ISO 20083-2:2019

INTERNATIONAL ISO
STANDARD 20083-2
First edition
2019-06
Ships and marine technology —
Determination of the shaft power of
ship propulsion systems by measuring
the shaft distorsion —
Part 2:
Optical reflection method
Reference number
©
ISO 2019
© ISO 2019
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ii © ISO 2019 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principles of the measurement . 2
5 Components of the device . 4
5.1 General . 4
5.2 Mounting rings . 5
5.3 Torsion meter . 5
5.4 Reflecting mirror . 5
5.5 Transmitter . 6
5.6 Receiver and power supply system . 6
5.7 Revolution sensor . 6
6 Calculation of the shaft power . 6
6.1 Shaft torque . 6
6.2 Shaft power . 7
7 Factors for determining the measuring accuracy . 7
7.1 General . 7
7.2 Shaft diameter . 7
7.3 G-modulus . 7
7.4 Distance between mounting rings . 7
7.5 Thickness of the mounting ring . 7
7.6 Vibration of the shaft . 7
7.7 Zero adjustment . 8
7.7.1 Zero point . 8
7.7.2 Procedure for zero adjustment. 8
7.8 Calibration . 8
7.8.1 General. 8
7.8.2 Calibration procedure . 8
8 On-board documentation for the device . 8
Annex A (informative) Sample form of calibration results . 9
Bibliography .10
Foreword
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electrotechnical standardization.
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This document was prepared by Technical Committee ISO/TC 8, Ships and marine technology,
Subcommittee SC 2, Marine environment protection.
A list of all parts in the ISO 20083 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
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iv © ISO 2019 – All rights reserved

Introduction
Selecting the optimum rating of a ship’s main engine is important for ship owners, because it greatly
affects the expenses of operations, maintenance and management as well as the ship’s construction cost.
Measuring the output of the ship’s main engine is important for confirming the ship efficiency, as well
as for assessing the possible deterioration of the propulsion equipment or the accumulation of fouling
on the hull over time. There are many methods of measuring an engine’s output: (1) measuring the
distortion of the shaft, (2) determining the fuel consumption, and (3) observing engine indicators such
as cylinder pressure gauges.
Among these methods, ISO 20083 addresses the shaft distortion measurement with a shaft power
meter, a method commonly used as the principal measurement of engine power output.
The purposes of shaft power measurement are:
— to provide a measurement of the ship’s main engine output,
— to provide information regarding the ship’s most efficient speed,
— to select optimum engine operational characteristics,
— to estimate maintenance and repair costs, and
— to monitor heavy propeller running.
INTERNATIONAL STANDARD ISO 20083-2:2019(E)
Ships and marine technology — Determination of the shaft
power of ship propulsion systems by measuring the shaft
distorsion —
Part 2:
Optical reflection method
1 Scope
This document specifies a procedure to determine the shaft power of engine ships, by measuring the
shaft distortion using an optical reflection type device. It gives the principles of the measurement, the
components of the device and the calculation method. It also describes the factors for determining the
measuring accuracy, including the calibration procedure, and specifies the on-board documentation for
the device.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/s
3.1
shaft
propeller shaft or intermediate shaft that transmits the engine power to the propeller, and on which the
shaft power meter is installed
3.2
shaft torque
Q
turning moment transmitted to the shaft that is generated by the engine to rotate the propeller
Note 1 to entry: It is expressed in newton meters.
3.3
shaft power
P
s
power transmitted to the shaft that is generated by the engine to rotate the propeller
Note 1 to entry: It is expressed in kilowatts.
4 Principles of the measurement
The shaft power meter is a device that measures the shaft revolution and the torsional deformation of
the shaft caused by the shaft torque. The shaft power, P [kW], is calculated using Formula (1):
s
2⋅⋅π NQ⋅ 1
P = × (1)
s
where
-1
N is the rate of shaft revolutions per minute [min ];
Q is the shaft torque [Nm].
The shaft torque, Q [Nm], is calculated from the torsional deformation angle rate at unit length of the
shaft using Formula (2):
G⋅⋅I θ′
p
Q = (2)
where
G is the G-modulus [N/mm ];
I is the polar moment of inertia [mm ];
p
θ′ is the shaft torsional deformation angle rate at unit length [1/mm].
The polar moment of inertia, I [mm ], is calculated using Formula (3):
p
π
ID=− D (3)
po()i
where
D is the outer diameter of the shaft [mm];
o
D is the inner diameter of the hollow shaft [mm].
i
The shaft torsional deformation angle rate at unit length, ϴ′ [1/mm], is calculated using Formula (4):
θ
θ′= (4)
l
where
θ is the shaft torsional deformation angle [rad] as shown in Figure 1;
l is the length between the shaft rings [mm].
2 © ISO 2019 – All rights reserved

The torsional deformation angle, ϴ [rad], can be calculated from the displacement of the detecting point
measured by the torsion meter as given in Formula (5):
δ
θ = (5)
r
where
δ is the displacement of the detecting point [mm];
r is the distance of the detecting point from the shaft center line [mm].
Key
1 center line of the shaft
θ shaft torsional deformation angle [rad]
l length between rings [mm]
δ displacement of the detecting point [mm]
r distance of the detecting point from the shaft center line [mm]
Figure 1 — Torsional deformation angle of a shaft
Th
...