O-Ring Back-Up Rings 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.

 

Single Turn or Split Back Up Rings

SPECIFICATIONS AND VARIATIONS RELATIVE COST
Commercial Grade. Commercial Grade PTFE for similar sizes to MS28774 to fit Glands per Mil-G-5514 and Mil-P-5514 and custom sizes.
Per MS28774. PTFE material per MIL-R-8791. To fit Glands per Mil-G-5514 and Mil-P-5514. 
Per M8791/1.   PTFE material per MIL-R-8791. To fit Glands per Mil-P-5514C, D & E and Mil-G-5514F.
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. 
Per MS9058 for Boss Connection. Dash number sizes correspond to AN-6290 O-ring sizes. PTFE per AMS 3656/ AMS 3660.

Solid Back Up Rings

SPECIFICATIONS AND VARIATIONS RELATIVE COST
Commercial Grade. Commercial Grade PTFE for similar sizes available to the MS28782, MS28783, MS35803 and AN6244 sizes and custom sizes.
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.

Spiral Back Up Rings

SPECIFICATIONS AND VARIATIONS RELATIVE COST
Commercial Grade. Commercial Grade PTFE for similar sizes available to the MS28782, MS28783, MS35803 and AN6244 sizes and custom sizes.
Per MS28782. Dash sizes correspond to the AN6227 packing.
PTFE per MIL-R-8791.
Per MS28783.  Dash sizes correspond to the AN6230 packing.
PTFE per MIL-R-8791.

Contoured Rubber Back Up Rings

SPECIFICATIONS AND VARIATIONS RELATIVE COST
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.

Need a custom product design or custom material formulation to improve performance in a specific application to separate yourself from the competition? Let us prove how responsive our product and application engineers are and that our custom products and custom materials often cost less than our competitors’ standards.

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Marco Rubber & Plastics
PO Box 1150
Seabrook, NH 03874

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