Product Overview
Reliable custom rubber parts for industrial applications
Quick Answer
This brown FKM O-ring assortment is designed for industrial sealing, repair kits, maintenance programs and equipment assembly. Inner diameter, cross-section, Shore A hardness, dimensional tolerance, size quantity, FKM compound grade, packaging and labeling can be customized according to the sealing conditions and buyer requirements.
Brown FKM (Viton®) O-Ring Assortment — Chemical & High-Temperature Industrial Seal Kit, AS568A / ISO 3601, Shore A 75
This brown FKM O-ring assortment includes multiple fluoroelastomer O-ring sizes for industrial sealing applications involving heat, oil, fuel, chemical media or demanding service conditions. Each O-ring is designed for groove installation and controlled compression between compatible mating components. Size range, Shore A hardness, tolerance, packaging and documentation options can be customized according to the application requirements.
Product Overview
The brown FKM O-ring assortment is designed for industrial users, maintenance teams, OEM assemblers and distributors that require multiple O-ring sizes in one supply program. FKM is commonly selected where standard rubber compounds may not provide sufficient resistance to elevated temperature, oils, fuels or selected chemical media. Each O-ring has a circular shape with a round cross-section and is installed in a groove to create a static or selected dynamic seal. The brown color helps identify the material during storage, assembly and maintenance. Final sealing performance depends on the O-ring size, groove design, compression rate, operating temperature, pressure, contact media and dimensional tolerance.
Product Specifications
| Attribute | Value |
|---|---|
| Product Name | Brown FKM O-Ring Assortment |
| Material | FKM — Fluorocarbon Elastomer (Viton® is a registered trademark of The Chemours Company) |
| Also Known As | FPM O-Ring (ISO/DIN designation); Fluororubber O-Ring; Fluoroelastomer O-Ring |
| Color | Brown (standard FKM color — universal visual identification) |
| Hardness | Shore A 75 (standard); 60A, 80A, 90A available |
| Standard Series | AS568A Imperial; ISO 3601 Metric; DIN 3771; BS 1806; JIS B2401 |
| CS Range | 1.0 mm to 10.0 mm (inch: 1/16″ to 3/8″) |
| ID Range | 1.5 mm to 400 mm standard; larger lathe-cut on request |
| Temperature Range | -20°C to +200°C continuous; up to +230°C high-temp FKM grade |
| Pressure Rating | Static: up to 200 bar (with back-up rings); Dynamic: up to 80 bar |
| Assortment Kit Options | 436-piece / 36-size industrial repair kit (AS568A); custom BOM kits |
| Certifications | RoHS; REACH; FDA 21 CFR 177.2600 (FDA-grade FKM available); AS9100 (aerospace) |
Why Brown? — FKM Color Identification Convention
Brown is the universally adopted color code for standard FKM fluorocarbon O-rings across the global sealing industry. In a multi-compound workshop environment, visual identification before installation is a critical quality control step — installing an NBR O-ring in a fuel or solvent application, or using an EPDM O-ring in an oil system, causes rapid seal failure with potential equipment damage and safety consequences.
The industry color coding system provides instant compound identification:
| Color | Compound | Primary Strength |
|---|---|---|
| Black | NBR | Oil, hydraulic fluid |
| Black | EPDM | Water, steam, outdoor |
| Red | VMQ Silicone | High temperature, FDA |
| Brown | FKM (Viton®) | Chemical, fuel, high temp oil |
| Green | FKM (low-temp grade) | Low-temp chemical service |
| White/Translucent | PTFE / VMQ | Chemical inertness, pharma |
| Yellow/Tan | FFKM | Ultimate chemical/temp |
Brown FKM at Shore A 75 is the standard specification — harder than typical NBR 70A to compensate for FKM’s inherently lower compression set resistance and to reduce extrusion risk at higher operating pressures.
FKM — Material Science & Key Properties
FKM (Fluorocarbon Rubber) belongs to the fluoroelastomer family — polymers in which fluorine atoms replace hydrogen atoms on the carbon backbone, creating C-F bonds with the highest bond dissociation energy of any C-X bond in organic chemistry. This molecular architecture is the basis for FKM’s unique combination of chemical inertness, thermal stability, and resistance to oxidative degradation that no hydrocarbon-based rubber can approach.
Chemical Resistance — Broadest Spectrum of Any Standard Elastomer
FKM resists the widest range of aggressive industrial chemicals of any standard O-ring compound:
| Chemical Class | Examples | FKM Rating |
|---|---|---|
| Petroleum oils | Mineral oil, gear oil, hydraulic oil | ✅ Excellent |
| Synthetic hydraulic fluids | Phosphate ester (Skydrol), polyol ester | ✅ Excellent |
| Aliphatic hydrocarbons | Petrol, diesel, kerosene, butane, propane | ✅ Excellent |
| Aromatic hydrocarbons | Benzene, toluene, xylene | ✅ Excellent |
| Chlorinated solvents | Trichloroethylene, carbon tetrachloride | ✅ Excellent |
| Concentrated mineral acids | Sulfuric acid, hydrochloric acid (dilute-moderate) | ✅ Good |
| Fuels | Jet fuel (Jet A, JP-4, JP-8), biodiesel blends | ✅ Excellent |
| High vacuum | 10⁻⁸ Torr and below | ✅ Excellent |
| Ozone / weathering | Atmospheric, outdoor | ✅ Excellent |
| NOT suitable for: | Ketones (acetone, MEK), esters, amines, steam above +120°C | ❌ Not recommended |
Temperature Performance
FKM provides the second-highest upper temperature limit of any standard O-ring compound — exceeded only by VMQ silicone and FFKM perfluoroelastomer:
| Compound | Continuous Upper Temp | Lower Temp Limit |
|---|---|---|
| FFKM (Kalrez®) | +320°C | -20°C |
| VMQ Silicone | +250°C | -60°C |
| FKM (standard) | +200°C | -20°C |
| FKM (high-temp grade) | +230°C | -20°C |
| FKM (low-temp grade, GF) | +200°C | -40°C |
| HNBR | +150°C | -40°C |
| EPDM | +150°C | -50°C |
| NBR | +100°C | -40°C |
Key limitation: FKM’s lower temperature limit of -20°C (standard grade) is significantly higher than NBR (-40°C) and VMQ (-60°C). For applications requiring both chemical resistance and low-temperature flexibility below -20°C, specify low-temperature FKM (GF type) with a lower limit of -40°C.
Key Physical Properties (Brown FKM Shore A 75)
| Property | Test Method | Value |
|---|---|---|
| Hardness | ISO 48-4 / Shore A | 75 ± 5 |
| Tensile Strength | ISO 37 / ASTM D412 | ≥ 10 MPa |
| Elongation at Break | ISO 37 | ≥ 150% |
| Compression Set | ISO 815 (22h @ 200°C) | ≤ 20% |
| Volume Change in Oil | ISO 1817 (IRM 903, 70h @ 150°C) | ≤ +5% |
| Heat Aging | ISO 188 (70h @ 200°C) | ≤ ±15% |
| Low Temp Flexibility | ISO 812 | -20°C (TR10) |
| Gas Permeability | Relative | Very low |
| Density | ISO 2781 | 1.80–1.95 g/cm³ |
| Ozone Resistance | ISO 1431-1 | Excellent — no cracking |
Standard ISO 3601 Metric FKM Brown 75A (Selected Sizes)
| ID (mm) | CS (mm) | OD (mm) |
|---|---|---|
| 3.0 | 1.5 | 6.0 |
| 5.0 | 1.5 | 8.0 |
| 10.0 | 2.0 | 14.0 |
| 15.0 | 2.5 | 20.0 |
| 20.0 | 2.5 | 25.0 |
| 25.0 | 3.0 | 31.0 |
| 30.0 | 3.0 | 36.0 |
| 40.0 | 3.5 | 47.0 |
| 50.0 | 4.0 | 58.0 |
| 75.0 | 5.0 | 85.0 |
| 100.0 | 5.0 | 110.0 |
| 150.0 | 6.0 | 162.0 |
| 200.0 | 7.0 | 214.0 |
FKM Grade Selection — Matching Grade to Application
Standard brown FKM 75A covers the vast majority of applications, but four distinct FKM grades exist for specific requirements:
| FKM Grade | Fluorine Content | Temp Range | Key Advantage | Typical Specification |
|---|---|---|---|---|
| FKM Type 1 (Standard) | 66% F | -20°C to +200°C | Best all-round; lowest cost | Brown 75A — this product |
| FKM Type 2 (High-Temp) | 68% F | -20°C to +230°C | Extended upper temp limit | Refinery, aerospace |
| FKM GF (Low-Temp) | 66–67% F + perfluoro | -40°C to +200°C | Low-temp flexibility | Outdoor, cold climate |
| FKM GFLT (Extreme Low-Temp) | 67% F | -50°C to +200°C | Cryogenic + chemical | LNG, extreme cold |
For standard industrial maintenance and repair assortments, FKM Type 1 (Standard) Brown 75A covers over 90% of applications and is the correct stock specification.
Application Markets
Automotive — Fuel & Engine Systems
FKM is the O-ring compound of choice throughout modern automotive fuel and engine systems — the only standard elastomer that simultaneously resists petroleum fuels, biodiesel blends (B20–B100), ethanol-blended fuels (E10–E85), and sustained under-hood temperatures above +150°C.
- Fuel injector O-rings and fuel rail seals
- Fuel pump body seals
- Throttle body and intake manifold seals
- Turbocharger oil feed and return line connections
- Transmission fluid cooler line connections
- EGR (Exhaust Gas Recirculation) valve seals (+200°C+)
- Power steering pump seals (synthetic fluid service)
Chemical Process Industry
Chemical plant piping systems, reactor vessels, pump seals, and valve body O-rings in contact with aromatic solvents, chlorinated solvents, concentrated acids, and process chemicals that attack all other standard rubber compounds. FKM’s resistance to toluene, benzene, trichloroethylene, concentrated sulfuric acid, and chlorinated process streams makes it the specification compound for chemical plant maintenance kits.
Oil & Gas — Upstream, Midstream, Downstream
FKM O-rings are specified throughout oil and gas production and processing equipment — from wellhead Christmas tree valve seals and downhole tool O-rings in contact with crude oil, H₂S (sour gas), and hot produced water, to refinery heat exchanger cover seals, process valve body O-rings, and instrumentation port seals in contact with hot process hydrocarbons.
Aerospace & Defense
FKM is the standard O-ring compound for aerospace hydraulic systems using phosphate ester fluid (Skydrol, Hyjet), jet fuel, and aviation gasoline — fluids that rapidly destroy NBR. The combination of synthetic hydraulic fluid resistance, fuel resistance, and temperature capability makes FKM the mandatory specification for commercial and military aircraft hydraulic and fuel system O-rings. AS9100-certified FKM O-rings with full material traceability documentation available.
Industrial Hydraulics — Synthetic & Fire-Resistant Fluids
Hydraulic systems using fire-resistant fluids (phosphate ester HFD-R, water glycol HFC, polyol ester HFD-U) that are incompatible with NBR require FKM O-rings throughout the system — cylinder seals, valve body O-rings, pump cover seals, and accumulator port seals.
High-Temperature Process Equipment
Industrial ovens, heat treatment equipment, drying systems, and process vessels operating above +150°C — where EPDM and NBR reach their temperature limits — require FKM O-rings for sustained reliable static sealing. FKM maintains adequate elasticity and compression set resistance to +200°C continuous, making it the standard specification for high-temperature industrial process equipment O-ring maintenance kits.
Semiconductor & Electronics Manufacturing
Ultra-high vacuum systems, plasma etch chambers, CVD reactors, and semiconductor process equipment require O-ring compounds with very low gas permeability, high temperature resistance, and chemical resistance to aggressive process gases (HF, Cl₂, F₂, NF₃). FKM provides acceptable performance in many semiconductor process applications; FFKM (perfluoroelastomer) is specified for the most aggressive plasma and corrosive chemical environments.
FKM vs. Other Compounds — Application Decision Matrix
| Criterion | FKM (Brown) | NBR (Black) | EPDM (Black) | VMQ (Red) | FFKM |
|---|---|---|---|---|---|
| Petroleum oil | ✅ Excellent | ✅ Excellent | ❌ Poor | ❌ Poor | ✅ Excellent |
| Synthetic hydraulic fluid | ✅ Excellent | ⚠️ Varies | ❌ | ❌ | ✅ |
| Aromatic solvents | ✅ Excellent | ❌ Poor | ❌ | ❌ | ✅ |
| Chlorinated solvents | ✅ Excellent | ❌ | ❌ | ❌ | ✅ |
| Water / HVAC | ⚠️ Limited | ⚠️ Good | ✅ Excellent | ✅ Good | ✅ |
| Steam (>120°C) | ❌ | ❌ | ✅ | ✅ | ✅ |
| Max temp | +200°C | +100°C | +150°C | +250°C | +320°C |
| Min temp | -20°C | -40°C | -50°C | -60°C | -20°C |
| Chemical resistance | Broadest standard | Moderate | Good | Good | Universal |
| FDA available | ✅ Yes | ❌ | ✅ | ✅ | ✅ |
| Relative cost | Medium-High | Low | Low | Medium | Very High |
Decision rule: Specify FKM Brown 75A when:
- (1) operating temperature exceeds +100°C with oil/fuel contact,
- (2) media includes aromatic or chlorinated solvents,
- (3) synthetic hydraulic fluids (phosphate ester) are present, or
- (4) combined chemical and high-temperature resistance is required beyond NBR’s capability.
Groove Design Reference for FKM 75A O-Rings
FKM at Shore A 75 is harder than standard NBR 70A — groove dimensions follow the same AS568A / ISO 3601 groove standards but the higher durometer reduces compression set risk at elevated temperatures:
| Application | Recommended Squeeze | Surface Finish (Ra) | Notes |
|---|---|---|---|
| Static face seal | 20–28% | ≤ 3.2 μm | Standard industrial |
| Static radial | 18–25% | ≤ 3.2 μm | Standard industrial |
| Dynamic reciprocating | 12–18% | 0.2–0.4 μm | Lubricate with FKM-compatible grease |
| Dynamic rotary | 10–15% | 0.2–0.4 μm | Limit surface speed ≤ 0.5 m/s |
| High pressure static (>100 bar) | 20–25% | ≤ 1.6 μm | Add PTFE back-up ring |
Installation Best Practices — FKM-Specific
- Use FKM-compatible lubricant — petroleum jelly (Vaseline), mineral grease, or silicone grease are acceptable for FKM installation. Do NOT use ketone-based or ester-based lubricants — these swell FKM
- Pre-heat in cold environments — below -10°C, FKM becomes stiff; warm O-rings to +20°C before installation to restore flexibility and prevent installation tearing
- Protect from sharp edges — use installation sleeves and chamfered bore lead-ins; FKM at 75A is harder and less forgiving of sharp edges than softer compounds
- Cross-bolt torque sequence — when replacing FKM O-rings in flanged cover applications, always tighten in cross-pattern sequence to ensure even face compression
- Allow thermal stabilization — in high-temperature applications, bring system to operating temperature before final torque check; FKM relaxes slightly at first heat exposure
- Never mix with incompatible fluids — confirm system is completely purged of ketones, esters, or amines before installing FKM O-rings; even traces of incompatible fluid cause rapid compound swelling
Storage & Shelf Life
| Parameter | FKM O-Ring Guidance |
|---|---|
| Shelf life | 10+ years from manufacture (ISO 2230) |
| Storage temperature | +15°C to +25°C |
| UV / ozone | FKM is inherently ozone-resistant; standard precautions apply |
| Packaging | Original sealed packaging; avoid contact with NBR and NR compounds |
| Long-term stability | Outstanding — FKM has among the best long-term aging characteristics of any standard elastomer |
FKM’s long shelf life makes it ideal for maintenance stock — standard brown FKM 75A O-ring kits held as workshop maintenance inventory retain full sealing performance for the life of the kit.
Quality & Compliance
| Standard | Status |
|---|---|
| AS568A dimensional | ✅ Full range, all dash numbers |
| ISO 3601 dimensional | ✅ Full metric range |
| Hardness ISO 48-4 | ✅ Shore A 75 ± 5 |
| Compression Set ISO 815 | ✅ ≤ 20% (22h @ 200°C) |
| Oil resistance ISO 1817 | ✅ ≤ +5% volume change (IRM 903) |
| Heat aging ISO 188 | ✅ ≤ ±15% (70h @ 200°C) |
| FDA 21 CFR 177.2600 | ✅ FDA-grade FKM available (brown) |
| RoHS 2011/65/EU | ✅ Compliant |
| REACH 1907/2006 | ✅ Compliant |
| AS9100 Rev D | ✅ Available for aerospace supply |
| EN 10204 Type 3.1 | ✅ Full material certificate on request |
| PPAP Level 3 | ✅ Automotive OEM on request |
FAQ
What is a brown FKM O-ring assortment used for?
A brown FKM O-ring assortment is used when multiple O-ring sizes are needed for industrial sealing, repair, maintenance or assembly. The O-rings are installed in grooves and compressed between compatible mating surfaces to help reduce leakage of liquids or gases.
Why are FKM O-rings often brown?
Brown is commonly used as an identification color for FKM O-rings in many industrial sealing programs. It helps warehouse staff, assemblers and maintenance teams distinguish FKM seals from black NBR or EPDM O-rings, reducing the risk of material mix-up.
How should buyers select the correct FKM O-ring size?
The two key dimensions are inner diameter and cross-section. For critical sealing applications, buyers should also confirm groove width, groove depth, squeeze rate, pressure, temperature and movement type. A drawing or standard size reference helps avoid incorrect fit.
Is FKM suitable for all chemical media?
No. FKM offers strong resistance to many oils, fuels and chemicals, but it is not compatible with every chemical environment. Buyers should provide the exact contact media, concentration, temperature and exposure time so the compound can be reviewed before production.
Can the assortment packaging be customized?
Yes. Brown FKM O-rings can be supplied in bulk bags, size-labeled bags, compartment boxes, repair kits or OEM private-label packaging. The packaging method should match the buyer’s warehouse control, assembly process and distributor sales requirements.
Are samples available before bulk assortment production?
Samples are available upon request. Sample planning depends on the O-ring sizes, FKM compound, hardness, tolerance, tooling status, packaging method and quantity. Please provide a size list, drawing or physical sample so the assortment can be reviewed accurately.
Request a Custom Quote
Send your brown FKM O-ring assortment size list, drawing, standard reference or physical sample for technical review. Please include ID, cross-section, quantity per size, hardness, contact media, temperature range, pressure, sealing condition, packaging method and documentation requirements so we can prepare a practical quotation.
