EN ISO 3104:2020

SLOVENSKI STANDARD
01-december-2020
Nadomešča:
SIST EN ISO 3104:1998
SIST EN ISO 3104:1998/AC:1999
Naftni proizvodi - Prozorne in neprozorne tekočine - Določevanje kinematične
viskoznosti in izračun dinamične viskoznosti (ISO 3104:2020)
Petroleum products - Transparent and opaque liquids - Determination of kinematic
viscosity and calculation of dynamic viscosity (ISO 3104:2020)
Mineralölerzeugnisse - Durchsichtige und undurchsichtige Flüssigkeiten - Bestimmung
der kinematischen Viskosität und Berechnung der dynamischen Viskosität (ISO
3104:2020)
Produits pétroliers - Liquides opaques et transparents - Détermination de la viscosité
cinématique et calcul de la viscosité dynamique (ISO 3104:2020)
Ta slovenski standard je istoveten z: EN ISO 3104:2020
ICS:
75.080 Naftni proizvodi na splošno Petroleum products in
general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 3104
EUROPEAN STANDARD
NORME EUROPÉENNE
September 2020
EUROPÄISCHE NORM
ICS 75.080 Supersedes EN ISO 3104:1996
English Version
Petroleum products - Transparent and opaque liquids -
Determination of kinematic viscosity and calculation of
dynamic viscosity (ISO 3104:2020)
Produits pétroliers - Liquides opaques et transparents Mineralölerzeugnisse - Durchsichtige und
- Détermination de la viscosité cinématique et calcul de undurchsichtige Flüssigkeiten - Bestimmung der
la viscosité dynamique (ISO 3104:2020) kinematischen Viskosität und Berechnung der
dynamischen Viskosität (ISO 3104:2020)
This European Standard was approved by CEN on 16 July 2020.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 3104:2020 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 3104:2020) has been prepared by Technical Committee ISO/TC 28 "Petroleum
and related products, fuels and lubricants from natural or synthetic sources" in collaboration with
Technical Committee CEN/TC 19 “Gaseous and liquid fuels, lubricants and related products of
petroleum, synthetic and biological origin.” the secretariat of which is held by NEN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by March 2021, and conflicting national standards shall
be withdrawn at the latest by March 2021.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 3104:1996.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
Endorsement notice
The text of ISO 3104:2020 has been approved by CEN as EN ISO 3104:2020 without any modification.

INTERNATIONAL ISO
STANDARD 3104
Third edition
2020-09
Petroleum products — Transparent
and opaque liquids — Determination
of kinematic viscosity and calculation
of dynamic viscosity
Produits pétroliers — Liquides opaques et transparents —
Détermination de la viscosité cinématique et calcul de la viscosité
dynamique
Reference number
ISO 3104:2020(E)
©
ISO 2020
ISO 3104:2020(E)
© ISO 2020
All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved

ISO 3104:2020(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Reagents and materials . 2
6 Apparatus design and requirements . 3
7 Verification . 6
7.1 Viscometer . 6
7.2 Liquid-in-glass thermometer. 6
7.3 Digital contact thermometer . 7
7.4 Timer . 7
8 Re-calibration . 7
9 Quality control . 7
10 Sample preparation . 7
10.1 Pre-analysis sample conditioning . 7
10.2 Visual inspection and filtering . 8
11 Procedure A — Manual equipment . 8
12 Procedure B — Automated equipment .10
13 Cleaning of the viscometer tube .11
14 Calculation .11
14.1 Procedure A — Manual viscometers .11
14.2 Procedure B — Automated viscometers .12
15 Expression of results .13
16 Precision of procedure A .13
16.1 Determinability, d .13
16.2 Repeatability, r .14
16.3 Reproducibility, R .14
17 Precision of Procedure B .15
17.1 Determinability, d .15
17.2 Repeatability, r .15
17.3 Reproducibility, R .15
18 Test report .15
Annex A (normative) Viscometer types, calibration and verification .17
Annex B (normative) Thermometers for kinematic viscosity test .18
Annex C (normative) Conditioning of samples prior to manual or automated analysis .22
Annex D (normative) Calculation of acceptable tolerance zone (band) to determine
conformance with a certified reference material .23
Bibliography .24
ISO 3104:2020(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 28, Petroleum and related products, fuels
and lubricants from natural or synthetic sources.
This third edition cancels and replaces the second edition (ISO 3104:1994), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— precision data have been updated to all actual fuels on the market;
— biodiesel (FAME) blends and paraffinic diesel have been included in the scope;
— the procedure description and allowance of automated techniques have been included.
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.
iv © ISO 2020 – All rights reserved

ISO 3104:2020(E)
Introduction
Many petroleum products, and some non-petroleum materials, are used as lubricants, and the correct
operation of equipment depends upon the appropriate viscosity of the liquid being used. In addition,
the viscosity of many petroleum fuels is important for the estimation of optimum storage, handling
and operational conditions. Thus, the accurate measurement of viscosity is essential to many product
specifications.
INTERNATIONAL STANDARD ISO 3104:2020(E)
Petroleum products — Transparent and opaque liquids
— Determination of kinematic viscosity and calculation of
dynamic viscosity
WARNING — This document does not purport to address all of the safety problems, if any,
associated with its use. It is the responsibility of users of this document to take appropriate
measures to ensure the safety and health of personnel prior to the application of this document,
and to determine the applicability of any other restrictions.
1 Scope
This document specifies Procedure A, using manual glass viscometers, and Procedure B, using glass
capillary viscometers in an automated assembly, for the determination of the kinematic viscosity, ν,
of liquid petroleum products, both transparent and opaque, by measuring the time for a volume of
liquid to flow under gravity through a calibrated glass capillary viscometer. The dynamic viscosity, η,
is obtained by multiplying the measured kinematic viscosity by the density, ρ, of the liquid. The range
2 2
of kinematic viscosities covered in this test method is from 0,2 mm /s to 300 000 mm /s over the
temperature range –20 °C to +150 °C.
NOTE The result obtained from this document is dependent upon the behaviour of the sample and is intended
for application to liquids for which primarily the shear stress and shear rates are proportional (Newtonian flow
behaviour). If, however, the viscosity varies significantly with the rate of shear, different results can be obtained
from viscometers of different capillary diameters. The procedure and precision values for residual fuel oils,
which under some conditions exhibit non-Newtonian behaviour, have been included.
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 3105, Glass capillary kinematic viscometers — Specifications and operating instructions
ISO 3696:1987, Water for analytical laboratory use — Specification and test methods
ASTM E1137, Standard Specification for Industrial Platinum Resistance Thermometers
ASTM E2877, Standard Guide for Digital Contact Thermometers
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 http:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org
ISO 3104:2020(E)
3.1
kinematic viscosity
ν
resistance to flow of a fluid under gravity
Note 1 to entry: For gravity flow under a given hydrostatic head, the pressure head of a liquid is proportional to
its density, ρ. For any particular viscometer, the time of flow of a fixed volume of fluid is directly proportional to
its kinematic viscosity, ν:
ν = η/ρ
Note 2 to entry: where η is the dynamic viscosity coefficient.
3.2
dynamic viscosity
coefficient of dynamic viscosity
viscosity
η
ratio between the applied shear stress and rate of shear of a liquid
Note 1 to entry: It is a measure of the resistance to flow or deformation of a liquid.
Note 2 to entry: The term dynamic viscosity is also used in a different context to denote a frequency-dependent
quantity in which shear stress and shear rate have a sinusoidal time dependence.
3.3
density
ρ
mass per unit volume of a substance at a given temperature
4 Principle
The time is measured for a fixed volume of liquid to flow under gravity through the glass capillary
of a calibrated viscometer under a reproducible driving head and at a known and closely controlled
temperature. The kinematic viscosity is the product of the measured flow time and the calibration
constant of the viscometer.
5 Reagents and materials
5.1 Cleaning solution, strongly-oxidizing cleaning solution or alkaline cleaning solutions can be used.
Alkaline cleaning solutions with a pH of greater than 10 are not recommended as they have been shown
to change the viscometer calibration. If these are used, then the viscometer calibration should be
verified to ensure there is no change.
5.2 Sample solvent, completely miscible a prewash with an aromatic solvent such as toluene or
heptane might be necessary to remove asphaltenic material. When cleaning capillaries inside the bath,
the boiling point of the cleaning solution shall be higher than the bath temperature.
5.3 Drying solvent, suitable and volatile at the used temperature. Filter before use. If moisture
remains, use a drying solvent miscible with water (5.4).
NOTE When cleaning capillaries inside the bath and if the bath temperature is higher than 50 °C, acetone is
not suitable.
5.4 Water, deionized or distilled, conforming to Grade 3 of ISO 3696:1987. Filter before use.
2 © ISO 2020 – All rights reserved

ISO 3104:2020(E)
5.5 Certified viscosity reference standards (CRM), with data provided by an accredited calibration
laboratory — traceable to the international agreed value of distilled water (1,003 4 mm /s at 20 °C as
specified in ISO/TR 3666) and calibrated in accordance with a standard practice for the basic calibration
[8]
of master viscometers and viscosity oils, such as in ASTM D2162 . ISO 17034 specifies the requirements
for CRM producers.
6 Apparatus design and requirements
6.1 Drying tubes, consisting of a desiccant drying system, consisting of either externally mounted
drying tubes or an integrated desiccant drying system designed to remove ambient moisture from the
capillary tube. Ensure that they are packed loosely and that the desiccant is not saturated with water.
6.2 Sample filter, micron screen or fretted (sintered) glass filter, no more than 75 µm.
6.3 Reagent filter, micron screen or fretted (sintered) glass filter, no more than 11 µm.
6.4 Ultrasonic bath, unheated — with an operating frequency between 25 kHz to 60 kHz and a typical
power output of ≤100 W, of suitable dimensions to hold container(s) placed inside of bath, for use in
effectively dissipating and removing air or gas bubbles that can be entrained in viscous sample types
prior to analysis. It is permissible to use ultra-sonic baths with operating frequencies and power outputs
outside this range; however, it is the responsibility of the laboratory to conduct a data comparison study
to confirm that results determined with and without the use of such ultrasonic baths does not materially
impact results.
6.5 Manual apparatus
6.5.1 Glass capillary viscometer, calibrated in accordance with ISO 3105.
The viscometer shall have a certificate of calibration provided by a laboratory that meets ISO/IEC 17025.
The calibration constant should be checked before first use of the capillary and only changed if
necessary.
The calibration constant, C, is dependent upon the gravitational acceleration at the place of calibration.
The variation in the value of g across the earth’s surface is about 0,5 % due to latitude plus approximately
0,003 % per 100 m altitude. Apply a gravity correction to the viscometer calibration constant as in
Formula (1), if the acceleration of gravity of the testing laboratory differs by more than 0,1 % of the
calibration laboratory.
g
 
CC= (1)
 
g
 
where the subscripts 1 and 2 indicate, respectively, the calibration laboratory and the testing laboratory.
NOTE Calculation of acceleration of gravity values can be found at www .NPL .co .uk.
IMPORTANT — Viscometers used for silicone fluids, fluorocarbons and other liquids, which are
difficult to remove using a cleaning agent, shall be reserved for the exclusive use of those fluids,
except during their calibration. Subject such viscometers to calibration checks at frequent
intervals. The solvent washings from these viscometers shall not be used for the cleaning of
other viscometers. If the viscometer is cleaned using the material in 5.1 then the user shall
verify the calibration before further use.
ISO 3104:2020(E)
6.5.2 Viscometer holder or mounting device within the temperature-controlled bath, enabling
the glass viscometer to be suspended so that the upper meniscus is directly above the lower meniscus
vertically within 1° in all directions.
Those viscometers whose upper meniscus is offset from directly above the lower meniscus shall be
suspended vertically within 0,3° in all directions (see ISO 3105).
The proper alignment of vertical parts may be confirmed by using a plumb line, but for rectangular
baths with opaque ends, this might not be possible.
6.5.3 Temperature-controlled bath, containing a transparent liquid of sufficient depth such that at
no time during the measurement is any portion of the sample in the viscometer less than 20 mm below
the surface of the bath liquid or less than 20 mm above the bottom of the bath.
Temperature control of the bath liquid shall be such that, for each series of flow-time measurements,
within the range of 15 °C to 100 °C the temperature of the bath medium does not vary by more
than ±0,02 °C from the selected temperature over the length of the viscometer, and/or between the
position of each viscometer, and/or at the location of the thermometer i.e. the temperature needs to
be constant at the capillary and at the position of the thermometer within a maximum difference of
0,04 °C. For temperatures outside this range, the deviation from the desired temperature shall not
exceed ±0,05 °C.
Adjust and maintain the viscometer bath at the required test temperature within the limits given
in 6.5.3, taking account of the conditions given in Annex B and of the corrections supplied on the
certificates of calibration for the thermometers. Maintain the bath temperature at the test temperature
using the readings of the temperature measuring device with the corrections supplied by the certificate
of calibration.
Thermometers shall be held in an upright position under the same conditions of immersion as when
calibrated. In order to obtain the most reliable temperature measurement, it is recommended that two
thermometers with valid calibration certificates be used. They should be viewed with a lens assembly
giving approximately 5× magnification and be arranged to eliminate parallax errors.
6.5.4 Temperature-measuring device, for the range 0 °C to 100 °C, being either:
a) a calibrated liquid-in-glass thermometer, (see Annex B) with a calibration and measurement
capability (CMC) of ±0,02 °C after correction or better, or
b) a digital contact thermometer (DTC) as described in 6.5.4.2 with equal or better CMC.
6.5.4.1 The calibration data should be traceable to a calibration or metrology standards body and
meet the uncertainty of measurement required. The calibration certificate shall include data covering the
series of temperature test points which are appropriate for its intended use. When two thermometers are
used in the same bath in this range, they shall agree within 0,04 °C. See Annex B for the list of complying
thermometers.
If calibrated liquid-in-glass thermometers are used, the use of two thermometers is recommended.
Outside the range 0 °C to 100 °C, a calibrated liquid in-glass thermometer (see Annex B) or a DTC as
described in 6.5.4.2 with a CMC of ±0,05 °C or better shall be used, and when two thermometers are
used in the same bath they shall agree within ±0,1 °C.
When using liquid-in-glass thermometers, use a magnifying device to read the thermometer to
the nearest 1/5 division (e.g. 0,01 °C or 0,02 °C) to ensure that the required test temperature and
temperature control capabilities are met. It is recommended that thermometer readings (and any
corrections supplied on the certificates of calibrations for the thermometers) be recorded on a periodic
basis to demonstrate compliance with the test method requirements.
6.5.4.2 A DCT meeting the requirements in Table 1.
4 © ISO 2020 – All rights reserved

ISO 3104:2020(E)
NOTE The resulting uncertainty of calibration can be dependent upon the immersion depth.
6.5.4.3 The DCT probe is to be immersed no less than the immersion depth stated on the calibration
certificate.
NOTE With respect to DCT probe immersion depth, a procedure is available in ASTM E644 -11: 2011, Section
[10] [9]
7 , for determining the minimum depth. With respect to an ice bath, ASTM E563 provides guidance on
the preparation of an ice bath however variance from the specific steps is permitted provided preparation is
consistent as it is being used to track change in calibration.
Table 1 — DCT requirements
Criteria Minimum requirements
DCT ASTM E2877 Class A
Display resolution 0,01 °C, recommended 0,001 °C
Display accuracy ±20 mK (±0,02 °C) for combined probe and sensor
Sensor type RTD, such as a PRT or thermistor
Drift less than 10 mK (0,01 °C) per year
Response time less than or equal to 6 s, as defined in specification ASTM E1137/E1137M
Linearity 10 mK over range of intended use
Calibration report The DCT shall have a report of temperature calibration which should be traceable to
a national calibration or metrology standards body issued by a calibration laboratory
a
with demonstrated competency in temperature calibration .
Calibration data The calibration report shall include at least 3 calibration temperatures including 0 °C
and 2 other points including the test temperature of use and state the immersion
depth under which this was calibrated and the resulting uncertainty.
a
An ISO/IEC 17025 accredited laboratory with temperature calibration in its accreditation scope and which meets the
stated measurement uncertainty would meet this requirement.
6.6 Automated apparatus
6.6.1 General
Automated viscometers, which use the technical principles of this document, are acceptable provided
they meet the accuracy and precision of all the equipment listed in 6.5. In addition, if they are used to
measure kinematic viscosity in samples subject to conditioning using the steps in Annex C, a heated
sample tray shall be used if the sample is not analysed immediately after conditioning. This sample
tray (6.6.2) shall be heated to a temperature which will not allow the sample to fall below the testing
temperature.
Flow times of less than 200 s are acceptable; however, the kinetic energy correction shall be calculated
and should not exceed 3 % of the measured viscosity. Where a value of greater than 3 % is achieved the
analysis should be repeated using a smaller diameter viscometer tube.
6.6.2 Sample trays
Some automated equipment contain sample loading trays for analysis of multiple samples. When a
sample has been subjected to conditioning using the steps in Annex C, the sample shall not be allowed
to cool below the testing temperature on the loading tray as this will result in an increase in measured
viscosity as compared to the manual procedure. As the temperature of the conditioned sample can
drop very quickly, for analysis of these samples, the sample loading trays shall be heated above the test
temperature to ensure the temperature of the sample does not fall below the test temperature at the
time of analysis, and the nature of the sample is not changed. For analysis of these samples at 50 °C a
sample tray heated at 54 °C has been shown to be sufficient to maintain the sample temperature above
50 °C for at least 40 min. For analysis of these samples at other temperatures the lab should establish
the correct sample tray temperature and time before analysis.
ISO 3104:2020(E)
6.6.3 Temperature measuring device
If embedded, a temperature measuring device shall fully meet the requirements of 6.5.4 and be
removable for an external calibration. The embedded device will provide an independent reference
temperature read-out, allowing the temperature control of the automated apparatus to be adjusted at
the required set-point of test.
6.7 Timing device, capable of taking readings with a discrimination of 0,1 s or better, and having an
uncertainty within ±0,07 % of the reading when tested over intervals of 200 s and 1 000 s.
Regularly check timers for accuracy and maintain records of such checks.
Time signals as broadcast by the National Institute of Standards and Technology (NIST) are a convenient
and primary standard reference for calibrating timing devices.
NOTE Many broadcast networks put out a standard frequency signal, as do many telephone networks. Such
signals are suitable for checking the timing devices used to an accuracy of 0,1 s.
Timing devices employed in automated viscometers may be an integral part of the apparatus and
typically are digital (using a precision crystal oscillator) with precision discriminations of 0,01 s
or better. As such, the timing devices may not be able to be individually verified once installed.
Documentation of the accuracy of the timing device over the intended measuring range of the
viscometer tube should therefore be provided by the manufacturer. Independent verification of timing
devices should be provided in cases where the above-mentioned limits are not satisfied.
Electrical timing devices may be used if the current frequency is controlled to an uncertainty of 0,05 %
or better. Alternating currents, as provided by some public power systems, are controlled intermittently
rather than continuously. When used to actuate electrical timing devices, such control can cause large
errors in viscosity flow measurements.
7 Verification
7.1 Viscometer
Verify the calibration of the viscometer using a certified viscosity reference standard (5.5) following
Procedure A (manual, Clause 11) or Procedure B (automated, Clause 12). Acceptable tolerance bands
for this verification check shall be as detailed in Annex D. If the measured kinematic viscosity does
not fall within this acceptable range, recheck each step in the procedure, including thermometer and
viscometer calibrations and cleaning to locate the source of error. Table 1 in ISO 3105:1994 gives details
of standards available.
Alternatively verify working viscometers against a reference viscometer having a certificate of
calibration provided by an accredited calibration laboratory accredited to ISO 3105.
Verification is required at least prior to first use of the viscometer and whenever a physical change is
made to the apparatus e.g. re-calibrating the temperature set-point, after cleaning or investigating the
failure of QA/QC protocol in place.
7.2 Liquid-in-glass thermometer
Verify the calibration of the liquid in a glass thermometer on a periodic basis in line with B.2 at least
at the frequencies described and maintain records of such checks. A complete new recalibration of the
thermometer, while permitted, is not necessary in order to meet the accuracy ascribed to the design of
the thermometer until the ice point change from the last full calibration amounts to one scale division
such as 0,05 °C. Some thermometers have an ice point scale for this activity.
6 © ISO 2020 – All rights reserved

ISO 3104:2020(E)
7.3 Digital contact thermometer
Verify the calibration of the DCT at least annually. The probe shall be recalibrated, when the check value
differs by more than 0,01 °C from the last probe calibration.
Verification can be accomplished with the use of a water triple point cell or an ice bath.
[9] [11] [12]
ASTM standard practices given in ASTM E563 , ASTM E1750 , and ASTM E2593 may be used as
reference regarding checking calibrations.
7.4 Timer
Verify the accuracy of the timer, regularly check timers and maintain records of such checks.
NOTE Many broadcast networks put out a standard frequency signal, as do many telephone networks. Such
signals are suitable for checking the timing devices used to an accuracy of 0,1 s.
8 Re-calibration
Glass capillary viscometer recalibration, if required, should be undertaken using the procedures in
ISO 3105.
CAUTION — Users are cautioned that recalibrating equipment in situ when a verification fails
potentially calibrates in an error. The most common sources of error are caused by particles
of dust lodged in the capillary bore and temperature measurement errors. It should be
appreciated that a correct result obtained on standard oil does not preclude the possibility of a
counterbalancing combination of the possible sources of error.
9 Quality control
Use a quality control (QC) sample that is representative of the product(s) routinely tested by the
laboratory to confirm that the instrument is in statistical control at a frequency in line with the testing
facility quality assurance (QA) protocol.
This might not be possible if the product under test cannot be used as a QC material due to its nature
(unstable or subject to thermal treatment).
When QC/QA protocols are already established in the testing facility, these can be used when they
confirm the reliability of the test result.
Where the testing facility lab uses a CRM material as a measure of quality control, Annex D can be used
as the procedure to construct suitable acceptable tolerance zones for the QC/QA system.
10 Sample preparation
10.1 Pre-analysis sample conditioning
10.1.1 Using Table 2, verify whether the sample type under analysis requires conditioning before
analysis and, if so, follow the relevant procedure and steps noted, before charging the viscometer.
10.1.2 If the sample is transparent, but not liquid, at room temperature, for example, samples with a
high pour point value, then the sample should be sufficiently heated to ensure it can flow freely before
charging the viscometer.
ISO 3104:2020(E)
10.2 Visual inspection and filtering
When the sample is liquid then visually inspect it. If the sample contains fibres or solid particles, use a
sample filter (6.2) prior to or during charging of the viscometer tube. At all stages, protect the sample
from contamination.
Table 2 — Sample types and conditioning procedures
Sample type Is sample conditioning Is sample filter Conditioning procedure
required before required? reference
analysis?
a
Base oils No No Not required
a
Gas oils No No Not required
a
Distillate No No Not required
a
Kerosene No No Not required
a
Jet fuel No No Not required
a
Formulated oils No No 10.1.2
a
Lubricant additives No No 10.1.2
a
Biofuel blend No No 10.1.2
a
Biodiesel B100 (transparent) No No 10.1.2
a
Petroleum wax (transparent) No No 10.1.2
Biodiesel B100 (opaque) Yes Yes Annex C
Petroleum wax (opaque) Yes Yes Annex C
Residual fuel oils Yes Yes Annex C
Steam-refined cylinder oils Yes Yes Annex C
Black lubricating oils Yes Yes Annex C
Used oils No Yes Not required
a
Unless contains fibres, solid particles or is not transparent.
11 Procedure A — Manual equipment
11.1 Check the bath temperature using the temperature measuring device, ensuring that the set point is
within the acceptable tolerance and accuracy of the test temperature and record this data.
With certain products which exhibit “gel-like” behaviour, users should take care that measurements
are made at temperatures sufficiently high for such materials to flow freely, so that similar kinematic
viscosity results are obtained in viscometers of different capillary diameter.
11.2 Select suitable clean, dry calibrated viscometer(s) having a range covering the estimated kinematic
viscosity at the specified test temperature. The flow time shall not be less than 200 s, or the minimum
flow time specified in Annex A for viscometer types and/or sizes and the maximum flow time stated in
ISO 3105.
The specific details of operation vary depending on the type of viscometer. The operating instructions
for the different types of viscometers listed in Table A.1 are given in ISO 3105. In general, the viscometers
used for opaque liquids are of the reverse-flow type listed in Table A.1 type C.
For the measurement of kinematic viscosity of jet fuels at −20 °C, only suspended-level type ISO 3105
viscometers as noted in Table A.1 shall be used. The suspended-level type viscometer types used for jet
fuel do not require a correction to the calibration constant for the test temperature being used.
11.3 Charge the viscometer with the sample as per the operating instructions in accordance with
ISO 3105 for the particular type of viscometer, as described in Annex A. Then place in the bath in
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ISO 3104:2020(E)
the manner dictated by the design of the instrument. This operation shall be in conformity with that
employed when the instrument was calibrated.
Allow the charged viscometer to remain in the bath long enough to reach the test temperature, and
to ensure that all air bubbles in the sample have dispersed. As the equilibration time in the bath will
vary for different products, different viscometer tubes, for different temperatures and for different
kinematic viscosities, establish and document a safe equilibrium time by trial. A minimum of 30 min is
required for jet fuel at −20 °C.
Where the design of the viscometer requires it, adjust the volume of the sample to the mark after the
sample has reached temperature equilibrium.
NOTE Some viscometers require charging outside of the bath due to their design.
When the test temperature is below the ambient dew point, the use of loosely packed drying tubes
affixed to the open ends of the viscometer is permitted but not mandatory. These are designed to
prevent water condensation. However, it is essential that they do not set up a pressure differential and
affect the rate of flow. Before first use of drying tubes, it is recommended that a certified viscosity
reference standard is used to verify the correct use of the viscometer with and without drying tubes in
order to ensure that there is no restriction in the flow.
Special conditions apply when the test temperature is below the dew point, such as for analysis at
−20 °C. To ensure moisture does not condense or freeze on the walls of the capillary, it is recommended
to charge the viscometer outside the bath and if used affix loosely packed drying tubes to the open
ends of the viscometer. The
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