MetaPower

Torque and Power Measurement System for Rotating Shafts

MetaPower is a system intended for the measurement of RPM (revolutions per minute), torque and power transferred from the main engine on a ship to the propeller(s). The system does not need strain gauges or any type of delicate electronics glued to, or mounted on the rotating shafts. The system is a digital measuring system using a laser beam for the detection of the shaft torque, the shaft RPM and consequently the transferred power. The MetaPower system offers high accuracy and good long term stability. By transmitting measured data via satellite from ship to shore, the shipping company's operation management is able to decide the most economical operating modes for the ship's engine and propulsion system. Wind turbines, mainly offshore installed turbines with controllable pitch, is another interesting market for the MetaPower system.

The main benefits of the MetaPower system are:

• Continuous, highly accurate measurements
• Reliable and maintenance-free
• Robust construction
• The sensing elements can be installed in hazardous areas
• Suitable for any shaft diameter
• Easy-to-read displays and graphics
• Integration into control and monitoring systems and data networks
• Excellent price/performance ratio
• For shafts rotating at up to 30000 RPM

The MetaPower basic working principle is shown on the figure below.

An IR beam is transmitted through optical fibre (3) from the VCSEL source mounted in the processing unit (8) to a specially designed optical fork (7). The IR beam in the air gaps is pulse modulated by the coding wheels (1) and (2) mounted on the rotating shaft at an adequate distance from each other. The generated pulse pattern will depend on the shaft speed and torque. The resulting IR light signal in the optical fibre (4) contains the information on the torsional angle between the two cuts (1) and (2) of the rotating shaft. In addition, the IR light signal contains the information on the shaft RPM. The IR signal is detected by one single light sensitive sensor in the processing unit (8). The modulated IR pulses are converted to electronic pulses for the further processing.

In this way the following can be measured and read out:

• The RPM of the shaft
• The torsional angle between two cuts of the shaft, i.e., the torque
• The power transferred by the shaft

In certain cases with short shafts or limited space available, an alternative solution may be used. A tube is split in half and fixed to the shaft in the outer ends. At the inner end, two coding wheels are mounted close together on the tubes. A benefit with this method is that only one optical fork is needed.

The measured figures are displayed on analogue instruments, in digital form on an LCD (Liquid Crystal Display) monitor or both analogue and digital on a standard PC monitor.

The MetaPower system is classified by the International Patent Cooperation Treaty to be a novelty, an inventive step and to have industrial applicability. The Intellectual Property Rights to the MetaPower system were granted by patents registered in the most important industry and shipping countries, including USA.

MetaPower on Ships

In July 1999, full scale tests of MetaPower were commenced on board Bergen, Norway based Fjord Line's M/V "Bergen", a passenger and car ferry sailing in a shuttle between Bergen and Hanstholm in Denmark. In October 1999, full scale tests were also initiated on board Solstad Shipping AS' offshore vessel "Normand Progress." This test was carried out in cooperation with, and supported by Rolls-Royce Marine AS dep. Propulsion-Ulstein.

The test programs covered continuous logging and read-out of the propeller shafts' RPM, torque, power and the total energy transferred to the propellers. These logged figures can in turn be compared to the total consumption of fuel in order to optimize the operation of the ship.

Both test programs are completed with excellent results.

The company has through 2001 to 2003 received commercial orders from major players in the maritime industry.

MetaPower has been installed on board a numerous range of different ship types like passenger vessels, tankers, offshore vessels, cargo/container ships and seismic survey vessels. Ships with both one and two shafts/propellers.

MetaPower is on these vessels used for many different purposes like optimizing of ship performance, fuel reduction, NOx reduction and to save maintenance costs by minimize down time. By using MetaPower's additional torsional oscillation analysis, ship owners are able to monitor their propeller shafts and thrusters over periods of time for preventive maintenance and corrective actions.

MetaPower on Wind Turbines

The installations on wind turbines seem to be of considerable commercial interest. Risø National Laboratory, Denmark, and MetaSystems AS have carried out long term tests on a research turbine located at, and owned by Risø National Laboratory. This is a two-shaft installation in order to monitor and log the torque and the power on both the slow running shafts connected to the turbine blades as well as the fast running generator shaft. Nominal power is 500 kW. As the future wind turbines will be equipped with controlled, variable pitch wings, it seems to be of considerable interest to measure the torque continuously for the purpose of being able to optimize the torque automatically. This will give the maximum wind power under all weather conditions.

A report from these tests can be found here

In addition to the data logging at Risø, all measured figures were transmitted to a PC at the MetaSystems AS office in Bergen. There, the office computer was contacted via the ordinary public telephone communication system with Risø. This way the RPM, torque, and power on the two shafts at the Risø research turbine were monitored and logged.