Back Up Washers

A continuous one piece ring - will not pinch o-ring


Back Up Washers are used in conjunction with ‘O’ Rings for both static and dynamic sealing applications. The prevent extrusion of the ‘O’ Ring when it is subjected to high pressures, or when the extrusion gaps are excessive.

Whenever possible two Back Up Washers should be used, one on each side of the ‘O’ Ring.

All Series 19 Back Up Washers are continuous one piece rings, so they will not pinch ‘O’ Rings. The Polyurethane material used, allows the rings to be stretched over pistons for easy installation.

Types Available

  • For general use (i.e. either for rod or piston): Request Series 19
  • For rod applications (with interference fit on O.D.): Request Series 19/RO
  • For piston application (with interference fit on I.D.): Request Series 19/PI


  • TYPE: Unithane 395A, Liquid Cast Polyurethane
  • HARDNESS: Durometer 95A
  • CHEMICAL COMPATABILITY: See ‘Material Specifications’,
    Technical Bulletin US – 96