Oil seal materials · Nitrile rubber (NBR)
NBR oil seals are the general-purpose choice for oil-resistant rotary shaft sealing. Made from nitrile butadiene rubber, they hold lubricating oil and grease where it belongs and keep dust, moisture and abrasive particles out of the bearing chamber — in gearboxes, pumps, motors and machinery of every size.
Nitrile rubber resists many petroleum-based oils and greases at a reasonable cost, which is why it is the most widely specified oil-seal material. The right compound still depends on the fluid, temperature, speed and contamination of your application — share the details and we will help you confirm the fit.
* Typical values for general-purpose nitrile compounds, shown for orientation only. The selected compound’s data sheet and your operating conditions govern the actual limits.
The basics
A short, plain-language answer for buyers who need to know what they are specifying — and why nitrile rubber is the default choice for oil-contact sealing.
An NBR oil seal is a radial shaft seal whose flexible sealing element is made from nitrile butadiene rubber — usually shortened to NBR or called nitrile rubber. The seal closes the small gap between a rotating shaft and the housing around it, holding lubricating oil or grease inside the bearing or gear chamber and keeping dust, moisture and abrasive particles out.
NBR stands for nitrile butadiene rubber, a synthetic elastomer produced by copolymerising acrylonitrile and butadiene. The acrylonitrile content gives the material its resistance to oils and fuels; grades with more acrylonitrile resist oil and heat better, while grades with less stay flexible at lower temperatures. That balance is set in the compound — which is why two “NBR” seals can behave very differently in service.
A rotary shaft oil seal has one job with two sides: keep the lubricant in and keep contamination out. Its shaped lip presses against the spinning shaft with a controlled contact force, usually maintained by a small garter spring. The lip carries a thin oil film that lubricates the contact, while the case holds the seal firmly in the housing bore. When the seal is correctly selected, bearings stay lubricated, oil stays off the floor, and the machine keeps its designed service life.
Seals rarely fail because they were badly moulded — they fail because the compound was wrong for the fluid, the temperature or the speed. Nitrile rubber is the most widely used oil-seal material because it resists many petroleum-based oils and greases at a reasonable cost. But no rubber suits every duty: before ordering, the seal material should be matched against the fluid being sealed, the operating temperature, the shaft speed, the pressure and the level of contamination.
Material properties
General characteristics of nitrile rubber as an oil-seal material. Actual performance always depends on the rubber compound, the seal design and the operating conditions.
NBR is well suited to many mineral-based oils, greases and mineral-oil hydraulic fluids — the media most rotating machinery runs on. Fluid compatibility still varies by compound and must be confirmed for the exact lubricant.
A nitrile lip follows small shaft movements, run-out and surface variations while keeping steady contact pressure — the combination a dynamic rotary seal needs to hold oil without wearing the shaft.
Within its working envelope — suitable shaft finish, speed and temperature — an NBR lip wears gradually and predictably instead of degrading early, giving stable sealing life in daily service.
From gearbox and pump shafts to agricultural and automotive positions, nitrile rubber oil seals cover a wide share of everyday sealing duties at moderate temperatures and speeds.
Seals are sized to the shaft diameter, housing bore and width of the application. Standard and non-standard dimensions can both be discussed against your requirement and quantity.
Where a duty needs different hardness, fluid resistance or temperature behaviour, custom compound specifications can be discussed — subject to review of the application and quantity before ordering.
Performance is application-specific. How an NBR oil seal behaves in service depends on the rubber compound, the temperature, the composition of the fluid, the pressure, the shaft speed, the shaft surface finish and the overall operating conditions. Nitrile rubber is not resistant to every oil, chemical, fuel or environment — confirm the compound against the actual duty before ordering.
Seal configurations
“NBR” describes the material of the sealing element — the lip design and casing decide how the seal handles dust, pressure and assembly. These are the configurations commonly specified for nitrile rotary shaft seals. Availability of a specific construction is confirmed against our product range for each enquiry.
The standard radial lip seal for rotating shafts in relatively clean environments — gearboxes, electric motors and housings protected from splash and grit. One nitrile lip retains the lubricant and excludes light contamination.
A secondary lip shields the main sealing lip from dust, mud, splash and slurry. The extra lip is worth specifying on farm machinery, construction equipment and any housing open to the weather or to washdown.
A garter spring holds constant contact pressure on the shaft as the lip wears and as temperature moves. Most rotary shaft seals use this arrangement, because it keeps sealing force stable over long service periods.
Without a garter spring, these seals suit slower shafts, greased assemblies and positions where retention of a soft grease or light fluid is the priority. They are simpler and more compact than spring-loaded types.
The nitrile element is carried in a fully rubber-covered case, which seats gently in the housing and tolerates slight bore imperfections. Useful where a metal case could corrode, squeal or damage a light alloy housing.
A rigid metal case keeps the seal round and gives a firm press fit in the housing bore. This construction suits sturdy housings and higher-duty positions where dimensional stability matters most.
Non-standard sections, combined profiles and seals matched to an existing housing are discussed from a drawing, a sample or the machine details. Feasibility, tooling and quantities are confirmed before any commitment.
Where they work
Typical sealing positions where nitrile rubber oil seals are commonly specified. Suitability always depends on the actual fluid, temperature, speed and contamination of the machine.
Machine tools, mixers, crushers and processing lines need shaft seals that hold lubricant through daily duty cycles. NBR suits the mineral oils and greases most industrial gearboxes and bearings run on.
Pump shafts and motor bearing chambers need a lip that keeps oil in and workshop dust out. Sealing requirements rise with speed and pressure, so the pump media and rpm should be stated when enquiring.
Input and output shafts run in warm gear oil — a classic NBR duty. Continuous operating temperature at the lip, not just the machine’s rating, decides which compound grade will hold up.
Tractors, rotavators and harvesters work in dust, mud and crop residue. Double-lip NBR shaft seals keep grit away from the main sealing edge while holding gear and hydraulic oils inside the housing.
Engines, axles, wheel hubs and auxiliary drives seal engine and gear oils in dusty, hot surroundings. Nitrile rubber is widely used here, with the grade matched to the fluid and temperature of each position.
Where the seal design and operating conditions are appropriate, NBR suits mineral-oil hydraulic circuits and lubricated pneumatic assemblies. Pressure duty needs purpose-rated constructions, not a standard lip alone.
Conveyors, fans, blowers, generators and workshop machines — wherever a shaft turns through a housing, a correctly sized NBR oil seal protects the bearing it serves at a sensible cost.
Not a universal fit. A standard nitrile oil seal is not automatically suitable for every pressure, speed, temperature or fluid condition. Describe the machine and its duty when you enquire, and the appropriate material and design can be confirmed before you order.
Technical data
Seals are supplied against the requirement of the application. The table below describes the specification fields involved — actual dimensions, material grades and operating limits for your enquiry are confirmed before ordering.
| Specification | Details |
|---|---|
| Material | Nitrile butadiene rubber (NBR) — also called nitrile rubber or Buna-N; compound grade matched to the application |
| Product type | Rotary shaft oil seals (radial lip seals) and related machine sealing positions, where the design suits the duty |
| Dimensions | Inner diameter (shaft), outer diameter (housing bore) and width (housing depth) — manufactured to requirement; confirm the range for your size |
| Lip configuration | Single lip or double lip — the second lip adds protection where dust, splash or slurry is present |
| Spring design | Spring-loaded (garter spring) or non-spring-loaded, selected against shaft speed and the fluid being retained |
| Casing configuration | Metal-cased or rubber-covered constructions, matched to the housing material and environment |
| Operating temperature | Depends on the compound. General-purpose NBR compounds are typically quoted from about −40 °C to +120 °C continuous — an indicative range only; confirm the limit for the specific grade |
| Fluid compatibility | Generally suited to many petroleum-based oils, greases and mineral hydraulic fluids; not suitable for every fluid — verify against the actual media and temperature |
| Shaft speed & conditions | Surface speed, pressure, shaft finish and contamination decide the lip profile and compound — share the operating conditions with your enquiry |
| Customization | Dimensions, compound grade, hardness, lip design and casing discussed against application requirements and quantity |
Ananta Venture does not publish generic performance limits, because safe values depend on the compound and the duty. Temperature and compatibility figures above are indicative ranges for general-purpose nitrile compounds, shown for orientation only — the selected compound’s technical data sheet and your operating conditions govern the actual limits.
Buyer’s perspective
A practical look at when nitrile rubber is the sensible sealing material — and what buyers gain by specifying it for the right duty.
Nitrile rubber resists many of the petroleum-based oils, greases and mineral hydraulic fluids that rotating machinery actually runs on — the reason it remains the default oil-seal material across industry.
From gearboxes and pumps to tractors and conveyors, the same material family covers a wide spread of machines, which simplifies spares planning and procurement across a plant or a fleet.
Where offered, NBR oil seals are available in multiple standard sizes — and sizes to requirement can be discussed from your dimensions, drawing or sample, subject to confirmation.
Choosing NBR is not a default — it is a selection. Share the fluid, temperature, speed and contamination of the duty, and the compound and lip design are chosen to match rather than assumed.
For machinery running in mineral oils at moderate temperatures, nitrile rubber delivers reliable sealing at a lower cost than specialty elastomers — paying more for FKM or silicone only makes sense when the duty demands it.
Working with us
Ananta Venture is a Delhi-based manufacturer and supplier of rubber oil seals — including nitrile rubber (NBR) shaft seals — for industrial, automotive, agricultural and heavy machinery applications. Enquiries are answered with product options matched to the application, not just the closest catalogue number.
A quotation is only as good as the information behind it. The points below let the appropriate seal, compound and price be confirmed in one pass instead of five emails.
No obligation, no guesswork. Requirements are reviewed before any commitment — dimensions, material suitability, quantities and lead times are confirmed with you first, so the quote you receive reflects what can actually be supplied.
Material comparison
There is no best sealing rubber — only the material that matches your fluid, temperature, pressure and motion. The table compares the four elastomers buyers ask about most.
| Material | Typical temperature | Oil & lubricant compatibility | Weather & ozone | Often considered for | Main limitation |
|---|---|---|---|---|---|
| NBR (nitrile) This page | About −40 °C to +120 °C* | Excellent with mineral oils, greases and hydraulic fluid | Moderate | General oil sealing, hydraulic components, automotive and industrial shafts | Limited heat and ozone resistance; hardens with age |
| FKM (fluoroelastomer) | About −20 °C to +200 °C* | Excellent with oils, fuels and many chemicals | Excellent | High-temperature oil and fuel sealing, chemically demanding duty | Higher cost; poorer low-temperature flexibility; not for some esters, ketones and amines |
| Silicone (VMQ) | About −60 °C to +200 °C* | Poor to moderate in hydrocarbon oils; better with some synthetic and silicone fluids | Excellent | Heat, cold, outdoor exposure, static seals, electrical insulation | Swells in many oils and fuels; lower tear and abrasion resistance |
| PU (polyurethane) | About −40 °C to +90 °C* | Good with many mineral oils and hydraulic fluids, grade-dependent | Moderate | Abrasive, high-load and reciprocating hydraulic sealing duties | Hydrolysis in hot water; heat build-up limits rotary lip service |
*Figures are indicative ranges for orientation and will not match every grade. Confirm the actual limits, fluid compatibility and compression set on the data sheet of the compound offered, and test where the duty is severe or safety-related.
Reading the table: NBR is the economical general-purpose material for machinery in mineral oils and greases at moderate temperatures. FKM earns its cost in hot-oil, fuel and chemically aggressive duties. Silicone wins on temperature span and weathering but is rarely the choice for dynamic oil-wetted lips. Polyurethane excels where abrasion and load dominate — typically reciprocating hydraulic service rather than rotary shaft sealing. The correct choice follows from the temperature, the fluid, the mechanical requirements and the intended application of your machine.
For duties at the edge of NBR’s range, a silicone oil seal or an FKM grade may be the better answer — or an HNBR compromise. Describe the duty and the options can be compared honestly.
Buyer questions
Short, direct answers to the questions that come up most often on NBR oil seal enquiries. Full technical answers depend on the compound offered and the conditions it will meet.
NBR oil seals are radial shaft seals made from nitrile butadiene rubber. They are fitted around rotating shafts to retain lubricating oil or grease inside a housing and to keep dust, moisture and other contaminants out of the sealed chamber.
NBR stands for nitrile butadiene rubber (also called nitrile rubber or Buna-N) — a synthetic elastomer produced by copolymerising acrylonitrile and butadiene. Its oil resistance comes from the acrylonitrile content of the compound.
Nitrile rubber oil seals offer good resistance to many petroleum-based oils, greases and mineral hydraulic fluids, together with the elasticity and abrasion resistance a rotating lip needs. They are a cost-effective general-purpose choice for machinery that runs in mineral oil at moderate temperatures.
NBR oil seals are generally compatible with mineral-based engine oils, gear oils, greases and mineral-oil hydraulic fluids, and are commonly used with petrol and diesel fuels subject to the compound. They are generally not suitable for polar solvents such as ketones and esters, glycol-based brake fluids, or highly aromatic and chlorinated fluids. Compatibility must be confirmed for the exact fluid and temperature.
The working temperature of an NBR oil seal depends on the compound. General-purpose nitrile compounds are typically quoted for continuous service from about −40 °C to +120 °C, with special grades extending either end. The figure is indicative only — the compound data sheet and the actual duty govern the real limits.
Start by measuring the shaft diameter, housing bore and seal width. Then confirm the fluid being sealed, the operating temperature, the shaft speed, the pressure and the level of contamination. Sharing these details — or the old seal, drawing or part number — with the supplier is the most reliable way to arrive at the correct seal.
FKM (fluoroelastomer) seals withstand higher continuous temperatures and a broader range of aggressive fluids than NBR, at a higher cost and with less low-temperature flexibility. NBR is the cost-effective general-purpose material for machinery running in mineral oils and greases at moderate temperatures, while FKM is considered for hot-oil, fuel and chemically demanding duties.
Sizes to requirement can be discussed. Share the inner diameter, outer diameter and width — or a drawing, sample or part number — together with the application and quantity, and the supplier will confirm the available options, minimum quantities and lead times before you order.
Next step
Tell us what the seal has to do — the dimensions, the fluid, the temperature, the speed and the quantity — and we will come back with the options that fit, or tell you honestly if a different material is the better answer.
Send the shaft diameter, housing bore and width if you have them, or simply a photograph of the old seal, its part number, or the name of the machine it protects. A call, a WhatsApp message or an email reaches the same team and gets an answer faster.
No prices are published on this page. Quotations depend on size, compound, quantity and tooling, and are confirmed after your requirement is reviewed.