MODULE 2 NON-DESTRUCTIVE TESTINGThree Rs of maintenance 1. Routine 2. Renewal 3. Repair Maintenance Renewal Routine Repair Inspection Adjustment LubricationInspection means of predicting a need for future work for example (visualor condition monitoring equipment to check all wearing parts)Equipment wear records: in the predictive maintenance program the abovemethods utilizes to predict failures. The wear of the equipment plotted againsttime. As the wear progressing a graph is made. This prevents a breakdown andallows the maintenance staff the flexibility to schedule the repair withoutinterrupting production.
Non-destructive testingTo know the amount of deterioration in a piece of equipment or the condition offinished product without destroying or dismantling the product.Types of Non-destructive testing 1. Liquid penetrate 2. Magnetic particles 3. Ultra-sound 4. Visual inspection 5. Vibration analysis 6. X-ray 7. Thermography Visual inspectionBasic principle: Illuminate the test specimen with light Examine the specimen with the eyeUsed to: To magnify defects which can not be detected by the unaided eye To assist in the inspection of defects To permit visual check of areas not accessible to unaided eyeAdvantage Most widely used of all nondestructive tests Simple, easy to apply, quickly carried out and usually low in cost
Liquid penetrate (LP)Principle:The surface part under evaluation is coated with a penetrant in which a visible ordye is dissolved the penetrant is pulled into surface defects by capillary actionAfter a waiting period to insure the dye has penetrated into the cracks, theexcess penetrant is cleand from the surface of the sample. A white powder calleddeveloper is the sparyed or dusted over the part. The developer lifts thepenterant out of the defect.Example of applications: Detection of cracking and porosity in welded joints Detection of surface defects in casting Detection of fatigue cracking in stressed materialsEquipment: Portable systems in spray
Magnetic particle (MP)Principle:The sample is magnetized are dusted over the sample. A surface defect will forma magnetic anomaly attracting and holding magnetic particles and giving a visualindication of the defectExample of applications: Fatigue cracks in steel dies Shrinkage in machined castings Stringers or cold shunts in forgings after finish machiningEquipment:Fixed piece of equipment or portable system for use in the field
Ultra-sound (UT)Principle:Ultrasonic test (UT) uses high frequency sound energy to conduct examinationsand measurements.Equipment: Pulse/receiver produce high voltage electrical pulse Transducer generates high frequency ultrasonic energy the sound energy is introduced and propagates through the materials in the form of waves Display devicesExample of applications: Detection of cracks, voids and inclusions Detection of density variations on the order 0.25% or less Samples which require resolution as small as 2 microns in three dimensions Samples can be inspected for both surface characteristics as well as bulk properties Examining bolts or rivets in aircraft wings to find crakes and defects Inspection of carbon composites for aging or impact damage Weld penetration inspection Weapons stockpile surveillance
Vibration analysisVibration analysis it analyzes the cause of vibration instead of just determiningthe level of vibrationVibration has two main characteristics frequency and amplitudeFrequency : is the number of times that a part oscillates through a cycle in onesecond expressed in hertz or cycles per minute (CPM) is usually reserved forequipment of a slower speedAmplitude: is the measure of the severity of the vibration can be measured inthree ways Displacement Velocity AccelerationDisplacement is the actual amount of movement that takes place its measuredin peak-to-peak displacement is usually used to measure low or constant speedmachineryVelocity: is the speed at which the displacement takes place is used on allfrequencies of rotating machineryAcceleration: is the time rate of change in velocity is used on high speedrotating equipmentsExample of applications: Unbalance Defective bearings Misalignment Looseness Oil whip Bend shaft
Infrared imagingThermo graphic Principle: Heat flow in a material is altered by the presence of some types of anomalies These changes in heat flow cause localized temperature differences in the material Slow heating of part reveals these anomaliesGeneral uses:To remotely examine surface temperatures of objects Measuring temperature of hot pressings Temperature measurement of material inside furnaces and material being heated by microwaves Observing temperature gradients across molded plastic Measuring temperature of circuit board components during operation Line scan mode enables measurement of a single lineEquipment: IR imaging system
X-RAYPrinciple:A source of radiation is directed toward an object a sheet of radiographic film isplaced behind the object the density of the image is a function of the quantity ofradiation transmitted through the object which in turn is inversely proportional tothe atomic number density and thickness of the objectEquipment: X-ray sources Radiograph scanners Digital imagesGeneral uses: Generation of images corresponding to density atomic number and thickness variation of static solid objects Check for internal defects such as voids cracks Determination of internal clearances between parts in an assembly