T-seals were originally developed to retain the advantages of O-rings in dynamic fluid power applications while addressing two of their most serious reliability problems: (1) squeeze through the gap between static and dynamic surfaces, and (2) Instability in the groove, which leads to failure of the helix or twist. T-seals eliminate both of these problems while retaining the space-saving properties of compact O-ring grooves. Most importantly, the T-seal meets or exceeds the O-ring's Excellent sealing ability at all pressures and temperatures.

The extrusion clearance is rarely constant throughout the stroke. The gap may vary due to uneven wear along a rod or bore, it may vary as system pressure rises (breathing) and distance from end restraints changes (thereby changing the stretch of cylinder walls). Ovality of cylinder tubes or rod glands due to side-load is not necessarily constant throughout the stroke, and out-of-round tubes may assume a near-perfect circular shape where restrained by the end caps.

These numerous possible sources of changing extrusion gaps make T-seals' speed of response extremely valuable. Despite rapid strokes, lateral shock loads, pressure surges, and uneven wear or stretching, T-seals maintain zero extrusion gaps. In the free state, back-up rings appear quite loose on their seal element. This slack is taken up during installation, however, since the interference fit of the seal in standard O-ring grooves either stretches (piston seals) or compresses (rod seals) the element to seat the backups.  T-seals are easy to assemble and may be inserted into their grooves manually without special assembly tools.

T-shaped seal support ring can quickly track the change of dynamic surface and become a very effective wiper to keep contaminants away from the seal line.

Standard to T-seals are skive-cut back-up rings. Skive-cut rings are simple to install and allow harder and more extrusion-resistant materials to be used without sacrificing their ability to respond quickly to gap changes.

JST produces customizable T-seals from a variety of materials to meet almost any gland size.