Shaft Horsepower Meter

What is a shaft horsepower meter?

A shaft horsepower meter is an instrument that measures the transmitted horsepower supplied from the engine to the propeller on a vessel by measuring the torsion of the rotating shaft.


The main engine output can be measured from the FO Load Indicator, turbocharger speed, scavenging pressure, and fuel consumption rate. The shaft horsepower meter that can directly measure the main engine horsepower is the most efficient.


By installing a shaft horsepower meter, the vessel's operational status and the operating status of the main engine can be accurately grasped based on horsepower, which increases the safety of the vessel. In addition, by setting the optimal operation schedule based on shaft horsepower meter data, fuel consumption can be reduced and the economics of the ship can be improved.

SEC Shaft Horsepower Meter

SEC shaft horsepower meter installation image
SEC shaft horsepower meter installation image

<Metal strip vibration method

The principle of measurement is a method for detecting shaft torque using the fact that the vibration frequency changes in proportion to the change in tension.

Two sensors are installed between the detection rings mounted on the shaft, and the metal strip stretched inside the sensor changes the distance between the fulcrums due to the torsion of the shaft, increasing the tension between AB and decreasing between AC. The amount of each change is reflected in the natural frequency of the sensor strip.


The distance between the fulcrum of the sensor strip changes due to the torsion of the sensor strip stretched between the two detector rings mounted on the shaft.
        Tension : A-B → Increase  A-C → Decrease
Tension ∝ change amount of A-B (A-C)  ∝ Square Hz

Composition of SEC Shaft Horsepower Meter


SEC shaft horsepower meter consists the detector ring attached to the intermediate shaft, the contactless power supply unit that supplies power to vibrate the metal strip of the torsion sensor and to transmit and receive the sensor signal and the data processing display unit that calculates and displays horsepower and torque from the shaft speed signals and the sensor frequency signals.

The SEC shaft horsepower meter can also be installed on the service vessel. For in-service vessels, installation at the port of call is also available.