LineBacker® Isolating Gaskets/Kits


Flange Isolation Kits consisting of an isolating gasket and isolating sleeves and washers

LineBacker® sealing gaskets use a rectangular sealing element, referred to as a “quad” ring, in combination with a unique groove design to effectively seal and isolate flanges of all types. With the unique quad ring design, elastic memory is provided for elastomers not normally associated with this characteristic. Materials such as PTFE may therefore be used as sealing elements, dramatically increasing the ability to match gasket materials to service conditions. This greater variety of materials also provides excellent temperature and chemical range compatibility. LineBacker® sealing gaskets are self-energizing resulting in a positive seal without excessive bolt loads – as are often required with flat gaskets.


  • Guards against blowouts¹
  • Usable with virtually any type of flange
  • Matches gasket materials to service conditions
  • Lowest possible clamp and compressive load



  • All standard ANSI and API flange sizes from 1/2″ and above
  • Custom odd sizes and shapes
  • AWWA flange sizes from 1/2″ and above

The LineBacker® gasket is constructed from G10 glass-reinforced epoxy (GRE). The LineBacker® contains a rectangular sealing element referred to as a “quad-ring.” The quad-ring is used in combination with a unique, engineered groove design and together they provide an effective sealing element that also requires less bolt load than a typical flat gasket. The sleeves and washers offered with the LineBacker® gasket are completely temperature dependent. Most commonly used are Mylar and G10 sleeves accompanied by G10 and zinc plated steel washers. Sleeve will be designed to mate with separate isolating washers and will be of a length such that the sleeve extends into one and one-half washer thicknesses on each side of the flange.


All ANSI rated flanges to 600#/2,225 psi respectively. Maximum hydrotest pressure is 2480 psi and 302Fp>


The LineBacker™ is an excellent choice for isolating distribution lines and transport lines for gas, oil and water. The screened version is the best available product for filtering welding slag, rocks, nuts, bolts and other particulates from traveling downstream and damaging valves, pumps, compressors, etc. Because the LineBacker™ has very good resistance to creep relaxation², it performs well in heat exchangers, applications with high vibration or excessive thermal cycling.


Gasket Types

Isolating gaskets may be specified as either “E” or “F” type while single, double or one-piece sleeve and washer sets are offered as options for varying degrees of electrical isolation between the flanges. A wide variety of material options exist for both isolating gaskets and sleeve and washer materials.

All kits are correctly sized for the application and conveniently packaged to minimize loss of component parts during installation.

Type E Gasket (Full Face) The gasket retainer extends out to the O.D. of the flange. Holes are cut at the bolt circle to accommodate threaded studs and sleeves. 

Type F Gasket(Ring Type) The gasket retainer extends out to the I.D. of the bolt circle. The threaded studs and sleeves center the gasket in the flange.

Single Washer Set flange isolation kits include the following items for each threaded stud:

  • One – 1/8″ thick steel washer
  • One – Isolating Washer
  • One – Isolating Sleeve

Application Considerations

In buried applications, single washer configurations may be used to allow the Cathodic Protection (CP) current to reach the nuts and bolts. If desired, nuts on the opposite side of the cathodically protected flange may be included as part of the protected system.

Double Washer Set

Double washer set flange isolation kits include the following components for each bolt:

  • Two – 1/8″ thick steel washers
  • Two – Isolating washers
  • One – Full length isolating sleeve

Application Considerations

Double washer configurations may be used for added protection against the possibility of “shorting out” the nuts and bolts. In addition, double washer sets electrically isolate the nuts and bolts from both flanges.

Acetal One-Piece Sleeve and Washer Sets

One-piece sleeves eliminate the possibility of error by installers. One-piece sleeve and washer set flange isolation kits include the following items for each bolt:

  • Two – 1/8″ thick steel washers
  • One-One-piece isolating sleeve

Application Considerations

Easier to install, one-piece sleeves also allow the inspector a visual indication of sleeve usage. Due to the relatively low compressive strength of this material, its use is not recommended for high pressure or large diameter flanges that require high torque loads.