5/8" ID X 7/8" OD X 1/8" HT
The HRU12-0.62-12V is a homogeneous U-Seal molded from 90 durometer Viton® FKM fluorocarbon. It fits a 5/8" (0.625") rod in a 7/8" (0.875") bore with a 0.156" groove width. It is rated from -20 to +400F (-29 to +204C), up to 2,000 PSI (138 bar) and up to 3 feet per second (0.91 m/s).
Keep a hot cylinder from weeping oil with the HRU12-0.62-12V Viton® U-Seal. A U-Seal has two flexible sealing lips. System pressure pushes those lips out against the rod and the groove, so the seal grips harder as pressure climbs. That makes it a strong choice for reciprocating rods and pistons that see heat, fuel or harsh oils.
"Homogeneous" means the whole seal is one piece of one compound. There is no fabric layer and no O-Ring energizer inside, so there is nothing to separate or roll out of the groove. The 90 durometer Viton® FKM is firm enough to resist extrusion in a 2,000 PSI system. The lips stay flexible enough to seal at low pressure. The O-Ring Store LLC carries the HRU12-0.62-12V for maintenance shops, OEMs and rebuilders who need a 5/8" x 7/8" x 1/8" U-Seal that holds up to heat.
Operating Temperature
-20 to +400F (-29 to +204C)
Material and Performance
The HRU12-0.62-12V 5/8" x 7/8" U-Seal is made from Viton® FKM, also called fluorocarbon or fluoroelastomer. At 90 Shore A durometer, it is a hard sealing compound that stands up to pressure and resists being pushed into the clearance gap. Viton® FKM holds its shape at high heat and has excellent compression set resistance, so the lips keep their sealing force after long runs at temperature. It also resists the petroleum oils, fuels and hydraulic fluids that swell or harden lesser rubbers. Here is the honest limit: Viton® FKM is the wrong choice for steam, phosphate ester fluids and ketones such as MEK or acetone. For those, an EPDM seal is usually the better fit.
Excellent resistance to: petroleum oils, petroleum-based hydraulic fluids, fuels (gasoline, diesel, JP-8), aromatic fuels, chlorinated solvents, mineral acids, dilute acids and silicone fluids
Limited capability with: steam, hot water above 300F (149C), low molecular weight esters and some ketones
Not compatible with: ketones (MEK, acetone), amines, anhydrous ammonia, hot water above 400F (204C), ethylene oxide, phosphate ester fluids such as Skydrol 500B-4 and low molecular weight organic acids
Sizes and Measurements
Nominal Size: 5/8" ID x 7/8" OD x 1/8" CS x 1/8" Height
Metric: 15.88mm ID x 22.23mm OD x 3.18mm CS x 3.18mm Height
Rod Diameter: 0.625" (15.88mm)
Bore Diameter: 0.875" (22.23mm)
Groove Diameter (H): 0.625" (15.88mm)
Groove Width (D): 0.156" (3.96mm)
Groove Width with Backup Ring (D1): 0.219" (5.56mm)
Housing Diameter (G): 0.875" (22.23mm)
Piston Diameter (I): 0.873" (22.17mm)
Throat Diameter (F): 0.626" (15.90mm)
Part Number: HRU12-0.62-12V
Cross-references: 5/8" x 7/8" x 1/8" U-Seal, 15.88mm x 22.23mm x 3.18mm U-Seal (size match only, so confirm lip style, height and compound before you swap)
Applications and Use Cases
The HRU12-0.62-12V Viton® U-Seal works in hydraulic cylinders, actuators and pumps with a 5/8" rod or a 7/8" bore that run hot or handle fuel and harsh oils. Look for it on cylinders mounted near engines and exhaust and on mobile and ag equipment. It also works on plant hydraulics next to ovens, furnaces or molding machines, plus fuel and lube oil transfer equipment. The data sheet lists gland dimensions for both a rod install and a piston install. Install it with the open side of the U facing the pressure. U-Seals are built for back-and-forth motion up to 3 feet per second (0.91 m/s), not for a spinning shaft. If your cylinder runs colder than -20F (-29C) or never sees heat or chemicals, ask us whether a different compound will do the job for less money.
Key Specifications
Material: Viton® FKM fluorocarbon (fluoroelastomer)
Seal Type: Homogeneous U-Seal
Durometer: 90 Shore A
Color: Black
Temperature Range: -20 to +400F (-29 to +204C)
Pressure Rating: 0 to 2,000 PSI (0 to 138 bar)
Speed: Up to 3 ft/sec (0.91 m/s)
Weight: 0.0020 lbs (0.91 g)
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 full lot traceability and documentation on request. Our technical help comes from people with decades of sealing experience. Not sure the HRU12-0.62-12V 5/8" x 7/8" Viton® U-Seal fits your gland? Send us your rod, bore and groove measurements and we will check them against the numbers on this page. Every order is verified through our Olypsys® scan-based quality system before it ships. We make getting O-Rings easy!
Frequently Asked Questions
Q: What gland does the HRU12-0.62-12V U-Seal fit? A: The HRU12-0.62-12V Viton® U-Seal fits a 0.625" (15.88mm) rod or groove diameter in a 0.875" (22.23mm) bore, with a groove width of 0.156" (3.96mm). If you add a backup ring, the groove width goes to 0.219" (5.56mm). The nominal seal size is 5/8" ID x 7/8" OD x 1/8" cross-section x 1/8" height.
Q: How much pressure and speed can the HRU12-0.62-12V handle? A: The HRU12-0.62-12V 90 durometer Viton® FKM U-Seal is rated from 0 to 2,000 PSI (138 bar) at speeds up to 3 feet per second (0.91 m/s). If your 5/8" x 7/8" gland has a large clearance gap or sees pressure spikes, use the 0.219" (5.56mm) backup ring groove width to help keep the seal from extruding.
Q: Can I use the HRU12-0.62-12V Viton® U-Seal with steam or Skydrol? A: No. The HRU12-0.62-12V is 90 durometer Viton® FKM, which is not compatible with phosphate ester fluids such as Skydrol 500B-4 and is limited in steam and hot water above 300F (149C). This 5/8" x 7/8" U-Seal is the right call for petroleum oils, fuels and petroleum-based hydraulic fluid up to +400F (+204C). For steam or phosphate ester hydraulics, an EPDM seal is usually the better fit.
