Design of ultrasonic attenuation sensor with focused transmitter for density measurements of a slurry in a large steel pipeline.

To design an ultrasonic sensor to measure the attenuation and density of slurry carried by a large steel pipeline (diameter up to 70 cm) is the goal of this research. The pitch-catch attenuation sensor, placed in a small section of the pipeline, contains a send unit with a focused transducer that focuses the ultrasound to a small region of the receive unit on the opposite wall. The focused transducer consists of a section of a sphere (base ∼12 cm) on the outer side of the send unit and a 500 kHz piezoelectric shell of lead zirconate titanate epoxied to it. The Rayleigh surface integral is used to calculate the pressure in steel and in water (slurry). An incremental method to plot the paths of ultrasonic rays shows that the rays focus where expected. Further, there is a region where the parallel rays are perpendicular to the wall of the receive unit. Designs for pipeline diameters of 25 and 71 cm show that the pressure in water at the receive transducer is about 17 times that for a pitch-catch system using 5 cm diameter disk transducers. The enhanced signal increases the sensitivity of the measurements and improves the signal-to-noise ratio.