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Metallurgy & Materials Engineering
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Bilal Hassan Saad Rafique Javed Iqbal Saqib Fraz Amanullah Submitted To:_______________ Signature:__________________ Dated:_____________________
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Aknowledgment
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Introduction KSEW
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NDT & Types
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Radiography Testing
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Ultrasonic Testing
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Magnetic Particle Inspection
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Dye Penetration Inspection
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Acknowledgements
All the praises are for the almighty, Allah who bestowed me with the ability and potential to complete this Internship. We also pay our gratitude to the Almighty for enabling us to complete this Internship Report within due course of time.
Words are very few to express enormous humble obligations to my affectionate Parents for their prayers and strong determination to enabling me to achieve this job.
We take this opportunity to record our deep sense of gratitude and appreciation to our Internship Advisor Mr.Abdul Waheed Bhuttoo, Department of Metallurgy and Materials Engineering, Dawood College Of Engineering & Technology Karachi for his constant encouragement and inspiring guidance with his Wisdom.
We also appreciate the cordial co-operation from all our concern Managers in the department of Engineering Quality Control (EQC) especially Mr,Abdul Majeed Billoo (DGM), Mr.Ghufran Ahmad (ASP),Mr.M.A Wadood QC (UT), Mr.Irfan (UT), Mr.Altaf (UT),Mr.Ahad (RT/DPT),Mr.Obaid (RT),Mr.Rashid (RT),Mr.Rashid (MPI) and Admin & HR management for providing me requisite information information and knowledge for compilation of our complete Internship.
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Introduction To Karachi Shipyard & Engineering Works (KSEW )
Karachi Shipyard is the oldest Heavy Engineering Works of Pakistan of Pakistan which is catering for its Ship Building, Ship Repairing, Submarine/Warship Construction and Heavy/General Engineering requirements. KSEW was established in early 1950 1950''s as a project of PIDC. It was incorporated as a public limited company in 1957 1957.. The shipyard spread over an area of 29 hectares (71 acres). KSEW has a large Ship Building Hall, three Ship Building Berths, two Dry Docks, three Foundries (Iron, Steel & Non-Ferrous), Fabrication Shops, one machine shop and other supporting facilities like Carpentry, Pipe Fitting and Light Karachi Shipyard is strategically located on the cross roads of South Asia and Gulf region. It is designed to carryout Shipbuilding and Shiprepair business for the local and foreign customers. The major local customers - PN, PNSC, MSA, KPT, PQA, GPA in the public sector and vide range of customers in the private sector have been well served o ver the last forty seven years. Facilitates installed, are suited to build and repair medium size ships up to 18,000 TDW and multipurpose cargo vessels up to 26,000TDW. Today, KS&EW enjoys a unique status of a public limited company with its entire shares owned by the Government of Pakistan under the administrative control of Ministry of Defence (as an autonomous body). While, still remaining in public sector, it maintains, corporate sector outlook and work methodology. It is the first state owned organization to have acquired ISO 9001 : 2000 certification. Till Till to date, it has built 434 ships, repaired 5000 vessels and built over 2000 heavy engineering units suiting the requirements of local and foreign clients. Steel Fabrication Shop. KSEW is working as an autonomous commercial organization under the Ministry of Defence, Government of Pakistan.
Karachi Shipyard is the only shipbuilding company in Pakistan. It has built numerous cargo ships,tugboats and support vessels, naval vessels and submarines.
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Non Destructive testing Nondestructive testing (NDT) is a wide group of analysis techniques used in science and industry to evaluate the properties of a material, component or system without causing damage. The terms Nondestructive examination (NDE), Nondestructive inspection (NDI), and Nondestructive evaluation (NDE) are also commonly used to describe this technology. Because NDT does not permanently alter the article being inspected, it is a highly-valuable technique that can save both money and time in product evaluation, troubleshooting, and research. Common NDT methods includeultrasonic includeultrasonic,, magnetic-particle magnetic-particle,, liquid penetrant, penetrant, radiographic radiographic,, remote visual inspection (RVI), eddy-current testing, testing, and low coherence interferometry. interferometry. NDT is a commonly-used tool in forensic engineering, engineering, mechanical engineering, engineering, electrical engineering, engineering, civil engineering, engineering, systems engineering,,aeronautical engineering, engineering engineering, medicine medicine,, and art art..
Training
Non-Destructive Testing (NDT) (NDT) training is provided for people working in the "steel" industry. It is generally necessary that the student successfully completes a theoretical training program (usually 40 hours of classroom training), as well as have performed several hundred hours of practical application of the particular method they wish to be trained in. At this point, they can apply to write a certifying exam with one of the few governing bodies. Getting certified to inspect steels is quite a complex, and difficult process. Further, NDT Training has recently become available online. WorldSpec.org is one of the innovative companies that helped pioneer this new "era" in NDT Training.
Examples
Welds In manufacturing, welds are commonly used to join two or more metal surfaces. Because these connections may encounter loads and fatigue during product lifetime, there is a chance that they may fail if not created to proper specification proper specification.. For example, the base metal must reach a certain temperature during the welding process, must cool at a specific rate, and must be welded with compatible materials or the joint may not be strong enough to hold the surfaces together, or cracks may form in the weld causing it to fail. The typical welding defects, lack of fusion of the weld to the base metal, cracks or porosity inside the weld, and variations in weld density, could cause a structure to break or a pipeline to rupture. Welds may be tested using NDT techniques such asindustrial radiography using Xrays or gamma rays,ultrasonic testing, liquid penetrant testing or via eddy current. In a proper
6 weld, these tests would indicate a lack of cracks in the radiograph, show clear passage of sound through the weld and back, or indicate a clear surface without penetrant captured in cracks elding techniques may also be actively monitored with acoustic emission techniques before production to design the best set of parameters to use to properly join two materials. Structural mechanics Structures can be complex systems that undergo different loads during their lifetime. Some complex structures, such as the turbomachinery in a liquid-fuel rocket, rocket, can also cost millions of dollars. Engineers will commonly model these structures as coupled second-order systems, approximating dynamic structure components with springs springs,, masses masses,, and dampers dampers.. These sets of differential equations can be used to derive a transfer function that models the behavior of the system. In NDT, the structure undergoes a dynamic input, such as the tap of a hammer or a controlled impulse. Key properties, such as displacement or acceleration or acceleration at different points of the structure, are measured as the corresponding output. This output is recorded and compared to the corresponding output given by the transfer function and the known input. Differences may indicate an inappropriate model (which may alert engineers to unpredicted instabilities or performance outside of tolerances), failed components, or an inadequate control system Methods
NDT methods may rely upon use of electromagnetic of electromagnetic radiation, radiation, sound sound,, and inherent properties of materials to examine samples. This includes some kinds of microscopy of microscopy to examine external surfaces in detail, although sample p reparation techniques for metallography for metallography,, optical microscopy and electron microscopy are generally destructive as the surfaces must be made smooth through polishing or the sample must be electron transparent in thickness. The inside of a sample can be examined with penetrating electromagnetic radiation, such as X-rays or 3D or 3D Xrays for volumetric inspection. Sound waves are utilized in the case of ultrasonic testing. Contrast between a defect and the bulk of the sample may be enhanced for visual examination by the unaided eye by using liquids to penetratefatigue penetratefatigue cracks. One method (liquid (liquid penetrant testing) testing) involves using dyes, fluorescent or non-fluorescing, in fluids for non-magnetic materials, usually metals. Another commonly used method for magnetic materials involves using a liquid suspension of fine iron particles applied to a part while it is in an externally applied magnetic field (magnetic-particl magnetic-particle e testing testing). ). Thermoelectric effect (or use of theSeebeck theSeebeck effect) effect) uses thermal properties of an alloy to quickly and easily characterize many alloys. The chemical test, test, or chemical spot test method, utilizes application of sensitive chemicals that can indicate the presence of individual alloying elements. There are four non destructive mrthods are used.
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Radiography (RT) Ultrasonic testing (UT) Dye penatrant testing (DPT) Magnetic Partical Inspection Inspection (MPI) Eddy Current
RADIOGRAPHY
X and gamma radiations, because of their unique ability to penetrate material and disclose discontinuities, have been applied to the radiographic (X-ray) inspection of metal fabrications and nonmetallic products.
7 The penetrating radiation is projected through the part to be inspected and produces an invisible or latent image in the film. When processed, the film becomes a radiograph or shadow p icture of the object. This inspection medium, in a portable unit, provides a fast and reliable means for checking the integrity of airframe structures and engines. Radiographic inspection techniques are used to locate defects or flaws in airframe structures or engines with little or no disassembly. This is in marked contrast to other types of nondestructive testing, which usually require removal, disassembly, and stripping of paint from the suspected part before it can be inspected. Due to the nature of X-ray, extensive training is required to become a qualified radiographer, and only qualified radiographers are allowed to operate the Xray units. Three major steps in the X-ray process discussed in subsequent paragraphs are: (1) Exposure to radiation, including preparation, (2) processing of film, and (3) interpretation of the radiograph.
Preparation and Exposure
The factors of radiographic exposure are so interdependent that it is necessary to consider all factors for any particular radiographic exposure. These factors include, but are not limited to, the following: (a) Material thickness and density. (b) Shape and size of the object. (c) Type of defect to be detected. (d) Characteristics of X-ray machine used. (e) The exposure distance. (f) The exposure angle. (g) Film characteristics. (h) Types of intensifying screen, if used. Knowledge of the X-ray unit's capabilities should form a background for the other exposure factors. In addition to the unit rating in kilovoltage, the size, portability, ease of manipulation, and exposure particulars of the available equipment should be thoroughly understood. Previous experience on similar objects is also very helpful in the determination of the overall exposure techniques. A log or record of previous exposures will provide specific data as a guide for future radiographs. Film Processing
After exposure to X-rays, the latent image on the film is made permanently visible by processing it successively through a developer chemical solution, an acid bath, and a fixing bath, followed by a clear water wash. The film consists of a radiation sensitive silver salt suspended in gelatin to form an emulsion. The developer solution converts radiation affected elements in the emulsion to black metallic silver. These black metallic particles form the image. The longer the film remains in the developer, the more metallic silver is formed, causing the image to become progressively darker. Excessive time in the developer solution results in overdevelopment.
8 An acid rinse bath, sometimes referred to as a stop bath, instantly neutralizes the action of the developer and stops further development. Due to the soft emulsion and the nonabsorbent quality of the base of most negative materials, only a very weak a cid bath is required. The purpose of the fixing bath is to arrest the image at the desired state of development. When a radiation sensitive material is removed from the developing solution, the emulsion still contains a considerable amount of silver salts which have not been affected by the developing agents. These salts are still sensitive, and if they are allowed to remain in the emulsion, ordinary light will ultimately darken them and obscure the image. Obviously, if this occurs, the film will be useless. The fixing bath prevents this discoloration by dissolving the salts of silver from the developed free silver image. Therefore, to make an image permanent, it is necessary to fix the radiation sensitive material by removing all of the unaffected silver salt from the emulsion. After fixing, a thorough water rinse is necessary to remove the fixing agent which, if allowed to remain, will slowly combine with the silver image to produce brownish-yellow stains of silver sulfide, causing the image to fade. NOTE: All processing is conducted under a subdued light of a color to which the film is not readily sensitive. Radiographic Interpretation
From the standpoint of quality assurance, radiographic interpretation is the most important phase of radiography. It is during this phase that an error in judgment can produce disastrous consequences. The efforts of the whole radiographic process are centered in this phase; the part or structure is either accepted or rejected. Conditions of unsoundness or other defects which are overlooked, not understood, or improperly interpreted can destroy the purpose and efforts of radiography and can jeopardize the structural integrity of an entire aircraft. A p articular danger is the false sense of security imparted by the acceptance of a part or structure based on improper interpretation. As a first impression, radiographic interpretation may seem simple, but a closer analysis o f the problem soon dispels this impression. The subject of interpretation is so varied and complex that it cannot be covered adequately in this type of document. Instead, this chapter will give only a brief review of basic requirements for radiographic interpretation, including some descriptions of common defects. Experience has shown that, whenever possible, radiographic interpretation should be conducted close to the radiographic operation. It is helpful, when viewing radiographs, to have access to the material being tested. The radiograph can thus be compared directly with the material being tested, and indications due to such things as surface condition or thickness variations can be immediately determined. The following paragraphs present several factors which must be considered when analyzing a radiograph. There are three basic categories of flaws: voids, inclusions, and dimensional irregularities. The last category, dimensional irregularities, is not pertinent to these discussions because its prime factor is one of degree, and radiography is not that exacting. Voids and inclusions may appear on the radiograph in a variety of forms ranging from a two dimensional plane to a three dimensional sphere. A crack, tear, or cold shut will most nearly resemble a two dimensional plane, whereas a cavity will look like a three dimensional sphere. Other types of flaws, such as shrink, oxide inclusions, porosity, etc., will fall somewhere between these two extremes of form.
9 It is important to analyze the geometry of a flaw, especially for such things as the sharpness of terminal points. For example, in a crack-like flaw the terminal points will appear much sharper than they will for a sphere-like flaw, such as a gas cavity. Also, material strength may be adversely affected by flaw shape. A flaw having sharp points could establish a source of localized stress concentration. Spherical flaws affect material material strength to a far lesser degree than do sharp pointed flaws. Specifications and reference standards usually stipulate that sharp pointed flaws, such as cracks, cold shuts, etc., are cause for rejection. Material strength is also affected by flaw size. A metallic component of a given area is designed to carry a certain load plus a safety factor. Reducing this area by including a large flaw weakens the part and reduces the safety factor. Some flaws are often permitted in components because of these safety factors; in this case, the interpreter must determine the degree of tolerance or imperfection specified by the design engineer. Both flaw size and flaw shape should be considered carefully, since small flaws with sharp points can be just as bad as large flaws with no sharp points. Another important consideration in flaw analysis is flaw location. Metallic components are subjected to numerous and varied forces during their effective service life. Generally, the distribution of these forces is not equal in the component or part, and certain critical areas may be rather highly stressed. The interpreter must pay special attention to these areas. Another aspect of flaw location is that certain types of discontinuities close to one another may potentially serve as a source of stress concentrations; therefore, this type of situation should be closely scrutinized. An inclusion is a type of flaw which contains entrapped material. Such flaws may be either of greater or lesser density than the item being radiographed. The foregoing discussions on flaw shape, size, and location apply equally to inclusions and to voids. In addition, a flaw containing foreign material could become a source of corrosion. Radiation Hazards
Radiation from X-ray units and radioisotope sources is destructive to living tissue. It is universally recognized that in the use of such equipment, adequate protection must be provided. Personnel must keep outside the primary X-ray beam at all times. Radiation produces changes in all matter through which it passes. This is also true of living tissue. When the radiation strikes the molecules of the body, the effect may be no more than to dislodge a few electrons, but an excess of these changes could cause irreparable harm. When a complex organism is exposed to radiation, the degree of damage, if any, depends o n which of its body cells have been changed. The more vital organs are in the center of the body; therefore, the more penetrating radiation is likely to be the most harmful in these areas. The skin usually absorbs most of the radiation and, therefore, reacts earliest to radiation. If the whole body is exposed to a very large dose of radiation, it could result in death. In general, the type and severity of the pathological effects of radiation depend on the amount of radiation received at one time and the percentage of the total body exposed. The smaller doses of radiation may cause blood and intestinal disorders in a short period of time. The more delayed effects are leukemia and cancer. Skin damage and loss of hair are also possible results of exposure to radiation.
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Apparatus
Radiographs
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ULTRASONIC TESTING In ultrasonic testing (UT), very short ultrasonic pulse-waves with center frequencies ranging from 0.1-15 MHz and
occasionally up to 50 MHz are launched into materials to to detect internal flaws flaws
or to characterize materials. The technique is also commonly used to determine the thickness of the test object, for exa mple, to monitor pipework corrosion. Ultrasonic testing is often performed on steel and other metals and alloys, though it can also be used on concrete, wood and composites, albeit with less resolution. It is a form of non-destructive testingused in many industries including aerospace, automotive and other transportation sectors. PRINCIPLE In ultrasonic testing, an ultrasound transducer connected to a diagnostic machine is passed over the object being inspected. The transducer is typically separated from the test object by a couplant (such as oil) or by water, as in immersion testing. There are two methods of receiving the ultrasound waveform, reflection and attenuation. In reflection (or pulse-echo) mode, the transducer performs both the sending and the receiving of the pulsed waves as the "sound" is reflected back to the device. Reflected ultrasound comes from an interface, such as the back wall of the object or from an imperfection within the object. The diagnostic machine displays these results in the form of a signal with an amplitude representing the intensity of the reflection and the distance, representing the arrival time of the reflection. In attenuation (or through-transmission) mode, a transmitter sends ultrasound through one surface, and a separate receiver detects the amount that has reached it on another surface after traveling through the medium. Imperfections or other conditions in the space between the transmitter and receiver reduce the amount of sound transmitted, thus revealing their presence. Using the couplant increases the efficiency of the process by reducing the losses in the ultrasonic wave energy due to separation between the surfaces.
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USES OF UT • •
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It is sensitive to both surface and subsurface discontinuities. The depth of penetration for flaw detection or measurement is superior to other NDT methods. Only single-sided access is needed when the pulse-echo technique is used. It is highly accurate in determining reflector position and estimating size and shape. Minimal part preparation is required. Electronic equipment provides instantaneous results. Detailed images can be produced p roduced with automated systems. It has other uses, such as thickness measurement, in addition to flaw detection
Limitations of UT • • •
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Surface must be accessible to transmit ultrasound. Skill and training is more extensive than with some other methods. It normally requires a coupling medium to promote the transfer of sound energy into the test specimen. Materials that are rough, irregular in shape, very small, exceptionally thin or not homogeneous are difficult to inspect.
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Cast iron and other coarse grained materials are difficult to inspect due to low sound transmission and high signal noise. Linear defects oriented parallel to the sound beam may go undetected. Reference standards are required for both equipment calibration and the characterization of flaws.
Magnetic particle inspection (MPI) (MPI ) Magnetic particle inspection (MPI) is a non-destructive testing (NDT) process for detecting surface and subsurface discontinuities in ferroelectric materials such as iron, nickel, cobalt, and some of their alloys. The process puts a magnetic field into the part. The piece can be magnetized by direct or indirect magnetization. Direct magnetization magnetization occurs when the electric current is passed through the test object and a magnetic field is formed in the material. Indirect magnetization occurs when no electric current is passed through the test object, but a magnetic field is applied from an outside source. The magnetic lines of force are perpendicular to the direction of the electric current which may be either alternating current (AC) or some form of direct current (DC) (rectified AC). The presence of a surface or subsurface discontinuity in the material allows the magnetic flux to leak. Ferrous iron particles are applied to the part. The particles may be dry or in a wet suspension. If an area of flux leakage is present the particles will be attracted to this area. The particles will build up at the area of leakage and form what is known as an indication.
MPI PROCESS: PROCESS :
14 Magnetic particle inspection (MPI) is used for the detection of surface and near-surface flaws in ferromagnetic materials. A magnetic field is applied to the specimen, either locally or overall, using a permanent magnet, electromagnet, flexible cables or hand-held prods. If the material is sound, most of the magnetic flux is concentrated below the material's surface. However, if a flaw is present, such that it interacts with the magnetic field, the flux is distorted locally and 'leaks' from the surface of the specimen in the region of the flaw. Fine magnetic particles, applied to the surface of the specimen, are attracted to the area of flux leakage, creating a visible indication of the flaw. The materials commonly used for this purpose are black iron particles and red or yellow iron oxides. In some cases, the iron particles are coated with a fluorescent material enabling them to be viewed under a UV lamp in darkened conditions. Magnetic particles are usually applied as a suspension in water or paraffin. This enables the particles to flow over the surface and to migrate to any flaws. On hot surfaces, or where contamination is a concern, dry powders may be used as an alternative to wet inks. On dark surfaces, a thin layer of white paint is usually applied, to increase the contrast between the background and the black magnetic particles. The most sensitive technique, however, is to use fluorescent particles viewed under UV (black) light. MPI is particularly sensitive to surface-breaking or near-surface cracks, e ven if the crack opening is very narrow. However, if the crack runs parallel to the magnetic field, there is little disturbance to the magnetic field and it is unlikely that the crack will be detected. For this reason it is recommended that the inspection surface is magnetised in two directions at 90° to each other. Alternatively, techniques using swinging swinging or rotating magnetic fields can be used to ensure that all orientations of crack are detectable. The method of magnetisation depends on the geometry of the component and whether or not all or only part of the specimen is to be magnetised. Permanent magnets are attractive for on-site inspection, as they do not need a power supply. However, they tend only to be used to examine relatively small areas and have to be pulled from the test surface. Despite needing their own power supply, electromagnets (yokes) find widespread application. Their main attraction is that they are easy to remove (once the current has been switched off) and that the strength of the magnetic field can be varied. For example, an AC electromagnet can be used to concentrate the field at the surface where it is needed. Hand-held electrical prods are useful in confined spaces. However, they suffer two major disadvantages that can rule out their use u se altogether. Firstly, arc strikes can occur at the prod contact points and these can damage the specimen surface. Secondly, because the particles must be applied when the current is on, the inspection becomes a two-man operation. Bench units are fixed installations used to test large numbers of manufactured specimens of various sizes. The electrical components of a mobile unit (as described above) are incorporated in the bench unit making testing more rapid, convenient and efficient. In some cases, MPI can leave residual fields which subsequently interfere with welding repairs. These can be removed by slowly wiping the surface with an energised AC yoke. USES
MPI is often used to look for cracking at welded joints and in areas identified as being susceptible to environmental cracking (e.g. stress corrosion cracking o r hydrogen induced cracking), fatigue cracking or creep cracking. Wet fluorescent MPI finds widespread use in looking for environmental damage on the inside of vessels.
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Dye penetrant inspection (DPI) (DPI ) 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 allnon-porous materials (metals, plastics, or ceramics). The penetrant may be applied to all non-ferrous materials and ferrous materials, but for inspection of ferrous components magnetic-particl magnetic-particle e inspection is also preferred for its subsurface detection capability . LPI is used to detect casting, forging and welding surface defects such as cracks,suface porosities, and leaks in new products, and fatigue cracks on in-service components.
Principle DPI is based upon capillary action, 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, a developer is applied. The developer helps to draw penetrant out of the flaw where a visible indication becomes visible to the inspector. Inspection is performed under ultraviolet or white light, depending upon the type of dye used - fluorescent or nonfluorescent (visible).
The main steps of Liquid Penetrant Inspection : 1. Pre-cleaning: 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 includesolvents includesolvents,, alkaline cleaning steps, vapor degreasing, 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-bath treatment. 2. Application of Penetrant: Penetrant : The penetrant is then applied to the surface of the item being tested. The penetrant is allowed time to soak into any flaws (generally 5 to 30 minutes)is called dwell time. The dwell time time mainly depends upon the penetrant being used, material being testing 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.
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3. Excess Penetrant Removal: 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, solvent-removable, lipophilic post-emulsifiable, or hydrophilic 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. 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 acetone,,isopropyl alcohol, 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
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the indications found may require some training and/or experience [the indication size is not the actual size of the defect] 5. Inspection: 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 Inspection of the test surface should take p lace after a 10 minute development time. 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 postinspection coating processes are scheduled.
The End
