Guided Waves Measurement Techniques in Pitch-Catch Configuration

Guided waves testing allows a long-range screening in pipes of different types and represents an effective and powerful non-destructing technique for defect detections using a limited number of points of measures. After the characterization through a general theoretical analysis, the focus is set to a real steam discharge pipe with a high mechanical complexity used for many years in a research plant now dismissed. The experimental method applied here is the pitch-catch configuration of two magnetostrictive sensors. The objective of this paper is to establish a strong theoretical background to pave the way for a robust experimental investigation. Preliminary experimental results are consistent with the theoretical analysis.

Guided Waves in Pitch-Catch Configuration: A Theoretical Framework to Steer Toward Experimental Tests

Guided waves testing allows a long-range screening in pipes of different types and represents an effective and powerful non-destructing technique for defect detections using a limited number of points of measures. This kind of testing hence represents an appealing technique not only for the Oil and Gas industries but also for the Nuclear Industry, in particular regarding the Structural Health Monitoring of Nuclear Power Plants components. Another point of strength of this technique is that it can be applied in different configurations as the pulse-echo (the same probe is used both for transmission and signal receiving) or the pitch-catch (two symmetric probes are used one for the signal transmission and the second one for the signal receiving). In this way, the guided wave testing with magnetostrictive sensors can be reliably used for the short and long-term monitoring of Nuclear Power Plants components. The objective of this paper is to establish a strong theoretical background to pave the way for a robust experimental investigation. In particular, after the characterization through a general theoretical analysis, the focus is on a real steam discharge pipe with a high mechanical complexity used for many years in a research facility and now dismissed. The experimental method applied is the pitch-catch configuration of two magnetostrictive sensors. Preliminary experimental results conducted on a real complex steam discharge pipe are consistent with the theoretical analysis.

Pressure loss reduction of pipe elements

A theoretical research was conducted from 2016 to 2018 which aimed to reduce the head loss of pipe networks in the pump stations. The results were promising and predicted an average head loss reduction by 30%. Afterwards, physical experiments were carried out to test the effectiveness of the new pipe designs. Two new prototype pipe sections were installed into one of our pump stations. The experiment was successful as two unique pipe sections installed in the discharge pipe reduced the head loss of the pump station by 25–26%. According to these results, we can set a target value of 30% head loss reduction at full pump station pipe reconstruction.

DESCRIPTION OF THE PROCESS OF A TWO-PHASE MEDIUM FLOW FROM THE DISINTEGRATOR GRINDING CHAMBER IN A PLANE PERPENDICULAR TO THE AXIS OF ROTATION OF THE ROTORS INTO A TANGENTIAL SEMI-INFINITE BRANCH PIPE

In recent decades, disintegrator type mills have become widely used for grinding, activating and mixing construction materials. The efficiency of these mills is largely influenced by the design parameters of the working chamber, loading and unloading units, as well as some technological parameters, such as the speed of rotation of the rotors. In this article, an attempt is made to determine the conditions for the departure of material particles from the disintegrator grinding chamber into the tangential discharge pipe and the geometric parameters of this pipe, based on the conditions for the flow of a two-phase medium from the external row of shock elements to the discharge zone. Figure 1 shows the flow diagram of the two-phase medium from the disintegrator grinding chamber to the tangential discharge pipe. It is assumed that the speed of movement of the two-phase medium in this section does not change modulo and the length of the tangential branch pipe is significantly greater than its width. The formula (26) shows the density of the unit volume of kinetic energy of a two-phase medium along the "oy" axis, as well as the change in the density of the unit volume of energy spent on the rotation of the velocity vector relative to the "oy"axis. As a result of theoretical calculations, the obtained formula (15) allows to determine the diameter of particles entering the tangential discharge pipe from a circular trajectory (11), and formulas (36) and (37) describe the process of rotation of the velocity vector of a two-phase medium when the disintegrator flows into the tangential discharge pipe. Figure 2 shows a graph based on the intersection of expression (15), which allows to determine the range of diameters of particles entering the tangential branch pipe, depending on the specified conditions, design and technological parameters. Figures 3 and 4 show graphs in accordance with the analytical expression (35) describing the change in the rotation angle of the velocity vector of a two-phase medium. The results of this article can be used to design the discharge unit of the disintegrator with a tangentially located discharge pipe.

Investigations on Flow Characteristics in Diffuser-Discharge-Channel of Volute Casing

The volute casing used in centrifugal pumps is efficient for the transformation of kinetic energy into pressure energy, however, its asymmetric hydraulic design makes the flow in diffuser-discharge-channel (DDC) inhomogeneous, resulting in unsatisfactory flow patterns. In this study, the unsteady numerical simulations are carried out to investigate the transient flow characteristics in DDC. The accuracy of numerical results is found to agree well with experimental performance and pressure fluctuations. It is observed that the flow in DDC is significantly uneven. At the elbow of DDC, the static pressure on the volute left side (VL) is larger than the volute right side (VR) due to the flow impact and flow separation respectively. Thereby, this high-pressure gradient induces the secondary flow on the cross sections of DDC. Further, there is an obvious dependency of pressure fluctuations in the discharge pipe on the strong interaction between the impeller and tongue, in which four small peaks and four large peaks can be observed. At each moment, the pressure on VL gradually decreases from the inlet of discharge pipe to the pump outlet, while it increases on VR, finally, two sides tend to be the same. The pressure fluctuation intensity gradually becomes equivalent-distributed. In particular, it should be noticed that the energy loss in the diffuser part is larger than the discharge pipe, which requires a redesign concerning hydraulic performance. This study can help to better understand the transient flow characteristics and provide guidance for reducing flow loss in the volute casing.