Ultrasonic methods radiography

Studying modem approaches for such schemes, one can see that knowledge of operational conditions and potential degradation mechanisms play a prominent role. Surprisingly, the role of NDT is often limited to tlie use of conventional methods such as ultrasonic wall thickness measurements, ultrasonic inspection, radiography, and last but not least visual inspection. 

By comparison with other NDC methods, such as liquid penetrant examination, magnetic particle, eddy current testing, and radiography, the ultrasonic method is the only technique that is applicable to a wide range of materials. 

Other NDT Methods. Radiography (x-ray) inspection can be used to detect voids or discontinuities in the adhesive bond. This method is more expensive and requires more skilled experience than ultrasonic methods. The adhesive must contain some metal powder or other suitable filler to create enough contrast to make defects visible. This method is applicable to honeycomb sandwich structures as well as metal and nonmetal joints. 

Measurement sensitivity divides the metal loss methods. Ultrasonics and radiography are usually considered as inspection methods. Typically, ultrasonics has a measurement resolution of around 50 pm (0.002 in.), and radiography 250 p,m (0.010 in.). Consequently, these types of measurements are typically made annually. Corrosion test specimens (coupons) assess metal loss typically over a one to three month interval. Electrical resistance probes, as an automatic coupon, assess metal loss typically over a few hours to a few weeks. 

Other NDT methods. Radiography (x-ray) inspection can be used to detect voids or discontinuities in the adhesive bond. This method is more expensive and requires more skilled experience than ultrasonic methods. 

Projection radiography is widely used for pipe inspection and corrosion monitoring. Film digitisation allows a direct access to the local density variations by computer software. Following to a calibration step an interactive estimation of local wall thickness change based on the obtained density variation is possible. The theoretical model is discussed, the limitations of the application range are shown and examples of the practical use are given. The accuracy of this method is compared to results from wall thickness measurements with ultrasonic devices. 

The results of the review exercise described above confirmed that all shipyards do not have the same attitude towards quality. Whilst the results presented by most of the yards visited were reasonably consistent at 0.5 - 4.5 % repair rate regardless of NDE method, the results from other yards were less satisfactory. The exercise showed that in some yards repair rates were regularly in excess of 10% and that repair rates for radiography tended to be higher than those for ultrasonics. 

Considerable corrosion monitoring is carried out utilising invasive methods, i.e. where the corrosion sensor is required to penetrate the pipe or vessel wall. Avoidance of penetration using non-invasive methods (thin layer activation, ultrasonics, radiography and magnetic fingerprinting) is receiving considerable developmental attention. 

Nondestructive testing (NDT) is used to assess a component or structure during its operational lifetime. Radiography, ultrasonics, eddy currents, acoustic emissions, and other methods are used to detect and monitor flaws that develop during operation (Chapter 7). 

Other Examination. All circumferential butt and miter groove welds shall be examined by 100% radiography in accordance with para. IP-10.5.2. Alternatively, when specified by the engineering design, ultrasonic examination 100% shall be performed in accordance with para. IP-10.5.5. Socket welds and branch connection welds that are not radiographed shall be examined by magnetic particle or liquid penetrant methods in accordance with para. IP-10.5.4 or IP-10.5.3. 

There are several methods of layering in common use ( ) thick layers shrunk together (2) thin layers, each wrapped over the other and the longitudinal seam welded by using the prior layer as backup and (3) thin layers spirally wrapped. The code rules are written for either thick or thin layers. Rules and details are provided for all the usual welded joints and nozzle reinforcement. Supports for layered vessels require special consideration, in that only the outer layer could con-triDute to the support. For lethal service only the inner shell and inner heads need comply with the requirements in Subsec. B. Inasmuch as radiography would not be practical for inspection of many of the welds, extensive use is made of magnetic-particle and ultrasonic inspection. When radiography is required, the code warns the inspector... 

It is perhaps less easy to excuse the lack of a chapter on non-destructive testing. The reason is a mixture of the fact that the major NDT techniques are, in the main only applied to a few particular rubber products and the realisation that to properly describe all methods would require a book, not a chapter. It is, however, worth remembering that it is not only ultrasonics, radiography, holography and so on which are non-destructive. A number of the more traditional rubber tests, for example electrical properties, many dynamic tests, hardness and dimensional measures leave you with the product intact. There are text books which deal with NDT techniques generally and. a comprehensive review of NDT of polymers by Gross in Handbook of Polymer Testing3. 

The Dow Freeport in-service inspection procedures are similar to those reported earlier in this chapter. The Dow out-of-service (internal) inspection includes ultrasonic thickness measurements at all benchmark locations. Other test methods include shear wave ultrasonics, eddy current, and radiography. Engineers use ultrasonic thickness readings to project the remaining useful life of the vessel and to determine when the next internal inspection should be scheduled. 

The adopted methods were x-ray radiography (RT-X), especially concerning circumferential and longitudinal joints magnetic particle testing (MT) ultrasonics (UT) tensile and cold-bend test macroscopic sections hardness test metallographic examinations microanalysis (EDS) SANS. 

The choice of the nondestructive technique used in the examination of the sample on hand also depends upon the complexity of the shape of the sample. The following order of the methods is in progressively increasing complexity of the shape of the sample to be examined acoustic microscopy, microwave method, eddy current, magnetic particle, X-ray radiography, ultrasonics, liquid penetrant and visual methods. 

Lack of penetration Processing Ferrous and nonferrous weldments Radiography, ultrasonics confined to specific cases Eddy current method used for nonferrous samples Magnetic particle and liquid penetrant methods when back surface of weld is visible... 

Intergranular corrosion Service Nonferrous Liquid penetrant method is primary choice, radiography, eddy current method and ultrasonics may be used with some limitations... 

There are other methods of NDI other than X-ray radiography. One of them is ultrasonic NDI. In this technique, ultrasonic waves are used to investigate the interior of a ceramic piece. An ultrasonic transducer placed on the surface of the ceramic piece sends the ultrasonic waves received by a sensor found either within the ultrasonic transducer or at another location on the surface of the ceramic piece. Ultrasonic waves are scattered emd reflected back finm the surfaces and defects within... 

---