A – APPLICABLE O –   Marginally applicablity U- Not applicable



Porosity – Causes

  • Due to dissolved gases ( mostly H2 ) in the weld metal > the solubility limits when weld solidifies
  • H2 is supplied by gas shield, moisture in atmosphere, flux, coating, or water in the area of welding
  • Excess arc length
  • Moisture pickup in the low hydrogen electrodes
  • Surface contamination
  • Moist flux
  • Magnetic arc blow
  • Welding speed too high
  • Crater pipes
  • In TIG , MIG process loss of shielding, impure gas may causes porosity
  • More tendency in vertical & overhead position
  • At start and stop points due to unstable heat flow condition


  • Oxides and other non metallic solid materials entrapped between weld and base metal, or between weld metal and base metal


  • Loss of slag control due to poor manipulating technique and slag flooding advance of the arc because of the arc positioning
  • Incomplete inter-pass cleaning
  • Poor previous bead
  • Heavy mill scale or rust
  • Piece of unfused flux from electrodes with damaged coatings

Eddy current

Eddy current

An eddy current is an electrical current induced in a piece of metal due to the relative motion of a nearby magnet. Any time a magnet passes a metallic object, its magnetic field induces an electric current, which swirls around near the surface of the metal like an eddy in a river. This electric current creates its own magnetic field, which opposes the motion of the magnet.

  • This module is intended to present information on the NDT method of eddy current inspection.
  • Eddy current inspection is one of several methods that use the principal of “electromagnetism” as the basis for conducting examinations. Several other methods such as Remote Field Testing (RFT), Flux Leakage and Barkhausen Noise also use this principle.
  • Electromagnetic induction
  • Generation of eddy currents
  • Inspection applications
  • Equipment utilized in eddy current inspection
    • Probes/Coils
    • Instrumentation
    • Reference standard
  • Advantages and Limitations
  • Glossary of Terms

Electromagnetic Induction:

  • Eddy currents are created through a process called electromagnetic induction.
  • When alternating current is applied to the conductor, such as copper wire, a magnetic field develops in and around the conductor.
  • This magnetic field expands as the alternating current rises to maximum and collapses as the current is reduced to zero.
  • If another electrical conductor is brought into the proximity of this changing magnetic field, the reverse effect will occur. Magnetic field cutting through the second conductor will cause an “induced” current to flow in this second conductor. Eddy currents are a form of induced currents! 

Generation of Eddy Currents

Eddy currents are induced electrical currents that flow in a circular path. They get their name from “eddies” that are formed when a liquid or gas flows in a circular path around obstacles when conditions are right.

In order to generate eddy currents for an inspection a “probe” is used. Inside the probe is a length of electrical conductor which is formed into a coil.

Alternating current is allowed to flow in the coil at a frequency chosen by the technician for the type of test involved.

A dynamic expanding and collapsing magnetic field forms in and around the coil as the alternating current flows through the coil.

When an electrically conductive material is placed in the coil’s dynamic magnetic field electromagnetic, induction will occur and eddy currents will be induced in the material.

Eddy currents flowing in the material will generate their own “secondary” magnetic field which will oppose the coil’s “primary” magnetic field.

This entire electromagnetic induction process to produce eddy currents may occur from several hundred to several million times each second depending upon inspection frequency.

Eddy currents are strongest at the surface of the material and decrease in strength below the surface.  The depth that the eddy currents are only 37% as strong as they are on the surface is known as the standard depth of penetration or skin depth.  This depth changes with probe frequency, material conductivity and permeability

Inspection Data

  • There are three characteristics of the specimen that affect the strength of the induced eddy currents.
    • The electrical conductivity of the material
    • The magnetic permeability of the material
    • The amount of solid material in the vicinity of the test coil.
  • Information about the strength of the eddy currents within the specimen is determined by monitoring changes in voltage and/or current that occur in the coil.
  • The strength of the eddy currents changes the electrical impedance (Z) of the coil.
  • Impedance (Z) in an eddy current coil is the total opposition to current flow. In a coil, Z is made up of resistance (R) and inductive reactance (XL).


  • Resistance – The opposition of current flow, resulting in a change of electrical energy into heat or another form of energy.
  • Inductive Reactance (XL) – Resistance to AC current flow resulting from electromagnetic induction in the coil.
  • Impedance (Z) – The combined opposition to current flow resulting from inductive reactance and resistance.

Inspection Applications

One of the major advantages of eddy current as an NDT tool is the variety of  inspections that can be performed. The following slides depict some of the these capabilities.

Material Thickness Measurement

  • Thickness measurements are possible with eddy current inspection within certain limitations.
  • Only a certain amount of eddy currents can form in a given volume of material.
  • Therefore, thicker materials will support more eddy currents than thinner materials.
  • The strength (amount) of eddy currents can be measured and related to the material thickness.
  • Eddy current inspection is often used in the aviation industries to detect material loss due to corrosion and erosion.
  • Eddy current inspection is used extensively to inspect tubing at power generation and petrochemical facilities for corrosion and erosion.

Crack Detection

Crack detection is one of the primary uses of eddy current inspection. Cracks cause a disruption in the circular flow patterns of the eddy currents and weaken their strength.  This change in strength at the crack location can be detected.








Magnetic Particle Testing


Magnetic Particle Testing

Magnetic Particle Testing (Questions)


  1. Which of the following is not a property of magnetic lines of force?

(a) They form closed loops which do not cross

(b) The density increases with distance from the poles of a permanent magnet

(c) Hey are considered to have direction

(d) They seek paths of least magnetic resistance or least reluctance


  1. Surrounding an electromagnet, the magnetic field is strongest:

(a) Immediately after the current ceases to flow

(b) While the magnetizing current ceases to flow

(c) At the time the magnetic particles are applied to the part

(d) Just prior to current reversal


  1. The value of permeability is:

(a) A fixed value depending upon the type of material

(b) Between 1 and 100 for all ferromagnetic materials

(c) Between 0 and 10 for all ferromagnetic materials

(d) Dependent upon the amount of magnetizing force necessary to overcome



  1. The flux density of the magnetism induced by a coil is affected by:

(a) The coil size

(b) The current in the coil

(c) The number of turns in the coil

(d) All of the above


  1. How many turns of a coil will be needed to establish a longitudinal field in a steel

shaft that is 22.86 cm (9 inches) long and 7.62 cm (3 inches) in diameter? 3000

amperes magnetizing current is available, it is desired to magnetize the part in

accordance with the formula NI = 45,000/(L/D):

(a) 1

(b) 3

(c) 5

(d) 7

  1. How many ampere-turns are required to magnetize a part that is 40.6 cm (16 inches)

long and 5 cm (2 inches) in diameter?

(a) 9000 ampere-turns

(b) 5625 ampere-turns

(c) 2812 ampere-turns

(d) None of the above


  1. The lines of flux or force in a circularly magnetized ferromagnetic bar:

(a) Are aligned through the piece from the south to the north pole

(b) Are aligned through the piece from the north to the south pole

(c) Leave the south pole and enter the north pole

(d) Are contained within and around the part


  1. In which magnetizing method is the current passed directly through the part, thereby

setting up a magnetic field at right angles to the current flow?

(a) Longitudinal magnetization

(b) Coil magnetization

(c) Central conductor magnetization

(d) None of the above


  1. Which of the following is false concerning a magnetic field in and around a hollow

conductor as compared to that of a solid conductor of the same outside diameter when

both are of the same magnetic material, and when the applied current is the same?

(a) The field immediately outside the outer surface of the hollow conductor is


(b) The field gradient inside the hollow conductor is steeper

(c) The fields outside the conductors are the same

(d) The fields are the same at the centre



  1. The field in a section of ferromagnetic pipe being magnetized by means of a central

conductor is strongest at the:

(a) Ends of the pipe

(b) Outer surface of the pipe

(c) Inner surface of the pipe

(d) The field is uniform at all places

  1. For a 7.6 cm (3 inches) diameter bar how much current is needed to magnetize the bar

for the detection of longitudinal discontinuities:

(a) 5500 amperes

(b) 16500 amperes

(c) 1000 amperes

(d) 3000 amperes


  1. For detection of longitudinal discontinuities a 7.6 cm (3 inches) diameter bar is

magnetized in:

(a) The longitudinal direction

(b) The circular direction

(c) The clockwise direction

(d) None of the above directions


  1. A bar that is 5 cm (2 inches) by 10 cm (4 inches) by 30.5 cm (12 inches) is being

magnetized in the circular direction. About how many amperes are required using the

perimeter approach?

(a) 2200

(b) 4500

(c) 3800

(d) None of the above



  1. An advantage of AC is that:

(a) It is most readily available

(b) Equipment can be made lighter

(c) It leaves the part demagnetized

(d) All of the above


  1. When a magnetic field cuts across a crack:

(a) Electrons begin jumping back and forth across the crack

(b) The crack begins to heat up

(c) Magnetic poles form at the edges of the crack

(d) All of the above

  1. A disadvantage of AC current is that it:

(a) Cannot be used with dry powder

(b) Has poor penetrating power

(c) Can only provide low flux densities

(d) Cannot be used for residual magnetic particle testing


  1. What causes a leakage field in a steel bar?

(a) A crack

(b) Reversal of the magnetic field

(c) Paint on the surface

(d) All of the above


  1. An indication is a defect under which of the following conditions?

(a) If it is greater than 3.8 cm (1.5 inches) long

(b) If it exceeds the limits of a standard or specification

(c) If it is deep

(d) Under all of the above indications


  1. Paint will not affect the detection of a crack if:

(a) The paint is thick and the defect is subsurface

(b) The paint is thin and the crack is parallel to the direction of flux lines

(c) The crack is sharp and the paint is thin

(d) All of the above


  1. A magnetic particle indication is sharp and very fine; this suggests that the

discontinuity is:

(a) Subsurface seam

(b) A shallow, tight surface crack

(c) Porosity

(d) A deep crack

  1. Among the following, the best type of current for the detection of fatigue cracks is:

(a) Half-wave direct current

(b) Alternating current

(c) Direct current

(d) Half-wave alternating current


  1. Continuous magnetization provides the most sensitivity because:

(a) The magnetic particles are present while the part is being magnetized

(b) The magnetic field is greatest while the magnetizing current is on

(c) All of the above

(d) Neither of the above


  1. The sensitivity of magnetic particle testing is greatest when the discontinuity is:

(a) Parallel to the direction of the magnetic flux lines

(b) Perpendicular to the flow of the magnetizing current

(c) Perpendicular to the direction of the magnetic flux

(d) Perpendicular to the line between prods


  1. To provide reliability and reproducibility in magnetic particle testing, written

procedures should include:

(a) Location of the coil and current for each magnetization

(b) Requirements for ammeter calibration

(c) Type and concentration of the particles

(d) All of the above


  1. The magnetic particles are noticed to bunch in some fillet areas and stand on end on

the edge of a part being magnetized. These observations indicate that the:

(a) Particle concentration is too low

(b) Flux density is excessive

(c) Flux density is too low

(d) Magnetizing current should be changed form AC to DC

  1. Flux density is a measure of the number of magnetic flux lines perpendicular to an

area of cross-section. If a discontinuity is in the plane of the unit area, the strongest

magnetic article indication will be formed when the discontinuity is:

(a) Inclined at 45º to the flux lines

(b) Parallel to the flux lines

(c) 90º to the flux lines

(d) 135º to the flux lines


  1. Prods are being used to magnetize a weld area. When dry powder is dusted on the

surface, it is observed that there is no mobility of the particles. What is the most

probable reason for this observation?

(a) The magnetizing current is not high enough

(b) The flux density is too low

(c) DC is being used

(d) All of the above are possible reasons


  1. The current from portable high amperage units can be applied to the object using:

(a) Prods

(b) Cable coils

(c) Pre-wrapped coils

(d) All of the above


  1. How can parts be tested to determine if they have been adequately demagnetized?

(a) By bringing a suspended paper clip near the middle of the part

(b) By using a small horseshoe permanent magnet

(c) By using a small magnetometer held at a corner of the part

(d) By sprinkling some magnetic particles on the part


  1. The statement ‘magnetic particle testing can be applied to plated and painted parts’.

(a) May be true depending upon the thickness of the coating

(b) May be true if flux densities are increased to compensate for the coating


(c) Is true only for circular circumstances

(d) Both (a) and (b)

  1. A group of indications, some sharp and some broad and fuzzy, were found on an area

of a small forging. Demagnetization and re-inspection eliminated these indications.

What was the probable cause?

(a) Forging lap

(b) Magnetic writing

(c) Change in permeability

(d) Subsurface variation


  1. Magnetic particle testing is most likely to find subsurface discontinuities in:

(a) Soft steels with high permeability

(b) Soft steels with low permeability

(c) Hardened steels with low permeability

(d) Hardened steels with high permeability


  1. Which of the following is not an advantage of Magnetic Particle testing?

(a) Fast and simple to perform

(b) Can detect discontinuities filled with foreign material

(c) Most reliable for finding surface cracks in all types of material

(d) Works well through a thin coat of paint


  1. Which of the following does not represent a limitation of Magnetic Particle testing?

(a) The type of materials which may be effectively tested

(b) The directionality of the magnetic field

(c) The need for demagnetization

(d) The ability to detect discontinuities filled with foreign material


  1. The most effective NDT method for locating surface cracks in ferromagnetic materials


(a) Ultrasonic testing

(b) Radiographic testing

(c) Magnetic particles testing

(d) Liquid penetrant testing

  1. A discontinuity which is produced during solidification of the molten metal is called:

(a) Inherent

(b) Processing

(c) Service

(d) None of the above


  1. Pipe would be classified as what type of discontinuity?

(a) Inherent

(b) Processing

(c) Service

(d) None of the above


  1. A seam would be classified as what type of discontinuity?

(a) Inherent

(b) Processing

(c) Service

(d) None of the above


  1. A lamination in steel plate would be classified as what type of discontinuity?

(a) Inherent

(b) Processing

(c) Service

(d) None of the above


  1. An internal rupture caused by working steel at improper temperatures is called a:

(a) Lap

(b) Cold shut

(c) Forging burst

(d) Slag inclusion

  1. Cracks which are caused by alternating stresses above a critical level are called:

(a) Stress corrosion cracks

(b) Cycling cracks

(c) Critical cracks

(d) Fatigue cracks


  1. Cracks which are caused by a combination of tensile stress and corrosion are called:

(a) Stress corrosion cracks

(b) Cycling cracks

(c) Critical cracks

(d) Fatigue cracks


  1. Which of the following are ferromagnetic materials?

(a) Aluminium, iron, copper

(b) Iron, copper, nickel

(c) Copper, aluminium, silver

(d) Iron, cobalt, nickel


  1. The reverse magnetising force necessary to remove a residual magnetic field from a

test piece after it has been magnetically saturated is called:

(a) Hysteresis

(b) Coercive force

(c) Demagnetising flux

(d) Reverse saturation


  1. Magnetic lines of force enter and leave a magnet at:

(a) Saturation

(b) L/D ratios of greater than 4 to 1

(c) Flux concentration points

(d) Poles

  1. The ease with which a magnetic field can be established in a test piece is called:

(a) Reluctance

(b) Retentivity

(c) Permeability

(d) Electromagnetism


  1. Opposition to establishment of a magnetic field in a test piece is called:

(a) Reluctance

(b) Retentivity

(c) Permeability

(d) Electromagnetism


  1. The ability of a material to remain magnetic after the magnetising force is removed is


(a) Reluctance

(b) Retentivity

(c) Permeability

(d) Electromagnetism


  1. A magnetic field which is contained completely within the test piece is called a:

(a) Confined field

(b) Longitudinal field

(c) Circular field

(d) Saturated field


  1. Which of the following produces a circular field?

(a) Coil

(b) Head shot

(c) Yoke

(d) All of the above

2 d

3 a

4 d

5 c

6 b

7 d

8 d

9 c

10 c

11 d

12 b

13 c

14 d

15 c

16 b

17 a

18 b

19 c

20 b

21 b

22 c

23 c

24 d

25 b

26 c

27 d

28 d

29 c

30 a

31 b

32 a

33 c

34 d

36 a

37 a

38 b

40 c

41 d

42 a

43 d


45 d

46 c

47 a

48 b

49 c

50 d

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API 1169 Training

API 1169 Training

API 1169 – Pipeline inspector

API 1169 training

API 1169 training


  • This is an intensive 3 days course to prepare you to pass the API 1169 certification exam that has been recently launched by API.
  • The Technical Toolboxes, Inc. API – 1169 Exam Prep Course covers all information in the current API 1169 Pipeline Inspector Certification program “Body of Knowledge.”
  • This program has been developed to provide full coverage for the API certification exam in the context of the API multiple choice exam format.
  • The training will be invaluable in preparing you for the exam and providing you with an edge to passing.
  • Students will be assigned homework for evening study and practice questions and a practice exam will be given.
  • The instructor has taken and passed the exam. This 3 days class covers American Codes only.


Preparation to pass the API 1169 Exam.

Students should bring the following documents with them . TTI does not provide these for the students.:
After the description of the instructor below there is a link to the API 1169 Exam Publication Effectivity Sheet for 2016. Attendees bring everything on page 1. Technical Toolboxes will provide everything on page 2 in electronic format, or you may bring a hard copy if you wish. Below is the same list.

API 1169, Basic Inspection Requirements – New Pipeline Construction
All of API 1169 is applicable to the examination

API 1104, Welding of Pipeline and Related Facilities
ATTN: Test questions will be based on the following portions of the document only:
Section 3, Terms, Definitions, Acronyms, and Abbreviations
Section 4, Specifications
Section 5, Qualifications of Welding Procedures with Filler Metal Additions
Section 6, Qualification of Welders
Section 7, Design and Preparation of a Joint for Production Welding
Section 8, Inspection and Testing of Production Welds
Section 9, Acceptance Standards for NDT
Section 10, Repair and Removal of Weld Defects
Section 11, Procedures for Nondestructive Testing (NDT)

API 1110, Pressure Testing of Steel Pipelines –
Entire document is subject to testing with exception of the appendices

API Q1, Specification for Quality Programs
ATTN: Test questions will be based on the following portions of the document only:
Section 3: Terms, Definitions and Abbreviations
Section 4: Quality Management System Requirements
Section 5: Product Realization

ANSI Z49.1 Safety in Welding, Cutting, and Allied Processes
ATTN: Test questions will be based on the following portions of the document only:
Chapter 4: Protection of Personnel and the General Area
Chapter 5: Ventilation
Chapter 6: Fire Prevention and Protection
Chapter 8: Public Exhibitions and Demonstrations

ASME B31.4, Pipeline Transportation Systems for Liquids and Slurries
ATTN: Test questions will be based on the following portions of the document only:
Chapter I, Scope and Definitions
Chapter II, Design
Chapter III, Materials
Chapter V, Construction, Welding, and Assembly
Chapter VI, Inspection and Testing

ASME B31.8, Gas Transmission and Distribution Piping Systems
ATTN: Test questions will be based on the following portions of the document only:
General Provisions and Definitions
Chapter I, Materials and Equipment
Chapter II, Welding
Chapter III, Piping System Components and Fabrication Details
Chapter IV, Design, Installation and Testing
Chapter VI Corrosion Control

CGA (Common Ground Alliance) Best Practices, 11.0 Edition, March 2014
Entire document is subject to testing

INGAA, Construction Safety Guidelines
Natural Gas Pipeline Crossing Guidelines, Version 1, June, 2013 (http://www.ingaa.org/File.aspx?id=20405)
Section II – Definitions
CS-S-9 Pressure Testing (Hydrostatic/Pneumatic) Safety Guidelines, September, 2012 (http://www.ingaa.org/File.aspx?id=18981)
Entire document is subject to testing

ISO 9000:2005 Quality Management Systems – Fundamentals and Vocabulary 3rd edition (confirmed in 2009).
ATTN: Test questions will be based upon the Definitions Only

Technical Toolboxes will provide the below in electronic format. You may bring your own print version if you wish.

Who Should Attend:

Those planning on sitting for the API 1169 Certification Examination
Pipeline Welding Inspectors, Pipeline Welding Engineers,, Pipeline Welding Supervisors, NDT personnel, and those who wish to understand pipeline QA/QC.

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API 653 Questions and Answers

API 653 Questions and Answers


1)         __________ is a change from previous operating conditions involving different properties of the stored product such as specific gravity or corrosivity and / or different service conditions of temperature and / or pressure”

(a) Re-rating;                                                 (b) Change in service;

(c) Repair;                                                      (d) Reconstruction

REF : API-653, – 1.5.4

ANS : (b)

2)         A __________ is a device used to determine the image quality of a radiograph.

(a) A step wedge comparison film;                        (b) A densitometer;

(c) A penetramter                                         (d) All of the above.

REF : Section V, T-233

ANS : (c)

3)         A corroded roof plate is found to have an average thickness of 0.1″ measured over an area of 100 sq. inches. This area shall be :-

(a) Repaired or replaced;                            (b) Found to be acceptable;

(c) Repair is prohibited;                               (d) Replacement is mandated

REF : API-653,

ANS : (b)

4)         A double-welded butt joint is defined as :-

(a) A joint between two members that intersect at an angle between 0 degrees (a butt joint) and 90 degrees (a corner joint).

(b) A joint between two abutting parts lying in approximately the same plane that is welded from both sides.

(c) A joint whose size is equal to the thickness of the thinner jointed member.

(d) A joint  between two  overlapping members in which the overlapped edge is welded.

REF : 650

ANS : (b)

5)         An external floating roof shall be provided with atleast one manhole having a minimum inside diameter of __________ inches.

(a) 18;             (b) 15;             (c) 24;             (d) 30.

REF : 650 APP. C. 3.11

ANS : (c)

6)         A formal Visual External inspection by a qualified inspector shall be done atleast :-

(a) Every 5 years of ¼ CR life whichever is less

(b) Every 5 years of ½ CR life whichever is less

(c) Every 2 years

(d) Every 1- years or ¼ CR life whichever is greater

REF : 653

ANS : (a)

7)         A full hydrostatic test (when required) shall be held for __________ hours :-

(a) 24;             (b) 8;               (c) 18;             (d) 12

REF : 653

ANS : (a)

8)         A full-fillet weld is a weld that :-

(a) not less than 1/3 the thinner plate;

(b) the legs equal the thickness of the thinner plate;

(c) the largest isosceles triangle that can be inscribed within the cross section of the weld

(d) is atleast the thickness of the thicker plate

REF : API 650

ANS : (b)

9)         A hot tap in a 1.25″ thick tank with a minimum metal temperature of 65oF at time of hot tap, without having material toughness data is :-

(a) not permitted;                                          (b) permitted

(c) not enough information;                                   (d) not addressed by the code

REF : API 653 – 7.13.4 & Fig. 7-5

ANS : (a)

10)      A hydrostatic test for a relocated tank :-

(a) may be waived by the Owner / Operator;                   (b) is required;

(c) may be waived by the Inspector;                                 (d) is not necessary

REF : 653 (a)

ANS : (b)

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API 570 Questions

                                                     API 570 Questions

1.In the Barlow formula for determining pipe thickness, the term S stands for

  • Internal design gage pressure of the pipe in psi
  • Pressure design strength for internal pressure, in psi
  • Allowable unit stress at the design temperature, in psi
  • Maximum strain at the average operating temperature, in psi


2.At low pressure and temperature, the thickness determined by the Barlow formula may  be so small that  the pipe would have _________________ structural strength

  • Adequate
  • Insufficient
  • Ample
  • Good


3.A seamless NPS 12, A-106 Grade A pipe operators at 300 degrees F and 941 psi. The allowable stress is 16000 psi. Using the Barlow Equation, determine the thickness required for these conditions

  • 0.375”
  • 0.750”
  • 0.353”
  • 0.706”

4.A seamless NPS6, A-106 Grade A pipe operators at 300 degrees F and 941 psi. The allowable stress is 16000 psi . The owner-user specified that the pipe must have 0.1” allowed for corrosion allowance. Using the Barlow Equation, determine the thickness required for these conditions

  • 0.706”
  • 0.277”
  • 0.195”
  • 0.295”

5.A seamless NPS8, A-53 Grade B pipe operators at 700 degrees F and 700 psi. The allowable stress is 16500 psi . The pipe has been in service for 6 years. The original wall thickness of the pipe was 0.375”. The pipe wall now measure 0.30” Considering no structural requirements, estimate how long the piping can continue to operate and not be below the minimum thickness

  • 4.68 years
  • 9.8 years
  • 0 years; pipe now below minimum
  • 10.42 years


6.An Inspector finds a thin area in the body of a NPS 8 (8.625” O.D.) 600# gate valve. The valve’s body is made from ASTM A216 WCB material. The system operates at 700 psi and 750 degrees F. Using a corrosion allowance of 0.125”, what thickness must be present in order to continue to safely operate ( Hint 1.5 x 8.635 x 600/ 2 X 7000  +  0.125 )

  • 0.48”
  • 0.68”
  • 0.51”
  • 0.43”


7.If corrosion or erosion is anticipated for a valve, what should be done prior to installing the valve?

  • Severance thickness determinations should be made when the valves are installed so that the fretting rate and metal ruination can be determined
  • Retirement thickness measurement should be made after installation so that the fatigue rate and metal loss can be determined
  • Reference thickness measurements should be made when the valves are installed so that the corrosion rate and metal loss can be determined
  • Retina measurements of the macula should be made when the iris’ are installed so the optical rate and losses of perception can be determined



8.Which of the items listed below would NOT normally be contained in inspection records of piping?

  • Original date of installation, the specifications and strength levels of the materials used
  • Original vessel hydrotest pressures and conditions that the tests were performed  under
  • Original thickness measurement and the locations and dates of all subsequent readings
  • Calculated retirement thicknesses


9.Accurate records of a piping system make possible an evaluation of _____________ on any piping, valve or fitting

  • Computerization
  • Security and continuity
  • Cost and competency
  • Service life


10.You are working as an inspector. While reviewing a tabulation of thickness  data on a section of piping in non-corrosive or very low corrosive service, you  find the initial thickness reading of an inspection point to be 0.432” and marked nominal on a NPS 6 pipe. At the next inspection 12 months later you find a reading by ultrasonics of 0.378” at the same point. Twelve months later UT readings were taken and the thickness at the point was still 0.378” what would this mean to you?

  • No measurement was taken originally, the nominal thickness  was listed and the piping probably had an under-tolerance of 12.5%
  • There was an error made by the inspector at the installation or the inspector who UT” d the piping at the next inspection made an error
  • The UT machine that the inspector used during the 12 month inspection after installation was defective and not reading correctly
  • The pipe contractor or the installer put the wrong schedule piping in service


11.You are working as an inspector. While reviewing a tabulation of thickness data on a section of piping, you find the letter “C” marked under a column headed by the word METHOD. What does the “C” indicate?

  • The  inspection temperature of the pipe was COLD
  • The thickness measurement was made by an inspector with  ID OF “C”
  • The thickness measurement was taken with calipers
  • The thickness measurement was CONFIRMED  by a second party


12.Which of the following is not an important function of an accurate sketch?

  • Assist in determining future locations that urgently require examinations
  • Identifying systems and circuits in terms of location,  size, material etc
  • Serve as field data sheets
  • None of the above


13.The Wenner 4-Pin methods, the soil bar, and the soil box do not represent  methods of determining

  • Holidays
  • Pipe-to-soil potentials
  • Cathodic protection acceptability
  • All of the above


14.The total resistivity for a wenner 4-Pin test that utilizes pins spaced 2 feet apart and a 6 “R” factor is:

  • 2298 ohm/cm
  • 3500 ohm/cm
  • 6000 ohm/cm
  • 8000 ohm/cm


15.Which of the following is not a consideration when using a soil bar?

  • Using a standard prod bar
  • Avoiding the addition of water
  • Applying pressure on the soil bar after injection
  • None of the above


16.Which of the following is a consideration when using a soil box

  • Depth of pins less than 4% of spacing
  • Ensuring the soil has dried out before testing
  • Avoiding contamination of the sample during handling and storage
  • All of the above
1 C
2 B
3 A
4 A
5 B
6 C
7 C
8 B
9 D
10 A
11 C
12 D
13 D
14 A
15 D
16 C


API 570 Piping Inspection |API Training in India

API 570 Piping Inspection

API 570 Piping Inspection is an inspection code developed by the American Petroleum Institute that covers the in-service inspection, repair, alteration, and relating activities for piping systems and their associated pressure relieving devices in the petroleum and chemical process industries.

API 570 Piping Inspection

It specifically applies to metallic piping and those plastic ones that are either fiberglass reinforced (FRP) or glass reinforced (GRP).

API 570 Piping Inspection establishes requirements and guidelines that allow owners or users of piping systems to maintain the safety and mechanical integrity of their systems after they have been placed into service.

While it was primarily intended for those systems in the petroleum and chemical process industries, this code can be applied to any piping system where practical.

This code also covers pipelines that carry process fluids, hydrocarbons, and other flammable or toxic fluids.

Some specific fluids covered include: petroleum and chemical products, natural gas, flare systems, sour water, high pressure gasses and several others.

This standard specifically does not govern the construction of pipelines or set forth any standards relating to them before they are placed into service.

In the event of any conflicting standards of regulations, API 570 should take precedence in cases where it is the more stringent requirement.

The American Petroleum Institute offers API 570 Piping Inspection certification training and exams for inspectors.

To take the exam, a minimum amount of experience and education are required. It can vary, but in general the more education one has, the less experience is required to qualify for the exam.

Certification under API 510 is valid for a three year term at the end of which it must be renewed.

API 570 – Piping Inspector:

Corrosion rates and inspection intervals – Welds joint – Quality factors and casting factors – Internal pressure minimum thickness of pipe – Pressure testing – Impact testing – Preheating and heat treatment requirements – Thermal expansion – Minimum wall thickness and working pressure for flanges – Minimum required thickness of a permanent blank – Non destructive examination – Damage mechanisms – Welding metallurgy – Inspection of piping components .



Welding Terms Glossary

Welding Terms Glossary

Abrasive – Slag used for cleaning or surface roughening.

Active Flux – Submerged-arc welding flux from which the amount of elements deposited in the weld metal is dependent upon welding conditions, primarily arc voltage.

Adhesive Bonding – Surfaces, solidifies to produce an adhesive bond.

Air Carbon Arc Cutting – An arc cutting process in which metals to be cut are melted by the heat of carbon arc and the molten metal is removed by a blast of air.

All-Weld-Metal Test Specimen – A test specimen with the reduction section composed wholly of weld metal.

Alloying – Adding a metal or alloy to another metal or alloy.

Alternating Current (AC) – Electric current that reverses direction periodically, usually many times per second.

Annealed Condition – A metal or alloy that has been heated and then cooled to remove internal stresses and to make the material less brittle.

Arc Blow – The deflection of an electric arc from its normal path because of magnetic forces.

Arc Cutting – A group of thermal cutting processes that severs or removes metal by melting with the heat of an arc between an electrode and the work piece.

Arc Force – The axial force developed by an arc plasma.

Arc Gouging – An arc cutting procedure used to form a bevel or groove.

Arc Length – The distance from the tip of the electrode or wire to the work piece.

Arc Time – The time during which an arc is maintained.

Arc Voltage – The voltage across the welding arc.

Arc Welding – A group of welding processes which produces coalescence of metals by heating them with an arc, with or without the application of pressure and with or without the use of filler metal.

Arc Welding Deposition Efficiency (%) – The ratio of the weight of filler metal deposited to the weight of filler metal melted.

Arc Welding Electrode – A part of the welding system through which current is conducted that ends at the arc.

As-Welded – The condition of the weld metal, after completion of welding, and prior to any subsequent thermal or mechanical treatment.

Atomic Hydrogen Welding – An arc welding process which produces coalescence of metals by heating them with an electric arc maintained between two metal electrodes in an atmosphere of hydrogen.

Austenitic – Composed mainly of gamma iron with carbon in solution.

Autogenous Weld – A fusion weld made without the addition of filler metal.

Automatic – The control of a process with equipment that requires little or no observation of the welding and no manual adjustment of the equipment controls.

Back Gouging – The removal of weld metal and base metal from the other side of a partially welded joint to assure complete penetration upon subsequent welding from that side.

Backfire – The momentary recession of the flame into the welding or cutting tip followed by reappearance or complete extinction of the flame.

Backhand Welding – A welding technique where the welding torch or gun is directed opposite to the direction of welding.

Backing – A material (base metal, weld metal, or granular material) placed at the root of a weld joint for the purpose of supporting molten weld metal.

Backing Gas – A shielding gas used on the underside of a weld bead to protect it from atmospheric contamination.

Backing Ring – Backing in the form of a ring, generally used in the welding of pipe.

Back-Step Sequence – A longitudinal sequence in which the weld bead increments are deposited in the direction opposite to the progress of welding the joint.

Base Metal (material) – The metal (material) to be welded, brazed, soldered, or cut. See also substrate.

Bend Radius – Radius of curvature on a bend specimen or bent area of a formed part. Measured on the inside of a bend.

Bevel – An angled edge preparation.

Blanking – Process of cutting material to size for more manageable processing.

Braze Welding – A method of welding by using a filler metal, having a liquidus above 840 °F (450 °C) and below the solidus of the base metals.

Brazing – A group of welding processes which produces coalescence of materials by heating them to a suitable temperature and by using a filler metal, having a liquidus above 840 °F (450 °C) and below the solidus of the base materials. The filler metal is distributed between the closely fitted surfaces of the joint by capillary attraction.

Burr – A rough ridge, edge, protuberance, or area left on metal after cutting, drilling, punching, or stamping.

Buttering – A form of surfacing in which one or more layers of weld metal are deposited (for example, a high alloy weld deposit on steel base metal which is to be welded to a dissimilar base metal). The buttering provides a suitable transition weld deposit for subsequent completion of the butt weld on the groove face of one member.

Butt Joint – A joint between two members lying in the same plane.

Camber – Deviation from edge straightness, usually the greatest deviation of side edge from a straight line.

Cap Pass – The final pass of a weld joint.

Carrier Gas – In thermal spraying, the gas used to carry powdered materials from the powder feeder or hopper to the gun.

Capillary Action – The action by which the liquid surface is elevated or depressed where it contacts a solid because the liquid molecules are attracted to one another and to the solid molecules.

Cladding – A thin (> 0.04″) layer of material applied to the base material to improve corrosion or wear resistance of the part.

Clad Metal – A composite metal containing two or three layers that have been welded together. The welding may have been accomplished by roll welding, arc welding, casting, heavy chemical deposition, or heavy electroplating.

Coalescence – The uniting of many materials into one body.

Coherent – Moving in unison.

Cold Lap – Incomplete fusion or overlap.

Collimate – To render parallels to a certain line or direction.

Complete Fusion – Fusion that has occurred over the entire base material surfaces intended for welding, and between all layer and passes.

Complete Joint Penetration – Joint penetration in which the weld metal completely fills the groove and is fused to the base metal throughout its total thickness.

Constant Current Power Source – An arc welding power source with a volt-ampere output characteristic that produces a small welding current change from a large arc voltage change.

Constant Voltage Power Source – An arc welding power source with a volt-ampere output characteristic that produces a large welding current change from a small arc voltage change.

Contact Tube – A system component that transfers current from the torch gun to a continuous electrode.

Contact Resistance – The resistance in ohms between the contacts of a relay, switch, or other device when the contacts are touching each other.

Contact Tube – A device which transfers current to a continuous electrode

Covered Electrode – A filler metal electrode used in shielded metal-arc welding, consisting of a metal-wire core with a flux covering.

Crater – In arc welding, a depression on the surface of a weld bead.

Crater Crack – A crack in the crater of a weld bead.

Cryogenic – Refers to low temperatures, usually -200 o (-130 o) or below.

Cutting Attachment – A device for converting an oxy-fuel gas-welding torch into an oxy-fuel cutting torch.

Cylinder – A portable container used for transportation and storage of a compressed gas.

Defect – A discontinuity or discontinuities that by nature or accumulated effect (for example, total crack length) renders a part or product unable to meet minimum applicable acceptance standards or specifications.

Density – The ratio of the weight of a substance per unit volume; e.g. mass of a solid, liquid, or gas per unit volume at a specific temperature.

Deposited Metal – Filler metal that has been added during welding, brazing or soldering.

Deposition Efficiency – In arc welding, the ratio of the weight of deposited metal to the net weight of filler metal consumed, exclusive of stubs.

Deposition Rate – The weight of material deposited in a unit of time. It is usually expressed as pounds/hour (lb/h) or kilograms per hour (kg/h).

Depth of Fusion – The distance that fusion extends into the base metal or previous pass from the surface melted during welding.

Dew Point – The temperature and pressure at which the liquefaction of a vapor begins. Usually applied to condensation of moisture from the water vapor in the atmosphere.

Dilution – The change in chemical composition of a welding filler material caused by the admixture of the base material or previously deposited weld material in the deposited weld bead. It is normally measured by the percentage of base material or previously deposited weld material in the weld bead.

Direct Current – Electric current that flows in one direction.

Direct Current Electrode Negative (DCEN) – The arrangement of direct current arc welding leads in where the electrode is the negative pole and work-piece is the positive pole of the welding arc.

Direct Current Electrode Positive (DCEP) – The arrangement of direct current arc welding leads in where the electrode is the positive pole and work-piece is the negative pole of the welding arc.

Duty Cycle – The percentage of time during a time period that a power source can be operated at rated output without overheating.

Dynamic Load – A force exerted by a moving body on a resistance member, usually in a relatively short time interval.

Electrode Extension – The length of electrode extending beyond the end of the contact tube.

Electrode Holder – A welding process that produces coalescence of metals with the heat obtained from a concentrated beam composed primarily of high velocity electrons

Electron Beam Welding – A welding process producing coalescence of metals with molten slag which melts the filler metal and the surfaces of the work to be welded. The molten weld pool is shielded by the slag, which moves along the full cross section of the joint as welding progresses.

Electroslag Welding – A welding process producing coalescence of metals with molten slag which melts the filler metal and the surfaces of the work to be welded. The molten weld pool is shielded by the slag, which moves along the full cross section of the joint as welding progresses.

Eutectoid Composition – A mixture of phases whose composition are determined by the eutectoid point in the solid region of an equilibrium diagram and whose constituents are formed by eutectoid reaction.

Facing Surface – The surfaces of materials in contact with each other and joined or about to be joined together.

Filler Material – The material to be added in making a welded, brazed, or soldered joint.

Fillet Weld – A weld of approximately triangular cross section that joins two surfaces approximately at right angles to each other in a lap joint, T-joint, or corner joint.

Filter Plate – A transparent plate tinted in varying darkness for use in goggles, helmets and hand shields to protect workers from harmful ultraviolet, infrared and visible radiation.

Flame Spraying – A thermal spraying process using an oxy-fuel gas flame as the source of heat for melting the coating material.

Flammable Range – The range over which a gas at normal temperature (NTP) forms a flammable mixture with air.

Flat Welding Position – A welding position where the weld axis is approximately horizontal and the weld face lies in an approximately horizontal plane.

Flashback – A recession of the flame into or back of the mixing chamber of the torch.

Flashback Arrestor – A device to limit damage from a flashback by preventing the propagation of the flame front beyond the point at which the arrestor is installed.

Flashing – The violent expulsion of small metal particles due to arcing during flash butt welding.

Flux – Material used to prevent, dissolve, or facilitate removal of oxides and other undesirable surface substances.

Flux Cored Arc Welding (FCAW) – An arc welding process that produces coalescence of metals by means of tubular electrode. Shielding gas may or may not be used.

Friction Welding – A solid welding process which produces coalescence of material by the heat obtained from a mechanically induced sliding motion between rubbing surfaces. The work parts are held together under pressure.

Friction Stir Welding – A solid-state welding process, which produces coalescence of material by the heat obtained from a mechanically induced rotating motion between tightly butted surfaces. The work parts are held together under pressure.

Forehand Welding – A welding technique where the welding torches or gun is pointed toward the direction of welding.

Fusion – The melting together of filler metal and base metal (substrate), or of base metal only, which results in coalescence.

Gas Metal Arc Welding (GMAW) – An arc welding process where the arc is between a continuous filler metal electrode and the weld pool. Shielding from an externally supplied gas source is required.

Gas Tungsten Arc Welding (GTAW) – An arc welding process where the arc is between a tungsten electrode (non-consumable) and the weld pool. The process is used with an externally supplied shielding gas.

Gas Welding – Welding with the heat from an oxy-fuel flame, with or without the addition of filler metal or pressure.

Globular-Spray Transition Current – In GMAW/Spray Transfer, the value at which the electrode metal transfer changes from globular to spray mode as welding current increases for any given electrode diameter.

Globular Transfer – In arc welding, a type of metal transfer in which molten filler metal is transferred across the arc in large droplets.

Groove Weld – A weld made in a groove between two members. Examples: single V, single U, single J, double bevel etc.

Hard-Facing – Surfacing applied to a workplace to reduce wear.

Heat-Affected Zone – That section of the base metal, generally adjacent to the weld zone, whose mechanical properties or microstructure, have been altered by the heat of welding.

Hermetically Sealed – Airtight. Heterogenous – A mixture of phases such as: liquid-vapor or solid-liquid-vapor.

Hot Crack – A crack formed at temperatures near the completion of weld solidification.

Hot Pass – In pipe welding, the second pass which goes over the root pass.

Inclined Position – In pipe welding, the pipe axis angles 45 degrees to the horizontal position and remains stationary.

Incomplete Fusion – A weld discontinuity where fusion did not occur between weld metal and the joint or adjoining weld beads.

Incomplete Joint Penetration – A condition in a groove weld where weld metal does not extend through the joint thickness.

Inert Gas – A gas that normally does not combine chemically with the base metal or filler metal.

Intergranular Penetration – The penetration of filler metal along the grain boundaries of a base metal.

Interpass Temperature – In a multi-pass weld, the temperature of the weld area between passes.

Ionization Potential – The voltage required to ionize (add or remove an electron) a material.

Joint – The junction of members or the edges of members that are to be joined or have been joined.

Kerf – The width of the cut produced during a cutting process.

Keyhole – A technique of welding in which a concentrated heat source penetrates completely through a work-piece forming a hole at the leading edge of the molten weld metal. As the heat source progresses, the molten metal fills in behind the hole to form the weld bead.

Lap Joint – A joint between two overlapping members in parallel planes.

Laser – A device that provides a concentrated coherent light beam. Laser is an acronym for Light Amplification by Stimulated Emission of Radiation.

Laser Beam Cutting – A process that severs material with the heat from a concentrated coherent beam impinging upon the work-piece.

Laser Beam Welding – A process that fuses material with the heat from a concentrated coherent beam impinging upon the members to be joined.

Leg of Fillet Weld – The distance from the root of the joint to the toe of the fillet weld.

Liquidus – The lowest temperature at which a metal or an alloy is completely liquid.

Mandrel – A metal bar serving as a core around which other metals are cast, forged, or extruded, forming a true, center hole.

Manifold – A multiple header for interconnection of gas or fluid sources with distribution points.

Martensitic – An interstitial, super-saturated solid solution of carbon in iron, having a body-centered tetragonal lattice.

Manual Welding – A welding process where the torch or electrode holder is manipulated by hand. MIG – See Gas Metal Arc Welding (GMAW).

Mechanical Bond – The adherence of a thermal-spray deposit to a roughened surface by particle interlocking.

Mechanized Welding – Welding with equipment where manual adjustment of controls is required in response to variations in the welding process. The torch or electrode holder is held by a mechanical device.

Melting Range – The temperature range between solidus and liquidus.

Melt-Through – Visible reinforcement produced on the opposite side of a welded joint from one side.

Metal Cored Arc Welding – A tubular electrode process where the hollow configuration contains alloying materials.

Metal Cored Electrode – A composite tubular electrode consisting of a metal sheath and a core of various powdered materials, producing no more than slag islands on the face of the weld bead. External shielding is required.

Molecular Weight – The sum of the atomic weights of all the constituent atoms in the molecule of an element or compound.

Monochromatic – The color of a surface that radiates light, containing an extremely small range of wavelengths.

Neutral Flame – An oxy-fuel gas flame that is neither oxidizing nor reducing.

Open-Circuit Voltage – The voltage between the output terminals of the welding machine when no current is flowing in the welding circuit.

Orifice Gas – In plasma arc welding and cutting, the gas that is directed into the torch to surround the electrode. It becomes ionized in the arc to form the plasma and issues from the orifice in the torch nozzle as the plasma jet.

Oxidizing Flame – An oxy-fuel gas flame having an oxidizing effect (excess oxygen).

Peening – The mechanical working of metals using impact blows.

Pilot Arc – A low current continuous arc between the electrode and the constricting nozzle of a plasma torch that ionizes the gas and facilitates the start of the welding arc.

Plasma – A gas that has been heated to at least partially ionized condition, enabling it to conduct an electric current.

Plasma Arc Cutting (PAC) – An arc cutting process using a constricted arc to remove the molten metal with a high-velocity jet of ionized gas from the constricting orifice.

Plasma Arc Welding (PAW) – An arc welding process that uses a constricted arc between a non-consumable electrode and the weld pool (transferred arc) or between the electrode and the constricting nozzle (non-transferred arc). Shielding is obtained from the ionized gas issuing from the torch.

Plasma Spraying (PSP) – A thermal spraying process in which a non-transferred arc is used to create an arc plasma for melting and propelling the surfacing material to the substrate.

Plug Weld – A circular weld made through a hole in one member of a lap or T joint.

Porosity – A hole-like discontinuity formed by gas entrapment during solidification.

Post-Heating – The application of heat to an assembly after welding, brazing, soldering, thermal spraying, or cutting operation.

Postweld Heat Treatment – Any heat treatment subsequent to welding.

Preform – The initial press of a powder metal that forms a compact.

Preheating – The application of heat to the base metal immediately before welding, brazing, soldering, thermal spraying, or cutting.

Preheat Temperature – The temperature of the base metal immediately before welding is started.

Procedure Qualification – Demonstration that a fabricating process, such as welding, made by a specific procedure can meet given standards.

Pull Gun Technique – Same as backhand welding.

Pulsed Power Welding – Any arc welding method in which the power is cyclically programmed to pulse so that the effective but short duration values of a parameter can be utilized. Such short duration values are significantly different from the average value of the parameter. Equivalent terms are pulsed voltage or pulsed current welding.

Pulsed Spray Welding – An arc welding process variation in which the current is pulsed to achieve spray metal transfer at average currents equal to or
less than the globular to spray transition current.

Push Angle – The travel angle where the electrode is pointing in the direction of travel.

Rake Angle – Slope of a shear knife from end to end.

Reducing Flame – A gas flame that has a reducing effect, due to the presence of excess fuel.

Reinforcement – Weld metal, at the face or root, in excess of the metal necessary to fill the joint.

Residual Stress – Stress remaining in a structure or member, as a result of thermal and/or mechanical treatment. Stress arises in fusion welding primarily because the melted material contracts on cooling from the solidus to room temperature.

Reverse Polarity – The arrangement of direct current arc welding leads with the work as the negative pole and the electrode as the positive pole of the welding arc.

Root Opening – A separation at the joint root between the work pieces.

Root Crack – A crack at the root of a weld.

Self-Shielded Flux Cored Arc Welding (FCAW-S) – A flux-cored arc welding process variation in which shielding gas is obtained exclusively from the flux within the electrode.

Shielded Metal Arc Welding (SMAW) – A process that welds by heat from an electric arc, between a flux-covered metal electrode and the work. Shielding comes from the decomposition of the electrode covering.

Shielding Gas – Protective gas used to prevent atmospheric contamination.

Soldering – A joining process using a filler metal with a liquidus less than 840 °F and below the solidus of the base metal.

Solid State Welding – A group of welding processes which produces coalescence at temperatures essentially below the melting point of the base materials being joined, without the addition of a brazing filler metal. Pressure may of may not be used.

Solidus – The highest temperature at which a metal or alloy is completely solid.

Spatter – Metal particles expelled during welding that do not form a part of the weld.

Spray Transfer – In arc welding, a type of metal transfer in which molten filler metal is propelled axially across the arc in small droplets.

Standard Temperature and Pressure (STP) – An internationally accepted reference base where standard temperature is 0 °C (32 °f) and standard pressure is one atmosphere, or 14.6960 psia.

Stick-Out – The length of unmelted electrode extending beyond the end of the contact tube in continuous welding processes.

Straight Polarity – Direct current arc welding where the work is the positive pole.

Stress Relief Heat Treatment – Uniform heating of a welded component to a temperature sufficient to relieve a major portion of the residual stresses.

Stress Relief Cracking – Cracking in the weld metal or heat affected zone during post-weld heat treatment or high temperature service.

Stringer Bead – A weld bead made without transverse movement of the welding arc.

Submerged Arc Welding – A process that welds with the heat produced by an electric arc between a bare metal electrode and the work. A blanket of granular fusible flux shields the arc.

Substrate – Any material upon which a thermal-spray deposit is applied.

Synergistic – An action where the total effect of two active components in a mixture is greater than the sum of their individual effects.

Tack Weld – A weld made to hold parts of a weldment in proper alignment until the final welds are made.

Tenacious – Cohesive, tough.

Tensile Strength – The maximum stress a material subjected to a stretching load can withstand without tearing.

Thermal Conductivity – The quantity of heat passing through a material.

Thermal Spraying – A group of processes in which finely divided metallic or non-metallic materials are deposited in a molten or semimolten condition to form a coating.

Thermal Stresses – Stresses in metal resulting from non-uniform temperature distributions.

Thermionic – The emission of electrons as a result of heat.

Throat – In welding, the area between the arms of a resistance welder. In a press, the distance from the slide centerline to the frame, of a gap-frame press.

TIG Welding – See Gas Tungsten Arc Welding (GTAW).

Torch Standoff Distance – The dimension from the outer face of the torch nozzle to the work piece.

Transferred Arc – In plasma arc welding, a plasma arc established between the electrode and the work-piece.

Underbead Crack – A crack in the heat-affected zone generally not extending to the surface of the base metal.

Undercut – A groove melted into the base plate adjacent to the weld toe or weld root and left unfilled by weld metal.

Vapor Pressure – The pressure exerted by a vapor when a state of equilibrium has been reached between a liquid, solid or solution and its vapor. When the vapor pressure of a liquid exceeds that of the confining atmosphere, the liquid is commonly said to be boiling.

Viscosity – The resistance offered by a fluid (liquid or gas) to flow.

Weldability – The capacity of a material to be welded under the fabrication conditions imposed into a specific, suitably designed structure and to perform satisfactorily in the intended service.

Weld Bead – The metal deposited in the joint by the process and filler wire used.

Welding Leads – The work piece lead and electrode lead of an arc welding circuit.

Welding Wire – A form of welding filler metal, normally packaged as coils or spools, that may or may not conduct electrical current depending upon the welding process used.

Weld Metal – The portion of a fusion weld that has been completely melted during welding.

Weld Pass – A single progression of welding along a joint. The result of a pass is a weld bead or layer.

Weld Pool – The localized volume of molten metal in a weld prior to its solidification as weld metal.

Weld Puddle – A non-standard term for weld pool.

Weld Reinforcement – Weld metal in excess of the quantity required to fill a joint.

Welding Sequence – The order in which weld beads are deposited in a weldment.

Wetting – The phenomenon whereby a liquid filler metal or flux spreads and adheres in a thin continuous layer on a solid base metal.

Wire Feed Speed – The rate at which wire is consumed in welding.

Work Lead – The electric conductor between the source of arc welding current and the work.

Dye penetrant inspection , liquid penetrant inspection or Penetrant Testing

Dye penetrant inspection:

  • Dye penetrant inspection (DPI), also called liquid penetrant inspection (LPI) or Penetrant Testing  (PT), is a widely applied and low-cost inspection method used to locate surface-breaking defects in all non – porus materials (metals, plastics, or ceramics).
  • The penetrant may be applied to all non-ferrous materials and ferrous materials, although for ferrous components magnetic particle inspection is often used instead for its subsurface detection capability.
  • LPI is used to detect casting, forging and welding surface defects such as hairline cracks, surface porosity, leaks in new products, and fatigue cracks on in-service components.


  • Dye penetrant inspection (DPI)  is based upon capillary action, where low surface tension fluid penetrates into clean and dry surface-breaking discontinuities.
  • Penetrant may be applied to the test component by dipping, spraying, or brushing.
  • After adequate penetration time has been allowed, the excess penetrant is removed and a developer is applied.
  • The developer helps to draw penetrant out of the flaw so that an invisible indication becomes visible to the inspector.
  • Inspection is performed under ultraviolet or white light, depending on the type of dye used – flurescent or nonfluorescent (visible).

Inspection Steps:

Below are the main steps of Dye penetrant inspection (DPI), liquid penetrant inspection (LPI) or Penetrant Testing  (PT):

1. Pre-cleaning:

  • The test surface is cleaned to remove any dirt, paint, oil, grease or any loose scale that could either keep penetrant out of a defect, or cause irrelevant or false indications. Cleaning methods may include solvents, alkaline cleaning steps, vapor degreasing, or media blasting.
  • The end goal of this step is a clean surface where any defects present are open to the surface, dry, and free of contamination.
  • Note that if media blasting is used, it may “work over” small discontinuities in the part, and an etching bath is recommended as a post-blasting treatment.

Dye penetrant inspection (DPI)

Application of the penetrant to a part in a ventilated test area.

2. Application of Penetrant:

  • The penetrant is then applied to the surface of the item being tested.
  • The penetrant is allowed “dwell time” to soak into any flaws (generally 5 to 30 minutes).
  • The dwell time mainly depends upon the penetrant being used, material being tested and the size of flaws sought.
  • As expected, smaller flaws require a longer penetration time.
  • Due to their incompatible nature one must be careful not to apply solvent-based penetrant to a surface which is to be inspected with a water-washable penetrant.

3. Excess Penetrant Removal:

  • The excess penetrant is then removed from the surface.
  • The removal method is controlled by the type of penetrant used.
  • Water-washable, solvent-removable, Liphopilic post-emulsifiable, or hydrophilic  post-emulsifiable are the common choices.
  • Emulsifiers represent the highest sensitivity level, and chemically interact with the oily penetrant to make it removable with a water spray.
  • When using solvent remover and lint-free cloth it is important to not spray the solvent on the test surface directly, because this can remove the penetrant from the flaws.
  • If excess penetrant is not properly removed, once the developer is applied, it may leave a background in the developed area that can mask indications or defects.
  • In addition, this may also produce false indications severely hindering your ability to do a proper inspection.
  • Also, the removal of excessive penetrant is done towards one direction either vertically or horizontally as the case may be.

4. Application of Developer:

  • After excess penetrant has been removed, a white developer is applied to the sample.
  • Several developer types are available, including:non- aqueous wet developer, dry powder, water-suspendable, and water-soluble.
  • Choice of developer is governed by penetrant compatibility (one can’t use water-soluble or -suspendable developer with water-washable penetrant), and by inspection conditions.
  • When using non-aqueous wet developer (NAWD) or dry powder, the sample must be dried prior to application, while soluble and suspendable developers are applied with the part still wet from the previous step.
  • NAWD is commercially available in aerosol spray cans, and may employ acetone, isopropyl alcohol, or a propellant that is a combination of the two. Developer should form a semi-transparent, even coating on the surface.
  • The developer draws penetrant from defects out onto the surface to form a visible indication, commonly known as bleed-out. Any areas that bleed out can indicate the location, orientation and possible types of defects on the surface.
  • Interpreting the results and characterizing defects from the indications found may require some training and/or experience [the indication size is not the actual size of the defect].

5. Inspection:

  • The inspector will use visible light with adequate intensity (100 foot-candles or 1100 lux is typical) for visible dye penetrant.
  • Ultraviolet (UV-A) radiation of adequate intensity (1,000 micro-watts per centimeter squared is common), along with low ambient light levels (less than 2 foot-candles) for fluorescent penetrant examinations.
  • Inspection of the test surface should take place after 10- to 30-minute development time, depends of product kind.
  • This time delay allows the blotting action to occur.
  • The inspector may observe the sample for indication formation when using visible dye.
  • It is also good practice to observe indications as they form because the characteristics of the bleed out are a significant part of interpretation characterization of flaws.

6. Post Cleaning:

  • The test surface is often cleaned after inspection and recording of defects, especially if post-inspection coating processes are scheduled.

Dye penetrant inspection (DPI)

Advantages and Disadvantages:

  • The main advantages of Dye penetrant inspection (DPI), are the speed of the test and the low cost.
  • Disadvantages include the detection of only surface flaws, skin irritation, and the inspection should be on a smooth clean surface where excessive penetrant can be removed prior to being developed.
  • Conducting the test on rough surfaces, such-as “as-welded” welds, will make it difficult to remove any excessive penetrant and could result in false indications.
  • Water-washable penetrant should be considered here if no other option is available. Also, on certain surfaces a great enough color contrast cannot be achieved or the dye will stain the workpiece.
  • Limited training is required for the operator — although experience is quite valuable. Proper cleaning is necessary to assure that surface contaminants have been removed and any defects present are clean and dry. Some cleaning methods have been shown to be detrimental to test sensitivity, so acid etching to remove metal smearing and re-open the defect may be necessary.