Margaret S. Greenwood

On-line ultrasonic density sensor for process control of liquids and slurries

Abstract An on-line ultrasonic density sensor is described in which six transducers are mounted upon a plastic wedge, the base of the wedge being in contact with a liquid or slurry. Ultrasonic beams striking the base at several angles are reflected. The amount of reflection at the plastic–liquid interface depends upon the density of the liquid ρ, the speed of sound c in the liquid, and wedge parameters. By determining the reflection coefficient at two angles, ρ and c can be determined. The sensor can be mounted in a pipeline configuration or submerged for tank applications.

Ultrasonic sensor to measure the density of a liquid or slurry during pipeline transport

This paper describes the design and testing of a computer-controlled sensor for the real-time measurement of the density of a liquid or slurry. It is to be deployed at the US Department of Energys Hanford Site in Richland, WA, to monitor slurry properties during radioactive waste transfers. To demonstrate the sensor performance, tests were carried out using non-radioactive waste simulants and the results will be presented. The sensor is mounted flush with the pipeline wall in a nominal 5-cm (2-in.) pipe spool piece. The design pressure is 2.8 MPa (400 psi). The probe wedge in contact with the slurry was selected to operate up to pH 14, and the probe components were radiation tested at exposures of 1 x 10(6) R. The sensor is applicable for process control of all types of liquids or slurries in pipelines or in vessels.

Self-Calibrating Sensor for Measuring Density through Stainless Steel Pipeline Wall

An ultrasonic instrument to measure the density of a liquid or slurry [1,2] through the stainless steel (SS) pipeline wall is described. By using multiple reflections of the ultrasound within the SS wall, the acoustic impedance (defined as the product of the density of the liquid and the velocity of sound in the liquid) is determined. Thus, the wall is part of the measurement system. The density is obtained by coupling the acoustic impedance measurement with a velocity of sound measurement. Since methods for measuring the time-of-flight (TOF) are well known, the research presented here will focus on the measurement of the acoustic impedance. The self-calibrating feature is very important because the measurement of the acoustic impedance is independent of changes in the pulser voltage. The objective is to develop an ultrasonic sensor that (1) can be attached permanently to a pipeline wall, possibly as a spool piece inserted into the line and (2) can clamp onto an existing pipeline wall and be movable to another location. The self-calibrating feature is very important because the signal strength is sensitive to the pressure on the clamp-on sensor. A sensor for immersion into a tank could also be developed. A U.S. Patent application has been filed.Copyright

Attenuation measurements of ultrasound in a kaolin–water slurry: A linear dependence upon frequency

The attenuation of ultrasound through a kaolin–water slurry was measured for frequencies ranging from 0.5 to 3.0 MHz. The maximum concentration of the slurry was for a weight percentage of 44% (or a volume fraction of 0.24). The goal of these measurements was to assess the feasibility of using ultrasonic attenuation to determine the concentration of a slurry of known composition. The measurements were obtained by consecutively adding kaolin to the slurry and measuring the attenuation at each concentration. After reaching a maximum concentration a dilution technique was used, in which an amount of slurry was removed and water was added, to obtain the attenuation as a function of the concentration. The dilution technique was the more effective method to obtain calibration data. These measurements were carried out using two transducers, having a center frequency of 2.25 MHz, separated by 0.1016 m (4.0 in.). The maximum attenuation measured in these experiments was about 100 Np/m, but the experimental apparat...

Attenuation of Sound in Concentrated Suspensions: Theory and Experiments

Ensemble-averaged equations are derived for small-amplitude acoustic wave propagation through non-dilute suspensions. The equations are closed by introducing effective properties of the suspension such as the compressibility, density, viscoelasticity, heat capacity, and conductivity. These effective properties are estimated as a function of frequency, particle volume fraction, and physical properties of the individual phases using a self-consistent, effective-medium approximation. The theory is shown to be in excellent agreement with various rigorous analytical results accounting for multiparticle interactions. The theory is also shown to agree well with the experimental data on concentrated suspensions of small polystyrene particles in water obtained by Allegra & Hawley and for glass particles in water obtained in the present study.

On-Line Sensor to Measure the Density of a Liquid or Slurry

An on-line sensor to measure the density of a liquid or slurry is of interest for many different applications, such as measuring the density of a reagent in a pipeline during production or transport or measuring the density of a slurry in a radioactive waste storage tank on the Hanford reservation. Such a real-time, in-situ sensor is shown in Figure 1. The ultrasonic density sensor consists of longitudinal (B, C, D, E, and F) and shear wave (A) transducers mounted upon a plastic wedge. Density is measured based on the reflection of ultrasound at the wedge-liquid interface.

Ultrasonic technologies for advanced process monitoring, measurement, and control

Ultrasonic signals are well suited for characterizing of liquids, slurries, and multiphase flows. Ultrasound sensor systems provide real-time insitu measurements or visualizations, and the sensing systems are compact, rugged, and relatively inexpensive. The objective is to develop ultrasonic sensors that 1) can be attached permanently to a pipeline wall, possibly as a spool piece inserted into the line, and 2) can clamp onto an existing pipeline wall and be movable to another location. Two examples of systems based on pulse-echo and transmission signal analysis are used to illustrate some of the capabilities of ultrasonic online measurements with technologies that have applications in the nuclear, petrochemical, and food processing industries.

Test Loop Demonstration and Evaluation of Slurry Transfer Line Critical Velocity Measurement Instruments

This report presents the results of the evaluation of three ultrasonic sensors for detecting critical velocity during slurry transfer between the Hanford tank farms and the WTP.

Using Ultrasonic Diffraction Grating Spectroscopy to Characterize Fluids and Slurries

In ultrasonic diffraction grating spectroscopy, the grating surface is in contact with the liquid or slurry. The ultrasonic beam, traveling in the solid, strikes the back of the grating and produces a transmitted m = 1 beam in the liquid. The angle of this beam in the liquid changes with frequency and the so‐called critical frequency occurs when the angle is 90°. At this point, the signal of the reflected m = 0 wave—the signal observed in the experiment—increases and this increase is used to characterize the liquid or slurry.

Evolution of a Non-Invasive Sensor for Fluid Density and Solids Concentration Measurement Using Ultrasound

This paper describes the evolution of an ultrasonic sensor to non-invasively measure slurry density and solids concentration. Three generations of probe are discussed: 1) density sensor, 2) densimeter, and 3) fluid and solids monitor. The initial application was to measure slurry density during radioactive waste transport. The probe uses ultrasonic signal reflection at the fluid-pipe wall interface to quantify density in situ in real time and signal attenuation to evaluate solid concentration. In the latest configuration, the transducers are mounted on the wall of the pipe spool piece. This instrument was selected for monitoring radioactive waste transport based on several characteristic features: the sensing surface is non-intrusive and does not disrupt the slurry flow, instrument performance is not affected by slight amounts of entrained air that could be present during waste retrieval and transfer; nor is it affected by electromagnetic noise from nearby pumps and other equipment; and the instrument is compact. The densimeter has been deployed at Hanford tank SY-101 in the prefabricated pump pit process manifold to monitor slurry properties during radioactive waste transfers. To qualify densimeter performance prior to manifold installation in the radioactive pipeline, the probe was installed in the process manifold and performance was evaluated during tests using non-radioactive waste simulants over the density range from 1000 to 1500 kg/m3 . The probe predicted density within ± 2%. The sensor is installed in a nominal 5-cm-diameter (2-in.) pipe spool piece; the design pressure is 2.8 MPa (400 psi). To ensure operability during prolonged contact with radioactive waste, the probe wedge in contact with the slurry was selected to operate up to pH 14, and the probe components were radiation tested at exposures of 1×106 R.Copyright