EN ISO 21645:2021

SLOVENSKI STANDARD
01-junij-2021
Nadomešča:
SIST EN 15442:2011
Trdna alternativna goriva - Metode za vzorčenje (ISO 21645:2021)
Solid recovered fuels - Methods for sampling (ISO 21645:2021)
Feste Sekundärbrennstoffe - Verfahren zur Probenahme (ISO 21645:2021)
Combustibles solides de récupération - Méthodes d'échantillonnage (ISO 21645:2021)
Ta slovenski standard je istoveten z: EN ISO 21645:2021
ICS:
75.160.10 Trda goriva Solid fuels
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 21645
EUROPEAN STANDARD
NORME EUROPÉENNE
April 2021
EUROPÄISCHE NORM
ICS 75.160.10 Supersedes EN 15442:2011
English Version
Solid recovered fuels - Methods for sampling (ISO
21645:2021)
Combustibles solides de récupération - Méthodes Feste Sekundärbrennstoffe - Verfahren zur
d'échantillonnage (ISO 21645:2021) Probenahme (ISO 21645:2021)
This European Standard was approved by CEN on 23 February 2021.

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
© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 21645:2021 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 21645:2021) has been prepared by Technical Committee ISO/TC 300 "Solid
recovered materials, including solid recovered fuels" in collaboration with Technical Committee
CEN/TC 343 “Solid Recovered Fuels” the secretariat of which is held by SFS.
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 October 2021, and conflicting national standards shall
be withdrawn at the latest by October 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 15442:2011.
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 21645:2021 has been approved by CEN as EN ISO 21645:2021 without any modification.

INTERNATIONAL ISO
STANDARD 21645
First edition
2021-03
Solid recovered fuels — Methods for
sampling
Combustibles solides de récupération — Méthodes d'échantillonnage
Reference number
ISO 21645:2021(E)
©
ISO 2021
ISO 21645:2021(E)
© ISO 2021
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 2021 – All rights reserved

ISO 21645:2021(E)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols . 7
5 Principle . 8
6 Development of a sampling plan. 8
6.1 Principle . 8
6.2 Definition of overall objectives. 9
6.3 Definition of a lot and determining lot size . 9
6.3.1 General. 9
6.3.2 Definition of a lot in case of sampling from a material flow .10
6.3.3 Definition of a lot in case of transport by a vehicle .10
6.3.4 Definition of a lot in case of transport by ship .10
6.3.5 Definition of a lot in case of sampling from a static lot .10
6.4 Determination of the sampling procedure.10
6.5 Determination of the number of increments .11
6.6 Determination of minimum sample mass .11
6.7 Determination of the minimum increment mass .11
6.7.1 Determination of minimum increment mass for material flows.11
6.7.2 Determination of the minimum increment mass for static lots, vehicles or
ships .11
6.8 Determination of the planned increment and planned sample amounts .11
6.9 Selection of distribution of increments over a lot .12
6.9.1 General.12
6.9.2 Determination of the distribution of the increments when sampling from
a material flow .12
6.9.3 Determination of the distribution of the increments when sampling from
a vehicle(s) .12
6.9.4 Implementation of sampling from a static lot .13
6.10 Sampling equipment and implements .14
7 Implementation of the sampling plan .14
7.1 Steps before actual sampling .14
7.2 Steps during sampling .14
7.3 Steps after sampling .14
8 Handling and storage of samples .15
9 Precision .15
Annex A (normative) Procedure for the development of a sampling plan .16
Annex B (normative) Sampling plan .19
Annex C (informative) Example of a sampling plan .23
Annex D (normative) Sampling equipment and implements .28
Annex E (normative) Determination of minimum sample mass .33
Annex F (normative) Determination of increment mass for sampling from material flows .38
Annex G (normative) Determination of increment mass for sampling from static lots,
vehicles or ships .41
Annex H (normative) Implementation of sampling plan from a material flow .42
ISO 21645:2021(E)
Annex I (normative) Implementation of the sampling plan from a static lot or vehicle .46
Annex J (normative) Minimum sample mass required for analysis .48
Annex K (informative) Additional information about precision .51
Annex L (informative) Examples for stratified and stratified random sampling .54
Bibliography .56
iv © ISO 2021 – All rights reserved

ISO 21645:2021(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 300, Solid recovered fuels.
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.
ISO 21645:2021(E)
Introduction
The testing of solid recovered fuels (SRF) enables informed decisions about their subsequent handling
and use. In order to carry out a test on a solid recovered fuel, a sample of the material is required. Before
any sampling operation is devised, it is important that the objectives for sampling are clearly identified
and subsequently well executed to ensure that the expectations of any involved parties are recognized
and satisfied. The identification of objectives helps to define the level of testing required, e.g. thorough
examination or routine testing, and in addition desired reliability of testing / assessment and frequency
of testing. The sampling objectives, along with the sequence of operations required to fulfil them, are
detailed in an overall sampling plan. After a sampling plan has been prepared, the sampling of SRF itself
can be implemented.
This document is largely based on the work already done by CEN/TC 292 “Characterization of waste”
(now integrated in CEN/TC 444 “Environmental characterization of solid matrices”), in particular EN
[1] [2]
14899:2005 and CEN/TR 15310-1:2006 .
The main characteristic that makes SRF samples significantly different from other kinds of waste is
that SRFs are very often solid, but neither "granular" nor monolithic; it often happens that SRF samples
are fibrous-like materials. This typical characteristic of SRF implies that the statistical formula for
sampling of EN 14899:2005 and CEN/TR 15310-1:2006, Annex D are not applicable without amendment.
The "shape factor" ( f ) is additionally needed in the statistical formula.
Figure 1 shows the links between the essential elements of a testing program.
Sampling procedures are provided for a range of process streams and common storage conditions. The
sampling technique adopted depends on a combination of different characteristics of the material and
circumstances encountered at the sampling location. The determining factors are:
— the type of solid recovered fuel;
— the situation at the sampling location / the way in which the material occurs (e.g. in a stockpile, on
a conveyor belt, in a lorry);
— the (expected) degree of heterogeneity (e.g. monostreams, mixed fuels, blended fuels).
This document is primarily geared toward laboratories, producers, suppliers and purchasers of solid
recovered fuels, but is also useful for the authorities and inspection organizations.
[3]
Sampling of solid biofuels is described in ISO 18135 .
vi © ISO 2021 – All rights reserved

ISO 21645:2021(E)
Figure 1 — Links between the essential elements of a testing program
INTERNATIONAL STANDARD ISO 21645:2021(E)
Solid recovered fuels — Methods for sampling
1 Scope
This document specifies methods for taking samples of solid recovered fuels for example from
production plants, from deliveries or from stock. It includes manual and mechanical methods.
It is not applicable to solid recovered fuels that are formed by liquid or sludge, but it includes
dewatered sludge.
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 21637, Solid recovered fuels — Terminology, definitions and descriptions
1)
ISO 21640:— , Solid recovered fuels — Specifications and classes
ISO 21644, Solid recovered fuels — Methods for the determination of biomass content
ISO 21654, Solid recovered fuels — Determination of calorific value
ISO 21656, Solid recovered fuels — Determination of ash content
ISO 21660-3, Solid recovered fuels — Determination of moisture content using the oven dry method —
Part 3: Moisture in general analysis sample
ISO 21663, Solid recovered fuels — Methods for the determination of carbon (C), hydrogen (H) and nitrogen
(N) content
ISO 22167, Solid recovered fuels — Determination of the content of volatile matter
EN 15408, Solid recovered fuels — Method for the determination of sulphur (S), chlorine (Cl), fluorine (F)
and bromine (Br) content
EN 15410, Solid recovered fuels — Method for the determination of the content of major elements (Al, Ca,
Fe, K, Mg, Na, P, Si, Ti)
EN 15411, Solid recovered fuels — Methods for the determination of the content of trace elements (As, Ba,
Be, Cd, Co, Cr, Cu, Hg, Mo, Mn, Ni, Pb, Sb, Se, Tl, V and Zn)
EN 15415-1, Solid recovered fuels — Determination of particle size distribution — Part 1: Screen method
for small dimension particles
EN 15415-2, Solid recovered fuels — Determination of particle size distribution — Part 2: Maximum
projected length method (manual) for large dimension particles
EN 15415-3, Solid recovered fuels — Determination of particle size distribution — Part 3: Method by image
analysis for large dimension particles
CEN/TS 15401, Solid recovered fuels — Determination of bulk density
CEN/TR 15404, Solid recovered fuels — Methods for the determination of ash melting behaviour by using
characteristic temperatures
1) Under preparation. Stage at the time of publication ISO/FDIS 21640.
ISO 21645:2021(E)
CEN/TS 15405, Solid recovered fuels —Determination of density of pellets and briquettes
CEN/TS 15406, Solid recovered fuels —Determination of bridging properties of bulk material
CEN/TS 15412, Solid recovered fuels — Methods for the determination of metallic aluminum
CEN/TS 15414-1, Solid recovered fuels — Determination of moisture content using the oven dry method —
Part 1: Determination of total moisture by a reference method
CEN/TS 15414-2, Solid recovered fuels — Determination of moisture content using the oven dry method —
Part 2: Determination of total moisture by a simplified method
CEN/TS 15639, Solid recovered fuels — Determination of mechanical durability of pellets
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 21637 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
coefficient of variation
estimate of the standard deviation of a population from a sample (3.28) of n results divided by the mean
of that sample
Note 1 to entry: The coefficient of variation is frequently stated as a percentage.
[4]
Note 2 to entry: Adapted from Eurachem/Citac Guide CG 4 .
3.2
composite sample mass
amount of sample (3.28) taken from a lot (3.11) or a sub-lot (3.40) consisting of all the increments (3.9)
3.3
distribution factor
correction factor for the particle size distribution (3.20) of the material to be sampled
[SOURCE: ISO 21637:2020, 3.17]
3.4
drop flow
material flow falling over an overflow point or a drop point in a transport system
[SOURCE: ISO 21637:2020, 3.18]
3.5
duplicate sample
two samples (3.28) taken under comparable conditions
Note 1 to entry: This selection may be accomplished by taking units adjacent in time or space.
Note 2 to entry: The replicate sample is usually used to estimate sample variability.
[SOURCE: ISO 21637:2020, 3.23, modified – Note 2 to entry has been added.]
3.6
general analysis sample
sub-sample (3.41) of a laboratory sample (3.10) having a nominal top size of 1 mm or less and used for a
number of chemical and physical analyses
2 © ISO 2021 – All rights reserved

ISO 21645:2021(E)
3.7
heterogeneity
degree to which a property or type of particle of a solid recovered fuel (3.34) is not uniformly distributed
throughout a quantity of material
[SOURCE: ISO 21637:2020, 3.36]
3.8
homogeneity
degree to which a property or type of particle of a solid recovered fuel (3.34) is uniformly distributed
throughout a quantity of material
[SOURCE: ISO 21637:2020, 3.37]
3.9
increment
portion of solid recovered fuel (3.34) extracted from a lot (3.11) or sub-lot (3.40) in a single operation of
the sampling (3.30) device
[SOURCE: ISO 21637:2020, 3.39]
3.10
laboratory sample
composite sample (3.28) received by the laboratory on which sample preparation (3.29) procedures for
analysis are undertaken
Note 1 to entry: When the laboratory sample is further prepared by mixing, subdividing, particle size reduction
or by combinations of these operations, the result is the general analysis sample. A test portion is removed from
the general analysis sample for the performance of the test or for analysis. When no preparation of the laboratory
sample is required, the test portion may be taken directly from the laboratory sample.
3.11
lot
defined quantity of fuel for which the quality is to be determined
Note 1 to entry: A lot may be divided into sub-lots.
[5]
[SOURCE: ISO 13909-1:2016, 3.16 ]
3.12
mechanical durability
ability of densified fuels to remain intact during handling and transportation
Note 1 to entry: Typical measures of resistance are shock and/or abrasion as a consequence of handling and
transportation processes, characterized by disintegration and fines formulation.
Note 2 to entry: Examples are briquettes and pellets.
[SOURCE: ISO 21637:2020, 3.41]
3.13
minimum increment mass
minimum dimension or mass of the increment that is taken from a lot (3.11) in a single operation of the
sampling (3.29) device from the point of view of preserving its representativeness
3.14
minimum sample mass
minimum amount or dimension of the sample required during sampling (3.30) and sample preparation
(3.29) from the point of view of preserving its representativeness
Note 1 to entry: The minimum sample mass is at least equal to the increment mass multiplied by the number of
increments, and is linked directly to the nominal top size.
ISO 21645:2021(E)
3.15
moisture
water removable under specific conditions
Note 1 to entry: See also total moisture (3.43).
[SOURCE: ISO 21637:2020, 3.46, modified – Note 1 to entry has been added.]
3.16
nominal minimum size
d
smallest aperture size of the sieve used for determining the particle size distribution (3.20) of solid fuels
through which at least 5 % by mass of the material passes
3.17
nominal top size
d
smallest aperture size of the sieve used for determining the particle size distribution (3.20) of solid
recovered fuels (3.34) through which at least 95 % by mass of the total material passes through the sieve
[SOURCE: ISO 21637:2020, 3.48]
3.18
particle density
density of a single particle
Note 1 to entry: Pores within the particle are included.
[SOURCE: ISO 21637:2020, 3.52]
3.19
particle size
size of the fuel particles as determined in a solid fuel
Note 1 to entry: Different methods of determination can give different results.
Note 2 to entry: See also particle size distribution (3.20).
3.20
particle size distribution
proportions of various particle sizes (3.19) in a solid fuel
3.21
particle size reduction
reduction of the nominal top size (3.17) of a sample (3.28) or sub-sample (3.41)
3.22
planned increment mass
planned dimension or mass of the increment (3.9) that is taken from a lot (3.11) in a single operation of
the sampling (3.30) device
3.23
planned sample mass
sample (3.28) amount or dimension that is planned to be taken during sampling (3.29)
Note 1 to entry: The planned sample mass is derived from the minimum sample mass and includes additional
considerations regarding the sampling procedure, practical handling and storage and the required sample
amounts for analysis.
Note 2 to entry: The planned sample mass can be equal to the minimum sample mass.
4 © ISO 2021 – All rights reserved

ISO 21645:2021(E)
3.24
precision
closeness of agreement between independent test/measurement results obtained under stipulated
conditions
Note 1 to entry: Precision depends only on the distribution of random errors and does not relate to the true value
or the specified value.
Note 2 to entry: The measure of precision is usually expressed in terms of imprecision and computed as a
standard deviation of the test results or measurement results. Less precision is reflected by a larger standard
deviation.
Note 3 to entry: Quantitative measures of precision depend critically on the stipulated conditions.
[6]
[SOURCE: ISO 3534-2:2006, 3.3.4 , modified – Second sentence of Note 3 to entry has been removed.]
3.25
producer
organization or unit responsible for the production of solid recovered fuel (3.34)
Note 1 to entry: The producer can also be the supplier of the fuel.
Note 2 to entry: The producer may not directly produce or process non-hazardous waste into solid recovered
fuel but may receive material appropriate to its requirements and already meeting the minimum criteria of
ISO 21640:—.
[SOURCE: ISO 21637:2020, 3.60]
3.26
random sampling
taking a sample (3.28) at a random location within a specified range or from a specified lot (3.11) such that
every portion of the solid recovered fuel (3.34) would have the same chance of being part of the sample
Note 1 to entry: A random location is determined by lot.
3.27
replicate sampling
taking of increments (3.9) at intervals, which are combined in rotation into different containers to give
two or more samples (3.28) of approximately equal mass
Note 1 to entry: The replicate sampling is usually used to estimate sample variability.
3.28
sample
quantity of material, from a larger amount for which the quality is to be determined
Note 1 to entry: See also increment (3.9).
[SOURCE: ISO 21637:2020, 3.63, modified – Note 2 and 3 to entry have been removed.]
3.29
sample preparation
actions taken to obtain representative laboratory sample (3.10) or test portions (3.42) from the original
sample as received
[SOURCE: ISO 21637:2020, 3.66]
3.30
sampling
process of drawing or constituting a sample (3.28)
[SOURCE: ISO 21637:2020, 3.68]
ISO 21645:2021(E)
3.31
sampling plan
predetermined procedure for the selection, withdrawal, preservation, transportation and preparation
of the portions to be removed from a population as a sample (3.28)
[SOURCE: ISO 21637:2020, 3.70]
3.32
sampling record
report which serves as a check list and provides the investigator with all necessary information about
the sampling (3.30) techniques applied at the site and any additional important information
[7]
[SOURCE: ISO 11074:2015, 4.4.26 , modified – Part of definition has been removed as irrelevant to the
context of this document.]
3.33
shape factor
factor that corrects the minimum sample mass (3.14) if the particles in a lot have not a regular shape (e.g.
spherical or cubic)
[SOURCE: ISO 21637:2020, 3.72]
3.34
solid recovered fuel
solid fuel for energy purposes according to ISO 21640:— derived from non-hazardous waste
Note 1 to entry: A number of terms can be used to describe fuels from waste that might (but not always) qualify
as solid recovered fuels. For example, refuse derived fuel, refuse derived paper and plastics densified fuel, waste
derived fuel, shredded light fraction, sewage sludge, end of life wood, fuel composed of either municipal solid waste,
industrial waste, commercial waste, construction and demolition waste, animal waste (e.g. meat and bone meal).
Note 2 to entry: This definition does not consider the value of the waste.
Note 3 to entry: Whether the input material is hazardous or non-hazardous is determined through national laws
and directives or by categorization of the fuel through the annexes in the Basel Convention on the control of
transboundary movements of hazardous wastes and their disposal.
[SOURCE: ISO 21637:2020, 3.75]
3.35
specification
document stating requirements
Note 1 to entry: See also specification of solid recovered fuels (3.36).
[8]
[SOURCE: ISO 9000:2015, 3.8.7 , modified - Example and notes to entry have been removed/replaced.]
3.36
specification of solid recovered fuels
list of properties that characterize solid recovered fuel (3.34)
Note 1 to entry: A template for such specification is given in ISO 21640:—.
[SOURCE: ISO 21637:2020, 3.76, modified – Note 1 to entry has been added.]
3.37
static lot
lot (3.11) that is not in motion during the sampling (3.30), or transported by a conveyor or alternative
transport system
[SOURCE: ISO 21637:2020, 3.77]
6 © ISO 2021 – All rights reserved

ISO 21645:2021(E)
3.38
stratified random sampling
stratified sample (3.28) constituting by increments which are taken randomly within each stratum
3.39
stratified sampling
sampling (3.30) constituting by increments taken from identified subparts (strata) of the parent
population
Note 1 to entry: Definition derived from ‘stratified sample’ as defined in ISO 21637:2020, 3.78.
3.40
sub-lot
part of a lot (3.11) for which a test result is required
[SOURCE: ISO 21637:2020, 3.81]
3.41
sub-sample
portion of a sample (3.28)
Note 1 to entry: A sub-sample is obtained by procedures in which the items of interest are randomly distributed
in part of equal or unequal size.
Note 2 to entry: A sub-sample may be either a portion of the sample obtained by selection or division of the
sample itself, or the final sample of a multistage sample preparation.
[SOURCE: ISO 21637:2020, 3.82]
3.42
test portion
sub-sample (3.41) either of a laboratory sample (3.10) or a test sample required for the specific
measurement
Note 1 to entry: The test portion can be taken from the laboratory sample directly if no preparation of sample is
required (e.g. for bulk density determination or particle size distribution).
[SOURCE: ISO 21637:2020, 3.83, modified – Note 1 to entry has been added.]
3.43
total moisture
moisture content
moisture in a fuel measured under specific conditions on as received basis
3.44
trueness
closeness of agreement between the expectation of a test result or a measurement result and a true value
Note 1 to entry: The measure of trueness is usually expressed in terms of bias.
Note 2 to entry: Trueness is sometimes referred to as “accuracy of the mean”. This usage is not recommended.
Note 3 to entry: In practice, the accepted reference value is substituted for the true value.
Note 4 to entry: The determination of the exact trueness for waste and from waste derived materials such as
solid recovered fuels is by definition not possible.
[SOURCE: ISO 3534-2:2006, 3.3.3, modified - Note 4 to entry has been added.]
4 Symbols
For the purposes of this document, the following symbols apply.
ISO 21645:2021(E)
b is the breadth of the flow, in m
C is the coefficient of variation
V
d is the nominal minimum size of a particle, in mm
d is the nominal top size of a particle, in mm
3 3
f is the shape factor, in m /m
G is the conveyor load, in kg/m
g is the correction factor for distribution in the particle size
m is mass, in kg
n is the number of increments to be taken per lot
p is the fraction of the particles with a specific characteristic (such as a specific contaminant), in
kg/kg, and is equal to 0,1
V is volume, in m
v is conveyor velocity, in m/s
Ф is the drop flow, in kg/s
d
λ is the bulk density of the solid recovered fuel, in kg/m
b
λ is the particle density, in kg/m
p
5 Principle
Every particle in the lot or sub-lot to be represented by the sample should have an equal probability of
being included in the sample. When this principle cannot be applied in practice, the sampler shall note
the limitations in the sampling plan.
6 Development of a sampling plan
6.1 Principle
The sampling plan shall be drawn up before the sampling takes place. Samples shall be taken
representatively from a pre-defined lot of solid recovered fuel on the basis of this sampling plan.
The sampling plan shall be drawn up on the basis of the objective for the sampling process, using
the available data on a solid recovered fuel and the accessibility of the lot. The procedure specified
in Annex A and the sampling plan presented in Annex B shall be used. Annex C provides an example
of a sampling plan. The sampling plan shall be completed. If certain estimates concerning specific
parameters relating to the lot cannot be determined with sufficient certainty on the basis of the
information available, these estimates shall be verified in the field. If necessary, the sampling plan shall
be adjusted in the field and the deviations shall be reported in the sampling record. Figure 2 shows the
actions that are necessary for the development of a sampling plan.
8 © ISO 2021 – All rights reserved

ISO 21645:2021(E)
Figure 2 — Necessary elements for the development of a sampling plan
6.2 Definition of overall objectives
The sampling plan shall specify the objectives of the sampling program through consultation with all
relevant parties. Parties that can be relevant are the client, the producer of the solid recovered fuel, the
sampler or authorities. The sampling plan shall meet the requirements of objectives.
NOTE Examples of objectives for sampling are to determine the fuel quality, to get information for processing
plant control, to estimate potential emission risks or to determine the necessary parameters for claiming
renewable energy subsidies.
The sampling plan(s) shall identify any special precautions to be followed to minimize working hazards
related to the sampling.
6.3 Definition of a lot and determining lot size
6.3.1 General
The lot shall be defined on the basis of the way in which the material is or has been produced and/or is
offered (upon delivery, upon acceptance, upon storage or in store, for instance). The lot size relates to a
quantity of material delivered on the basis of one specification and production process. This material
is agreed on by contract as a unit, and is identifiable as such. The maximum weight of a lot or sub-
lot, for sampling purposes, shall be no more than 1,5 × 10 kg. If the contracted lot weighs more than
ISO 21645:2021(E)
1,5 × 10 kg, it shall be split into two or more separate lots in order to maintain the lot size below or at
the maximum lot size. The lot definitions in 6.3.2 to 6.3.5 are possible.
NOTE It is not always necessary to sample every lot in a production period. The sampling frequency is
usually given by specific agreements with contractors and/or regulators.
6.3.2 Definition of a lot in case of sampling from a material flow
The lot shall be either defined as a period of production or as the period in which a certain amount of
solid recovered fuel is transported through the material flow.
6.3.3 Definition of a lot in case of transport by a vehicle
The total lot shall compromise the contents of the entire series of one or more vehicles used to transport
the lot. A vehicle can be both a lorry or a railway wagon.
6.3.4 Definition of a lot in case of transport by ship
The total lot shall compromise to the contents of the entire series of material with the same
specifications as agreed on in a contract of one or more ships used to transport the lot.
A lot can also relate to the quantity of material that is transported and delivered by separate
compartments in the ship and by different specifications agreed on in a contract. If one ship contains
several lots (i.e. quantities of material that differ from each other with regard to the specifications
agreed on in a contract with the producer of the material beforehand), these lots shall be stored in
separate compartments in the ship. In that case, a lot relates to the quantity of material that is
transported and delivered by separate compartments.
6.3.5 Definition of a lot in case of sampling from a static lot
If the material has been stored at the producer’s or purchaser’s premises in a store, the static lot
relates to the quantity of material with the specifications agreed on beforehand in a contract within a
demarcated area.
6.4 Determination of the sampling procedure
The applied sampling method shall result in a representative sample from the lot. Therefore, sampling
from a moving transport medium is preferred. The following sampling methods are available and
shown in the order of preference, in which the methods shall be used (i.e. representativeness of sample
decreases from top to bottom of this list):
a) mechanically from a drop flow, for which the method specified in Annex H.4 shall be used;
b) mechanically from a moving conveyor, for which the method specified in Annex H.5 shall be used;
c) manually from a stationary conveyor, for which the method specified in Annex H.6 shall be used;
d) manually from a drop flow, for which the method specified in Annex H.4 shall be used;
e) manually from a vehicle, for which the method specified in Annex I shall be used;
f) from a (temporary) store, for which the method specified in Annex I shall be used.
A less representative method shall only be chosen, if a more representative one is not possible in the
existing situation.
10 © ISO 2021 – All rights reserved

ISO 21645:2021(E)
6.5 Determination of the number of increments
The number of increments shall be at least 24.
EXAMPLE This means that for a lot size of 120 t an increment is taken on the average every 5 t and for a lot
size of 1 320 t an increment is taken on the average every 55 t.
It is possible to take more increments. Reasons for taking more increments can be:
— if more sample material is required, e.g. for duplicate analyses or as contra sample to be stored;
— if it is easier to stratify the lot in different number of strata, e.g. 5 × 5 = 25 strata.
NOTE The number of increments was fixed to 24 based on practical considerations. The main reason for this
choice is the large differences that exist between solid recovered fuels. It seemed not very practical to calculate
the number of increments for each situation before starting with sampling. More backgrounds on this choice can
[10,11]
be found in the QUOVADIS reports .
6.6 Determination of minimum sample mass
The minimum sample mass shall be determined according to the specifications in Annex E. The
minimum sample mass shall be reported in the sampling plan.
6.7 Determination of the minimum increment mass
6.7.1 Determination of minimum increment mass for material flows
If samples are taken from a material flow or from a conveyor, the minimum increment mass shall be
determined using the instructions in Annex F, in which a distinction is made between the following
situations for the purposes of determining the increment mass:
— mechanical and manual sampling from a drop flow;
— sampling from a conveyor.
NOTE For the purposes of determining the planned increment mass, no distinction is made between
mechanical sampling from a moving conveyor and manual sampling from a stationary conveyor.
6.7.2 Determination of the minimum increment mass for static lots, vehicles or ships
If samples are taken from static lots, vehicl
...