CSWIP 3.1 BOOK PDF 2015

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Cswip New Book - Ebook download as PDF File .pdf), Text File .txt) or read book online. CSWIP - Welding Inspector WIS5 () - Ebook download as PDF File .pdf), Text File .txt) or read book online. Course Note. Uploaded by. alefeli26 · CSWIP-WI 13th Edition July pdf. Uploaded by. jaisonaero. PROFESSIONAL??TWI CSWIP Welding Inspector Course WIS 5 TWI CSWIP Senior Welding Inspector Course WIS 10 DEMONSTRATED EXPERTISEDocuments. CSWIP Training Schedule - WELDING INSPECTOR LEVEL 2 - () (4 days course followed by exam) 1,16, WIS CSWIP SENIOR.


Cswip 3.1 Book Pdf 2015

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In suitable condition free from damage and contamination. WPSs Approved and available to welders and inspectors. All welder qualification certificates are valid in date. Welder qualifications Identification of welders qualified for each WPS to be used. Weld faces Free from defects. Welding equipment In suitable condition and calibrated as appropriate. A welding inspector should also ensure that any inspection aids that will be needed are: Preheat if required Minimum temperature is in accordance with WPS.

Identified and can be traced to a test certificate. Interpass temperature Maximum temperature is in accordance with WPS. PWHT if required Monitor for compliance with procedure check chart record. Welding process In accordance with WPS. Preheat if required Minimum temperature is being maintained in accordance with WPS.

Repairs Monitor in accordance with the procedure. Welding parameters Current. Weld appearance Ensure welds are suitable for all NDT profile.

Root run Visually acceptable to Code before filling the joint for single sided welds. Visually inspect welds and sentence in accordance with Code. Welding consumables In accordance with WPS and being controlled as procedure. Inter-run cleaning To good workmanship standard.

Drawings Ensure any modifications are included on as-built drawings. The form of this record will vary. When an inspection record is required it may be necessary to show that items have been checked at the specified stages and have satisfied the acceptance criteria. For individual inspection reports. ISO lists typical details for inclusion such as: Welding Inspection Personnel should: Duties of a WI Objectives When this presentation has been completed you will have a greater understanding of the requirements of a Welding inspector before.

Important qualities that good Inspectors are expected to have are: Visual examination. Other aids: Welding equipment: Weld preparations: Welding procedures: Joint A connection where the individual components. In general. Welding terms and symbols — Glossary for welding. Weld A union of pieces of metal made by welding. Brazing A process of joining generally applied to metals in which. Braze welding The joining of metals using a technique similar to fusion welding and a filler metal with a lower melting point than the parent metal.

Welding An operation in which two or more parts are united by means of heat. T Connection between the end or edge of one part and the face of the other part. Cruciform A connection in which two flat plates or two bars are welded to another flat plate at right angles and on the same axis.

Table 2. Figure 2. Autogenous weld A fusion weld made without filler metal by TIG. Slot weld A joint between two overlapping components made by depositing a fillet weld round the periphery of a hole in one component so as to join it to the surface of the other component exposed through the hole.

Two carbon steel plates welded with a matching carbon steel electrode. Plug weld A weld made by filling a hole in one component of a workpiece with filler metal so as to join it to the surface of an overlapping component exposed through the hole the hole can be circular or oval. Partial penetration weld A welded joint without full penetration. A repair weld of a cast iron item performed with a nickel-based electrode.

To reduce the stress concentration. A carbon steel lifting lug welded onto an austenitic stainless steel pressure vessel. This is a very important feature of a weld since toes are points of high stress concentration and often are initiation points for different types of cracks eg fatigue and cold cracks. Other non-standard terms for this feature are reinforcement and overfill.

Land Straight portion of a fusion face between the root face and the radius part of a J or U preparation can be 0. Its value depends on the welding process used. For single and double V or U this angle is twice the bevel angle. Its value depends on the welding process used and application. Root face The portion of a fusion face at the root that is not bevelled or grooved.

The dimensions below can vary depending on WPS.

Gap The minimum distance at any cross-section between edges. Root radius The radius of the curved portion of the fusion face in a component prepared for a single or double J or U.

For an MMA weld on carbon steel plates. Usually present in weld preparations for MIG welding of aluminium alloys.

In the case of single or double bevel. Included angle The angle between the planes of the fusion faces of parts to be welded. Single V preparation One of the most common preparations used in welding and can be produced using flame or plasma cutting cheap and fast.

For thicker plates a double V preparation is preferred since it requires less filler material to complete the joint and the residual stresses can be balanced on both sides of the joint resulting in lower angular distortion. If the root gap is zero ie if components are in contact. This asymmetric preparation allows for a balanced welding sequence with root back gouging. Included angle Angle of bevel Root face Root gap Figure 2. Whilst a single V preparation allows welding from one side.

Double V preparation The depth of preparation can be the same on both sides symmetric double V preparation or deeper on one side asymmetric double V preparation. Like for V preparations. Double U preparation Usually this type of preparation does not require a land. Single U preparation U preparations can be produced only by machining slow and expensive. Usually applied to thicker plates compared with single V preparation as it requires less filler material to complete the joint.

Permanent types are made of the same material as being joined and are tack welded in place. Backing strips can be permanent or temporary. It is also difficult to examine by NDT due to the built-in crevice at the root of the joint. The main problems with this type of weld are poor fatigue resistance and the probability of crevice corrosion between the parent metal and the backing strip.

Temporary types include copper strips. Actual throat Design throat thickness thickness Figure 2. Double preparations are recommended for thick sections. The main advantage of these preparations is that only one component is prepared cheap. For further details regarding weld preparations. As a general rule: Types of butt weld from accessibility point of view Figure 2.

Layer A stratum of weld metal consisting of one or more runs. Run pass The metal melted or deposited during one pass of an electrode.

The relation between design throat thickness and leg length is: Actual throat thickness Leg length Leg length Design throat thickness Figure 2. The cross-section area of this type of weld can be considered to be a right angle isosceles triangle with design throat thickness a and leg length z. Design throat thickness The minimum dimension of throat thickness used for design purposes. Leg length Distance from the actual or projected intersection of the fusion faces and the toe of a fillet weld.

Actual throat thickness Perpendicular distance between two lines. Since there is excess weld metal present. Convex fillet weld A fillet weld in which the weld face is convex. Due to the smooth blending between the weld face and the surrounding parent material.

The above relation between leg length and design throat thickness for mitre fillet welds is also valid for this type of weld. This is why this type of weld is highly desired in applications subjected to cyclic loads where fatigue phenomena might be a major cause for failure. The relation between leg length and design throat thickness specified for mitre fillet welds is not valid for this type of weld.

Deep penetration fillet weld A fillet weld with a deeper than normal penetration. This type of weld uses the benefits of greater arc penetration to obtain the required throat thickness whilst reducing the amount of deposited metal needed thus leading to a reduction in residual stress level.

Fillet welds added on top of the groove welds improve the blending of the weld face towards the parent metal surface and reduce the stress concentration at the toes of the weld. The relation between leg length and design throat thickness is not valid for this type of weld because the cross-section is not an isosceles triangle.

Consequently this type of weld is usually produced using mechanised or automatic welding processes. To produce consistent and constant penetration. To differentiate this type of weld from the previous types. Asymmetrical fillet weld A fillet weld in which the vertical leg length is not equal to the horizontal leg length. Horizontal leg size Vertical leg size Throat size Figure 2. Bevel Fillet weld weld Figure 2. Weld slope Angle between root line and the positive X axis of the horizontal reference plane.

Weld rotation Angle between the centreline of the weld and the positive Z axis or a line parallel to the Y axis. PF Overhead A welding position in which the welding is horizontal and overhead applicable in fillet welds. PG PG.

Vertical-down Welding position in which the welding is downwards. Welding Sketch Definition and symbol position according to ISO Flat Welding position in which the welding is horizontal with the centreline of the weld vertical.

Vertical-up Welding position in which the welding is upwards. Welding position in which the overhead welding is horizontal and overhead with the centreline of the weld horizontal. Horizontal Welding position in which the welding is horizontal. Welding position in which the vertical welding is horizontal applicable in case of fillet welds. Stringer bead A run of weld metal made with little or no weaving motion. Terminology Objective When this presentation has been completed you will have a greater understanding of typical international language used in joint design and compilation of welding documentation.

What is a Joint? Single Sided Butt Preparations Double Sided Butt Preparations Single sided preparations are normally made on thinner Double sided preparations are normally made on thicker materials.

The leg length should be approximately leg length equal to the material thickness. What is the leg length? The leg length is 14mm. What is the design throat? The design throat is 10mm. How much larger is the CSA b comparable to a?

Features to Consider Features to Consider The design throat thickness of a flat or convex fillet Importance of fillet weld leg length size weld connecting parts with the fusion faces which form an angle between and may be a b calculated by multiplying the leg length by the appropriate factors as given below: Angle between fusion Factor 4mm 8mm faces in degrees 60 to 90 0.

If the gap is too big risk of possible burn-through. Root gap set to: Complete welding on the shallow side first. Weld Preparations Weld Preparations Type of parent material impacts upon weld preparation Thickness of parent material impacts upon weld preparation To reduce distortions on stainless steels welds. Reduce weld volume by: Reduce distortions by using an asymmetric V prep Use U prep instead V prep instead of a symmetric V prep.

Cyclic load Fillet welds Double bevel weld Lack of penetration promotes cracking! Lower neutral axis is more advantageous also helps tearing. Defect An unacceptable imperfection. This standard classifies the geometric imperfections in fusion welding dividing them into six groups: These cracks can be situated in the: Cracks are more significant than other types of imperfection as their geometry produces a very large stress concentration at the crack tip making them more likely to cause fracture.

Types of crack: Crater cracks are found only in the weld metal. It is important that an imperfection is correctly identified so the cause can be established and actions taken to prevent further occurrence. Depending on their nature. In steels this is commonly created by a higher than normal content of carbon and impurity elements such as sulphur and phosphorus. Occur in the coarse grain HAZ.

These elements segregate during solidification. The cracks can be wide and open to the surface like shrinkage voids or sub- surface and possibly narrow. Solidification cracking is most likely to occur in compositions and result in a wide freezing temperature range.

19 thoughts on “What Does a Certified Welding Inspector Do?”

Occur in the weld metal usually along the centreline of the weld as a result of the solidification process. The thermal shrinkage of the cooling weld bead can cause these to rupture and form a crack. It is important that the welding fabricator does not weld on or near metal surfaces covered with scale or contaminated with oil or grease.

Hydrogen induced cracking occurs primarily in the grain coarsened region of the HAZ and is also known as cold. Scale can have a high sulphur content and oil and grease can supply both carbon and sulphur. When this happens. The direction of the principal residual tensile stress can in toe cracks cause the crack path to grow progressively away from the fusion boundary towards a region of lower sensitivity to hydrogen cracking.

Hydrogen induced cracks Figure 3. Figure 3. It lies parallel to the fusion boundary and its path is usually a combination of inter and transgranular cracking. Contamination with low melting point metals such as copper. If any one factor is not satisfied. Four factors are necessary to cause HAZ hydrogen cracking: With further strain the vertical parts of the cracking are produced.

Contraction strain imposed on the planar non-metallic inclusions results in progressive decohesion to form the roughly rectangular holes which are the horizontal parts of the cracking.

Lamellar tearing occurs only in rolled steel products primarily plates and its main distinguishing feature is that the cracking has a terraced appearance. These two stages create the terraced appearance of these cracks. Lamellar tearing Figure 3. Cracking occurs in joints where: Shrinkage cavity: Two main options are available to control the problem in welded joints liable to lamellar tearing: Gas cavities can be present in various forms: Description A gas cavity of essentially spherical shape trapped within the weld metal.

TIG Comment Porosity can be localised or finely dispersed voids throughout the weld metal. Causes Prevention Gross contaminated of preparation Introduce preweld cleaning procedures.

These can appear as a herringbone array on a radiograph and some may break the surface of the weld. Replace parent material with an unlaminated piece. Description Elongated or tubular cavities formed by trapped gas during the solidification of the weld metal which can occur singly or in groups.

Crevices in work surface due to joint Eliminate joint shapes which produce geometry. Description A gas pore that breaks the surface of the weld.

Laminated work surface. Comments Worm holes are caused by the progressive entrapment of gas between the solidifying metal crystals dendrites producing characteristic elongated pores of circular cross-section. Causes Prevention Lack of welder skill due to using Retrain welder. TIG Comments The origins of surface porosity are similar to those for uniform porosity. Description A shrinkage cavity at the end of a weld run usually caused by shrinkage during solidification.

Inoperative crater filler slope out Use correct crater filling techniques. To fill the crater for this process it is necessary to reduce the weld current slope out in a series of descending steps until the arc is extinguished.

Comments Crater filling is a particular problem in TIG welding due to its low heat input. Causes Prevention Incomplete slag removal from underlying Improve inter-run slag removal surface of multi-pass weld Slag flooding ahead of arc Position work to gain control of slag.

Description Slag trapped during welding which is an irregular shape so differs in appearance from a gas pore. Appear only in flux associated welding processes ie MMA. These only become a problem when large or sharp-edged inclusions are produced. Gross oxide film enfoldment can occur due to a combination of unsatisfactory protection from atmospheric contamination and turbulence in the weld pool. Comments A fine dispersion of inclusions may be present within the weld metal.

Causes Prevention Contact of electrode tip with weld pool Keep tungsten out of weld pool. Lack of fusion Lack of Lack of inter. Lack of union between the weld and parent metal at one or both sides of the weld. Course outline cswip 3. Lack of fusion between the weld and parent metal at the root of a weld. Lack of root fusion Figure 3. Lack of union along the fusion line between the weld beads. Causes Prevention Low arc current resulting in low fluidity of Increase current weld pool Too high a travel speed Reduce travel speed Inaccurate bead placement Retrain welder Lack of inter-run fusion produces crevices between the weld beads and causes local entrapment of slag.

The difference between actual and nominal penetration. Causes Prevention Excessively thick root face. An irregular groove at the toe of a run in the parent metal or previously deposited weld metal due to welding. Characterised by its depth. If the weld joint is not of a critical nature.

Incomplete root penetration Figure 3. When examined from the root side. Causes and prevention Same as for lack of root fusion. Both fusion faces of the root are not melted. In this case incomplete root penetration is considered part of this structure and not an imperfection This would normally be determined by the design or code requirement. Undercut Continuous Intermittent Inter-run undercut undercut undercut Causes Prevention Melting of top edge due to high welding Reduce power input.

If the bead of a repair weld is too small. SAW Note DC-ve must be used for TIG The term reinforcement used to designate this feature of the weld is misleading since the excess metal does not normally produce a stronger weld in a butt joint in ordinary steel. Excess weld metal is the extra metal that produces excessive convexity in fillet welds and a weld thickness greater than the parent metal plate in butt welds. It is regarded as an imperfection only when the height of the excess weld metal is greater than a specified limit.

This imperfection can become a problem. Projection of the root penetration bead beyond a specified limit. Permanent or temporary backing bars can assist in the control of penetration.

Imperfection at the toe of a weld caused by metal flowing on to the surface of the parent metal without fusing to it. This can be made more difficult if there is restricted access to the weld or a narrow preparation. For a fillet weld overlap is often associated with undercut.

Causes Prevention Inaccuracies in assembly procedures or Adequate checking of alignment prior to distortion from other welds welding coupled with the use of clamps and wedges Excessive out of flatness in hot rolled Check accuracy of rolled section prior to plates or sections welding Misalignment is not a weld imperfection but a structural preparation problem.

Misalignment between two welded pieces such that while their surface planes are parallel. Even a small amount of misalignment can drastically increase the local shear stress at a joint and induce bending stress.

Non-Destructive Testing

If the volume of the weld pool is too large in a fillet weld in horizontal-vertical PB position. Causes and prevention are the same as for linear misalignment. Causes Prevention Insufficient weld metal Increase the number of weld runs Irregular weld bead surface Retrain welder This imperfection differs from undercut. Misalignment between two welded pieces such that their surface planes are not parallel or at the intended angle. Continuous or intermittent channel in the weld surface due to insufficient deposition of weld filler metal.

Excessive variation in width of the weld. Causes Prevention Insufficient travel speed Increase the travel speed Excessive welding current Reduce welding current Lack of welder skill Retrain welder Excessive grinding of root face More care taken. A shallow groove that occurs due to shrinkage at the root of a butt weld. A collapse of the weld pool resulting in a hole in the weld. Local damage to the surface of the parent metal adjacent to the weld. This results in random areas of fused metal where the electrode.

This is a gross imperfection which occurs due to lack of welder skill but can be repaired by bridging the gap formed into the joint. Causes Prevention Poor access to the work Improve access modify assembly sequence Missing insulation on electrode holder Institute a regular inspection scheme or torch for electrode holders and torches Failure to provide an insulated resting Provide an insulated resting place place for the electrode holder or torch when not in use Loose current return clamp Regularly maintain current return clamps Adjusting wire feed MAG welding Retrain welder without isolating welding current An arc strike can produce a hard HAZ which may contain cracks.

It is better to remove an arc strike by grinding than weld repair. However as it is usually caused by an excessive welding current. Some spatter is always produced by open arc consumable electrode welding processes. Globules of weld or filler metal expelled during welding adhering to the surface of parent metal or solidified weld metal. Anti-spatter compounds can be used on the parent metal to reduce sticking and the spatter can then be scraped off.

Damp electrodes Use dry electrodes Wrong selection of shielding gas Increase argon content if possible. Misalignment of opposite runs Difference between the centrelines of two runs made from opposite sides of the joint. Prior to service of a welded joint.

Chipping mark Local damage due to the use of a chisel or other tools. The area should be ground off. Underflushing Lack of thickness of the workpiece due to excessive grinding.

Temper colour visible oxide film Lightly oxidised surface in the weld zone. Some applications do not allow the presence of any overlay weld on the surface of the parent material. In exceptional circumstances and subject to the agreement of all parties. Replacing removed metal or weld repair as in filling an excavation or re- making a weld joint has to be done in accordance with an approved procedure.

If the weld imperfection is at the surface. Once unacceptable weld imperfections have been found they have to be removed. The rigour with which this procedure is qualified depends on the application standard for the job. All normal weld imperfection acceptance standards totally reject cracks.

If the level of reassurance required is higher. Superficial implies that after removal of the defect the remaining material thickness is sufficient not to require the addition of further weld metal. The acceptance of a certain size and type of defect for a given structure is normally expressed as the defect acceptance standard.

It is important to note that the levels of acceptability vary between different applications and in most cases vary between different standards for the same application.

This can be difficult to establish and usually involves fracture mechanics measurements and calculations. In some cases it will be acceptable to use a procedure qualified for making new joints whether filling an excavation or making a complete joint. If the defect is too deep it must be removed and new weld metal added to ensure a minimum design throat thickness. In either case. You should be able to asses the defect against an acceptance Welding Imperfections and criteria and accept or reject accordingly.

Misplaced welds. Causes b. Excessively thick root face. Welding Imperfections Objective When this presentation has been completed you will have a greater understanding of the types of defects during visual inspection. Too small a root gap. Lack of sidewall fusion due to arc deflection. Welding Defects Welding Defects Too large diameter d. Arc heat input too low. Smaller correct e. Power input too low.

Hi low. Angular misalignment measured in mm. Any Questions? Test specimens A transverse tensile test piece typical of the type specified by European Welding Standards is shown below. The tests are called destructive tests because the welded joint is destroyed when various types of test piece are taken from it.

Qualitative tests are used to verify that the joint is free from defects. Mechanical tests are quantitative because a quantity is measured. The emphasis in the following sub-sections is on the destructive tests and test methods widely used for welded joints. Destructive tests can be divided into two groups. The quantitative mechanical tests carried out for welding procedure qualification are intended to demonstrate that the joint properties satisfy design requirements.

Design engineers use the minimum property values listed for particular grades of material as the basis for design and the most cost-effective designs are based on an assumption that welded joints have properties that are no worse than those of the base metal. All-weld tensile tests are regularly carried out by welding consumable manufacturers to verify that electrodes and filler wires satisfy the tensile properties specified by the standard to which the consumables are certified.

The test is to measure tensile strength and also yield or proof strength and tensile ductility. Test pieces may be machined to represent the full thickness of the joint but for very thick joints it may be necessary to take several transverse tensile test specimens to be able to test the full thickness.

The tensile strength Rm is calculated by dividing the maximum load by the cross-sectional area of the test specimen. Method Test specimens are accurately measured before testing. Parallel length Figure 4. The test is intended to measure the tensile strength of the joint and thereby show that the basis for design. Acceptance criteria If the test piece breaks in the weld metal. Figure 4. Method Specimens are subjected to a continually increasing force in the same way that transverse tensile specimens are tested.

Typical load extension curves and their principal characteristics are shown below. Yield Re or proof stress Rp are measured by an extensometer attached to the parallel length of the specimen that accurately measures the extension of the gauge length as the load is increased. Round tensile specimen from a Round tensile specimen from an welding procedure qualification electrode classification test piece.

To calculate elongation: The figure below illustrates these two ductility measurements. Load extension curve for a steel Load-extension curve for a steel or that shows a distinct yield point at other metal that does not show a the elastic limit.

The term necking is often used to describe reduction in diameter. Tensile ductility is measured in two ways: There are also standard dimensions for smaller sized specimens. Specimens Test specimen dimensions have been standardised internationally and are shown below for full size specimens. The transition temperature is defined as the temperature midway between the upper shelf maximum toughness and lower shelf completely brittle.

Degrees Centigrade Three specimens are normally tested at each temperature Figure 4. Design engineers need to ensure that the toughness of the steel used for a particular item will be sufficient to avoid brittle fracture in service and so impact specimens are tested at a temperature related to the design temperature for the fabricated component. C-Mn and low alloy steels undergo a sharp change in their resistance to brittle fracture as their temperature is lowered so that a steel that may have very good toughness at ambient temperature may show extreme brittleness at sub- zero temperatures.

Method Test specimens are cooled to the specified test temperature by immersion in an insulated bath containing a liquid held at the test temperature. After allowing the specimen temperature to stabilise for a few minutes it is quickly transferred to the anvil of the test machine and a pendulum hammer quickly released so that the specimen experiences an impact load behind the notch.

The main features of an impact test machine are shown below. Impact specimen on the anvil showing the hammer position at point of impact. Specimens are machined from welded test plates with the notch position located in different positions according to the testing requirements but typically in the centre of the weld metal and at positions across the HAZ.

Increase in width of the back of the specimen behind the notch. After impact testing. Acceptance criteria Each test result is recorded and an average value calculated for each set of three tests. Energy values are given in Joules or ft-lbs in US specifications.

The imperfection is of an irregular shape and thus differs in appearance from a gas pore. Adjust welding parameters ie current, voltage etc to produce satisfactory welding conditions Oxide inclusions Description Oxides trapped during welding. This type of defect occurs especially in the case of aluminium alloys. Gross oxide film enfoldment can occur due to a combination of unsatisfactory protection from atmospheric contamination and turbulence in the weld pool.

Lack of fusion Lack of sidewall fusion 5. Causes Low arc current resulting in low fluidity of weld pool Too high a travel speed Inaccurate bead placement Prevention Increase current Reduce travel speed Retrain welder Comments Lack of inter-run fusion produces crevices between the weld beads and causes local entrapment of slag.

Causes Low heat input Excessive inductance in MAG dip transfer welding, MMA electrode too large low current density Use of vertical down welding Large root face Small root gap Incorrect angle or incorrect electrode manipulation Excessive misalignment at root 5.

In this case incomplete root penetration is considered part of this structure and is not an imperfection this would normally be determined by the design or code requirement. When examined from the root side, you can clearly see one or both of the root edges unmelted. Causes and prevention Same as for lack of root fusion.

It is characterised by its depth, length and sharpness. If the bead of a repair weld is too small, the cooling rate following welding will be excessive and the parent metal may have an increased hardness and the weld may be susceptible to hydrogen cracking.

This feature of a weld is regarded as an imperfection only when the height of the excess weld metal is greater than a specified limit. This imperfection can become a problem, as the angle of the weld toe can be sharp, leading to an increased stress concentration at the toes of the weld and fatigue cracking.

This can be made more difficult if there is restricted access to the weld or a narrow preparation. Permanent or temporary backing bars can be used to assist in the control of penetration. Change to flat position Change electrode coating type to a more suitable fast freezing type which is less fluid Comments For a fillet weld overlap is often associated with undercut, as if the weld pool is too fluid the top of the weld will flow away to produce undercut at the top and overlap at the base.

Causes Prevention Inaccuracies in assembly Adequate checking of alignment prior procedures or distortion from to welding coupled with the use of other welds clamps and wedges Excessive out of flatness in hot Check accuracy of rolled section prior rolled plates or sections to welding Comments Misalignment is not really a weld imperfection, but a structural preparation problem.

Even a small amount of misalignment can drastically increase the local shear stress at a joint and induce bending stress.

Causes and prevention Same as for linear misalignment. Causes Insufficient weld metal Irregular weld bead surface Prevention Increase the number of weld runs Retrain welder Comments This imperfection differs from undercut, it reduces the load-bearing capacity of a weld, whereas undercut produces a sharp stress-raising notch at the edge of a weld.

Causes Severe arc blow Irregular weld bead surface Prevention Switch from DC to AC, keep as short as possible arc length Retrain welder Comments Although this imperfection may not affect the integrity of completed weld, it can affect the width of HAZ and reduce the load-carrying capacity of the joint in the case of fine-grained structural steels or impair corrosion resistance in the case of duplex stainless steels.

Causes Insufficient travel speed Excessive welding current Lack of welder skill Excessive grinding of root face Excessive root gap Prevention Increase the travel speed Reduce welding current Retrain welder More care taken, retrain welder Ensure correct fit-up Comments This is a gross imperfection, which occurs basically due to lack of welder skill.

It can be repaired by bridging the gap formed into the joint, but requires a great deal of attention. This results in random areas of fused metal where the electrode, holder, or current return clamp have accidentally touched the work.

Causes Poor access to the work Prevention Improve access modify assembly sequence Missing insulation on electrode Institute a regular inspection scheme for holder or torch electrode holders and torches Failure to provide an insulated Provide an insulated resting place resting place for the electrode holder or torch when not in use Loose current return clamp Regularly maintain current return clamps Adjusting wire feed MAG Retrain welder welding without isolating welding current Comments An arc strike can produce a hard HAZ, which may contain cracks.

These can lead to serious cracking in service. It is better to remove an arc strike by grinding than weld repair. However as it is usually caused by an excessive welding current, it is a sign that the welding conditions are not ideal and so there are usually other associated problems within the structure ie high heat input. Note that some spatter is always produced by open arc consumable electrode welding processes.

Anti-spatter compounds can be used on the parent metal to reduce sticking and the spatter can then be scraped off. The area should be ground off, then subjected to a dye penetrant or magnetic particle examination and then restored to its original shape by welding using a qualified procedure. Some applications do not allow the presence of any overlay weld on the surface of the parent material. Chipping mark Description Local damage due to the use of a chisel or other tools.

Underflushing Description Lack of thickness of the workpiece due to excessive grinding. Misalignment of opposite runs Description Difference between the centrelines of two runs made from opposite sides of the joint. Temper colour visible oxide film Description Lightly oxidised surface in the weld zone, usually occurs in stainless steels. Therefore, prior to service of a welded joint, it is necessary to locate them using NDE techniques, assess their significance, and take action to avoid their reoccurrence.

The acceptance of a certain size and type of defect for a given structure is normally expressed as the defect acceptance standard.

This is usually incorporated in application standards or specifications. All normal weld imperfection acceptance standards totally reject cracks. However, in exceptional circumstances, and subject to the agreement of all parties, cracks may be allowed to remain if it can be demonstrated beyond doubt that they will not lead to failure. This can be difficult to establish and usually involves fracture mechanics measurements and calculations.

It is important to note that the levels of acceptability vary between different applications, and in most cases vary between different standards for the same application. Consequently, when inspecting different jobs it is important to use the applicable standard or specification quoted in the contract. Once unacceptable weld imperfections have been found, they have to be removed.

If the weld imperfection is at the surface, the first consideration is whether it is of a type, which is normally shallow enough to be repaired by superficial dressing. Superficial implies that, after removal of the defect, the remaining material thickness is sufficient not to require the addition of further weld metal.

If the defect is too deep, it must be removed and new weld metal added to ensure a minimum design throat thickness. Replacing removed metal or weld repair as in filling an excavation or remaking a weld joint has to be done in accordance with an approved procedure. The rigour with which this procedure is qualified will depend on the application standard for the job.

In some cases it will be acceptable to use a procedure qualified for making new joints whether filling an excavation or making a complete joint. If the level of reassurance required is higher, the qualification will have to be made using an exact simulation of a welded joint, which is excavated and then refilled using a specified method. In either case, qualification inspection and testing will be required in accordance with the application standard.

The tests are called destructive tests because the welded joint is destroyed when various types of test piece are taken from it.

Destructive tests can be divided into two groups: Qualitative tests are used to verify that the joint is free from defects — they are of sound quality and examples of these are bend tests, macroscopic examination and fracture tests fillet fracture and nick-break.

Cswip 3.1 exam questions and answers pdf

Design engineers use the minimum property values listed for particular grades of material as the basis for design and the most cost-effective designs are based on an assumption that welded joints have properties that are no worse than those of the base metal. The quantitative mechanical tests carried out for welding procedure qualification are intended to demonstrate that the joint properties satisfy design requirements.

The emphasis in the following sub-sections is on the destructive tests and test methods that are widely used for welded joints.

Test specimens A transverse tensile test piece typical of the type specified by European Welding Standards is shown below. Standards, such as EN , that specify dimensions for transverse tensile test pieces require all excess weld metal to be removed and the surface to be free from scratches. Parallel length Test pieces may be machined to represent the full thickness of the joint but for very thick joints it may be necessary to take several transverse tensile test specimens to be able to test the full thickness.

Test method Test specimens are accurately measured before testing. Specimens are then fitted into the jaws of a tensile testing machine and subjected to a continually increasing tensile force until the specimen fractures.

The tensile strength Rm is calculated by dividing the maximum load by the cross-sectional area of the test specimen - measured before testing.

The test is intended to measure the tensile strength of the joint and thereby show that the basis for design, the base metal properties, remains the valid criterion. Acceptance criteria If the test piece breaks in the weld metal, it is acceptable provided the calculated strength is not less than the minimum tensile strength specified, which is usually the minimum specified for the base metal material grade.

The test is carried out in order to measure tensile strength and also yield or proof strength and tensile ductility. All-weld tensile tests are also regularly carried out by welding consumable manufacturers to verify that electrodes and filler wires satisfy the tensile properties specified by the standard to which the consumables are certified.

Yield Re or proof stress Rp are measured by means of an extensometer that is attached to the parallel length of the specimen and is able to accurately measure the extension of the gauge length as the load is increased. Typical load extension curves and their principal characteristics are shown below.

Load extension curve for a steel that shows a distinct yield point at the elastic limit Load-extension curve for a steel or other metal that does not show a distinct yield point; proof stress is a measure of the elastic limit Tensile ductility is measured in two ways: Design engineers need to ensure that the toughness of the steel used for a particular item will be high enough to avoid brittle fracture in service and so impact specimens are tested at a temperature that is related to the design temperature for the fabricated component.

C-Mn and low alloy steels undergo a sharp change in their resistance to brittle fracture as their temperature is lowered so that a steel that may have very good toughness at ambient temperature may show extreme brittleness at sub-zero temperatures — as illustrated in following figure.

Test specimens The dimensions for test specimens have been standardised internationally and are shown below for full sized specimens.

There are also standard dimensions for smaller sized specimens, for example 10x7. Typical notch positions for Charpy V notch test specimens from double V butt welds Test method Test specimens are cooled to the specified test temperature by immersion in an insulated bath containing a liquid that is held at the test temperature. After allowing the specimen temperature to stabilise for a few minutes it is quickly transferred to the anvil of the test machine and a pendulum hammer quickly released so that the specimen experiences an impact load behind the notch.

Impact testing machine Impact specimen on the anvil showing the hammer position at point of impact. Charpy V notch test pieces before and after testing The energy absorbed by the hammer when it strikes each test specimen is shown by the position of the hammer pointer on the scale of the machine. Energy values are given in Joules or ft-lbs in US specifications. Acceptance criteria Each test result is recorded and an average value calculated for each set of three tests. These values are compared with those specified by the application standard or client to establish whether specified requirements have been met.

After impact testing, examination of the test specimens provides additional information about their toughness characteristics and may be added to the test report: A specimen that exhibits very good toughness will show only a small degree of crack extension, without fracture and a high value of lateral expansion.

This is determined by measuring the resistance to indentation by a particular type of indenter. Specimens prepared for macroscopic examination can also be used for taking hardness measurements at various positions of the weldment referred to as a hardness survey. Test methods There are three widely used methods for hardness testing: Rockwell hardness test - uses a diamond cone indenter or steel ball. Brinell hardness test - uses a ball indenter.

The hardness value being given by the size of the indentation produced under a standard load, the smaller the indentation, the harder the metal. A typical hardness survey requires the indenter to measure the hardness in the base metal on both sides of the weld , the weld metal and across the HAZ on both sides of the weld. The Brinell method gives an indentation that is too large to accurately measure the hardness in specific regions of the HAZ and is mainly used to measure hardness of base metals.

Hardness values are shown on test reports as a number followed by letters indicating the test method, for example: Fracture toughness data enables engineers to carry out fracture mechanics analyses such as: Test specimens A CTOD specimen is prepared as a rectangular or square shaped bar cut transverse to the axis of the butt weld.

A V notch is machined at the centre of the bar, which will be coincident with the test position - weld metal or HAZ. A shallow saw cut is made at the bottom of the notch and the specimen is then put into a machine that induces a cyclic bending load until a shallow fatigue crack initiates from the saw cut. The test piece details are shown below. Test method CTOD specimens are usually tested at a temperature below ambient and the specimen temperature is controlled by immersion in a bath of liquid that has been cooled to the required test temperature.

A load is applied to the specimen to cause bending and induce a concentrated stress at the tip of the crack and a clip gauge, attached to the specimen across the mouth of the machined notch, gives a reading of the increase in width of the crack mouth as the load is gradually increased.

For each test condition position of notch and test temperature it is usual practice to carry out three tests. Fracture toughness is expressed as the distance the crack tip opens without initiation of a brittle crack. The clip gauge enables a chart to be generated showing the increase in width of the crack mouth against applied load from which a CTOD value is calculated.

Acceptance criteria An application standard or client may specify a minimum CTOD value that indicates ductile tearing. Alternatively, the test may be for information so that a value can be used for an engineering critical assessment.

A very tough steel weldment will allow the mouth of the crack to open widely by ductile tearing at the tip of the crack whereas a very brittle weldment will tend to fracture when the applied load is quite low and without any extension at the tip of the crack.

Subjecting specimens to bending is a simple method of verifying there are no significant flaws in the joint. Some degree of ductility is also demonstrated. Ductility is not actually measured but it is demonstrated to be satisfactory if test specimens can withstand being bent without fracture or fissures above a certain length. Test specimens There are four types of bend specimen: Longitudinal bend: The diameter of the former used for a particular test is specified in the code, having been determined by the type of material being tested and the ductility that can be expected from it after welding and any post weld heat treatment PWHT.

The diameter of the former is usually expressed as a multiple of the specimen thickness t and for C-Mn steel it is typically 4t but for materials that have lower tensile ductility the radius of the former may be greater than 10t. The standard that specifies the test method will specify the minimum bend angle that the specimen must experience and this is typically Acceptance criteria Bend tests pieces should exhibit satisfactory soundness by not showing cracks or any signs of significant fissures or cavities on the outside of the bend.

This method for assessing the quality of fillet welds may be specified by application standards as an alternative to macroscopic examination. It is a test method that can be used for welder qualification testing according to European Standards but is not used for welding procedure qualification.

The notch profile may be square, V or U shape. Test method Specimens are made to fracture through their throat by dynamic strokes hammering or by pressing, as shown below. The welding standard or application standard will specify the number of tests typically four. Test reports should also give a description of the appearance of the fracture and location of any imperfection 2. These tests are specified for welder qualification testing to European Standards as an alternative to radiography.

They are not used for welding procedure qualification testing. Test specimens Test specimens are taken from a butt weld and notched so that the fracture path will be in the central region of the weld.

Typical test piece types are shown below. Test method Test pieces are made to fracture by hammering or three-point bending. Acceptance criteria The standard for welder qualification, or application standard, will specify the acceptance criteria for imperfections such as lack of fusion, solid inclusions and porosity that are visible on the fracture surfaces.

Test reports should also give a description of the appearance of the fracture and location of any imperfection. This is considered in detail in a separate section of these course notes. EN Destructive tests on welds in metallic materials — Impact tests — test specimen location, notch orientation and examination. EN Destructive tests on welds in metallic materials — transverse tensile test. EN Destructive tests on welds in metallic materials — bend tests.

EN Destructive tests on welds in metallic materials — macroscopic and microscopic examination of welds. Part 1: Method of test at ambient temperature. BS EN Tensile testing of metallic materials. Part 5: Method of test at elevated temperatures.

The relative advantages and limitations of the methods are discussed in terms of their applicability to the examination of welds. The transmitted radiation is collected by some form of sensor, which is capable of measuring the relative intensities of penetrating radiations impinging upon it. In most cases this sensor will be radiographic film, however the use of various electronic devices is on the increase. These devices facilitate so-called real-time radiography and examples may be seen in the security check area at airports.

Digital technology has enabled the storing of radiographs using computers. The present discussion is confined to film radiography since this is still by far the most common method applied to welds. Other forms of penetrating radiation exist but they are of limited interest in weld radiography. Up to keV they are generated by conventional X-ray tubes which, dependant upon output, may be suitable for portable or fixed installations.

Portability falls off rapidly with increasing kilovoltage and radiation output. Above keV X-rays are produced using devices such as betatrons and linear accelerators, not generally suitable for use outside of fixed installations. All sources of X-rays produce a continuous spectrum of radiation, reflecting the spread of kinetic energies of electrons within the electron beam.

Low energy radiations are more easily absorbed and the presence of low energy radiations, within the X-ray beam, gives rise to better radiographic contrast and therefore better radiographic sensitivity than is the case with gamma-rays which are discussed below. Conventional X-ray units are capable of performing high quality radiography on steel of up to 60mm thick, betatrons and linear accelerators in excess of mm.

The activity of these sources was not very high, therefore they were physically rather large by modern standards even for quite modest outputs of radiation and the radiographs produced by them were not of a particularly high standard.

CSWIP 3.2 Study Materials

Radium sources were also extremely hazardous to the user due to the production of radioactive radon gas as a product of the fission reaction. Since the advent of the nuclear age it has been possible to artificially produce isotopes of much higher specific activity than those occurring naturally and which do not produce hazardous fission products.

Unlike the X-ray sources gamma-sources do not produce a continuous distribution of quantum energies. Gamma-sources produce a number of specific quantum energies which are unique for any particular isotope. Four isotopes are in common use for the radiography of welds, they are in ascending order of radiation energy: Thulium 90, Ytterbium , Iridium and Cobalt Cobalt 60 has an energy approximating to that of 1. Cobalt 60 sources are for this reason not fully portable.

They are useful for the radiography of steel in the thickness range mm. The major advantages of using isotopic sources over X-rays are: Against this the quality of radiographs produced by gamma-ray techniques is inferior to that produced by X-ray techniques, the hazards to personnel may be increased if the equipment is not properly maintained, or if the operating personnel have insufficient training , and due to their limited useful lifespan new isotopes have to be downloadd on a regular basis so that the operating costs of an gamma-ray source may exceed those of an X-ray source.

Volumetric weld defects such as slag inclusions except in some special cases where the slag absorbs radiation to a greater extent than does the weld metal and various forms of gas porosity are easily detected by radiographic techniques due to the large negative absorption difference between the parent metal and the slag or gas. Planar defects such as cracks or lack of sidewall or interun fusion are much less likely to be detected by radiography since they may cause little or no change in the penetrated thickness.

Where defects of this type are likely to occur other NDE techniques such as ultrasonic testing are preferable to radiography. This lack of sensitivity to planar defects makes radiography an unsuitable technique where a fitness-for-purpose approach is taken when assessing the acceptability of a weld. X-ray equipment. Safety Important Classified workers, medicals required Sensitive to defect orientation Not good for planar defect detection Limited ability to detect fine cracks Access to both sides required Skilled interpretation required Relatively slow High capital outlay and running costs Isotopes have a half life cost When ultrasonic waves pass from a given material with a given sound velocity to a second material with different velocity refraction, and a reflection of the sound beam will occur at the boundary between the two materials.

The same laws of physics apply equally to ultrasonic waves as they do to light waves. Ultrasonic waves are refracted at a boundary between two materials having different acoustic properties, so probes may be constructed which can beam sound into a material at within certain limits any given angle. Because sound is reflected at a boundary between two materials having different acoustic properties ultrasound is a useful tool for the detection of weld defects.

Since velocity is a constant for any given material and sound travels in a straight line with the right equipment ultrasound can also be utilised to give accurate positional information about a given reflector. Automated or semi-automated systems for ultrasonic testing utilise the same basic equipment although since in general this will be multi-channel equipment it is bulkier and less portable. Probes for automated systems are set in arrays and some form of manipulator is necessary to feed positional information about the probes to the computer.

Automated systems generate very large amounts of data and make large demands upon the RAM of the computer. Recent advances in automated UT have led to a reduced amount of data being recorded for a given length of weld.

Simplified probe arrays have greatly reduced the complexity of setting-up the automated system to carry out a particular task. Automated UT systems now provide a serious alternative to radiography on such constructions as pipelines where a large number of similar inspections allow the unit cost of system development to be reduced to a competitive level. Ultrasonic equipment. Compression and a shear wave probe.

Typical screen display when using a shear wave probe. These leakage fields will attract magnetic particles finely divided magnetite to themselves and this leads to the formation of an indication. The magnetic particles may be visibly or fluorescently pigmented in order to provide contrast with the substrate or conversely the substrate may be lightly coated with a white background lacquer in order to contrast with the particles.

Fluorescent magnetic particles provide the greatest sensitivity. The particles will normally be in a liquid suspension, usually applied by spraying. In certain cases dry particles may be applied by a gentle jet of air. The leakage field will be greatest for linear discontinuities lying at right angles to the magnetic field.

This means that for a comprehensive test the magnetic field must normally be applied in two directions, which are mutually perpendicular. The test is economical to carry out both in terms of equipment costs and rapidity of inspection. The level of operator training required is relatively low. Magnetic particle inspection using a yoke. Crack found using magnetic particle inspection. Penetrants are attracted into surface-breaking discontinuities by capillary forces.

Penetrant, which has entered a tight discontinuity, will remain even when the excess penetrant is removed. Application of a suitable developer will encourage the penetrant within such discontinuities to bleed out. If there is a suitable contrast between the penetrant and the developer an indication visible to the eye will be formed. This contrast may be provided by either visible or fluorescent dyes. Use of fluorescent dyes considerably increases the sensitivity of the technique.

Methods of applying the red dye during dye penetrant inspection. Crack found using dye penetrant inspection. You just clipped your first slide! Clipping is a handy way to collect important slides you want to go back to later. Now customize the name of a clipboard to store your clips. Visibility Others can see my Clipboard. Cancel Save.Temper colour visible oxide film Description Lightly oxidised surface in the weld zone. Baking of cored wires is ineffective and will do nothing to restore the condition of a contaminated flux within a wire.

Lack of fusion between the weld and parent metal at the root of a weld. Type of current AC only qualifies for AC. An alternative method is to use a symbolic representation to specify the required information — as shown below for the same joint detail.

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