Value Collection ZMSCHB90347 O-ring Backup Ring Nbr

Product Description

The VALUE COLLECTION ZMSCHB90347 is a rectangular-cross-section backup ring O-ring made from Nitrile Butadiene Rubber (NBR), rated at 90 durometer for extra-hard hardness. It measures 4.278 inches inside diameter, 4.644 inches outside diameter, and 0.0625 inches thick, conforming to Dash Number 8-347. The 90-durometer rating makes this a backup ring application seal, designed to prevent extrusion of primary O-rings under pressure. It is used by plumbers, pipefitters, hydraulic technicians, and industrial maintenance professionals working on fluid sealing assemblies where high hardness and dimensional stability are required. The NBR compound provides solid resistance across a wide temperature range.

This backup ring is suited for hydraulic and pneumatic systems, fluid handling assemblies, and industrial sealing applications operating between -40 degrees F and 250 degrees F. Its rectangular cross section seats firmly against primary seals to reduce blow-by and extrusion under load. Typical installations include cylinder rod and piston gland assemblies, manifold ports, and valve body sealing stacks where system pressures demand a hard backing element alongside a softer primary O-ring. Sold in a package quantity of 10, it is well suited for service shops maintaining backup inventory for repeat repair applications.

Key Features

• 90 durometer extra-hard NBR construction resists extrusion behind primary O-rings under pressure
• Rectangular cross section provides full face contact against gland surfaces
• 4.278 inches ID x 4.644 inches OD x 0.0625 inches thick, Dash 8-347 dimensional standard
• Operating temperature range of -40 degrees F to 250 degrees F
• NBR material offers good resistance to petroleum-based fluids, oils, and fuels
• Package quantity of 10 supports shop stock and repeat service calls

Compatibility

Designed as an OEM-style replacement backup ring for hydraulic, pneumatic, and fluid sealing assemblies requiring a Dash 8-347 rectangular NBR backup ring with 90 durometer hardness.

Installation Notes

Installation is typically performed by hydraulic technicians, pipefitters, or industrial maintenance mechanics. Depressurize and isolate the system completely before disassembling any gland or port. Inspect the gland groove for wear or damage before seating the backup ring, and ensure the primary O-ring is installed on the correct side of the backup ring relative to the pressure source. Avoid rolling or twisting the ring during installation to maintain its rectangular profile and sealing integrity.