NON DESTRUCTIVE TEST The frequency of test was following the BS 5400 part 6:1999 as state below: All fillet weld, visual inspection and dye penetrate or magnetic particle test shall be carried out. All transverse weld butt weld in tension weld 10% of the length of longitudinal butt welds in tension flanges 5% of the length of longitudinal butt weld in compression flanges The non- destructive test is mainly divided to surface inspection and sub-surface Inspection: Surface inspection- Visual inspection, Dye penetration test and Magnetic Particle Test Sub- surface inspection – Radiographic (X-ray or Gamma) and ultrasonic testing ARHA SDN. BHD was carried out the NDT for this project and the codes of practice and standards which cover various types of constructions fabricated by welding work is AWS D1.1 Structural welding code (American) was adopted. The test has started on 1st April 2011 with the Ultrasonic testing and Magnetic Particle test. For the Radiographic test had was have to test at night time to prevent the radioactive For MAGNETIC PARTICLE TEST, the equipments used for testing are below:
Magnaflux Electro Magnetic Model- Yoke Y-6
White Contrast
To detect cracks by using ordinary magnetic particle, apply with magnetic particle paints evenly on the surface of the inspection object. When the paint are dried, spray ordinary magnetic particle to detected flaws, this paint makes contrast sharp in surface detection, making the detection of fine cracks easily.
Black Magnetic Ink/ ordinary magnetic particle fluid
This method is capable of detecting open surface and just below the surface flaws, the test specimen was magnetized by the “Magnuaflux Electro Magnetic” The magnetic field thus introduced into the specimen is composed of magnetic line of force.
Whenever there is a flaw which interrupts the flow of the magnetic line some of these lines must exit and re-enter the specimen. These points of exit and re-entry from opposite magnetic poles. Whenever minute magnetic particle are sprinkled onto the surface of such a specimen, these particles are attracted by these magnetic poles to create a visual indication approximating the size and shape of the flaw.
Flux
Test specimen
Electro Magnet
ULTRASONIC INSPECTION Equipment
: Main unit comprising pulse generator, display oscilloscope, probe
Display Oscilloscope
Probes 70 Deg. 4Mhz Angle Probe
Mode of operation: A pulse of electrical energy is fed to the probe in which a piezo-electric crystal converts it to mechanical vibrations at an ultrasonic frequency. The vibrations are transmitted (via a layer of grease to exclude the air) through the work. If they encounter a defect some are reflected back to the probe, where they regenerate an electrical signal. A cathode ray tube trace, started when the original signal is sent, displays the reflected defect signal and from it time - indicating distance from probe, and amplitude - indicating defect size, can be calculated. Operating parameters. Probe frequency 1 - 5MHz Portability Good Access Good (can be battery operated) Thickness range 5 - 500mm Minimum defect size 5mm wide
The weld for Joint at B-G 2 Butt weld for the web plate was rejected after Ultrasonic Test carried out. A defected found at depth 13-15mm with length of 50mm. The weld had been repaired and retest at 8th April. The Ultrasonic test was adopted to re-check on the rejected portions.
Grease
Setting out for the operating parameter
The operating parameter adopted for 25mm flange plated are 60Deg. 5Mhz Angle Probe. Full skip method
Pulse
Daley = 0s
100mm test range
Velocity = 3240m/s Angle = 60⁰
Overall advantages. Immediate presentation of results. Not necessary to evacuate personnel. Can be battery powered.
Overall limitations. Trained and skilled operator needed. No pictorial record.
Safety. Moderate care needed as for all electrical equipment.
WELD JOINTS The most commonly occurring defects in welded joints are porosity, slag inclusions, lack of sidewall fusion, lack of inter-run fusion, lack of root penetration, undercutting, and longitudinal or transverse cracks. With the exception of single gas pores all the defects listed are usually well detectable by ultrasonic. Ultrasonic flaw detection has long been the preferred method for nondestructive testing in welding applications. This safe, accurate, and simple technique has pushed ultrasonic‟s to the forefront of inspection technology.
Phased array pulse-echo technique the phased array technique uses a mosaic of transducer elements in which the timing of the elements' excitation can be individually controlled to produce a certain desired effect, such as steering the beam axis or focusing the beam.
Pulse-Echo technique The pulse echo technique is an ultrasonic test in which discontinuities are detected by the reflected echoes from defects.
Time-of-flight Diffraction (TOFD) technique The time-of-flight diffraction technique is an ultrasonic test that relies on the diffraction of ultrasonic beams from the "corners" and "ends" of internal structures (primarily defects) in a component being tested.
Creeping wave technique The creeping wave technique is an ultrasonic test in which discontinuities are detected by the return of a creeping wave that tracks the surface of the component being tested.
RADIOGRAPHY TEST Type of operation. Static - development may be mechanised. Equipment. Radioactive isotope in storage container. Remote handling gear. Lightproof cassette. Photographic development facilities. Darkroom and illuminator for assessment.
Control housing -50ft
Amersham Gamma Ray Projector – Model: Delta 880
Pistol Control
Survey Meter-ND 2000
Pocket dosimeters are used to provide the wearer with an immediate reading of his or her exposure to x-rays and gamma rays Pocket dosimeter
Wire penetrameter are used as the Image Quality Indicator on films
Wire Penetrameter
880 Delta Series Source Projectors Model 880 series source projectors are used for industrial applications of gamma radiography to inspect materials and structures in the density range of approximately 2.71 g/cm3 through 8.53 g/cm3. SENTINELTM Model 880 Delta, 880 Elite and 880 Omega source projectors are portable, lightweight and compact industrial radiographic exposure devices. The patented device body consists of a titanium „S‟ tube and cast depleted uranium (DU) shield contained within a 300series stainless steel tube with stainless steel discs welded at each end forming a cylinder shaped housing. The discs are recessed to provide protection for the rear mounted locking mechanism and front mounted outlet port. The horizontally oriented design allows the locking mechanism, source assembly connector and outlet port to be easily operated, simplifying connection of source guide tubes and remote controls. EXPOSURE DEVICE The exposure device body, containing the DU shield, locking mechanism, outlet port, protective covers and required labels*, comprises the radioactive material transport Type B(U) package. REMOVABLE JACKET An impact resistant plastic jacket surrounds the exposure device to protect labels and provide the means for carrying andplacement during radiographic operations. The three models are identified by jacket color; yellow for the 880 Delta, blue for the 880 Elite and orange for the 880 Omega *Multilingual labeling is available upon request. For Batukawa Bridge Project
Sources Isotope
Selenium-75
Iridium-192
Cobalt-60
Assembly Model Number Gamma Energy Range
A424-25W 66-401 keV
Half-Life Aproximate Steel Working Thickness Maximum Source Capacity
120 Days 3-29 mm
A424-9 A424-19 206-612 keV 1.17-1.33 MeV 74 Days 5.27 Years 12-63 mm 50-150 mm
150Ci 5.55TBq
150Ci 5.55TBq
65mCi 2.40GBq
Ytterbium169 91810 8-308 keV 32 Days 2-20 mm 20Ci 0.74 TBq
Setting up for Radiographic Test
Films Source positioning rod
Source guide tube
Front Side
Back Side
The Ray Projector was connect with the control housing tube and the control pistol, another side of the projector then connected to the source guide tube at the Front side of the welding. This method of weld testing makes use gamma rays, produced by a radioactive isotope. The basic principle of radiographic inspection of welds is the same as that for medical radiography. Penetrating radiation is passed through a solid object, a weld onto a photographic film, resulting in an image of the object's internal structure being deposited on the film. The amount of energy absorbed by the object depends on characteristic, its thickness and density. Energy not absorbed by the object will cause exposure of the radiographic film. These areas will be dark when the film is developed. Areas of the film exposed to less energy remain lighter. Therefore, areas of the object where the thickness has been changed by discontinuities, such as porosity or cracks, will appear as dark outlines on the film. Inclusions of low density, such as slag, will appear as dark areas on the film while inclusions of high density, such as tungsten, will appear as light areas. All discontinuities are detected by viewing shape and variation in density of the processed film.
Defects appears dark outline due to films exposed more energy
Radiographic testing can provide a permanent film record of weld quality that is relatively easy to interpret by trained personnel. This testing method is usually suited to having access to both sides of the welded joint. Although this is a slow and expensive method of nondestructive testing, it is a positive method for detecting porosity, inclusions, cracks, and voids in the interior of welds. It is essential that qualified personnel conduct radiographic interpretation since false interpretation of radiographs can be expensive and interfere seriously with productivity. There are obvious safety considerations when conducting radiographic testing. X-ray and gamma radiation is invisible to the naked eye and can have serious heath and safety implications. Only suitably trained and qualified personnel should practice this type of testing.
Image Quality Indicator
Project Name
Girder No: B-G 37
Flange
Thickness 25mm
Cluster porosity / Slag Inclusion
Cluster porosity is caused when flux coated electrodes are contaminated with moisture. The moisture turns into a gas when heated and becomes trapped in the weld during the welding process. Cluster porosity appear just like regular porosity in the radiograph but the indications will be grouped close together. Slag inclusions are nonmetallic solid material entrapped in weld metal or between weld and base metal. In a radiograph, dark, jagged asymmetrical shapes within the weld or along the weld joint areas are indicative of slag inclusions.
Lack of fusion / penetration
Lack of fusion is a condition where the weld filler metal does not properly fuse with the base metal. Appearance on radiograph: usually appears as a dark line or lines oriented in the direction of the weld seam along the weld preparation or joining area Incomplete penetration (IP) or lack of penetration (LOP) occurs when the weld metal fails to penetrate the joint. It is one of the most objectionable weld discontinuities. Lack of penetration allows a natural stress riser from which a crack may propagate. The appearance on a radiograph is a dark area with well-defined, straight edges that follows the land or root face down the center of the weldment.
Interpretation of radiographs takes place in three basic steps: (1) detection, (2) interpretation, and (3) evaluation. All of these steps make use of the radiographer's visual acuity.
ACCEPTANCE CRITERIA The acceptance criteria for the Non- Destructive Test was followed the AWS (American Welding Society) D1.1 Section 6. The visual inspection was carried out by the KKB Engineering QA/QC Team, Mr. Hashim, QA/QC Manager and his crew once the welding completed.
Automated Ultrasonic Testing Versus Radiography Testing Ultrasonic technology has been proven very effective for pressure vessel weld inspections and it is easily adapted to common codes such as API and ASME Sec III, V, VIII, CC2235, CC2599, and CC2600. Comparing the Indications
Analysis of the weld inspection results given by UT and radiography shows that UT provides both depth and height information, and is more sensitive to planar-type defects while eliminating radiation hazards.
ID 1
Type of Defect Toe crack
2
Centerline crack
3
Porosity
4
Incomplete root penetration
Measurements Performed by UT Radiography Position X, Y, and Z Position X and Y Length sizing Length sizing Height sizing Position X, Y, and Z No detection Length sizing Height sizing Position X, Y, and Z Position X and Y Length sizing Length sizing Position X, Y, and Z Position X and Y Length sizing Length sizing Height sizing
Ultrasonic Weld Inspection Solutions Olympus has created the UT solutions (automated ultrasonic testing) to provide you with an affordable means to inspect welds according to code. These solutions are portable and can be put to work virtually anywhere. The perfect combination of acquisition unit, scanner, encoder, and software makes the inspection of pressure vessel welds and other welds an easy task.
Fast inspection of small- and large-diameter welds 100 % volumetric weld coverage Adaptable to butt welds, circumferential welds, long seams, one-sided access configuration, and most common weld profiles Inspection of wall thicknesses from 8 mm to 300 mm and part diameters from 100 m to flat Digital archiving of inspection data Elimination of film archiving Portable for in-house and field inspections Improved productivity compared to radiography Improved probability of detection (POD) compared to radiography Combining Different Techniques for Full-Weld Coverage and Improved Efficiency
