Abstract: An ultrasonic method and apparatus for measuring liquid level in a vessel employing an acoustic waveguide (16) connected to an ultrasonic transducer (14) and the vessel (18). Guiding means (24) situated inside a vessel (18) directs the acoustic energy pulse to a surface (22) of the liquid. The acoustic energy pulse is reflected from the surface (22) and returned along the guiding means (24) to the acoustic waveguide (16). A pulser/receiver (10) connected thereto measures the reflected acoustic energy pulse for determining liquid level from the transit time.

Abstract: A method and apparatus for detecting the presence of a gaseous substance within a space bounded by an enclosure utilizes the fact that sound is not transmitted through a vacuum and is transmitted through the material of the enclosure. A sonic wave transmitter and a sonic wave receiver are engaged with the material of the enclosure and separated by the space. Using the calculated arrival times and/or amplitudes for the soundwave portions through the space and through the material of the enclosure, it can be determined whether a soundwave portion has passed through the space and thus a leakage of gaseous substance into the space above a threshold amount has taken place.

Abstract: A compensator for differential thermal expansion in a multi-stage barrel type centrifugal pump has a truncated conical body section and a plurality of leaf springs extending radially from said body section, the compensator is disposed in the multi-stage barrel type centrifugal pump between the outer casing and the end most interstage pumping assembly of a plurality of serially disposed interstage pumping assemblies in the centrifugal pump so that it is biased by the leaf springs to exert a controlled force in the direction of the end most interstage pumping assembly to permit movement between the serially disposed interstage pumping assemblies with variations in temperature arising during the operation of the centrifugal pump while continuing to maintain a tight seal between these respective interstage pumping assemblies.