“Press-fit” fitting systems and ... - Stainless steel

1 Press- fit fitting systems and Stainless steel Materials and Applications Series, Volume 19. P r ess - f it f ittin g s y stems an d stain l ess stee l Euro Inox Euro Inox is the European market development asso- Full members ciation for Stainless steel . Members of Euro Inox Acciai Speciali Terni include: European Stainless steel producers;. Acerinox national Stainless steel development associations;. development associations of the alloying element industries. Aperam The prime objectives of Euro Inox are to create aware- ness of the unique properties of Stainless steel and Outokumpu to further its use in existing applications and in new markets. To achieve these objectives, Euro Inox Outokumpu Nirosta organises conferences and seminars and issues guid- ance in printed and electronic form, to enable archi- tects, designers, specifiers, fabricators and end users Associated members to become more familiar with the material.

2 Euro Inox Acroni also supports technical and market research. British Stainless steel Association (BSSA). Cedinox Centro Inox ConstruirAcier Industeel Informationsstelle Edelstahl Rostfrei International Chromium Development Association (ICDA). International Molybdenum Association (IMOA). Nickel Institute Polska Unia Dystrybutor w Stali (PUDS). SWISS INOX. ISBN 978-2-87997-371-5 P r ess - f it f ittin g s y stems an d stain l ess stee l Contents Press- fit fitting systems and Stainless steel 1 Introduction 2. First edition 2012 2 The principle 4. (Materials and Applications Series, Volume 19) 3 Comparison with alternative techniques 5. Euro Inox 2012 4 Relevant material properties 7. Self-passivation 7. Work hardening 7. 5 Applications 8. Publisher Plumbing 8. Euro Inox Vertical distribution 9. Diamant Building, Bd. A. Reyers 80 Horizontal distribution 9. 1030 Brussels, Belgium Grades of Stainless steel for plumbing 10.

3 Phone: +32 2 706 82 67 Tube for contact with drinking water 10. Fax: +32 2 706 82 69 Mixed-material plumbing installations 11. E-mail: Heating 12. Solar panels 13. Author Process water and chilled water 14. Thomas Pauly, Brussels (B) Fire extinguishing systems 14. Drainage 14. Acknowledgements Mineral oil products and chemicals 15. The author wishes to thank Mr. Tony Newson, Gaseous fuels 15. Rotherham (UK) and Dr. Hubertus Schlerkmann, Compressed air 16. Salzgitter-Mannesmann Forschung GmbH, Duisburg Other gases 16. (D) for their input and critical reading of the draft. Electrical installation 16. 6 General recommendations for installation 17. Cover photos Exposure to chlorides 17. Cover photos: Geberit, Jona (CH), left Cutting and bending 18. Nussbaum, Olten (CH), right 7 Summary 19. 8 Bibliography 20. Copyright notice This work is subject to copyright. Euro Inox reserves all rights of translation in any language, reprinting, re-use of illustrations, recitation and broadcasting.

4 Disclaimer No part of this publication may be reproduced, stored Euro Inox has made every effort to ensure that the in a retrieval system or transmitted in any form or by information presented in this document is technically any means, electronic, mechanical, photocopying, correct. However, the reader is advised that the recording or otherwise, without the prior written per- material contained herein is for general information mission of the copyright owner, Euro Inox. Violations purposes only. Euro Inox and its members, specifically may be subject to legal proceedings, involving mon- disclaim any liability or responsibility for loss, dam- etary damages as well as compensation for costs age or injury, resulting from the use of the information and legal fees, under Luxembourg copyright law and contained in this publication. regulations within the European Union. 1. P r ess - f it f ittin g s y stems an d stain l ess stee l 1 Introduction The press-fit fitting technique ideally known for its use in domestic plumbing, meets a number of key requirements for its potential areas of application are much tube systems conveying drinking water, wider and include process water, petroleum process water, other liquids or gases: ease products and gas.

5 And speed of installation, combined with long-term reliable service. Potable water re- The present publication outlines quires the utmost neutrality of the material the main technical properties of Stainless to ensure public health and that neither the steel press-fit connections colour nor the taste of the water is changed. its competitive position in the context of For process liquids, the potential corrosive alternative solutions influence of the product has to be taken into typical areas of application account. For gaseous media, gas tightness aspects of design and installation that can be safety-critical. are specific to Stainless steel . Mechanical fitting systems are available for a number of metallic materials. However, the outstanding formability of Stainless steels and their proven neutrality make the press-fit fitting system , on the one hand, and Stainless steel , on the other, a dream team.

6 While this constellation is best The Stainless steel press-fit fitting system combines ease of instal- lation with the proven neutrality of Stainless steel . Photo: Chibro, Montano Lucino, CO (I). 2. P r ess - f it f ittin g s y stems an d stain l ess stee l At a glance: Why Stainless steel ? Corrosion resistant to any allowable European drinking water composition without restrictions Corrosion resistant to other fluids including many types of process water, min- eral oil products and gaseous fuels Corrosion resistant outer surface for use in aggressive atmosphere (brewer- ies, dairy ). High resistance against erosion corrosion Visually attractive contributes to a visual impression of cleanliness Lower thermal expansion than most alternative materials Exceptionally durable Proven hygienic properties, right from the start No ageing; insensitive to UV radiation when exposed to daylight Also available as flexible composite tubes with a Stainless steel inner lining Why press-fit fittings?

7 Exceptionally fast joining method Reach their full structural integrity immediately No heat input, no fire hazard Multi-purpose technique: one principle for the most diverse types of liquids and gases Illustration: Sanha Kaimer, Essen (D). 3. P r ess - f it f ittin g s y stems an d stain l ess stee l 2 The principle The exact geometry of mers for these sealing components, which the section may vary must provide a level of durability that is con- from one system to an- other and also depend- sistent with the useful life of the Stainless ing on the dimensions. steel . The O ring must be made of a mater- Illustration: Raccorderie ial that is resistant to the media to be con- Metalliche, Campitello di veyed. For instance, different types of rings Marcaria (MN), (I). are used for water, petroleum products or natural gas. Some manufacturers use colour The term press-fit refers to a joining codes for different categories of seal rings method for tube systems by means of fit- to avoid errors.

8 The manufacturers provide tings, which are mechanically pressed with suitable product ranges for each of the vari- specific tools. The pressing operation leads ous applications. Reassuring long-term ex- to a mechanical joint between the tube and perience has now been available for more the fitting . Hydraulic tightness is achieved than 40 years. by the O-ring- system . Its high ductility is the reason why Stainless steel is particularly suitable for this tech- nique. The geometry of the fitting and the section of the compressed area vary from one manufacturer to another. Therefore, the (interchangeable) jaws of the power tools must be approved by the manufacturer of the fittings. Press tools are available Additionally, an elastomer O ring is em- in electro-hydraulic and bedded in the fitting . Considerable research electromechanical (in- was carried out to identify and test poly- cluding battery-powered).

9 Versions. Photo: Viega, Attendorn (D). The press tool must match the geometry of the fitting . Photo: Sanha Kaimer, Essen (D). 4. P r ess - f it f ittin g s y stems an d stain l ess stee l 3 Comparison with alternative techniques As a fully mechanical type of joints, press- fit connections are produced at ambient temperature and any fire risk is avoided. Photo: Geberit, Jona (CH). In professional plumbing and heating instal- Press-fit connections for metallic materials lation practice, the brazing of copper has are time-saving and safe: been a classic joining method. Its limita- The operation is performed at ambi- tions include the use of open flames, which ent temperature. There is no risk of fire, can involve fire risks, specifically in the re- even if the tube is laid close to (or even novation of buildings, where flammable ma- in) flammable materials, in historic terials may be close to the working area.

10 The buildings. retrofitting of modern heating installations The compression process is fast: it takes in listed buildings is a typical case. The just a few moments. Depending on the selection and use of solder and appropri- tube diameter, it can be as short as 3. ate flux are critically important. The joining seconds. Contractors report reductions process is relatively slow, requiring experi- of time-related installation cost between ence and skill. The joints are only mech- 25 % and 40 %. Studies point out that anically sound when they have cooled off. the cost benefit is particularly marked in large-diameter systems . Plastic tubes are available as an alternative. The joints immediately reach their final The connections are adhesively bonded, mechanical stability. which avoids the complexity and fire risks of the brazing process. Limitations for profes- sional users lie in the fact that the adhesives need time to cure.