Back-up O-Rings
Explore Back-Up O-Rings Designed for Higher-Pressure Applications
- Back-Up Rings used with O-Rings at pressures > 1500 psi or big extrusion gaps
- Back-Up Rings are designed to limit O-Ring clearance gap extrusion.
- Available in elastomeric compounds and PTFE Back-Up Rings.
- PTFE Back-up rings can be solid, split, spiral, or custom for ease of install.
- PTFE Back-up Ring size standards AN6244, AN6246, MS27595, MS28774, MS28782 and MS28783.
- Elastomer Back-up Rings are typically contoured to conform to an O-Ring.
- Elastomer Back-up Rings fit standard USA and custom O-Ring sizes.
- Back-up Rings require wider glands to accommodate.
 |  | | Extruding O-Ring Without a Back-up Ring | O-Ring sealing properly with Back-up Ring |
Back-up Rings are flat, split, spiral or contoured washer type fittings used to protect an O-Ring seal from extrusion at higher pressures and temperatures. A Back-up Ring works by blocking or reducing the extrusion gap, thus preventing the o-ring from extruding. The use of a back-up ring increases the pressure and temperature capability of o-rings. Back-up Rings can be solid, split, spiral or contoured. The split and spiral back-up rings are easier to install, especially in small diameters. The chart to the right depicts the higher pressure capabilities of using Back-up Rings for a given clearance gap dimension. Back-up Rings can be used on both sides of the O-Ring if pressure is bidirectional. Gland widths should be widened to accommodate one or two Back-up Rings. Please contact us for selection and design assistance. |  |
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 | | | Marco CPD# | SPECIFICATIONS AND VARIATIONS | RELATIVE COST |
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| T1017 | Commercial Grade. Commercial Grade PTFE for similar sizes to MS28774 to fit Glands per Mil-G-5514 and Mil-P-5514 and custom sizes. |  | | T1004 | Per MS28774. PTFE material per MIL-R-8791. To fit Glands per Mil-G-5514 and Mil-P-5514. | | | T1007 | Per M8791/1. PTFE material per MIL-R-8791. To fit Glands per Mil-P-5514C, D & E and Mil-G-5514F. | | | T1011 | Per MS28773 for Tube Fittings. Dash size numbers correspond to the MS28778 packing and AN6289 nut. | | | | | Per BACR12BM. Heavy Duty to fit MIL-P-5514C thru F glands. PTFE per BMS 8-121, Type 1, Class1, Grade B. | | | T1010 | Per MS9058 for Boss Connection. Dash number sizes correspond to AN-6290 O-ring sizes. PTFE per AMS 3656/ AMS 3660. | |
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 | | | Marco CPD# | SPECIFICATIONS AND VARIATIONS | RELATIVE COST |
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| T1032 | Commercial Grade. Commercial Grade PTFE for similar sizes available to the MS28782, MS28783, MS35803 and AN6244 sizes and custom sizes. | | | T1008 | Per MS27595. PTFE material per MIL-R-8791. To fit Glands per Mil-G-5514F. | | | | | Heavy Duty Per BACR12BP. To fit MIL-P-5514C thru F glands.
PTFE per BMS 8-121, Type 1, Class1, Grade B. | |
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 | | | Marco CPD# | SPECIFICATIONS AND VARIATIONS | RELATIVE COST |
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| T1009 | Commercial Grade. Commercial Grade PTFE for similar sizes available to the MS28782, MS28783, MS35803 and AN6244 sizes and custom sizes. | | | T1033 | | T1005 | Per MS28782. Dash sizes correspond to the AN6227 packing. PTFE per MIL-R-8791. | | | T1006 | Per MS28783. Dash sizes correspond to the AN6230 packing. PTFE per MIL-R-8791. | |
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 | | | Marco CPD# | SPECIFICATIONS AND VARIATIONS | RELATIVE COST |
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| U1000 (NBR90) | Most Commonly Available in 90 Durometer Nitrile and FKM in AS568A O-Ring sizes. Other materials and sizes can be made to order.
Rubber Back-Up rings perform the same function as PTFE back-ups; to reduce the extrusion gap and thus increasing o-ring’s pressure capabilities. They provide sufficient elasticity to permit stretching over the major diameter of a piston and then snapping back into the gland groove cut into the piston. 90 durometer has sufficient hardness to resist extrusion of the softer elastomeric o-ring performing the actual sealing function against the high pressure liquid or gas. | | | U1002 (FKM90) |
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