Buna-N 70 Vulcanized O-Ring 100% Size and Joint Guarantee
The Buna-N 70 Vulcanized O-Ring is a custom O-Ring made from Buna-N (Nitrile, NBR) cord, spliced and vulcanized into one continuous ring at the exact size you order. It seals petroleum oils, fuels, hydraulic fluids and water from -40 to +250F (-40 to +121C). The O-Ring Store LLC makes every ring to the size you order, verifies it with an Olypsys® scan and replaces it if the joint or the size is ever wrong.
Get the exact O-Ring your gland needs without waiting weeks on a mold. We cut Buna-N 70 cord to length, splice it and vulcanize the joint into one continuous ring. There is no tooling to pay for, so one O-Ring is as easy to order as a hundred. Maintenance crews use these rings to get a pump, cylinder or tank lid back in service fast. Engineers and OEMs use them when a design calls for a size nobody molds.
The Best Vulcanized O-Rings in the World, and We Prove It
We make it to the size you order. Then we prove it. On orders up to 100 pieces, every single O-Ring goes on our Olypsys® scanner. On orders over 100 pieces, we scan a 10 percent sample pulled from the lot. You get the Olypsys® Measurement Verification Report with the measured ID, OD and cross-section, so you have the numbers in hand before the ring ever touches your machine. If a joint fails or a ring is not the size you ordered, we replace it. That is a 100 percent guarantee with no fine print. Other shops tell you their splices are good. We send you the proof and put our name on it.
Operating Temperature: -40 to +250F (-40 to +121C)
Material and Performance
Buna-N, also called Nitrile or NBR, is the workhorse elastomer for oil and fuel service. At 70 durometer Shore A it is firm enough to resist extrusion in most static glands and soft enough to seal on ordinary machined surfaces. The standard color is black. Buna-N 70 has good tensile strength, strong abrasion resistance and low compression set. It also stays dimensionally stable, which matters on a large ring that has to hold its shape in the groove.
- Excellent resistance to: petroleum oils, fuels (gasoline and diesel), hydraulic fluids (petroleum-based), mineral oils, silicone greases and oils, water, ethylene glycol and LP gases
- Limited capability with: dilute acids and long-term sunlight (UV) exposure
- Not compatible with: strong acids, ozone, ketones (acetone and MEK), halogenated hydrocarbons (carbon tetrachloride), phosphate ester hydraulic fluids (Skydrol), automotive brake fluid, nitro hydrocarbons and aromatic hydrocarbons
Applications and Use Cases
The Buna-N 70 Vulcanized O-Ring seals hydraulic cylinders, pump housings, valve bodies, tank and hatch covers, filter housings, gearbox covers and large flanges in oil, fuel, hydraulic fluid and cold water service. It is a go-to for MRO emergencies, when a machine is down and the original seal is an odd size or years out of production. One honest note most suppliers leave out: a vulcanized joint is at its best in static and slow-moving seals. If you run a high-cycle reciprocating rod or piston and a standard molded AS568 size fits your gland, buy the molded ring. Call us and we will tell you straight which one fits your job.
Key Specifications
- Material: Buna-N (Nitrile, NBR)
- Durometer: 70 Shore A
- Color: Black
- Temperature Range: -40 to +250F (-40 to +121C)
- Construction: extruded Buna-N cord, spliced and vulcanized into one continuous ring
- Size: made to the size you order, verified by Olypsys® scan
- Inspection: every O-Ring scanned on orders up to 100 pieces; 10 percent sample scan on orders over 100 pieces
- Documentation: Olypsys® Measurement Verification Report with measured ID, OD and CS
- Guarantee: 100 percent; any failed joint or wrong-size ring is replaced
- Lead Time: up to 24 pieces about 2 to 5 days ARO; 25 to 100 pieces about 5 to 10 days ARO; over 100 pieces about 10 to 15 days ARO (depends on cord stock)
Why Buy from The O-Ring Store LLC
The O-Ring Store LLC is an ISO 9001:2015 certified distributor with USA-based stock, and most in-stock items ship the same day. Nobody in the world does vulcanized O-Rings better than we do, and we prove it on every order with an Olypsys® scan report in your hands. Every ring is made to the size you order and every joint is guaranteed, so buying from us carries zero risk. You also get full lot traceability and documentation on request, plus technical help from people who have spent decades sizing and specifying seals. Use our O-Ring Cord Cut-Length Calculator to check your numbers, or send us the gland size and we will figure it out with you. We make getting O-Rings easy!
Frequently Asked Questions
Q: How do I know a custom Buna-N 70 vulcanized O-Ring will be the size I ordered?
A: The O-Ring Store LLC makes every Buna-N 70 Vulcanized O-Ring to the size you order and proves it with an Olypsys® scan. Orders up to 100 pieces get every single O-Ring scanned, and orders over 100 pieces get a 10 percent sample scan. You receive the Olypsys® Measurement Verification Report, and if a ring is not the size you ordered, we replace it.
Q: Is a spliced and vulcanized Buna-N O-Ring as strong as a molded O-Ring?
A: A Buna-N 70 vulcanized O-Ring from The O-Ring Store LLC carries a 100 percent joint guarantee and performs like a molded ring in static seals and slow-moving service. For high-cycle reciprocating rods and pistons, a molded AS568 O-Ring is the better choice when a standard size fits your gland. The vulcanized ring wins when you need an odd size, one piece or a fast turnaround.
Q: What temperatures and fluids can a Buna-N 70 vulcanized O-Ring handle?
A: A Buna-N 70 vulcanized O-Ring seals from -40 to +250F (-40 to +121C). It has excellent resistance to petroleum oils, gasoline, diesel, petroleum-based hydraulic fluids, silicone greases and water. Do not use it with ketones like acetone or MEK, Skydrol, brake fluid, strong acids or ozone.
