Abstract: A method and apparatus for detecting perforations in an underground fuel storage tank, employs the creation of a partial vacuum in the tank and a pressure difference across the tank wall, to cause air to pass through the perforation, and a hydrophone to sense the acoustic waves produced by the formation of air bubbles in the fuel. The acoustic waves of the bubbles caused by the air passage are sensed by a hydrophone and processed to provide an electrical signal indicative of the presence of the perforation. A water level sensor is also used to detect the level of water beneath hydrocarbon fuel in the tank. The method and apparatus can also be used with above ground fuel storage tanks and other types of above and below ground storage tanks.

Abstract: This is an electronic device which determines the fatigue life of a structure and its crack growth characteristics when subjected to repeated loading by using the signal from an electrical resistance type strain gage secured to the structure to provide the input to a processor which monitors cyclic excursions, calculates the fatigue and fracture structural damage from those excursions, stores the cumulative damage, and displays that damage on command.