ISO 23742:2024

Test method for the evaluation of permeability and filtration efficiency distribution of bag filter medium

This document specifies a measuring method for the distribution of thickness, area mass, gas permeability and collection efficiency in the filter medium, and applies to both woven and non-woven filter medium. This document provides a method for sampling specimen (position, size and number) from the filter medium required to obtain its performance distribution accurately. The purpose of this document is to provide more accurate information about the morphology of the filter medium for users, and not to compare grade the performance of the filter medium.

Méthode d'essai pour l'évaluation de la perméabilité et de la distribution de l'efficacité de filtration d'un média filtrant à poches

General Information

• Status: Published
• Publication Date: 06-Jun-2024
• ICS: 13.040.99 - Other standards related to air quality
• ICS: 91.140.30 - Ventilation and air-conditioning systems
• Technical Committee: ISO/TC 142 - Cleaning equipment for air and other gases
• Drafting Committee: ISO/TC 142/WG 7 - Cleanable filter media used in industrial applications
• Current Stage: 6060 - International Standard published
• Start Date: 07-Jun-2024
• Due Date: 17-May-2024
• Completion Date: 07-Jun-2024

Overview

ISO 23742:2024 - Test method for the evaluation of permeability and filtration efficiency distribution of bag filter medium - specifies a standardized measuring method to determine the spatial distribution of key properties in bag filter media. It applies to both woven and non‑woven filter medium and focuses on measuring distributions (not ranking or grading products) of thickness, area mass, gas permeability and collection (filtration) efficiency. The standard also defines how to sample specimen sheets (position, size and number) to obtain accurate performance distributions.

Key topics and requirements

• Measurement scope
  • Distribution measurements for thickness, area mass, gas permeability, and optional filtration efficiency.
  • Tests produce local performance distributions rather than only average values.
• Sampling protocol
  • Sample sheets taken from at least 20 cm inside roll ends and sides; avoid selvedge.
  • Lateral spacing between sample sheets: at least 50 cm, maximum 5 sheets across a roll.
  • Minimum sample sheet size: 30 cm × 30 cm.
  • Number of sample sheets determined based on sampling theory (see Annex A) to meet required reliability.
• Specimen preparation and conditioning
  • Conditioning and testing in a standard atmosphere (referenced to ISO 139).
  • Specimen strip sizes and conditioning procedures specified to ensure comparable results.
• Measurement methods
  • Thickness measurement procedures and apparatus (see Clause 6; reference ISO 5084 for textile thickness).
  • Area mass measurement using precision balance and calibrated ruler.
  • Gas permeability testing with specified specimen holders, flow measurement and pressure instrumentation.
  • Optional filtration efficiency testing method and recommended test sequence.
• Reporting
  • Expression of distribution results and an example test report (Annexes D and E).
  • Guidance on measurement management and equipment accuracy (reference ISO 10012).

Applications and users

ISO 23742:2024 is practical for:

• Filter media manufacturers - to characterize production non‑uniformity and improve quality control.
• Baghouse and dust collector designers/operators - to predict localized performance, clogging risk and service life.
• Testing laboratories and QA/QC teams - for standardized performance mapping and reproducible test reports.
• Procurement and R&D - to compare morphological information and ensure specification compliance (note: the standard is not intended for grading different media).
• Environmental and industrial compliance teams - to better understand filtration behavior in applications like incineration, power plants, cement and metallurgical plants.

Related standards

• ISO 139 - Standard atmospheres for conditioning and testing
• ISO 5084 - Determination of thickness of textiles and textile products
• ISO 10012 - Measurement management systems - Requirements for measurement processes and measuring equipment

Keywords: ISO 23742:2024, bag filter medium, permeability distribution, filtration efficiency distribution, gas permeability, area mass, thickness measurement, sampling procedure, non‑woven filter medium.

Standards Content (Sample)

International
Standard
ISO 23742
First edition
Test method for the evaluation of
2024-06
permeability and filtration efficiency
distribution of bag filter medium
Méthode d'essai pour l'évaluation de la perméabilité et de la
distribution de l'efficacité de filtration d'un média filtrant à poches
Reference number
© ISO 2024
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
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Phone: [phone]
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Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Determination of sampling . 2
4.1 General .2
4.2 Collection position, size and shape of representative sample sheets .2
4.3 Number of representative sample sheets .2
5 Preparation of specimen strips. 3
5.1 General .3
5.2 Standard atmosphere for conditioning and testing .3
5.3 Conditioning of specimen strips .3
5.4 Size of specimen strips .3
6 Measurement method - Thickness. 4
6.1 General .4
6.2 Apparatus .4
6.2.1 Thickness tester .4
6.2.2 Thickness gauge .4
6.3 Procedure .4
7 Measurement method - Area mass . 4
7.1 General .4
7.2 Apparatus .4
7.2.1 Precision balance .4
7.2.2 Calibrated rule . .5
7.3 Procedure .5
8 Measurement method - Gas permeability. 5
8.1 General .5
8.2 Apparatus .5
8.2.1 Circular specimen holder . .5
8.2.2 Clamping device .5
8.2.3 Guard ring device . .5
8.2.4 Pressure gauge or manometer .5
8.2.5 Blower, fan or pump . .5
8.2.6 Flowmeter, volumetric counter or measuring aperture .5
8.3 Procedure .5
9 Measurement method – Filtration efficiency (option) . 6
10 Order of measurement sequence . 6
11 Expression of distribution of each measurement item . 6
12 Test report . 7
Annex A (normative) Sampling survey theory based on normal distribution . 8
Annex B (informative) Analysis example of measurement results . 9
Annex C (informative) Example of relationship between exerting pressure and thickness
distribution .13
Annex D (informative) Example of a test report . 14
Annex E (informative) Example of a test report with measurement results .16
Bibliography .18

iii
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
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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
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ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
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related to conformity assessment, as well as information about ISO's adherence to the World Trade
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This document was prepared by Technical Committee ISO/TC 142, Cleaning equipment for air and other gases.
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
Introduction
The main purpose of using dust collector systems is to separate dust particles from dirty gases. The dry
type filtering dust collectors, bag filter systems are one of the most widely used industrial dust collectors
such as municipal garbage incinerators, coal fired boilers, iron makings, cement factories, power plants,
etc. They are also used to improve the local working environment where dust is emitted. For the bag filter
systems, the operations to collect the dust particles at the surface of the filter for relatively long periods,
and to remove the accumulated dust on the filter away instantaneously are conducted. Therefore, the dust
particles are collected inside the filter immediately after the dust removal operation until the dust layer is
completely formed on the filter and particle collection on the filter surface begins. Therefore, their most
important performances, filtration efficiency and pressure drop depend upon the characteristics of the
filter medium installed in them.
Such as non-woven filter medium for bag filter systems packs densely with relatively large fibres. Although
fibre size and its orientation are different slightly in the entire filter medium, packing structure of the
medium (packing density and area mass of fibres, thickness of the medium, etc.) can vary depending on the
position of the filter medium due to the manufacturing method.
The non-uniformity (variation by the position) in the packing structure of the-medium affects its pressure
drop, gas permeability and filtration efficiency. As a result, the local values of the pressure drop, gas
permeability and filtration efficiency in small domains in the medium are also distributed unevenly.
However, the non-uniformity of these performances has been ignored. In many cases of commercial filters,
their thickness, area mass, fibre packing density, and gas permeability are only indicated as the average
specifications.
The non-uniformity of these properties of the filter medium can cause various troubles in operation and
reducing the collection performance of the bag filter system. The part with relatively lower packing density
of fibres in the filter medium allows higher gas flow rate, but the densely packed part provides lower gas
flow rate. Thus, the gas and dust flows concentrate in areas with low packing density, causing clogging in
those areas. Since the dust particles are collected inside the filter immediately after the cleaning operation of
accumulated dust on the medium until the dust layer is completely formed on the filter (transition to the cake
filtration process), the area with a relatively higher gas permeability can give the lower filtration efficiency,
and the dust easily leak from there. These phenomena finally can accelerate the further deterioration of the
filter medium.
Accordingly, in order to accurately evaluate the performance of the filter medium, it is preferable to measure
not only the average value of each property but also its distribution based on globally consistent methods
and standards.
v
International Standard ISO 23742:2024(en)
Test method for the evaluation of permeability and filtration
efficiency distribution of bag filter medium
1 Scope
This document specifies a measuring method for the distribution of thickness, area mass, gas permeability
and collection efficiency in the filter medium, and applies to both woven and non-woven filter medium.
This document provides a method for sampling specimen (position, size and number) from the filter medium
required to obtain its performance distribution accurately.
The purpose of this document is to provide more accurate information about the morphology of the filter
medium for users, and not to compare grade the performance of the filter medium.
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 139, Textiles — Standard atmospheres for conditioning and testing
ISO 5084, Textiles — Determination of thickness of textiles and textile products
ISO 10012, Measurement management systems — Requirements for measurement processes and measuring
equipment
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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
lot
minimum unit for the manufacture of a product with the same specification
3.2
roll
minimum unit for filter shipping from the manufacturer
3.3
area mass
mass per unit area for a two-dimensional object

4 Determination of sampling
4.1 General
As explained in Annex A, as the number of sample sheets increases, the accuracy of the non-uniformity
measurement improves. The number of sample sheets corresponding to the required reliability shall
be specified. Since the position of the sample sheets in the roll of the filter medium directly influences
the obtained distribution for each measurement item, it shall be specified. As the specimen strip size for
each measurement item decreases, the non-uniformity on smaller scales is measured. Hence, they shall be
specified. Since reducing the sample sheet size also yields more localized distributions with finer resolution,
it shall also be standardized.
4.2 Collection position, size and shape of representative sample sheets
Figure 1 shows the position where sample sheets are cut from the filter medium roll. Sample sheets shall be
taken from at least 20 cm inside the end and both sides of the roll of the filter medium, and avoid its selvedge.
The lateral distance between the sample sheets shall be at least 50 cm equally spaced. The maximum number
of sample sheets which are taken from a roll in the lateral direction is defined as 5. When the required
number of sample sheets are not obtained from the row closest to the end of the filter roll (first row), the
remaining sample sheets shall be taken in the same way from the next farther row, more than 20 cm apart.
The size of the sample sheet shall be more than 30 cm square (30 cm × 30 cm). All the measurement items
are tested sequentially on one specimen strip cut out from each taken sample sheet.
Dimensions in centimetres
Key
nd
1 filter roll 4 2 row
st
2 five sample sheets from one roll 5 1 row
3 less than five sample sheets from one row 6 sample sheets larger than 30 cm square
Figure 1 — Position to take sample sheets from the filter medium roll
4.3 Number of representative sample sheets
As the number of sample sheets increases, the reliability of the measured results increases, and the
confidence interval decreases. Therefore, it is preferable to collect more sample sheets and evaluate each
measurement item. However, as an increase in the number of sample sheets results in an increase in cost,
the necessary and sufficient number of sample sheets shall be determined from the sample survey theory
explained in Annex A. Namely, at least 15 sample sheets shall be sampled per lot.

The selection of filter rolls to take sample sheets from one lot is shown in Figure 2. To evaluate the
longitudinal variance, at least three rolls shall be selected evenly for each lot of the filter medium, and the
number of sample sheets allowed to be taken from a roll is limited to five, respectively.
Key
1 filter roll
2 select at least three filter rolls per lot
3 one lot
4 maximum of five sample sheets per roll (sample sheets of larger than 30 cm square)
Figure 2 — Number of sample sheets to be acquired per lot of the filter medium
5 Preparation of specimen strips
5.1 General
A specimen strip to measure all three evaluation items (thickness, area mass, gas permeability) shall be cut
out from each sample sheet taken.
5.2 Standard atmosphere for conditioning and testing
The atmosphere for conditioning and testing specimen strips shall be defined according to ISO 139. This
atmosphere has a relative humidity of (65 ± 2) % and a temperature of (20 ± 2) °C. In tropical regions
between the Tropic of Cancer (23°26'22" N) and the Tropic of Capricorn (23°26'22" S), centred on the
equator, a t
...