*SM1 CH 4*TEST EQUIPMENT AND MATERIALS MUKHTAR ALI, NCNDT

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*SM1 CH 4*EVALUATION OF THE MATERIALS FOR TESTINGFor appropriate selection of inspection procedure following information shall be considered:Materials and desired objectivesSurface ConditionShape of the productType of the productSize of the productAvailability of the equipmentSensitivity desired

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*SM1 CH 4*PROCESS SELECTION GUIDE

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*SM1 CH 4*PROCESS SELECTION GUIDE

TESTING PROBLEMPREFERRED PROCESSREMARKSArticles having medium rough surfacesWater washable or post emulsifiedChoice depends upon production and sensitivity requirementsSpot testing of local areas desiredSolvent removedBest choice for an efficient & sensitive method.Portable equipment necessarySolvent removedBest choice for an efficient & sensitive method.Water and electricity not availableSolvent removedMost appropriate choice.Anodized articles, cracks after anodizing, to be tested1. Solvent removed2. Post emulsified3. Water washableOrder of preference indicatedRepeated application of process is desiredSolvent removedFour to five times inspection, results reliable.

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*SM1 CH 4*Characteristic properties Each process of inspection by liquid penetrant method has typical characteristic associated with it. They have thus certain advantages and disadvantages depending on the state of the samples and conditions of inspection.

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*SM1 CH 4*SOLVENT REMOVABLE VISIBLE DYE-PENETRANT PROCESS

S/NoADVANTAGESDISADVANTAGES1.Has greater portability, requires no black light.Some materials are flammable.2.Can be used on suspected local areas of large parts, aids in rework or repair.Expensive in man-hours.3.Can be used on parts where contact with water is not permissible or water is not available.Indications are less visible than fluorescent indications.4.Can be used on anodized surfaces.Difficult to use on rough surfaces, especially on sand castings.5.Material should not be used in open tanks.

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*SM1 CH 4*WATER WASHABLE VISIBLE DYE PENETRANT PROCESS.

S/No.ADVANTAGESDISADVANTAGES1.Has greater portability, requires no black light source.Not a reliable process for finding scratches and wide shallow surface discontinuities.2.Susceptible to overwashing.3.Fast economical of time.Not reliable for second or third running of parts.4.Easily washed with water.5.Good on rough surfaces.6.Good on threads & keyways.7.Relatively inexpensive.

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*SM1 CH 4*WATER WASHABLE FLUORESCENT PENETRANT PROCESS.

S/No.ADVANTAGESDISADVANTAGES1.Has fluorescence for greater visibility.May be difficult to rerun parts.2.Easily washed with water.Anodizing may affect sensitivity.3.Good on rough surfaces such as large forgings and castings.Chromate finish may affect sensitivity.4.Good for quantities of small parts.Requires inspection in dark areas with black light.5.Good in keyways and threads.Not reliable for detecting scratches and similar shallow-surface discontinuities.6.High speed, economical of time, and good on wide range of defects.For black light electricity is required.

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*SM1 CH 4*POST-EMULSIFIABLE FLUORESCENT PENETRANT PROCESS.

S/No. ADVANTAGES DISADVANTAGES1.Has fluorescence for greater visibility.Application of emulsifier is a separate operation.2.Highest sensitivity to very fine defects.Requires inspection in dark areas with black light.3.Can show wide, shallow defects.Sometimes difficult to wash penetrant from:a. Threaded parts.b. Keyways.c. Blind holes.4.Easily washed with water after emulsification.Some materials are flammable.5.Difficult to use on rough surfaces.6.High production, especially with large parts.Requires a rinsing aid.7.Can be used on anodized surfaces.Emulsification time control is critical.8.Can be used on chromate surfaces.9.Parts can be rerun satisfactorily.

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*SM1 CH 4*SOLVENT REMOVABLE FLUORESCENT PENETRANT PROCESS.

S/No.ADVANTAGESDISADVANTAGES1.Fluorescence ensures visibility.Requires darkened area for inspection.2.Portability.Flammable materials.3.No water required.Removal of excess penetrant is time consuming.4.Good on anodized specimens.Materials cannot be used in open tanks.5.Good for spot checking.Difficult to use on rough surfaces such as cast magnesium.6.Specimen can be rerun.

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*SM1 CH 4*BEHAVIOUR PROPERTIES Evaluation of the Behaviour of penetrant materialsUse of aluminium comparator blocksBehaviour of used materialsBehaviour of fresh stockBehaviour of materials at low temperature Behaviour of materials at high temperature

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*SM1 CH 4*Preparation of cracks in aluminium alloy blocks Three-inch (75 mm) lengths are cut from a 3/8 x 2 inch (9.5 mm x 50.8 mm) bar of 2024 aluminium alloy Temperature 525CHeating time at least 4 minutesQuenching Temperature 50F or less.

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*SM1 CH 4*RENEWAL OF ALUMINIUM COMPARATOR BLOCKSVapour phase degrease Scrub with stiff brush, soap and water Soak in acetone at least overnight Rinse with water Heat slowly with a gas burner to 800 F (425 C) and quench in cold waterReheat moderately to drive off any water in cracks and allow to cool to room temperature

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*SM1 CH 4*USE OF CRACKED BLOCKSThe ASME code prescribes various uses of aluminium comparator blocks The block is used for qualifying a liquid penetrant technique at a temperature of less than 50 F (10 C) or above 125 F (52 C).The penetrant materials in use are applied to half of the block on one side of the slot, and control materials (fresh in stock) are applied to the other half in an identical fashion Processing of the two halves should be made simultaneously and then a direct visual comparison of the results should be made

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*SM1 CH 4*If the comparison of the observed crack pattern reveals no outstanding difference in two halves, it can be assumed that all the materials under use are suitable and their behaviour is normal

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*SM1 CH 4*LIMITATION OF ALUMINIUM ALLOY BLOCKS TESTSThe artificial cracks in aluminium alloy are non-uniform by nature and as such it is impossible to make two blocks identical It is important therefore to make a series of tests before reaching conclusions for critical results The difference may be quite subtle, hence the interpretation of the results should be done by personnel experienced at least in use of block themselves Other forms of test blocks such as made of ceramic stress-cracked anodized, aluminium and chrome plated nickel test panels are also used to check the overall performance of the penetrant materials

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*SM1 CH 4*CONTROL OF CONTAMINANTSMostly affective materials, Austenitic stainless steels, Titanium or Nickel base alloys Affective contaminants are Sulphur, Chlorine and FluorineContamination limits 1% by weight

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*SM1 CH 4*CLEANING EQUIPMENTUltrasonic CleaningUse of ultrasonic cleaning equipment is often combined with a solvent or detergent bath to improve cleaning efficiency and reduce cleaning time The method works well with water and detergent cleaning when contaminants to be removed are inorganic, and with solvents for organic type of contamination It is recommended to heat the test articles after the cleaning process to aid in the evaporation of cleaning fluids

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*SM1 CH 4*Degreasing SteamCleaning by vapour degreasing is particularly effective in the removal of oil, grease and similar organic contamination There are certain restrictions as to its use as a pre-cleaning or post-cleaning method Nickel alloys, certain stainless steels, and titanium have an affinity for specific elements e.g. chlorine or sulphur, and if exposed to them will become structurally damagedDegreasing must be limited to those materials that have been approved for this method of cleaning

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*SM1 CH 4*PULVERIZERS AND AEROSOLS Safe from outside contaminationEasy in Lab and field useStorage is not a problemGood and uniform performance

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*SM1 CH 4*INSTALLATIONS FOR PROCESSING BY IMMERSION The stationary equipment used in liquid penetrant testing ranges from simple to fully automatic systems and varies in size depending on the requirements of specific tests

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*SM1 CH 4*Visible dye and fluorescent penetrant process

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*SM1 CH 4*Dual sensitivity penetrant processes

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*SM1 CH 4*Small-size fluorescent post-emulsified penetrant and dry developer test equipment

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*SM1 CH 4*Medium-size fluorescent water-washable penetrant and wet developer test equipment

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*SM1 CH 4*Large-size fluorescent water-washable penetrant and wet developer test equipment

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*SM1 CH 4*Medium-size visible dye water-washable penetrant and dry developer test equipment

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*SM1 CH 4*Medium size visible dye post-emulsified penetrant and dry developer test equipment

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*SM1 CH 4*Stations Pre-cleaning station Penetrant station (tank) Drain station Emulsifier station Rinse station Developer station Dryer station Inspection station Post cleaning

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*SM1 CH 4*AUXILIARY EQUIPMENT Pumps To agitate different penetrant materialsSprayers and applicatorsUsed to spray penetrant, emulsifier and water rinsing Reduce inspection timeLights Visible and Ultraviolet lights are installed at inspection stationTimersTimers are used to control the time at different stages during process

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*SM1 CH 4*Thermostats and thermometersTo check the temperature of drying oven and penetrant materials Exhaust fansExhaust fans are used to remove fumes and dust HydrometersUsed to check the specific gravity of aqueous developers

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*SM1 CH 4*LIGHTING Measuring equipment and units Measurement of black light intensity requires the use of a special meter calibrated in watts per square metre or microwatt per square centimetre Meter is filtered so that it responds only to black light It is also filtered so as not to read short wave ultraviolet The meter scale runs up to 6000 watt/cm2, which is expandable up to 25000 watt/cm2 by attaching a multiplier screen supplied with the meter

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*SM1 CH 4*ULTRAVIOLET RADIATION LAMPS (BLACK LIGHT) Incandescent lampsMetallic or carbon arcsTubular `BL' fluorescent lampsTubular `BLB' fluorescent lampsEnclosed mercury vapor arc lamps

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*SM1 CH 4*Mercury vapour arc lamp sources of black light Mercury vapour lamps are gaseous discharge devices in which an electric arc takes place in a controlled atmosphere and emits light whose characteristics depend on the nature of the atmosphere MC represents a quartz or hard-glass cartridge in which the mercury vapour is confined E1 and E2 are the main electrodes that carry current to the arc stream which takes place along the length of the cartridge. E3 is an auxiliary starting electrode. R represents a current limiting resistor The entire assembly is sealed in an outer protective bulb, B, which may be either evacuated or filled with air or an inert gas, depending on the design of the bulb

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*SM1 CH 4*The lamp is fed from a current regulating ballast reactance or transformer This is required because the arc tube shows negative resistance characteristics and would quickly destroy itself if not throttled by an external device

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*SM1 CH 4*A black light mercury arc bulb requires a housing and fixture:-i)to support the filter.ii)to prevent leakage of unwanted visible light and to permit the operator to direct the beam onto the area to be inspected. Mercury vapour arc lamps up to an intensity of 400 watt are also commercially available, but are normally not portable

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*SM1 CH 4*Tubular fluorescent cold discharge black light sources

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*SM1 CH 4*These are standard fluorescent bulbs that come in sizes from 2 to 60 input watts and over These cold discharge tubular lamps contain low-pressure mercury vapour glow discharges Their primary radiation is hard ultraviolet of 253.7 nm (2537 A) wavelength This is used to excite a special cerium-activated calcium phosphate phosphor which is coated on the inside of the tube This phosphor, when activated by the ultraviolet, emits black light with a range of 320 to 440 nm wavelengths peaking at 360 nm

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*SM1 CH 4*Because a significant amount of visible light is emitted along-with the black light, these bulbs are often made of a purple-red filter glass similar to that used over the high-pressure arc lamps previously describedThis greatly reduces the black light emitted, but still leaves what is often an excessive amount of visible blue light, considering the relatively low intensity of the black light produced

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*SM1 CH 4*Advantages and limitations of fluorescent tubular black light sources AdvantagesInstant startingCool OperationLow costLimitationsLow IntensityCannot easily focusedNot suitable for critical inspection

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*SM1 CH 4*Incandescent filament black light sources This type of source of black light comes in 75 and 150 watt sizes It comes as standard incandescent bulb with a filter glass envelope These sources give a considerable portion of visible light along with black light, as such are thus even less usable and suitable than the fluorescent black light sources

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*SM1 CH 4*MEASUREMENT OF LIGHTVisible LightUltraviolet LightVisible light intensity at inspection site 50 foot candle or 500 LuxUltraviolet light intensity at inspection site 1000 W/cm2 Measurement of visible light intensity by visible light meterMeasurement of UV light intensity by UV light meter J221

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*SM1 CH 4*THANK YOU

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