Back to overview Back Ring


The STR back-up ring is a virgin PTFE ring of 55 shore D hardness as to guarantee a high level of resistance to extrusion and abrasion. The STR back-up ring is of symmetrical profile. This allows it to be used in both internal and external sealing systems.


STR back-up rings are used in conjunction with O-Rings to avoid gap extrusion. Under high pressures and with large sealing gaps, there is the risk that the material of the O-Ring is compressed into the sealing gap at the side not subject to pressure. If this process is repeated and if the pressure rises further, then irreversible damage may be caused to the O-Ring and it may eventually be completely destroyed. STR back-up rings are used to reduce the risk of gap extrusion. These reduce the sealing gap at the side of the O-Rings not subject to pressure. STR back-up rings do not fulfil any sealing function per se. However, by reducing the sealing gap at the side not subject to pressure, they ensure that the O-Ring can fulfil its sealing function in the long term, without suffering any damage. Back-up rings are also used for applications involving pulsed and varying pressures. STR back-up rings are often used in hydraulic systems, especially in hydraulic valves and hydraulic pumps, and also for sealing cylinder bottoms and heads (in conjunction with O-Rings). However, STR back-up rings are also used in many other fields of industry as a whole, e.g. for sealing ball valves.

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design material d D H brand legacy item no. item no. SP | IP    
STR 55 PTFE - - - Dichtomatik BU-85X2.5X1.25PTFE 75186899 Details