ST08-13 customized Machined Back-up Rings
A back-up ring sits behind an O-ring or seal lip and blocks the extrusion gap. Without one, the elastomer is forced into the clearance at high pressure and nibbles away until the joint leaks. SES holds the range as an authorised SKF distributor, covering purpose Closes the extrusion gap behind an elastomer seal; materials Virgin and filled PTFE, POM, polyamide, fabric-reinforced resin; cut styles Solid, spiral wound, scarf cut, bias cut; profile Flat or concave to wrap the O-ring. Executions include solid PTFE back-up rings, spiral back-up rings, scarf-cut back-up rings, concave profile rings, among others. It is specified most often into high-pressure test rigs and pressure vessel closures and hydraulic accumulator and manifold block joints. Every part is genuine SKF through official channels, with designation, specification and options confirmed against your duty before it ships — supplied from Kolkata and our branch network, with breakdown cover that does not sit in an inbox.
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From integrated steel plants to power utilities and EPC majors — the works that cannot afford a counterfeit part specify through SES.
Duty
Anti-extrusion support
Materials
PTFE, POM, PA, fabric-reinforced
Forms
Solid, spiral, scarf cut, concave
Position
Low-pressure side of the seal
Where it runs.
You will find ST08-13 customized Machined Back-up Rings in the parts of a plant where this particular duty actually occurs. In practice that means high-pressure test rigs and pressure vessel closures, hydraulic accumulator and manifold block joints, descaling pump and high-pressure water systems in a rolling mill, and equally screwdown and hydraulic gap control cylinders, valve spindle and actuator glands on a process line, mobile plant pilot and pressure control valve blocks. What links them is the duty rather than the machine name — duty: Anti-extrusion support. If your installation is not on that list it matters less than you would think: the operating condition decides the specification. Send us the load, the speed, the running temperature and the environment it runs in, and we will match it to the right execution in the SKF range and confirm what is in stock.
Specify it against the duty.
Specification here follows the operating condition, not the catalogue. Pressure acts from one direction only — One ring on the downstream side. Fit it on the pressure side by mistake and it does nothing at all — the O-ring still extrudes. Pressure alternates, as in a double-acting piston groove — A ring either side of the O-ring. A single ring in an alternating groove leaves one direction unprotected and the seal shreds on that stroke. The groove is closed and cannot be split for assembly — A spiral or scarf-cut ring so it can be wound into place. Forcing a solid ring over a piston land stretches it permanently. Where two of those apply at once, specify for the harsher of the two — under-specifying is what puts the part back on the bench a month later. Send us the duty and we will confirm the execution.
Ordering this from SES.
Concave rings have a right way round. The hollow face must sit against the O-ring so the elastomer is cradled; fitted flat-face-in, it pinches the O-ring and cuts it instead. Send the designation off the failed part and we will confirm the SKF equivalent and stock position.