NBR 90 Shore A O-Rings for High Pressure Hydraulic Glands - AS568 Standard
NBR 90 Durometer O-Rings for High Pressure Hydraulic Glands
NBR 90 Shore A O-rings are specified for hydraulic glands where extrusion clearance and pressure cycling are key selection factors. Nominal hardness is one part of the design: provide maximum pressure, clearance at operating load, oil specification and temperature. Review the groove and any backup rings before selecting a seal for a cylinder, valve or manifold.
| Material | NBR (Nitrile / Buna-N) |
|---|---|
| Hardness | 90 Shore A (90 durometer, hard grade) |
| Temperature | Confirm service temperature limits for the selected NBR compound |
| Color | Black |
| Standards | Specify AS568 dash size or metric ID and cross-section, with agreed tolerance |
| Sealed Media | Specify hydraulic-fluid type and additives for compound compatibility review |
| Not Recommended | Ozone, ketones, esters, strong acids, aromatic hydrocarbons (long term), H2S |
Features
- 90 Shore A nominal hardness, selected together with pressure and extrusion clearance
- Specify compression-set and pressure-cycle requirements for the compound
- NBR material family for compatible oil service; confirm fluid and wear requirements
- AS568 or metric dimensions specified by dash number or drawing
Applications
High-pressure hydraulic cylinders, presses, power units, directional valves, manifolds, injection molding machines, and other equipment where the O-ring sees high pressure and a visible clearance gap.
FAQ
Q: What pressure can a 90 durometer NBR O-ring handle?
A: There is no universal pressure rating based only on 90 Shore A hardness. Provide maximum pressure, transient peaks, temperature, groove geometry and operating clearance. Backup-ring requirements and the selected compound must be reviewed for the complete gland.
Q: Why 90 durometer instead of 70 Shore A for high pressure?
A: Higher hardness can improve extrusion resistance, but it also changes installation and compression force. Compare the specific compounds against clearance, pressure, squeeze and motion. A harder ring does not correct an unsuitable gland or damaged mating surface.
Q: What gland clearance should I design to?
A: AS568 identifies O-ring sizes; it is not a universal pressure-clearance rule. Provide the equipment gland drawing, diametral clearance under load, surface finish and relevant design specification. Review squeeze, groove fill and backup rings against the service requirements.
Q: What sizes and standards are available?
A: Send an AS568 dash number or metric inner diameter and cross-section. State dimensional tolerances, nominal hardness, quantity and inspection requirements. Confirm availability and tooling for the specified size in the quotation.
Q: Is this O-ring rated for sour gas (H2S)?
A: This page does not establish sour-service qualification. Specify gas composition, pressure, temperature and decompression conditions, together with required tests. Neither NBR nor HNBR should be accepted for sour service from the polymer name alone.
Q: Can you supply other NBR grades?
A: Specify alternative hardness, low-temperature performance or regulatory requirements with the application details. Food-contact requirements need the applicable regulation and compound documentation; do not infer compliance from NBR material or color.
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