DOUBLE ACTING SEAL 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 zero, one, 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 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 prevents 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 commer- cial), 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 encoun- tered 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. EXTRUSION RESISTANCE 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 resi- lent T-shaped elastometric-sealing element performs transmit- ting 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 non-extrusion ring permits instanta- neous radial movement into positive contact with the cylinder bore or rod being sealed, closing the clearance gap before any extrusion 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 mini- mum during the low-pressure portion of the pressure cycle.

The seal is installed in the groove on a flat stable, static base. The non-extrusive 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. Since the G-Tnon-extrusion ring prevents extrusion and spiraling of the elastomeric sealing element, it is not necessary to sacrifice desirable wear resistance or low compression set characteristics by selecting a harder...

APPLICATION RECOMMENDATIONS Even though clearances should be reduced to a practical mini- mum in applications where pressures are 3000 psi or higher, the outstanding capability of the G-T® Ring to bridge the extrusion gap permits its use with clearances commonly encountered where bearing elements are included in the cylinder design or where there is side loading or piston and rod "lay down" (See Table 3). Suitable materials are available for use with all currently used hydraulic fluids in temperature ranges from minus 65°F to 500°F (-54°C to 260°C). The G-T Ring, correctly applied, provides long...

TABLE 1 ELASTOMERIC COMPOUND SELECTOR *TFE: Virgin or filled to GTspec.

TABLE 2 ANTI-EXTRUSION RING MATERIAL SELECTOR NWR: Wear Resistant Nylon to L-P-410A Arlon 1000: Polyetheretherketone to GTspec. Avalon 8: Graphite filled TFE to GT spec. Avalon 16: Glass and MoS2 filled TFE to GT spec. f Assembly includes 4 backups... 1 TFE backup each side adjacent to rubber sealing element; 1 NWR backup each side adjacent to groove wall 'Unless otherwise indicated, for temperatures above 275"F (135"C), contact GT for Backup Material selection.', PISTON TYPE "isKTi ! 'paan ! 1 pasn COMPACT INTER-BASE WIDE BASE WIDE BASE

PART NUMBERING SYSTEM The part numbering system requires the use of Tables 1-3, the material designator tables. For nonstandard designs contact GT Elastomer Back-up ring compound material designator, Back-up Size Greene, Tweed Statements and recommendations in this publication are based on our experience and knowledge of typical applications of this product and shall not constitute a guarantee of performance nor a modification or alteration of our standard warranty that shall be applicable to such products.