LARSEN AND TOUBRO LIMITED HEAVY ENGINEERING DIVISION NON DESTRUCTIVE EXAMINATION ULTRASONIC TESTING LARSEN AND TOUBRO LIMITED HEAVY ENGINEERING DIVISION

ULTRASONIC SYSTEMS PULSE ECHO SYSTEM RESONANCE SYSTEM THROUGH TRANSMISSION SYSTEM PULSE ECHO SYSTEM RESONANCE SYSTEM

ULTRASONIC SYSTEMS THROUGH TRANSMISSION SYSTEM: 1. Sound Energy is continuous or Pulsed 2. Separate transmitter / reciever 3. Soundness of test specimen based on energy lost 4. Indicates only presence of defect and not the location Transmitter Reciever echo Reduced echo Reciever Through Trans. Testing CRT Display - defect free area CRT Display - defective area

Fundamental Resonance Frequency F = V/2T RESONANCE SYSTEM 1. CONTINUOUS WAVES ARE NEEDED. 2. USED FOR THICNESS MEASUREMENT, LACK OF BONDING IN CLAD & FOR DETECTING LAMINATION. T= 1 Resonance will occur only when the specimen thickness is equal to a half wave length or an exact multiple of a half wave length. Fundamental Resonance Frequency F = V/2T

PULSE ECHO SYSTEM 1. WIDELY USED FOR FLAW DETECTION 2. SOUND ENERGY IS TRANSMITTED IN PULSES 3. USED IN CONTACT AND IMMERSION METHODS 4. CRT DISPLAY - A-SCAN : ANALOG DISPLAY - TIME VERSUS AMPLITUDE B-SCAN : CROSS SECTIONAL VIEW C-SCAN : PLANAR VIEW 5. MAY BE USED IN CONTACT AS WELL AS IMMERSION TESTING OF PLATES, PIPES, FORGINGS , CASTINGS & WELDS.

ULTRASONIC EXAMINATION Basic Principles Ultrasonic Pulse Echo equipment generates high voltage electrical pulses. These pulses are applied to the Transducer ( Probe ) which converts them into mechanical vibrations ( sound energy at high frequency i.e. Ultrasonic sound energy > 20,000 cycles per second ) that are transmitted into the material being tested. The reflected sound energy either from the back surface or from discontinuities is again converted into electrical pulses by the transducer and is displayed on the CRT ( Cathode ray tube )

TYPICAL A- SCAN DISPLAY Normal Beam Scanning: CRT Display Transducer A B C Defect Specimen Thicknes (Time-Distance) A- Initial Pulse B- Defect Echo C- Back Surface Echo

TYPICAL A-SCAN DISPLAY Angle Beam scanning CRT Display A B Time - Distance A- Initial Pulse B- Defect Echo

ULTRASONIC TRANSDUCERS 1. LONGITUDINAL MODE PROBES ARE USED IN GENERAL FOR STRAIGHT BEAM EXAMINATION. 2. SHEAR WAVE PROBES ARE USED FOR ANGLE BEAM EXAMINATION. 3. HIGHER THE FREQUENCY OF THE PROBE, HIGHER WILL BE THE SENSITIVITY AND RESOLUTION BUT LESSER PENETRATION. 4. LOWER THE FREQUENCY OF PROBE LESSER WILL BE THE SENSITIVITY AND RESOLUTION BUT HIGHER WILL BE THE PENETRATION.

ULTRASONIC TRANSDUCERS 1. IN GENERAL CONTACT TESTING IS CARRIED OUT USING PROBES IN THE FREQUENCY RANGE OF 1 TO 5MHz. 2. HIGHER FREQUENCY PROBES IN RANGE OF 2.25MHz TO 25MHz ARE USED IN IMMERSION TESTING. 3. LONGITUDINAL MODE COARSE GRAIN ANGLE BEAM PROBES FOR SPECIAL APPLICATION ARE AVAILABLE FOR TESTING OF AUSTENITIC / NICKLE BASE WELDS. 4. TWIN CRYSTAL PROBES ARE USED FOR TESTING WELDS AND MATERIALS FOR BETTER NEAR SURFACE RESOLUTION.

NDE PERSONNEL QUALIFICATIONS NDE Personnel are qualified as per L&T’s Written Practice which is based on SNT-TC-1A of ASNT LEVEL -I Functions as per the written instructions from Level II/III. LEVEL - II Prepare Procedures , carry out testing , guide level -I , evaluate results etc. LEVEL-III Train & qualify Level-I & II personnel as per L&T’s Written Practice , prepare procedures, approve procedures etc.

ULTRASONIC EXAMINATION APPLICATION Plates are usually tested for laminations using normal beam probes. For special application such as Nuclear / Aerospace, plates are also tested with angle beam. Forgings depending on their shape and size are tested using normal as well as angle beam probes. Weld overlay is usually tested with twin crystal normal beam probes. In some special application angle beam scanning is also carried out. Welds such as butt / nozzle welds are tested both with normal & angle beam probes

ULTRASONIC EXAMINATION Application ( cont..) Frequency of sound energy used in general for contact testing is up to 5 MHz, whereas in immersion testing the frequency used may be as high as 25 MHz. Probe angles used in general in angle beam examination are 45, 60 & 70 Deg. Some other angles such as 35, 80 deg etc are also used for some special applications depending on the geometry of the specimen. In general normal beam testing is carried out using longitudinal mode, whereas shear waves are used in case of angle beam scanning. But in some cases like angle beam examination of weld overlay, longitudinal waves are used for better penetration.

ULTRASONIC EXAMINATION ADVANTAGES Testing can be carried out with one side access. Any thickness on higher side can be tested ( Superior penetrating power ). Results are immediate. Exact depth and locations of flaws can be estimated. Compact and portable equipments are available.

ULTRASONIC EXAMINATION LIMITATIONS Highly skilled and trained personnel are required. Coarse grain weld material like Austenitic stainless steel & Nickel based non ferrous welds are difficult to test. Equipment cost is very high for automated testing with recording / imaging facility.

ULTRASONIC EXAMINATION SPECIAL APPLICATIONS / DEVELOPMENTS 1. High Temperature Ultrasonic Examination of welds upto 250 ° C using special purpose RTD make probes & Silicone oil as couplant. 2. Ultrasonic Examination of Ausenitic Stainless Steel welds using Coarse Grain Longitudinal Mode Probes.

ULTRASONIC EXAMINATION SPECIAL APPLICATIONS / DEVELOPMENTS contd... Ultrasonic Examination of Coarse Grain Nickle Based weld overlay for detecting underbead transverse cracks at the clad interface using RTD make , longitudinal mode, twin crystal focussed probes.

SPECIAL APPLICATIONS / DEVELOPMENTS contd... DC LOW SPEED MOTOR PROBE - FIXTURE ASSEMBLY XY - RECORDER USM - 3S FLAW DETECTOR REDUCTION GEAR BOX CLAD TUBESHEET PROBE 0 2 4 6 8 10 SCHEMATIC DIAGRAM Ultrasonic Examination of Tube# Tubesheet welds in Carbamate Condenser using Auto-Immersion Technique.

ULTRASONIC EXAMINATION TRANSDUCERS FOR SPECIAL APPLICATIONS: 1. Panametric make Videoscan Immersion Transducer with Mirror Reflector for Ultrsonic Examination of Tube to Tubesheet welds. 2. High Temperature RTD make probes. 3. RTD make coarse grain angle beam probe for testing of overlay.

EQUIPMENTS & ACCESSORIES ULTRASONIC EXAMINATION EQUIPMENTS & ACCESSORIES ULTRSONIC FLAW DETECTORS: 1. USM 3S - MAKE- KRAUTKRAMER GERMANY RANGE 5- 15000MM 2. USIP -11 - MAKE - KRAUTKRAMER GERMANY RANGE 5-15000MM 3. USN - 50 - MAKE - KRAUTKRAMER GERMANY RANGE 5-5000MM STORAGE FACILITY UPTO 30 CALIBRATIONS DIGITAL AND ANALOG DISPLAY 4. USK -6 /7S -MAKE - KRAUTKRAMER GERMANY RANGE 10-2500MM

EQUIPMENTS & ACCESSORIES contd... ULTRASONIC EXAMINATION EQUIPMENTS & ACCESSORIES contd... ULTRASONIC TRANSDUCERS Contact Probes : Normal, 35° ,45°,60 °,70°,80° Frequency 1MHz to 4MHz Krautkramer make Immersion Type probes : Frequency 5MHz to 15 MHz Krautkramer, Panametrics & Ultran make Finger Tip probes: Miniature probes , Frequency 2.25MHz - 5MHz Make - Krautkramer.

VARIOUS TYPES OF WELDS AND MATERIALS EXAMINED BY UT White metal lining examination on bearings. Austenitic stainless steel welds on Nuclear End Shields. Austenitic S.S to Inconel Weld joints in Steam Generators. Weld joints on Maraging Steel M-250 materials for space application. Monel, Inconel & Austenitic stainless steel weld overlay Carbon Steel and Alloy Steel welds and materials Titanium clad testing for bond and flaw detection