Value Collection ZMSCHB90342 O-ring Backup Ring Nbr

Product Description

The VALUE COLLECTION ZMSCHB90342 is a rectangular-cross-section backup O-ring made from Nitrile Butadiene Rubber (NBR), rated at 90 durometer for extra-hard hardness. It measures 3.648 inches inner diameter, 4.014 inches outer diameter, and 0.0625 inches thick, corresponding to Dash Number 8-342. Backup rings of this profile are installed behind primary O-rings in hydraulic and pneumatic assemblies to prevent extrusion under pressure, extending seal service life in demanding applications. Licensed plumbers, HVAC technicians, and industrial mechanics install this type of seal during pump, valve, and cylinder service work.

This backup ring suits residential and commercial maintenance applications involving hydraulic cylinders, pneumatic actuators, pump housings, and fluid-control valves where a Dash 8-342 rectangular NBR seal is specified. The -40 to 250 degrees F operating range makes it suitable for moderate-temperature fluid systems, including water, oils, and common refrigerants compatible with NBR compound. It is sold in a package quantity of 10 and carries a minimum order quantity of 1 package.

Key Features

• Rectangular cross section prevents primary O-ring extrusion under system pressure
• 90 durometer extra-hard NBR compound resists deformation in high-load sealing grooves
• Dash 8-342 sizing for direct drop-in replacement to standard SAE O-ring groove specs
• Operating range of -40 to 250 degrees F covers a broad range of fluid system service conditions
• Nitrile Butadiene Rubber construction offers resistance to petroleum-based fluids and water
• Packaged in quantities of 10 to support multi-unit repair kits or stocking needs

Compatibility

Designed as an OEM-style replacement for hydraulic, pneumatic, and fluid-control assemblies specifying a Dash 8-342 rectangular backup ring in NBR compound with 90 durometer hardness.

Installation Notes

Installation should be performed by a qualified mechanic, plumber, or HVAC technician after fully depressurizing and isolating the system being serviced. Clean the O-ring groove thoroughly and inspect for wear or damage before installing the backup ring. Avoid rolling or twisting the ring during installation, as rectangular-cross-section backup rings must seat flat in the groove to function correctly. Refer to the equipment manufacturer's service manual for groove dimensions and assembly torque specifications.