ISO 23048:2018

INTERNATIONAL ISO
STANDARD 23048
First edition
2018-07
Ships and marine technology —
Verification method for portable power
measurement using a strain gauge
Titre manque
Reference number
©
ISO 2018
© ISO 2018
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ii © ISO 2018 – All rights reserved

Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Composition of the shaft power meter verification equipment . 2
4.1 General . 2
4.2 Torque generator and RPM generator .2
4.2.1 General. 2
4.2.2 Torque generator.2
4.2.3 RPM generator.2
5 Guidelines for installation and verification test . 3
5.1 General . 3
5.2 Installation guidelines .4
6 Test procedure . 5
7 Test report . 5
8 Verification . 5
Annex A (normative) Installation and verification method — Strain gauge . 6
Annex B (informative) Shaft power measurement — Strain gauge (portable type) . 9
Annex C (normative) Verification test report for shaft power meter (strain gauge) .14
Bibliography .15
Foreword
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This document was prepared by Technical Committee ISO/TC 8, Ships and marine technology,
Subcommittee SC 2, Marine environment protection.
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iv © ISO 2018 – All rights reserved

INTERNATIONAL STANDARD ISO 23048:2018(E)
Ships and marine technology — Verification method for
portable power measurement using a strain gauge
1 Scope
This document specifies a procedure for the verification of portable power measurement equipment
using a strain gauge in the laboratory.
The power measurement equipment verified in accordance with this document can be used on
merchant ships.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 15016:2015, Ships and marine technology — Guidelines for the assessment of speed and power
performance by analysis of speed trial data
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/
3.1
strain gauge
gauge used to measure the strain on an object
Note 1 to entry: As the object is deformed it causes a change in electrical resistance. This change in resistance,
usually measured using a Wheatstone bridge, is related to the strain by the quantity known as the gauge factor.
3.2
shaft power meter verification equipment
equipment designed to provide a real torque, produced by a torque arm weighted with a known exact
mass, to the torque measurement device
3.3
portable power measurement equipment
equipment temporarily installed on the ship and operated during a sea trial to measure the power
delivered to the propeller by the engine and transmission systems, as opposed to the fixed-type shaft
power measurement equipment, if installed
4 Composition of the shaft power meter verification equipment
4.1 General
The verification equipment is composed of a torque arm, a weight surface plate, a torque arm axis, a
shaft, a torque sensor, a weight and an RPM (revolutions per minute) generator. See Figure 1. The real
torque is generated by weights with known exact mass, attached to a torque arm of known length which
is attached to the shaft.
Shaft torque shall be measured by means of a verified permanent torque sensor or strain gauges on
the shaft.
4.2 Torque generator and RPM generator
4.2.1 General
Torque and RPM are needed for calculating the shaft power output. The ship’s power output can be
simulated by multiplying the RPM, which are generated by an RPM generator, generating exact RPM,
and the torque which is generated by a torque generator.
4.2.2 Torque generator
Torque is applied to the shaft by a torque generator using weights with exact mass and a torque arm
with exact length, see Figure 2. Weight shall be corrected and calibrated accurately.
The shaft material properties of the torque generator shall be stated in a test report in accordance with
ISO 15016:2015, 6.1.
4.2.3 RPM generator
a) The RPM generator is composed of a body of revolution, which can be controlled from 0 RPM to
1 RPM, and a tacho sensor which measures the number of revolutions.
b) The RPM generator shall control the RPM precisely. It shall be designed to attach to the various
types of tacho sensors to be linked with the shaft power device.
c) The RPM generator shall be capable of displaying the current RPM status data. The RPM error rate
shall be recorded in the test report as specified in Annex C.
d) The RPM generator should be calibrated by a facility meeting ISO/IEC 17025. If it is not, it should be
verified by a calibrated tachometer.
e) The engine RPM generator shall be included for exact verification of the shaft power meter as
shown in Figure 1.
f) The RPM error rate shall be measured at least five times for each of the RPM testing conditions.
2 © ISO 2018 – All rights reserved

Key
1 motor precise control system
2 precise servo meter
3 rotating shaft
4 tachometer
5 shaft power verification simulator (SW)
6 control and data processing unit
7 torque arm
8 torque
9 weight
10 moment
Figure 1 — Composition of the verification equipment
5 Guidelines for installation and verification test
5.1 General
The verification equipment shall be designed to enable a comparison with the output of the portable
shaft power meter by generating torque and RPM.
When the weights are installed to the torque arm, the specimen shaft is twisted by the torque and this
torque is measured by the shaft power verification equipment.
The torque can be verified by a torque arm weighted with a known exact mass and exact length. The
shaft power meter can be verified by comparing the output values with the verification equipment. It is
possible to verify whether the torque output measured by the torque sensor is equal to the calculated
values or not.
Measured values of the verification equipment torque sensor are the standard values.
Final power (kW) of the shaft power meter for the ship’s engine can be verified when RPM data is
provided by the RPM generator.
NOTE The verification equipment is designed for the portable torque meter; however, this equipment can
verify other types of shaft power meters by agreement between manufacturers and purchasers.
5.2 Installation guidelines
The verification equipment can be designed as given in Table 1, however other types of equipment
designs can be applied by agreement between manufacturers and purchasers, see Annex B.
Table 1 — Installation guidelines
Name Use Guidelines
Comparing and analysing the output values installed in
Sensor to measure torque
Torque sensor the test shaft and suggesting the standard value allows
values at specimen shaft
verification of the shaft power meter.
4.2.2 shall be followed for the shaft property of the
Shaft Shaft for verification test
shear modules.
Distance between rotation pivot point of torque arm
Mechanism for transferring
and acting point of weighting shall be 1 m for the sake
Torque arm the torque moment by weight
of convenient calculation of moment of rotation and
to the test specimen shaft
torsional rigidity.
Device for generating artifi- Predictable standard torque is generated by weight
Weight
cial torque with exact mass.
It shall be designed to equip the tacho sensor of shaft
RPM generator Device for generating RPM
power equipment and precisely control the RPM.
4 © ISO 2018 – All rights reserved

Key
1 shaft
2 shaft angle of distortion sensor
3 torque arm
4 weight surface plate
Figure 2 — Torque generator
6 Test procedure
a) Install the shaft power meter to the shaft of the verification equipment in accordance with A.2.
b) Test the strain gauge to ensure it is attached correctly in accordance with A.2 d).
c) Put weight in surface plate and generate torque.
d) Compare the installed shaft power meter values and the shaft power values by the verification
equipment, and record the error rate of these compared values.
e) Compare the number of revolutions generated by the RPM generator and measured output data
and calibrated tachometer and record the error rate of these compared values.
7 Test report
The results of the verification test shall be reported in the form specified in Annex C.
8 Verification
If the torque given by the torque generator is correctly indicated, the power measurement equipment is
deemed to have correct performance of shaft power measurement.
...