EN ISO 17829:2025

Solid biofuels - Determination of length and diameter of pellets (ISO 17829:2025)

This document specifies the methods for determination of the diameter and length of pellets. Concerning the pellet length, methods for the determination of fractions of specified lengths, such as pellets > 40 mm and particles < 10 mm and for determination of the average length are included.

Biogene Festbrennstoffe - Bestimmung der Länge und des Durchmessers von Pellets (ISO 17829:2025)

In diesem Dokument werden die Verfahren für die Bestimmung des Durchmessers und der Länge von Pellets festgelegt. Hinsichtlich der Pelletlänge sind Verfahren zur Bestimmung von Fraktionen festgelegter Längen, z. B. Pellets > 40 mm und Partikel < 10 mm sowie zur Bestimmung der durchschnittlichen Länge enthalten.

Biocombustibles solides - Détermination de la longueur et du diamètre des granulés (ISO 17829:2025)

Le présent document spécifie les méthodes permettant de déterminer le diamètre et la longueur des granulés. Pour ce qui concerne la longueur des granulés, des méthodes de détermination des fractions de longueurs spécifiées (telles que les granulés > 40 mm et les particules < 10 mm) et de détermination de la longueur moyenne sont incluses.

Trdna biogoriva - Določanje dolžine in premera peletov (ISO 17829:2025)

Ta dokument določa metode za določanje premera in dolžine peletov. V zvezi z dolžino peletov so vključene metode za določevanje deležev določenih dolžin, npr. peletov, večjih od 40 mm, in delcev, manjših od 10 mm, in za določevanje povprečne dolžine.

General Information

• Status: Published
• Publication Date: 16-Sep-2025
• ICS: 27.190 - Biological sources and alternative sources of energy
• ICS: 75.160.40 - Biofuels
• Technical Committee: CEN/TC 335 - Solid biofuels
• Drafting Committee: CEN/TC 335 - Solid biofuels
• Current Stage: 6060 - Definitive text made available (DAV) - Publishing
• Start Date: 17-Sep-2025
• Completion Date: 17-Sep-2025
• Ref Project: SIST EN ISO 17829:2025 - Solid biofuels - Determination of length and diameter of pellets (ISO 17829:2025)

Relations

• Replaces: EN ISO 17829:2015 - Solid biofuels - Determination of length and diameter of pellets (ISO 17829:2015)
• Effective Date: 18-Jan-2023

Overview

EN ISO 17829:2025 - Solid biofuels: Determination of length and diameter of pellets specifies standardized methods to measure pellet diameter and length, including procedures to determine fractions of pellets by size (for example pellets > 40 mm and particles < 10 mm) and to calculate average pellet length. Published by CEN as the European adoption of ISO 17829:2025, this edition supersedes the 2015 version and extends the scope to include detailed fraction analysis and updated measurement methods.

Key topics and technical requirements

• Scope and purpose: Defines how to determine pellet diameter class and pellet length parameters that influence bulk density, handling and combustion performance.
• Measurement principles: Describes the principle for diameter classification (linked to ISO 17225-2) and for length measurement.
• Apparatus and sample preparation: Specifies required equipment and sample preparation rules to ensure representative test portions.
• Length measurement options:
  • Option A: Using a measuring block/device designed for pellet length.
  • Option B: Using callipers to measure individual pellets.
• Fraction determination: Methods to quantify shares of pellets in specified length ranges (including coarse fines and very short particles < 10 mm) and procedures to report the proportion of pellets exceeding specified maximum lengths (e.g., > 40 mm).
• Calculations and reporting: Rules for calculating diameter class, shares of specified fractions, average pellet length, and reporting test results.
• Performance characteristics and annexes: Includes informative annexes with device designs, comparative studies between methods, and an example construction plan for a measuring block.

Practical applications and users

This standard is practical and widely used for quality control, compliance and procurement across the solid biofuels value chain:

• Pellet manufacturers: to control production, optimize pelletizing parameters and demonstrate compliance with size specifications.
• Fuel suppliers and traders: to verify delivered product meets contractual and fuel-class requirements.
• Testing laboratories and certification bodies: to perform accredited tests and produce reproducible reports.
• Boiler and burner manufacturers / plant operators: to assess fuel compatibility with feeders, conveyors, and combustion systems.
• Regulators and standards committees: for conformity assessment and alignment with ISO 17225 fuel classes.

Related standards

EN ISO 17829:2025 references and aligns with other key solid biofuel standards, including:

• ISO 17225-1 / -2 / -6 / -8 (fuel specifications and pellet classes)
• ISO 16559 (vocabulary)
• ISO 14780 (sample preparation)
• ISO 5370 (fines content)
• ISO 18135 / ISO 21945 (sampling) Use EN ISO 17829:2025 when precise, standardized measurement of pellet dimensions is required for product specification, quality assurance, or compliance with fuel classification systems.

Standards Content (Sample)

SLOVENSKI STANDARD
01-november-2025
Nadomešča:
SIST EN ISO 17829:2016
Trdna biogoriva - Določanje dolžine in premera peletov (ISO 17829:2025)
Solid biofuels - Determination of length and diameter of pellets (ISO 17829:2025)
Biogene Festbrennstoffe - Bestimmung der Länge und des Durchmessers von Pellets
(ISO 17829:2025)
Biocombustibles solides - Détermination de la longueur et du diamètre des granulés
(ISO 17829:2025)
Ta slovenski standard je istoveten z: EN ISO 17829:2025
ICS:
75.160.40 Biogoriva Biofuels
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 17829
EUROPEAN STANDARD
NORME EUROPÉENNE
September 2025
EUROPÄISCHE NORM
ICS 27.190; 75.160.40 Supersedes EN ISO 17829:2015
English Version
Solid biofuels - Determination of length and diameter of
pellets (ISO 17829:2025)
Biocombustibles solides - Détermination de la Biogene Festbrennstoffe - Bestimmung der Länge und
longueur et du diamètre des granulés (ISO des Durchmessers von Pellets (ISO 17829:2025)
17829:2025)
This European Standard was approved by CEN on 12 September 2025.

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, Türkiye 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
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 17829:2025 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 17829:2025) has been prepared by Technical Committee ISO/TC 238 "Solid
Biofuels and Pyrogenic Biocarbon" in collaboration with Technical Committee CEN/TC 335 “Solid
Biofuels and Pyrogenic Biocarbon” the secretariat of which is held by SIS.
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 2026, and conflicting national standards shall
be withdrawn at the latest by March 2026.
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 17829:2015.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
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, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 17829:2025 has been approved by CEN as EN ISO 17829:2025 without any modification.

International
Standard
ISO 17829
Second edition
Solid biofuels — Determination of
2025-09
length and diameter of pellets
Biocombustibles solides — Détermination de la longueur et du
diamètre des granulés
Reference number
ISO 17829:2025(en) © ISO 2025
ISO 17829:2025(en)
© ISO 2025
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: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
ISO 17829:2025(en)
Contents Page
Foreword .iv
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus . 2
6 Sample preparation . 4
6.1 General .4
6.2 Preparation requirements for pellet diameter .4
6.3 Preparation requirements for pellet length and pellet length fractions .4
7 Procedure . 4
7.1 Determination of the parameters to be analysed .4
7.2 Determination of the pellet diameter class .5
7.3 Measuring the length of an individual pellet .5
7.3.1 General .5
7.3.2 Option A: Measuring the length of an individual pellet with a measuring block
(5.2) .5
7.3.3 Option B: Measuring the length of an individual pellet with a calliper.6
7.4 Determination of the number of pellets above a maximum length .6
7.5 Determination of the share of pellets > 40 mm and the length of the longest pellet.6
7.6 Determination of the share of pellets of any other specified length, including pellets
< 10 mm .7
7.7 Determination of the average length of pellets .7
8 Calculations . 7
8.1 Pellet diameter class .7
8.2 Share of a specified fraction of pellets .7
8.2.1 General .7
8.2.2 Share of fractions including coarse pellet fines .8
8.2.3 Share of pellets > 40 mm .8
8.3 Average pellet length .9
9 Performance characteristics . 9
10 Test report . 9
Annex A (informative) Devices for the determination of the length of pellets with a diameter of
8 mm or above . .11
Annex B (informative) Comparative studies for determination of the pellet length .13
Annex C (informative) Example of a construction plan for a measuring block .15
Bibliography .18

iii
ISO 17829:2025(en)
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
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 238, Solid Biofuels and Pyrogenic Biocarbon, in
collaboration with the European Committee for Standardization (CEN) Technical Committee CEN/TC 335,
Solid Biofuels and Pyrogenic Biocarbon, in accordance with the Agreement on technical cooperation between
ISO and CEN (Vienna Agreement).
This second edition cancels and replaces the first edition (ISO 17829:2015), which has been technically
revised.
The main changes are as follows:
— extended scope which now includes the determination of specified pellet length fractions;
— description of a procedure to determine fractions of specified length including particles < 10 mm;
— added definition of pellet length;
— modified drawings for measuring pellet length;
— changed sizes of the test portions for the determination of the pellet length and fractions of specific
length including pellets > 40 mm;
— changed procedures for measuring pellet length with two options: using a device for measuring the
pellet length or a calliper;
— added measurement and reporting of the length of the longest pellet if pellets over 40 mm are found
— added informative annex with a device for measuring the length of pellets with other diameters than 6 mm;
— added informative annex with comparing data for the determination of pellet length with different methods
— added informative annex with an example of a building plan for a measuring block
— updated references;
iv
ISO 17829:2025(en)
— modified drawings of pellet length to avoid potential ambiguity.
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.

v
ISO 17829:2025(en)
Introduction
Pellets with a length and diameter outside the specification can cause problems with transportation in screw
conveyors, silo outlets, and burner feeding systems. ISO 17225-1, ISO 17225-2, ISO 17225-6, and ISO 17225-8
stipulate the dimensions of pellets. The average pellet length and the amount of pellets of specific size
fractions can influence the bulk density and the combustion behaviour.
This document describes procedures for determining the diameter class according to ISO 17225-2 as well as
the length and diameter of pellets and the shares of specified pellet length fractions.

vi
International Standard ISO 17829:2025(en)
Solid biofuels — Determination of length and diameter of pellets
1 Scope
This document specifies the methods for determination of the diameter and length of pellets. Concerning
the pellet length, methods for the determination of fractions of specified lengths, such as pellets > 40 mm
and particles < 10 mm and for determination of the average length are 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 3310-2, Test sieves — Technical requirements and testing — Part 2: Test sieves of perforated metal plate
ISO 5370, Solid biofuels — Determination of fines content in pellets
ISO 14780, Solid biofuels — Sample preparation
ISO 16559, Solid biofuels — Vocabulary
ISO 17225-1, Solid biofuels — Fuel specifications and classes — Part 1: General requirements
ISO 17225-2, Solid biofuels — Fuel specifications and classes — Part 2: Graded wood pellets
ISO 17225-6, Solid biofuels — Fuel specifications and classes — Part 6: Graded non-woody pellets
ISO 17225-8, Solid biofuels — Fuel specifications and classes — Part 8: Graded thermally treated and densified
biomass fuels for commercial and industrial use
ISO 18135, Solid Biofuels — Sampling
ISO 21945, Solid biofuels — Simplified sampling method for small scale applications
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 16559 and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
pellet length
distance from endpoint to endpoint along the pellet axis
Note 1 to entry: Before measuring the pellet length, the coarse pellet fines (fraction of particles between 3,15 mm and
5,6 mm) are removed by sieve according to ISO 5370. For determination of the average pellet length, this fraction is not
considered. For the determination of specific size fractions, the coarse pellet fines is included as mass fraction.

ISO 17829:2025(en)
4 Principle
The diameter of fuel pellets (see Figure 1) of a representative test sample is measured by means of a calliper.
Measuring the pellet length along the axis of pellets is done with an apparatus as described in 5.2 (Option
A) or with a calliper as described in 5.1 (Option B). The method for length measurement enables the user to
determine the share of pellets in specified length classes such as pellets longer than 40 mm or shorter than
10 mm. Furthermore, the average length of pellets can be determined.
a) Idealized pellet shape b) Typical pellet shape
Key
D diameter of a pellet, in mm
L length of a pellet, in mm
Figure 1 — Length and diameter of a pellet
Automatic equipment for the determination of the pellet length may be used when the method is validated
with biomass reference samples of adequate biomass pellets. The automatic equipment shall fulfil all
requirements concerning sample size for length determination given in 7.1.
5 Apparatus
5.1 Calliper as shown in Figure 2 shall have a readability of at least 0,1 mm to be used for the measurement
of the pellet length (Option B) and the pellet diameter.
For easier handling a digital calliper is recommended. If technically possible, the digital calliper may be
connected to a computer to avoid manual recording of the data.
Figure 2 — Example of a digital calliper
5.2 Measuring block with a built-in calliper and metal pin elements (Option A for pellet length
measurement). The metal block (A) has a groove (D) for holding the pellets to be measured (see Figure 3).
The groove has an angle of 90° and shall be deep enough to keep the pellet properly in the correct direction
along the groove.
ISO 17829:2025(en)
a) Top view b) Cross section
Key
A metal block
B fixing plate (to hold the metal pin element)
C metal pin elements, 7 mm diameter
D groove in the metal block
E connecting plate (between metal pin element and built-in calliper)
F digital measuring unit of the calliper
G built-in calliper, min. 100 mm measuring range
Figure 3 — Example of a measuring block with a mounted digital built-in calliper and metal pin
[1]
elements for 6 mm pellets
Two metal pin elements (C) with a diameter of (7 ± 0,1) mm (see Figure 3) are placed in the groove of the
measuring block, and both ends of each metal pin element are cut flat perpendicular to the axis of the pin
element.
One of the metal pin elements is connected to a built-in calliper, readable to the nearest 0,1 mm, by a metal
plate (E) in such a way, that it slides easily in the groove and the measuring unit of the mounted calliper
(F) can be moved freely as well. The connecting plate should be fixed at the metal pin element and at the
measuring unit with screws to enable the change of the metal pin elements. Depending on the depth of the
groove in the measuring block it can be necessary, to flatten the rear part of the metal pin element in order to
attach it to the connecting plate in such a way that free movement of these parts is ensured (see Figure A.2).
The second metal pin element (C) is placed at the end of the groove where the scale of the mounted calliper
starts. It is fixed at the metal block by screws to enable the change of the metal pin element.
For easier handling, a digital built-in calliper is recommended. If technically possible, the digital calliper may
be connected to a computer to avoid manual recording of the data.
In case of using a non-digital built-in calliper, it shall be placed in such a way that the scale shows “0 mm”
when both metal pin elements are pushed together completely. Alternatively, the offset shall be recorded
and taken into consideration when reporting the me
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