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Military Standard MS28774-229 Teflon (PTFE) Retainer, Packing
PART #: SGP136747MFR PART #: MS28774-229Our Price: $1.82 (Each)QTY: Add to Cart -
Military Standard MS28774-446 Teflon (PTFE) Retainer, Packing
PART #: SGP136807MFR PART #: MS28774-446Our Price: $11.72 (Each)QTY: Add to Cart -
National Aerospace Standard NAS1523C3E Packing with Retainer
PART #: SGP140726MFR PART #: NAS1523C3EOur Price: $2.43 (Each)QTY: Add to Cart -
National Aerospace Standard NAS1523C06R Packing with Retainer
PART #: SGP140714MFR PART #: NAS1523C06ROur Price: $9.96 (Each)QTY: Add to Cart -
Military Standard MS28774-013 Teflon (PTFE) Retainer, Packing
PART #: SGP136671MFR PART #: MS28774-013Our Price: $0.87 (Each)QTY: Add to Cart -
National Aerospace Standard NAS1523AA4R Packing with Retainer
PART #: SGP140696MFR PART #: NAS1523AA4ROur Price: $2.97 (Each)QTY: Add to Cart -
Military Standard MS28774-005 Teflon (PTFE) Retainer, Packing
PART #: SGP136663MFR PART #: MS28774-005Our Price: $1.61 (Each)QTY: Add to Cart -
Military Standard MS28774-217 Teflon (PTFE) Retainer, Packing
PART #: SGP136734MFR PART #: MS28774-217Our Price: $1.02 (Each)QTY: Add to Cart -
Military Standard MS28774-325 Teflon (PTFE) Retainer, Packing
PART #: SGP136765MFR PART #: MS28774-325Our Price: $1.02 (Each)QTY: Add to Cart -
Military Standard MS28774-210 Teflon (PTFE) Retainer, Packing
PART #: SGP136727MFR PART #: MS28774-210Our Price: $0.60 (Each)QTY: Add to Cart -
Military Standard MS28774-116 Teflon (PTFE) Retainer, Packing
PART #: SGP136693MFR PART #: MS28774-116Our Price: $0.70 (Each)QTY: Add to Cart -
Military Standard MS28774-238 Teflon (PTFE) Retainer, Packing
PART #: SGP136756MFR PART #: MS28774-238Our Price: $2.40 (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.