A portable, passive, non‐destructive, non‐intrusive instrument is currently in use by the U.S. Navy to detect fluid leakage through shipboard steam, water, hydraulic, and high‐pressure air valves. The Acoustic Valve Leak Detector (AVLD) was developed by the David W. Taylor Naval Ship RID Center (DTNSRDC) under the financial sponsorship and technical direction of the Nuclear Powered Fleet Ballistic Missile Submarine (SSBN) Ship Systems Maintenance Monitoring and Support Office (SMMSO) of the Naval Ship Engineering Center. The instrument is used to identify more precisely internal leakage points which may require opening and visual inspection of Submarine piping system. “Open‐and‐inspect” routines generate both risk of system damage and high man‐hour expenditure. The degree to which such procedures are necessary to achieve confidence in the material condition of systems is dependent on the availability and performance of non‐intrusive test equipment which can detect and assess the nature and degree of malfunctions. The development, design, operations, limitations, and successful applications of the existing AVLD are described. The AVLD is currently being used for troubleshooting, for overhaul planning, and in a systematic preventive maintenance program for seawater valves. Plans for future development and progress achieved in current work are described. The AVLD listens for the ultrasonic acoustic emissions characteristic of internal valve leakage and uses transducers attached temporarily to the valve or adjacent piping. The background spectra of structureborne noise can be subtracted automatically by the AVLD when a second transducer is attached to the piping system at a point far enough away from the valve in question that it picks up no leakage noise. Since the transducers are attached to the outside of the valves, the time and expense of dismantling the valves or of removing them from the systems are avoided.
Underway replenishment (UNREP) operations have always been a difficult maneuver, and are accomplished by manual control of U.S. Navy ships, using the most experienced personnel. The probability of collision during UNREP increases with decreasing distance between the ships. The David W. Taylor Naval Ship Research and Development Center has recently completed an exploratory development program to define and analyze the control parameters affecting the dynamic interactions between ships during UNREP, resulting in definition of some of the requirements for a prototype ship separation and sensing and control system. The UNREP control problem was simulated on a hybrid computer using analytical models of two identical Mariner-class ships, including consideration of nonlinear maneuvering equations, ship interaction forces and moments, regular waves, severe first-and second-order irregular waves, oblique seaway, time-sampled separation measurements, and low-pass filters. Assumed sensor inputs to the controller were longitudinal and lateral separation, lateral separation rate, relative yaw, relative yaw rate, and rudder angle. Results of the simulation indicate that first-order irregular-wave excitations dominate the UNREP rudder control problem in severe sea states. Use of either automatic or quickened (display-aided) manual control was found to be feasible, but additional work is needed to define the capabilities and limitations of quickening in this application, and to redesign the controller, using modern control theory techniques.
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