WELDING PROCEDURE SPECIFICATION

WELDER QUALIFICATION AND ITS DOCUMENTATION

SCOPE

·        All welding processes should be qualified as per ASME section IX before start the welding on job.

·        All the welder in the company should be qualified in specified welding process.

STANDARDS

·        ASME section IX: Pressure equipment fabrication

·        AWS D1.1:  welding of structures whose material of construction is steel

·        AWS D1.2: welding of structures whose material of construction is Aluminum

BASICS

·        In welding of pressure vessel or other heavy fabricated equipment’s which are manufactured by welding then all the welding joints should be sound in strength as per required application and looks visually better.

·        Welding a specific job requires lots of knowledge and experience.

·        Along with those experience and knowledge welder can give the sound welding quality.

·        But as everyone knows that there is a standards for every process hence we are comparing our welding quality and process with this standards.

·        As any student needs to clear an exam to get a post in various field, like that every welder should give the exam before starting the welding and it’s called the welder qualification.

ABBREVIATION  

·        WPS: welding procedure specification

·        PQR: procedure qualification record.

·        WPQ: welder performance qualification.

 

WELDING PROCEDURE SPECIFICATION

·        WPS is nothing but the control on in-process welding’s in the shop.

·        WPS is a record of welding parameters as per standard which gives the path/direction to the welder for welding.

·        Its main aim is all the welding in the shop floor should be done as per given standard to avoid measurable/noticeable defects.

·        For every welding process required standard parameters like weld consumables, PWHT, position, Material of construction etc. parameters are mentioned in the WPS documents.

·        Welder should follow the WPS parameters during welding for specified welding process.

·        WPS is prepare as per ASME section IX QW-482.

WPS DATA

Welding Process and its type

·        SMAW / GTAW & Manual / Auto

Weld joint (QW-402)

·        Joint design, backing, backing material, retainers etc.

Base metal (QW-403)

·        P number & Group number of both base metal.

Filler metal (QW-404)

·        Process, F number, A number, SFA number, AWS class, size, make etc.

Thickness range

·        As per required thickness in mm.

Position (QW-405)

·        Position (1G, 2G, 3G etc.), welding progression (up-fill / down-fill) etc.

Electrical characteristics (QW-409)

·        Current, polarity, volts etc.

Preheat (QW-406)

·        Mention preheat temperature limits, inter-pass temperature etc.

PWHT (QW-407)

·        If required mention method of heat treatment and temperature range.

 

WELDING SPECIFICATIONS

·        It is of mainly three types as below

Essential parameters

·        This are the very important parameters regarding welding.

·        As the any one of the essential parameter is change beyond the qualified limit, the WPS needs to be re-qualify.

·        This variables are affected on mechanical properties of the weld joints.

·        Below chart shows that the essential parameters for different welding type.

Weld type	Welding parameters
	Base metal	Filler metal	Position	Gas	PWHT	Electrical
SMAW	P number & thickness	F number, t of weld deposit	Weld position	------	As per requirement	-----
OFW	P number & thickness	F number, t of weld deposit	Weld position	Type of fuel gas	As per requirement	-----
GMAW	P number, thickness & pipe diameter	F number, t of weld deposit	Weld position	Backing gas	As per requirement	Transfer mode
FCAW	P number, thickness & pipe diameter	F number, t of weld deposit	Weld position	Backing gas	As per requirement	Transfer mode
SAW	P number, thickness & pipe diameter	F number, t of weld deposit	Weld position	-----	As per requirement	-----
GTAW	P number, thickness & pipe diameter	F number, size of filler, insert, filler metal product form	Weld position	Backing gas	As per requirement	Current or polarity
PAW	P number, thickness & pipe diameter	F number, size of filler, insert, filler metal product form	Weld position	Backing gas	As per requirement	-------

 

Abbreviations

·        OFW: Oxy-fuel gas welding

·        SMAW: Shielded metal arc welding

·        GMAW: Gas metal arc welding

·        FCAW: Flux core arc welding

·        SAW: Submerged arc welding

·        GTAW: Gas tungsten arc welding

·        PAW: Plasma arc welding

 

Non-essential parameters

·        This are the parameters of welding that must include in WPS but they have not affect the mechanical properties of the weld joint.

·        If this parameters are change then need not to re-qualify the WPS, only revise the pre-qualified WPS.

·        It contains Groove design, backing, root spacing retainers etc.

Supplementary essential parameters

·        When the Supplementary essential parameters are change it affects the toughness property of the welding joint or near to welding joint that is heat affected zone.

·        It is same as per essential parameters only addition of toughness test is required in procedure qualification record. But if the client does not mention about toughness test then we does not require to re qualify the WPS.

·        It contains base metal group number, toughness limit, diameter of filler metal, classification of filler metal, PWHT toughness range etc.

·        When supplementary essential parameters are change it needs to re qualify the WPS.

 

PRE-QUALIFIED WPS

·        It is nothing but a document of WPS before its qualification.

·        It is not compulsory to develop a PWPS for each welding process but some standards like AWS D1.1 allow PWPS.

·        It is the written procedure as per codes and standards will produce a welding with correct mechanical and chemical properties.

·        In this situation PQR formation is not needed because the welding is done as per all standard parameters.

·        But if any one of the standard parameter is deviated outside the specified range during welding then PQR must be generated as a supporting document to the PWPS.