AS568-001 B70 (NBR) Buna-N Nitrile 70 Duro O-Ring

1/32"ID X 3/32"OD X 1/32"CS

Buna-N O-Rings 70 Duro (NBR):

The most commonly used elastomer for sealing products. Nitrile, also known as Buna-N or NBR, is a copolymer of Butadiene and Acrylonitirle. It has a temperature range of -40F to +250F and is exceptionally resistant to petroleum base oils and hydrocarbon fuels. Nitrile materials also exhibit excellent tensile strength and abrasion resistance properties. The material performs well with most dilute acids, silicone oils and lubricants and in water applications. It is not recommended for use with ketones, aromatic hydrocarbons and phosphate ester hydraulic fluids. More than 50% of the Orings sold are Nitrile Orings, commonly used in hydraulic/pneumatic motors, cylinders, pumps and valves.

Buna-N / Nitrile Recommended uses:

  • General purpose sealing.
  • Petroleum oils and fluids.
  • Gasoline
  • Hydraulic fluids
  • L.P. gases
  • Cold Water.
  • Silicone greases and oils
  • Di-ester base lubricants (MIL-L-7808).
  • Ethylene glycol base fluids (Hydrolubes)

Nitrile is not recommended for:

  • Halogenated hydrocarbons (carbon tetrachloride, trichloroethylene)
  • Nitro hydrocarbons (nitrobenzene, aniline)
  • Phosphate ester hydraulic fluids (Skydrol, Fyrquel, Pydraul).
  • Ketones (MEK, acetone)
  • Ozone
  • Sunlight, UV
  • Weather
  • Strong Acids Ozone
  • Automotive brake fluid

Compound Info:

  • A general purpose, sulfur-cured Nitrile (Buna-N) compound
  • Color: Black
  • Duro: 70
  • FDA: No
  • ASTM D2000-99 Grade M2BG714 B14 EA14 EF11 EF21 EO14 EO34 Z1=TR10= -31.9C
  • B70 is designed to meet or exceed the properties of these popular Buna Nitrile Compounds:
    N674-70, N100-70, 7507, B46-70, 4200-70, H14327, 4700-70 and 366Y

Operating temperature: -40° to +250°F


Qty Discounts Prices
  • Model: B70001
    Dimensions: 1/32"ID X 3/32"OD X 1/32"CS
    Actual: 0.029"ID X 0.040"CS
    Metric: 0.74mm ID X 1.02mm CS
  • PDF Data Sheet
  • 687,482 in Stock
Add to Cart:
Min Qty:  100

 O-Ring Squeeze Compression

(O-Ring C/S) - Gland Depth / (O-Ring C/S)

  • Face seal:20-30%
  • Static Male/Female: 18-25%
  • Reciprocating: 10-20%
  • Rotary: 0-10%

O-Ring Installed Stretch

(Groove Diameter) - (O-Ring ID)(O-Ring ID)

  • General rule is 0-5%
  • Excessive stretch can overstress material, thin cross section, and reduces % squeeze
  • % cross section reduction due to stretch about half of the % ID stretch

  O-Ring Application Pressure  Vs. O-Ring Gland Clearance Gap Size

  • Excessive clearance and or pressure can result in sealextrusion and failure
  • Durometer vs. Pressure and Clearance Gap Chart
  • Consider use of Back-Ups or product selection with large gaps or > pressure

O-Ring Tolerances

  • Tolerances should be considered for the O-Ring and the gland
  • Can impact sealing performance and life

O-Ring Gland Surface Finish

  • Seal material must fill in voids in surface
  • Static surfaces

           - 32Ra to seal liquid

           -16Ra to seal gas

  • Dynamic Surfaces: 8 to 16Ra
  • Too rough of a surface can result in abrasion or spiraling, even with a static seal
  • Lower durometer materials can be used to seal rough surface finishes

O-Ring Gland Sharp Corners

  • Corners should be chanpfered to limit  damage during seal installation

O-Ring Gland Fill %
O-Ring Volume) / (Gland Volume)

  • Gland volume vs. O-Ring volume
  • About 25% void space or 75% nominal fill
  • Need space in groove to allow for volume swell, thermal expansion, and increasing width due to squeeze
  • Narrower groove for sealing vacuum or gas
  • O-Ring can extrude into clearance gap or get squeezed in two directions

O-Ring Eccentricity & Side Loading

  • Too much squeeze on one side and not enough on the other or none at all
  • Can open too wide a clearance gap and result in extrusion of one portion of seal leading to leaks


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