Wear Diagnostics of the Thrust Bearing of NK-33 Turbo-Pump Unit on the Basis of Single-Coil Eddy Current Sensors

The problem of early wear diagnostics of the combined journal-and-thrust bearing of the turbo-pump unit (TPU) of the liquid-propellant rocket engine NK-33 is considered. A feature of the problem is the significant restriction on modifications of the power plant’s design. The original solution based on replacing the standard induction sensors of the turbo-pump rotational speed currently used in TPU by single-coil eddy current sensors (SCECS) with sensitive elements in the form of a segment of a linear conductor is proposed. The SCECS provide the monitoring of the axial displacement of the shaft in the thrust bearing, which characterizes the state of the unit and increases with the bearing wear. The function of the TPU shaft’s rotational speed measuring also remains. The article describes the proposed approach as well as a laboratory prototype of the system for early detection of the TPU thrust bearing’s wear. The results of the prototype research that confirm the feasibility of the proposed approach are analyzed.

Electrical-resistivity characterization of an industrial site using long electrodes

An electrical-resistivity survey was completed at the T tank farm at the Hanford nuclear site in Washington State, U.S.A. The purpose of the survey was to define the lateral extent of waste plumes in the vadose zone in and around the tank farm. The T tank farm consists of single-shell tanks that historically have leaked and many liquid-waste-disposal facilities that provide a good target for resistivity mapping. Given that the site is highly industrialized with near-surface metallic infrastructure that potentially could mask any interpretable waste plume, it was necessary to use the many wells around the site as long electrodes. To accommodate the long electrodes and to simulate the effects of a linear conductor, the resistivity inversion code was modified to assign low-resistivity values to the well’s location. The forward model within the resistivity code was benchmarked for accuracy against an analytic solution, and the inverse model was tested for its ability to recreate images of a hypothetical target. The results of the tank-farm field survey showed large, low-resistivity targets beneath the disposal areas that coincided with the conceptual hydrogeologic models developed regarding the releases. Additionally, in areas of minimal infrastructure, the long-electrode method matched the lateral footprint of a 3D surface-resistivity survey with reasonable fidelity. Based on these results, the long-electrode resistivity method may provide a new strategy for environmental characterization at highly industrialized sites, provided a sufficient number and density of wells exist.

Modeling and analysis of the response of a triaxial, frequency-domain electromagnetic induction sensor to a buried linear conductor

This paper presents analytical modeling results for a triaxial frequency-domain electromagnetic-induction (EMI) sensor over a homogeneous earth containing a long linear conductor. Although the conductor studied is intended to represent an underground wire or pipe, it can represent any subsurface, linear geologic structure that can channel current. Treating the sensor transmitter as a vertical magnetic dipole, the model combines the well-known solution for the magnetic field arising from the interaction with the earth with the solution for the induced magnetic field from the excited subsurface conductor. Expressions for the three components of the magnetic field at an arbitrary point above the earth are presented. Two types of coupled, moving transmitter-receiver configurations (coaxial and coplanar) wereconsidered, and the model is sufficiently flexible to allow for many other sensor variations to be studied. Characteristics of the sensor signals were explored through several parametric modeling studies that demonstrate the sensitivity of the signals to transmitter frequency, earth conductivity, conductor depth, sensor geometry, and crossing angle. Using simple relationships developed from analysis of the sensor signals, key parameters such as conductor depth and orientation can be estimated. The ability of the model to predict and characterize sensor output should prove helpful in distinguishing between geologic features and man-made underground infrastructure. These modeling results also are expected to facilitate frequency-domain EMI data analysis and interpretation, sensor design and operation, and the development of detection and classification algorithms.