The unique G-T® Ring provides a compact double acting seal for use in a new design for heavy duty applications where a more bulky type of seal had previously been required, as well as for retrofit in standard grooves designed for O-rings with two, one, or no backups. This proven seal combines a tough, resilient, T-shaped sealing ring with precisely-dimensioned, pressure-actuated non-extrusion rings – for use with pressures ranging from zero to 10,000 psi (690 bar) and higher.
Performance, reliability, and economy as a piston seal are unequaled – with no piston drift with minimum piston length. This seal eliminates two major sealing problems: 1) the G-T Ring sealing element is protected from extrusion so that it seals satisfactorily when clearances must be abnormally large or where pressures are high, 2) the unique G-T Ring configuration presents seal roll and spiral failure. (See Fig. 1)
The G-T Ring is a piston, rod or static seal for use in cylinders, intensifiers, accumulators, spool valves, and other demanding fluid power applications. It is currently specified for critical applications on all major jet aircraft (both military and commercial), sealing accumulators, reservoirs, actuators, valves, and the most rugged landing gear shock strut applications.
For more than 25 years the G-T Ring has been used by the Ordnance Department as the primary seal in recoil systems and by designers to solve their most severe sealing problems encountered in a wide variety of industrial and mobile equipment – including rough terrain lift trucks, front end loaders, tractors, back hoes, excavators, graders, cranes, jacks, oil field valves and well heads, and machine tools.
The G-T design resists extrusion by preventing the elastomeric sealing element from wedging into the diametral clearances, or pinching off under motion or pressure. Under pressure, the resilient T-shaped elastometric-sealing element deforms transmitting hydraulic pressure “down stream”. This causes radial
swelling or expansion of the flange under the non-extrusion backup ring on the low-pressure side of the assembly (See Fig. 2). The skive cut in the nonextrusion ring permits instantaneous radial movement into positive contact with the cylinder bore or rod being sealed, closing the clearance gap before any extension of the sealing element can occur.
Since the non-extrusion rings do not rely on axial compression to radially expand, but are moved radially by hydro-mechanical action, they need not be made of easily deformed material. Rather they can be made of durable, low friction material with high shear strength and high resistance to cold flow, which results in superior resistance to extrusion. These pressure activated, non-extrusion rings successfully bridge the large clearance incident to the use of wear rings – and protect the seal both from extrusion and contamination. As radial loading of the non-extrusion rings varies directly with fluid pressure, seal friction is kept to a minimum during the low pressure portion of the pressure cycle.
Resistance to Roll
The seal is installed in the groove on a flat, stable, static base. The non-extrusion rings complete the rectangular shape of the seal assembly and “lock” the T-shaped sealing element in position so that it is restrained from rolling around its circumferential axis. The G-T ring cannot roll, twist or spiral (See Fig. 3) and therefore, it is not subject to this mode of failure.