Liquid Penetrant TestingCompiled for ASNT byDavid Quattlebaum, Jr.Quattlebaum Consultants

Level I

Liquid Penetrant Testing

Lesson 1Introduction to Liquid Penetrant Testing

History of Liquid Penetrant Testing1.Liquid penetrant testing is one of the oldest methods of nondestructive testing.The origin of liquid penetrant testing is generally attributed to the inspection of wheel axles in the railroad industry in the 1890s.

History of Liquid Penetrant Testing3.The oil-and-whiting test involves immersing test objects in oil and then wiping with rags dampened with kerosene. Powdered chalk was used to dust the surface to increase the visibility of any oil leaking back onto the test object surface.

Nondestructive Testing Methods1.To ensure product integrity and reliability. 2.To avoid test object failure, prevent accidents and save lives. To make user profits.Nondestructive testing methods are used for the following reasons:

Nondestructive Testing Methods4.To ensure customer satisfaction.5.To aid in better product design.6.To lower manufacturers costs.7.To maintain uniform quality levels. 8.To ensure operations readiness.

Reasons for Selecting Liquid Penetrant Testing1.Liquid penetrant testing quickly examines all accessible surfaces.2.Liquid penetrant testing detects very small surface discontinuities.Some advantages of liquid penetrant testing include the following:

Reasons for Selecting Liquid Penetrant Testing3.It can be used on a wide variety of materials including ferrous and nonferrous metals and alloys and fired ceramics.4.It uses relatively inexpensive and nonsophisticated equipment.5.Sensitivity magnifies size and location of discontinuities.

Reasons for Selecting Liquid Penetrant Testing6.Sensitivity can be adjusted by selection of penetrant, removal technique and type of developer.7.Technicians can visually detect indications.8.Liquid penetrant testing can be used for inservice checks to resolve production problems early.

Availability of Liquid Penetrant1.Type I: Fluorescent penetrant.2.Type II: Visible penetrant (color contrast).3.Type III: Dual mode (visible/ fluorescent).There are three basic classification types by dye.

Type I Fluorescent1.Level 1/2: Ultra low.2.Level 1: Low.3.Level 2: Medium.4.Level 3: High.5.Level 4: Ultra high.Type 1 fluorescent is further classified by five sensitivity levels as follows:

Type II FluorescentThere is no sensitivity level classification for Type II penetrant systems.

Method of Removal1.Method A: Water washable.2.Method B: Lipophilic postemulsifiable.3.Method C: Solvent removable.4.Method D: Hydrophilic postemulsifiable.Type I and II are further classified by method of removal of excess penetrant.

Developer FormsDevelopers are classified as forms.1.Form A: Dry powder.2.Form B: Water soluble.3.Form C: Water suspendible.4.Form D: Nonaqueous Type I (fluorescent).

Developer Forms5.Form E: Nonaqueous Type II (visible dye).6.Form F: Special applications.

Solvent ClassesSolvents are divided into classes.1.Class 1: Halogenated.2.Class 2: Nonhalogenated.3.Class 3: Special applications.

Qualification and Certification Requirements1.ASNT Recommended Practice No. SNT-TC-1A.2.ANSI/ASNT CP-189: Standard for Qualification and Certification of Nondestructive Personnel.The following documents outline personnel qualification and certification requirements:

Qualification and Certification Requirements3.ACCP: ASNT Central Certification Program.4.NAS 410, National Aerospace Standard Certification and Qualification of Nondestructive Testing Personnel.

Training and Qualification ProcessA person who is in the process of training and qualification is considered a trainee.

Three Basic Levels of Qualification1.Level I.2.Level II.3.Level III.

Qualification Requirements1.Organized training (required class hours).2.Required testing (general, specific, practical).3.Education (depends on written practice).

Qualification Requirements4.Experience (documented hours).5.Physical attributes to perform examinations (vision acuity and color contrast test performed annually).

CertificationCertification is a written testimony that an individual has met all the qualifications of a companys written practice.

Safety Precautions: Fire1.Materials are usually combustible.2.Minimum flash point on open tanks is usually 93 C (200 F).3.Smoking and open flames should be avoided.4.Storage should be away from heat and open flames.

Safety Precautions: Fire5. Always review the material safety data sheets (MSDS) for precautions.

Skin Irritation1.Drying action can occur on skin from oil bases.2.Avoid splashing of materials.3.Wear protective gloves, aprons and glasses.4.Wash hands immediately when in contact with penetrant materials.5.Use protective hand creams.

Air Pollution1.Dust and vapors are nontoxic.2.Inhalation of excessive amounts can be a health hazard.3.Exhaust fans should be installed for the use of dry developers.4.Fans should be used in test areas to remove vapors.5.Always follow recommendations for respirator or mask use.

Ultraviolet Radiation1.365 nm ultraviolet radiation causes fluorescence of penetrant material.2.Higher frequencies are harmful to humans.3.Ultraviolet lamp filters are used to prevent these harmful rays from harming humans.

Ultraviolet Radiation4.Filters should be inspected for cracks and replaced as necessary.5.Protective lenses or goggles should be used.

Lesson 2Liquid Penetrant Processing

Procedures and Techniques1.Procedures can be broad and cover several specific techniques.2.Each procedure and technique should be approved and signed by a certified Level III.

Precleaning of Test Objects1.Solvent.2.Detergents.3.Vapor degreasing.4.Steam cleaning.Cleaning processes include the following:

Precleaning of Test Objects5.Ultrasonics.6.Chemical.7.Paint strippers.

Precleaning of Test Objects1.Local environmental requirements.2.Health and safety requirements.3.Cause no harm to the test object.All cleaning methods must meet the following requirements:

Precleaning of Test Objects4.Substrate should be wiped clean with an approved solvent cleaner.5.Solvent cleaner should be allowed to dry completely before application of penetrant.

Preparation of Test Objects1.The surface properties of the test object determine surface preparation.2.High nickel alloys, titaniums and stainless steels require the use of low sulfur and chloride products.

Preparation of Test Objects3.Surfaces need to be free of foreign materials which block open discontinuities.4.Cleaning operations such as power wire brushing, grit blasting, shot peening and other metal smearing operations should be avoided.

Precleaning and Postcleaning1.Liquid penetrant test will be ineffective if substrate is not physically and chemically cleaned and dried.2.Liquid penetrant residue may have a harmful effect on test object if not properly removed before placing it in service.

Precleaning and Postcleaning3.The compatibility of cleaning agents and penetrant materials should be verified to ensure an acceptable penetrant test.

Solvent Cleaning1.The application of solvent cleaning may be immersion, sprayed, brushed or wiped.2.Solvent cleaning is commonly used for spot inspections.

Solvent Cleaning3.Solvent cleaners must evaporate readily and completely from the substrate.4.Solvent cleaners should be used to remove organic contaminants only.

Solvent CleaningTest object being cleaned with a solvent- damped, lint-free cloth prior to application of penetrant.

Detergent Cleaning1.Detergents wet the substrate.2.Penetrates various soils.3.Emulsification.4.Saponification (change to soap).5.Substrate is rinsed and dried.Cleaning is accomplished by the use of immersion tanks and or detergent solutions. Cleaning is accomplished as follows:

Detergent Cleaning Equipment1.Suitable rinsing stations.2.Suitable drying stations.3.Thorough rinsing and drying after detergent cleaning will leave the substrate physically and chemically clean for liquid penetrant testing.

Vapor Degreasing1.Removal of oils.Removal of greases.Removal of other similar organic contaminations.Vapor degreasing does not require a rinse or drying (oven) step.Vapor degreasing is effective for the following procedures:

Vapor Degreasing5.Vapor degreasing can be hazardous to the environment.6.Vapor degreasing safety is a large concern due to health hazards.7.Vapor degreasing is limited to cleaning of substrates that have been approved for this type of cleaning method.

Steam CleaningPrecleaning with steam and alkaline detergents provide ideal cleaning.1. Alkaline detergent emulsifies, softens or dissolves organic contamination.

Steam Cleaning2.Steam provides mechanical action for removal of detergents/contaminations from the surface of the substrate.3.Steam cleaning is suitable for cleaning large, unwieldy components which are not easily submerged.

Ultrasonic Cleaning1.Ultrasonic cleaning is often combined with detergent or alkaline cleaning.2.Combined ultrasonic cleaning improves efficiency and reduces cleaning time.

Ultrasonic Cleaning3.Ultrasonic cleaning is useful for cleaning large quantities of small test objects.4.Ultrasonic agitation requires special approval on some substrates.

Rust and Surface Scale RemovalApproved commercial rust and surface scale removers include the following:1.Acid rust removers.2.Alkaline rust removers.These require special equipment, and specific procedures should be followed.

Paint RemovalPaint removal methods include the following:1.Dissolving hot tank paint strippers.2.Bond release paint strippers.3.Solvent paint strippers.These require special equipment, and specific procedures should be followed.

Etching1. Acid or alkaline solutions are used to remove smeared metal from operations, including the following:a. Power wire brushing.b. Sand blasting.

Etching 2.Solutions open up grinding burrs and remove smeared metals. 3.Etching and neutralization processes use either tanks/immersion or manual equipment.

Precleaning Processes to be AvoidedThe following methods should not be used before liquid penetrant tests:1. Blasting (shot, sand, grit, pressure, etc.).2. Liquid honing.

Precleaning Processes to be Avoided3.Emery cloth.4.Power wire brushes.These processes tend to close discontinuities by smearing metal, peening or cold working the surface.

Drying Test ObjectsTest objects and potential discontinuities should be completely dry of cleaner before the application of penetrant.1.Any remaining cleaner may prevent capillary action of the penetrant into discontinuities.

Drying Test Objects2.Some procedures require application of isopropyl alcohol or acetone to promote drying.3.Drying ovens are sometimes required.

Dwell Time1.Penetrant dwell time is a period of time to allow penetrant to enter and fill any discontinuities open to the surface through capillary action.

Dwell Time2.Liquid penetrant is drawn out of discontinuity entrapments to the test object surface during the so-called development time or developer dwell time. 3.Liquid penetrant may spread into the developer coating to form enhanced indications. This is sometimes referred to as reverse capillary action.

Application of PenetrantPenetrant applications include the following:1.Spraying.2.Brushing.3.Pouring.4.Dipping.

Application of PenetrantTest surfaces should remain wetted the entire penetrant dwell time. Ultraviolet radiation sources may assist when using fluorescents.

Application of Penetrant: Color ContrastApplication of penetrant also includes the HAZ; technicians should review procedures to ensure complete coverage for area of interest.

Application of Penetrant: FluorescentTest object held in suspension while required dwell time elapses for fluorescent process.

Adequate Illumination1.Fluorescent rinse station requires about 100 lux (10 ftc) of ambient (white) light and less than 100 W/cm2 of near ultraviolet radiation (UV-A).

Adequate Illumination2.Fluorescent evaluation station should be about 1000 W/cm2 of near ultraviolet radiation (UV-A) as measured at the test surface, and the ambient (white) light should not be greater than 20 lux (2 ftc).

Adequate Illumination3. Visible dye penetrant (color contrast) usually requires 1000 lux (100 ftc) at the test surface.These levels should always be verified against the governing procedure, standard or specification.

Adequate Illumination: Ultraviolet Radiation MeterTypical ultraviolet radiation meter used for fluorescent processes.

Adequate Illumination:Ultraviolet Radiation MeterTypical test fixture for verification of adequate illumination at a fixed distance from the meter.

Adequate Illumination:Ambient Light MetersIllumination meters for the measurement of ambient (white) light in foot-candles or lux.

Penetrant: Water Rinse (Methods A, B and D)After the required dwell/ emulsification time, the examination area should be:1.Water rinsed. Course droplets are preferred, as the mechanical action is dependent on the size of drops and velocity at impact.

Penetrant: Water Rinse (Methods A, B and D)2.Applied at an oblique angle (45 to 75 is most effective angle).3.Normal distances of 15 to 61 cm (6 to 24 in.) are acceptable and provide a uniform rate of removal.

Penetrant: Water Rinse (Methods A, B and D)4.Temperature range for rinse water is 10 to 38 C (50 to 100 F).5.Water pressure of about 69 to 241 kPa (10 to 35 psi) is generally used. The pressure should not exceed 276 kPa (40 psi).

Typical Water Rinse StationTest objects being rinsed while viewed under a fluorescent light to ensure adequate cleaning.

Solvent RemovableAfter the required dwell time, the following functions should be performed:1.Wipe test area with a lint-free, absorbent towel that has a color contrast with the penetrant.2.Use a clean section with each swipe.

Solvent Removable3.After removal of the bulk of penetrant, lightly dampen a clean cloth. Do not soak or saturate the cloth with cleaner. Continue to swipe area until no evidence of penetrant is observed.

Solvent Removable4.Make a final swipe with a clean dry cloth and verify that there is no evidence of penetrant on the cloth. Allow the cleaner to evaporate before the application of developer.

Developer Application and DryingThe basic types of developer are as follows: 1.Form A: Dry powder (fine powder form).2.Form B: Water soluble (liquid dip tanks).

Developer Application and Drying3.Form C: Water suspendible (liquid dip tanks).4.Form D: Nonaqueous Type I (aerosol spray cans).5.Form D: Nonaqueous Type II (aerosol spray cans).6.Specific application developers.

Dry Powder Developer Form ADry powder developers are applied to dry test object surfaces by the following methods:1.Air suspension.2.Electrostatic spraying (common in automated systems).

Dry Powder Developer Form A3.Test object immersion.4.The powder is light and fluffy and clings to the test object surfaces in a fine film.5.Dry powder is most useful on rough surfaces and automated processing using fluorescent penetrants.

Water Soluble Developer Form BDevelopers consist of a powder dissolved in water and applied by the following means:1.Dipping a test object in the solution.2.Flowing the solution over a test object.

Water Soluble Developer Form B3.Spraying the solution onto the test object. This type of aqueous developer forms a translucent film.4.Water soluble developer can be used for fluorescent dyes.5.Not recommended for use with visible dye.

Water Soluble Developer Form B6.Not recommended for use with water washable. Water in the developer may remove water washable penetrant from discontinuities.7.Can save time during processing, since drying is included in the developer dwell time.

Water Soluble Developer Form B8.Supplied as a dry concentrate that must be mixed and maintained at the proper ratio of developer to water.9.Developer should be checked at regular intervals for penetrant contamination and water evaporation per approved specifications.

Water Suspendible Developer Form C1.Supplied as a dry concentrate that must be mixed and maintained at the proper ratio of developer to water.2.Suspended aqueous developer does not dissolve in water so it must be thoroughly agitated just before application to suspend the particles in water.

Water Suspendible Developer Form C3.Development of indications does not begin until the moisture is completely evaporated from the developer.4.Thickness of the coating and its white color work well with visible dyes.

Water Suspendible Developer Form C5.Test objects should be checked to ensure a uniform coating of developer has been applied.6.Developer should be checked at regular intervals for penetrant contamination and water evaporation per approved specifications with a hydrometer.

Water Suspendible Developer Form C7.Removal of dried suspendible developers may be more difficult because they are not soluble in water.8.All aqueous developers necessarily contain biocides, corrosion inhibitors and wetting agents.

Nonaqueous (Aerosol Can) Type I and II1.Nonaqueous (solvent suspendible) developers are supplied in the ready-to-use condition, frequently in aerosol cans.

Nonaqueous (Aerosol Can) Type I and II2.Nonaqueous developer is the most sensitive form of developer because the solvent action contributes to the absorption and adsorption mechanisms of the developer by entering the discontinuity and dissolving into the liquid penetrant.

Nonaqueous (Aerosol Can) Type I and IIa.Adsorption is the surrounding of the developer particles by adhesion, which coats the surface of the particles.b.Absorption is the assimilation of penetrant into the bulk of the particles.

Nonaqueous (Aerosol Can) Type I and IIPrior to spraying of developer, the following procedures should be followed: 1. Aerosol can requires agitation before spraying.2. The test object must be thoroughly dry.

Nonaqueous (Aerosol Can) Type I and II3.Several thin, uniform coats are preferred over one heavy coat.4.A check spray should be performed before spraying the test surface to prevent spattering of the developer.

Nonaqueous (Aerosol Can) Type I & II Visible fluorescent portable kit.

Development/Dwell Time1.The development of indications does not begin until the moisture is completely evaporated from the developer.2.The test object must be monitored very closely during the developer dwell time to properly evaluate the indications as they form.

Development/Dwell Time3.Typically, the developer dwell time is a minimum of 10 min. Always reference the specifications.4.The point at which the developer dwell time begins depends on the type of developer being used.

Development/Dwell Time5.Wet developer dwell time begins as soon as the developer is dry.6.Dry and nonaqueous developer dwell times begin at application.

Interpretation and Evaluation1.Interpretation: The determination of whether indications are relevant or nonrelevant.2.Evaluation: A review, following interpretation of the indications noted, to determine whether they meet specified acceptance criteria.

Types of IndicationsIndications form on the surface of test objects during examinations because of discontinuities located on the surfaces. They may be classified as the following:1.False indications.2.Nonrelevant indications.

Types of Indications3.Relevant indications.a.Linear indications are those which contain a major dimension at least three times the minor dimension.b.Round indications are those whose major dimension is less than three times the minor dimension.

Types of IndicationsThis is a general rule of thumb. Refer to the specification or procedure.

Discontinuities1.A discontinuity is an interruption in the normal structure of the test object. It may not be a defect. 2.If, during the evaluation phase, it is determined that the discontinuity interferes with the serviceability of the test object or it does not meet the acceptance criteria, the discontinuity is then classified as a defect.

False Indications1.A nondestructive testing indication that is interpreted to be caused by a discontinuity at a location where no discontinuity exists.2.False indications are nonrelevant.3.In some reference documents, false indications and nonrelevant indications are considered to be the same thing.

False Indications4. False indications are caused by the following reasons:a.Lack of cleanliness by poor processing conditions.b.Lack of cleanliness in the testing booth or other aspects of the penetrant process.

False Indicationsc. Penetrant on the hands of technicians.d.Contamination of wet or dry developer.e. Penetrant from other test objects.f. Penetrant on examination table.g.Fluorescent specks or particles.

False Indications5. Cleaning and reprocessing a test object is required when false indications are noted.6.A typical false indication is a piece of lint on a part that resembles a crack during ultraviolet radiation testing.

False Indications7. The most serious problem with false indications is determining whether the indication is masking a relevant indication.

Typical False IndicationMarks from handling toolFingerprints left by technicianPatch from contact with another test objectLint and dirt

Nonrelevant IndicationsNonrelevant indications are caused by surface irregularities or test object configuration and are not detrimental to the serviceability of the test object. They may appear on test objects at the following locations:

Nonrelevant Indications1.Press fitted joints.2.Riveted connections.3.Spot welds.4.Substrates with rough surfaces.

Relevant Indications1.Relevant indications are those that are caused by discontinuities on the surface of a test object. 2.All relevant indications are discontinuities, but not all discontinuities are defects.

Relevant Indications 3. Relevant indications are classified as:a. Continuous line indications.b. Intermittent line indications.c. Round or dot indications.Within these groups there are large, small, weak and diffused indications.

Continuous Line Indications1. Continuous line indications are discontinuities. a.Cracks.b.Seams.c.Cold shuts.d.Forging laps.

Continuous Line Indications2.Continuous line indications can be jagged, like most cracks, or very straight, like a seam indication. 3.The degree of bleed out depends on factors such as the width and depth of the indication and the penetrant and developer dwell times.

Intermittent Line Indications1.Intermittent line indications are caused by the same discontinuities as continuous line indications. 2.The difference is that these indications have been affected by previous processing steps, inservice use or are partially subsurface. Therefore, they are not continuous lines.

Round or Dot Indications1.Round or dot indications are caused by porosity, pin holes, a porous surface or a coarse grain structure.2.Round indications also can be caused by crater cracks because they tend to trap large amounts of penetrant.

Round or Dot Indications3.A round indication becomes a linear indication when the length of the indication is more than three times the width.

PostcleaningPostcleaning can involve the following:1.Vapor degreasing.2.Solvent soak.3.Ultrasonic cleaning.Other postcleaning operations may be required by specifications and procedures.

Lesson 3Liquid Penetrant Testing Methods

Introduction1.Test methods are developed for the detection of discontinuities that are open to the surface, such as cracks, seams, laps, cold shuts, laminations, through leakage or lack of fusion.

Introduction2.Application of the methods are applicable to in-process and final manufacturing of components, inservice tests and maintenance activities.

Introduction3.The different methods can be effectively used for the examination of nonporous, metallic materials (both ferrous and nonferrous) and of nonmetallic materials such as glazed or fully densified ceramics, certain nonporous plastics and glass.

Introduction4.Once a method has been selected and discontinuities are detected by evidence of indications from the examination, they must be interpreted or classified and then evaluated.

Introduction5.Evaluation requires codes, specifications or procedures to define the type, size, location and direction of indications considered acceptable or unacceptable.

Introduction6.Classification/method of penetrant testing requires consideration of the following:a.Type of dye penetrant.b.Method of removal.c.Penetrant sensitivities.d.Form of developer.e.Classes of solvent removers.

Method Characteristics: Type I Fluorescent versus Type II VisibleThe following factors should be considered when choosing between Type I fluorescent and Type II visible: 1.Availability of dark area and power source.2.Level of sensitivity required.3.Type of indication sought.

Type I Fluorescent versus Type II Visible4.Size and location of surface to be examined.5.Availability of cleaning processes.6.Type I has five levels of sensitivity: 1/2 ,1, 2, 3, and 4; 4 being most sensitive.7.Type II has no sensitivity level rating.

Type I Fluorescent versus Type II Visible8.Type I is usually required when a specific level of sensitivity is desired.9. Type I fluorescent should never follow Type II visible. The visible dye may quench the fluorescent dye properties, and the visible dye may fill the discontinuity, eliminating a fluorescent indication.

Solvent or Water Removable1.Portable solvent or manual water removable kits allow field testing.2.Materials are supplied in aerosol spray cans.3.One technician can carry equipment.

Solvent or Water Removable4.Available in Type I and II materials.5.Aerosol cans do not require daily calibration or contamination checks.

Inline Penetrant Systems1.Inline systems normally consist of bulk penetrant materials in tanks.2.Type I fluorescent is usually used.3.Water rinse or emulsification is used.

Inline Penetrant Systems4.Type I, Method A is most common. Methods B or D are also used for inline testing.5.Normally used for large volumes of manufactured test objects. The type of indication sought will dictate method and sensitivity.

Lipophilic Emulsification1.Method B is lipophilic (oil loving).2.Application is done by dipping. Agitation of the test object is prohibited.3.Brush-on or spray-on is not permitted.

Lipophilic Emulsification4.The mechanism of lipophilic is by diffusion.5.Emulsification time is critical and must be carefully controlled for reproducible results.

Hydrophilic Emulsification1.Method D is hydrophilic (water loving).2.Works through detergent or surfactant reaction.3.Prewashing removes 60 to 80% of the surface layer of penetrant.4.Following the prerinse, hydrophilic emulsifier or remover is applied by immersion or spray.

Hydrophilic Emulsification5.Concentration by immersion is usually 5 to 30% by volume.6.Slight agitation is necessary to remove the colloidal suspension of penetrant and emulsifier from the surface and to expose fresh penetrant.

Hydrophilic Emulsification7.Agitation is done by gently moving the submerged test object in the remover, or by an air manifold in the bottom of the tank.8.Only enough air to cause slight bubbling is required.

Hydrophilic Emulsification9.The mechanism of spray hydrophilic emulsifier is a combination of chemical and mechanical action.10.Immediately following the remover, a fresh water rinse of the entire test object is required. This stops the action of any remaining remover on the test object.

Hydrophilic Emulsification11.Concentration of spray removers is usually 0.5 to 1% by volume; up to 5% may be used.

Lesson 4Liquid Penetrant Testing Equipment

Liquid Penetrant Testing Units1. Liquid penetrant testing units can be arranged so test objects are moved in the following ways:a. Manually.b. Mechanically assisted.c. Semiautomatic.d. Fully automatic.

Liquid Penetrant Testing Units2. The choice depends on budget, timing and the long-term system performance.3. The size of testing unit is largely dependent on size and type of test object. The layout of the system may take on various designs depending on the facilities available, production rate desired and ease of handling test objects.

Liquid Penetrant StationsTesting stations requirements are dependent on the following factors:1. Type of penetrant used.2. Processing requirements.3. Size of test objects.4. Quantity/production rate desired.

Auxiliary Equipment 1.Auxiliary equipment located at the penetrant test station (other than cleaning stations) is required to perform penetrant testing. 2.Auxiliary equipment may be built in at one or more test stations.

Auxiliary Equipment Penetrant StationEmulsifier StationDrain StationDryer StationUltraviolet lampUltraviolet lampTest StationDeveloper StationRinse StationControl Panel

Test StationRest StationDryerDeveloper StationUltraviolet lampRinse StationHandheld sprayerDrain StationPenetrant Station

Test StationUltraviolet LampsWhite LightDryerDeveloper StationRinse StationDrain StationPenetrant StationHand hose (pump fed)Hand hose (pump fed)Hand hose waterUltraviolet Lamp

Modular UnitsStations are supplied in modular units to allow many configurations, such as straight line, L- or U-shaped arrangements.

Liquid Penetrant Tank with Cover

Drain and Rest Station

Wash Station

Drying Oven

Dry Developer Station

Testing Station

Multiple Component Inline Liquid Penetrant System

Multiple Component Inline Liquid Penetrant System

Self-Contained, Water Washable Fluorescent Unit

Testing Station PumpsVarious pumps are installed at the penetrant, emulsifier, rinse and developer stations as applicable. They are required for the following procedures:1.Agitation of the solutions.2.Pump drain-off material into proper tanks for reuse or filtration for disposal.

Testing Station Pumps3.Used to power handheld sprayer and applicators.4.Require routine maintenance to ensure reliability.

Sprayers and Applicators1.Sprayers and applicators are frequently used at the penetrant, emulsifier, rinse and developer stations.2.They decrease test time by permitting rapid and even application of penetrant materials.

Sprayers and Applicators3.Conventional and electrostatic sprayers are used for penetrants, dry and suspended developers.

Electrostatic Spray Systems1. Application with an electrostatic spray system does the following: a. Minimizes consumption of liquid penetrant materials and reduces pooling of penetrant.b. Helps ensure complete even coverage of complete surfaces.

Electrostatic Spray Systems2.Requires penetrant material have an electrostatic charge.3.Suitable for parts too large for immersion.4.Spray systems virtually eliminate contamination of reservoirs of penetrant materials.

Electrostatic Spray Systems5. For application with electrostatic spray, the technician applies fluorescent penetrant with a handheld spray gun that makes atomized particles attract to the test object.

Automatic Electrostatic Spray Two reciprocating electrostatic spray guns in a conveyorized installation used to apply penetrant.

Lamps for Penetrant Stations1.Ambient and ultraviolet radiation lamps are installed as required to ensure adequate illumination at all stations.2.When using fluorescent materials, lamps are installed at the rinse and inspection booths.

Lamps for Penetrant Stations3.Illumination should be checked with calibrated instruments as required by procedures and specifications at the testing area.

Illumination InstrumentsUltraviolet Light MeterWhite Light Meters

Liquid Penetrant Station TimersTimers are used at penetrant stations to monitor the following:1.Penetrant dwell times.2.Emulsifier dwell times.3.Developer dwell time.4.Drying cycles.

Thermostats and ThermometersThermostats and thermometers are used to monitor and control temperatures of the following:1.Penetrant materials.2.Drying ovens.3.Test objects.4.Atmosphere.

Exhaust Fans for Penetrant Stations1.Exhaust fans are used when testing is performed in confined spaces.2.Fans remove fumes and dust particulate from the test area.3.Prolonged breathing of penetrant vapors, emulsifier vapors or solvent remover vapors may cause headaches, nausea, tightness or pain in the chest.

RefractometerUsed to measure the concentration of hydrophilic emulsifier in water.

HydrometerA hydrometer is used to measure specific gravity of water-based wet developers.

HydrometerA hydrometer floats vertically in developer, and specific gravity is read from scale at fluid level.BallastBodyScaleStem

Portable Penetrant Equipment 1.For use when testing is required at a location remote from stationary equipment.2.For use when small portions of a large object require testing.

Portable Penetrant Equipment 3.Available in fluorescent and visible dye kits which are compact and lightweight.4.May be applied by spray from aerosol cans or applied with a brush.

Visible Dye Penetrant KitThe contents of a visible dye penetrant kit consist of the following:1.Solvent cleaner.2.Penetrant remover.3.Visible penetrant.4.Application brushes or pads.5.Nonaqueous wet developer.6.Lint-free wiping cloths.

Visible Dye Penetrant KitTypical portable visible dye kit.

Fluorescent Penetrant KitThe fluorescent penetrant kit combines portability with high visibility and normally contains: 1. Portable ultraviolet lamp.2. Solvent cleaner.3. Penetrant remover.4. Fluorescent penetrant.

Fluorescent Penetrant Kit5.Application brushes or pads.6.Developer, either nonaqueous wet or dry.7.Lint-free wiping towels.8.Hood to provide darkened area for viewing of indications.

Portable Fluorescent Penetrant Kit

Ultraviolet Radiation Illumination1.Most common, handheld ultraviolet mercury vapor lamps will produce light in the wavelength range of 320 to 440 nm.2.Fluorescent penetrant dyes are usually in the range of 475 to 575 nm, which is in the visible spectrum of green to yellow.

Ultraviolet Radiation Illumination3.Equipment checks should be performed as defined in the specification or procedure being used for the testing.

Lamp Filters1.A filter that transmits near-ultraviolet radiation while absorbing other wavelengths.2.The most common UV-A light consists of a mercury bulb housed with a filter that is powered by a constant voltage transformer producing wavelengths in the range of 320 to 400 nm.

Lamp Filters3. The filter used in front of the high-pressure mercury vapor light has a peak transmission at a wavelength of 365 nm.4. A warm-up time is required for the mercury bulb to reach full intensity and the light should remain on to avoid cycling, which reduces the life of the bulb.

Lamp Filters5.Regular cleaning of the bulb and filter is required to remove dust, oil, dirt and fluorescent contamination that can reduce the ultraviolet radiation intensity.

Ultraviolet Radiation SourcesCommon sources of near-ultraviolet radiation include:1.Enclosed mercury vapor arc lamps.2.Metal halide or halogen lamps. 3.Integrally filtered tubular fluorescent lamps.

Ultraviolet Radiation Sources4.Tubular fluorescent lamps.5.Metallic or carbon arcs.6.Incandescent lamps.

Ultraviolet Radiation Sources

Tubular Fluorescent Cold Discharge Sources1.Tubular fluorescent lamps are quite low in output and only usable in a very few special applications.Available in sizes from 2 W to more than 60 W input. Contain low pressure mercury vapor glow discharges.Made of a purple-red filter glass.

Subdued White Light Inspection1.Improved penetrant materials have made it possible to test in less than total darkness.2.Medium to large indications can be detected under fairly high ambient (white) light.

Subdued White Light Inspection3.Fluorescent testing is possible outdoors.4.Requirements for ambient (white) light must be met using black cloth or other shielding.

Light Meters1.White light sensors measure in foot-candles or lux.2.Ultraviolet radiation sensors measure in microwatts per centimeter squared (W/cm2).

Materials for Liquid Penetrant TestingMaterials used in liquid penetrant testing include:1.Penetrants.2.Emulsifiers.3.Removers.4.Cleaners.5.Developers.

Precleaning and Postcleaning1.Materials must be compatible with the penetrant.2.Manufacturers will recommend an approved cleaner for their products.

Water Washable PenetrantsHighly penetrating, oily liquids containing a built in emulsifying agent that renders the oily media washable with water.The simplest to use are visible penetrants or color contrast penetrants, because no fluorescent lighting is required.

Water Washable Penetrants3.Greater visibility is obtained if fluorescent penetrants are used and viewed under ultraviolet radiation.

Postemulsification PenetrantsPostemulsification penetrants are available as either visible or fluorescent penetrants.These penetrants have the advantage of eliminating some of the danger of over rinsing.

Emulsifiers1.When applied to a post-emulsification penetrant, emulsifiers combine with the penetrant to make the resultant mixture water washable.2.The emulsifier, usually dyed orange to contrast with the penetrant, may be either lipophilic (oil base) or hydrophilic (detergent water base).

EmulsifiersTypical Emulsifier Dip Tank

Lipophilic Emulsifiers1.They begin emulsifying on contact with the penetrant.2.Emulsifiers can never be applied by brushing.The mixture of penetrant and emulsifier can be removed with a standard water rinse.Renders the penetrant water washable.

Hydrophilic Emulsifiers1.Function by displacing the excess penetrant film on the surface through detergent action.2.Force of water spray or air/mechanical agitation in an open dip tank provides the scrubbing action while the detergent displaces the film of penetrant.

Hydrophilic EmulsifiersEmulsification time will vary, depending on its concentration, which can be monitored using a suitable refractometer.Hydrophilic emulsifiers (removers) can also be used as contact emulsifiers.

Hydrophilic Emulsifiers5.These penetrants have the advantage of eliminating some of the danger of over rinsing.Require agitation to allow fresh emulsifier to contact the surface penetrant.Render the penetrant water washable.

Solvent RemoversUsed to remove excess penetrant from test surfaces.Must be approved by the penetrant manufacturer and penetrant procedure or specification.

DevelopersDevelopment of penetrant indications is the process of bringing the penetrant out of discontinuities open to the surface through blotting action of the applied developer. This increases the visibility of the indications under suitable visible white light or fluorescent light.

Dry DeveloperFluffy powder that is applied to dry test surfaces.Most adaptable to rough surfaces and automatic processing.Easiest to remove.

Dry Developer4.Care should be taken not to contaminate developer with fluorescent penetrant.5.Penetrant contamination may cause specks that appear as indications.

Nonaqueous Wet DeveloperSuspension of developer particles in a rapid drying solvent.Used with solvent removable processing.Applied only to dry surfaces.This type of developer is intended for application by spray only.

Water-Based DevelopersApplied before drying the test object.Water suspendible developer: Particles are held in suspension in water and require continuous agitation to keep the particles in suspension.

Water-Based Developers3.Water soluble developer: Powder is dissolved in water, forming a solution; once mixed they remain mixed.

Special Purpose PenetrantsThere are low sulfur and low chlorine materials for testing nickel alloys, certain stainless steels and titanium.High and low temperature penetrants are available for special applications.

Special Purpose PenetrantsLow-energy emulsifiers and inhibited solvent removers are available to slow emulsification and the removal of excess penetrant.4.Wax and plastic film developers absorb and fix penetrant indications to provide record of the test.

Precautions1. Ensure that the test object is not damaged or overheated during the test.2. The technician must ensure that solvent wont harm the test object.3. Review the MSDS frequently.