UT Defect Characteristics of Small-Diameter Pipe Welds in Ultrasonic Testing

2022-11-17

1. Overview In ultrasonic testing, the three key aspects of defect evaluation are localization, quantification, and characterization. Currently, research on defect localization and quantification in ultrasonic testing has reached a relatively mature stage; however, the characterization of defects remains underdeveloped. Ultrasonic testing standards mandate defect localization and quantification, but do not require defect characterization due to the inherent difficulties involved. This is because the ultrasonic reflection characteristics of a defect depend on its orientation, geometric shape, and its dimensions—length and thickness—in relation to the direction of ultrasonic wave propagation.

Method for Detecting “Internal Defects” in Fillet Welds Using Phased-Array Ultrasonic Testing

2022-11-10

Welding is a manufacturing process and technology that joins metallic materials by means of heating, high temperature, or high pressure. Various types of welded joints are widely used in petrochemical plants and play a crucial role in the fabrication of pressure-containing special equipment. Consequently, the quality of welded joints is of paramount importance for the safe operation of such equipment. Welding is a manufacturing process and technology that joins metallic materials by means of heating, high temperature, or high pressure. Various types of welded joints are widely used in petrochemical plants and play a crucial role in the fabrication of pressure-containing special equipment. Therefore

Current Status and Improvement Strategies for Pipeline In-Service Inspection Technologies and Management

2022-11-04

Pipeline defects have long been the primary cause of pipeline failure, and the use of internal inspection technologies to detect and identify such defects has become a widely recognized practice both domestically and internationally. To further promote the development of internal inspection technologies and enhance management standards, this study systematically reviews the technical capabilities and evolutionary trajectories of leading domestic and international companies providing internal inspection services for pipelines. It also analyzes the limitations of existing internal inspection techniques in addressing girth weld defects, crack defects, pinhole corrosion defects, and the assessment of pipeline stress states in oil and gas pipelines. Furthermore, the study identifies the challenges currently faced in the management of internal inspection technologies from three perspectives—government, pipeline operators, and internal inspection service providers—and proposes a multi-dimensional approach to application.

Ultrasonic Testing of Plates, Profiles, and Bars

2022-10-20

I. Ultrasonic Testing of Plates Ultrasonic testing of thick and medium-thick plates—using the shear-wave method. To detect defects that are oriented at a certain angle to, or even perpendicular to, the plate surface—such as cracks—it is necessary, when required, to supplement the inspection with shear-wave testing. The determination of the conditions for shear-wave testing of plates, including the calibration of the incident angle or the refraction angle (or K-value), is conducted in the same manner as for conventional shear-wave testing; sensitivity adjustment, however, is performed using reference test blocks made of the same grade, material, metallurgical condition, and surface condition as the test piece, with notches or cylindrical holes serving as reflectors.

Research on Crack Detection Using Radiographic Testing

2022-10-15

Radiographic Resolution As shown in Figure 3-3, a beam of radiation perpendicular to the surface of the test specimen is used to radiograph a metallic step block. In theory, the image on the radiographic film should consist of two regions of uniform blackness: one region of high blackness corresponding to the AO portion of the specimen, and another region of low blackness corresponding to the OB portion. The boundary between these two regions should exhibit a sharp, discontinuous transition in blackness, as illustrated in Figure 3-3a. However, in practice, the variation in blackness on the film is not abrupt. The “step-edge” image of the specimen is blurred,

Array Eddy Current Testing of Nuclear Fuel Cladding Tubes

2022-09-29

Nuclear fuel elements are the core components of a reactor, operating in harsh environments characterized by high temperature, high pressure, intense radiation, coolant erosion, and corrosive degradation. As the first safety barrier in a nuclear reactor, the cladding tube requires rigorous quality monitoring to ensure the safe operation of the reactor. Prior to fuel assembly loading, if defect parameters such as cracks, inclusions, and pitting in the cladding tube exceed established safety thresholds, the fuel rod will face a significantly elevated risk of failure. Therefore, it is essential to employ effective nondestructive testing methods to perform 100% inspection of cladding tubes. Currently, the primary NDT techniques for cladding tubes include ultrasonic testing, eddy current testing, and visual inspection. Eddy Current Testing of Cladding Tubes – Main

Corrosion Detection Technologies and Anti-Corrosion Measures for Oil and Gas Pipelines

2022-09-23

During operation, oil and gas pipelines are subject to corrosion caused by oxygen, hydrogen sulfide, and soil conditions, which adversely affect their service quality and service life and pose significant safety risks. This paper primarily examines the underlying corrosion mechanisms and explores corresponding corrosion detection technologies as well as appropriate anti-corrosion measures. During operation, oil and gas pipelines are subject to corrosion caused by oxygen, hydrogen sulfide, and soil conditions, which adversely affect their service quality and service life and pose significant safety risks. This paper primarily examines the underlying corrosion mechanisms and explores corresponding corrosion detection technologies as well as appropriate anti-corrosion measures.

The image quality indicator, unassuming yet crucial in radiographic testing

2022-09-17

In radiographic testing, the image quality indicator (IQI) is one of the most commonly used and critical inspection tools. Often unassuming—sometimes even tucked away in a corner and easy to overlook—it may appear at first glance as nothing more than a few metal wires or thin metal sheets. Yet it plays the role of the “unsung hero,” serving as an essential accessory for controlling and ensuring the quality of radiographic inspections. This leads us to pose a profound question: Do you remember whether you have ever made a mistake simply because you were not familiar with it? 1. What is an IQI? An IQI, also known as a radiographic image quality comparator, is primarily a tool used to inspect and quantitatively evaluate the image quality of radiographic films. It is also referred to by various other names, such as IQI or penetrameter. The material requirements for an IQI generally stipulate that it must be made from a material that is either identical to the test piece’s material or has similar radiographic absorption characteristics. IQIs incorporate artificial structures with controlled thickness differences—such as slots, holes, or metal wires—whose dimensions are related to the thickness of the test piece in specific ways. The IQI image on the radiographic film serves as permanent evidence that the radiographic examination was performed under appropriate conditions; however, the indication provided by the IQI does not represent the actual size of natural defects that could be detected in the test piece. Rather, it is a relative measure of sensitivity. 2. What are the classifications of IQIs? Currently, there are three main types of IQIs used in industrial radiography: wire-type, hole-type, and slot-type. Among these, the wire-type IQI is the most widely used and is adopted by most major industrial countries. In addition, some countries still use flat-hole-type IQIs—for example, the United States. The United Kingdom and France, on the other hand, employ stepped-hole-type IQIs. There is also a dual-wire-type IQI, which is not used to measure radiographic sensitivity but rather to assess radiographic unsharpness. Category 1: Wire-Type IQIs Based on the variation in wire diameter, wire-type IQIs can be further classified into arithmetic-series, geometric-series, constant-diameter, and single-wire types. Globally, the geometric-series IQI is currently the most prevalent. A wire-type IQI consists of a set of seven numbered metal wires connected together. All wires in each IQI must be made of the same material and embedded in a low-absorption matrix—such as an engineering-plastic housing—to ensure that their presence does not compromise image quality. The wires themselves should be arranged in parallel. The IQI marking comprises the designation of the largest-diameter wire, the wire material, and the standard code. The largest-diameter designation is placed on the side corresponding to the largest-diameter wire and simultaneously indicates the IQI number. According to the wire-diameter ratio, IQIs are divided into four models. IQIs can also be categorized by material: steel IQIs, aluminum IQIs, titanium IQIs, copper IQIs, and so on, represented by the codes FE, AL, TI, and CU, respectively. During radiography, the IQI material should match that of the test piece; if an IQI made of the same material is unavailable, one made of a material with a lower atomic number may be used as a substitute. Category 2: Flat-Hole-Type IQIs Flat-hole-type IQIs are manufactured by drilling small holes of specified dimensions into a uniformly thick plate. This type of IQI is recognized in U.S. ASME codes, MIL standards, European EN 1435, and Chinese GB 3323 standards. There are three options for selecting the IQI thickness T: 1%, 2%, or 4% of the exposure thickness. The corresponding hole diameters are IT, 2T, and 4T. IQIs come in rectangular and circular forms, with the latter being suitable for thicker workpieces. The sensitivity level of a flat-hole-type IQI is expressed as “thickness–hole type.” For example, 2-1T means that a 1T-diameter hole on a 2% thickness IQI can be detected; 1-2T means that a 2T-diameter hole on a 1% thickness IQI can be detected. Following this notation, each thickness of flat-hole-type IQI can display three sensitivity levels, and three different thicknesses can collectively show nine sensitivity levels: 1-1T, 1-2T, 1-4T, 2-1T, 2-2T, 2-4T, 4-1T, 4-2T, and 4-4T. In actual radiographic inspections, five of these sensitivity levels are typically used: 1-1T, 1-2T, 2-1T, 2-2T, and 2-4T. Flat-hole-type IQIs should be made from materials belonging to the same group or grade as the material being radiographed, or alternatively from materials with lower radiographic absorption characteristics than the test piece. Category 3: Slot-Type IQIs General-purpose wedge-shaped test blocks are available in two versions: stainless steel and aluminum, with the choice based on the most stringent materials actually used in practice. 3. How to Use an IQI Regardless of the type of IQI used, its placement directly affects the sensitivity reading indicated by the IQI. Therefore, when positioning the IQI, it is generally placed in areas within the radiographic field where sensitivity is relatively low—for example, on the surface of the workpiece far from the film or in regions with greater exposure thickness. If the unfavorable area can achieve the specified sensitivity, it is generally assumed that the favorable area will achieve even higher sensitivity. In certain special cases, the IQI cannot be placed on the source-side surface; in such instances, a comparative test must be conducted. The procedure involves fabricating a short test specimen with the same material, diameter, and wall thickness as the test piece, placing one IQI on both the inner and outer surfaces of the test area, adding an “F” mark to the IQI on the film side, and then performing radiography under the same exposure conditions as the test piece. On the resulting radiograph, the IQI index or relative sensitivity achieved by the source-side IQI is used to determine the corresponding IQI index or relative sensitivity that the film-side IQI should attain. When using a double-wall single-image IQI on the film side, an “F” mark must be added to indicate that the IQI is positioned on the film side. For flat-hole-type IQIs, placement requires positioning them at least 5 mm away from the edge of the weld being inspected, on the base metal surface, and under the IQI a shim of a specific thickness must be placed—approximately equal to the total excess height of the weld being inspected. The purpose of this shim is to ensure that the density of the inspected area is no less than 15% of the IQI’s density range, while the shim’s dimensions should exceed those of the IQI itself, so that at least three of the IQI’s contour lines are clearly visible in the radiograph. 4. Have You Ever Made These IQI Mistakes? As a nondestructive-testing professional new to the field, what are the most common mistakes made when using IQIs? A. Selection Errors When performing radiographic inspections on steel materials, failing to use a steel IQI and instead mistakenly choosing an aluminum IQI; selecting the wrong IQI for different thicknesses—for example, using a 1-6# IQI when a 6-13# model is required; using the wrong standard—for instance, applying an ASME-standard IQI when NB/T47013 specifies a particular marking system; or marking the IQI in a way that does not comply with the relevant standards. B. Placement Errors This is the most common mistake made by inspectors and also the easiest to overlook during the inspection process. Placing the IQI in the center of the radiograph (for non-tubular components)—the correct method is to position it at the 1/4 mark of the film or in an area of lower sensitivity. Reversing the orientation of the IQI’s thick and thin wires is another frequent error among beginners: the thick wire should be placed on the film’s inner side, while the thin wire goes on the outer side—not the other way around. Placing the IQI on the film side is also a common convenience-based mistake made during on-site inspections. According to standards, most IQIs should be placed on the source side; only in a few special cases are they placed on the film side, such as in double-wall single-image projections. When an IQI is placed on the film side, a lead letter “F” should be appropriately affixed to the IQI as a marker. The “F” mark must appear on the radiograph alongside the IQI’s own markings, and this fact must be noted in the inspection report. All content in this article has been collected from the internet for technical exchange and sharing purposes only. If any infringement occurs, please contact us, and we will promptly remove the offending material.

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