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Military Standard MS28774-017 Teflon (PTFE) Retainer, Packing
PART #: SGP136675MFR PART #: MS28774-017Our Price: $0.78 (Each)QTY: Add to Cart -
Military Standard MS28774-020 Teflon (PTFE) Retainer, Packing
PART #: SGP136678MFR PART #: MS28774-020Our Price: $0.64 (Each)QTY: Add to Cart -
Military Standard MS28774-022 Teflon (PTFE) Retainer, Packing
PART #: SGP136680MFR PART #: MS28774-022Our Price: $0.87 (Each)QTY: Add to Cart -
Military Standard MS28774-111 Teflon (PTFE) Retainer, Packing
PART #: SGP136688MFR PART #: MS28774-111Our Price: $0.70 (Each)QTY: Add to Cart -
Military Standard MS28774-115 Teflon (PTFE) Retainer, Packing
PART #: SGP136692MFR PART #: MS28774-115Our Price: $0.58 (Each)QTY: Add to Cart -
Military Standard MS28774-117 Teflon (PTFE) Retainer, Packing
PART #: SGP136694MFR PART #: MS28774-117Our Price: $0.87 (Each)QTY: Add to Cart -
Military Standard MS28774-120 Teflon (PTFE) Retainer, Packing
PART #: SGP136697MFR PART #: MS28774-120Our Price: $1.00 (Each)QTY: Add to Cart -
Military Standard MS28774-125 Teflon (PTFE) Retainer, Packing
PART #: SGP136702MFR PART #: MS28774-125Our Price: $1.00 (Each)QTY: Add to Cart -
Military Standard MS28774-134 Teflon (PTFE) Retainer, Packing
PART #: SGP136712MFR PART #: MS28774-134Our Price: $0.88 (Each)QTY: Add to Cart -
Military Standard MS28774-135 Teflon (PTFE) Retainer, Packing
PART #: SGP136713MFR PART #: MS28774-135Our Price: $1.44 (Each)QTY: Add to Cart -
Military Standard MS28774-136 Teflon (PTFE) Retainer, Packing
PART #: SGP136714MFR PART #: MS28774-136Our Price: $1.44 (Each)QTY: Add to Cart -
Military Standard MS28774-139 Teflon (PTFE) Retainer, Packing
PART #: SGP136717MFR PART #: MS28774-139Our Price: $0.54 (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.