-
Military Specification M8791/1-110 Teflon (PTFE) Retainer, Packing
PART #: SGP130289MFR PART #: M8791-1-110Our Price: $0.74 (Each)QTY: Add to Cart -
Military Standard MS28774-015 Teflon (PTFE) Retainer, Packing
PART #: SGP136673MFR PART #: MS28774-015Our Price: $0.83 (Each)QTY: Add to Cart -
Military Standard MS28774-340 Teflon (PTFE) Retainer, Packing
PART #: SGP136780MFR PART #: MS28774-340Our Price: $4.82 (Each)QTY: Add to Cart -
Military Standard MS28774-228 Teflon (PTFE) Retainer, Packing
PART #: SGP136746MFR PART #: MS28774-228Our Price: $1.69 (Each)QTY: Add to Cart -
Military Standard MS28774-342 Teflon (PTFE) Retainer, Packing
PART #: SGP136782MFR PART #: MS28774-342Our Price: $9.12 (Each)QTY: Add to Cart -
Military Standard MS28777-8 Leather Retainer, Packing
PART #: SGP137147MFR PART #: MS28777-8Our Price: $1.16 (Each)QTY: Add to Cart -
Military Standard MS28774-215 Teflon (PTFE) Retainer, Packing
PART #: SGP136732MFR PART #: MS28774-215Our Price: $0.88 (Each)QTY: Add to Cart -
Military Standard MS28774-333 Teflon (PTFE) Retainer, Packing
PART #: SGP136773MFR PART #: MS28774-333Our Price: $2.61 (Each)QTY: Add to Cart -
Military Standard MS28774-337 Teflon (PTFE) Retainer, Packing
PART #: SGP136777MFR PART #: MS28774-337Our Price: $3.27 (Each)QTY: Add to Cart -
Military Standard MS28774-010 Teflon (PTFE) Retainer, Packing
PART #: SGP136668MFR PART #: MS28774-010Our Price: $0.78 (Each)QTY: Add to Cart -
National Aerospace Standard NAS1523AA08B Packing with Retainer
PART #: SGP140668MFR PART #: NAS1523AA08BOur Price: $168.35 (Each)QTY: Add to Cart -
National Aerospace Standard NAS1523C4B Packing with Retainer
PART #: SGP140732MFR PART #: NAS1523C4BOur Price: $6.00 (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.