CEN/TR 12333:2021

SLOVENSKI STANDARD
01-november-2021
Nadomešča:
SIST CR 12333:1999
Gnojila - Določanje odpornosti granul gnojil proti drobljenju
Fertilizers - Crushing strength determination on fertilizers grains
Düngemittel - Bestimmung der Kornfestigkeit auf Düngemittelkörnern
Engrais - Détermination de la résistance à l'écrasement des engrais
Ta slovenski standard je istoveten z: CEN/TR 12333:2021
ICS:
65.080 Gnojila Fertilizers
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

CEN/TR 12333
TECHNICAL REPORT
RAPPORT TECHNIQUE
June 2021
TECHNISCHER BERICHT
ICS 65.080 Supersedes CR 12333:1996
English Version
Fertilizers - Crushing strength determination on fertilizers
grains
Engrais - Détermination de la résistance à l'écrasement Düngemittel - Bestimmung der Kornfestigkeit auf
des engrais Düngemittelkörnern

This Technical Report was approved by CEN on 23 May 2021. It has been drawn up by the Technical Committee CEN/TC 260.

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. CEN/TR 12333:2021 E
worldwide for CEN national Members.

Contents  Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Principle . 5
5 Apparatus . 5
6 Sample preparation . 6
7 Procedure . 6
8 Test report . 6
9 Statistical calculations . 7
10 Expression of results . 7
11 Conclusion . 8
Annex A (informative) Flow chart of statistical calculations . 9
Annex B (informative) Crushing strength — Interlaboratory test. 10
Annex C (informative) Crushing strength — Interlaboratory test — Outlier deleted . 11
Annex D (informative) Crushing strength — Interlaboratory test — Outlier deleted . 12
Annex E (informative) Crushing strength — Interlaboratory test — No outlier in this
grouping . 13
Annex F (informative) Crushing strength — Interlaboratory test — Outlier deleted . 14
Bibliography . 15

European foreword
This document (CEN/TR 12333:2021) has been prepared by Technical Committee CEN/TC 260
“Fertilizers and liming materials”, the secretariat of which is held by DIN.
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 CR 12333:1996.
Significant changes between this document and CR 12333:1996 are as follows:
a) 24/8/8, 13/13/21 and 0/10/20 changed to NPK 24+8+8, NPK 13+13+21 and PK 10+20,
respectively;
b) adaption to current principles and rules for structure and drafting.
The present report arises from work done by CEN/TC 260/WG 2 under the work item “Crushing strength
determination” with the view of producing a European Standard.
Unfortunately, after several ring tests, results appeared to be so randomly distributed that a statistically
significant interpretation showing good reproducibility and repeatability could not be obtained.
Tests on correlation have also shown that no significant correlation as to the causes of the dispersion of
the results could be obtained within the proposed time scale and probably not without expending too
much effort, time and money.
Therefore, since the results obtained may be added to those of past publications in the literature,
CEN/TC 260 decided the results obtained should not be ignored by the scientific community.
Introduction
The resistance to crushing (crushing strength) of fertilizer is an important property used in quality
control of fertilizer production. It influences the storage and handling as well as spreading properties of
fertilizer.
However, crushing strength of fertilizer grains is not a constant property stricto sensu. Crushing strength
is significantly influenced by the content of free water in the fertilizer, humidifying and drying during
storage, as well as by temperature changes. Time dependent processes in the grain and bulk during the
lifetime of the grains may also affect the crushing strength.
Nevertheless, there are several “in house” methods used for the measurement of crushing strength of
fertilizer grains which give different results. There is also a need for a standardized method.
This document reports the results of the international ring test, organized by CEN/TC 260/WG 2
(physical properties), carried out 1992, with the purpose of standardizing the measurement technique of
crushing strength.
1 Scope
This document is applicable to crushing strength measurement as applied to grains of fertilizer obtained
in prilling or wet-granulation process. Compacted or crystalline materials were not considered.
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 565:1990, Test sieves — Metal wire cloth, perforated metal plate and electroformed sheet — Nominal
sizes of openings
ISO 5725:1986, Precision of test methods — Determination of repeatability and reproducibility for a
standard test method by inter-laboratory tests
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 https://www.iso.org/obp
— IEC Electropedia: available at https://www.electropedia.org/
3.1
crushing strength of grains
force necessary to destroy the grain as such
4 Principle
The measurement of the force applied for the destruction of the grains may be carried out by constant
load or constant speed.
NOTE Not all manufacturers of apparatus can give information about the principle (constant speed or constant
load) used.
It is not known which of the first “peak” or maximum of force applicable on the grain is measured.
The grains undergoing the measurement were of the same size.
5 Apparatus
5.1 Sieves
The sieve is in accordance with ISO 565:1990 for the grain size chosen. In this ring test, the grain size was
2,8 mm (retained in the mesh of the sieve).

ISO 5725:1986 has been withdrawn and replaced by the ISO 5725 (series) released between 1994 and 1998.
5.2 Crushing strength measuring apparatus
In this ring test, the following apparatus as given in Table 1 were used:
Table 1
Compression speed
mm/min Direction
low high
Alvetron 10  vertical
Dinamometro Ceast 5, 10, 20  vertical
Erweka THB 28 8 38, 48, 55 horizontal
Forcemeter 10  vertical
lnstrou 4502 10 55 vertical
Matec Accuforce II 10  vertical
Mecmesin 10 55 vertical
Salter EFG-2 10 55 vertical
To investigate the influence of compression speed and/or direction of the crushing force applied, in this
ring test both low and/or high compression speed were allowed in both directions: horizontally and
vertically.
6 Sample preparation
The ring test included products with high and low elasticity. The following products or formulations have
been chosen:
Urea; AN; NPK 24+8+8; NPK 13+13+21; PK 10+20.
The test was taken with 5 × 25 = 125 grains of each formula. The grain size was d = 2,8 mm (in order to
be retained in the mesh of the sieve).
To carry ou
...