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TECHNICAL GUIDE FOR PRECISION MOULDED SEALS DESIGN. DEVELOP. IMPROVE. THE SUPER

TECHNICAL GUIDE FOR PRECISION MOULDED SEALS DESIGN. DEVELOP. IMPROVE. THE SUPERIOR TECHNICAL GUIDE We believe that this latest edition of the guide will become an invaluable resource for anyone involved in the specification and application of elastomer seals. We have not designed it to be a catalogue, but a reference to guide you through the relevant selection and design processes. It will become clear as you use the guide that we are not in the business of commodity production. Superior manufactures precision components from specialised high performance rubber compounds. As a result, we actively seek the most demanding customers. We relish involvement at the earliest point in their product development cycle. And it’s the customer who benefits most: more effective application of seals means better product design – everyone wins. To this end, we have committed to a culture of continuous, aggressive improvement in the design, manufacture and supply of precision ‘O’ rings and special mouldings. We like to exceed expectations. Innovation and Investment are the keys to this. Natural curiosity and the desire to find better processes and methodologies feeds the Superior promise to innovate. Re-investment in state-of-the-art facilities and valued, accountable people increases our ability to convert ideas into production reality. This guide is a part of that investment. Use it with confidence. It is fully backed by both our Engineering and Technical Service teams who are on hand to offer advice and support: we strongly recommend using these services as part of your design development process.You will find the contact number at the foot of each page.* *These services have been developed with you in mind. If you have any issues or comments arising from them, please contact us in the first instance. 1 THE SUPERIOR TECHNICAL GUIDE SUPERIOR SEALS WWW.SUPERIORLTD.COM 2 THE SUPERIOR TECHNICAL GUIDE SUPERIOR TECHNICAL SERVICE +44 (0)1202 854300 THE SUPERIOR TECHNICAL GUIDE CONTENTS 03 Research, Development and Partnership Consultation Testing Optimising Tooling Staying Ahead 04 Specifying Compounds Important Environmental Parameters Temperature Approvals Media Compatibility Rating Materials Reference Guide Elastomer Properties Hardness Compression Set Ageing Low Temperature Flexibility Tensile Strength Elongation Tear Strength Gas Permeability Abrasion Colour Media Table Producing an Order Specification 13 Seal Design Introduction Precision ‘O’ rings Sealing Types Groove Layouts Static Sealing – Axial and Triangular Static Axial Face Housing Static Triangular Housing Static/Dynamic Sealing – Radial ‘O’ ring Stretch in Piston Sealing Reduction of Cross-Section due to Stretch Gough-Joule Effect ‘O’ ring Size & Compound Selection Program Pressure 20 Bespoke Seal Design Precision Mouldings / Bespoke Seals Seal Integrity Seal Performance Development of a Seal Profile 22 Quality Standards Compliance ‘O’ ring Size Range Standards Quality Acceptance Criteria ISO 3601-3 Limits of Surface Imperfections Quality Control: Documentation Seal Surface Inspection Levels Special Moulding Tolerances Certification Environmental Compliance 25 Assembly, Care and Storage Fitting Aids ‘O’ ring Stretching for Assembly Cleanliness/Cleaning Materials Preparation of Housing/Mating Parts Light Humidity Contaminants Stress Temperature Oxygen and Ozone Shelf Life 28 Going Forward 3 RESEARCH, DEVELOPMENT AND PARTNERSHIP SUPERIOR SEALS WWW.SUPERIORLTD.COM RESEARCH, DEVELOPMENT AND PARTNERSHIP: A RELEVANT APPROACH TO DESIGN FOR TODAY’S MANUFACTURING CONSULTATION We actively encourage and cultivate early involvement in customer projects. This helps to ensure that the seal element is optimised within the environment demanded by the customer. This ensures that our products are reliable, fit for purpose, correctly specified with all critical features identified, controlled and costed at an appropriate and agreed level. TESTING We control all aspects of seal test and development programs closely with our customers. All testing procedures are carried out under ISO 9001 accreditation. We offer a diverse range of compounds, to satisfy the vast majority of market needs. If a customer has specific working parameters that cannot be met within our existing elastomer range, we will develop new compound grades at our in-house laboratory – even for unique needs. We are able to conduct extensive test programs to fully validate specific elastomers to customer parameters (eg, temperature/media exposure and mechanical property testing). Also we will validate to specific accreditation standards (eg, EN681, WRAS, DVGW, ACS, KIWA, NSF, EN 549). OPTIMISING Through the customer partnership exchange, we can assist with optimised seal profile design and application. TOOLING Our Tooling Manufacture Department designs and machines precision prototype and production moulds to exceed conventional tolerancing. Pilot tooling can be provided economically and rapidly to further expedite customer test programs. With our extensive tooling expertise, we can optimise critical surface features to facilitate reliable function with mating parts. STAYING AHEAD Our continuous capital investment program allows us to remain at the leading edge of our field. We continually implement latest technology systems, ensuring batch-to-batch consistency throughout the manufacturing process. With such broad customer support facilities, Superior will always strive to provide added value with our customer programs. Indeed, we find that each new project challenges our thinking and creates a springboard to increasingly enlightened manufacturing practices. Customer Service lies at the heart of everything we do at Superior. Our philosophy is based upon three key constituents: • Material Science & Technology • Seal Engineering • State-of-the-Art Manufacturing The combination of these 3 factors provides the high integrity of our precision ‘O’ rings and seals and in turn provides the long term performance and high integrity in our customers products. Our “fast response” culture is applied to each individual factor to help reduce our customers’ overall project lead time. 4 THE SUPERIOR TECHNICAL GUIDE SUPERIOR TECHNICAL SERVICE +44 (0)1202 854300 SPECIFYING COMPOUNDS IMPORTANT ENVIRONMENTAL PARAMETERS TEMPERATURE At Superior we are able to develop and manufacture the majority of elastomer compounds used in most market sectors. Awareness of specific limitations on each elastomer is fundamental, in terms of both mechanical and chemical characteristics. The most relevant influential working criteria should then be carefully matched to elastomer parameters. Only then is it possible to achieve accurate selection of the most suitable elastomer for any given environmental condition. Please refer to the Media Table on page 6. Terms and environmental aspects related to working with compounds, are highlighted in the following pages. Each elastomer type has a specific working temperature range, assuming media compatibility is optimised. All dynamic and shock loads should be avoided at temperatures below the minus limit of a given compound. However, elastomers stored in static conditions, below the low temperature flexible range, will recover full physical properties during the warm-up period. At elevated temperatures, consideration must be given to the long term running limit and the short term peak limit of each elastomer. Elastomers exposed to the extreme limit can suffer an accelerated loss of flexibility, resulting in excessive compression set. This can dramatically shorten effective sealing life. Also there is an influence in volume swell and age hardening at high temperatures, dependant on compound type. The temperature guide below is generic for each elastomer type. We have developed particular compounds which exhibit improved upper or lower temperature performance. Please consult our Technical Department. 5 SPECIFYING COMPOUNDS SUPERIOR SEALS WWW.SUPERIORLTD.COM MEDIA COMPATIBILITY RATING Virtually all elastomers exhibit a physical or chemical change when exposed to working media, whether gas or fluid. The degree of change depends upon media composition in combination with the elastomer exposed. Aggressive media become more active with subsequent increase in temperature. Physical changes become apparent in two ways and can occur simultaneously; • the elastomer absorbs a medium – creating a volume increase or swell; • a base constituent (such as plasticiser) is extracted – creating a volume decrease or shrinkage. The degree of volume change is dependant upon: • the media type; • the elastomer chemical structure; • the geometric shape of the seal (section thickness); • the stressed condition of the seal; • temperature; • time. A rubber will swell significantly less when compressed in the working envelope than in the free state (up to 50% less). Chemical changes tend to affect the cross-linking structure of the elastomer (eg, embrittlement). Any application where the media can create high shrinkage changes to the elastomer should be avoided, due to squeeze reduction and resultant leakage risk. APPROVALS We are able to develop and provide a comprehensive range of elastomers specific for; Water Industry: WRAS, NSF, DVGW, KTW, ACS, KIWA, UL Gas Industry: EN549, EN682 Compliance Food & Beverage Industry: FDA, AAA, NSF51 Pharmaceutical: USP Class XI Please consult our Technical Department for specific accreditations. 6 THE SUPERIOR TECHNICAL GUIDE SUPERIOR TECHNICAL SERVICE +44 (0)1202 854300 Material Nitrile Butyl Epichlorohydrin Polyacrylate MATERIALS REFERENCE GUIDE Designation NBR IIR ECO ACM Superior Elastomer Code MN, LN, HN,WN, FN BB ECO PA Hardness Range (IRHD) 40 – 90° 40 – 80° 50 – 80° 50 – 80° Colours Limited Range Black Limited Range Limited Range Heat Resistance °C Peak 120 130 135 150 Normal 100 110 120 135 Low Temp °C -30 -50 -20 -20 -50 low temp version Resistances Mineral Oil (low aromatic) •• x ••• ••• Oxidisation •• ••• ••• •• Ozone x ••• / •• ••• •• Weathering • ••• •• •• Radiation •• / • x •• • Integrity Tear Strength •• •• •• / uploads/Geographie/ o-ring-guide-superior.pdf