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Military Standard MS28774-142 Teflon (PTFE) Retainer, Packing
PART #: SGP136720MFR PART #: MS28774-142Our Price: $1.61 (Each)QTY: Add to Cart -
Military Standard MS28774-211 Teflon (PTFE) Retainer, Packing
PART #: SGP136728MFR PART #: MS28774-211Our Price: $0.63 (Each)QTY: Add to Cart -
Military Standard MS28774-212 Teflon (PTFE) Retainer, Packing
PART #: SGP136729MFR PART #: MS28774-212Our Price: $0.70 (Each)QTY: Add to Cart -
Military Standard MS28774-221 Teflon (PTFE) Retainer, Packing
PART #: SGP136739MFR PART #: MS28774-221Our Price: $1.11 (Each)QTY: Add to Cart -
Military Standard MS28774-232 Teflon (PTFE) Retainer, Packing
PART #: SGP136750MFR PART #: MS28774-232Our Price: $2.31 (Each)QTY: Add to Cart -
Military Standard MS28774-239 Teflon (PTFE) Retainer, Packing
PART #: SGP136757MFR PART #: MS28774-239Our Price: $5.10 (Each)QTY: Add to Cart -
Military Standard MS28774-243 Teflon (PTFE) Retainer, Packing
PART #: SGP136762MFR PART #: MS28774-243Our Price: $7.76 (Each)QTY: Add to Cart -
Military Standard MS28774-331 Teflon (PTFE) Retainer, Packing
PART #: SGP136771MFR PART #: MS28774-331Our Price: $1.82 (Each)QTY: Add to Cart -
Military Standard MS28774-335 Teflon (PTFE) Retainer, Packing
PART #: SGP136775MFR PART #: MS28774-335Our Price: $2.53 (Each)QTY: Add to Cart -
National Aerospace Standard NAS1523-08R Packing with Retainer
PART #: SGP181527MFR PART #: NAS1523-08ROur Price: $8.17 (Each)QTY: Add to Cart -
National Aerospace Standard NAS1523-08Y Packing with Retainer
PART #: SGP140639MFR PART #: NAS1523-08YOur Price: $6.28 (Each)QTY: Add to Cart -
National Aerospace Standard NAS1523-10R Packing with Retainer
PART #: SGP140640MFR PART #: NAS1523-10ROur Price: $10.24 (Each)QTY: Add to Cart
Ask any Skygeek and they will tell you a back-up ring functions on the principle of "everything needs support." As its name implies, it is a sturdy ring that "backs-up" (usually a rubber) seal. It is designed specifically to hold or maintain this seal in its proper position.
In many assemblies, joints require a seal. This is done so as to prevent the leakage of fluid or gas. O-rings are often used as a seal. However, due to extreme pressures inherent in aviation, these seals may extrude or lose their place and thus compromise their intended use. Back-up rings prevent extrusion and thus are used in conjunction with O-rings.
Back-up rings, like their O-ring counterparts, are usually made of elastic polymers, the most common being nitrile butadiene rubber (NBR) and polytetrafluoroethylene (PTFE or Teflon). Like other materials, elastomers are often given a hardness rating (durometer). This identifies a material's resistive strength, especially when dealing with pressures and other external forces. For instance, when viewing a back-up ring, you might find a 70 or 75A in its name; these numbers refer to its durometer.
Besides material, back-up rings can be classified by type, three variations include: spiral, endless, and endless split. A spiral back-up ring is the most frequently used because of its ability to efficiently self-adjust to diametrical tolerances. Endless back-up rings are applied whenever problems occur with the rotation of screwed endcaps that may cause a spiral type to unwind. The endless split back-up ring is identical to the endless back-up ring, the only difference is it is split at a 30-degree angle; this facilitates assembly for some applications.
Finally, back-up rings conform to several military specifications and Skygeek carries them including: MS27595, M8791, and MS9058. Our inventory is growing so check in from time to time. Otherwise, click on the specific series of back-up rings and make sure your seals are supported.