thick, providing all the essential, non essential and supplementary variables are applied to the WPS. (Note the procedure allows the SMAW to be used as a root run but not the welder qualification.) When tested the deposited weld metal of each process must be included in the tension and bend test specimens and impacts where applicable. Note it is acceptable for the impact test for the GTAW to contain some SMAW in the test specimen. PICK and MIX QW200.4 b [Note restrictions in QW451.1 notes (1)] This applies to test coupons 13mm and thicker and welding processes SMAW, SAW, GTAW, GMAW. A WPS consisting of several processes can be created from different PQR’s, but the maximum thickness of base metal covered by this WPS can’t exceed 2 x the thickness of the thinnest test coupon used for each PQR and each process can’t exceed 2 x its deposited thickness. This applies even if all the processes used for that coupon are not required in this WPS. However the base metal thickness of the PQR used for the root does not have to be considered if the WPS is single sided QW200.4 b Note test coupons 38mm and above approve deposited weld metal and also base metal thickness up to 200mm max QW451.1. (QW403.7 Processe GTAW,SMAW,GMAW,SAW) EXAMPLE

Can the proposed PQR be made from the above example + PQR 2 + PQR 3. Consider individual deposited thickness 2 x t GTAW 12mm > 6mm. SMAW 60mm > 39mm. GMAW 66mm > 20mm All OK Consider Plate thickness 2 x T SMAW 60mm <65mm Fail. GMAW 66mm > 65mm OK. GTAW not considered. SMAW procedure can’t be used for proposed PQR

PQR/ WPQR Testing

The following tests by Independent Test Laboratory may be required on your PQR and WPQR Coupons: 

Weld Visual Examination by a Certified Welding Inspector



Bend Test



Hardness Test



Transverse Tensile Test



All Weld Metal Tensile Test



Charpy Impact Test



Weld Metal Chemical Analysis



Macroetch Test



Nick Break Test



Radiography Test



Ultrasonic Test

What is Welder Performance Qualification Record (WPQR)? Once the procedure is approved it is necessary to demonstrate that all your welders working to it have the required knowledge and skill to put down a clean sound weld. If the welder has satisfactorily completed the procedure test then he is automatically approved but each additional welder must be approved by completing an approval test to an appropriate standard such as ASME Sec IX as follows: 1. Complete a weld test as stated above. The test should simulate production conditions and the welding position should be the position that the production welds are to be made in or one more severe. 2. For maximum positional approval a pipe inclined at 45 degrees (referred to as the 6G position) approves all positions except vertical down. 3. Test the completed weld in accordance with the relevant standard to ensure that the weld is clean and fully fused. 4. For a butt weld this is normally a visual examination followed by radiography or bend tests. 5. Once the test is completed the necessary forms have to be completed by you or the test body and signed by the test body’s surveyor. 6. Note that any changes that require a new welding procedure (WPS) may also apply to the welders approval, refer to the referencing code/ standard for precise details Article III of Section IX defines the requirements for welder qualification. Essential variables that apply to the welder qualification test are listed by weld process. It is important to note that if a welder qualifies to one WPS using a specific welding process the welder is also qualified to the manufacturer’s other WPS using that same process within the limits of

the essential variables. The most common welding process Meyer Tool employs in the fabrication of cryogenic, vacuum, and pressure equipment is the Gas Tungsten Arc Welding (GTAW) processes. The essential variables for welder qualification as defined by Section IX for this process are:

Table 1 Welder Qualification Essential Variables for the GTAW Process WQR Essential Variable

Explanation

With or without backing.

Generally it is easier to execute a weld if it is backed. Performing the test without backing qualifies the welder for either.

P number of base material and

Base metals are assigned P numbers. QW-424 lists combinations of metals and

pipe diameter (if the coupon is

the ranges qualified by P number. Different pipe diameters qualify the welder

a pipe)

for ranges of diameter and for flat plates.

Use

of

filler

metal

or

Filler metals are assigned F numbers. QW-433 lists combinations of filler metals

autogenous, F number of filler

and ranges qualified. The WPS will often limit these further, so correct

metal, and thickness of weld

combinations of filler and base metals are used. Up to 0.5” the welder qualifies

deposited.

from the thickness of weld deposited to two times that thickness.

Position, 1G through 6G and

The position of the weld and the progression are important parameters in welder

vertical up or down.

performance. From easiest to perform 1G (flat) to hardest 6G (on a 45 degree angle) with an upward progression. Performing the test to 6G with an upward progression qualifies the welder for all positions.

Type of inert backing gas.

This variable will be specified in the WPS for a GTAW process.

Current of polarity.

This variable will be specified in the WPS for a GTAW process.

The WPS also defines essential variables or limits that the welder must meet during performance of the weld coupons. The Code is set up such that through judicious selection of the essential and non-essential variables utilized in producing a weld coupon, the welder can be qualified for a wide range of situations. A series of tables in Section IX define these ranges. Using the GTAW process again as our example, if we define the test coupon requirements as follows, we see the following qualification limits for a welder: Table 2 Welder Qualification Example for Variable Selection and Range Qualified

Variable

Selection

Range Qualified

Type of Weld

Groove

Groove or Fillet

Base Metal

304SS (P-8 to P-8)

P-1 through P-11, P-34, P41 through P49

Filler Metal

308LSS (F6)

All F6 filler metals

Thickness of metal deposited

0.375”

.375” to .75”

Position

6G

All positions.

Pipe Diameter

2.63” diameter pipe

1” OD to unlimited diameter and flat plates.

All weld coupons must be visually inspected and undergo either mechanical testing or radiographic testing to assess their acceptability. The welder’s qualification range and the results of the coupon test are documented on a Welder Qualification Record (QWR) form. Depending upon the skill and experience of the welder, he or she will have multiple QWR forms. For example, to qualify to the full range of Meyer Tool’s WPS for cryogenic welding of stainless steel, GTAW-SS/LT, a welder would have to perform at minimum nine (9) qualification tests. Ensuring the skill level of those performing critical manufacturing processes is of key importance. Welding is a critical process; the procedures and personnel used to perform welding should be qualified to a national standard. Meyer Tool reduces your Project Risk in order to achieve the Lowest Total Cost of Ownership by certifying our welders to the stringent requirements of Section IX of the ASME B&PV Code.

Acceptance Standards In general welds must show a neat workman like appearance. The root must be fully fused along the entire length of the weld, the profile of the cap should blend in smoothly with the parent material and the weld should be significantly free from imperfections. Reference should be made to the acceptance standard for precise details. Documentation The necessary documents for a successful Welding Program are as follows: 1. Welding Procedure Specification (WPS), Procedure Qualification Record (PQR), Independent Laboratory Test Report for the PQR, Welder Performance Qualification Record (WPQR), and Independent Laboratory Test Report for the WPQR; OR 2. Pre-qualified Welding Procedure Specification (Applicable to some Codes only), Welder Performance Qualification Record (WPQR), and Independent Laboratory Test Report for the WPQR; OR 3. Code adopted Standard Welding

Procedure Specification (SWPS), Welder Performance Qualification Record (WPQR), and Independent Laboratory Test Report for the WPQR PQR/ WPQR Testing 

The following tests by Independent Test Laboratory may be required on your PQR and WPQR Coupons:



Weld Visual Examination by a Certified Welding Inspector



Bend Test



Hardness Test



Transverse Tensile Test



All Weld Metal Tensile Test



Charpy Impact Test



Weld Metal Chemical Analysis



Macroetch Test



Nick Break Test



Radiography Test



Ultrasonic Test



Weld Inspection and Testing



In addition to the above, you may require independent inspection of the welds by the following qualified personnel:



Visual Inspection by Certified Welding Inspector (CWI



Radiographic Testing by Level II personnel certified as per SNT-TC-1A



Ultrasonic Testing by Level II personnel certified as per SNT-TC-1A



Magnetic Particle Testing by Level II personnel certified as per SNT-TC-1A



Penetrant Testing by Level II personnel certified as per SNT-TC-1A