Sealing materials: NBR, FKM and selection
A material family such as NBR or FKM is a starting point, not a complete operating specification. Select a specific compound against the actual fluid and conditions, then verify the seal geometry and application requirements.
- Identify the exact fluid or fluid mixture, including cleaning chemicals.
- Record minimum, normal and peak temperatures and exposure duration.
- Describe pressure, motion, shaft speed where relevant, lubrication and contamination.
- Request the proposed compound grade and supporting data for the intended conditions.
What does the material name tell you?
NBR and FKM identify elastomer families. They do not by themselves establish a product-specific temperature range, hardness, certification or service life. FKM is a generic designation; a named commercial compound or trademark requires its own evidence.
How to compare two proposed compounds
Compare supplier data for the actual fluid and operating conditions using the same criteria. Ask which properties were tested, under what conditions, and whether the data applies to the supplied compound. Do not transfer ratings from a different compound or seal design.
Information to include in your enquiry
Send the product link or drawing, fluid name, operating conditions, quantities and destination. If a grade or performance limit is missing from the listing, ask for confirmation rather than assuming a value.
What makes an NBR versus FKM comparison useful?
Compare documented compounds under the same operating conditions rather than selecting from an acronym alone. Ask for the fluid compatibility evidence, the relevant temperature and duty limits, and the test basis for the proposed part. A general material-family table is a starting point, not a product rating.
What if a listing omits a pressure, speed or temperature limit?
Treat the missing value as unknown. Send the intended conditions with your inquiry and ask for confirmation of the complete seal design. Do not transfer a limit from another product merely because it uses the same material name or color.
NBR and FKM: compare the evidence, not just the label
| Selection question | For the proposed NBR part | For the proposed FKM part |
|---|---|---|
| Which compound? | Request the exact material specification | Request the exact material specification |
| Which fluid and temperature? | Confirm compatibility for the actual duty | Confirm compatibility for the actual duty |
| Same geometry? | Check profile and installation dimensions | Check profile and installation dimensions |
| Evidence required? | Applicable drawing and supporting material data | Applicable drawing and supporting material data |
Parker O-Ring Handbook: general elastomer and O-ring design background Background reference for material selection principles, not a specification or certification of VKEFOT products. Rotary shaft seals require their own application review.
Updated
Request a quote · Review product specifications
Need help specifying a seal?
Use these checks to prepare your enquiry. Final suitability depends on the specific design and operating conditions.
Check dimensions and design
Provide the shaft diameter, housing bore and seal width in mm. Include the part marking, lip profile or a dimensioned drawing if available.
Describe operating conditions
Share the fluid or medium, operating temperature, pressure and shaft speed. Confirm the material grade against the application.
Verify a replacement
Provide the original part number and photos. Similar dimensions alone do not confirm interchangeability; compare the design and material.
Selection questions
Which sealing materials do you use? How to choose for high temperature or special media?
Common compounds are NBR, FKM/FPM, PTFE and silicone, matched to media, temperature and pressure. Engine oil near 120°C or fuel/high-heat duty usually needs FKM review; general mineral oil at moderate temperature often stays NBR. Share temperature, media and motion; the quote names the grade and its limits.
NBR vs FKM oil seal for hot engine oil?
Continuous engine-oil duty near 120°C or fuel exposure should be reviewed as FKM; general mineral oil at moderate temperature and cost-sensitive repair jobs often stay NBR. Brown color is not proof of FKM. The quote names the grade and temperature limit — do not order by color.
How to select oil seals for ag gearbox and PTO shafts?
Ag gearboxes and PTO shafts see dust and shock — prefer a dust lip or cassette, with NBR or FKM matched to gear oil and temperature. Do not force a passenger-car hub seal onto a PTO shaft. Send shaft, bore, height and whether mud/water is present, then RFQ.