Category Archives for In-Service Inspection
Acoustic Emission Testing – Applications and Limitations
AE can be used for the in-service inspection of pressure vessels to detect cracks that have resulted from any form of deterioration during service that can cause cracking. It can be a very sensitive NDE method for detecting cracks, but … Continue reading
Acoustic Emission Testing – Test Pressure
Acoustic emission tests of a pressure vessel are usually conducted by filling the vessel with water, and slowly increasing the hydrostatic pressure until it exceeds the maximum pressure that the vessel has experienced during recent operation. Early development of acoustic … Continue reading
Radiographic Examination – Applications and Limitations
It is sometimes thought that RT is the best NDE method that can be used for detecting flaws, because it is mandated by the ASME Code for certifying the quality of newly constructed pressure vessels. This is not true. RT … Continue reading
Radiographic Examination – Radiograph Quality
The acceptability of a radiograph for the detection of flaws is determined with a device, referred to as a “penetrameter,” that is placed upon the surface of the workpiece when the exposure is made. Penetrameters are relatively thin pieces of … Continue reading
Radiographic Examination – Exposure
The exposure of the photographic film by radiation passing through the workpiece is determined by the intensity of the radiation multiplied by the time of the exposure. The optical density of the developed negative increases with increasing exposure. ASME Code, … Continue reading
Radiographic Examination – Photographic Film
The radiation which passes through the workpiece is recorded by photographic film. The radiographs are usually interpreted visually with the aid of a high intensity light source (light box), but optical densitometers or image analyzers are occasionally used. Two primary … Continue reading
Radiographic Examination – Radiation Sources
Both x-rays and gamma rays can be used as the incident radiation. Energy and intensity are the most important characteristics of the incident radiation. The energy of the incident radiation determines its ability to penetrate the workpiece. Higher energy radiation … Continue reading
Radiographic Examination – Physical Principles
X-rays and gamma rays penetrate steel, but the intensity of the incident radiation will be attenuated as it passes through the material. The degree of attenuation depends on the thickness and density of the material. Flaws can have the effect … Continue reading
Radiographic Examination (RT)
RT is very useful for detecting both surface and internal flaws, and it is the primary NDE procedure required by the ASME Code to verify the quality of welds during construction. However, the associated radiation hazard makes it difficult to … Continue reading
Shear Wave UT – Applications and Limitations
UT is a very efficient NDE method. A large amount of data for evaluating the integrity and reliability of a vessel can be obtained in a relatively short period of time, without requiring extensive preparation of the vessel or interfering … Continue reading