Asnt level iii study guide basic free download pdf

Many users routinely verify the performance of each incoming batch of penetrant materials, Reference B Penetrant Properties Formulation of a liquid penetrant is a complex process because of the numerous and frequent conflicting requirements.

This conflicts with the need to be able to remove the excess surface penetrant. Another requirement of equal importance is the visibility or contrast between the penetrant indication and the surface background. Unfortunately, there is neither a fixed rule for formulating a liquid penetrant nor a set of criteria that will provide a satisfactory produet. However, there are some fundamental prerequisites that are necessary for aeceptable performance. The penetrant must: 1.

Reference A Reference B Hazardous Characteri Safety is a concern because of the possible hazardous characteristics of each material used in compounding penetrants, emulsifiers and developers.

Federal law requires the manufacturer to identity and define the hazardous characteristics of each material used in its formulation. Whenever a change in materials is made, the manufacturer must update the materials safety data sheet. For more information, see Chapter 9, Safery, Health and Disposal. Complicating this requirement is the fact that many of the parts tested by the penetrant method are subsequently subjected to varying temperatures.

There may be no chemical attack at room temperature, but if traces of penetrant are left on the part and it is subjected to elevated temperatures, then pitting, intergranular corrosion or stress corrosion may occur. All penetrant materials must be subjected to three corrosion tests: moderate temperature corrosion, high temperature stress corrosion and high temperature corrosion of nickel based alloys. This makes i very difficult to see when it is entrapped in small surface openings and voids.

A dye or blend of dyes is dissolved in the vehicle to provide a high contrast, readily visible indication. Two types of dyes are usually used, visible or fluorescent Visible Dyes Visible dye penetrants, also called color contrast penetrants, are viewed under visible light and are available in red, orange or purple.

The most frequently used dyes are red because they provide high contrast with the developer and many metallic surfaces. They are inexpensive and readily dissolve in the penetrant oil, When used with emulsifiers or solvents to remove the excess surface penetrant, the small amount of penetrant trapped in the surface discontinuity is diluted when it spreads through the developer. To compensate for this, the deepest shade of red and the highest concentration of dye that can be dissolved in the oil without precipitation is used.

The red dyes are visible in very thin films, however, fluorescent dyes are visible in even thinner films. One of the basic reasons that a visible dye is considered to be less sensitive than a fluorescent dye is that fluorescent penetrants can locate an indication with a smaller, thinner volume of oil. The primary advantage of a visible penetrant is that it can be used with ordinary shop lighting and it can be applied from a small portable kit.

Fluorescent Dyes Some minerals and chemical compounds have the ability to emit visible light when exposed to short wavelength energy X-rays, ultraviolet light. The mechanism of fluorescence involves the atomic structure of the fluorescent material and the energy level and quantity of the exciting radiation. A material will fluoresce only if it has a specific atomic structure.

This is an abnormal or unbalanced condition; the displaced electron quickly returns to its normal shell. In returning to equilibrium, the electron releases the excess energy as electromagnetic radiation. Fluorescent penetrant dyes are designed to fluoresce when exposed to nm wavelength ultraviolet light, The released energy always has a longer wavelength than the exciting radiation.

The released energy in fluorescent materials has a wavelength of nm to nm, which is in the visible light range. The wavelength of released energy depends on the type of dye used. Fluorescent penetrant dyes are usually in the range of nm to nm, which is in the visible spectrum of green to yellow.

Viscosity varies widely with temperature, decreasing when temperatures are raised and increasing when temperatures are lowered. Viscosity is an important factor in the application process of both penetrant and lipophilic emulsifiers. Viscosity has no effect on penetrating ability; some very viscous fluids, such as molasses, have Very good penetrating ability, while some low viscosity fluids, such as pure water, have very poor penetrating ability.

From an application viewpoint, viscosity affects the rate of penetration and higher viscosity fluids require a longer penetration time. Viscosity also determines how much penetrant or emulsifier remains on the part surface at the end of the dwell time. High viscosity penetrants cling to the part surface and require increased effort in removal. High viscosity emulsifiers are slow to diffuse into penetrant and require an increased emulsifier dwell time.

The manufacturer must state the nominal viscosity of each penetrant and lipophilic emulsifier. The flash point does not affect the performance of a penetrant, but it is important as a safety precaution. Flash point requirements have changed through the years. Penetrant materials packaged in aerosol containers are not affected, but must be labeled in accordance with CFR This is confirmed by testing samples submitted for qualification to the specification requirements. Temperature Stability Temperature stability is a requirement of the newer specification and should not be confused with thermal stability.

Temperature stability refers to the resistance to separation of penetrants and emulsifiers when exposed to temperatures outside of the recommended processing range. Sensitivity When used to describe a penetrant performance characteristic, sensitivity is defined as the ability to produce a visible indication from very small, tight surface openings. It involves both penetrating ability and contrast with surface background. The penetrant must enter and exit the discontinuity with enough dye to produce a noticeable indication.

Test panels of titanium and nickel alloy containing very small, laboratory generated fatigue cracks are first processed using the applicable reference standard penetrant system.

The luminance of the resulting indications is measured using a photometer to standardize the testing equipment. The panels are then cleaned and reprocessed using the penetrant system to be evaluated. The resulting luminance numbers must equal or exceed those of the reference standard material. Thete is only one set of qualification test panels.

The US Air Force is the qualifying agency and maintains the test panels, It is not possible to duplicate fatigue cracks with identical penetrant system performance characteristics. Therefore, nonqualification comparison tests are performed using a variety of test panels, such as cracked nickel chromium plates, alternate fatigue cracked panels and actual service cracked parts. While visible dye Type [1 penetrants are not classified by sensitivity level, they do have to meet certain minimum requirements.

The test depends on the visual comparison of indications on thermal cracked aluminum blocks. Half of the block is processed with the reference standard penetrant system and the other half is processed with the material that is being evaluated. After processing, the two halves are visually compared.

The penetrant under evaluation must produce indications equal to or greater than the standard Figure 2. The generai rule is to use the lowest sensitivity that will reveal the possible discontinuities. Difficulties can arise if the sensitivity is cither too low or too high.

Low sensitivity levels may not reveal potentially harmful discontinuities, while a sensitivity level that is too high can result in a residual background that could obscure any discontinuity indications. Reference B Fluorescent Intensity Fluorescent intensity is the amount of visible light given off when fluorescent dye is exposed to ultraviolet light. There are a number of variables, that influence fluorescent intensity. Some of these are: 1. Variables that can be controlled by the operator are the intensity of the ultraviolet light impinging on the surface and the thickness of the penetrant film emulsifying, washing and developing.

The other variables are controlled by the penetrant manufacturer. Increasing the amount of dye in solution proportionally increases the fluorescent intensity. The absorptivity and quantum yield are characteristics of the dye system. These are controlled by the dye blends, because most penetrant systems contain a blended dye.

A second dye can be selected that has a good absorptivity where the activator dye has its peak emission. The second dye, called a colorforming dye, will emit in the to nm range.

This interaction of different dye types is called cascading. A thin film is achieved by accurately ting both the standard and material to be tested. Four small squares of filter paper are dipped into the dihited reference standard and four squares are dipped into the diluted test material.

The samples are then dried. This produces a thin, uniform film of penetrant on the filter paper squares. The fluorescent intensity on both the reference standard and test material are measured using a fluorometer. Reference A Reference B Ultraviolet Stability The efficiency of fluorescent dyes in converting ultraviolet light to visible light is reduced by prolonged exposure to ultraviolet light.

The test for ultraviolet stability is performed in a manner similar to the test for fluorescent intensity ASTM E' with the following changes. No reference standard specimens are necessary. Five of the dried specimens are then phiced ina dorkened area such as a desk drawer. The remaining five specimens are exposed to 80 mWem?

The minimum accepted averaged values are: 1. Five of the test specimens are pkiced in a location away trem strong light. Afier exposure, the Muoreseent intensity is measured according w ASTM E Altemating between exposed and unexposed samples is recommended. At the end of the period. Method A penetrants shall show no gelling. The manufacturers carefully formulate the emulsifiers depending on the penetrant to he used.

The surface roughness of the test item bas an effect on the test. Smooth machined parts are enstly emubsified, white rough surface pants require a more aetive emulsifier. Oxerremowall is tested during the sensitivity test because removal of entrapped penetrant will decrease sensitivity on the relatively smooth panels, Urwerremoval, which causes excessive background. Procedures for produeing and testin the panels and the type of washing apparatus to be used are detailed in SAE-AMS, Four of the panels are processed in the applicable reference standard system and four are processed in the system to be tested.

They consist of dipping the test samples and allowing them te dain tor approximately 10 min while at a 60 degree angle: Procedures for washing, drying emulsifying and applying developer vary slightly. Afier processing. Three measurements are made on cach panel.

Study Guide: Liquid Penetrant Testing standard, Penetrant systems should leave no more residual penetrant than the same sensitivity level reference standard. These chemicals are called emulsifiers. Ideally, during removal of surface penetrant, all excess surface penetrant should be removed from all surface areas including fillets, comers and recesses without removing penetrant entrapped in discontinuities. Formulating the ideal emulsifier mixture is a delicate balancing act.

A mixture that is too aggressive will leave a clean surface but will also remove entrapped penetrant, while a low aggressive mixture will leave an excessive background, Fach manufacturer has its own formulation for penetrants and the emulsifiers must be formulated for that specific penetrant except for solvent removers.

Emulsifiers from one manufacturer may not perform satisfactorily on a different manufacturer's penetrant. Generally, emulsifiers are tested for sensitivity and removability during the penetrant tests. Water washable or selfemulsifiable penetrants Method A contain emulsifier as an integral part of their formulation.

Adding a lipophilic emulsifier toa postemulsifiable penetrant will not produce a satisfactory water washable penetrant. Because water washable penetrants already contain an emulsifier, they are susceptible to water contamination.

They must also meet the requirement for tank life without separation of emulsifier from. Lipophilic emulsifier Method B is a type of Jiguid soap that will diffuse into the penetrant, producing a mixture that can be removed with a water spray. These emulsifiers are required to be a distinctly different color from the penetrant. The three properties of lipophilic emulsifiers that control the washing characteristics are activity, viscosity and water tolerance.

These properties are factored against the characteristics of the oil based penetrant. If a penetrant is highly resistant to water, an emulsifier with a high activity is needed.

The rate of diffusion of the emulsifier into the penetrant depends on the viscosity of the emulsifier. High osity emulsifiers diffuse more slowly than low viscosity emulsifiers.

A highly active emulsifier with a low viscosity can be adjusted by blending it with a more viscous emulsifier to provide the desired washing characteristics. As water is added to the emulsifier, the emulsifier gels, separates or coagulates. As parts are processed through the emulsifier, some of the surface penetrant dissolves in the emulsifier. Udaya Sundar. A short summary of this paper. Subsequent printings of the document will incorporate the corrections into the published text.

In order to verify the print run of your book, refer to the copyright page. Ebooks are updated as corrections are found. In the right-hand column, the last paragraph should be changed to read: Paintbrush transducers are mosaics that are excited as a single element search-unit with a large length-to-width ratio and are used to sweep across large segments of material in a single pass.

Question 2 should be changed to read: 2. The wave may be totally reflect- If the sound energy is partially transmitted beyond ed if the incident angle is sufficiently large. Figure 1 a shows normal reflec- wave energies as a function of the incident angle for tion and partial transmission, while Figure 1 b shows oblique reflection and the partition of waves into reflected and transmitted wave modes.

When Equation 5 is expressed for pressure waves rather than the energy contained in the waves, the terms in parentheses are Figure 2: Reflection and transmission coefficients versus not squared. Sound waves continue to travel until: 6.

The equations that show VL and VT being dependent on elastic properties suggest that: a. Wavelength may be defined as: d. VT will always be one-half of VL in the same material. Velocity measurements in a material revealed that the b. This material c. To determine wavelength: d. What is the most c. The wavelength of a 5 MHz sound wave in water is b. It can be deduced from Table 2 that the densities of: c.

Thickness resonance occurs when transducers c. The acoustic energy reflected at a plastic glass-quartz a. Table 2: Piezoelectric material characteristics. The couplant should be spread in a thin, uniform film between the transducer and the mate- rial under test. Rough surfaces and vertical or over- where head surfaces require a higher viscosity couplant R is the lens radius of curvature, than smooth, horizontal surfaces. Because stainless steels and other high-nickel For example, to get a focal length of In a few highly specialized applications, dry Focusing has three principal advantages.

First, the couplants, such as a sheet of elastomer, have been energy at the focal point is increased, which increases used. Bonding the transducer to the test item, usu- the sensitivity or signal amplitude. Second, sensitivity ally in distributed materials characterization studies, to reflectors above and below the focal point is is an accepted practice.

High pressure and intermit- decreased, which reduces the noise. Third, the lateral tent contact without a coupling medium, has also resolution is increased because the focal point is nor- been used on high-temperature steel ingots. It is inexpensive, plentiful and frame. When examined from the composite side, relatively inert to the materials involved. It is some- there are many echoes from within the composite times necessary to add wetting agents, antirust that interfere with the desired interface signal; how- additives and antifouling agents to the water to pre- ever, focusing at the bondline reduces the interfer- vent corrosion, ensure absence of air bubbles on test ence and increases system sensitivity and resolution part surfaces and avoid the growth of bacteria and at the bond line depth.

Bubbles are removed from both the transduc- Where a shape other than a simple round or er face and the material under examination by regu- square transducer is needed, particularly for larger- lar wiping of these surfaces or by water jet. Mosaic higher, more concentrated beam that results in bet- assemblies may be linear, circular or any combina- ter lateral spatial resolution in the vicinity of the tion of these geometries.

With properly timed focal zone. This focusing moves the last peak of the sequences of exciting pulses, these units can func- near field closer to the transducer than that found tion as a linear array with steerable beam angles with a flat transducer. Lenses may be formed from or as transducers with a variable focus capability. Paintbrush transducers are mosaics that are The radius of curvature is determined using excited as a single element search-unit with a Equation 4.

The sound beam is broad and the lateral resolution and discontinuity sensitivity is not as good as small- er transducers. Which of the following is a true statement about a In Figure 6 and using the conditions of question 13, sound beam with a longer wavelength.

A longer wavelength has better penetration than a shorter wavelength. A longer wavelength provides a greater sensitivity b. A longer wavelength has less energy than a d. Wavelength does not affect penetration, It is desired to detect discontinuities 6.

The search unit must be selected Backing material on a transducer is used to: with the choice between a narrow band and a broadband unit. Which should be chosen and why? The narrow band unit because it examines only a b. The broadband unit because the entire volume is d. The broadband unit because the near surface Angle beam search units are used to: resolution is better. The broadband unit because the lateral resolution a. In a longitudinal-wave immersion test of d.

What is the approximate incident angle? Several sections have been expanded including the sections on UV light, indications, surface discontinuities, welding discontinuities, subsurface discontinuities and interpretations, and on UV light hazards. Many new chapter review questions were added.

This second edition Study Guide was extensively revised and updated to better cover the training outlines in CP and includes new chapters and color photographs. The new chapters cover interpretation and evaluation; codes, regulations, and standards; friction and fluid flow investigations; exothermic or endothermic investigations; imagers and heat-flux indicators; contact temperature indicators; safety, and more. Many new review questions follow every chapter.

To better cover the training outlines in CP, this Study Guide was extensively revised and updated including new chapters and color photographs. New and expanded content includes lighting, imaging fundamentals, test object characteristics, VT techniques, remote VT equipment, as well as codes and standards.

Many new review questions follow every chapter and all questions follow the format of an ASNT exam.

Modern leak testing equipment and techniques are introduced. Leak flow and vacuum gas characteristics are presented in an organized and understandable manner facilitating the planning and performing of leak tests.