Nominal Size: 1/8" CS x 13/16" ID x 1-1/16" OD
Part number UC90211 is an AS568-211 UC90 cast polyester polyurethane O-Ring at 90 Shore A durometer, natural in color, TODI cured and molded from Freudenberg Disogrin 9251 with an actual size of 0.139" cross-section x 0.796" ID x 1.074" OD (3.53mm x 20.22mm x 27.28mm). It belongs to the AS568 -200 series, 0.139" (1/8") nominal cross-section family. It seals to 10,000 psi with standard gland clearance and no backup rings and runs roughly 5 to 10 times the wear life of nitrile in sliding service. Certified lot testing returned 6,217 psi tensile and 690 lbf/in Die C tear strength, three to four times what a 90 durometer nitrile ring delivers. It is sold and shipped by The O-Ring Store LLC in Clarkston, Washington.
Stop replacing nibbled, extruded and worn out nitrile rings on high pressure hydraulics. The UC90 cast urethane O-Ring is the toughest thing you can put in a standard AS568-211 gland, and it is built for the jobs that chew rubber up: heavy equipment cylinders, quick disconnect couplers, impact tools and abrasive slurry service. At 92 plus or minus 5 Shore A nominal it holds its shape under load where a thermoplastic urethane of the same hardness would creep, because it is a thermoset that crosslinks in the mold rather than being melted and reflowed.
This compound is a hydraulic and wear material, not an all purpose seal. It is at its best in petroleum oil, air, nitrogen and water below 120°F (49°C), and it is the wrong choice for hot water, steam, brake fluid, phosphate ester fluids and ketone solvents. The details below spell out exactly where it fits so you can make the call before you order.
Operating Temperature: -22°F to +212°F (-30°C to +100°C)
Continuous service, dry or in petroleum oil. Short intermittent excursions run to +250°F (+121°C). The static low temperature limit is -22°F (-30°C) and the dynamic low limit is roughly -10°F (-23°C), governed by a glass transition temperature of -33°F (-36°C). In water or water glycol, hold the UC90 to +120°F (+49°C) maximum.
Material and Performance Details
UC90 is Freudenberg Disogrin 9251, a cast polyester polyurethane carrying the ISO 1629 designation AU and the ASTM D2000 line callout 6BG950 A14 B14 B34 EO14 EO34 F17 Z1 Z2 Z3 Z4 Z5 Z6 Z7. The cure system is TODI, a stiff symmetrical molecule that packs the hard segments tighter than the more common MDI or TDI. That packing is what buys the high tensile, the extrusion resistance and the cold flexibility. Color is natural, opaque white to cream. At 90 durometer the ring is stiff enough to hold a 10,000 psi joint with the clearance kept to the standard gland tables, which is why it needs a 20 degree lead-in chamfer and broken edges at installation. What you give up is chemical breadth and long term compression set. Set runs 18 percent after 70 hours at 158°F (70°C) and 62 percent after 70 hours at 212°F (100°C), so long term static clamping at heat is not this compound's job.
- Excellent resistance to: petroleum oils and greases; mineral hydraulic fluid in ISO VG and AW grades; biodegradable hydraulic fluids of the natural and synthetic ester type (HETG and HEES); diesel and kerosene; jet fuel JP-4, JP-5 and JP-8; aliphatic gasoline; silicone oils and greases; air; nitrogen; gaseous and liquid CO2 at bottle pressure; water below 120°F (49°C); water glycol at ambient temperature; ozone, oxygen, sunlight and outdoor weathering; dilute mineral acids at ambient temperature; abrasion and extrusion
- Limited capability with: water from 120°F to 160°F (49°C to 71°C) on an intermittent basis only; water glycol above 120°F (49°C); aromatic gasoline and high aromatic fuels such as toluene and xylene; alcohols and alcohol blended fuels; dilute alkalis; long term storage in high humidity
- Not compatible with: supercritical CO2 at any pressure; continuous hot water above 120°F (49°C); steam at any temperature; ketones such as MEK and acetone; low molecular weight solvent esters such as ethyl acetate; chlorinated hydrocarbons; concentrated acids, alkalis and caustics; amines; phosphate ester fluids including Skydrol, Fyrquel and HFD types; glycol ether brake fluid in DOT 3 and DOT 4; hydrogen peroxide; hypochlorite bleach; DMF and DMSO
Sizes and Measurements
O-Ring sizes are always listed here as cross-section x ID x OD. The nominal size is the rounded fractional reference used to name and look up the ring. The actual size is the true manufactured dimension the ring is molded to, and it is the number to design your gland around. The OD is the ID plus two cross-sections.
- Nominal: 1/8" CS x 13/16" ID x 1-1/16" OD
- Actual: 0.139" CS x 0.796" ID x 1.074" OD
- Metric: 3.53mm CS x 20.22mm ID x 27.28mm OD
- Part Number: UC90211
- AS568 Dash Number: -211 (AS568-211)
- Size Family: AS568 -200 series, 0.139" (1/8") nominal cross-section family
- Approximate Weight: 0.855 g per ring, about 531 rings per pound, calculated from the actual size and a 1.17 g/cm3 density
- Compound Code: UC90
- TORS Compound Designation: PU-90
- Base Compound: Freudenberg Disogrin 9251
- Gland Type: standard AS568 O-Ring glands, no special gland geometry required
- Squeeze, Static: 15 to 25 percent
- Squeeze, Dynamic: 8 to 12 percent
- Stretch on Installation: 5 percent maximum on the ID
- Gland Fill: 75 to 85 percent
- Surface Finish, Dynamic: 8 to 16 microinch Ra
- Surface Finish, Static: 32 to 63 microinch Ra
- Installation: 20 degree lead-in chamfer and broken edges
- Cross-references: SAE AS568-211, Freudenberg Disogrin 9251, ISO 1629 AU, ASTM D2000 6BG950 A14 B14 B34 EO14 EO34 F17 Z1 Z2 Z3 Z4 Z5 Z6 Z7
Gland Guide for This Size
These numbers are worked out from the 0.139" (3.53mm) actual cross-section and the UC90 squeeze and stretch limits above. They are a starting point for your design. Your final gland depth also has to account for the ring and housing tolerances.
- Static Gland Depth for 15 to 25 percent squeeze: 0.104" to 0.118" (2.65mm to 3.00mm)
- Dynamic Gland Depth for 8 to 12 percent squeeze: 0.122" to 0.128" (3.11mm to 3.25mm)
- Largest Groove Diameter at 5 percent ID stretch: 0.836" (21.23mm)
Applications and Use Cases
Heavy equipment hydraulics is the core of it: bulldozers, excavators, loaders, forklifts, mobile lifts, mobile arm trucks and agricultural machinery, where cylinders see high pressure, dirt and side load all at once. Quick disconnect couplers are the other big one, where the ring is dragged across a metal edge on every connection and a nitrile ring shaves itself apart in a season. Anywhere a nitrile ring is getting replaced too often because it nibbled, extruded or wore out, and the fluid is oil, air or water below 120°F (49°C), this is the swap.
- Heavy equipment cylinders on bulldozers, excavators, loaders, forklifts, mobile lifts, mobile arm trucks and agricultural machinery
- Quick disconnect couplers that drag the ring across a metal edge on every connection
- Injection molding machines, presses, general cylinders, valves and flange faces
- Mining, aggregate and slurry equipment in abrasive service
- Air tools, nail guns, riveters and impact equipment where impulse loading tears softer compounds
- Equipment converted to biodegradable ester based hydraulic fluid and the cold water side of high pressure water blast and wash equipment
- CO2 and compressed air gun systems including paintball markers, airsoft and CO2 target pistols
Key Specifications
- Size: 0.139" CS x 0.796" ID x 1.074" OD actual (3.53mm x 20.22mm x 27.28mm)
- AS568 Dash Number: -211
- Material: cast polyester polyurethane, thermoset, TODI cured (ISO 1629 AU)
- Compound: UC90, TORS designation PU-90, Freudenberg Disogrin 9251
- ASTM D2000 Line Callout: 6BG950 A14 B14 B34 EO14 EO34 F17 Z1 Z2 Z3 Z4 Z5 Z6 Z7
- Durometer: 92 plus or minus 5 Shore A nominal, 90 Shore A typical
- Color: natural, opaque white to cream
- Temperature Range: -22°F to +212°F (-30°C to +100°C) continuous, to +250°F (+121°C) intermittent, +120°F (+49°C) maximum in water or water glycol
- Maximum Working Pressure: 10,000 psi (70 MPa) with no backup ring, diametral clearance held to the standard gland tables
- Tensile Strength: 6,217 psi (42.9 MPa) certified, ASTM D412
- Elongation at Break: 566 percent certified, ASTM D412
- Tear Strength, Die C: 690 lbf/in certified, ASTM D624
- Compression Set: 18 percent typical at 70 hours and 158°F (70°C), 62 percent at 70 hours and 212°F (100°C), ASTM D395 B
- Glass Transition Temperature: -33°F (-36°C), ISO 11357-2
- Density: 1.17 plus or minus 0.02 g/cm3, ASTM D297
- Abrasion Loss: 25 to 50 mg per 1,000 cycles, Taber H-18, 1,000 g
- Regulatory: RoHS 2011/65/EU and ELV 2000/53/EC compliant with manufacturer declarations on file. Not FDA compliant and not certified to NSF/ANSI 61, NSF/ANSI 51, USP Class VI or 3-A Sanitary Standards
- Shelf Life: 5 years from cure date per SAE ARP5316 and ISO 2230, stored between 40°F and 80°F (4°C and 27°C) with relative humidity below 65 percent
Why Buy from The O-Ring Store LLC
The O-Ring Store LLC is an ISO 9001:2015 certified distributor with USA-based stock for fast delivery. Most in-stock items ship the same day. We offer custom cast sizes, full lot traceability with a cure date and lot number on every bag and a Certificate of Conformance with every shipment at no charge and no asking twice. Every batch is dimensionally verified through our Olypsys® O-Ring Measurement System, which reports the actual measured ID, cross-section and out of round rather than a pass or fail stamp. If this compound is not the right fit for your fluid, our technical staff will tell you so and point you at the one that is, including gland design help and failure analysis at no charge. We make getting O-Rings easy!
Frequently Asked Questions
Q: What are the exact dimensions of the AS568-211 UC90 O-Ring?
A: Part number UC90211 measures 0.139" cross-section x 0.796" ID x 1.074" OD actual, which is 3.53mm x 20.22mm x 27.28mm in metric. Its nominal size is 1/8" CS x 13/16" ID x 1-1/16" OD. The nominal size is the rounded name for the ring. The actual size is what it is molded to, so use the actual numbers for gland design.
Q: What gland depth should I cut for an AS568-211 UC90 O-Ring?
A: Working from the 0.139" actual cross-section, a static seal at 15 to 25 percent squeeze wants a gland depth of 0.104" to 0.118", and a dynamic seal at 8 to 12 percent squeeze wants 0.122" to 0.128". Keep the ID stretch at 5 percent or less, which means a groove diameter no bigger than 0.836" for this size, and aim for 75 to 85 percent gland fill. Give the bore or rod a 20 degree lead-in chamfer so this 90 durometer ring is not cut on assembly. Call us and we will check your drawing at no charge.
Q: How much pressure will a UC90 O-Ring hold without a backup ring?
A: The UC90 cast polyurethane O-Ring is rated to 10,000 psi (70 MPa) with no backup ring, provided the diametral clearance is held to the standard AS568 gland tables. Extrusion is driven by the gap, not by pressure alone, so if the housing flexes and the clearance opens under load, add a backup ring or tighten the fit. A 90 durometer nitrile ring typically needs backups above about 1,500 psi.
Q: Can I run a UC90 urethane O-Ring in hot water or water glycol?
A: No, not continuously above 120°F (49°C). Cast polyurethane contains ester and urethane linkages that hot water splits apart, a reaction called hydrolysis. It takes months rather than hours, so a short 70 hour test looks fine while real service life does not. Water and water glycol below 120°F (49°C) are normal service, 120°F to 160°F (49°C to 71°C) is intermittent duty only and steam is not an option at any temperature. For continuous hot water, ask us about the hydrolysis resistant grade in this same TODI family, or move to EPDM.
Q: Is the UC90 compound FDA compliant for food contact?
A: No. UC90 has not been tested or certified to FDA 21 CFR 177.2600, and it is not certified to NSF/ANSI 61, NSF/ANSI 51, USP Class VI or 3-A Sanitary Standards. Keep it out of food contact, potable water, beverage, dairy, pharmaceutical and medical device service. The O-Ring Store LLC stocks FDA compliant compounds for that work, including white FDA nitrile and FDA silicone for most food contact, EPDM for potable water and clean in place wash down where NSF/ANSI 61 is the requirement and perfluoroelastomer for pharmaceutical and high purity service.
