1 Scope
This British Standard specifies requirements for the design and dimensions of a range
of spiral anti-extrusion back-up rings that prevent “O”-rings, manufactured in accordance
with BS 4518, from extruding under pressure or where extrusion clearances are in excess of those
specified in BS 4518.
NOTE 1 These spiral back-up rings are particularly suitable for use in hydraulic diametral sealing applications where the pressures exceed 100 bar and are generally less than 200 bar, where 1 bar = 105 N/m2 = 105 Pa. Annex B provides guidance on obsolete series of sprial back-up rings.
This British Standard also specifies the shape and dimensions of housing grooves to
accommodate one or two spiral back-up rings and their associated “O”-ring.
NOTE 2 The range of spiral back-up rings specified in this British Standard is intended for use with “O”-rings selected from BS 4518.
NOTE 3 Annex A provides guidance for the assembly of spiral back-up rings.