CSWIP 3.2.2 Questions

CSWIP 3.2 THEORY PAPER Q&A

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1. Signing off a product

In an engineering fabrication industry the last activity in the sequence of manufacturing is load out or

dispatch. This activity cannot be initiated unless the product is signed off. As a matter of fact signing

the product off is assurance of quality which is authenticated by a technically competent person such

as “Senior Welding Inspector” who makes sure that complete manufacturing of product has been

carried out in accordance with applicable standard and sound engineering practices.

However before signing the documents the senior welding inspector should make enquiry which can

give him the in sites of the past while product was being manufactured.

Typical questions can be as followed

1. What was the repair rate during production?

2. Whether any difficulties are encountered within the job?

3. Which is the critical area in this job or product?

4. Whether any concession or waiver were given, if yes why?

5. How were the weather conditions?

6. Whether there were any safety issues, fatalities, major accidents/incident etc…?

7. Whether there were any labour problems?

8. What was the general moral and standard of work amongst the inspection team(s)?

Further to this he can start reviewing of documents and he should make sure that he attaches the

following documents as a minimum

1. Quality control plan – ensure all stages are completed and signed off

2. Inspection check list – ensure all stages are completed and signed off

3. Verify material certificates such as mill test certificates; material traceability records lap

reports etc…

4. Verify the following procedures which are to be attached and have all been approved

a. Welding

b. Repair

c. NDT

d. PWHT

e. Hardness

f. PMI

g. Hydrotest

h. Coating/Painting

5. Verify the qualification level and validity of the welder and NDT personnel

6. Verify the inspection reports of following disciplines and ensure that they cover all

appropriate joints and structure

a. Visual

b. NDT

c. Dimensional control etc…

7. Verify calibration certificates of equipments and instruments such as pressure gauge,

inspection tools and welding equipments etc…

8. Verify hardness test reports

9. Verify PMI reports

10. Verify PWHT reports and charts

11. Verify Hydro test reports and charts

12. Verify painting and coating inspection reports

13. Verify as built drawings are completed

14. Verify weld maps are available for traceability

15. Verify name plate, rubbing details are available when applicable

16. Verify concession request, NCR, site query etc…

17. Verify permit to work

As a part of his own inspection he may be obliged to witness final hydrotest, visual inspection of

completed parts. As a matter of quality assurance he may view some radiographs at random and may

even conduct radiograph audit.

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Finally, transit and tie down procedures should all have been approved by the relevant engineer prior

to the final acceptance of the product and issue of any signed certificate of conformance.

2. Duties of the Senior Welding Inspector

Plan

It is an agreed pre-determined structural path way that needs specific aim. All projects inspection

needs the following planning.

a. Establishing inspection test plan and plan for all stages of inspection

b. Establish requires WPS and PQR

c. Plan for requires resources. I.e. manpower, inspection tools, etc.,

d. Developing quality control procedures

e. Plan the work schedule i.e. type of inspection and at what times.

f. Communication with superior and others.

Organize

To make all necessary arrangement required to carry out or fulfil plan, this may involve the

following.

a. Any training and certification required.

b. Staffing plan i.e. assigning work and area to inspectors

c. Procurement of inspection equipment and its calibration

d. Transportation to and fro from site

e. Accommodation and messing

f. Inspectors leave cycle

Supervise

Once the plan has been organized it is essential that controls are exercised so that the plan is

successfully implemented

a. Supervise and evaluate inspectors work.

b. Check inspection equipment condition

c. Organize the inspection activities to be completed in time

d. Take effective decision for solving quality related problems

e. Share your knowledge with technical discussion with all inspectors

f. Motivate the staff to meet standard of quality

g. Communicate with other department to improve procedure, investigate and advice on quality

problems.

h. Keep a record of day to day inspection activates and pending inspection to be completed

i. Supervise to maintain ISO related documents.

Auditing

To carry out a periodic and systematic check on a system process to ensure that it has been carried

out as specified

Staff

a. All staff to be internal audited to ensure that they are maintaining all documents as per ITP

b. Whether all ISO related documents are maintained

c. Whether all welder details are up to date

Equipment

a. Inspection tools to be checked for calibration and condition

b. Welding machine over calibration and condition

Documentation

a. Check all inspection documents are maintained as per procedure

b. Check all NDT records



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c. Check welder qualification record

d. Randomly interpret Radiographic for all personals.

3. Describe and sketch the following defects lamination, laps, bands and their differences

Lamination

Laminations are planes within the steel plate across (through thickness) which there is no metallic

bond (separated in layers). They are typically a result of non-metallic inclusions and gas pockets

formed in the ingot when it has been cast and as it solidifies.

In the steel mill the molten steel poured in moulds to form ingots. While solidification is taking place

huge amount of gases are released. It is quite possible that some of these gases and non-metallic

inclusions such as oxide coating of the bubbles, slag inclusions, refractory inclusions from erosion of

the furnace may remain trapped in the solidified steel. This ingot when rolled the gas pocket and

inclusions inside get flattened in the forms of lamination.

This discontinuity adversely affects through thickness strength of steel and is not traceable by MPI or

RT. The only way to detect lamination is UT. This discontinuity may also contribute to lamellar tear

in thicker section.

Laps

Laps are basically chunk of metal that has flown from the desired profile during operations such as

rolling and hot forming. This chunk of material is connected to the base metal at some locations and

overhanging portion of the chunk simply lies on the metal without being the homogeneous part of it.

As it is surface defect it can be found visually and can be confirmed by MPI.

Differences: lamination is a sub-surface defect lap is a surface defect. Lap can be found in visual

inspection and confirm by MPI. Lamination can be confirmed by ultrasonic test only.

Bands

As the ingot is forged and rolled the segregation are elongated and reduced in cross section. If further

processing is carried out, they may appear as very thin parallel lines of bands and is generally known

as banding. Banding is not usually significant.

4. It has come to your attention that the morale of your inspection team appears to be low,

a. What could you have observed to determine this?

b. What would occur if this was not rectified quickly?

c. What could you do to lift low morale?

Low morale can be identified by the following symptoms

1. lack of diligence

2. taking short cuts

3. ignoring safety procedures

4. not starting work promptly

5. taking long breaks

6. talking in groups and grumbling about minor matters

7. higher levels of absenteeism

8. Negligence (poor record keeping, not inspecting the weld etc...)

9. complaints from TPI/Client

Low morale may be result in the following

1. lack of control over production activities from quality point of view

2. poor productivity

3. substandard work output

4. delay in work schedule

5. lack of credibility to the organization

Observing all above, it is imperative that lifting the low morale this can be done as follows



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1. Arrange the meeting of entire sub coordinates staff for discussion on the subject matter.

2. From their response I can form a collective opinion for low morale

3. Further to this I may have private discussion with each individual which can help me to zero

in on his problems.

4. This problem is then sorted out as general problem and individual problems.

5. As regard to the personal problems I can assure the team that I will do everything possible in

my capacity to rectify it.

6. I should bring to the attention of the employees in gentle but firm manner that, their

individual problems must not affect the morale.

7. I will try to seek company’s help for their personal problem.

8. These they should be noticed that the high morale will reflect in good salary rise, better

facilities etc.

9. If low morale continues then the management will be obliged warning letters, demotions and

worst case termination also

5. you suspected that a radiographic team under supervision of your inspector has radiographed

the same weld seam and only changing the lead letters

a. What would be your initial course of action? Or what action would you take to confirm

this?

b. If your suspicion is proved to be correct, what would be your further course of action?

Or what action would you take upon your conformation?

Actions to confirm

1. Conduct the radiographic audit in the batches and if similar looking radiographs are found

then they should be verified at job against the welds comparing by profile or by any parent

metal marks.

2. If many such suspected radiographs are found then the full audit of all radiographs should be

performed.

3. Physically inspect three or four joints to random mark with correct identification number and

take new radiographs by using new radiographic crew.

4. Evaluate the new radiographs and compare with the previous taken radiographs of the

respective joints.

5. The outcome of this investigation could be of two types

a. Rare case of duplication

b. Occurrence of duplication in many cases

In the first case it is most likely to be a human error; hence the matter can be resolved by

making NDT supervisor aware of facts.

In the second case it is an intentional action performed to help somebody’s interest, which is

obviously a set back to the quality.

Actions upon conformation

1. Inform the occurrence to the higher authorities or supervisor and produce objective evidence

2. Identify the crew which has taken with wrong identification

3. Raise NCR

4. Arrange to remove and replace the crew immediately

5. Arrange to reshoot all joints by using new crew

6. Establish proper monitoring system to avoid reoccurrence of such problems

7. Arrange to close NCR

A meeting of all inspectors to be conducted and they should be issued a strong warning letter to

improve the level of their performance to avoid such incident in future.



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6. What is the course of investigation for vessel rupture with loud bang?

Based on the above information one can construe the failure must be catastrophic in nature, which

means in all likeness mode of failure is to be brittle. However there could be more than one mode of

failure I.e. the initiation could be the fatigue mode followed by brittle. Because of this reason it is

advisable to personality visit the venue of failure to do some visual inspection of exposed surface to

find out the mode of failure. If the failure found be brittle in nature the following will be the symptoms

1. rough and crystalline surface

2. the chevron mark having “V” shaped pointing towards the point of initiation otherwise if

failure initiated in fatigue mode then it will be manifested by

3. smooth surface having dull texture

4. half round crescent or beach marks

It is also important to note whether the initiation of rupture is in weld/HAZ or in the base metal then

one can further investigate the following avenues

If in base metal

1. chemical composition and physical properties certificates supplied by manufacturer (material

test certificates)

2. heat treatment records and lap test reports if any

3. hardness of the base metal and thickness in the rupture zone

4. suitability of material for the given service conditions

If in weld/HAZ

1. Check the WPS used for welding

2. Visual inspection reports and weld logs

3. Radiographic reports

4. Heat treatment records and charts

5. Hardness reports

Based on the outcome of the above investigation the reason of the failure can be judged.

7. you have overheard a conversation suggestion that a third party inspector who is under your

charge has been allowing repairs of cracks to be made without reporting them qa/qc

department

a. What would be your course of action?

b. If this is found to be correct what would be your course of action?

Since it is grave consequence senior welding inspector should go personally to the job site try to

establish facts in a diplomatic way. Once the facts are established and it is been proved beyond any

reasonable doubts, then the prevention action should be taken in such a way that it will eliminate

further occurrence of such events but will not break any relation.

For the sake of disciplinary measures first, the TPI should be summoned for a private discussion and

may be questioned about his action and omissions. It is imperative that he must be made aware of the

fact that you are aware of his omission. Further to this a meeting should be conducted for all

inspectors and they should be made alert against such instance and they should be instructed to

report such occurrence if found immediately to QA/QC department.

In order to make higher management aware of the omission of third party inspector, a strong letter

may be drafted and circulated to higher management about the omission of TPI for their information

and action.

8. What is transition joint? What are the problems occur during welding of a transition joint?

Where corrosion will occur in transition joint?

A transition joint is a joint between different thickness and or dissimilar metals. It could be of two

categories

1. different base metals

2. different thickness

Assuming that the transition joint in this discussion complied with both of the above two categories.

Following care should be taken during welding



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Transition joint with different base metal:

1. proper selection of electrode to avoid dilution of the weld metal

2. proper selection of current range and polarity type of current

3. back purging required, if any

4. cleanliness

5. pre-heat, PWHT

6. Welding process

Transition joint with different thickness

1. The thicker member should be gradually tapered off to match the thickness of thinner member

such that said taper will not exceed 1:4

2. The completed weld should be blended in such a way it will follow the gradual transition

3. Proper heat treatment should be chosen taking consideration of thickness of thicker member

On steels, the HAZ of the weld tends to be more brittle i.e. it has lower notch toughness than the

actual weld metal. The HAZ area is therefore more prone to cracking especially when hydrogen is

induced, although it must be noted that the tensile strength of the HAZ is normally high in comparison

with the weld and parent material. Unfortunately it a fusion welding process is being used then the

HAZ cannot be eliminated.

Problems occur during welding a transition joint

1. Consumable selection

2. Hot cracking due to thermal expansion of steel

3. Cold cracking due to uneven expansion and contraction of thick and thin member or different

material properties

4. Corrosion will occur in SS side in HAZ

9. What is lamellar tearing? describe briefly causes and control measures for lamellar tearing

Crack type : lamellar tearing

Location : below the weld, HAZ (T & Corner Joints)

Steel types : High sulphur & phosphorous steel

Susceptible microstructure : cold rolled

It is a step like crack occurring in the parent metal or HAZ of steel with poor through thickness

ductility, where the fusion boundary of the weld is parallel with plate surface. It is usually associated

with restrained joints on corner, tee or fillet welds joining thick plate.

Causes

1. poor through thickness ductility

2. non-metallic inclusion in the direction of rolling

3. restrained joint

4. through thickness stress

5. high sulphur/phosphorous content

6. presence of hydrogen

Lamellar tearing occurs when two conditions exist at the same time:

a. A susceptible rolled plate is used to make a weld joint

b. High stresses act in the through-thickness direction of the susceptible material

(known as the short-transverse direction)

Control

1. Reducing the size of weld

2. modify joint design

3. control restraint

4. use of forged materials for critical work

5. Grind the parent metal and fill with ductile weld metal. A buttering layer of high ductility

weld metal may be deposited where the vertical member is to be welded.



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6. Asses the through thickness ductility by short transverse tensile test

7. Inspect the plate for non-metallic inclusions

8. Carry out full chemical analysis to make sure sulphur is less than 0.05%

10. What is solidification crack describe briefly causes and controlling measures?

Cracking that takes place during the weld solidification process is termed either hot cracking or

solidification cracking and occurs in all steels which have high sulphur content - sulphur causes low

ductility at elevated temperatures.

In order for a crack to develop the solidifying metal must be subjected to a high tensile stress, this

may by present as a result of weld metal contraction combined with high restraint. Solidification

cracks usually occur longitudinally down the centre of the weld because of the segregation of

impurities and have a blunt profile.

Centreline solidification cracks tend to be surface breaking at some point in their length and can be

easily seen during visual inspection because they tend to be relatively wide cracks.

Solidification cracking occurs when three conditions exist at the same time:

1. Weld metal has a susceptible chemical composition (sulphur and phosphorus)

2. Welding conditions used give an unfavourable bead shape

3. High level of restraint or tensile stresses present in the weld area

Below causes may accelerate Solidification Crack

1. Contamination in weld joint

2. Unfavourable welding condition

3. Improper Width to depth ratio

Control measures

1. Control the sulphur content

2. Use consumable with high manganese

3. Keep manganese-sulphide: carbon ratio as low as possible

4. Minimise restraints

5. Use low dilution process

6. Weld joints are thoroughly cleaned immediately before welding

7. Maintain proper width to depth ratio

8. Use preheat

11. Explain solidification crack in ferritic steels

Solidification cracking is a hot cracking mechanism that caused during solidification of weld in

ferritic steels, containing high sulphur content. During welding sulphur in the plate may be remelted

and will fuse with iron to form iron sulphide (FeS). These iron-sulphides are low melting point

impurities, so that collect around the grain boundaries, which are under great stress due to the action

of contractional forces. The bonding between the grains may now be insufficient to maintain cohesion

and cracks will result running through the length of the weld centreline.

Causes

1. Weld metal has a susceptible chemical composition

a. High sulphur

b. High carbon

c. High phosphorus





6. High dilution process




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Control measures

1. Control the sulphur content

2. Limit the heat input, hence minimising expansion and contraction

3. Increase the grain boundaries by adding delta ferritic





12. Explain solidification crack in stainless steel

Solidification cracking is a hot cracking mechanism that occurs during solidification of weld metal in

austenitic stainless steels. Austenitic stainless steels have large grain structure compared to ferritic

steel grains. During solidification low melting point impurities collect around these large austenitic

grain structures in the weld centreline. These large grains have small gain in boundaries compared to

ferritic steels. This lack of grain boundary area between the grains may be insufficient to maintain

cohesion and cracks occur in the centreline of weld along its length.

Causes

1. Weld metal has a susceptible chemical composition (low melting point impurities)






Control measures

1. Control the low melting point impurities (sulphur/phosphorous)

2. Ensure the weld joints are thoroughly cleaned

3. Limit the heat input, hence minimising expansion and contraction

4. Increase the grain boundaries by adding delta ferritic





13. What is weld decay describe the causes and prevention measures?

Weld decay occurs in unstabilised austenitic stainless steel with 550°C to 850°C range of the HAZ. At

this temperature range carbon is absorbed by chromium and chromium carbide precipitated at the

grain boundaries as a metal cools down. This precipitation of chromium carbides consumed the

alloying element cause a local reduction in chromium content, which has the effect of lowering the

resistance to corrosive attack and allowing occurring.

Controlling measures

1. using of stabilised steels (with addition of Ni or Ti)

2. Use low carbon stainless steels i.e. 316L, 304L (carbon content below 0.03%)

3. Heating to about 1100°C where chromium carbide will be dissolved. Then steel is normally

quenched from this temperature to stop re-association.

14. What is liquation cracking describe the causes and prevention measures?

Crack type : Liquation crack

Location : HAZ

Steel type : Low quality sulphur content steels



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Liquation cracks occur in steels, which have high sulphur content. When welding low quality high

sulphur content steels, it is possible that areas containing iron-sulphide (FeS) in the HAZ will liquefy.

These low melting point iron-sulphides usually accumulate at the grain boundaries. If this melting

occurs in the presence of high contractional stress, then the boundaries will be pulled apart and

liquation cracks occur.

Causes

1. High sulphur content

2. High restraint

3. High contractional stresses

Control

1. Use high quality refined steel

2. Controlled heat input

3. Minimise restraint

4. Use preheat

15. What is reheat cracking describe the causes and prevention measures?

Crack type : Reheat cracking

Location : Coarse grained HAZ and weld metals

Steel type : Low alloy steel, creep resistance steels

Susceptible microstructure : Embrittled coarse grains

Reheat cracking is also known as relaxation cracking. It mainly occurs in HAZ of welds particularly

in low alloy steels during post weld heat treatment or service at elevated temperatures.

Most alloy of steel subject to an increase of embrittlement of the coarse grained region of the HAZ

when heated above 600°C. The problem is worse with thicker steels containing Cr, Cu, Mo, V, Nb and

Ti. Sulphur and phosphorus also have an influence. Typical steels susceptible would be the 2 ¼ Cr.

Mo. V type. Example creep resistance steels

During post weld stress relief and at high operating temperature the residual stresses would be

relieved by creep deformation which involves grain boundary sliding and grain deformation. If due to

metallurgical conditions these actions cannot occur, then grain boundaries may be open up into

cracks

Causes

1. areas of high stress concentration and existing weld defects

2. the toes of badly shaped fillet welds, incomplete root penetration welds

3. high creep resistance

Control

1. toe grinding, elimination of partial penetration welds

2. rejection of poor weld profile

3. heat quickly through the susceptible temperature 450°-550° C

4. use high preheat temperature and stage wise PWHT during welding large fabrication to

reduce the risk of reheat cracking in the final stress relieving

5. use of weld metal with high ductility

16. Describe the phenomenon of hic or under bead cracking and prevention measures

During fabrication by welding, cracks can occur in some types of steel, due to the presence of

hydrogen. The technical name for this type of cracking is hydrogen induced cold cracking (HICC) but

it is often referred to by other names that describe various characteristics of hydrogen cracks:

1. Cold cracking - cracks occur when the weld has cooled down



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2. HAZ cracking - cracks tend to occur mainly in the HAZ

3. Delayed cracking - cracks may occur sometime after welding has finished (possibly up to

~48h)

4. Under bead cracking - cracks occur in the HAZ beneath a weld bead

These types of cracks often originate from sub-surface locations under the weld in HAZ. Hydrogen

cracking in the HAZ of steel occurs when 4 conditions exist at the same time:

1. Hydrogen level > 15ml/100g of weld metal deposited

2. Stress > 0.5 of the yield stress

3. Temperature < 300°C

4. Susceptible microstructure > 400HV hardness

These four conditions (four factors) are mutually interdependent so that the influence of one condition

(its’ active level) depends on how active the others three factors are.

The phenomenon of HIC is as follows

During welding small amount of free hydrogen is generated due to decomposition of moisture from

the air, electrode coating, shielding gas or contaminations on the surface to be welded. This hydrogen

can dissolve in the molten steel and from there diffuse into extremely hot but solidified base metal. If

the cooling is sufficiently slow, this evolved hydrogen has enough time to escape to the atmosphere by

diffusion. However if the cooling is rapid some hydrogen may get trapped in HAZ. This hydrogen

produces a condition called as “Hydrogen Embrittlement” in the locations of its entrapment, which

are dislocations and voids between grains. Also it generates very high hydrostatic pressure in the

space of its confinement. This pressure combined with shrinkage stress due to cooling produce tiny

cracks in metal immediately next to weld bead, which are sub-surface initially but eventually

propagate to surface.

Avoid or Control measures for HICC

Because the factors that cause cracking are interdependent, and each need to be at an active level at

the same time, cracking can be avoided by ensuring that at least one of the four factors is not active

during welding.

Methods that can be used to minimise the influence of each of the four factors as follows

1. Use of low hydrogen electrodes

2. Electrodes to be baked and should be stored in hot holding oven to avoid moisture pickup

3. Ensuring that the weld zone is dry and free from rust/scale and oil/grease

4. Control moisture in shielding gas

5. Avoiding stress concentrations due to poor fit-up

6. Avoiding poor weld profile (sharp weld toes)

7. Applying a stress-relief heat treatment after welding

8. Increasing the travel speed as practicable in order to reduce the heat input

9. Keeping weld metal volume to an as low level as possible

10. Procuring steel with a CEV that is at the low-end of the range for the steel grade(limited

scope of effectiveness)

11. Using moderate welding heat input so that the weld does not cool quickly (and give HAZ

hardening)

12. Applying pre-heat so that the HAZ cools more slowly (and does not show significant HAZ

hardening); in multi-run welds, maintain a specific inter-pass temperature

13. Post heat to slow down the cooling rate

17. Describe the under bead cracking and prevention measures in Q/T steels (Quenched and

Tempered)

Q/T steels are normally full alloyed steels which have high hardenability due to high carbon

equivalent. Such steels subsequent to welding if allowed cooling down rapidly produce brittle

microstructure in HAZ. In such circumstances if the hydrogen gets involved in the process and

trapped in brittle microstructure will produce a condition called as “Hydrogen Embrittlement” in the



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location of its entrapment which are dislocations and voids between grains. Also it generates very

high hydrostatic pressure in the space of confinement. This pressure combined with shrinkage stress

due to cooling produce tiny cracks immediately next to weld bead, which are subsurface initially but

eventually propagate to surface. (as stipulated above in phenomenon of under bead cracking and

thereby cause under bead cracks in Quench and Tempered steels.)

Prevention

1. giving sufficient heat input by means of pre heating

2. maintain proper inter-pass temperature

3. reduce the rate of cooling by means of post heating and adequate PWHT

4. Use low hydrogen process for welding

5. Performing welding in stress free conditions

18. Describe the under bead cracking and prevention measures in hsla steels

Unlike in Q/T steels, HSLA steels are ferritic in nature. The properties of these steels are achieved by

small amounts of alloying elements dissolved in their ferritic structure. For this very reason they are

soft and ductile as compared to QT steels. Such steels, subsequent to welding if cooled too rapidly,

may undergo a change of microstructure from ferritic to martensitic namely in HAZ. Once martensitic

is formed it is hard and brittle. In such circumstance if any hydrogen pick-up takes place it may very

well lead to phenomenon of HIC or under bead cracking

Prevention

1. ensure that base metals have enough ductility

2. ensure that base metals have sufficient low % of carbon, manganese and other alloying

element which cause appreciable martensite formation

3. reducing the rate of cooling of weldment

4. performing the welding in stress free conditions

5. use of low hydrogen process

19. Describe the three fracture mechanisms

Welds may suffer three different fracture mechanisms:

1. Fatigue

2. Ductile

3. Brittle

Often a complete fracture of a weldment will be a combination of fracture types e.g. initially fatigue

followed by final ductile fracture.

Fatigue

Fatigue fractures occur in situations where loading is of a cyclic nature and at stress levels well

below the yield stress of the material. Typically fatigue cracks will be found on bridges, cranes,

aircraft and items affected by out of balance or vibrating forces. Initiation takes place from stress

concentrations such as changes of section, arc- strikes, and toes of welds. Even the best designed and

made welds have some degree of stress concentration.

Following appearances of exposed surfaces manifests these kinds of fractures.

1. Very smooth fracture surface, although may have steps due to multiple initiation points.

2. It is encompassed by crescent marks or beach marks

3. Bounded by curved crack front

4. Bands may be visible indicating crack progression.

5. Initiation point opposite curve crack front

6. Surface at 90° to applied loading

Fatigue cracks sometimes stop of their own accord if the crack runs into an area of low stress. On the

other hand they may grow until the remaining cross-section in insufficient to support the applied

loads. At this point final failure will take place by a secondary mechanism i.e. ductile or brittle.



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Ductile

Occur in instances where the strength and the cross-sectional area of the material are insufficient to

carry the applied load. Such fractures are commonly seen on material and welding procedure tensile

test specimens where failure is accompanied by yielding, stretching and thinning.

A ductile fracture is an outcome of plastic deformation of material to the point of rupture. It is

manifested by

1. Surface is torn and rough

2. Shear lips at 45° applied stress

Brittle

Brittle fracture is result of composition of hard, brittle material and an impulsive snappy load. It is a

fast, unstable type of fracture which can lead to catastrophic failure.

Following factors will increase the risk of brittle fracture:

1. As the temperature (ambient or operational) decreases

2. With the type and increasing thickness of the material

3. Where high levels of residual stresses are present

4. In the presence of notches.

5. Increased strain rate i.e. speed of loading

Distinguishing features of a brittle fracture are:

1. Surface is flat and at 90° to the applied load.

2. Will show little or no plastic deformation

3. The surface will be rough and may be crystalline in appearance.

4. May show “V” shaped chevrons on the surface which will point back to the initiation source

Out of the above types fatigue is always the first mode of failure. If failure is in second mode i.e.

ductile or brittle, then these failures will always be following fatigue and not vice-versa. Otherwise

there could be purely ductile or purely brittle failures also which manifested by the appearance as

mentioned above.

20. Describe residual stresses

Metals contract during solidification and subsequent cooling, but if this contraction is prevented or

inhibited residual stresses will develop. Most metal products contain residual stresses, often up to the

yield point. Pipe products for example are usually very highly stressed. The tendency to develop

residual stresses when the heating and cooling are localised. So welding with its much localised

heating and the presence of liquid and solid metal contact can be expected to induce very high levels

of residual stressed. Residual stresses can be difficult to measure with any real accuracy, but a rough

guide is that when the weld metal exceeds 2 inch3 (14 cm3) then the total residual stress is about yield

point in magnitude.

Normal welds develop residual stresses:

1. along the weld – longitudinal residual stresses

2. across the weld – transvers residual stresses

3. through the weld – short transverse residual stresses

21. Describe distortion

Distortion is caused by stress. Distortion related to the change of shape of a component, which results

from welding. This change in shape may be temporary (elastic) or permanent (plastic). If two pieces

of materials e.g. plates, which are to be joined, are free to move during welding distortion will occur.

If the two pieces of material are not free to move (restrained) the force will remain as residual

stresses (no distortion)



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Types of distortion

1. longitudinal shrinkage

2. transverse shrinkage

3. angular distortion

4. bowing

Factor which affect distortion

1. material properties and condition

2. heat input

3. Amount of restraint

4. Joint design

5. Part fit-up

6. Welding procedure

Method of reducing distortion

1. Pre-setting, pre-bending

2. Forced restraint e.g. welding fixtures, flexible clamps, strong backs

3. Using balancing welding technique e.g. back strip welding, back step welding

4. Using by design e.g. Elimination of welding, Weld placement, Reducing the volume of weld

metal, Reducing the number of runs

5. Reducing the heat input

22. Describe distortion in a simple weld with single “v” preparation

The action of the residual stresses in weld in welded joints is to cause distortion. Consider a simple

weld with single “V” preparation.

The following movements can be detected

1. contraction in the weld and HAZ along with the length

2. bowing due to the greater volume of weld metal at the top of the weld

3. peaking due to the “Vee” angle

4. ripple (in sheet) away from the weld

5. contraction in the weld metal and HAZ transverse to the weld

Control of distortion is achieved in one or more of the following ways

1. pre-setting or pre-bending – so that the metal distorts into the required position

2. clamping – to prevent distortion, but this increases the level of residual stress

3. welding sequence – i.e. balanced welding, back step or back strip welding

23. Destructive testing or mechanical testing

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 2 groups, those used to:

1. Measure a mechanical property – quantitative tests

2. Assess the joint quality – qualitative tests

Mechanical tests are quantitative because a quantity is measured – a mechanical property such as

tensile strength, hardness and impact toughness.

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).

Test objectives



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Various types of mechanical test are used by material manufacturers/ suppliers to verify that plates,

pipes, forgings etc… have the minimum property values specified for particular grades.

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 that are carried out for welding procedure qualification are

intended to demonstrate that the joint properties satisfy design requirements.

Tensile Test – Transverse tensile tests

To measure the transverse tensile strength under static loading

1. A reduced specimen assesses the tensile strength of the joint

2. A radius reduced specimen assesses the tensile strength of the weld meta

Tensile Test – Cruciform test

To measure the relative tensile strength of joints with fillet welds under static loading (Load through

welds)

All weld Tensile Test

To measure Yield Strength & Tensile Strength of (% Elongation also measured & usually also %

Reduction of Area)

1. Electrodes of filler wire / flux combinations

2. Quality of the weld metal as deposited

3. STRA – Short transverse reduction areas to access lamellar tear

Bend tests (transverse and longitudinal)

To determine the

1. Soundness of weld metal

2. Weld junctions

3. Heat affected zone

All specimens to be removed and prepared without causing significant distortion or heating

Side bend test

To determine the soundness of a joint in cross section

Charpy “V” notch test

To determine the energy absorbed at a specified temperature to fracture the specimen.

Nick break test

To fracture the joint through the weld metal to permit examination of the fracture surface

Fillet weld fracture test

To fracture the joint through the weld metal to permit examination of the fracture surface (Swan

notch in compression)

Macro examination

To examine the whole joint for soundness

CTOD (Crack Tip Opening Displacement Test)

CTOD is a test method for the determination of a metals resistance to the initiation of a crack

resulting from notch defects.

CTOD measures the elastic-plastic toughness of the metal in the ductile-brittle transition. The

propagation of a crack in a welded structure depends upon factors including the materials used. The

size and sharpness of any notch present, operating temperature, the degree of restraint and welding

procedure requirements.



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CTOD test permits full size specimens to be used irrespective of metal thickness to which a notch of

given width and depth is applied. The specimen is subjected to a high speed resonance load cycling

on a three point bending rig. A clip gauge is fixed to the mouth of the notch accurately measures the

slow opening of the crack and a force sensing device enables the applied load to be plotted against

displacement on a graph.

24. Explain haz – heat affected zone

During welding using fusion welding process there is a huge temperature difference between the weld

and parent material. Because of this temperature difference, the material immediately adjacent to the

weld undergoes micro structural changes.

This area which lies between the fusion boundary and the unaffected parent material is called heat

affected zone HAZ. The extent of changes in microstructure will depend on the following.

1. Material composition especially carbon content

2. Heat input – the higher the heat or arc energy, the wider HAZ. Metallurgical properties will

also be affected.

3. The rate of cooling – higher the rate of cooling, harder the HAZ especially C.E. of the steel is

high.

The HAZ in a weld zone on steel consist of up to four separate regions, starting from the area

immediately to the weld.

1. Coarse grained region – heat between 1100°C and melting point

2. Grain refined region - 900°C to 1100°C

3. Region of partial transformation - 750°C to 900°C

4. Region of spheroidization – just below 750°C

25. Describe briefly saw wire/flux + saw consumables

AWS A5.17.89 is a specification for carbon steel electrode and fluxes for SAW. The coding system

shows the flux capabilities when combined with a specific electrode.

Example coding

F7A6 – EM12K or EC1 (Trade Name)

F – Indicates flux

7 – Indicates the weld metals minimum ultimate tensile strength in Kpsi x 10 (7x10=70Kpsi), when

using the flux with the electrode identified.

A – Designates the condition of heat treatment to the weld or which test were conducted “A” is for as

welded and “P” for PWHT

6 – Indicates the lowest temperature in degree Fahrenheit x 10 at which a charpy value of 27 J was

achieved.

E – Indicates a solid electrode. EC would indicate a composite electrode

M – This may be L, M, or H indicating Low, Medium or High manganese content

12 – This may be one or two digits and nominal carbon content of the electrode i.e. 12 = 0.12%, 8 =

0.08%

K – Indicates the electrode is made from semi-killed steel.

Additional flux Information

All fluxes to this specification must be of a granular nature and capable of flowing freely when used.

Particle size is to be a matter of agreement between the purchaser and supplier. The flux must permit

the production of smooth with depth of undercut. Fluxes are classified on the basis of mechanical

properties of the weld metal which they produce and therefore have to be shown in conjunction with

the electrode used. Fluxes used to this specification may contain fusible compounds of various

proportions. Some fluxes contain de-oxidisers, others do not and fluxes may react differently with

different electrodes and are voltage used. A change of arc voltage during welding will change the

amount of flux melted and may therefore change the composition of the weld metal. The effect of this

change allows fluxed to be described as neutral, active or alloy.



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Neutral fluxes

Neutral fluxes are those which do not produce any significant change in the weld metal chemical

analysis irrespective of arc voltage / arc length changes. Fluxes of this type contain little or no de-

oxidisers and rely on electrode for de-oxidation. They are mainly used for multi-pass welds

Active fluxes

Active fluxes contain manganese and silicon as de-oxidisers and the effect of those on the weld metal

will change as the arc voltage changes. These fluxes are used mainly for single pass welds.

Alloy fluxes

Alloy fluxes are those which can be used with a carbon steel electrode to produce a low alloy weld

metal as such they come under the scope of AWS a5.23, low alloy steel electrodes and fluxes for SAW.

Flux basicity or classification

Basic oxides tend to be more stable than acidic oxides. Fluxes for SAW may be classified as follows

1. acid – general purpose use and for dirty (rusty) steel

2. neutral

3. semi basic – improving quality

4. basic

5. high basicity – maximum weld toughness and performance

26. Describe briefly fused and agglomerated flux for saw

Fused flux

Fused flux are manufactured as follows, the ingredients are mixed and melted at high temperature,

the mixture is then poured on to large chill blocks or directed into a steam of water to produce

granules which have a hard glassy appearance. The material is then crushed, sieved and packaged.

Advantages

Good chemical mix achieved

They do not attract moisture, (not hygroscopic) this improves handling, storage, use and weldability.

Any moisture present is easily removed by low temperature drying.

It is easy to remove impurities and fine particles etc. when recycling.

Disadvantages

The main disadvantage is the difficult in adding de-oxidants and Ferro-alloys. These would be lost

during the high temperature manufacture. The maintenance of a controlled flux depth is considered

critical.

Agglomerated flux

All the flux materials are dry mixed and then bonded with either potassium or silicate. They are then

baked at a temperature below the fusion or melting point and therefore remain as a powder, which is

sieved for size and packaged.

Advantages

Can be colour coded

Easy addition of de-oxidants and Ferro-alloys

Flux depth not co critical

Disadvantages

Tendency for flux to absorb moisture and difficult to re-drying procedure

Possibility of molten slag, causing porosity

Difficult recycling i.e. removal of impurities and sieving



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27. A failure has been occurred in service at 40°c what is your evaluation on this?

Service temperature of the order of 40°C tells that the failure most probably has occurred due to lack

of strength or toughness at that temperature. Compared to base metal a weld is always of irregular

shape and hence considered as irregularity or discontinuity in surface profiles. Any discontinuity

serves as a stress raiser when it comes across lines of stresses. The strength of material / metal would

drops at the locations of high stress concentration especially when temperature drops significantly. In

brief metal tends to lose its “notch toughness”. Hence our area of investigation should be notch

toughness of given weld at low temperature. This can be approached in following ways.

1. Verifying that WPS has recommended proper consumables to be used and all the essential

variables were adhered to.

1. heat treatment records and lap test reports if any

2. Review batch certificates for consumables used chemical composition and physical properties

certificates supplied by manufacturer (material test certificates)

3. hardness of the base metal and thickness in the rupture zone

4. suitability of material for the given service conditions

2. Location of failure should be inspected and point of initiation should be established

If the location of failure initiation happens to be without any defect viz., undercut or porosity then

failure can be attributed to sheer lack of low temperature strength and consumable giving higher low

temperature strength may be recommended and improvement in weld profile may also be advised.

However if the point of initiation happens to be a defect such as porosity or any sub surface defect

then corresponding radiograph for that section of weld may be closely examined and interpreted. In

such cases more stringent acceptance criterion may be recommended in addition to recommendations

mentioned above.

28. If you detect an arc strike what is the course of action?

If any arc strike is found on the parent metal is should be ground smooth and MPI is to be conducted

on the location, if it is a ferrous material. For S.S PT is to be conducted.

29. What are the documents required to do repair?

Approved repair welding procedure, qualified welders, method of exploration of defect, method of

defect removal, repair report.

30. What would be the result of using temperature 1300°c in heat treatment?

Steel which are overheated above 1200°C may suffer a permanent loss of toughness, distortion and

also forms large quantities of mill scale on their surface.

31. What are the differences between a welding procedure approval and a welder qualification

test?

The welding procedure approval test is carried out by a competent welder and the quality of weld is

assessed using non-destructive and mechanical testing techniques. The intention of the test is to

demonstrate that the proposed welding procedure will produce a welded joint which will satisfy the

specified requirement of weld quality and mechanical properties.

Welder approval test examines a welder’s skill and ability in producing a satisfactory weld. The test

may be performed with or with a qualified procedure, (Note: without an approval welding procedure

the welding parameters must be recorded.) welder approval must be done prior to start the welding in

production site. Welder should be qualified to do the task.

32. Can a non-approved welder be employed to perform welding test?

Yes



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33. Describe two method of producing approval procedures?

1. By using prequalified procedure

2. By establishing a procedure

3. By doing mock-up or by trial and error method

34. How to improve team spirit?

1. If there are aged and young inspectors in my team I will give more responsibility to aged one

than younger one so that everyone will get equal load with job according to their experience.

2. Off the job, play games like cricket, badminton etc. against inter department which will make

them united.

3. Once in a while call them for meeting to discuss the latest development

4. Motivate them by giving small incentives or gift at the end of project to encourage the team

work.

5. On special occasion arrange social programme against inter department.

6. Help them all personally without partiality

7. Discuss often their site problems

8. Offer them immediate rewards when they completed really risky and effective job

35. Going to sickness it has been necessary for you to replace a very experienced welding inspector

he has been responsible for carrying out all welder approval testing. his replacement has to

come from your existing staff that has not vast experience in this field

a. How would you instruct the replacement in his new duties and what critical points

would you emphasis?

Prior to assigning the job you would assess the inspector knowledge level in the welder approval test

and you would instruct to carry out and observe the following

1. Collect and go through relevant welding procedure specification and other procedures.

2. Prepare the measuring instrument those are required during the test for checking and

inspection tools like tongue tester, temperature indicating crayons, inspection mirror, torch

light weld gauges, measuring tape etc. and check their calibration validity.

3. Check the test piece material specification and dimension as per WPS.

4. Check the welding preparation for correct bevel angle, root face, root gap and mismatch.

5. Check consumable certificate such as filler wire, electrodes, fluxes and gases going to be

used for welder test.

6. Check fixing position of the test piece that is 1G, 2G, 3G, 4G, 5G and 6G etc.

7. Mark the bottom and top position in case of pipe

8. Measure heat input.

9. Final weld visual inspection

10. Mark welder’s name date WPS No and position

11. Prepare test report and submit to supervisor for record and NDE processing.

36. Define quantitative test and qualitative test

Quantitative Test

For measuring a “quantity” (quantity test = a mechanical property)

Typical mechanical testes

- tensile test

- hardness test

- charpy V notch test & CTOD

Qualitative test

For assessing joint “quality” (quality test = good fusion & free from defects)

Typical qualitative tests

- bend test

- macro examination (micro examination for some metals)



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- fillet fracture & nick break test

37. What does a welding procedure consist of?

Welding procedure consist of

1. essential variables

2. non-essential variables

3. supplementary essential variables

Essential variables

A change in welding parameters which effects the mechanical properties of a weld are called

essential variables. E.g. process, type of material, electrode / flux, shielding gas, preheating, PWHT

etc…

Non-essential variables

Changes in welding parameters, which will not affect the mechanical properties of the weld metal, are

called non-essential variables. E.g. groove angel, method of cleaning etc.

Supplementary essential variables

Supplementary essential variables are variables that have an effect on the impact properties of a

joint. They are classed as Non-Essential if impact testing is not required. The welding procedure shall

be attached with PQR to show the evidence that the procedure meets the mechanical properties

desired by the code / specification.

38. Give typical example of welder qualification range for a

a. thickness

b. diameter

c. process

Thickness - When welder is tested on thickness “T” he is qualified to weld two times the thickness

“2T”

Diameter – when welder is tested on diameter “D” he is qualified to weld pipe size “D/2” and above

Process – welder is qualified to weld only which process he has been tested

39. Explain why the quality of the parent metal may affect the incidence of weld metal cracking?

Lower quality or dirty contaminated steels have a higher residual content e.g. sulphur, phosphorus

etc. due to the lower melting point of these impurities segregated into the centreline of the weld pool

during the solidification and will form a plane of low ductility which may crack when acted upon by

the normal transverse residual stress.

40. Explain purpose of preheat

Preheating involves heating the base metal, either entirely or just the region surrounding the joint to

a specific desired temperature, called the preheat temperature

Purpose

1. reduce the risk of hydrogen crack

2. reduce the hardness of the weld heat affected zone

3. reduce shrinkage stresses during cooling and improve the distribution of residual

If preheat is locally applied it must extend to at least 75mm from the weld location and be preferably

measured on the opposite face to the one being welded.

The selection of preheat temperature should be based on three factors listed in order of importance

1. composition and hardenability of the base or parent metal

2. the feasibility of post weld heat treatment

3. the size, thickness and configuration of the part to be welded

The temperature of the part can be checked by use of temperature indicating crayons (temp-sticks)

tough pyrometers or thermocouples.



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41. Explain PWHT

Post weld heat treatment is a process in which the metal in the solid state is subjected to one or more

controlled heating cycles after welding. This PWHT is normally carried out for the purpose of stress

relief and ensuring that the HAZ hardness is not too high for particular steels with certain service

applications. PWHT may also be used to produce certain properties such as softening after cold

working.

Few more advantages of PWHT

1. Improve the resistance of the joint to brittle fracture

2. Improve the resistance of the joint to stress corrosion cracking

3. Enable welded joints to be machined to accurate dimensional tolerances

Because the main reason for (and benefit of) PWHT is to reduce residual stresses, PWHT is often

called stress relief.

The following variables for PWHT must be carefully controlled

1. Maximum heating rate

2. Soak temperature range

3. Minimum time at the soak temperature (soak time)

4. Maximum cooling rate

42. Terms & definitions

Quality assurance

All the planned and systematic actions and activities required providing an adequate level of

confidence in a product, what is wanted?

Quality control

The operational techniques and activities used to fulfil quality. What must be done / controlled, in

order to achieve what is wanted

Quality control inspection

Quality control inspection as an “activity such as measuring, examining, testing or gauging one or

more characteristics of a product or service, and comparing the results with specified requirements in

order to establish whether conformity is achieved for each characteristic”.

In-process inspection

Inspection & surveillance carried out during production

Non-compliance

A written report that states that a clause or instruction in the contract documents, code or standard

cannot be or was not met.

NCR

A non-conformance report documents the details of a non-conformance identified in a quality audit or

other process review. The objective of the report is to make an unambiguous, defensible, clear and

concise definition of the problem so that corrective action can and will be initiated by management.

Concession

An agreed deviation (with the customer or client) from a pre-agreed path, or specification

Inspection specification

A document containing or referring to all information required in the level of inspection for a

product.

Certificate of conformance

A signed certificate, declaring that a product has been produced in accordance with a specification

Defect



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A welding imperfection that falls outside of a level of acceptance criteria in an applied standard

Minor defect

Unlikely to cause failure of the product

Major defect

Likely to cause failure, but small risk of loss of life

Critical defect

Extremely likely to cause failure, with high risk of loss of life

Audit compliance

It determines quality system complies with the applicable quality control procedures

Material specification

The specification applicable to a raw material which is used in the fabrication of a product

Auditor

The certified quality auditor is a professional who understands the standards and principles of

auditing and the auditing techniques of examining, questioning, evaluating and reporting to

determine a quality system’s adequacy and deficiencies.

Calibration:

Operations for the purpose of determining the magnitude of errors of a measuring instrument, etc.

Validation:

Operations for the purpose of demonstrating that an item of welding equipment, or a welding system,

conforms to the operating specification for that equipment or system

Accuracy:

Closeness of an observed quantity to the defined, or true, value

43. As a team leader what steps you will take for improving quality?

a. If a member has to be replaced what all things to do?

b. What are the things you will brief in start of a job for your new member?

Actions to Improve quality

1. I conduct periodic and systematic audit, based on audit finds such non-conformance, any

other quality related issues, take preventive actions and avoid such things occur in future.

2. Conduct quality related meetings with inspectors, other department members, and look for

any ideas to improve quality or any quality related concerns they have in their job, take

necessary preventive actions.

3. Any complaints from clients / TPI or feedback from clients, take necessary preventive actions.

4. Technical information related to quality; circulate to all concern departments members

5. Conduct training programs for specialized jobs and critical jobs

6. Provide motivation, motivated employees provide a better working environment in addition to

the product or service output benefits

Actions with replacing member

Get hand over note from replacing member including the following

1. Hand over note including completed status, which was handled by him, current job status,

any quality related issues such as site query, concession request, NCR log etc.

2. Document management etc.

3. Contact details of client representative, contractor personal email address, contact telephone

numbers



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4. Contact details of replacing member for future reference

Actions for new member

1. Welcome and introduced to all staff including higher authority

2. Safety induction explain minimum PPE, emergency exit, and emergency contact numbers

3. Brief explain about work system organization chart, reporting channels etc.

4. Brief explain about project specification, quality control procedure, ITP, method statements,

safety procedures, quality management system and location available of those documents

5. Brief explain about site query, NCR log, WPS, PQR, and WQT records etc.

44. Misunderstand between NDT inspector and QC inspector, why is it rectified? How will you

rectify? explain briefly

Reasons to rectify

1. It will lead to miscommunication which will affect the quality of NDT such as wrong

identification of weld joint, wrong NDT method, wrong weld details.

2. Back log in work, substandard work output, work delay in schedule

Rectification measures

1. Conduct the meeting with QC inspector and NDT inspector

2. Open discuss with them, find actual problem

3. May have technical problem, communication problem like language problem or personal

problem like leave overdue, sick family reason

4. Analysis the root cause of problem and solve

5. Verify the correct system is followed, it not establish the system

6. Continuous monitoring the inspectors activities

45. Give brief describe of the difference between macro and micro examination also state the

purpose of the examination?

Differences

1. macro examination magnification is 10x or lower

2. micro examination magnification is greater than 10x usually 100x or higher

3. macro specimen need rough and ground with 80 grit finish

4. micro specimen need very fine grinding at 600 grit and polish / etching to produce a mirror

finish

Purpose of examination

1. Macro examination: to determine depth of fusion, depth of penetration, effective throat, weld

soundness, degree of fusion, presence of discontinuity, weld configuration, number of weld

pass etc.

2. Micro examination: to determine micro structural constituents, presence of inclusions,

presence of microscopic defects, and nature of cracking etc.

46. Describe briefly the duties of senior welding inspector

A senior welding inspector may be required to manage and control and lead a team of welding

inspectors who will look to him for guidance, especially on subjects of a technical nature. The SWI

will be expected to give advice, handle problems, take decisions and lead from the front. The SWI will

therefore require leadership skills in addition to technical experience. Senior welding inspector is

responsible for the following

1. Signing off the product

2. Prepare department budgets for personnel facilities and supplies

3. Assign work to the inspectors

4. Supervise and evaluate their work

5. Motivate staff to meet standards of quality and efficiency

6. Interlink with other departments to improve procedure and advice on quality problems

7. Receive complying item, understand the problems and establish corrective measures



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8. Review plant equipment condition, inspection reports for fitness to use during service

9. Prepare scrutinize documentation for quality

10. Participate in inspection and planning, reviewing and approve procedure which is prepared

by inspection department

11. Develop teak work, advice on training and other personnel qualification requirements

12. Ensure adequate safety precaution for all personnel

In other circumstances he may have a more technically demanding role that requires detailed

knowledge or particular activities

The technical skills required are:

1. Knowledge of technology

2. Knowledge of code of practice

3. Knowledge of planning

4. Knowledge of organization

5. Knowledge of auditing

Knowledge of technology – required is similar to the welding inspector but with additional cope and

depth of

1. Commonly used NDT technique

2. Radiographic interpretation

3. QA/QC knowledge

4. Basic metallurgy of commonly used welded materials including assessment of fracture

surfaces.

Knowledge of code and practice – the SWI should be aware of common standards applied in the

welding industry

Knowledge of planning – planning of inspection will be required for all phase of inspection (pre-in-

service-post)

Knowledge of organization – organization skills are necessary to ensure their inspection requirement

of any plan can be met on time using the correct personnel for the job

Knowledge of auditing – the knowledge of audit may involve in detailed checks of very limited area of

inspection to ensure that documentation produced meet the requirement of the specification

Leadership requires:

1. Ability to if so required

2. Willingness to direct

3. Acceptance of responsibility

4. Understand of problems

5. Ability to delegate – willingness to trust staff

6. Commitment to oneself

47. A. on a material certificate following abbreviations APPEARS

a. What do they mean?

1. Re

2. Rm

3. Rp0.2

4. Z%

5. A%

6. CEV or CEQ

b. answer the below given questions

1. In a cross joint tensile test what dimensions and readings are taken?

2. Show how these are used to determine the tensile strength

3. Where would you normally expect the specimen to break?

Re means yield stress Reu = upper yield stress Rel = lower yield stress

Rm means ultimate tensile strength

Rp0.2 means proof stress 0.2% of gauge length



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Z% means reduction of area at the point of fracture or transverse ductility (>20% = high resistance

to lamellar tear)

A% means elongation of the gauge length or elongation ductility

To approve a butt welding procedure most of specifications such as ISO 15614 and ASME SEC. IX

require tensile tests to be carried out.

These are generally cross joint (transverse) tensile tests of square or rectangular cross section that as

the name suggests, are oriented across the weld so that both parent metals, both heat affected zones

and the weld metal itself are tested. The tensile test piece typical of the type specified by European

standards, such us EN 895, that specify the dimensions of the test pieces require all excess weld

metals to be removed and the surface shall be free from scratches. 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.

While it is possible to measure the yield strength, the elongation and the reduction of area of

transverse tensile test specimens the fact that there are at least three different areas with dissimilar

mechanical properties makes such measurements inaccurate and unreliable, although this is

sometimes carried out purely for information purpose.

The specifications mentioned above require the UTS and the position of the fracture to be recorded.

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.

In the ASME IX code, if the test specimen breaks outside the weld or fusion zone at a stress above

95% of the minimum base metal strength the test result is acceptable.

In most situations the weld metal stronger than the parent metal – it is overmatched – so that failure

occurs in the parent metal or the HAZ at a stress above the specified minimum.

48. On a material certificate following terms may APPEARS:

a. normalised

b. quenched and tempered

c. as rolled

d. z quality

What are the meanings of these terms?

Normalised

It is a process of heating steel to about 40°-50°C above upper critical temperature holding for proper

time and then cooling in still air on slightly agitated air to room temperature. The resultant

microstructure should be pearlite. It is done for grain structure refinement, homogenization, removal

of residual stress and improved machinability. For plain steel the temperature for normalizing is

860°-915°C, and for alloy steels it is 870°-925°C

Quenched and Tempered

Quenching is a process of rapid cooling from austenising temperature, which results in the

transformation of austenite to martensite. During cooling, heat musts be extracted at a very fast rate

from the steel piece; and is possible when a steel piece is allowed to come in contact with some

medium which absorbs heat from steel within short period. The medium use for quenching is known

quench out. The quenchants used are liquids, air and gases are used in special case.

Quenching is a hardening treatment which develops maximum hardness, excellent wear resistance

and high strength levels in the steel, at the same time it adversely affects properties such as ductility.

Toughness and impact strength and also imparts brittleness because of internal stress developed by

quenching. Such a process, which consists of heating hardened steel below the lower critical



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temperature, followed by cooling in air is known as tempering. Tempering lowers strength and wear

resistance of the hardened steel marginally.

As rolled

As rolled means having improved low temperature toughness. A high strength steel plate of improved

low temperature toughness useful for making an grade line pipe provided with the addition of 0.8 -2%

by weight of nickel and 0.0005 – 0.0040% by weight of Ca., which may be used in the as rolled state

and manufactured through tow step controlled rolling the secondary step rolling of which is carried

out at a temperature lower than conventional rolling.

Z Quality

“Z” quality means low sulphur steel with a tested level of ductility through the “Z” axis of the plate

as opposed to the transverse on longitudinal axis, “Z” quality is determined by through thickness

tensile test hence sometimes known as through thickness tested plate.

49. On a construction site a member of your staff has issued an instruction that all MMA

electrodes have to be baked at 250°C before use. the electrode in question are of the following

types:

a. aws 5.1 e6013

b. bs en 499 e423b (in standard packing)

c. bs en 499 e425ni b (in vacuum packs)

d. bs en 499 e352c

1. Do you agree with this instruction?

2. give reasons for your answer

I would not agree the instructions given that the above mentioned MMA electrodes to be baked at 250

degree Celsius before use

The reasons for my answer as described below:

1. the first given electrode details are AWS 5.1 E6013, it is a rutile electrode, since they have

high combined moisture and also contains up to 10% cellulose they cannot be baked as they

will not give a low Hydrogen weld deposit.

2. The second electrode is BS EN 499 E423B (in standard packing), it is a basic electrode and it

should be baked at 350 degree Celsius for up to 2 hours, since the packing is not sealed they

will not reach the end user a guaranteed low hydrogen condition, and should follow

manufacturer instructions.

3. The third electrode BS EN 499 E425Ni B (In vacuum pack), it is a basic electrode and need

no baking since it is vacuum packed.

4. The fourth electrode is BS EN 499 E352C, since it is a cellulose electrode it does not require

baking

50. Describe briefly

a. What are the principle reasons for specifying preheat and interpass temperatures in a

welding procedure?

b. how these temperature may be applied and controlled

c. Undercut has occurred along the top edge of a butt weld made by mma using 4mm

electrodes in the pc position in 25mm thick c/mn steel plate.

1. the preheat specified for the joint was 50°c

2. The welder proposes to apply a cosmetic pass, to correct the defect using a

2.5mm electrode should he used no preheat, the same preheat as the original

weld or a higher preheat for this repair? justify your answer

a. the principle reason for specifying preheat and interpass temperature in welding procedure is

to reduce internal stresses and solidification cracks during and after welding

b. Preheat: before starting of the welding heat the weld face with flame /coil till the

temperature reaches to the specified in the WPS then stop the heating and start the root



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welding. If preheat is locally applied it must extend to at least 75mm from the weld location

and be preferably measured on the opposite face to the one being welded. Interpass

Temperature: Once the root is welded allow the weld to cool the job to required interpass

temperature mentioned in the WPS. And maintained the temperature till the welding is

completed for subsequent passes. This can be maintained by automatic heating system or

manual heating. The temperature range can be measured by temple sticks (Temperature

indicating crayons or touch pyrometers or thermocouples)

c. Whatever preheat temperature mentioned in WPS has to be applied even for repair

procedures also to control the weld properties.

51. List five items of information that could be recorded on an ultrasonic test report, which would

be never present on radiographic report?

a. couplant type

b. probe details: type, angle, size and frequency

c. scanning method/type

d. correction sensitivity (+2db)

e. db (disable)

52. What is the consideration for qa/qc and inspection department if it is required to increase the

toughness and tensile strength of welds on a specific type of component?

a. Select high tensile and toughness welding consumables and alloying elements which will

increase the toughness and tensile strength of the component.

b. Select the welding parameters to control the heat input and followed by PWHT, this will

increase the tensile strength and toughness.

c. Select suitable welding process.

d. Select the suitable joint design.

e. Make sure all the required parameters are followed in production.

53. Without approval of drawing piping fabrication has been completed. What will be your course

of action?

a. Raise a non-conformance report.

b. Check with approved drawing. If minor changes noted, which will not affect the product

design requirement accept as it is provided a deviation request to be raised and approved.

c. The changes to be incorporated in the as build drawing.

d. If any major changes noted compared with approved drawing, to be refabricated as per

approved drawing.

e. Concern person involved, to issues a warning letter,

f. Conduct meeting with all inspectors and make them awareness, such as things recur in future.

54. During an audit no material certificate was found. How would you proceed?

If material test certificate not available ask the supplier to provide it. If it is not available with

supplier then material should be sent to lab for verifying its chemical and mechanical properties. The

lab report shall be attached instead of MTC.

55. Why it is desirable to seal in a lamination which is found to break during edge preparation?

Lamination is to be seal welded prior to welding because these areas will open up during welding due

to the heat produced while welding.

56. In a welder approval test should the procedure be explained to the welder?

No. it is not necessary.



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57. State the objectives of

a. A reduced transverse tensile test

b. A radius reduced transverse tensile test

A reduced transverse tensile test specimen assesses the tensile strength of the joint. A radius reduced

transverse tensile test specimen assesses the tensile strength of the weld metal.

58. What is the purpose of all weld tensile test and a radius reduced tensile test?

An all weld tensile test is to measure the tensile strength of electrodes/flux combination and quality of

weld metal as deposited.

A radius reduced tensile test is to assess the tensile strength of the weld metal.

59. State three factors which contribute to or control the mechanical properties of wrought steel?

Wrought steel grain much refinement during the hot/cold working and many defects are also removed.

This improvement is marked in the rolling direction but is usually results in a loss of strength through

the thickness.

60. What is the metallurgical production cause of lamellar tearing?

Lamellar tear could cause due to the presence of inclusions of sulphur, phosphorus and higher

percentage of carbon.

61. Does a wrought plate contain residual stresses due to manufacture?

Yes.

62. Give the composition for tool steel?

0.8%Cr, 1.0%Mn, 0.4%C, 0.3%Mo + Ti or Al + residuals

63. If bend test failure has occurred what would be your course of action?

Set aside the piece, take one more test piece and repeat the test. Assess the failure, whether the failure

is within the weld metal, weld junction or in the HAZ. A retest is very much needed in case of failure.

64. In which steels can it be expected that hydrogen induced cracking is found in the weld metal if

present at all?

High strength Mn steels

65. State four mechanisms of cracking, which may be found in the weld metal of ferritic steel

weldments?

a. Hydrogen induced cracking

b. Solidification cracking

c. Solidification pipe or void

d. Reheat cracking

66. State six methods of procedure to avoid solidification or centreline cracking?

a. Control the sulphur content

b. Use consumable with high manganese

c. Keep manganese-sulphide: carbon ratio as low as possible

d. Minimise restraints

e. Use low dilution process



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f. Weld joints are thoroughly cleaned immediately before welding

g. Maintain proper width to depth ratio

h. Use preheat

67. State three methods of procedure for avoiding solidification pipe in weld metal?

a. Correct depth to width ratio

b. Correct bead shape

c. Correct surface chilling effect due to

1. No slag covers process

2. Gas not heated

3. Flow rate too high

68. State the four factors which give rise to hydrogen cracking and suggest how control can be

exercised?

Factors which raise the risk of hydrogen crack

a. Stress

b. Hardness

c. Hydrogen and

d. Temperature

Control methods

Minimise stress by

a. Pre-setting

b. Back stitch welding or back skip welding

c. Stringer bead

d. Improve joint design (using double side joint instead of single joint)

e. Reduce restraints (J preparation – reduce included angle)

Minimize hardness by

a. Lower C.E

b. Limit heat input to 1.7kj/m ( avoid grain enlargement) use BS 5135 for preheat

Minimize hydrogen presence in three ways

a. Removal by a combination of preheat heat input (interpass temperature) and PWHT

b. Prevent entry by selection of process, consumable control, surface cleanliness and

welding technique (short arc)

c. Making hydrogen acceptable by control of formation of microstructure. Use austenitic or

nickel weld metal.

Temperature

a. Use post heating to maintain temperature and hydrogen defuse

b. Control the cooling rate

69. Why are austenitic SS electrodes sometimes specified for the welding of steels which might be

susceptible to hydrogen cracking?

Austenitic stainless steel can absorb more hydrogen than carbon steel.

70. In what way does the thickness of the metal influence hydrogen cracking?

Increases rate of cooling, larger volume of hydrogen and greater stress

71. In what steel group is PWHT almost always used?

Group 4 – high carbon steel



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72. The high carbon – no alloys the carbon content is critical. State the % of carbon which the

welding becomes very difficult?

Carbon content in excess of 0.45% becomes very difficult to weld.

73. State two results which may be expected from stress relief of welded products?

a. Will reduce internal stresses

b. Hydrogen is diffused

c. Grain refinement

74. State two types of cracking which can result from heat treatment?

a. Stress relief cracking or reheat cracking in steels containing chromium

b. Thermal cracking

75. What is the main advantage of using austenitic electrodes (for weld repair)?

The advantage of using austenitic stainless steel electrodes for repairs that hydrogen entering the

weld metal during welding is held in the weld metal and so will not diffuse in to the hardening HAZ.

Hence hydrogen cracking in the HAZ is unlikely to happen.

76. What is the main problem of weldability when using 18/8 type austenitic electrodes to repair

ferritic steels?

a. Solidification cracking

b. Weld decay

c. Reduces the corrosion resistance of weld metal

77. Why it is recommended that 29/10 is used for buttering and 18/8 is used to fill when using

austenitic electrodes for repair?

To avoid cracking, it is desirable (at least in joints with high restraint) to butter with an electrode

with high dilution tolerance and to make the closing weld with low strength electrodes.

78. Explain why the depth to width ratio of the bead is important?

To take care of residual stresses in welds which developed

a. Longitudinal along the weld

b. Across the weld

c. Through the weld

79. Outline metallurgical features of weld decay?

Weld decay: steels with high carbide forming characteristics such as these will react if the

temperature is allowed to dwell about 550°C. If this occurs then the chromium is no longer available

for combination with oxygen for the reformation of the protective oxide and corrosion may result.

Weld decay: depletion of chromium carbides in stainless steel.

80. State three methods of avoiding weld decay?

a. Reduce the carbon content i.e. SS316L

b. Heat treatment 1100°C and quench

c. To stabilize the steel by added Ti or Nb (to form carbides in preference to Cr carbides)



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81. Why backing gases are often specified when welding stainless steel?

a. To avoid contamination

b. To prevent formation of porosity

c. To avoid formation of oxides

82. Why carbon di oxide not normally uses as a shielding as when welding stainless steel?

To maintain low carbon

83. When stainless steel is welded to mild steel buttering is recommended why?

a. To seal carbon in

b. To stop dilution

84. When welding SS to a large root gap (3mm) are often used why?

Distortion closes gap

85. What is the essential feature of a stainless steel?

Chromium content (minimum 11%Cr is required to form SS and 29% is maximum) it react with

oxygen and produce chromium oxide which is protect the steel from rust.

86. What is the principle reason for the development of residual stresses in metals?

Metals contract during solidification and subsequent cooling, but if this contraction is prevented or

inhibited residual stresses will develop.

87. Name three directions of residual stresses in weld joints?

Normal welds develop residual stresses

a. Along the weld longitudinal residual stress

b. Across the weld transverse residual stress

c. Through the weld short transverse residual stress

88. What causes distortion in welded products?

The action of the residual stresses in the welded joints is to cause distortion

89. Give four consequences of using excessive current?

a. Excess spatter

b. Excess metal profile

c. Center line cracking

d. Undercuts

90. Give four consequences of using excessive arc length?

a. Unstable arc

b. Lack of penetration

c. Uneven profile bead

91. State the defects which occur when the tack weld is not correctly incorporated into the weld?

Lack of penetration or fusion



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92. Give three consequences of incorrect electrode angle?

a. Undercut

b. Spatter

c. Lack of penetration or fusion

93. Give one consequence of a) too fast travel speed and b) too slow travel speed?

a. Lack of penetration or fusion

b. Slag inclusion

94. What defect associated with excessively large size electrodes?

Lack of penetration

95. What defect is caused by inadequate cleaning between runs?

Slag inclusion

96. What defects can be caused by use of high welding speeds in saw process?

a. Lack of penetration or fusion

b. Undercut

97. What defects can be caused by the use of excessive gaps in saw process?

Excess penetration or burn through

98. What are likely causes of slag in the weld metal?

Slag inclusions, insufficient inter-run cleaning, poor bead profile (convex shape)

99. What adjustment must be made in submerged arc welding to reduce the bead width?

a. Lower the voltage

b. Increase the travel speed (if still within the parameters)

100. What defects can be caused by a plate having poorly cut joint preparation?

Lack of penetration or fusion

101. A weld is to be made on a close square butt joint with excessively high current, what defect

would occur?

Excess weld metal

102. What is the likely defect to be caused by an excessive flux burden?

Porosity

103. What is the critical level of hydrogen in a weld; can it be measured at any time or after stress

relief?

a. 5ml per 100gm of weld metal

b. All weld metal hydrogen diffusion test possible but not for the actual weldment



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104. Describe how and why hydrogen increases the incidence of hydrogen cracking?

Hydrogen in the weld/HAZ builds up internal pressure which could be higher than yield point of

metal low hydrogen would cause residual stresses.

105. Describe a heat treatment designed to remove hydrogen, when the treatment must is applied?

PWHT for 10-20-30 hours

106. Why basic hydrogen controlled electrodes must be kept at 150°C?

Prevents reabsorbing of moisture (Hydrogen)

107. What are the causes of lamellar tearing?

Lamellar tearing is a defect in the parent metal of a weldment due to high through thickness residual

stresses and a low through thickness strength and ductility of the material arising from elongated

inclusions and bands within the steel.

108. Where lamellar tearing is found in a weldment?

The crack is stepped and parallel to the surface of the plate.

109. How do bands (segregation) within steel influence the incidence of lamellar tearing?

Low through thickness strength and ductility are arising from bands within the steel and of high

residual stress.

110. Can susceptibility to lamellar tearing be assessed by ultrasonic NDE?

No. (But I feel yes)

111. Can lamellar tear be detected by NDE?

Before welding can’t be detected, after welding can be detected by ultrasonic NDE.

112. State three methods of avoiding lamellar tearing?

a. Reduce the residual stress by low restraints i.e. pre-setting rather than clamping by use of

gaps.

b. Buttering

c. Change the joint design

113. Name three types of stainless steel?

a. Martensitic

b. Austenitic

c. Ferritic

114. State the main weldability problem of the Fe11% chromium steels?

Hydrogen cracking

115. Name two methods of avoiding hydrogen cracking in martensitic stainless steel?

a. Control by hydrogen limitation i.e. the use of TIG welding process

b. Control by hardness, normal preheat and heat inputs, so select a very low carbon grade.



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116. Why do micro alloyed steels suffer hydrogen cracking in the weld metal?

In the micro alloyed steels the hydrogen is held in the weld metal and so hydrogen tends to be located

there also.

117. What are the factors which give rise to hydrogen cracking in alloyed steels?

In the HAZ the tensile residual stresses are across the weld, so the hydrogen cracks are along the

length of the weld. In the weld metal the tensile residual stresses are along the weld so the hydrogen

cracks are across the weld.

118. What are the two types of SAW flux?

a. Fused

b. Agglomerated

119. Why are the hydrogen cracks in the weld metal positioned across (transverse) the width of the

weld?

Hydrogen cracking is typically formed at right angles to the stress and is positively identified by its

transgranular appearance when viewed at X100 magnification. In ferritic steels hydrogen which

enters the weld metal during welding moves into the HAZ and due to, gas forming characteristics and

the residual stress, cracking may result.

120. State three items which may contribute to excessive hardness in a weldment?

a. Grain size

b. Quenching

c. C.E carbon and alloys

121. State two elements which cause centreline cracking?

a. Sulphur

b. Phosphorous

122. State the methods of minimizing solidification cracking?

a. Increase weld metal

b. Reduce the welding speed

c. Increase the manganese content of the weld pool

d. Use of cooling bars

e. Control the sulphur content

f. Keep manganese-sulphide: carbon ratio as low as possible

g. Minimise restraints

h. Use low dilution process

i. Weld joints are thoroughly cleaned immediately before welding

j. Maintain proper width to depth ratio

k. Use preheat

l. Reduce the amount of metal melted out of the parent metal by

1. skill/technique of the welder

2. reduce the amperage

123. A crack is observed along the centreline of the weld metal. Give two reasons for its formation?

When the weld metal has been deposited and its contracts during solidification it is vital that the

contraction and be fed by the depression of the outer surface

Contraction fed by the weld metal surface



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124. Give three reasons why pipe may form in the weld metal?

a. Premature freezing of the surface

b. Excessive depth of bead related to width

c. Bad bead shape

125. Give three reasons which contribute to premature freezing of the weld pool surface?

Premature of the surface due to

a. No slag covers i.e. the process

b. Gas not heated

c. Flow rate too high

126. Why ferritic material is usually added to austenitic electrodes?

To avoid centreline cracking

127. Why are austenitic electrodes used for welding carbon manganese steel?

To control the hydrogen level i.e. making the hydrogen level acceptable to avoid hydrogen cracking

128. When ferritic is added to electrodes what are two possible consequences?

It tends to avoid solidification cracking it does induce magnetism and makes the weld metal avoid so

reducing the corrosion resistance.

129. Why are small stringer beads usually recommended for SS weldments?

To reduce the level of heat input and avoid cracking

130. Describe the thermal conditions which give rise to weld decay in austenitic SS weldments

550 degree C for six seconds

131. State the special mechanical properties of 25%Cr in Fe alloys?

Ferritic SS is poor weldability due to cracking brittleness and temper embitterment. It is a single

phase alloy which is ferritic at all solid temperatures, so solidification cracking is a problem.

132. What is a specification?

Specification is a description of what to use in the making of a product i.e. type of material type of

process and type of consumables.

133. What is the extent of approval in a procedure?

Extent of approval is the range over which certain variables may alter without requiring new

procedure i.e. when there is a limitation in the welding qualification i.e.

a. The minimum and maximum diameter of the pipe that the test sample covers e.g. two inch

test piece would allow down 1” and upto 4”

b. The test may only allow welding of consumables in the same grouping, any other

consumable would require retest

c. The use of set electrical characteristics would not allow change without retest

d. The direction of welding if changed may require retest

e. Change of material to be tested would require retesting



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134. When is a procedure to be re-established?

When there is change in following essential variables

a. Change of welding process

b. Change of shielding gases or fluxes

c. Change of direction of welding

d. Change in parent metal to be welded

e. Change in joint design

f. Change in welding consumables

g. Change welding parameter range

135. State the four factors which must be satisfied for good welds:

Fusion welding factors

a. Fusion (melting) – the metal must be melted which requires a high intensity of heat

source.

b. The process must remove any oxide and other contaminants from the joint faces

c. Contamination by the atmosphere must be avoided

d. The welded joint must possess adequate properties

136. If visual examination of weld is not possible how will you ensure that the joint is okay?

It can be examined by appropriate NDT methods like RT or UT etc…

137. What are minor defects?

Misalignment (linear & angular), slag, porosity etc…

138. What are the major defects?

Lack of side wall fusion, overlap, lamination, lack of inter-run fusion, lack of penetration and

incomplete fusion

139. What is the course of action if the weldment has been accepted or rejected?

Inspection results to be recorded in an approved format. If the sample is rejected then the type of

defect and the location has to incorporated in a sketch and the report to be given for further remedial

action

140. What features of steel determine its weldability?

Carbon content & carbon equivalent

141. What is the main advantage of using 29/10 type austenitic electrodes to repair ferritic steels?

The defects of dilution will be lower the alloy content of the weld metal during cooling so it is

advisable to use it.

142. What is the difference between inspection for quality control and inspection for fitness for

purpose?



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143. Describe the relationship between the four essential factors involved in the formation of

hydrogen induced cold cracking.

144. Discuss the reasons for the existence of arc blow and state possible methods of minimising arc

blow.

145. Welder used cellulose electrode instead of low hydrogen electrode. Suggest corrective action

and your course of action in it?

a. Raise Non conformity report

b. Further investigation to be done to identify any other joints welded.

c. Analysis and identify the root cause for this incident

d. Check with approved drawing, product specification and welding procedures specifications.

If welding procedure specification available for this electrode and product design

requirement accept as it is provided a deviation request to be raised and approved.

e. If the specifications not allowed, the entire joints which is identified to be refabricated as per

approved specification.

f. The changes to be incorporated in the as built drawing.

g. Move welder for training and requalification

h. Issue a strong warning letter to Concern person involved.

i. Conduct meeting with all inspectors and make them awareness, such as things recur in future.

j. Document all the above and close the NCR

146. Name four commonly used NDT methods and list their advantages and disadvantages?

NDT METHOD ADVANTAGES DISADVANTAGES

Visual Inexpensive Highly portable Immediate

results Minimum training Minimum

part preparation

Surface discontinuities only Generally

only large discontinuities

Misinterpretation of scratches

Dye Penetrant Portability

Inexpensive

Sensitive to very small discontinuities

Simple to use

Quick results

Can be used on any non-porous

material

Low operator skill required

Locates surface breaking defects only

Little indication of depths

Direct visual detection of results

required

Penetrant may contaminate component

Surface preparation critical

Post cleaning required

Potentially hazardous chemicals



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Magnetic

Particle

Can be portable

Low cost

Sensitive to small discontinuities

Immediate results

Moderate skill required

Detects surface and subsurface

discontinuities

Relatively fast

No harm to test piece

Surface must be accessible

Rough surfaces interfere with test Part

preparation required (removal of

finishes and sealant, etc.)

Semi- directional requiring general

orientation of field to discontinuity

Ferro-magnetic materials only

Part must be demagnetized after test.

Eddy Current Portable

Detects surface and subsurface

discontinuities

Moderate speed

Immediate results

Sensitive to small discontinuities

Thickness sensitive

Accurate conductivity measurements

Can detect thorough several layers

Can be automated

Can detect thorough surface coatings

Little pre-clean required

Surface must be accessible to probe

Very susceptible to permeability

changes

Only works on conductive materials

Will not detect defects parallel to the

surface

Not suitable for large areas and /or

complex geometry

Signal interpretation required

No permanent record (unless

automated)

Skill and training required

Ultrasonic Portable

Inexpensive

Sensitive to very small discontinuities

Immediate results

Little part preparation

Wide range of materials and thickness

can be inspected

Surface must be accessible to probe

Rough surfaces interfere with test

Highly sensitive to sound beam

discontinuity orientation

High degree of skill required to set up

and interpret

Couplant usually required

Radiographic

Test

Permanent record

Internal flaws

Can be used on most materials

Direct image of flaws

Real – time imaging

Minimum part preparation

Health hazard

Sensitive to defect orientation

Limited ability to detect fine cracks

Access to both sides required

Limited by material thickness

High degree of skill and experience

required for exposure and

interpretation

Relatively slow

Depth of discontinuity not indicated

High capital outlay and running costs

147. Explain hardness and hardenability

a. Hardness is the property of a material that enables it to resist plastic deformation,

penetration, indentation, and scratching.

b. Hardenability is a term used to describe a material's ability to be hardened when it is exposed

to heat and then quenched, or cooled rapidly.


CSWIP 3.2.2 Questions

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