SIST ISO 9110-2:2021

SLOVENSKI STANDARD
SIST ISO 9110-2:2021
01-julij-2021
Nadomešča:
SIST ISO 9110-2:1997
Fluidna tehnika - Hidravlika - Merilna tehnika
Hydraulic fluid power -- Measurement techniques
Transmissions hydrauliques -- Techniques de mesurage
Ta slovenski standard je istoveten z: ISO 9110-2:2020
ICS:
23.100.01 Hidravlični sistemi na splošno Fluid power systems in
general
SIST ISO 9110-2:2021 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST ISO 9110-2:2021

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SIST ISO 9110-2:2021
INTERNATIONAL ISO
STANDARD 9110-2
Second edition
2020-05
Hydraulic fluid power — Measurement
techniques —
Part 2:
Measurement of average steady-state
pressure in a closed conduit
Transmissions hydrauliques — Techniques de mesurage —
Partie 2: Mesurage de la pression moyenne dans un conduit fermé en
régime permanent
Reference number
ISO 9110-2:2020(E)
©
ISO 2020

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SIST ISO 9110-2:2021
ISO 9110-2:2020(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2020
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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Published in Switzerland
ii © ISO 2020 – All rights reserved

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SIST ISO 9110-2:2021
ISO 9110-2:2020(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Measuring instrument selection . 1
5 Pressure taps . 3
6 General procedure . 6
7 Total measurement uncertainty . 9
Bibliography .10
© ISO 2020 – All rights reserved iii

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ISO 9110-2:2020(E)

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www .iso .org/
iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 131, Fluid power systems, Subcommittee
SC 8, Product testing.
This second edition cancels and replaces the first edition (ISO 9110-2:1990), which has been technically
revised. The main changes compared to the previous edition are as follows:
— the list of normative references has been revised;
— additional terms and definitions have been added;
— the evaluation of the readability of measuring instruments has been deleted and moved to ISO 9110-1;
— the calibration of working instruments has been deleted and moved to ISO 9110-1;
— the selection and installation of test equipment has been revised and combined and test data
acquisition has been renamed as measuring instrument selection;
— total measurement uncertainty has been added.
A list of all parts in the ISO 9110 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
complete listing of these bodies can be found at www .iso .org/ members .html.
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ISO 9110-2:2020(E)

Introduction
Universal and standardized techniques for the measurement of pressure are required for accurate and
repeatable evaluation of fluid power systems. The purpose of this document is to present recommended
practices for the measurement of average steady-state pressure in hydraulic fluid power systems. This
document is intended for use in conjunction with ISO 9110-1.
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SIST ISO 9110-2:2021
INTERNATIONAL STANDARD ISO 9110-2:2020(E)
Hydraulic fluid power — Measurement techniques —
Part 2:
Measurement of average steady-state pressure in a
closed conduit
1 Scope
This document establishes procedures for measuring the average steady-state pressure in a hydraulic
fluid power conduit.
It is applicable to the measurement of average steady-state pressure in closed conduits with inside
diameters greater than 3 mm, transmitting hydraulic fluid power with average fluid velocities less than
25 m/s and average steady-state static pressures less than 70 MPa.
It is not applicable to sensors which are flush mounted with, or an integral part of, the closed fluid
conduit wall.
It provides the formulae for estimating the total uncertainty in a given pressure measurement.
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 5598, Fluid power systems and components — Vocabulary
ISO 9110-1, Hydraulic fluid power — Measurement techniques — Part 1: General measurement principles
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 5598 and the following 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
tare pressure differential
pressure loss between the pressure tapping points as generated by the test circuit exclusive of the
component under test
4 Measuring instrument selection
4.1 The following subclauses shall be evaluated in accordance with ISO 9110-1.
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4.2 A complete calibration on measuring instruments which have not been previously calibrated shall
be conducted. Gage or absolute pressure instruments are calibrated following established procedures
using a traceable reference standard. The reference standard used shall be recorded.
Differential pressure instruments should be calibrated at the line pressures corresponding to their
application by pressurizing both instrument ports simultaneously. If bidirectional pressures are to be
measured, calibration should encompass both the positive and negative measurement quadrants of the
instrument.
If this is not practical or the differential pressure instrument is subject to varying line pressures in the
measurement situation, include the maximum expected value of the line pressure effect as a standard
uncertainty contributing term in computing the total measurement uncertainty in Clause 7.
Perform an intermediate instrument calibration as required by the measurement class specified.
4.3 Evaluate the readability uncertainty of the readout device to which the measuring instrument is
connected or equipped.
4.4 Each measuring instrument shall be described by an uncertainty model, which is derived from the
calibration results. Evaluate the calibration uncertainty.
4.5 Each measuring instrument shall be supported by calibration records or calibration database and
should have a calibration label attached. See ISO 9110-1:2020, 6.2.12.
4.6 Consider influencing environmental factors in order to minimize their standard uncertainty
contribution. Environmental conditions usually limit the usefulness of instruments because they are
not designed to operate under diverse operating conditions of temperature, vibration or supply voltage
variations, for example. Consider environmental factors carefully since they often are the largest
uncertainty contributors.
With knowledge of the instrument operating environment and the instrument manufacturer’s
specifications, environmental factors can be minimized or evaluated. Either correct for or include the
uncertainty contribution of environmental factors in computing the total measurement uncertainty in
Clause 7.
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ISO 9110-2:2020(E)

5 Pressure taps
5.1 Select and install one of the following types of pressure taps. Types 1 and 2 are constructed in
accordance with Figure 1 and Table 1. The Type 3 tap consists of a construction other than Type 1 or 2.
NOTE Drawing is not to scale.
Figure 1 — Pressure tap hole construction
Table 1 — Pressure tap hole construction
Characteristic Description Requirement
C1 Inside diameter Application Specific
C2 Fluid conductor wall thickness Application Specific
C3 Tap hole diameter C2 / C3 ≥ 1,5
C4 Centre line of tap hole diameter (C4) shall meet conductor
Tap hole centre line
centre line and be normal to it.
C5 Corner radius Corner radius R = 1/8 (C3).
max
C6 Corner break Break sharp edge
More than one pressure tap hole is permitted, but only one may be used in the measurement situation
(not a piezometer ring). The tap hole should not be situated on the lowest point of the fluid conductor
when fluid contamination effects are significant. The fabrication technique used for connecting the
fitting to the fluid conductor is optional provided the geometric requirements of Figure 1 are adhered to.
a) Type 1 – This tap is constructed by drilling a hole into a straight piece of the fluid conductor and
shall be free of all visible burrs.
b) Type 2 –
...