Non Destructive Testing Of Steel Valve Castings And

Comparison For The Betterment Of Performance50

Chapter 1INTRODUCTION

There are different methods for producing parts. One among is the casting process. It is one of the most efficient processes which are followed. But there are many defects present in this process also. The sole aim of the project is to determine the defects, the quantity of each defect and to suggest methods to avoid them.The different defects present are,

Gas porosity or blow holesare caused by accumulated gas or air which is trapped by the metal. These discontinuities are usually smooth-walled rounded cavities of a spherical, elongated or flattened shape. Sand inclusions and drossare nonmetallic oxides, which appear on the radiograph as irregular, dark blotches. Shrinkageis a form of discontinuity that appears as dark spots on the radiograph. Shrinkage assumes various forms, but in all cases it occurs because molten metal shrinks as it solidifies, in all portions of the final casting. Among all these the most frequent defect is detected. Actions are taken to reduce this defect. The casting for study is provided at pee key steels. Valve castings are to be tested in them.1.1 PEEKAY STEEL CASTINGS (P) LTD -A PROFILEPeekay Steel Castings Pvt Ltd shall consistently and diligently manufacture products exceeding the expectation of our customers, to remain a leader in casting market by excellence in total quality performance. The foundry is committed to its quality policy and objectives. To achieve this, the foundry has formulated a quality systems and assurance program to bring about improvements in all areas of operation including:Continuous effort to improve product quality Training and motivation of employees Improve professionalism and competence Reduce rejections, rework & wastage and conserve energy. Peekay Steel Castings Pvt Ltd is a vibrant, tech-savvy company which manufactures and supplies steel castings to industry majors like Indias Navaratna Companies and major global OEMs in the Oil, Gas, Power, Transportation, Earth- moving and Engineering Sectors. Peekay Steel Castings Pvt Ltd, which is the flag- ship company of the reputed Peekay Group, commenced manufacture of Steel Castings in 1997. It has an annual turnover of US $ 50 million with a growth rate of 50%. Peekay Steel Castings are exported to USA, Europe, Far East, the Middle East and ASEAN Countries. Over the years the company has gained international reputation as leading manufacturers and suppliers of quality steel castings. Peekay makes steel castings with piece weights ranging between half a kilo and 15 tons. Its Calicut and Coimbatore foundries produce 13200MT of Steel Castings annually using latest advanced technology processes like AOD/ Metal Refining converter, Automatic Moulding Loop Line, Continuous Casting, Leco Gas Analyzer, etc at various stages to ensure highest quality for the steel castings. Peekay is approved supplier of castings for nuclear power plants. The company has the distinction of being the only foundry in India holding all major global certification and accolades under one umbrella.VISIONTo be an engineering conglomerate and lead Peekay to new horizons. Expand and diversify to new industries and cutting edge technologies. To become a one stop supplier to all major OEMs globally in terms of ready to assemble machined castings, forging and fabrication requirements.MISSIONEmerge as one of the top 5 casting manufacturers in the world. To serve the customers with wide range of requirements starting from 0.5 kg to 15 Ton single piece casting from our different plants in different locations.PRODUCTSPeekay Steel Castings (P) Ltd, manufacturing high quality steel castings made of Carbon steel, Alloy steel, Stainless steel, Duplex steel, Nickel base alloys etc. in various sizes and weights up to 11000 Kg per piece for the petrochemical industry, water supply, earth moving, transportation and other engineering industries.PRODUCT LIST:

Gate Valve Components.

Plug Valve Components.

Control and Special Valve Components.

Ball Valve Components.

Butterfly Valve Components.

Engineering Components.THE FOLLOWING END CUSTOMERS/EPC COMPANIES VISITED PEEKAY AND AUDITED THE QUALITY MANAGEMENT SYSTEM :

Mistubishi Heavy Engineering JGC Hawaiyah L&T MHI Exxon Mobil/KOSP Doosan Babcock Thermax TOA Japan Petropars Petronas / Punj Lloyds Abudhabi Marine Operating Co (ADMA) / Mc Dermoot Dubai Man Turbo Switzerland Petrofac British Petroleum National Grid (Trasnco) GDF (France)1.2 OBJECTIVE AND SCOPE OF THE PROJECT

The main objective of the project is to perform NDT on different steel valve castings, ensure the quality of the product fabricated, its safety and reliability in operation. A comparison is done between the radiography results of different steel castings and thus determining the key defects arising in it.

NDT plays a very important role in quality control of a product. The comparison of the different results obtained adds as a feedback for the following: To increase the safety and reliability of product during operation

To reduce cost of production by reducing scrap and conserving materials, labour and energy.

To enhance the reputation of the manufacturer as producer of quality goods. 1.3 ABOUT THE PROJECT WORK

In our project, we attempted to find the defects that are present in steel castings made in peekay steel. There where four NDT testing available at peekay steel. They are magnetic particle inspection, ultrasonic inspections, radiographic testing, liquid penetration test. These tests were conducted by our group. Also we done radiographic testing in 10 steel casting and observed their defects. The defects were plotted, tabulated and studied1.4 PROJECT METHODOLOGY

Chapter 2LITERATURE SURVEYJavier Garcia Martin & Jaime Gomez Gil presented a paper on non-destructive testing of welded products at philosophical transactions of the royal society of London. Series a, mathematical and physical sciences 1979 the royal society. Most process plant and a great deal of structural steelwork for the nuclear, petrochemical, power generation and gas industries is fabricated with the use of fusion welding. Imperfections occur in such welds, due to problems with materials, procedures and techniques, and non-destructive testing is employed to detect such imperfections. The two principal reasons for the use of non-destructive testing are (a) to monitor and control the quality of weld workmanship and (b) to assess fitness for purpose and to ensure that failure will not occur from a weld fault within the design life of the fabrication. In both cases it is necessary to be able to detect, identify and measure weld defects. The results are compared with quality control levels of defect acceptance in the former circumstance and used in fracture mechanics analyses in the latter to ensure that defects present are not critical. A further important application of non-destructive testing is to assess deterioration of plant and structures in service or undergoing maintenance.Ernesto Francis & Nigel Rodrigos presented a paper on estimation of mean and standard deviation at Journal of the Royal Statistical Society. Series B (Methodological) 1961 Royal Statistical Society. The estimation of mean and standard deviation from the values of two quantiles dividing the specimens into three groups has, by previous authors, been made the basis of a quality control system of gauging specimens at two levels. When a specimen may be gauged once only, single gauging, different specimens must be gauged at each level, and the efficiency of the method is reduced. Maximum efficiency is attained when the gauge levels are set symmetrically about the mean. Contour maps calculated for a strongly asymmetric case of the gamma distribution show the maximum efficiency of estimation of to be 20.6 per cent, and of to be 20.0 per cent, while the positioning of the gauge levels for maximum efficiency is now rather critical and the optimum levels are no longer symmetrical about the mean.

Matthias pelkner, andreas neudauer & verena reimund presented a paper on non-destructive testing techniques at philosophical transactions of the royal society of London. Series a, mathematical and physical sciences 1979 the royal society. The paper gives an introductory review of the current status of non-destructive testing techniques as used in engineering practice, and the various ways in which they are employed to improve quality and reliability. All structural materials are inherently 'defective' if one inspects at sufficient sensitivity and many of the limitations of present-day testing techniques centre around the difficulty of characterizing defects in a sufficiently quantitative way so that thresholds can be realistically set. Many techniques rely on interrogation with a sensing probe and as a consequence of this approach there are many limitations associated with ambiguity in interpretation. Improved means of signal processing and data presentation are being evaluated to minimize this ambiguity although it must be realized that the conditions under which engineering inspection has to be carried out in practice often preclude the use of optimum solutions. The paper identifies areas where scientific attention might be directed so that the techniques are more acceptable to present requirements.Valentina ulissi & Francesca antonucci presented a paper on Russell effect on non-destructive testing at philosophical transactions of the royal society of London. Series a, mathematical and physical sciences 1979 the royal society. The Russell effect was discovered in 1897 when it was found that some types of photographic plate could form an image in the dark when placed in contact with certain organic materials or freshly abraded metals. The technique was largely forgotten for several decades. It is now thought that image formation is due to hydrogen peroxide evolution caused by the autooxidation of the objects under examination. The peroxide reduces the silver halide in the photographic emulsion. Several interesting results have been obtained in the non-destructive testing of materials including the detection of recent abrasions of watermarks, areas of objects exposed to daylight, cracks in paint films and the enhancement of writing. A method for studying the Russell effect with modern materials is described.Michele farneselli &Luis a Tarapresented a paper on non-destructive methods at philosophical transactions of the royal society of London. Five non-destructive testing (n.d.t.) methods are widely used for defect detection: these are magnetic particle, dye penetrant, electrical eddy currents, radiography and ultrasonic. The first three can detect only surface-breaking or immediately sub-surface defects, while radiography and ultrasonics can also find embedded, remote defects. Ultrasonics is far more sensitive to cracks than is radiography; moreover, of all the n.d.t. methods, only ultrasonics can in general measure a crack's through-wall position and size. Consequently only ultrasonics is fully compatible with fracture mechanics requirements. Used in conjunction with fracture mechanics, ultrasonics has proved a powerful technique for demonstrating component integrity. After a brief description of the five main n.d.t. methods, the paper concentrates on ultrasonics. Among the points raised are the importance of access and component geometry, the need for cooperation in planning inspections and the ability of ultrasonics to distinguish significant from insignificant defects. The paper closes with two examples of the beneficial joint application of ultrasonics and fracture mechanics.Michael owen & Charles d carlos reported on Recent trends in electromagnetic non destructive sensing. The paper deals with material electromagnetic non-destructive testing (eNDT) with emphasize on eddy current testing (ECT). Various modifications of ECT sensing are compared and discussed from the desired detected signal characteristics point of view. Except of the optimization of usual probe coils arrangements for the concrete applications, the new magnetic sensors as giant magneto-resistance (GMR) and spin dependent tunneling (SDT) are presented. The advanced ECT sensors are characterized by their sensitivity, frequency range and sensor dimensions.Paul j cohn & scarlet docks reported on Efficiency of 2 non destructive testing methods to detect defects in polymeric materials. The aim of this paper was to compare application possibilities of non-destructive ultrasonic and thermographic testing methods to detect defects in polymeric materials. In experimental part, subsurface defects were made in specimens of polymeric materials such as PE, PMMA, laminate then experimentally detected and directly displayed in ultrasonic and thermographic images.Design/methodology/approach: In this paper the development of a real-time non-invasive technique using pulsed infrared (IR) thermography to measure the temperature of polymer materials is described. In this study 16 specimens were pre-heated during specific time using infrared lamp. After that the specimens surface temperature was scanned during cooling down process by a thermovision camera, then defects were detected by means of a thermographic images analysis. The second method applied was ultrasonic testing using the pulse-echo technique as a type of non-destructive testing commonly used to find flaws in materials and to measure the objects thickness.Federer lichards & marvel dukes reported on non destructive testing based on eddy current testing. Non-destructive techniques are used widely in the metal industry in order to control the quality of materials. Eddy current testing is one of the most extensively used non-destructive techniques for inspecting electrically conductive materials at very high speeds that does not require any contact between the test piece and the sensor. This paper includes an overview of the fundamentals and main variables of eddy current testing. It also describes the state-of-the-art sensors and modern techniques such as multi-frequency and pulsed systems. Recent advances in complex models towards solving crack-sensor interaction, developments in instrumentation due to advances in electronic devices, and the evolution of data processing suggest that eddy current testing systems will be increasingly used in the future.Cristepher Nolan reported on system of non destructive testing. In this paper the initial analysis of NDT laboratory is presented by means of agent-based modelling. For the purpose of analysis, laboratory is taken into account as a complex system consisting of three agents; equipment, personnel and specimens. Interaction between the agents is circular. In that sense, the agents are mutually interconnected in a way that one agent simultaneously interacts with others.According to the interactions specific for NDT laboratories, the response of total testing time is presented considering various number of laboratory personnel while each operator has different skills and ability. Agent personnel has to perform testing of specimens. Since the complexity of specimens is quite diverse the specimens are represented as an agent. Additionally, during the whole time sequence of testing a certain specimen, operator is using NDT equipment relevant for the testing method, while the particular time of usage of the equipment can be shorter than the whole testing time. Availability of the equipment is therefore another agent. The evaluated outcome is the total testing time.Presented results are obtained carrying out a simulation by means of multi-agent modelling and simulation tool named ENTORAMA. Finally, the overall laboratory's performance is given in the respect of the number and structure of the laboratory personnel.Albert bale & joe d cruise reported onmagnetic non destructive testing of plastically deformed mild steel. The Barkhausen noise analysis and coercive field measurement have been used as magnetic non-destructive testing methods for plastically deformed high quality carbon steel specimens. The strain dependence of root mean square value and power spectrum of the Barkhausen noise and the coercive field are explained in terms of the dislocation density. The specimens have been subjected to different magnetizing frequencies to show the overlapping nature of the Barkhausen noise. The results are discussed in the context of usage of magnetic non-destructive testing to evaluate the plastic deformation of high quality carbon steel products.

Chapter 3DEFECTS IN CASTINGS

A casting defect is an irregularity in the metal casting process that is undesired. Some defects can be tolerated while others can be repaired otherwise they must be eliminated. They are broken down into five main categories: gas porosity, shrinkage defects , sand inclusion, pouring metal defects , and metallurgical defects .

The terms "defect" and "discontinuity" refer to two specific and separate things in castings. Defects are defined as conditions in a casting that must be corrected or removed, or the casting must be rejected. Discontinuities, also known as "imperfections", are defined as "interruptions in the physical continuity of the casting". Therefore, if the casting is less than perfect, but still useful and in tolerance, the imperfections should be deemed "discontinuities". There are many types of defects which result from many different causes. Some of the solutions to certain defects can be the cause for another type of defect. The following defects can occur in sand castings. Most of these also occur in other casting processes. Shrinkage defects. Shrinkage defects occur when feed metal is not available to compensate for shrinkage as the metal solidifies . Shrinkage defects can be split into two different types: open shrinkage defects and closed shrinkage defects . Open shrinkage defects are open to the atmosphere , therefore as the shrinkage cavity forms air compensates. There are two types of open air defects: pipes and caved surfaces . Pipes form at the surface of the casting and burrow into the casting, while caved surfaces are shallow cavities that form across the surface of the casting.Closed shrinkage defects, also known as shrinkage porosity, are defects that form within the casting. Isolated pools of liquid form inside solidified metal, which are called hot spots. The shrinkage defect usually forms at the top of the hot spots. They require a nucleation point, so impurities and dissolved gas can induce closed shrinkage defects. The defects are broken up into macroporosity and microporosity (or microshrinkage ), where macroporosity can be seen by the naked eye and microporosity cannot. Gas porosity Gas porosity is the formation of bubbles within the casting after it has cooled. This occurs because most liquid materials can hold a large amount of dissolved gas, but the solid form of the same material cannot, so the gas forms bubbles within the material as it cools. Gas porosity may present itself on the surface of the casting as porosity or the pore may be trapped inside the metal, which reduces strength in that vicinity. Nitrogen , oxygen and hydrogen are the most encountered gases in cases of gas porosity. In aluminum castings, hydrogen is the only gas that dissolves in significant quantity, which can result in hydrogen gas porosity. For casting that are a few kilograms in weight the pores are usually 0.01 to 0.5 mm (0.00039 to 0.01969 in) in size. In larger casting they can be up to a millimeter (0.040 in) in diameter. Gas porosity can sometimes be difficult to distinguish from micro shrinkage because micro shrinkage cavities can contain gases as well. In general, microporosities will form if the casting is not properly risered or if a material with a wide solidification range is cast. If neither of these are the case then most likely the porosity is due to gas formation. Blowhole defect in a cast iron part. Tiny gas bubbles are called porosities, but larger gas bubbles are called a blow holesor blisters . Such defects can be caused by air entrained in the melt, steam or smoke from the casting sand, or other gasses from the melt or mold. (Vacuum holes caused by metal shrinkage (see above) may also be loosely referred to as 'blowholes'). Proper foundry practices, including melt preparation and mold design, can reduce the occurrence of these defects. Because they are often surrounded by a skin of sound metal, blowholes may be difficult to detect, requiring harmonic, ultrasonic , magnetic , or X-ray (i.e., industrial CT scanning) analysis.RADIOGRAPHIC INDICATIONS FOR CASTINGS

Gas porosity or blow holesare caused by accumulated gas or air which is trapped by the metal. These discontinuities are usually smooth-walled rounded cavities of a spherical, elongated or flattened shape. If the sprue is not high enough to provide the necessary heat transfer needed to force the gas or air out of the mold, the gas or air will be trapped as the molten metal begins to solidify. Blows can also be caused by sand that is too fine, too wet, or by sand that has a low permeability so that gas cannot escape. Too high a moisture content in the sand makes it difficult to carry the excessive volumes of water vapor away from the casting. Another cause of blows can be attributed to using green ladles, rusty or damp chills and chaplets.Sand inclusions and drossare nonmetallic oxides, which appear on the radiograph as irregular, dark blotches. These come from disintegrated portions of mold or core walls and/or from oxides (formed in the melt) which have not been skimmed off prior to the introduction of the metal into the mold gates. Careful control of the melt, proper holding time in the ladle and skimming of the melt during pouring will minimize or obviate this source of trouble.Shrinkageis a form of discontinuity that appears as dark spots on the radiograph. Shrinkage assumes various forms, but in all cases it occurs because molten metal shrinks as it solidifies, in all portions of the final casting. Shrinkage is avoided by making sure that the volume of the casting is adequately fed by risers which sacrificially retain the shrinkage. Shrinkage in its various forms can be recognized by a number of characteristics on radiographs. There are at least four types of shrinkage: (1) cavity; (2) dendritic; (3) filamentary; and (4) sponge types. Some documents designate these types by numbers, without actual names, to avoid possible misunderstanding.

CAVITY SHRINKAGEappears as areas with distinct jagged boundaries. It may be produced when metal solidifies between two original streams of melt coming from opposite directions to join a common front. Cavity shrinkage usually occurs at a time when the melt has almost reached solidification temperature and there is no source of supplementary liquid to feed possible cavities.

DENDRITIC SHRINKAGEis a distribution of very fine lines or small elongated cavities that may vary in density and are usually unconnected.FILAMENTARY SHRINKAGEusually occurs as a continuous structure of connected lines or branches of variable length, width and density, or occasionally as a network.

SPONGE SHRINKAGEshows itself as areas of lacy texture with diffuse outlines, generally toward the mid-thickness of heavier casting sections. Sponge shrinkage may be dendritic or filamentary shrinkage. Filamentary sponge shrinkage appears more blurred because it is projected through the relatively thick coating between the discontinuities and the film surface.

CRACKSare thin (straight or jagged) linearly disposed discontinuities that occur after the melt has solidified. They generally appear singly and originate at casting surfaces.

Cold shutsgenerally appear on or near a surface of cast metal as a result of two streams of liquid meeting and failing to unite. They may appear on a radiograph as cracks or seams with smooth or rounded edges.INCLUSIONSare nonmetallic materials in an otherwise solid metallic matrix. They may be less or more dense than the matrix alloy and will appear on the radiograph, respectively, as darker or lighter indications. The latter type is more common in light metal castings.

CORE SHIFTshows itself as a variation in section thickness, usually on radiographic views representing diametrically opposite portions of cylindrical casting portions.

Chapter 4NDT TESTS

TEST 1 - MAGNETIC PARTICLE INSPECTION

1.1 INTRODUCTION

Magnetic particle inspection (MPI) is a nondestructive testing method used for defect detection. MPI is fast and relatively easy to apply, and part surface preparation is not as critical as it is for some other NDT methods. These characteristics make MPI one of the most widely utilized nondestructive testing methods.MPI uses magnetic fields and small magnetic particles (i.e.iron filings) to detect flaws in components. The only requirement from an inspectability standpoint is that the component being inspected must be made of a ferromagnetic material such as iron, nickel, cobalt, or some of their alloys. Ferromagnetic materials are materials that can be magnetized to a level that will allow the inspection to be effective.The method is used to inspect a variety of product forms including castings, forgings, and weldments. Many different industries use magnetic particle inspection for determining a component's fitness-for-use. Some examples of industries that use magnetic particle inspection are the structural steel, automotive, petrochemical, power generation, and aerospace industries. Underwater inspection is another area where magnetic particle inspection may be used to test items such as offshore structures and underwater pipelines.1.2 PRINCIPLEIn theory, magnetic particle inspection (MPI) is a relatively simple concept. It can be considered as a combination of two nondestructive testing methods: magnetic flux leakage testing and visual testing. Consider the case of a bar magnet. It has a magnetic field in and around the magnet. Any place that a magnetic line of force exits or enters the magnet is called a pole. A pole where a magnetic line of force exits the magnet is called a north pole and a pole where a line of force enters the magnet is called a south pole.When a bar magnet is broken in the center of its length, two complete bar magnets with magnetic poles on each end of each piece will result. If the magnet is just cracked but not broken completely in two, a north and south pole will form at each edge of the crack. The magnetic field exits the north pole and reenters at the south pole. The magnetic field spreads out when it encounters the small air gap created by the crack because the air cannot support as much magnetic field per unit volume as the magnet can. When the field spreads out, it appears to leak out of the material and, thus is called a flux leakage field.

FIG 1 PRINCIPLE OF MAGNETIC PARTICLE INSPECTION

If iron particles are sprinkled on a cracked magnet, the particles will be attracted to and cluster not only at the poles at the ends of the magnet, but also at the poles at the edges of the crack. This cluster of particles is much easier to see than the actual crack and this is the basis for magnetic particle inspection.The first step in a magnetic particle inspection is to magnetize the component that is to be inspected. If any defects on or near the surface are present, the defects will create a leakage field. After the component has been magnetized, iron particles, either in a dry or wet suspended form, are applied to the surface of the magnetized part. The particles will be attracted and cluster at the flux leakage fields, thus forming a visible indication that the inspector can detect.1.3 REFERENCE STANDARDS

1.3.1ASME B16.34-valves-flanged, threaded and welding end.

1.3.2ASME Section V-Non destructive examination.

1.3.3ASME Section VIII div.1-Rules for construction of pressure vessels.

1.3.4ASTM/ASME E709/SE709-stamdard guide for magnetic particle examination.

1.3.5SNT TC 1A-personnel qualification and certification in non distructive testing.1.3.6MSS SP 53-magnetic particle examination method.1.4 EQUIPMENTS

1.4.1Magnetic particle testing equipment model m530,6000amps,ac/hwdc,make Magnaflux (prod type)1.4.2Electromagnetic yoke, model y-7, yoke weight lifting capacity 4.5 kgs1.4.3Electrical power source1.4.4Calibration equipment1.4.5Magnetizing and demagnetizing equipment1.4.6Inspection medium1.5 PROCEDURE

1.5.1 CALIBRATION OF EQUIPMENTS

1.5.1.1 Frequency-

The equipment shall be calibrated once in a year and/or whenever the equipment is subjected to major repair or damage whichever is earlier

1.5.1.2 Procedure-

The accuracy of the meter shall be verified by the equipment traceable to national standards. Comparative readings should be taken for different current output levels encompassing the usable range.

1.5.1.3 Tolerance-

The units light meter reading shall not deviate by more than 10% of full scale relative to the actual current value as shown by the test meter.

1.5.1.4 Lifting capacity check for yoke-

Electromagnetic yoke shall be weight tested before the start of the job. In AC mode, the yoke at maximum pole spacing required for the job shall lift at least 4.5kgs and in HWDC mode shall lift at least 18kgs.

1.5.1.5 Light meters-

Light meters shall be calibrated at least once a year or whenever the meter has been required. If meters were not in use for one year or more, calibration shall be done before being used.

1.5.1.6 Residual field indicator-

Field indicator shall be used to determine residual magnetism whenever required using a calibrated field indicator. This shall be calibrated once a year.1.5.2 INSPECTION MEDIUM

The inspection medium shall be finely divided either Dry or Wet visible or wet Fluorescent ferromagnetic powder particles. Powder particles shall be Black or Red in color for visible and Green Yellow in color fluorescent powder.

The particles having high permeability and low retentivity and of suitable grain size to be readily float over the surface being tested shall be used.1.5.3 SURFACE PREPARATIONThe surface being inspected shall be dry and clean. It shall be free from oil, sand, paint, scale, welding flux and weld spatter.

The tip of the prod shall be cleaned often to have better contact with the job surface.

1.5.4 INSPECTION TECHNIQUE

The area shall be circularly magnetized by means of contact electrode or prods. The process shall be carried out by continuous method and magnetic field strength is as follows,

I Prod method:

The magnetizing current of 90 to 110 ampere per 1 inch prod spacing is used. Prod Spacing should be between 4 inch and 8 inches to avoid spark and to get proper current flow. Defects are visualized under UV lights after the application of fluorescent fluid. The cracks are visualized by alternatively placing the prods across each diagonals of the grids. The visualized cracks are marked using solvent washable industrial marking paint.

II Yoke method:

Used for finished surfaces.

Alternating or direct current electromagnetic yokes, or permanent magnetic yokes shall be used.1.6 EXAMINATION1.6.1 DIRECTION OF MAGNETIZATIONTo separate examinations shall be carried out in each area. The second examination shall be performed with prods appropriately at right angles to the current flow used for the first examination in that area

1.6.2 EXAMINATION METHODWhen dry magnetic particles are used the magnetizing current shall remain on while the examination medium is being applied and while any excess of the examination medium is removed.

Fig 2 Examination MethodWhen wet magnetic particles are used the magnetizing current shall be turned on after the particles have been applied, flow of particles shall stop with the application of the current. Wet particles applied from aerosol spray cans may be applied before and / or after magnetizing current supplied.Wet articles maybe applied during the application of magnetizing current if they are not applied directly to the examination area and are allowed to flow over the examination area.

All the examinations shall be conducted with minimum 10% overlap to ensure the required areas are covered.

1.6.3 INTERPRETATION

1.6.3.1 Minimum light intensity:Visual observation of the non fluorescent magnetic particle indications shall be carried out with the naked eye or under slight magnification.

In case where artificial light sources are required, the minimum intensity shall be achieved by holding suitable light source held at an appropriate distance from examination surface to ensure 1000 lux.1.6.3.2 Minimum light intensity:In case fluorescent products are used the parts or area examined shall ne located in the dark area, where the uv lights of at least 1000microwatt/cm2 of intensity level. The white light or other light sources intensity shall not exceed 20 lux.

Discontinuities at or near the surface would be indicated by the retention of the inspection medium. All the indications are not necessarily defects. Since certain metallurgical discontinuities and magnetic permeability variations may produce similar indications which are not relevant to the detection of un acceptable discontinuities. These non relevant indications shall be re examined by any other suitable non destructive test such as penetrant test. Relevant indications are those which result from mechanical discontinuities. Only those indications with major dimension greater than 1.6 mm shall be considered relevant.1.6.4 ACCEPTANCE CRITERIA: 1.6.4.1 Unless otherwise specified the acceptance standard for discontinuities shall be ASME 1634 appendix - II for casting. ASME boiler and pressure vessel code section VIII division 1 appendix 6 for welds.The maximum acceptable indications are as follows,

1.6.4.2 Castings

1.6.4.3 Linear indications

I .3 in (8mm) long for materials up to .5 in (13mm) thick.

II .5 in (13mm) long for material .5in to 1in (13mm -25mm) thick.

III .7 in (18mm) long for materials over 1 in (25mm) thick

For linear indications the indications must be separated by the distance greater than the length of an acceptable indication. A linear indication is one with length in excess of 3 times the width.

1.6.4.4 Rounded indications

I max of 0.3 in (8mm) dia for materials up to 0.5 in (13mm) thick

II max of 0.5 in (13mm) dia for materials up to 0.5 in (13mm) thick

TEST 2 RADIOGRAPHY TEST

2.1 INTRODUCTION

Radiography today is one of the most important, most versatile, of all the nondestructive test methods used by casting industry. Employing highly penetrating X-rays, gamma rays, and other forms of radiation that do not damage the parts itself, radiography provides a permanent visible film record of internal conditions, containing the basic information by which soundness can be determined. This technique is suitable for the detection of internal defects in ferrous and nonferrous metals and other materials. X-rays, generated electrically, and Gamma rays emitted from radio-active isotopes, are penetrating radiation which is differentially absorbed by the material through which it passes; the greater the thickness, the greater the absorption. Furthermore, the denser the material, the greater the absorption. X and Gamma rays also have the property, like light, of partially converting silver halide crystals in a photographic film to metallic silver, in proportion to the intensity of the radiation reaching the film, and therefore forming a latent image. This can be developed and fixed in a similar way to normal photographic film. Material with internal voids is tested by placing the subject between the source of radiation and the film. The voids show as darkened areas, where more radiation has reached the film, on a clear background. The principles are the same for both X and Gamma radiography.

FIG 3 WORKING OF RADIOGRAPHIC TESTING2.2 PRINCIPLE

In X-radiography the penetrating power is determined by the number of volts applied to the X-Ray tube - in steel approximately 1000 volts per inch thickness is necessary. In Gamma radiography the isotope governs the penetrating power and is unalterable in each isotope. Thus Iridium 192 is used for 1/2" to 1" steel and Cesium 134 is used for 3/4" to 21/2" steel. In X-radiography the intensity, and therefore the exposure time, is governed by the amperage of the cathode in the tube. Exposure time is usually expressed in terms of mill ampere minutes. With Gamma rays the intensity of the radiation is set at the time of supply of the isotope. The intensity of radiation from isotopes is measured in Becquerels and reduces over a period of time. The time taken to decay to half the amount of curies is the half life and is characteristic of each isotope. For example, the half life of Iridium 192 is 74 days, and Cesium 134 is 2.1 years. The exposure factor is a product of the number of curies and time, usually expressed in curie hours. The time of exposure must be increased as the isotope decays - when the exposure period becomes uneconomical the isotope must be renewed. As the isotope is continuously emitting radiation it must be housed in a container of depleted uranium or similar dense shielding material, whilst not exposed to protect the environment and personnel. To produce an X or Gamma radiograph, the film package (comprising film and intensifying screens - the latter being required to reduce the exposure time enclosed in a light tight cassette) is placed close to the surface of the subject. The source of radiation is positioned on the other side of the subject some distance away, so that the radiation passes through the subject and on to the film. After the exposure period the film is removed, processed, dried, and then viewed by transmitted light on a special viewer. Various radiographic and photographic accessories are necessary, including such items as radiation monitors, film markers, image quality indicators, darkroom equipment, etc. Where the last is concerned there are many degrees of sophistication, including fully automatic processing units. These accessories are the same for both X and Gamma radiography systems. Also required are such consumable items as radiographic film and processing chemicals.

Fig 4 Inspection Method2.3 REFERENCE STANDARDS

2.3.1 BPVC Section V, Non destructive Examination Article 2 Radiographic examination

2.3.2 ASTM E 94, Standard Guide for Radiographic examination

2.3.3 ASTM E 592, Standard Guide to Obtainable ASTM Equivalent Penetrameter Sensitivity for Radiography of Steel Plates

2.3.4 SNT TC 1A-personnel qualification and certification in non destructive testing2.3.5 ASME Section V-Non destructive examination2.4 EQUIPMENTS

2.4.1 xray gennerators

2.4.2intensifying screen

2.4.3 penetrameters or image quality indicators or radiography camera.

2.4.4 industrial x ray flms

2.4.5 processing chemicals

2.4.5.1 developer

2.4.5.2 stop bath

2.4.5.3 fixer

2.4.5.4 wash accelerator

2.4.5.5 wetting agent

2.4.6 photographic processing equipment

2.5 PROCEDURE

2.5.1 CALIBRATION OF EQUIPMENTS

2.5.1.1 Exposure time:

To radiograph an object, the film is exposed to a pre determined dose of radiation [film factor] and then developed under standard conditions of temperature and time to achieve the target density [blackness].

Exposure = Radiation Intensity X Time.2.5.1.2 Half Life:The half life, T is defined as the time required for the activity of any particular radioisotope to decrease to one-half of its initial activity. N = N0 e -( t where ( = 0.693 / T

Or N = N0 e - .693 t / T T = half life ( = disintegration constant of the isotope.

N = number of remaining radioactive atoms after elapsed time t.

N0= initial number of radioactive atoms when the time t begins.

2.5.1.3 Radiation Intensity:

Radiation intensity of X or gamma rays is measured by the rate of ionization [knocked out electrons] or charge produced by the radiation in a specified volume of air at a given location.

2.5.2 INSPECTION MEDIUM

The inspection medium is a film which is a thin, flexible, optically clear, polyester base, which remains flat, is coated with Silver Halide-Gelatin emulsion using a binder.2.5.3 INSPECTION TECHNIQUE

In radiographic testing, the part to be inspected is placed between the radiation source and a piece of radiation sensitive film.

The radiation source can either be an X-ray machine or a radioactive source (Ir-192, Co-60, or in rare cases Cs-137).

The part will stop some of the radiation where thicker and denser areas will stop more of the radiation.

The radiation that passes through the part will expose the film and forms a shadowgraph of the part.

The film darkness (density) will vary with the amount of radiation reaching the film through the test object where darker areas indicate more exposure (higher radiation intensity) and liter areas indicate less exposure (higher radiation intensity).

2.6 EXAMINATION

2.6.1 Developing:

Exposed films are locked in stainless steel hangers, and immersed in the developer for 5 minutes at 200C. Immediately after immersion the hangers are tapped to dislodge air bubbles clinging to the surface of the films. The developer is then agitated by shaking the hangers for 10 seconds in every minute to maintain uniform developing action. Continuous agitation significantly reduces developing time. Developing time depends on solution temperature and concentration and must be corrected as required. By temperature control and replenishment of the developer, constant developing time can be maintained.

2.6.2 Stop bath:

Developer solution is alkaline where as fixer is acidic. Hence developed films are washed in 2% acetic acid solution or water to remove traces of developer remaining on the films before they are immersed in the fixer solution.

2.6.3 Fixing:

The films are immersed in the fixer solution to make the developed image stable by removing unexposed silver halide grains by fixing action. Recommended fixing time is twice the clearing time and films can be left in the fixer for up to 15 minutes.

2.6.4 Washing:

Following fixing, the films are washed in running water for 15 minutes to remove all traces of fixer from the surface. Washing time can be reduced by using suitable chemicals. Improperly washed films become brown with age.

2.6.5 Drying:

Films are finally dried uniformly by evaporation or by circulating hot air in a temperature controlled drying cabinet.

2.7 INTERPRETATION

2.7.1 Air inclusion

FIG 5 AIR INCLUSION

Air inclusion defects are seen as above. These discontinuities are usually smooth-walled rounded cavities of a spherical, elongated or flattened shape There are different levels of air inclusions. These levels are determined by comparing the obtained film with the standards.2.7.2 Sand Inclusion FIG 6 SAND INCLUSION

Sand inclusion is seen as above. These come from disintegrated portions of mold or core walls and/or from oxides (formed in the melt) which have not been skimmed off prior to the introduction of the metal into the mold gates. The levels of defect is noted by comparing with the standards.2.7.3 Shrinkage

FIG 7 SHRINKAGE

Shrinkage are seen as above. It appears as areas with distinct jagged boundaries. It may be produced when metal solidifies between two original streams of melt coming from opposite directions to join a common front. The level is determined b comparison with the appropriate standards.2.7.4 Cracks

Cracks are seen as thin (straight or jagged) linearly disposed discontinuities that occur after the melt has solidified. Its level is determined by comparing with the appropriate standards.FIG 8 - CRACKSTEST 3 PENETRANT TEST3.1 INTRODUCTION

Liquid penetrant test method enhances the visibility of surface breaking flaws such as cracssks, fissures, crevices and pores. It can be used very successfully regardless of component size and can tolerate complicated part geometry.Penetrant testing is used on metals such as aluminium, magnesium, brass, copper, cast iron, steel, stainless steel, titanium and other common alloys. It can also test other materials, including glazed ceramics, plastics, molded rubber, powdered metal products and glass.Some limitations are,the discontinuity to be detected must be open to the surface and the interior free from foreign materials.The test surface should not be porous.The material under test must not be susceptible to damage from the liquids used for the examination.The test process has temperature limitations [ 10 to 520 C ].Special requirements are that the penetrant materials must be designed with a low sulfur and halogen content to avoid harmful effects on the test parts. Stainless steels are especially susceptible to corrosion when exposed to chlorine and Carbon steels to sulfur. Titanium is extremely susceptible to embrittlement when in contact with halogens. High Nickel alloys are also affected by sulpher and halogens. These harmful chemicals can be found in penetrant materials but are limited to 1% by weight of content.Common penetrant materials attack PVC, making it brittle, which leads to cracking. Liquid oxygen compatible penetrant materials must be used when testing parts that will be in contact with either liquid or gaseous oxygen.

3.2 PRINCIPLE

The principle of liquid penetrant testing is based on the ability of some liquids to enter a discontinuity opening and then re-emerge from it when the excess penetrant is removed from the surface.Capillary action is the means by which a liquid enters a discontinuity opening. This action is what causes a piece of sponge to absorb liquid. Capillary action is a phenomenon in which water or other liquids will rise above the normal liquid level in a small bore or capillary tube due to the attraction of the molecules in the liquid for each other and for the wall of the tube [ cohesion and adhesion ].Cohesion is interaction between two surfaces of the same material in contact, makes them cling together [ with two different materials the similar phenomenon is called adhesion ]. According to kinetic theory, cohesion is caused by attraction between particles at the atomic or molecular level. Surface tension, which causes liquids to form spherical droplets, is caused by cohesion.The distance the liquid will rise up the tube of a given diameter and material is a function of three factors;Surface tension, Wetting ability, Tube open or close at the top end. Liquid will rise less in a closed end tube.The practical circumstances, a penetrant encounters during testing is more complex. Cracks, for example are not capillary tubes, but simulate the basic interaction between a liquid and a solid surface, which is responsible for the migration of penetrant into its open space. This same interaction acts again and penetrant emerges from the discontinuity when the excess penetrant is removed from the surface.

3.3 PROPERTIES OF PENETRANT

The performance of a penetrant is achieved by a combination of controlled physical and chemical properties ;

Viscosity :Is related to the rate at which a liquid will flow under some applied force. It affects the speed of penetration through the discontinuity opening. A low viscosity liquid is used for faster penetration and also less drag out in immersion. Surface tension :Is one of the most important properties which determines the penetrating ability of a liquid. Low surface tension liquids provide better penetration and spreads well on part surface. Wetting ability is another important property which also determines the penetrating ability of a liquid. Ability to wet or spread on the surface is related directly to the contact angle between the liquid and the surface at the point of contact. To have a good wetting ability, the contact angle must be small. Penetrants used for testing have contact angle of 50 or less. Brightness :The dye in the penetrant should be highly stable and bright enough to be visible in very thin film. Volatility is the speed with which a liquid evaporates. Penetrant should be non volatile to allow long penetration and inspection time. The penetrant must not dry during the examination period. Flash point is the temperature at which flammable vapor is given off. For safety purpose, a penetrant should have higher or no flash point. Chemical Innertness is the ability of a material not to interact when mixed with or brought into contact with other materials. Penetrant should be as inert and non corrosive as possible towards the materials to be tested. Solubility is the ability of a material to be dissolved into another material. Penetrant must be soluble in order to be easily removed from the surface of the part being examined. Creep is the ability of small amounts of liquid in discontinuities to com back out to form an indication. Tolerance for Contamination is the ability to tolerate small amounts of foreign substances and not affect unfavorably the action of a penetrant. A penetrant is a compound of several ingredients and a little water, acids, detergents and degreaser solvents may upset the balance and cause the penetrant to lose some or all of its important properties. Toxicity, Skin irritation and odor No penetrant should contain poisonous, corrosive or skin irritating material or have an offensive odor.3.4 REFERENCE STANDARDS

3.4.1-ASME B16.34-valves-flanged, threaded and welding end

3.4.2-ASME Section V-Non destructive examinassions 3.4.3-ASME Section VIII div.1-Rules for construction of pressure vessels

3.4.4-ASTM E165/ASME SE165-Standard Test Method for Liquid Penetrant Examination

3.4.5-SNT TC 1A-Personnel Qualification And Certification In Non Distructive Testing

3.4.6-MSS SP 93-Liquid Penetrant Examination Method

3.5 EQUIPMENTS

Liquid penetrant testing materials consist of visible penetrants,removers and developers.

3.5.1 PENETRANTS

Water washable penetrants are formulated to be directly water washable from the surface of the test part,after a suitable penetrant dwell time.

Solvent removable penetrants are formulated so that excess surface penetrant can be removed by wiping until most of the penetrant have been removed.3.5.2 SOLVENT REMOVERS

Solvent removers function by dissolving the penetrant making it possible to wipe the surface clean and free of excess penetrant.

3.5.3 DEVELOPER

Developers form a translucent or white absorptive coating that aids in bringing the developer particles in a nonaqueous solvent carrier ready to use as supplied.3.6 PROCEDURE

3.6.1 CALIBRATION

Light meters shall be calibrated at least once a year or whenever the meter has been repaired which ever is earlier.3.6.2 SURFACE PREPARATION

Satisfactory results May be obtained when the surface of the part is in the as-part condition.Surface preparation by grinding,machining,wire brushing or other may be necessary where surface irregularities could mask indication. Prior to examination the surface to be examined and adjascent areas within atleast 25mm shall be dry and clean from scale, dirt,paint,rust, greece, oil.

3.6.3 PRE-TEST CLEANING

Test area shall be thorougly cleaned by wiping with acetone or cleaner and then wiped with lint free cloth.Cleaner shall be allowed to dry for 3-5 min before applying penetrant.Adequate care shall be taken to ensure proper surface condition prior to testing.3.6.4 TEMPERATURE

The temperature of the penetrant materials and the surface of the part to be processed shall be between 50F to 125F.Local heating or cooling is permitted provided the part temperature remains in the range 50F to 125F during examination. 3.6.5 INSPECTION TECHNIQUE

3.6.5.1 Penetrant application

The penetrant is applied to the surface to be examined so that the entire part or area under examination is completely covered with penetrant. The penetrant shall be applied by spraying, brushing or dipping. Penetrant shall be applied so that no air bubbles are present and no uncovered areas are visible.

3.6.5.2 Penetrant dwell time

The penetration time shall be minimum 10 minutes and maximum 20 minutes. The penetrant shall be remaining wet throughout the dwell time.

3.6.5.3 Penetrant removal

Water washable penetrants Excess water washable penetrants shall be removed with a water spray. The water pressure shall not excceed 50psi and the water temperature shall not exceed 110F.

Solovent removable penetrants The area with penetrant shall be cleaned with a clean lint free cloth. Cleaning is continued till all the traces of visible penetrants is removed.

3.6.5.4 Drying after excess penetrant removal

For the water washable techniques the surfaces may be dried by blotting with clean materials or by using circulating air provided the temperature of the surface is not raised above 125F.For the solvent removable technique the surfaces may be dried by normal evaporation,blotting.

3.6.5.4 Developer application

With colour contrast penetrants only non aqueous developer shall be used.Non aqqueous developer shall be applie to dry surface.It shall be applied by spraying with aerosol spray can except where safety or restricted access precludes it.Drying shall be by normal evaporation.

3.6.5.5 Developer dwell time

Developer dwell time shall be 10min minimum.Viewing of the liquid penetrant test shall be done within 30min after the application of developer.

FIG 9 WORKING PRINCIPLE OF PENITRENT TEST3.6.6 INTERPRETATION

3.6.6.1 The final interpretation shall be done between 10 30 minutes after the application of developer. If the inspection area is large, the interpretation shall be done in increments.

3.6.6.2 Color contrast penetrants

Minimum Light Intensity-Interpretation shall be carried out in a well ilit area.A minmum light intensity of 1000lux is required on the surface to be examined to ensure adequate sesitivity during the exaniation and evaluation of indication.

Discontinuities at the surface will be indicated by bleeding out of the penetrant.However localised surface irregularities such as machining mark or other surface condition may produce false indication.

3.6.6.3 Any indications which is believed to be non relevant shall be regarded as a defect until the indication is either eliminated by surface conditioning or it is evaluated by other non destructive methods and proved to be non relevant.

3.7 EVALUATION

3.7.1 ACCEPTANCE CRITERIA Unless otherwise specified, acceptance standard for discontinuities shall be ASME B16.34 Appendix-III for castings.

3.7.2 Castings

3.7.2.1 Linear indications

0.3inch long for materials upto 0.5inch thick.

0.5inch long for materials 0.5 to1inch thick.

0.7inch long for materials over 1inch thick.

3.7.2.2 Rounded indications

0.3inch dia for materials upto 0.5inch thick.

0.5inch dia for materials over 0.5inch thick.3.8 POST CLEANING

Post cleaning shall be done by simple water rinse, water spray or solvent soak method. Post cleaning shall be carried out as a property as possible as examintaion to remove developer powder and penetrant from the examined surface.TEST 4 ULTRASONIC EXAMINATION

4.1 INTRODUCTION

Ultrasound is transmission of energy through an elastic medium, by means of vibrations of the particles. The vibrating particles transfers some of the vibrational [ mechanical ] energy on to neighboring particles and force them to vibrate. The energy thus propagates through particles. Because of this, sound cannot propagate in vacuum.

Sound generated above 20,000 Hz is called ultrasound. Ultrasound propagates more easily through solids than through liquids or gasses. Ultrasound with frequencies of 1 MHz and above is directional, has short wavelength, and gets reflected from small discontinuities in materials. This property makes ultrasound useful for detecting and locating defects in materials. Wave length : Ultrasonic vibrations travel in the form of waves. The distance, measured along the line of propagation, between two wave surfaces in which the phase differs by one complete period is wavelength. It is not the material's particles that moves through the thickness, it is the vibrational [ mechanical ] energy that is transferred from one particle to another.

Frequency : The number of wave lengths [ vibration cycles of a particle ] completed in one second is frequency.

Unit of frequency is Hertz [ Hz ]

Cycle : The particles are displaced, first in the forward direction and then in the opposite direction. These two displacements equal one cycle.

Period : The time required to complete a full cycle of vibration of a particle is period.

Period is one second divided by frequency. [ T = 1 / F ]

Velocity : Velocity is the speed of energy transfer between two points. The distance of propagation of the wave [ energy ] in one second is the velocity of the wave. Velocity of ultrasound in a perfectly elastic material at a given temperature and pressure is constant. Velocity depends on the density, elasticity and rigidity of the test material.Velocity, Frequency and Wavelength are related as,

Velocity = Frequency X Wavelength.

Acoustic pressure [ P ] is the amplitude of alternating stresses on the material by a propagating ultrasonic wave.

P = acoustic impedance X amplitude of particle vibration.

Ultrasonic Intensity [ I ] is the transmission of mechanical energy, through an unit cross- section area, which is perpendicular to the direction of the wave propagation.

I = [ acoustic pressure X amplitude of particle vibration ]

4.2 PRINCIPLEPulse echo test method uses reflected ultrasound as a means of collecting test information. A single crystal probe is normally used for ultrasound generation as well as reception.

The transmitter circuit of the flaw detector supplies short excitation pulses of few hundred volts at regular interval to the probe crystal. The excitation pulse oscillates the crystal to generate short burst of ultrasound such that the arrival of each returning echo may be identifiable as a discrete event. During the interval between two successive pulses, the crystal is at rest and detects any return echo such as from the back wall. A large percentage of the sound is reflected from the front surface of the test part and the remainder is reflected by the back surface or discontinuities. The flaw detectors CRT screen displays the whole operation by producing separated signals of transmission and the time of arrival of defect echo and the back wall echo. The transmission pulse and subsequent echoes appear as peaks rising out of the CRTs base line. The distance between the peaks is a measure of the defects location or the parts thickness.4.3 REFERENCE STANDARDS

4.3.1-ASME B1634 Valves Flanged, Threaded and Welding End

4.3.2-ASME Section V- Non Destructive Examination.

4.3.3-ASME Section VII Div. 1 Rule for Construction of Pressure vessels.

4.3.4-ASTM/ASME A609 / SA609 Standard Guide for ultrasonic examination.

4.3.5-TC 1A Personnel Qualification and Certification in Non-destructive Testing.4.4 EQUIPMENTS4.4.1ULTRASONIC FLAW DETECTOR:Make: EEC Mumbai, Model: Eecoscan ED-1-10/ Digital Ultrasonic equipment Model: DS-322 or equipment shall be used. The equipments shall meet the requirments of ASME SEC V Article 4 for the vertical and horizontal linearity.

4.4.2 TRANSDUCERS:

Normal probe:

Frequency:1 to 4 MHz

Size

:10mm Dia/24mm Dia

TR probe:

Frequency:1 to 4 MHz

Size

:10mm Dia/24mm Dia

Note: Transducer of the other frequency and size may be used depending upon particular test requirements.

Type of Wave : Longitudinal wave.

4.4.3 COUPLANT:

Couplant shall be able to remove air between the transducer and the test specimen surface so as to establish proper contact between transducer and job. Couplant used shall be oil, Type:SAE 30 / SAE 40, grease or a mixture of both depending up on surface condition of job.

Same type of couplant shall be used for calibration and during the examination.4.5 PROCEDURE

4.5.1 CALIBRATION OF EQUIPMENTSThe calibration and performance of manual ultrasonic test system can be checked using the IIW - V1 block.

Normal Probe :

S : System Sensitivity check, with the hole signal set to 75% screen height, minimum 40 dB reserved gain required.

R : Resolution check [ ability to produce separate indication ] The signals from the 85, 91 and 100 mm distances should be displayed on the screen without overlapping.D2 : Dead zone, signal from hole indicates 10 mm or less.D1 : Dead zone, signal from hole indicates, 5 mm or less.P : Checks sound generating ability of the system. With the gain at maximum, 5 full screen signals from the 23 mm Perspex insert, using a 2 MHz probe should be obtained. R1 and R2 : Range calibration and Horizontal Linearity.Angle Probe :

E: Beam exit point, when the signal from the radius becomes maximum, the exit point of the probe coincides with the center mark of the scale on the face of the block.S: Sensitivity check. with the signal from the radius set to 100%, minimum 40 dB reserved gain required.R: Range calibration for angle probe.

A1: and A2: Angle check, when the signal from the hole becomes maximum, the exit point of the probe may coincide with one of the marks on the face of the block to indicate the refracted beam angle of the probe. Horizontal Linearity : For accurately locating reflectors, a linear distance scale is essential.A 100 mm range is accurately calibrated from location R1. With the probe at position R2, signals should appear exactly at 12.5, 25, 37.5 and 50 th division on the screen. A signal position deviation by more than 1% indicates, non linear distance scale. This check should be carried out over the maximum range used for actual testing. The ultrasonic instrument must provide linear vertical presentation within +/- 5% of the full screen height.

Screen Height Linearity : Using a viscous couplant, a normal beam probe is positioned at a suitable location of the block to give a 2 : 1 ratio of amplitudes between two steady signals. When the attenuator is changed in 2 dB steps, the smaller amplitude signal must remain 50% of the larger amplitude within +/- 5% of full screen height.

Amplitude Control Linearity : The accuracy of the amplitude control of the ultrasonic equipment is also essential.

Using a viscous couplant, a normal beam probe is positioned on the block to produce a 80% steady signal.

With the attenuator changing by 2 dB steps, the signal amplitude shall change corresponding to the figure given below. A deviation of +/- 5% is considered acceptable.

A 50% signal, when reduced by 24 dB, should be

clearly detectable. ( Dynamic range )

Signal to Noise ratio : After setting a signal to 20% screen height, the gain is further increased till the base line noise equals 20%. The difference in gain is the signal to noise ratio and indicates the quality of the amplifier.

Fig 10 Calibration Of Probe 4.5.2 SURFACE PREPARATION

4.5.2.1 Casting shall receive at least an austenitizing heat treatment before being ultrasonically examined.

4.5.2.2 Test surface of casting shall be free of material that will interface with the ultrasonic examination. Surface may be as cast, shoty blasted, ground, or machined.

4.5.2.3 The ultrasonic examination shall be conducted prior to machining prevents an effective examination of the casting.4.5.3 INSPECTION TECHNIQUE

The transmitter circuit of the flaw detector supplies short excitation pulses of few hundred volts at regular interval to the probe crystal. The excitation pulse oscillates the crystal to generate short burst of ultrasound such that the arrival of each returning echo may be identifiable as a discrete event. During the interval between two successive pulses, the crystal is at rest and detects any return echo such as from the back wall. A large percentage of the sound is reflected from the front surface of the test part and the remainder is reflected by the back surface or discontinuities. The flaw detectors CRT screen displays the whole operation by producing separated signals of transmission and the time of arrival of defect echo and the back wall echo. The transmission pulse and subsequent echoes appear as peaks rising out of the CRTs base line. The distance between the peaks is a measure of the defects location or the parts thickness. Transmission of high frequency ultrasound cannot takes place in air. It is carried out through an intermediate liquid, in bulk or as a thin layer. Oily substances or water are generally used. They are called couplants. FIG 11- Working of Ultrasonic Testing The initial or transmitter pulse appears first in time and represents the electrical zero. This is the exact start time of crystal excitation. The exact point in time when ultrasound enters the test material is called acoustical zero. Acoustical zero is superimposed within the initial pulse and is not distinguishable. The next pulse represents the total elapsed time for sound

to travel from the entry surface to the reflector and back to the entry surface again.

At the instant the electrical pulse is removed the oscillations of the crystal do not cease immediately but decreases in an exponential manner until they reach zero. A dead zone is produced, starting immediately after entry into the test surface, in which echoes can not be detected.

One single test cycle is so fast that it is not physically visible in the detectors screen. Hence the flaw detector repeats the test cycle several times per second by supplying successive excitation pulses to the crystal and make the event appear as constant due to persistence of vision. The number of times, the crystal is electrically pulsed per second is called the pulse repetition rate.

A sufficient amount of time between successive pulses is necessary to allow ultrasound to travel through the material under examination. Higher pulse repetition rate produces brighter screen display. Very high pulse repetition rate produces spurious signals [ ghost echoes ] on the CRT screen.

The ultrasonic pulses used by the flaw detector are radio frequency type and have a serrated look. The pulses are filtered and rectified to smooth looking shapes by the flaw detector before display.

Pulse echo A-scan method displays distance along the horizontal scale called the baseline and amplitude of the reflection along the vertical scale. Because of similar return path, the screen is calibrated to display one way travel only.

A scan test method can accurately locate a discontinuity. The amplitude of the return signal is a relative measure of the amount of reflected energy and depends on the area and orientation of the reflecting surface. Amplitude of the signal can be used for accept / reject decision.4.5.4 ACCEPTANCE CRITERIA

No reduction of back reflection of 75% or greater than has been determined to be caused by a discontinuity over an area specified for the applicable quality level of table of ASME SA609 / ASTM A 609.Chapter 5RESULT AND CONCLUSION

RT DEFECT ANALYSIS OF 10 NUMBER () CASTING

Sl. No. FP No. RT No. Report No. Coverage Heat No. Date

1 AD44-2 PKW4034 PK 00101 100% H8317 11/12/2013

2 AD44-2 PKW4099 PK 00257 100% H8667 12/12/2013

3 AD44-2 PKW4129 PK 00305 100% H8698 12/12/2013

4 AD44-2 PKW4145 PK 00367 100% H8719 13/12/2013

5 AD44-2 PKW4151 PK 00392 100% H8808 13/12/2013

6 AD44-2 PKW4153 PK 00394 100% H8699 14/12/2013

7 AD44-2 PKW4154 PK 00397 100% H8877 14/12/2013

8 AD44-2 PKW4193 PK 0512 100% H9023 16/12/2013

9 AD44-2 PKW4197 PK 0527 100% H8995 17/12/2013

10 AD44-2 PKW4245 PK 0668 100% H9200 17/12/2013

Table 1- Defect Analysis Sheet-A

The above table provides the details about the field point number, radiographic testing number, report number, coverage, heat number and utilization. The field point number is the number allotted to the casting based on the their acceptance in the field. Radiographic testing number is the number allotted to them on the order of reaching for radiographic testing. Report number corresponds to the order at which the radiographic result reach the inspectional. Coverage implies to how much a casting is put to test. 100% of each product is covered. Dates of performing the test are shown.

DEFECT ANALYSIS SUMMARY

Heat No. Air inclusion Sand inclusion Shrinkage Crack Piping Total

H8317 10 5 10 0 0 25

H8667 16 2 9 7 13 47

H8698 22 5 12 7 0 46

H8719 4 8 1 8 1 22

H8808 25 11 13 2 3 54

H8699 28 9 9 0 3 49

H8877 27 6 18 0 2 53

H9023 21 11 4 3 1 40

H8995 33 17 11 0 3 64

H9200 20 9 2 2 2 32

Table 2- Defect Analysis Sheet-BThe table above gives the number of each defects. The main defects are air inclusion, sand inclusion, shrinkage, crack, piping. The number of these defects are given in the table. Using these numbers the graph can be plotted.

All the four NDT tests have been done. And radiographic test was done on 10 castings. The chart shows the number of defects in the casting. Air inclusions are shown by blue bar, sand inclusion by the maroon bar, the green bar indicates the shrinkage, violet shows the cracks, light blue shows piping and the total defects is shown by orange colour bar. As per the readings and observation, it is clear that the presence of air inclusion is the most dominant defect among all other defects. So necessary action need to be taken to avoid air inclusion. Chapter 6CONCLUSIONS AND RECOMENTATIONS The amount of each defect in each casting can be seen. The formation of defects is due to flaws in casting design. The casting models with highest amount of defects are noted. This might be due to the flaws in sprue or gate design, presence of impurities etc. Tears and cracks can be reduced by altering the casting design. Bulging and air inclusions can be avoided by proper sealing and reducing shell temperature or increasing radii. Shrinkage occurs due to improper cooling of the casting. To minimize air inclusions, material may be melted in vaccum, in an environment of low solubility gases(Ar,CO2). To prevent gas porosity the material may be melted in a vacuum, in an environment of low-solubility gases, such as argon or carbon dioxide, or under a flux that prevents contact with the air.

To minimize gas solubility the superheat temperatures can be kept low. Turbulence from pouring the liquid metal into the mold can introduce gases, so the molds are often streamlined to minimize such turbulence.

Other methods include vacuum degassing, gas flushing, or precipitation. Precipitation involves reacting the gas with another element to form a compound that will form dross that floats to the top. For instance, oxygen can be removed from copper by adding phosphorus; aluminum or silicon can be added to steel to remove oxygen.

A third source consists of reactions of the molten metal with grease or other residues in the mould.

Hydrogen is normally produced by the reaction of the metal with humidity or residual moisture in the mold. Drying the mold can eliminate this source of hydrogen formation.

REFERENCES[1] Introduction To Non Destructive Testing : a Training Guide By Paul E.[2] Practical Non Destructive Testing By Baldev Raj, T. Jayakumar.[3] Basics Of Non Destructive Testing By Donald Birchon.[4] Non Destructive Testing Handbook By Allgaier, Michael W.[5] Non Destructive Evaluation And Control By ASM International.[6] A Brief Description Of NDT Techniques By Mark Willcox & George Downes.[7] Non-destructive Testing And Evaluation Of Cast Materials N. Parida National Metallurgical Laboraton.[8] Annual Book of ASTM Standards. Metals Test Methods and Analytical Procedures: Nondestructive Testing, section 3, v03.03, American Society for Testing and Materials,Columbus, OH.[9] Non-destructive Testing Of Welded Products At Philosophical Transactions Of The Royal Society Of London[10] Russell Effect On Non-destructive Testing At Philosophical Transactions Of The Royal Society Of London[11] Non-destructive Testing Techniques At Philosophical Transactions Of The Royal Society Of London[12] Non-destructive Methods At Philosophical Transactions Of The Royal Society Of London[13] Non-destructive Testing And Evaluation Of Cast Materials At National Metallurgical Laboratory[14] Efficiency Of Two Non-destructive Testing Methods To Detect Defects At Institute Of Engineering Materials And Biomaterials Dept. of Mechanical Engineering, AWH Engineering college