Value Collection ZMSCHB90346 Backup Ring O-ring Nbr

Product Description

The VALUE COLLECTION ZMSCHB90346 is a rectangular cross-section backup ring O-ring made from Nitrile Butadiene Rubber (NBR), designed to prevent extrusion of primary seals in high-pressure static and dynamic sealing applications. It measures 4.153 inches inside diameter, 4.519 inches outside diameter, and 0.0625 inches thick. With a durometer hardness of 90 Shore A (Extra Hard), this ring provides rigid support behind softer primary O-rings. It carries a Dash 8-346 designation and is rated for temperatures from -40 degrees F to 250 degrees F. Licensed plumbers, pipefitters, and fluid-system technicians install this type of component in hydraulic, pneumatic, and industrial plumbing assemblies.

This backup ring is suited for static sealing applications in hydraulic cylinders, manifold assemblies, fluid fittings, and industrial piping systems where extrusion resistance is required. The NBR material offers reliable performance in contact with petroleum-based fluids, hydraulic oils, and water. The rectangular cross section seats reliably in standard grooves sized for Dash 8-346 geometry. It is sold in a package quantity of 10 units, making it practical for service stock or multi-point installations on a single job.

Key Features

• Rectangular cross section provides consistent extrusion resistance behind primary seals
• 90 Shore A Extra Hard durometer rating for high-pressure backup applications
• NBR material compatible with petroleum-based hydraulic fluids and water-based media
• Rated from -40 degrees F to 250 degrees F for broad service temperature range
• Dash 8-346 designation for precise groove and fitting identification
• Package of 10 units supports multi-point service and repair stock

Compatibility

Designed as an OEM-style backup ring for static and low-cycle dynamic sealing assemblies requiring a Dash 8-346 rectangular-section NBR ring at 4.153 inches ID.

Installation Notes

Installation is typically performed by licensed plumbers, pipefitters, or hydraulic system technicians. De-pressurize and lock out the system completely before disassembling any fitting or cylinder that contains the existing seal. Inspect the groove for burrs or damage before seating the backup ring, and ensure the primary O-ring is installed on the high-pressure side of the backup ring. Do not stretch the ring beyond its natural diameter during installation, as NBR at 90 durometer has limited elongation tolerance.