National foreword

This British Standard is the UK implementation of EN ISO 29461‑4:2025. It is identical to ISO 29461‑4:2025.

The UK participation in its preparation was entrusted to Technical Committee MCE/21, Filters for gases and liquids.

A list of organizations represented on this committee can be obtained on request to its committee manager.

Contractual and legal considerations

This publication has been prepared in good faith, however no representation, warranty, assurance or undertaking (express or implied) is or will be made, and no responsibility or liability is or will be accepted by BSI in relation to the adequacy, accuracy, completeness or reasonableness of this publication. All and any such responsibility and liability is expressly disclaimed to the full extent permitted by the law.

This publication is provided as is, and is to be used at the recipient’s own risk.

The recipient is advised to consider seeking professional guidance with respect to its use of this publication.

This publication is not intended to constitute a contract. Users are responsible for its correct application.

Compliance with a British Standard cannot confer immunity from legal obligations.

This British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 April 2025.

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 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).

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.

Introduction

The use of gas turbines in the oil and gas industry represents one of the most challenging applications for this engine technology. The major constraint of the oil and gas industry is to run 24/7 at full load with minimum downtime. In oil and gas activity, the installation must be run as close as possible to 100 % of the time with the highest level of efficiency (current production compared to nominal production).

An additional challenge for oil and gas applications lies in the absence of a back-up turbine on site, especially for mechanical-drive gas turbine configurations.

The coastal and offshore environment probably represents the harshest conditions for gas turbines. Humidity, rainfall and seasonal dust are the most obvious visible conditions that operators face on site. Hidden in the combustion air, alkali such as potassium, sodium or magnesium, as well as sulfur, soot, volatile hydrocarbons, oily vapours, and particles all generate gas turbine issues including compressor fouling, air-cooling passage fouling, vane and blade erosion, and compressor corrosion. Combined with sulfur in fuels, these alkali in combustion air create hot corrosion. Finally, heavy rainfall can induce filter washings that release filtered particles into the compressor. All these phenomena impact the gas turbine availability on site.

The role of a highly efficient air filtration system is to maintain the engine cleanliness by preventing the introduction of contaminants into the gas turbine air intake. Achieving a high level of engine cleanliness helps maintain engine integrity and efficiency and reduces the need for water washes which generate avoidable downtime.

Currently, high efficiency filter elements are characterized by a limited number of parameters, namely filter efficiency and most penetrating particle size (MPPS). These parameters, related to a single filter element, are measured in laboratory conditions close to favourable inland conditions with synthetic dust. Consequently, these conditions are far from the reality observed on site, offshore or near coast, where filter elements are usually part of a system. The test results do not therefore provide a basis for predicting either operational filter performance or service life.

The objective of this document is to consider how the effect of water spray, humidity and salt affects the performance of an air filter. The tested air flow passing through the filter element is close to the air flow rate operated on site for the three different concepts: low, medium or high velocity filter elements.

Soot, volatile hydrocarbons, oily vapours and particles also have impact on filter characterization and performance. The separate parts of ISO 29461 cover particles, while soot, volatile hydrocarbons and oily vapours are yet to be addressed. Current test methods are not mature enough for the inclusion of soot, volatile hydrocarbons and oily vapours.

The ageing of a filter element installed offshore and near the coast is addressed to allow the prediction of operational filter performance and its associated service life. It must be understood how filter elements perform during different cycles representing typical site conditions such as heavy rainfall, low and high humidity, filter element unloaded and loaded.

Depending on the gas turbine applications, the service life of the filter element is also a criterion to take into consideration. In this case, the robustness, loading capacity and pressure drop characteristics of the filter elements become key parameters for design and testing.

This European Standard was approved by CEN on 28 March 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, Czechia, 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 foreword

This document (EN ISO 29461‑4:2025) has been prepared by Technical Committee ISO/TC 142 "Cleaning equipment for air and other gases" in collaboration with Technical Committee CEN/TC 195 “Cleaning equipment for air and other gases” the secretariat of which is held by UNI.

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 2025, and conflicting national standards shall be withdrawn at the latest by October 2025.

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.

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 29461‑4:2025 has been approved by CEN as EN ISO 29461‑4:2025 without any modification.

1 Scope

This document defines test methods for performance testing of individual filter elements and of the complete filtration system.1

This procedure is intended for filter elements and filter systems which operate at flow rated up to 8 000 m³/h per filter element.

2 Normative references

3 Terms and definitions

3.1 Air flows

3.2 Efficiencies

4 Symbols and abbreviated terms

5 Principle

6 Test rig and equipment

6.1 Test rig

6.2 Test duct

6.3 Measurement equipment

6.4 Solid salt aerosol sampling

6.5 Solid salt aerosol generation

6.6 Water spray device

6.7 Water collection device

7 Qualification of test rig and apparatus

7.1 Pressure system testing

7.2 Solid salt aerosol uniformity

8 Test conditions

8.1 Test air

8.2 Test water

9 Test method

9.1 Stop criteria

9.2 Adjustment of the test air flow rate

9.3 Preparatory checks

9.4 Measurements

10 Test procedure

10.1 Preparation of test rig (no test object installed)

10.2 Cleaning of test rig

10.3 Primary weighing of the test object

10.4 Installation of the test object

10.5 Primary water deluge challenge

10.6 Salt loading

10.7 Water deluge challenge

10.8 Relative humidity cycles

10.9 End of test

10.10 Secondary weighing of the test object

11 Reporting results

11.1 General

11.2 Observations

11.3 Report template

Bibliography

BS EN ISO 29461-4:2025

Air intake filter systems for rotary machinery - Test methods for static filter systems in coastal and offshore environments

Current

Published:

30 Apr 2025