Sealing technology manual for the process industry

Applications O-rings are utilized in numerous applications and in nearly all industries. An overview of the primary applications is given below. • Static cover seals, axial sealing • Static piston or rod seals, radial sealing • Dynamic seals involving translatory movement (hydraulic or pneumatic) • Dynamic seals involving rotation • Valve seals • Flange seals THE ADVANTAGES AT A GLANCE • Can be used universally • Available in all dimensions • Available in all types of elastomer • Easy to install and assemble • Good price-performance ratio • Small installation space DESIGN NOTES General The design of O-ring sealing systems (groove, sealing surface) is described in the relevant standards (e.g. DIN 3771 and DIN ISO 3601-1) Compression Depending on the application, the following benchmarks apply for standard cases (compression in % of the cross-section diameter): • Static seals: 15 – 30% • Dynamic seals - hydraulic: at least 6% • Dynamic seals - pneumatic: 2 – 6% Degree of groove fill • In standard applications there is the rule that the O-ring volume is 70 – 90% of the groove volume • It should be kept in mind that the elastomer is more susceptible to thermal expansion than the metal housing • Applications in the food and beverage industry must be leak-free. The degree of groove fill can be more than 100%; specialized types of grooves should be utilized Elongation • Max. 6% in constant use • Max. 25% of the elongation at break cited in the data sheet when assembled • In the case of greater elongations, corresponding elastic recovery time should be taken into account Compression strain Max. 3% after installation, otherwise risk of deformation and shearing during installation Gap widths and surfaces • The acceptable gap widths and surface qualities depend on the material’s hardness rating and the operational parameters. Standard values can be found in the relevant standards (e.g. DIN 3771 and DIN ISO 3601-1) • Attention: In dynamic applications involving plastic housings, the friction heat can result in localized overheating • In dynamic applications or those involving pulsating pressures, no plastics reinforced with glass fibers should be used since otherwise extensive wear will occur APPENDIX PRODUCT PORTFOLIO MATERIALS RESISTANCE & PURITY ENGINEERING PLASTICS ELASTOMERIC MATERIALS TECHNICAL FUNDAMENTALS INTRODUCTION 67

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