Columbia provides a full line of back-up rings and other anti-extrusion devises. Back-up rings are used with a primary seal such as an o-ring in both dynamic and static applications to prevent extrusion of the oring when it is subject to high pressures, there are excessive extrusion gaps present in the application, or the o-ring is exposed to elevated temperatures. Elevated temperatures (160°F and higher) impose a severe burden on the physical and mechanical properties of rubber O-Rings which further increases their tendency to extrude. Two back-up rings should be used with one on each side of the primary seal.
The combination of high pressures and high temperatures is a common occurrence in present day fluid systems. Moreover, the trend is toward still higher pressures and longer resident times at elevated temperatures. This places more emphasis on the role of the back up ring in preventing O-Ring extrusion.
Our standard 800 Series Rubber Contoured Back-up Rings are manufactured from a 90 durometer material. For material information, please review our engineering center's material reference manual
Contoured Backup Rings: 800 Series Standard Nitrile
|Illustration of high pressure application with o-ring seal extruding
There are three basic types on Teflon back-up rings: T1 single turn (scarf cut), T2 multi-turn (spiral cut), and T3 solid (uncut).
T1 single turn
|Illustration of high pressure application with back-up ring to prevent primary seal extrusion
Columbia also has the ability to provide back-up rings for applications where standard sizes or material are not applicable. Contact our engineering group today to discuss your specific application.
Filled Teflon back-up rings: For applications where sealing systems are subjected to severe duty cycles, or where pressures exceed 3,000 psi and temperatures are above 275°F, filled Teflon back-up rings are very useful. TF-C-086 is a material well suited for high pressure, high temperature applications against hardened and/or chrome plated running surfaces. Tetralon 720, an unusual nonabrasive compound, is suitable for use against both hard anodized surfaces and most non-heat hardenable metals. Both of these materials provide wear resistance superior to unfilled Teflon when used in conjunction with MIL-P-83461 O-Ring compound in MIL-H-83282 and MIL-5606 hydraulic fluids. In addition to the more common fills such as glass fibers, Columbia has accumulated considerable experience with back up rings of Nylon, Kel F, FEP, UHMW and others. We have the very standards shown in this catalog using these materials as well as more specialized compounds of Teflon. Care should be taken in selecting a compound that is compatible with the gland or rod materials of construction to prevent abrasion or wear problems. Please contact Columbia direct for assistance in the selection of materials that will best fit your needs.
In addition to the military standards, Columbia supplies three series of extended dash-size standards which provide back up rings for all O-Rings in the Aerospace Standard AS-568A Uniform Numbering System. These configurations, T3-74, T1-74, and T3-171 have proven very useful to fluid systems designers because of the added flexibility in size selection.