Depending on the ship’s propulsion, noise and vibration mainly originate from motors or turbines and are affected by operational factors such as loading, weather and sea conditions, or maneuvers. Low-noise uniaxial and triaxial accelerometers are used to investigate these phenomena, and waterproof capabilities may also be required to support submersible installations.
Efficient noise and vibration reduction at sea
Mechanical noise and vibrations are investigated with the aim of improving passenger comfort, reliability, durability and silencing. Structural behavior and the many sources of noise and vibration are characterized in order to understand and optimize performance. Engineers rely on pressure sensors, waterproof accelerometers and acoustic emission sensors from Kistler –including IEPE, miniature and low-noise variants – for an efficient noise and vibration reduction at sea.
Exact measurement of propeller performance
Other than the main engine, the propeller is the principal exciter of ship vibrations. To take account of these issues, propeller tests generally include measurements of pressure fluctuation, vibration and sound. Most of these tests are performed on ship models in cavitation tunnels, but testing is also carried out on real vessels in some cases.
Piezoelectric pressure sensors are the solution of choice for measuring very small pressure pulsations (down to a few microbars/1E-5 psi), and they can also cope with high static pressure levels. Vibrations are measured directly on the propeller in order to analyze and compare acoustically optimized propellers.
Flush-mounted pressure pulsation sensors
Highly sensitive flush-mounted piezoelectric pressure sensors (such as the 601C series) are the key to measuring pressure pulsations down to a few microbars. When needed, the option of using IP68 cable solutions must also be available for this application.
Accelerometers with waterproof capability
Accelerometers sometimes need to be mounted inside the tunnel, in direct contact with water. These situations require very small sensors with waterproof capability up to IP68 (qualified to 10 bar). Pressurized water tests are carried out on all waterproof accelerometers from Kistler before they leave our factory.
Acoustic emission measurement capabilities
Frequencies above 20 kHz can be encountered when taking surface acoustic wave measurements during cavitation. Acoustic emission sensors with a frequency range capability of up to 1 MHz are required in these situations.