ISO 10790:2015

Measurement of fluid flow in closed conduits - Guidance to the selection, installation and use of Coriolis flowmeters (mass flow, density and volume flow measurements)

ISO 10790:2015 gives guidelines for the selection, installation, calibration, performance, and operation of Coriolis flowmeters for the measurement of mass flow and density. This International Standard also gives appropriate considerations regarding the type of fluids measured, as well as guidance in the determination of volume flow and other related fluid parameters. NOTE Fluids defined as air, natural gas, water, oil, LPG, LNG, manufactured gases, mixtures, slurries, etc.

Mesure de débit des fluides dans les conduites fermées — Lignes directrices pour la sélection, l'installation et l'utilisation des mesureurs à effet Coriolis (mesurages de débit-masse, masse volumique et débit-volume)

General Information

• Status: Published
• Publication Date: 01-Apr-2015
• ICS: 17.120.10 - Flow in closed conduits
• Technical Committee: ISO/TC 30/SC 5 - Velocity and mass methods
• Drafting Committee: ISO/TC 30/SC 5 - Velocity and mass methods
• Current Stage: 9020 - International Standard under periodical review
• Start Date: 15-Oct-2025
• Completion Date: 15-Oct-2025

Relations

• Revises: ISO 10790:1999/Amd 1:2003 - Measurement of fluid flow in closed conduits - Guidance to the selection, installation and use of Coriolis meters (mass flow, density and volume flow measurements) - Amendment 1: Guidelines for gas measurement
• Effective Date: 02-Oct-2010
• Revises: ISO 10790:1999 - Measurement of fluid flow in closed conduits - Guidance to the selection, installation and use of Coriolis meters (mass flow, density and volume flow measurements)
• Effective Date: 02-Oct-2010

Overview

ISO 10790:2015 provides international guidance for the selection, installation, calibration, performance and operation of Coriolis flowmeters used to measure mass flow, density and derived volume flow in closed conduits. It covers practical considerations for a wide range of fluids (air, natural gas, water, oil, LPG, LNG, manufactured gases, mixtures, slurries, etc.), diagnostic and safety issues, and methods for determining uncertainty and field or factory calibration.

Key Topics

• Selection criteria: guidance on choosing a Coriolis flowmeter based on fluid type, process conditions and measurement objectives.
• Physical installation: orientation, full-pipe requirements for liquids, straight-length and valve considerations, cleaning and pipe stress/torsion issues.
• Process influences: effects of multiphase flow, temperature, pressure, viscosity, pulsation, flashing/cavitation on meter performance.
• Transmitter and diagnostics: requirements for secondary devices (transmitters), diagnostic functions and zero adjustments.
• Measurement methods: principles and apparatus for mass flow and density measurements, and conversion to volume flow at metering conditions.
• Calibration & uncertainty: factory calibration, field calibration techniques, density calibration, and guidance on quantifying measurement uncertainty.
• Safety & integrity: hydrostatic testing, mechanical stress, erosion/corrosion considerations, housing design and cleaning.
• Special topics/annexes: calibration techniques, safety guidelines, considerations for multi-component liquid systems and miscible liquids.

Applications and Who Uses This Standard

ISO 10790:2015 is practical for professionals who design, operate or verify flow measurement systems, including:

• Instrumentation and process engineers specifying Coriolis meters for custody transfer, batching or process control
• Calibration laboratories and metrology professionals performing factory and field calibrations
• Plant operators in oil & gas, chemical, petrochemical, water treatment, food & beverage and bulk liquid handling
• Equipment manufacturers and integrators developing meter installations, transmitters or diagnostic software

Using ISO 10790 helps ensure reliable mass flow, density, and volume flow measurements, reduced measurement uncertainty, and safer installations across diverse fluid applications.

Related Standards

• ISO/IEC Guide 99 (JCGM:2012) / VIM references for measurement terminology and metrology concepts (referenced in ISO 10790).
• Industry flow-measurement standards and local legal metrology requirements (consult specific regional or industry documents when implementing ISO 10790).

Keywords: ISO 10790:2015, Coriolis flowmeter, mass flow measurement, density measurement, volume flow, flowmeter selection, calibration, installation guidance.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 10790
Third edition
2015-04-01
Measurement of fluid flow in closed
conduits — Guidance to the selection,
installation and use of Coriolis
flowmeters (mass flow, density and
volume flow measurements)
Mesure de débit des fluides dans les conduites fermées — Lignes
directrices pour la sélection, l’installation et l’utilisation des
mesureurs à effet Coriolis (mesurages de débit-masse, masse
volumique et débit-volume)
Reference number
©
ISO 2015
© ISO 2015
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail [e-mail]
Web www.iso.org
Published in Switzerland
ii © ISO 2015 – All rights reserved

Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
3.1 Definitions specific to this Coriolis flowmeter standard . 1
3.2 Definitions from VIM, ISO/IEC Guide 99 (JCGM:2012) . 3
3.3 Symbols . 4
3.4 Abbrevations . 5
4 Coriolis flowmeter selection criteria . 5
4.1 General . 5
4.2 Physical installation . 5
4.2.1 General. 5
4.2.2 Installation criteria . 6
4.2.3 Full-pipe requirement for liquids . 6
4.2.4 Orientation . 6
4.2.5 Flow conditions and straight length requirements . 6
4.2.6 Valves . 6
4.2.7 Cleaning . 6
4.2.8 Hydraulic and mechanical vibrations . 7
4.2.9 Pipe stress and torsion . 7
4.2.10 Crosstalk between sensors . 7
4.3 Effects due to process conditions and fluid properties . 7
4.3.1 General. 7
4.3.2 Application and fluid properties . 7
4.3.3 Multiphase flow . 8
4.3.4 Influence of process fluid . 8
4.3.5 Temperature effects . 8
4.3.6 Pressure effects . 9
4.3.7 Pulsating flow effects . 9
4.3.8 Viscosity effects . 9
4.3.9 Flashing and/or cavitation . 9
4.4 Pressure loss . 9
4.5 Safety . 9
4.5.1 General. 9
4.5.2 Hydrostatic pressure test . 9
4.5.3 Mechanical stress .10
4.5.4 Erosion.10
4.5.5 Corrosion .10
4.5.6 Housing design .10
4.5.7 Cleaning .10
4.6 Transmitter (secondary device) .10
4.7 Diagnostics .11
5 Inspection and compliance .11
6 Mass flow measurement .12
6.1 Apparatus .12
6.1.1 Principle of operation .12
6.1.2 Coriolis sensor .14
6.1.3 Coriolis transmitter .15
6.2 Mass flow measurement .15
6.3 Factors affecting mass flow measurement.17
6.3.1 Density and viscosity .17
6.3.2 Multiphase flow .17
6.3.3 Temperature .18
6.3.4 Pressure .18
6.3.5 Installation .18
6.4 Zero adjustment .18
6.5 Calibration of mass flow measurement .18
7 Density measurement .19
7.1 General .19
7.2 Principle of operation .20
7.3 Specific gravity of fluids .21
7.4 Density measurement uncertainty .21
7.5 Factors affecting density measurement .21
7.5.1 Temperature .21
7.5.2 Pressure .22
7.5.3 Multiphase (Two phase).22
7.5.4 Flow effect .22
7.5.5 Corrosion and erosion . .22
7.5.6 Coatings .22
7.5.7 Installation .22
7.6 Density calibration and adjustment .22
7.6.1 General.22
7.6.2 Manufacturer’s density calibration .22
7.6.3 Field density calibration and adjustment.23
8 Volume flow measurement at metering conditions .23
8.1 General .23
8.2 Volume calculation .23
8.3 Gas as a process fluid .24
8.4 Volume measurement uncertainty .24
8.5 Special influences .24
8.5.1 General.24
8.5.2 Empty pipe effect .24
8.5.3 Multiphase fluids .24
8.6 Factory calibration .24
8.6.1 Mass flow and density .24
8.7 Volume check .25
Annex A (informative) Calibration techniques .26
Annex B (informative) Safety guidelines for the selection of Coriolis flowmeters .29
Annex C (informative) Considerations for multi-component liquid systems .31
Annex D (informative) Miscible liquids containing chemically non-interacting components .34
Bibliography .37
iv © ISO 2015 – All rights reserved

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 on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical Barriers
to Trade (TBT), see the following URL: Foreword — Supplementary information.
The committee responsible for this document is ISO/TC 30, Measurement of fluid flow in closed conduits,
Subcommittee SC 5, Velocity and mass methods.
This third edition cancels and replaces the second edition (ISO 10790:1999), which has been technically
revised. It also incorporates the Amendment ISO 10790:1999/Amd 1:2003.
Introduction
This International Standard has been prepared as a guide for those concerned with the selection, testing,
inspection, operation, and calibration of Coriolis flowmeters (Coriolis flowmeter assemblies). A list of
related International Standards is in the Bibliography.
This International Standard provides the following:
a) description of the Coriolis operating principle;
b) guideline to expected performance characteristics of Coriolis flowmeters;
c) description of calibration, verification, and checking procedures;
d) description of potential error sources;
e) common set of terminology, symbols, definitions, and specifications.
The next paragraphs contain an explanation of when to use the measurement terminology, uncertainty,
and accuracy.
The VIM definition (see 3.2) of accuracy: closeness of agreement between a measured quantity value
and a “true quantity value” of a measurand. Per the VIM, accuracy is a quality and should not be given a
numerical value.
To understand the preceding paragraph, one needs to understand that a “true quantity value” does
not exist. The best that can be done is to determine the measured quantity value with measurement
instrumentation calibrated with a very good but imperfect reference. Therefore, the measurement is an
estimate. Uncertainty is used to define these measurement estimates (see 3.2.2).
Many Coriolis manufacturers use accuracy and zero stability as part of their published performance
specifications. The manufacturer’s accuracy specification includes repeatability, hysteresis, and
linearity but can also include other items that might be different for each manufacturer.
This International Standard will use uncertainty to quantify the results of a flow measurement system.
This International Standard will only use accuracy when it is very clear that it is referring to or using all
or part of the manufacturers published specifications.
vi © ISO 2015 – All rights reserved

INTERNATIONAL STANDARD ISO 10790:2015(E)
Measurement of fluid flow in closed conduits — Guidance
to the selection, installation and use of Coriolis flowmeters
(mass flow, density and volume flow measurements)
1 Scope
This International Standard gives guidelines for the selection, installation, calibration, performance,
and operation of Coriolis flowmeters for the measurement of mass flow and density. This International
Standard also gives appropriate considerations regarding the type of fluids measured, as well as
guidance in the determination of volume flow and other related fluid parameters.
NOTE Fluids defined as air, natural gas, water, oil, LPG, LNG, manufactured gases, mixtures, slurries, etc.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 5168, Measurement of fluid flow — Procedures for the evaluation of uncertainties
ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories
ISO/IEC Guide 99:2007 (JCGM 200:2012), International vocabulary of metrology — Basic and general
concepts and associated terms (VIM)
3 Terms and definitions
3.1 Definitions specific to this Coriolis flowmeter standard
For the purposes of this document, the following terms and definitions apply.
3.1.1
Coriolis flowmeter
device consisting of a flow sensor (primary device) and a transmitter (secondary device) which measures
mass flow and density by means of the interaction between a flowing fluid and the oscillation of a tube
or tubes
Note 1 to entry: This can also provide measurement of the tube(s) temperature.
3.1.2
flow sensor (primary device)
mechanical assembly consisting of an oscillating tube(s), drive system, measurement sensor(s),
supporting structure, and housing
3.1.3
transmitter (secondary device)
electronic control system providing the drive electrical supply and transforming the signals from the
flow sensor to give output(s) of measured and inferred parameters
Note 1 to entry: It also provides corrections derived from parameters such as temperature.
Note 2 to entry: The transmitter (secondary device) is either integrally mounted (compact device) on the flow
sensor (primary device) or remotely installed away from the primary device and connected by a cable.
3.1.4
oscillating tube
tube through which the fluid to be measured flows
3.1.5
drive system
means for inducing the oscillation of the tube(s)
3.1.6
sensing device
sensor to detect the effect of the Coriolis force and to measure the frequency of the tube oscillations
3.1.7
supporting structure
support for the oscillating tube(s)
3.1.8
housing
environmental protection of the flow sensor and/or transmitter
3.1.9
secondary containment
housing designed to provide protection to the environment in the event of tube failure
3.1.10
calibrating factor
numerical factor unique to each sensor derived during sensor calibration
Note 1 to entry: The calibrating factor is programmed into the transmitter to enable flowmeter operation.
3.1.11
zero offset
indicated flow when there are zero flow conditions present at the meter
Note 1 to entry: This could be due to mechanical or electrical noise superimposed on the sensor output but equally
could be due to installation effects such as torsional loading caused by improper torqueing of the flange bolts or
temperature extremes creating deflection of the pipeline.
3.1.12
zero stability
variation of the flowmeter output at zero flow after the zero adjustment procedure has been completed,
expressed by the manufacturer as an absolute value in mass per unit time
3.1.13
flashing
phenomenon, which occurs when the line pressure drops to, or below, the vapour pressure of the liquid
Note 1 to entry: This is often due to pressure drops caused by an increase in liquid velocity.
Note 2 to entry: Flashing is not applicable to gases.
3.1.14
cavitation
phenomenon related to and following flashing of liquids if the pressure recovers causing the vapour
bubbles to collapse (implode)
3.1.15
flow rate
quotient of the quantity of fluid passing through the cross-section of the conduit and the time taken for
this quantity to pass through this section
2 © ISO 2015 – All rights reserved

3.1.16
mass flow rate
flow rate in which the quantity of fluid is expressed as mass
3.1.17
volume flow rate
flow rate in which the quantity of fluid is expressed as volume
3.2 Definitions from VIM, ISO/IEC Guide 99 (JCGM:2012)
3.2.1
repeatability (condition of measurement)
condition of measurement, out of a set of conditions that includes the same measurement procedure,
same operators, same measuring system, same operating conditions, and same location, and replicate
measurements on the same or similar objects over a short period of time
Note 1 to entry: A condition of measurement is a repeatability condition only with respect to a specified set of
repeatability conditions environmental protection of the flow sensor and/or transmitter.
3.2.2
measurement uncertainty
non-negative parameter characterizing the dispersion of the quantity values being attributed to a
measurand, based on the information used
Note 1 to entry: Measurement uncertainty includes components arising from systematic effects, such as
components associated with corrections and the assigned quantity values of measurement standards, as well as
the definitional uncertainty. Sometimes estimated systematic effects are not corrected for but, instead, associated
measurement uncertainty components are incorporated.
Note 2 to entry: Measurement uncertainty comprises, in general, many components. Some of these can be evaluated
by Type A evaluation of measurement uncertainty from the statistical distribution of the quantity values from
series of measurements and can be characterized by standard deviations. The other components, which can be
evaluated by Type B evaluation of measurement uncertainty, can also be characterized by standard deviations,
evaluated from probability density functions based on experience or other information.
3.2.3
error
measured quantity value minus a reference quantity value
Note 1 to entry: The concept of “measurement error” can be used both a) when there is a single reference quantity
value to refer to, which occurs if a calibration is made by means of a measurement standard with a measured
quantity value having a negligible measurement uncertainty or if a conventional quantity value is given, in which
case the measurement error is known, and b) if a measurand is supposed to be represented by a unique true
quantity value or a set of true quantity values of negligible range, in which case the measurement error is not
known.
3.2.4
calibration
operation that, under specified conditions, in a first step, establishes a relation between the quantity
values with measurement uncertainties provided by measurement standards and corresponding
indications with associated measurement uncertainties and, in a second step, uses this information to
establish a relation for obtaining a measurement result from an indication
Note 1 to entry: A calibration can be expressed by a statement, calibration function, calibration diagram,
calibration curve, or calibration table. In some cases, it can consist of an additive or multiplicative correction of
the indication with associated measurement uncertainty.
Note 2 to entry: Calibration should not be confused with adjustment of a measuring system, often mistakenly
called “self-calibration”, nor with verification calibration.
3.3 Symbols
Table 1 — Symbols used in this International Standard
Symbol Description Dimensions SI Units
2 2
A oscillating tube internal cross-sectional area L m
id
−2 2
a radial acceleration LT m/s
r
−2 2
a transverse acceleration LT m/s
t
−1
V velocity LT m/s
δm delta mass of a flowing particle M kg
f
δm mass of tube element M kg
tb
−2 2
δF delta Coriolis force MLT m⋅kg/s
C
−1
q mass flow rate MT kg/s
m
−3 3
ρ density ML kg/m
−3 3
ρ density of the fluid ML kg/m
f
−3 3
ρ density of reference liquid ML kg/m
ref
tb tube dim-less —
−2 2
F resultant Coriolis force in the inlet MLT m⋅kg/s
C,Inlet
−2 2
F resultant Coriolis force in the outlet MLT m⋅kg/s
C,Outlet
−2 2
F Coriolis force MLT m⋅kg/s
C
−1 −2
sin sinusoidal function (displacement, velocity, or accelera- L, LT , or LT m, m/s, or m/
D
tion) s
−1 −2
sin sinusoidal function (displacement, velocity, or accelera- L, LT , or LT m, m/s, or m/
A
tion) s
−1 −2
sin sinusoidal function (displacement, velocity, or accelera- L, LT , or LT m, m/s, or m/
B
tion) s
t time delay T s
d
-1
K a constant, primary flow calibration factor at reference MT kg/s/s
R
conditions
−1
ω angular velocity T rad/s
r length L m
δx delta length L m
f resonant frequency T Hz
rf
−2 2
C mechanical stiffness MT kg/s
m mass M kg
−1
M total mass – over a period of time MT kg/s
m mass of oscillating tube(s) M kg
tb
m mass of fluid within the oscillating tube(s) M kg
f
3 3
V volume of fluid within the oscillating tube(s) L m
f
3 −1 3
V total volume – over a period of time L T m /s
K , K density calibration factors dim-less —
1 2
T is the period of the oscillating tube T s
rf
N number of cycles dim-less —
c
t is the time window (gate) T s
w
−3 3
ρ the density of water at reference conditions ML kg/m
ref
4 © ISO 2015 – All rights reserved

Symbol Description Dimensions SI Units
U expected uncertainty of the flow measurement volume percent of reading —
v
U expected uncertainty of the mass flow measurement percent of reading —
m
U expected uncertainty of the density measurement percent of reading —
ρ
w mass fraction of component A dim-less —
A
w mass fraction of component B dim–less —
B
φ volume fraction of component A dim-less —
A
φ volume fraction of component B dim-less —
B
−3 3
ρ density of component A ML kg/m
A
−3 3
ρ density of component B ML kg/m
B
−3 3
ρ density of measured mixture density ML kg/m
ms
−1
q mass flow rate of component A MT kg/s
mA
−1
q mass flow rate of component B MT kg/s
mB
−1
q total mass flow rate of the mixture MT kg/s
mT
3 −1 3
q volume flow rate of component A L T m /s
vA
3 −1 3
q volume flow rate of component B L T m /s
vB
3 −1
q total volume flow rate of the mixture L T m3/s
vT
3.4 Abbrevations
Table 2 — Abbreviations used in this International Standard
Abbreviations Descriptions
cP centipoise (dynamic viscosity) 1 cP = 1 mPa·s
cSt CentiStokes (kinematic viscosity) 1 cSt = 1 mm /s
cP/SG viscosity used in petroleum industry
DN European piping size (diameter nominal, millimetres)
SG specific gravity
SIP steaming-in-place
CIP cleaning-in-place
4 Coriolis flowmeter selection criteria
4.1 General
The Coriolis flowmeter should be selected to measure the user’s parameters within their required
ranges and uncertainty. Consideration should be given to the following points when selecting a Coriolis
flowmeter.
Coriolis flowmeters are not generic devices. The potential user should review the manufacturer’s data
sheet(s) carefully.
4.2 Physical installation
4.2.1 General
The manufacturer should describe the recommended installation arrangement and state any restrictions
of use.
The installation arrangement design enables measurement to meet the user’s requirements. Installation
for liquid and gas measurement can be different. Some applications might need strainers or filters, and
other applications might need air and/or vapour eliminators.
Coriolis flowmeters are regularly placed in the mainstream of the flow but can also be placed in a by-
pass arrangement for density measurements.
4.2.2 Installation criteria
Consider the following, noting that there might be differences for liquid and gas measurement
applications:
a) the space required for the Coriolis flowmeter installation, including provision for external prover or
master-meter connections, should in situ calibration be required;
b) the class and type of pipe connections and materials, as well as the dimensions of the equipment to
be used;
c) the hazardous area classification;
d) the environmental effects on the sensor, for instance, temperature, humidity, corrosive atmospheres,
mechanical shock, vibration, and electromagnetic field;
e) the mounting and support requirements.
4.2.3 Full-pipe requirement for liquids
The primary device should be mounted such that the oscillating tube(s) fill completely with the liquid
being metered; this prevents the measuring performance of the instrument from being impaired.
The manufacturer should state the means, if any, required to purge or drain gases or liquids from the
instrument.
4.2.4 Orientation
Plugging, coating, trapped gas, trapped liquid, or settlement of solids can affect the flowmeter’s
performance. The orientation of the sensor depends on the intended application of the flowmeter and the
geometry of the oscillating tube(s). The orientation of the Coriolis flowmeter should be recommended
by the manufacturer.
4.2.5 Flow conditions and straight length requirements
The performance of a Coriolis flowmeter in single phase flow is usually not affected by swirling fluid or
non-uniform velocity profiles induced by upstream or downstream-piping configurations.
4.2.6 Valves
Valves upstream and downstream to a Coriolis flowmeter, installed for the purpose of isolation and zero
adjustment, can be of any type, but should provide tight shutoff. Control valves in series with a Coriolis
flowmeter should be installed downstream to maintain the pressure required to ensure the product
remains single phase and no flashing or cavitation can occur.
4.2.7 Cleaning
For certain applications (for instance hygienic services), the Coriolis flowmeter might require in situ
cleaning which can be accomplished by
a) mechanical means (using a pig or ultrasonic device),
b) self-draining,
6 © ISO 2015 – All rights reserved

c) hydrodynamic means,
d) sterilization (steaming-in-place, SIP), and
e) chemical or biological (cleaning-in-place, CIP).
Care should be taken to avoid cross-contamination after cleaning fluids have been used.
Chemical compatibility should be established between the sensor wetted-materials, process fluid, and
cleaning fluid.
4.2.8 Hydraulic and mechanical vibrations
The manufacturer should specify the operating frequency range of the instrument to enable assessment
of possible influences of process or other external mechanically imposed frequencies. It is possible that
the performance of the flowmeter can be influenced by frequencies other than the operating frequencies.
These effects can largely be addressed by appropriate mounting or clamping of the instrument.
In environments with high mechanical vibrations or flow pulsations, consideration should be given to
the use of pulsation damping devices (see 4.3.7) and/or vibration isolators and/or flexible connections.
4.2.9 Pipe stress and torsion
The flow sensor is subjected to axial, bending, and torsional forces during operation. Changes in these
forces, resulting from variations in process temperature and/or pressure, can affect the Coriolis mass
flow measurement. Care should be taken to ensure that no forces are exerted on the flowmeter from the
clamping arrangements.
Measures should also be taken to prevent alignment stresses from being exerted on the Coriolis
flowmeter by connecting pipes.
Under no circumstances should the Coriolis flowmeter be used to align the pipe work.
4.2.10 Crosstalk between sensors
If two or more Coriolis flowmeters are to be mounted close together, interference through mechanical
coupling might occur. This is often referred to as crosstalk. The manufacturer should be consulted for
methods of avoiding crosstalk.
This should be recognized in the mechanical design of an installation to avoid interference or “crosstalk”.
Testing should be carried out after installation as flowmeter errors introduced can be significant but
not obvious in normal operation. If observed, the manufacturer should be consulted.
4.3 Effects due to process conditions and fluid properties
4.3.1 General
Variations in fluid properties, such as density, viscosity, and process conditions, such as pressure and
temperature, can influence the flowmeter’s performance. These effects have influences which differ
depending on which parameter is of interest.
4.3.2 Application and fluid properties
In order to identify the optimum flowmeter for a given application, it is important to establish the range
of conditions to which the Coriolis flowmeter will be subjected. These conditions should include the
following:
a) flow rates;
b) the range of densities;
c) the range of temperatures;
d) the range of pressures;
e) the pressure on the liquid adequate to prevent cavitation and flashing;
f) the permissible pressure loss;
g) the range of viscosities;
h) the properties of the metered fluids, including vapour pressure, two-phase flow, and corrosiveness;
i) unidirectional or bi-directional;
j) continuous, intermittent, or fluctuating;
k) corrosive additives (the effects of corrosive additives or contaminants on the flowmeters and the
quantity and size of foreign matter, including abrasive particles that can be carried in the liquid
stream).
4.3.3 Multiphase flow
Liquid mixtures, homogeneous mixtures of solids in liquids, or homogeneous mixtures of liquids with
entrained gas can be measured satisfactorily. Applications with two or more phases involving non-
homogeneous mixtures can cause additional measurement errors and in some cases, can stop operation
of the Coriolis flowmeter. Because of the random appearance of these effects, as well as the multitude
of application specific parameters influencing the measurement (e.g. flow profile, fluid velocity, density,
etc.), the impact on the measurement uncertainty is not fully predictable. Therefore, means to reduce
the influence by prevention (e.g. by installing adequate tank-level control systems or by installing an
adequate gas separator device) can be advisable. The installation of these devices, such as tank level
controls and gas separators, is beyond the scope of this International Standard.
Gases dissolved in the liquid can also lead to flashing, due to pressure loss in the upstream piping or
in the Coriolis flowmeter. Gas bubbles can lead to the creation of larger voids, which might disrupt the
measurement. Increasing pressure (e.g. by installing the sensor on the high-pressure side of a pressure
limitation device or control valve) helps keep the entrained gas in solution. If the gas is kept well mixed
and distributed to avoid imbalance of gas content between measurement tubes or inlet and outlet section
of the tube(s), the operability is maintained to higher gas volume fractions and lower measurement
uncertainty.
In the case of batch applications where the pipelines are empty at the start, a large gas void can be forced
through the Coriolis flowmeter by the liquid at the beginning of the batch process. Due to the undefined
error behaviour of the Coriolis flowmeter, the time required to fill the Coriolis flowmeter should be kept
as short as possible.
NOTE To discriminate the different components of the mixture, when more than two components are present
(e.g. water, gas, and oil), additional measurements are required (e.g. pressure, relative permittivity, percentage
water, or velocity). Typically, this is a task of a multiphase metering system.
4.3.4 Influence of process fluid
Erosion, corrosion, and deposition of material on the inside of the oscillating tube(s) (sometimes referred
to as coating) can initially cause measurement errors in flow and density, and in the longer term, sensor
failure.
4.3.5 Temperature effects
A change in oscillating tube(s) temperature affects the properties of the oscillating tube(s), and thus
influences the measurement of the fluid process by the Coriolis flowmeter. A means of compensation for
this temperature effect is usually incorporated in the transmitter.
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Users are advised to discuss temperature effects with the flowmeter manufacturer.
4.3.6 Pressure effects
Static pressure changes can affect the measurement of the fluid process by the Coriolis flowmeter; the
extent of the effect on measurement shall be specified by the manufacturer.
4.3.7 Pulsating flow effects
Coriolis flowmeters are generally able to perform under pulsating flow conditions except when pulsation
is relatively severe, which is often the case when reciprocating product pumps are in close proximity
to the metering system. When this situation occurs, steps should be taken to reduce pulsations to
levels that do not affect performance. This often requires passing through intermediate equipment,
improving pulsation damping equipment, changing pump type, etc. (see 4.2.8). The manufacturers’
recommendations should be observed regarding the application and the possible use of pulsation
damping devices.
4.3.8 Viscosity effects
Higher viscosity fluids might draw energy from the Coriolis flowmeter excitation system, particularly
at the start of flow. This phenomenon can cause the sensor tube(s) to momentarily stall during start
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