The Shaft power meter is an instrument for continuous measurements of torque, thrust and revolution on a rotating shaft.
The instrument is primarily designed for marine application. It standards concept consists of two major parts;
1. Display unit (DU)
2. Shaft power sensor (SPS)
The DU handles the data communication with the SPS and presents the calculation data.
Mostly, the DU is installed in the vessel engine room control room console, which serves as main and other displays units can be connected to it as a repeaters on location like wheel house or navigation room. The DU consists of a flat LCD screen module and a processing unit.
Also, the screen module consists of several push buttons for access to various system parameters and functions, brightness and contrast adjustment.
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The SPS device measures shaft torque and thrust using strain gauge technique. The device consists of an aluminium ring clamped onto the shaft, a stationary unit located next to the shaft and a terminal junction box for signal and power connection.
While the shaft ring contains electronic components for signal processing and transmission, as well as a protective means for the strain gauges which are glued onto the shaft surface.
Now, values for torque and thrust are transferable via frequency modulated signals to the stationary unit through contact free transmission. While the shaft rotates, the shaft revolutions are measured by sensing of steel studs on the shaft rings. The value of shaft power and total energy are calculated by the signal processor in the stationary unit.
Without DU, the SPS can also be connected to any system with a serial I/O port, which makes the instrument more unique.
why SPM required onboard ship?
The SPM help reveal the true mechanical horsepower, torque, speed, and thrust on a propulsion shaft. It use spans decades in the marine industries with the technology on thousands of ship globally.
Also, SPM is the key component for measuring ship performance and fuel / propulsion efficiency.
Most of the system is easy to install and requires no electronic parts on the shaft. SPM operates absolutely contact-free and can be extended with fuel performance system FPS to obtain all important data for optimizing ship performance and fuel efficiency as well as ship propulsion performance.
With this technology in place operators can understand when there are high torque acting on the shaft, actual shaft speed and thrust on the shaft.
What is the purpose of having torque meter in ships propeller shaft?
As mentioned on sciencedirect “Propulsion shaft torque measurement is essential in ship energy efficiency evaluation and emission control. Its accuracy and uncertainty influence decision making in terms of voyage optimisation and fuel consumption. For best results, the measuring device should be adjusted and calibrated adequately.”
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