Welding Procedure Specifications

Welding Procedure Specification Example

A WPS is a document that describes how welding is to be carried out in production. They are recommended for all welding operations and many application codes and standards make them mandatory

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) or Welding Procedure Approval Record (WPAR), except that ranges are usually permitted on thicknesses, diameters, welding current, materials, joint types etc.

If a WPS is used in conjunction with approved welding procedures then the ranges stated should be in accordance with the approval ranges permitted by the welding procedure.

However careful consideration should be given to the ranges specified to ensure they are achievable, as the ranges given by welding procedure standards do not always represent good welding practice. For example welding positions permitted by the welding procedure standard may not be achievable or practical for certain welding processes or consumables.

EN ISO 15609-1 (formally EN 288 Part 2) European Standard For

Welding Procedure Specifications EN ISO 15609 Defines the contents of a Welding Procedure Specification in the form of a list of information that should be recorded. For some applications it may be necessary to supplement or reduce the list. For example only in the case of a procedure requiring heat input control would there be a necessity to quote travel speed or run-out length for manual processes.

ASME IX American Boiler and Pressure Vessel Code QW 250 Lists the variables for each welding process, all the variables stated should be addressed. The range permitted by the WPS is dictated by the PQR or PQR’s used to qualify it.

Typical Items That Should Be Recorded On W.P.S:-

Common to all Processes .

• Procedure number• Process type• Consumable Size, Type and full Codification.• Consumable Baking Requirement if applicable• Parent material grade and spec.• Thickness range.• Plate or Pipe, Diameter range• Welding Position• Joint Fit Up, Preparation, Cleaning, Dimensions etc.• Backing Strip, Back Gouging information. • Pre-Heat (Min Temp and Method)• Interpass If Required (Maximum Temperature recorded )• Post Weld Heat Treatment. If Required (Time and Temp)• Welding Technique (weaving,max run width etc.)• Arc Energy Limits should be stated if impact tests are required or if

the material being welded is sensitive to heat input.

Specific To Welding Processes MMA TIG MIG MAG

SUB ARC

FCAW

Welding current yes yes yes yes

Type of Welding current AC/DC Polarity

yes yes yes yes

Arc voltage If Auto yes yes

Pulse parameters (Pulse time and peak & backgound current)

If Used If Used

Welding Speed If Mechanised yes yes yes

Wire configuration yes

Shielding gas (comp,flow rate) yes yes

Purge gas (comp & flow rate) If Used If Used

Tungsten electode Diameter and type. yes

Nozzle diameter yes yes

Type of Flux Codification & Brand Name

yes

Nozzle Stand Off Distance (Distance from tip of nozzle to workpiece).

yes

Sketches A sketch of the joint configuration is required which should include the basic dimensions of the weld preparation. Some indication of the run sequence is also beneficial, particularly if the correct sequence is essential to ensure the properties of the weld are maintained.

Production Sequence Whilst this is good practice it is not a requirement of either ASME 9 or EN288 Part 2; it could be issued as a separate QA procedure if preferred.

Non Destructive Testing A WPS is primarily concerned with welding not N D T, this activity should be covered by separate N D T procedures.

Welding Procedure Specifications

This is a simple instruction sheet giving details of how the weld is to be performed, its purpose is to aid the planning and quality control of the welding operation. EN ISO 15609 (formerly EN288 Part 2) specifies the contents of such a specification in the form of a list of items that should be recorded, however only relevant information need be specified, for example only in the case of a procedure requiring heat input control would there be a necessity to quote travel speed or run out length for manual processes.

A weld procedure specification may cover a range of thicknesses, diameters and materials, but the range must be specified and be compatible with the rest of the parameters on the document. I suggest that you produce a new WPS for each type of joint and keep to the ranges of thickness and diameters specified in the welding procedure standard.

Welding Procedures Welding procedures are 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 qualified in accordance with the requirements of an appropriate welding procedure standard such as EN ISO 15614 Part 1 as follows:-

1. Produce a welding procedure specification 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 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 can be carried out in any laboratory but the Inspection Body may require to witness the tests and view any radiographs.

4. If the test is successful you or the test body complete the appropriate documents which the test bodies surveyor signs and endorses. The necessary documents are as follows:-

E1 Welding Procedure Approval Test Certificate This is the front sheet and only gives details of what the procedure can be used for. i.e. its range of approval.

E2 Details Of Weld Test This gives details of what actually took place during the test weld it is similar to a WPS but should not include ranges of welding parameters.

E3 Test Results Details of NDT and Mechanical testing Results

E4 Welder Approval Test Certificate. This is the welder approval part of the qualification.

Note The E1, E2, E3, E4 designations are used by some Inspection Authorities to refer to the individual forms. Examples of these forms are given in annexes of EN ISO 15614 and EN287.

Forms E1, E2, E3 may be referred to as the WPAR (Welding Procedure Approval Record) or WPQR (Weld Procedure Qualification Record).

In general a new welding procedure must be qualified for each of the following changes subject to the individual requirements of the appropriate standard used:-

• Change in parent material type. • Change of welding process • The diameter range for pipe given by the welding standard is

exceeded. Typically 0.5xD to 2xD.

• The thickness range is exceeded. Typically 0.5xt to 2xt.

• Any other change required by the welding standard.

Welder Approval 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 EN 287 part 1 as follows:-

Complete a weld test as stated in 2) 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 For maximum positional approval a pipe inclined at 45 degrees (referred to as the 6G position) approves all positions except vertical down.

Test the completed weld in accordance with the relevant standard to ensure that the weld is clean and fully fused. For a butt weld this is normally a visual examination followed by radiography.

Once the test is completed the E4 form has to be completed by you or the test body and signed by the test bodies surveyor.

Note The above changes that require a new welding procedure may also apply to the welders approval, refer to the standard for precise details.

ASME 9 ASME 9 as far as the pressurised systems regulations are concerned can be considered as equivalent to EN ISO 15614-1 /EN 287. However it may not be contractually acceptable. The advantage in using ASME is that generally fewer procedure tests are required particularly when welding pipework.

Welder Approval Without A procedure BS 4872 is for the qualification of welders where a weld procedure is not required either by the application standard that governs the quality of

production welds or by contractual agreement. Typically applied per BS2971 for welding of boiler pipework less than 17 bar g and 200°C. Basically the same rules mentioned above for the welder approval apply.

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.

Its a good idear to ensure that you can achieve the appropriate standard before you call in an Inspection Body. Penetration defects and lack of fusion can often be easily detected by sectioning welds and bending them.

Welder Performance Qualification (WPQ)

Materials The purpose of this test is to determine the welders ability to deposit a sound weld therefore the base material is not considered as critical as it is in the PQR. Hence a performance test on any material in P groups 1 to 11 approves all those groups and sub groups, also P34 and P4X (P40-P49). Providing a compatible consumable exists with the same F number used in the qualification test. (QW423.1)

Note a single sided weld is classed as a weld without backing and a double sided weld or weld with sealing run is classed as a weld with backing

Consumables The F number cannot be changed without re qualification of the welder except that for performance qualification only using SMAW (MMA) F numbers up to and including 4 approve all lesser F numbers for double sided or welds with backing only. One Consumable from F41 To F45 approves any of these consumables, except SAW. Ref. QW404.11.

Note 'A' numbers do not apply to welder approval tests.

Variables For each welding process there is a list of essential variables in QW352 to

QW357 and QW360 for welding operators, these are not necessarily the same as the ones for the PQR. Essential variables cannot be changed. Explanations of all these variables is given in section IV of the code.

Diameter and Thickness Ranges Diameter limits for all circular welds including groove welds, branch welds and fillet welds is given in QW452.3. there are no upper limits on diameters approved and pipe covers plate

Note for branch welds the diameter considered for the above limits is the one containing the weld preparation.

Thickness limits, groove welds. The thickness limit only applies to the deposited weld metal thickness not the plate thickness and any groove weld approves all fillet weld sizes. For t greater than 12.5mm there is no restriction on the size that can be welded (Providing the test weld deposit contains at least 3 layers of weld).

Thickness limits, fillet welds. A test on plate greater than 3/16" approves all base metal thicknesses and fillet weld sizes ref. QW452.5. (Note the above diameter limits apply unless the fillet weld is qualified by a groove weld)

Joint Configuration Joint geometry, a double V (or U) is considered the same as a joint with backing and does not qualify a single V (or U) without backing, but a single full penetration joint without backing qualifies all joint configurations.

Approval Range Extent of approval is very well explained in QW461.9. Take particular note of welding positions which are also explained in QW461, for example to qualify a fillet weld in the normal horizontal-vertical position with a groove weld, the groove weld must be qualified in at least the 2G position. The welding positions defined in QW461.1.& QW461.2 should be referred to in the WPS. The position designations: 1G ,2G ,3G ,4G ,5G ,6G (Groove Welds) and 1F ,2F ,3F ,4F (Fillet Welds) are test positions

Period of Validity/Renewal of Qualifications (QW 322.2)

Providing the welder uses the process for which he is qualified and there is no reason to question his ability then his qualification lasts indefinitely.

If the welder does not use the welding process for which he is qualified for a period of 6 months or more then he must perform a new test in pipe or plate, any parent material, thickness and position, if successful all the welder approvals for that welding process are renewed in one test.

Testing Requirements Test requirements for groove welds QW452 consists of either:-

• One face bend and one root bend except for welding positions 5G & 6G which require 4 bends (Ref QW452.1 Note 4). If the plate exceeds 3/8" side bends may be used. See QW 466 for precise details and exceptions.

Note:- Bend Tests can in most cases be replaced by Radiography {See Below}.

• Radiography is optional and must be supplemented by bend tests when using GMAW (MIG/MAG) with dip transfer (Short Circuiting Arc) or when welding some special materials. Ref. QW304.

Note:- Ultrasonic Examination in lieu of Radiography is not permitted

Test requirements for fillet welds in plate ref. QW452.5:-

• One macro section (QW 184) and One fracture test (QW182).

The location where each specimen has to be taken is defined in QW463

Radiography Ref QW 191

• A length of at least 6" must be examined for plate or the entire circumference for pipe.

• If the pipe circumference is less than 6" then more samples must be welded up to a maximum of 4. Ref QW 302.2.

Visual Examination Ref QW 302.2 & QW 190

Performance test coupons must show complete joint penetration with full fusion of the weld metal and base metal.

The welder performance test must follow a properly qualified W.P.S. Once qualified the welder must always work within the extent of approval of any properly qualified W.P.S. and his W.P.Q.

The welder who qualifies the P.Q.R. is automatically approved within the limits specified in QW304, QW305 and QW303. Ref QW301.2.

Specialist Processes Such as corrosion resistant overlay or hard facing are covered in QW 453. Procedure variables are defined with all procedure variables in QW252 and in QW380 for welder approval.

Min base thickness approved = size welded or 1", QW 453

Min Deposit Size Approved:- Point Where Chemical analysis taken No upper limit QW402.16 (462.5a) Welding Positions QW405.4 Performance Qualification approves all deposit thickness’ No min.QW381

ASME Definitions, Consumables, Welding Positions

ASME P Material Numbers Explained

ASME has adopted their own designation for welding processes, which are very different from the ISO definitions adopted by EN24063.

Designation DescriptionOFW Oxyfuel Gas WeldingSMAW Shielded Metal Arc Welding (MMA)SAW Submerged Arc WeldingGMAW Gas Metal Arc Welding (MIG/MAG)FCAW Flux Cored Wire GTAW Gas Tungsten Arc Welding (TIG)PAW Plasma Arc Welding

Straight polarity = Electrode -ve

Reverse polarity = Electrode +ve

ASME F Numbers

F Number

General Description

1 Heavy rutile coated iron powder electrodes :- A5.1 : E70242 Most Rutile consumables such as :- A5.1 : E60133 Cellulosic electrodes such as :- A5.1 : E60114 Basic coated electrodes such as : A5.1 : E7016 and E70185 High alloy austenitic stainless steel and duplex :- A5.4 : E316L-166 Any steel solid or cored wire (with flux or metal)

2X Aluminium and its alloys3X Copper and its alloys4X Nickel alloys5X Titanium6X Zirconium7X Hard Facing Overlay

Note:- X represents any number 0 to 9

ASME A Numbers These refer to the chemical analysis of the deposited weld and not the parent material. They only apply to welding procedures in steel materials.

A1 Plain unalloyed carbon manganese steels.A2 to A4 Low alloy steels containing Moly and Chrome MolyA8 Austenitic stainless steels such as type 316.

ASME Welding Positions Graphic Representation

Note the welding progression, (vertically upwards or downwards), must always be stated and it is an essential variable for both procedures and performance qualifications.

Welding Positions For Groove welds:-

Welding Position Test Position ISO and ENFlat 1G PAHorizontal 2G PCVertical Upwards Progression 3G PFVertical Downwards Progression 3G PGOverhead 4G PEPipe Fixed Horizontal 5G PFPipe Fixed @ 45 degrees Upwards 6G HL045Pipe Fixed @ 45 degrees Downwards

6G JL045

Welding Positions For Fillet welds:-

Welding Position Test Position ISO and ENFlat (Weld flat joint at 45 degrees) 1F PAHorizontal 2F PBHorizontal Rotated 2FR PBVertical Upwards Progression 3F PFVertical Downwards Progression 3F PGOverhead 4F PDPipe Fixed Horizontal 5F PF

Welding Positions QW431.1 and QW461.2 Basically there are three inclinations involved.

• Flat, which includes from 0 to 15 degrees inclination• 15 - 80 degrees inclination• Vertical, 80 - 90 degrees

For each of these inclinations the weld can be rotated from the flat position to Horizontal to overhead.