Seals Taxonomy — Family Index
Reference catalog of every commonly specified seal family — static gaskets, O-rings, translating rod/piston seals, rotating lip and face seals, non-contact labyrinths, magnetic-fluid feedthroughs — with materials decisions, gland geometry, API 682 piping plans, and failure modes. SI units primary.
1. At a glance
Functional categories
- Static — no relative motion across the seal interface. Gaskets (soft-sheet, spiral-wound, kammprofile, RTJ), O-rings in static glands, metal C-rings, ConFlat (UHV).
- Dynamic, translational — reciprocating shaft / piston. Hydraulic rod seals, piston seals, wipers, buffer seals, pneumatic U-cups.
- Dynamic, rotational — rotating shaft. Radial lip seals (Simmerring), mechanical face seals, V-rings, spring-energized PTFE.
- Non-contact (clearance) — labyrinth, brush, bushing, throttle — controlled-leakage devices for steam turbines, jet engines, compressors.
- Magnetic — ferrofluidic feedthroughs (magnetic-fluid trapped by permanent magnet). Near-zero leakage but limited Δp.
Approximate leakage hierarchy (tightest → loosest)
- Welded / brazed joint — zero (no longer a “seal” but the reference floor)
- Metal-bonded gasket (ConFlat copper, knife-edge into Cu) — < 10⁻¹¹ mbar·L/s He
- Mechanical face seal (single, contacting wet) — < 0.5 mL/h typical API 682
- O-ring in proper gland (static) — < 10⁻⁸ mbar·L/s He achievable
- Lip seal (radial shaft) — film of oil weeps; “leak-free” is < 1 drop/h
- Labyrinth — designed-in leakage, kg/h to kg/s scale
- Bushing / clearance — highest controlled leakage, used where contact wear is unacceptable
2. Static gaskets
Soft-sheet gaskets
- Compressed aramid-fiber — e.g. Garlock Style 3000, Klinger Sil C-4400. NBR-bound aramid pulp on calender; replaces asbestos. T ≤ 200 °C, p ≤ 80 bar.
- Flexible graphite — e.g. Flexitallic Sigma 511, SGL Sigraflex. Pure exfoliated graphite, no binder; T to 450 °C oxidizing / 3000 °C inert. Use with tang or mesh insert.
- PTFE — Garlock GYLON 3504 (filled, restructured PTFE). Chemically inert; cold-flow controlled by silica/glass/barite filler.
- Expanded PTFE (ePTFE) — Garlock GYLON 3522, Gore GFO. Microfibrillated PTFE — compressible, conformable, FDA-compliant grades available.
- Rubber sheet — NBR, EPDM, FKM, neoprene. Low-pressure water / air / fuel; T limited by elastomer.
Spiral-wound
- Alternating V-shaped metal strip (usually 304/316/Inconel) and filler (graphite, PTFE, mica) wound under tension. Introduced by Flexitallic in 1912; modern construction with inner ring (anti-buckling) and outer ring (centering, compression stop) is the ASME B16.20 standard.
- Pressure class ASME 150–2500. Temperature −250 °C to 1000 °C (filler-dependent).
- Color code (B16.20): outer ring stripe = winding metal; inner-ring solid color = filler.
Camprofile (Kammprofile)
- Serrated solid metal core (concentric grooves ~0.5 mm pitch) faced with thin layer of soft material (graphite, PTFE, soft metal). Combines metal robustness with soft-facing sealability.
- High-recovery, reusable core, replaceable facings. Heat-exchanger gaskets, large-bore flanges.
RTJ — Ring-Type Joint
- Soft iron or low-alloy steel ring with oval (R) or octagonal (RX, BX) cross-section in machined groove on flange face. Seal by plastic deformation of ring into groove.
- API 6A / ASME B16.5 flanges for petroleum, high pressure / high temperature. RX is pressure-energized, BX is API 6BX for ≥ 5000 psi service.
Metal C-rings, spring-energized
- Bal Seal, Garlock Helicoflex — metal jacket (Inconel, SS) around helical coil spring; jacket plated (Ag, Au, Ni, In, PTFE) for conformability.
- Vacuum, cryogenic, ultra-high-temp, nuclear. Reusable in some grades.
Solid metal gaskets
- Soft Cu, Al, soft iron — annealed for compliance. Cu for UHV (ConFlat), Al for cryo/aerospace fittings.
Spring-loaded for nuclear / UHV
- Helicoflex (Garlock) C-ring with internal spring — primary nuclear closures, sodium-cooled reactors, fusion port flanges.
3. O-rings
Sizing standards
- AS568 (SAE) — US standard cross-section / ID dash numbers. 1xx = pipe / boss seal series (small ID), 2xx = standard (cross-section ~1/8 in), 3xx = large (cross-section ~3/16 in), 4xx = large bore (cross-section ~1/4 in), 5xx = boss/face seal special.
- ISO 3601-1 — metric equivalents; ID × cross-section in mm.
- JIS B 2401 — Japanese, P/G/S/V series for piston/gland/static/vacuum.
Variant cross-sections
- Square-section — rectangular cut; cheaper, less reliable sealing than round.
- X-ring / quad-ring — four-lobe cross-section; lower friction, less spiral-failure tendency in dynamic apps.
- Back-up rings — PTFE or hard polymer washer downstream of O-ring; prevents extrusion at high Δp.
- Encapsulated — FEP/PFA jacket over silicone or FKM core. Chemical resistance of fluoroplastic with elasticity of elastomer.
Common materials
| Elastomer | Trade names | T range (°C) | Best media | Avoid |
|---|---|---|---|---|
| NBR (Buna-N) | Buna-N, Perbunan | −30 to 100 | Mineral oil, fuel, water | Ozone, ketones, brake fluid DOT3/4 |
| HNBR | Therban, Zetpol | −30 to 150 | Hot oil, sour gas, R-134a, R-1234yf | Strong polar solvents |
| EPDM | Nordel, Vistalon | −50 to 150 | Water, steam, brake fluid DOT3/4/5.1, hot water | Mineral oils, fuel |
| FKM (Viton A/B/F) | Viton, Tecnoflon | −20 to 200 | Fuel, oil, acid, ozone | Steam, amines, ketones, DOT3/4 |
| FKM-GLT/GFLT | Viton GLT, GFLT | −40 to 200 | Same as FKM + low-T + R-1234yf | as FKM |
| FFKM | Kalrez, Chemraz, Perlast | −15 to 327 | Almost everything (semiconductor process gas, hot amines) | Cost — $$$$ |
| AFLAS (FEPM) | AFLAS, Viton ETP | −10 to 230 | Amines, H₂S, hot water + oil | Aromatic fuels |
| Silicone (VMQ) | Silastic | −60 to 230 | Dry heat, food/pharma (platinum-cure) | Steam, dynamic |
| FVMQ (fluorosilicone) | LS-2840 | −60 to 175 | Fuel + cold | Steam |
| PTFE | Teflon | −200 to 260 | Universal chemical | Static only (no elastic recovery) |
| CR (Neoprene) | Neoprene W | −40 to 110 | Refrigerants, mild oils, weather | Strong acids, aromatic fuel |
| Polyurethane (AU/EU) | Adiprene | −30 to 100 | Hydraulic — high abrasion resistance | Hot water, steam, amines |
4. Rod / piston seals (translational hydraulic)
Industrial hydraulic cylinder uses a stacked set in the rod gland:
- Wiper / scraper / excluder — outboard. Prevents ingress of dirt; lip points outward. NBR, polyurethane, or steel-cased polyurethane.
- Rod seal (primary) — main pressure seal. Polyurethane U-cup, PTFE-faced + elastomer-energizer (Trelleborg Stepseal, Turcon Glyd-Ring), or NBR/HNBR loaded U-cup (Polypak style, originated by Parker).
- Buffer seal — between rod seal and high-pressure side. Absorbs pressure spikes, drains trapped fluid. PTFE composite with O-ring energizer.
- Bearing band / wear ring — non-sealing; carries radial side-load off the rod seal. PTFE+bronze, PTFE+glass, or phenolic-cotton.
Piston gland mirrors this but reversed — bidirectional piston seal (Trelleborg Turcon Glyd-Ring T, Parker PolyPak double-acting) plus guide rings.
Manufacturer ecosystems: Trelleborg Sealing Solutions (Stepseal, Turcon, Zurcon), Freudenberg Sealing Technologies / SKF / CR, Parker Hannifin (Polypak, Polymyte), Hallite, Hunger.
Pressure capability: standard polyurethane U-cup ≤ 400 bar; with back-up ring ≤ 700 bar; PTFE composite up to 1000 bar.
5. Pneumatic seals
- Low pressure (≤ 10 bar typical), often oil-free service — different elastomers required (silicone or low-friction NBR).
- Symmetric U-cup (double-lip, bidirectional) — standard for pneumatic piston.
- Single-lip / X-ring — for low-friction rod seals.
- Wiper not always needed (cylinder typically sealed environment).
- Standard catalogs from SMC, Festo, Bosch Rexroth Pneumatik for ISO 15552 / VDMA-24562 cylinders.
6. Radial lip seals (Simmerring)
Invented by Walther Simmer at Freudenberg in 1929 — the standard rotating-shaft oil-retention seal.
Configurations
- Single-lip + garter spring — primary configuration. Elastomer lip pre-loaded against shaft by garter spring (typically stainless wire 0.3–0.5 mm). Designations: Freudenberg-Simrit BAUM / BAUMSL, SKF CRWH / HMSA10, Chicago Rawhide CR.
- Double-lip — primary sealing lip (oil-side) + secondary dust lip (air-side). For dirty environments.
- Labyrinth-pre-seal — labyrinth on air-side ahead of the lip — high-dirt service (off-road, agriculture).
- Hydrodynamic-aided — molded ribs or sine-wave pattern on lip pump fluid back toward sump. Unidirectional or bidirectional; allows higher shaft speeds and lower oil temperature.
Materials
- NBR (BA, B, BS profiles) — water-glycol, mineral oil, ≤ 100 °C continuous.
- FKM — hot engine oil, ≤ 180 °C continuous; ATF Dexron VI requires specific FKM compounds (peroxide-cured) — see failure modes.
- PTFE-stack — PTFE lip with garter spring + carbon back-up; for high shaft speeds (> 25 m/s), dry running, aggressive chemicals. Trelleborg Turcon Variseal, Bal Seal.
- Silicone — extreme cold-start (e.g. −60 °C aerospace).
Standards
- SAE J946 (radial lip seals) — dimensions, performance categories.
- ISO 6194 — equivalent international standard.
- DIN 3760 — German metric series.
7. Mechanical face seals
The standard rotating shaft seal for pumps, compressors, agitators in industrial / refinery service. A stationary face and rotating face held in axial contact by a spring and process-fluid pressure; sealing occurs across the flat face interface (≈ 1 µm film).
Spring configurations
- Single coil spring — simplest, cheap. Cannot be reversed for shaft direction.
- Multi-spring — ring of small springs around shaft, bidirectional. Standard for refinery service.
- Metal bellows — Inconel or AM350 welded-diaphragm bellows replace springs + dynamic O-ring. No dynamic elastomer → high temperature (≥ 400 °C, hot oil, steam) and clean-service (semiconductor) suitability. Flowserve Durametallic SBI, John Crane Type 28.
Face material pairs (rotating × stationary)
- Carbon-graphite vs SiC — workhorse for water, light hydrocarbons. Carbon is the wear-and-lubricate face; SiC provides hard counter-face.
- SiC vs SiC — severe service: abrasive slurries, dry-running risk, hot hydrocarbons. Self-lubricating reaction-bonded or sintered SiC grades.
- Tungsten-carbide vs WC or vs carbon — sour-gas, sulphuric acid; less thermal-shock tolerant than SiC.
- Carbon vs Ni-resist / Stellite — older / lower spec.
API 682 — refinery mechanical-seal standard
Categories 1/2/3 (severity), Types A/B/C (configuration), Arrangements 1/2/3 (single, dual unpressurized, dual pressurized).
Piping plans (selected):
- Plan 11 — flush from pump discharge through orifice into seal chamber (most common).
- Plan 13 — recirculation from seal chamber back to pump suction (vertical pumps, vapor handling).
- Plan 14 — combined 11+13 (in+out flush).
- Plan 21 — flush from discharge through cooler then orifice into chamber (hot fluids).
- Plan 23 — closed-loop flush via pumping ring through cooler back to chamber (hot service, lower utility cost than 21).
- Plan 52 — unpressurized buffer fluid between dual seals, vented to flare (Arrangement 2). Detects leak via reservoir level.
- Plan 53A/B/C — pressurized barrier fluid between dual seals (Arrangement 3). 53A = reservoir + N₂ pressure; 53B = bladder accumulator; 53C = piston accumulator self-pressurized from process. Zero process leakage to atmosphere.
- Plan 74 — buffer gas (typically N₂) for dry-running dual gas seal (Arrangement 3 dry).
Cartridge vs component
- Component — gland, faces, springs, O-rings shipped separately; assembled into pump stuffing-box. Skilled installation required.
- Cartridge — pre-assembled in sleeve + gland, set screws to shaft, clips to control axial position during install. Plug-and-play; preferred for refinery service per API 682.
Major OEMs: John Crane (Type 1/8/28/48/5610), AESSEAL (CDPH, CMTU), Flowserve / Durametallic / BW (ISC, BX, GX), EagleBurgmann (M7N, MFL).
8. Magnetic-fluid / ferrofluidic seals
Pioneered and commercialized by Ferrotec. Configuration:
- Permanent-magnet ring on shaft (or stator) creates radial field in narrow annular gap.
- Ferrofluid (magnetite particles colloidally dispersed in carrier oil) drawn into gap, held there by field gradient — forms multiple O-ring-like liquid “stages” in series.
- Each stage holds ~0.2 bar; stacked stages hold ~1–3 bar total typical.
Applications: semiconductor wafer-handler rotary vacuum feedthrough (cleanroom, must not particulate), CVD reactor shafts, X-ray tube anode, optical scanners. Near-zero leak rate (< 10⁻¹⁰ mbar·L/s He). Limited Δp and limited surface speed; ferrofluid evaporation in deep UHV is the lifetime limit.
9. Labyrinth and clearance seals (non-contact)
Designed-in clearance; some leakage by design. Standard in turbomachinery where contact would destroy efficiency or wear-life.
Labyrinth geometries
- Straight (see-through) — series of fins on rotor (or stator) projecting into chamber; each fin throttles flow. Simplest; rotor expansion can rub.
- Stepped — alternating-diameter cavities; better flow disruption per unit length.
- Staggered (interlocking) — fins on both rotor and stator interlace; highest sealing efficiency but axial position critical.
- Honeycomb stator — over-rotor labyrinth runs into honeycomb; rub-tolerant. Common in gas-turbine compressor inter-stage.
- Advanced spiral / brush-replacement — newer ridged geometries inspired by NASA / DOE turbine programs.
Bushing seals
- Carbon ring (segmented, 3–4 arc segments) loosely surrounding shaft, held by garter spring or external clamp. Used in steam-turbine shaft glands, large compressors. Allows controlled radial growth.
Brush seals
- Bristle pack (cobalt-base superalloy wire, 50–100 µm dia, 10⁵ bristles/cm circumferential) angled against rotor. Replaces or augments labyrinth in modern jet engines (GE GE90, PW1100G) for tight clearance with rub-tolerance. Stiffness varies with shaft excursion.
10. Lip seal exotica
- V-ring — axial elastomer seal that mounts on shaft and rotates with it; flexible lip rubs against a counterface (often a flat steel washer or housing face). Used as standalone (low-speed) or as a labyrinth pre-seal in front of a primary radial-lip seal. SKF V-Ring (VA, VL, VS, VE), Trelleborg Forsheda V-Ring.
- Spring-energized PTFE radial seal — PTFE jacket (filled — glass, MoS₂, bronze, carbon, polymer) with internal cantilever or coil spring. Brands: Bal Seal, Kalsi seal (rotary, oil-side bias), Trelleborg Variseal, Greene Tweed. Service: high speed, dry running, cryogenic, vacuum, aggressive chemicals.
- Excluder / scraper rings — metal-cased polyurethane or NBR; mechanical lip designed purely to remove ice/mud/abrasive from rod before primary seal.
11. Static vacuum / cryogenic seals
- Copper gasket (ConFlat / CF flange) — annealed OFHC copper gasket pressed between two stainless-steel knife-edge flanges; achievable leak rate < 10⁻¹¹ mbar·L/s He. UHV standard (DN 16 CF to DN 250 CF and beyond). Bakeable to 450 °C. Single-use gasket.
- Viton/FKM O-ring in groove (KF/QF, ISO-K) — high-vacuum (HV) to 10⁻⁸ mbar; reusable, no bake. KF (NW) quick-clamp series for routine HV.
- Wire seal — Au, In — soft metal wire ring crushed between flanges; cryogenic (LHe, LN₂) and UHV bake applications.
- Metal C-rings (Helicoflex, Garlock) — re-pressurizable, accommodate larger surface imperfection than CF Cu.
12. Materials decision matrix — media vs elastomer
| Media | First choice | Alternates | Avoid |
|---|---|---|---|
| Water, cold/hot ≤ 100 °C | NBR | EPDM, FKM | — |
| Steam (≤ 200 °C, saturated) | EPDM (peroxide-cured) | FFKM | NBR, FKM |
| Mineral oil, hot (engine, hydraulic) | FKM | HNBR, NBR | EPDM, silicone |
| Diesel / gasoline | NBR | FKM, HNBR | EPDM, silicone |
| E10 / E85 ethanol-gasoline | FKM-GFLT, HNBR | FFKM | NBR, EPDM |
| Brake fluid DOT 3 / 4 / 5.1 (glycol-ether) | EPDM | — | NBR, FKM |
| Brake fluid DOT 5 (silicone) | EPDM, NBR | — | — |
| Refrigerant R-134a + PAG/POE oil | HNBR | FKM-GFLT | EPDM, NBR |
| Refrigerant R-1234yf + PAG/POE oil | HNBR (specific compounds), FKM-GFLT | FFKM | NBR, EPDM |
| Refrigerant R-744 (CO₂) | EPDM (high-T compounds), HNBR | FFKM | — |
| Sour gas (H₂S service) | AFLAS / FEPM, HNBR (low H₂S), FFKM (severe) | — | NBR, low-grade FKM |
| Aromatic / chlorinated solvents | FFKM (Kalrez 4079), PTFE | FKM-F | NBR, EPDM, silicone |
| Strong acid (H₂SO₄, HCl) | FFKM, FEP-encapsulated FKM | — | NBR, EPDM |
| Strong base (NaOH, KOH) | EPDM, FFKM | — | FKM (especially A grades — attacked by amines) |
| Amines (gas-treating MDEA/DEA) | AFLAS, FFKM | EPDM | FKM-A |
| Hydraulic fluid HFA/HFB (water-glycol) | NBR, HNBR | — | Polyurethane (hydrolysis) |
| Hydraulic fluid HFC (water-glycol) | NBR, HNBR, EPDM | — | Polyurethane |
| Hydraulic fluid HFD-R (phosphate ester) | EPDM, FKM-F, FFKM | — | NBR, standard FKM |
| Food / pharma | EPDM (peroxide, FDA), platinum-cured silicone, FFKM (USP Class VI) | — | NBR (USDA H1 grades only) |
| Hydrogen gas | EPDM (low permeability), HNBR | — | Silicone (high permeability) |
Temperature × chemical compatibility is a two-axis problem — both must be satisfied. Manufacturer compatibility databases (Parker, Trelleborg, Freudenberg, DuPont/Chemours Kalrez) are authoritative; their numbers come from real soak tests not theory.
13. Geometry and gland design
O-ring static gland (radial squeeze)
- Radial squeeze typically 15–25 % of cross-section diameter for static face/radial; 10–15 % for dynamic to limit friction and wear.
- Groove fill: 70–85 % — leaves room for elastomer thermal expansion and (with media) swell.
- Stretch (for ID-sealing static): 1–5 %. > 5 % accelerates ozone/heat aging.
- Surface finish: 0.4–0.8 µm Ra (16–32 µin Ra) for static; 0.2–0.4 µm Ra (8–16 µin Ra) for dynamic; lay perpendicular to motion direction for dynamic.
- Hardness: 70–80 Shore A typical static; 80–90 Shore A dynamic (extrusion resistance); 90 + back-up ring for high-pressure dynamic.
Standards / handbooks
- Parker O-Ring Handbook ORD 5700 — definitive gland design reference (latest revision).
- SAE AS5857 — military / aerospace gland design.
- ISO 3601-2 — housing dimensions (mating gland).
- MIL-STD-413, MIL-G-5514 — legacy aerospace gland standards.
Rod / piston gland
- Hardened rod surface (HRC ≥ 55, Cr-plated or HVOF tungsten-carbide for severe). Surface finish 0.1–0.4 µm Ra for primary rod seal; finer = lower wear, but too fine starves lubrication.
- Piston bore honed cross-hatch 0.4–0.8 µm Ra to retain oil film.
14. Selection heuristics
- Hydraulic cylinder rod (industrial, 250 bar) → polyurethane U-cup primary + buffer seal + wiper, plus PTFE+bronze wear rings.
- Hydraulic cylinder rod (mobile, high shock, dirty) → step-seal (PTFE on O-ring) primary + heavy-duty metal-cased wiper + secondary lip.
- Pneumatic piston (oil-free) → NBR symmetric U-cup, low-friction silicone option for ISO 15552 cylinders.
- High-pressure flange (ASME 600+, hydrocarbon) → spiral-wound 316/graphite with inner + outer ring per B16.20, or RTJ for ≥ 1500 lb class.
- Water-pump shaft (auto, OEM) → unitized face seal (carbon vs SiC) or radial-lip NBR for low-cost.
- Refinery centrifugal pump shaft → API 682 cartridge mechanical seal, SiC vs carbon, Plan 11 (or 23 for hot service).
- Cryogenic pump shaft → metal-bellows mech seal or Bal Seal spring-energized PTFE.
- Steam-turbine HP-stage shaft glands → labyrinth + carbon bushing + steam-injection / extraction.
- Jet engine compressor / turbine inter-stage → labyrinth (honeycomb stator) or brush seal.
- Semiconductor process gas valve / chamber → Kalrez (FFKM) 4079 / 6375 / 7075 grade-matched to media.
- Cryogenic / UHV rotary feedthrough → magnetic-fluid (Ferrotec) or spring-energized PTFE.
- UHV static flange (bakeable) → ConFlat copper gasket.
- HV (10⁻⁶ mbar) static flange (reusable, no bake) → Viton in KF or ISO-K groove.
- Food / pharma agitator → platinum-cured silicone or EPDM USP Class VI O-rings; FDA-compliant mechanical seal with FFKM secondaries.
- Sour gas wellhead (high H₂S) → AFLAS / HNBR / FFKM elastomers; metal-to-metal primary, elastomer secondary; NACE MR0175-compliant metal grades.
- Automotive A/C R-1234yf → HNBR (qualified compound) or FKM-GFLT specifically rated by OEM; older NBR / standard-FKM fails on dye-test.
15. Failure modes
- Extrusion — high Δp pushes elastomer into clearance gap of low-pressure side; chunks of ring shave off. Cure: harder duro (80–90 A), tighter clearance, add back-up ring on low-Δp side (or both sides for alternating pressure).
- Explosive decompression (ED / RGD) — high-pressure gas dissolves into elastomer; rapid system depressurization → gas tries to escape faster than it can diffuse → forms blisters or splits the ring. Common in sour gas, CO₂, H₂. Cure: high-modulus / high-crosslink compounds — HNBR, EPDM, AFLAS, FFKM with anti-ED rating (NORSOK M-710, ISO 23936-2 tested).
- Thermal degradation — elastomer chain scission or further crosslink at elevated T. Symptom: brittle, cracked, glossy ring. Cure: move up the temperature ladder (NBR → HNBR → FKM → FFKM).
- Chemical swell — elastomer absorbs media, volume increases > 15–20 %, ring extrudes / loses sealing force. Cure: re-select compound; check published swell data in target media.
- Chemical attack (no swell, but degradation) — main-chain cleavage. E.g. FKM in amines, EPDM in mineral oil, NBR in ozone. Cure: re-select.
- Abrasion (dynamic) — particles in fluid grind the lip / rod-seal contact. Cure: install wiper, polyurethane primary, finer-finished mating surface; filter upstream.
- Spiral failure — long static O-ring in a dynamic gland twists during stroke; surface tears form helically. Often combined with starvation. Cure: X-ring (quad), proper lube during install, square-cross-section seal, or PTFE composite.
- Compression set — permanent deformation; ring fails to recover when bolt-load reduced (thermal cycle, vibration). Cure: peroxide-cured EPDM/FKM (lower set than sulfur-cured), lower service T, or live-loaded bolting.
- Ozone cracking — outdoor surfaces of NR, SBR, sometimes NBR; surface crazing perpendicular to stress. Cure: anti-ozonant compound; or use EPDM/CR/FKM/silicone (all ozone-resistant).
- ATF compatibility (FKM) — modern Dexron VI, Mercon LV use additive packages that attack non-peroxide-cured FKM-A. OEMs specify peroxide-cured FKM-B/F or FKM-GF for transmission shaft seals; misapplication causes early lip-seal weep.
- Bolt relaxation (gasket joints) — flange bolts lose preload over time at temperature; gasket stress drops below seating-stress floor; leak. Cure: live-loading (Belleville stacks), torque-retighten cycles per ASME PCC-1, or move to high-recovery gasket (kammprofile, spiral-wound).
16. Cross-references
- polymers-taxonomy — elastomer chemistry, families, supplier brands
- bearings-taxonomy — shaft systems that seals run with
- springs-taxonomy — garter springs, mech-seal compression springs
- fasteners-taxonomy — flange bolting, torque, live-loading
- pumps-turbomachinery — pump shaft sealing system context (API 682)
- refrigeration-cycles — refrigerant/elastomer compatibility context
17. Citations and references
- Parker Hannifin — Parker O-Ring Handbook ORD 5700 (latest revision). Definitive O-ring gland design and material compatibility.
- Trelleborg Sealing Solutions — Rod and Piston Sealing Catalog; O-Ring Catalog. Stepseal, Turcon, Variseal data.
- Freudenberg-Simrit — Simmerring & Rotary Seals Technical Manual. Radial lip seal design and material guide.
- SKF — Industrial Shaft Seals Catalog 4001/I E. Lip seal CRWH/HMSA10 lines.
- John Crane — Engineered Seal Solutions technical manuals; Type 28 Bellows Seal series datasheets.
- AESSEAL — API 682 Compliant Seal Solutions technical guide.
- Flowserve — Mechanical Seals Reference Manual; API Plans Pocket Guide.
- DuPont / Chemours — Kalrez Chemical Resistance Guide; Viton Selection Guide.
- ASME B16.20 — Metallic Gaskets for Pipe Flanges: Ring-Joint, Spiral-Wound, and Jacketed.
- ASME B16.21 — Nonmetallic Flat Gaskets for Pipe Flanges.
- ASME PCC-1 — Guidelines for Pressure Boundary Bolted Flange Joint Assembly.
- API 682 — Pumps — Shaft Sealing Systems for Centrifugal and Rotary Pumps. 5th edition (latest); also ISO 21049.
- API 6A / ASME B16.5 — flange and RTJ ring dimensions.
- ISO 3601-1/2/3 — Fluid power systems — O-rings. Inside dimensions, housing dimensions, quality acceptance.
- ISO 23936-2 / NORSOK M-710 — Explosive-decompression qualification of elastomers for oil and gas.
- NACE MR0175 / ISO 15156 — Materials for use in H₂S-containing environments in oil and gas production.
- SAE J946 — Radial lip seal dimensions and performance.
- SAE AS568 — O-ring sizes.
- SAE AS5857 — Aerospace O-ring gland design.
- Flitney, R. — Seals and Sealing Handbook, 6th ed., Butterworth-Heinemann, 2014. The general reference text.
- Müller, H. K. & Nau, B. S. — Fluid Sealing Technology: Principles and Applications, CRC Press, 1998.
- Ferrotec — Magnetic Liquid (Ferrofluid) Seals Technical Brochure.