BS 4518 is a British Standard that discusses specifications for metric dimensions of toroidal sealing rings ('O'-rings) and their housings. BS 4518 contains the material specification of a selection of standard elastomeric materials (rubber) for O-rings used in general industrial applications.
BS 4518 specifies the dimensions of elastomeric “O”-rings which are toroidal in shape, and which are used for sealing components against ingress or egress of fluids under dynamic and static conditions.
BS 4518 also specifies the shape and dimensions of five types of associated housing grooves for the rings when used at pressures not normally exceeding 100 bar1).
Note: At pressures exceeding 100 bar, or when the diametral clearances of the grooves are in excess of those specified in BS 4518, it is recommended that these “O”-rings should be used in conjunction with anti-extrusion backup rings. Spiral anti-extrusion backup rings and their housings, the dimensions of which are specified in BS 5106, are suitable for pressures up to approximately 200 bar.
Two charts are provided in Appendix A to aid the selection of “O”-rings.
BS 4518 on the specification for metric dimensions of toroidal sealing rings ('O'-ring dimensions) and their housings is useful for:
As a sealing device, the objective of O-Rings is to stop a passage via which fluid or air can escape. When the O-Ring is squeezed between two surfaces, it takes up space and inhibits the path that the fluid or air wants to take.
BS 4518 provides guidance on dimensions, surface imperfections, material, reference number, housing grooves, surface texture are intended to aid the selection of appropriate seals for given applications.
Using BS 4518 guidelines, you can identify the components based on operational requirements. BS 4518 guidelines help you to determine the compatibility of O-rings with the equipment based on parameters of the application. By applying BS 4518 you can select these elastomeric materials that result in manufacturing better quality O-rings.