ISO/PRF 29461-1

Air intake filter systems for rotary machinery -- Test methods

Systèmes de filtration d'air d'admission pour machines tournantes -- Méthodes d'essai

General Information

• Status: Published
• ICS: 29.160.99 - Other standards related to rotating machinery
• Technical Committee: ISO/TC 142 - Cleaning equipment for air and other gases
• Drafting Committee: ISO/TC 142/WG 9 - Particulate air filter intake systems for rotary machinery and stationary internal combustion engines

RELATIONS

• Revised: ISO 29461-1:2013 - Air intake filter systems for rotary machinery -- Test methods
• Effective Date: 23-Apr-2020

Standards Content (sample)

INTERNATIONAL ISO
STANDARD 29461-1
Second edition
Air intake filter systems for rotary
machinery — Test methods —
Part 1:
Static filter elements
Systèmes de filtration d'air d'admission pour machines tournantes —
Méthodes d'essai —
Partie 1: Éléments filtrants pour filtres statiques
PROOF/ÉPREUVE
Reference number
ISO 29461-1:2021(E)
ISO 2021
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ISO 29461-1:2021(E)
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ISO 29461-1:2021(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Symbols and abbreviated terms ........................................................................................................................................................... 2

5 Testing and classification of filter efficiencies ...................................................................................................................... 2

6 Determination of the air flow resistance versus the mass of test dust captured ..............................4

7 Conditioning method to determine the minimum fractional test efficiency .........................................5

8 Reporting ...................................................................................................................................................................................................................... 5

Annex A (normative) Net area calculation ..................................................................................................................................................... 7

Bibliography .............................................................................................................................................................................................................................15

© ISO 2021 – All rights reserved PROOF/ÉPREUVE iii
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ISO 29461-1:2021(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 142, Cleaning equipment for air and other

gases, in collaboration with the European Committee for Standardization (CEN) Technical Committee

CEN/TC 195, Cleaning equipment for air and other gases, in accordance with the Agreement on technical

cooperation between ISO and CEN (Vienna Agreement).

This second edition cancels and replaces the first edition (ISO 29461-1:2013), which has been technically

revised.
The main changes compared to the previous edition are as follows:

— a new test method, referring to ISO 16890 (all parts) and ISO 29463 (all parts), has been added;

— a classification table has been added;

— previous Annexes A, B, C and D have been deleted; previous Annex E has become Annex A.

A list of all parts in the ISO 29461 series can be found on the ISO website.

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.
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ISO 29461-1:2021(E)
Introduction

In rotating machinery applications, the filtering systems, typically a set of filter elements arranged in

a suitable manner, are an important part of the whole turbine/compressor system. The development

of turbine machinery used for energy production or others has led to more sophisticated equipment;

and therefore the importance of good protection of these systems has become more important in the

recent years. It is known that particulate contamination can deteriorate a turbine power system quite

substantially if not taken care of.

This event is often described as “erosion”, “fouling” and “hot corrosion” where salt and other corrosive

particles are known as potential problems. Other particulate matters can also cause significant

reduction of efficiency of the systems. It is important to understand that air filter devices in such systems

are located in various environmental conditions. The range of climate and particulate contamination is

very wide, ranging from deserts to humid rain forests to arctic environments. The requirements on

these filter systems are obviously different depending on where they will be operating.

ISO 29461 (all parts) has based the performance of the air intake filter systems not only upon heavy

dust collection but also particulate efficiency in a size range that is considered to be the problematic

area for these applications. Both ultra-fine and fine particles, as well as larger particles, should be

considered when evaluating turbine fouling. In typical outdoor air, ultra-fine and fine particles in the

size range from 0,01 μm to 1 μm contribute to > 99 % of the number concentration and to > 90 % of the

surface contamination. The majority of the mass normally comes from larger particles (>1,0 μm).

Turbo-machinery filters comprise a wide range of products from filters for very coarse particles to

filters for very fine, sub-micron particles. The range of products varies from depth to surface loading

systems, which can be regenerated e.g. by pulse cleaning. The filters and the systems have to withstand

a wide temperature and humidity range, very low to very high dust concentration and mechanical

stress. The shape of products existing today can be of many different types and have different functions

such as droplet separators, coalescing products, filter pads, metal filters, inertial filters, filter cells,

bag filters, panel-type, cleanable and depth loading filter cartridges and pleated media surface filter

elements.

ISO 29461 (all parts) provides a way to compare these products in a similar way and define what

criteria are important for air filter intake systems for rotary machinery performance protection.

The aim is to compare different filters and filter types with respect to the operating conditions they

finally will be used in. For instance, if a filter or a filter system is meant to operate in an extreme, very

dusty environment, the real particulate efficiency of such a filter cannot be predicted because the dust

loading of the filter plays an important role. A further part of ISO 29461 will address the performance

of cleanable and surface loading filters. Filters in turbo-machinery applications can also face very harsh

operating conditions such as high air flow rates or water and salt ingress. Further parts of ISO 29461

will address the performance of filters under such harsh conditions.
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INTERNATIONAL STANDARD ISO 29461-1:2021(E)
Air intake filter systems for rotary machinery — Test
methods —
Part 1:
Static filter elements
1 Scope

This document specifies methods and procedures for determining the static performance of particulate

air filters used in air intake filter systems for rotary machinery such as stationary gas turbines,

compressors and other stationary internal combustion engines. It applies to air filters with an efficiency

of 85 % or more for the MPPS (EPA and HEPA filters) which are tested according to ISO 29463 (all parts)

and filters with a lower efficiency which are tested according to ISO 16890 (all parts). The procedures

described in both ISO 16890 (all parts) and ISO 29463 (all parts) are applied and extended by this

3 3

document to air filters which operate at flow rates within the range 0,24 m /s (850 m /h) up to

3 3
2,36 m /s (8 500 m /h).

Static filter systems normally use multiple stages of coarse, fine and optional EPA or HEPA filter elements

to protect the machinery. The scope of this document includes methods for performance testing of

individual filter elements. It does not include methods for the direct measurement of the performance

of entire systems as installed in service except in cases where they can meet the qualification criteria

for the test assembly. Nevertheless, cumulative filter efficiencies of multistage systems of fine filters

can be calculated by using the methods described in ISO 16890-1.

This document refers to static (barrier) filter systems but can also be applied to other filter types and

systems in appropriate circumstances, for example to evaluate the initial efficiency of cleanable and

surface loading filters.

The performance results obtained in accordance with this document cannot be quantitatively applied

(by themselves) to predict performance in service with regard to efficiency and lifetime.

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 15957, Test dusts for evaluating air cleaning equipment
ISO 16890 (all parts), — Air filters for general ventilation

ISO 29463 (all parts), — High efficiency filters and filter media for removing particles from air

ISO 29464, Cleaning of air and other gases — Terminology
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 29464 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
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ISO 29461-1:2021(E)
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
EPA filter
efficient particulate air filter

filters with performance complying with requirements of filter class ISO T10 to ISO T12 as per this

document
Note 1 to entry: EPA filters cannot be and shall not be leak tested.
3.2
initial gravimetric arrestance
100

ratio of the mass of a standard test dust retained by the filter to the mass of dust fed after the first 100 g

of dust load
Note 1 to entry: This measure is expressed as a weight percentage.
4 Symbols and abbreviated terms

For the application of this document, the following symbols and abbreviated terms apply:

ePM Minimum efficiency value with x = 1 µm, 2,5 µm or 10 µm of the conditioned filter element,

x, min
% (see ISO 16890-1)
ePM Efficiency with x = 1 µm, 2,5 µm or 10 µm, % (see ISO 16890-1)
MPPS Most penetrating particle size
5 Testing and classification of filter efficiencies

Filters with an efficiency of 85 % or more for the MPPS (EPA and HEPA filters) shall be tested

according to ISO 29463 (all parts), while filters with a lower efficiency shall be tested according to

ISO 16890 (all parts). Filters are classified in groups and classes based on their efficiency as defined in

Table 1.

NOTE For the classification of ISO ePM and ISO ePM filters only the ePM values are used.

1 2,5 x, min

HEPA filters (class T13) shall be individually tested and their efficiency determined at MPPS according

to ISO 29463-5. Filters shall be individually leak tested according to ISO 29463-4 where, in addition to

the reference leak scan method, four alternate methods for leak testing are allowed. For HEPA filters

with geometries which do not allow a scan testing, like e.g. cartridges or V-bank filters, the oil thread

test method or one of the other suitable (non-scanning) methods described in ISO 29463-4 can be

applied. Alternate norms used for leak testing should be clearly identified on the filter and certifications.

In order to extent the volume flow rate and the range of filter geometries (e.g. cylindrical filters),

deviations and extensions to the test rig defined by ISO 16890-2 and ISO 29463-5, respectively, are

described below.

The test rig consists of several square duct sections with typical 610 mm × 610 mm nominal inner

dimensions except for the section where the filter is installed. This section has nominal inner

dimensions between 616 mm and 622 mm. The length of this duct section shall be at least 1,1 times

the length of the filter, with a minimum length of 1 m as shown in Figure 1 (for more details on the test

rig see ISO 16890-2). The filter shall be within the section and shall not protrude out of this section,

either upstream or downstream. The test duct may need to have larger dimensions in cases when very

large filters or integrated filter-system-element are to be tested. In those cases, other dimensions are

allowed as long as the qualification procedures described in ISO 16890-2 are fulfilled. An example of a

special (large) filter transition can be seen in Figures 2 and 3.
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ISO 29461-1:2021(E)
Table 1 — Filter classification
ISO 29463
Class Group ISO 16890 (all parts)
(all parts)
MPPS efficien- Initial gravimetric
ePM ePM ePM
1, min 2,5, min 10
cy arrestance A
100
ISO T1 20 % < A < 50 %
100
ISO T2 ≥ 50 %
Coarse
ISO T3 ≥ 70 %
ISO T4 ≥ 85 %
ISO T5 ePM ≥ 50 %
ISO T6 ePM ≥ 50 %
2,5
ISO T7 ≥ 50 %
ISO T8 ePM ≥ 70 %
ISO T9 ≥ 85 %
ISO T10 ≥ 85 %
ISO T11 EPA ≥ 95 %
ISO T12 ≥ 99,5 %
ISO T13 HEPA ≥ 99,95 %

In case of circular cartridges, the test setup (mounting of the filters in the test duct) shall be as close

to the real application as possible. In cases of large cylinders, a mounting plate with an additional hole

for the air inlet/outlet can be sufficient (see Figure 4). In terms of much smaller cylinders an additional

transition could be inserted in the du
...