Value Collection ZMSCH70390 O-ring Dash 390 Nitrile 70A

Product Description

The VALUE COLLECTION ZMSCH70390 is a Dash 390 Buna-N (Nitrile Butadiene Rubber) O-ring with a 21-inch inside diameter, 21.375-inch outside diameter, and 0.1875-inch (3/16 inches) cross-section thickness. The round cross-section profile seats consistently in standard O-ring grooves. With a 70 durometer hardness rating and a service temperature range of -40 degrees F to 250 degrees F, this O-ring is well-suited for static and dynamic sealing applications involving petroleum-based fluids. It is one of the most widely used elastomer compounds in fluid sealing. Licensed plumbers, HVAC technicians, and mechanical contractors regularly specify Buna-N O-rings for fluid system maintenance and repair.

This O-ring is used in residential and commercial applications wherever petroleum-based fluid sealing is required. Typical install scenarios include pump housings, valve bodies, pipe flanges, hydraulic fittings, and fluid handling assemblies. Its large diameter makes it common in industrial piping systems, large-bore valves, and commercial mechanical equipment. The Buna-N compound offers excellent resistance to petroleum products, good compression set characteristics, and solid tear and abrasion resistance. This O-ring should not be stored in direct sunlight or near motors and other electrical equipment that may generate ozone, as ozone exposure degrades NBR compounds.

Key Features

• Buna-N (NBR) elastomer: the most widely used O-ring material for petroleum fluid compatibility
• 21-inch inside diameter and 21.375-inch outside diameter to fit large-bore Dash 390 groove dimensions
• 70 durometer hardness rating for firm seating and reliable compression set performance
• Service temperature range of -40 degrees F to 250 degrees F
• Round cross-section for consistent groove seating in standard O-ring applications
• Meets SAE and MIL-Spec standards

Compatibility

Designed as an OEM-style replacement or service O-ring for large-bore fluid system components requiring a standard Dash 390 groove specification with Buna-N material compatibility for use with petroleum-based products.

Installation Notes

Installation should be performed by a licensed plumber or qualified mechanical technician following applicable codes such as the IPC or relevant ASME standards. Depressurize and drain the system completely before removing the existing O-ring. Inspect the groove for scoring or debris before seating the replacement ring. Lubricate with a compatible petroleum-based or silicone grease as specified for the system fluid to avoid tearing during assembly.