In flanged piping systems, heat exchangers and process vessels across the chemical, pharmaceutical and oil and gas industries, the gasket is the last line of defence between the process fluid inside the pipe and the personnel and environment outside it. Select the wrong gasket material and you have a potential leak path in a system carrying corrosive acid, toxic solvent or flammable hydrocarbon. Select the right one and that connection will operate without leakage for years — or decades.
Fluoro Polymer Products, based in Anand, Gujarat, has been manufacturing precision PTFE gaskets — including PTFE ring gaskets, envelope gaskets, sheet gaskets and custom PTFE seals — for over 30 years, supplying chemical plants, pharmaceutical manufacturers, oil refineries and power facilities across India and internationally.
Principal gasket types in industrial use
| Gasket type | Materials used | Typical applications |
|---|---|---|
| Full-face gasket | Rubber, PTFE, soft metal | Low-pressure flanged connections, glass-lined flanges |
| Ring gasket (raised face) | Rubber, PTFE, spiral wound | Medium-to-high pressure process flanges |
| Envelope gasket | PTFE envelope over soft filler | Corrosive chemical service, glass-lined equipment |
| Spiral wound gasket | Metallic + PTFE or graphite filler | High pressure, high temperature, cyclic service |
| Ring joint (RTJ) | Soft iron, stainless steel, alloys | Very high pressure (API pipe flanges, wellheads) |
How the four major gasket materials compare
Rubber and elastomeric gaskets (EPDM, NBR, neoprene, Viton): good conformability and low cost for moderate applications. However, every rubber type has defined chemical resistance boundaries. NBR is degraded by ketones and many acids; EPDM fails with oils and organic solvents; even Viton fails with certain ketones and steam. All rubber gaskets are susceptible to compression set — permanent deformation under sustained load — leading to eventual bolt-load relaxation and leakage. Verdict: suitable only within specific, tested resistance limits. Not for aggressive chemical service.
Compressed non-asbestos fibre (CNAF) gaskets: good general-purpose performance at moderate cost. However, binders and fillers have finite chemical resistance — susceptible to strong acids, oxidising agents and certain solvents. CNAF gaskets can wick process fluids, creating contamination risk in pharmaceutical and food applications. Verdict: suitable for moderate-duty general applications. Not for high-purity or aggressive chemical service.
Metallic and semi-metallic gaskets (spiral wound, ring joint): excellent at high pressures and temperatures. However, they require high bolt loads and precisely machined flange surfaces — not appropriate for glass-lined, FRP or other non-metallic flanges. Verdict: essential at high pressure and temperature. Limited applicability where flange surface capacity is constrained.
PTFE gaskets: chemical resistance to virtually every known process chemical — including all mineral acids, alkalis, solvents and hydrofluoric acid. FDA and USP Class VI compliance. No biological reactivity. Stable from cryogenic to 260°C. Good conformability on glass-lined and FRP flanges. Verdict: the optimal choice for chemical, pharmaceutical, food and aggressive process applications.
Head-to-head: PTFE vs other gasket materials
| Factor | Rubber gasket | CNAF gasket | Spiral wound | PTFE gasket |
|---|---|---|---|---|
| Chemical resistance | Limited by rubber type | Limited by binders | Limited by metal grade | Near-universal |
| Temperature range | Up to ~200°C (Viton) | Up to ~450°C | Very high | −200°C to +260°C |
| Pharma / food compliance | Limited | Not generally | Not generally | FDA / USP Class VI |
| Glass-lined flanges | Possible | Not ideal | Not suitable | Standard spec |
| HF acid service | Not suitable | Not suitable | Not suitable | Only polymer option |
| Creep under load | Compression set risk | Moderate | Minimal (metallic) | Manageable with correct grade |
The PTFE envelope gasket — the engineering solution for chemical service flanges
A PTFE envelope gasket consists of a precisely machined PTFE outer envelope that fully encapsulates a soft filler material — typically compressed fibre or soft rubber. The result combines the flange conformability of a soft gasket with complete PTFE chemical resistance at all fluid contact surfaces. Even for chemicals that would rapidly degrade the filler material — if the envelope remains intact, the filler sees no chemical exposure. The PTFE envelope gasket is the near-universal specification for glass-lined reactor and aggressive chemical service flange connections.
Managing PTFE creep in gasket applications
PTFE’s tendency to creep (cold flow) under sustained bolt load is a well-understood and readily managed phenomenon:
- Specify envelope gaskets with rigid fillers or glass-filled PTFE sheet for higher bolt-load applications.
- Re-torque bolts after the first heating cycle at operating temperature.
- Ensure correct flange surface finish and bolt stress calculations per ASME guidelines.
- For high-load applications, glass-filled or graphite-filled PTFE provides substantially better creep resistance while retaining chemical resistance.
Fluoro Polymer Products PTFE gasket range
- PTFE ring gaskets — machined from virgin or filled PTFE to ASME B16.21 and custom dimensions.
- PTFE envelope gaskets — flat, tongue & groove, male & female and ring styles; glass-lined equipment dimensions available.
- PTFE sheet gaskets — cut from moulded or skived PTFE sheet in any thickness and custom dimensions.
- Custom PTFE seals — machined to customer drawings, any geometry and grade.
For a properties-and-installation deep dive, see our PTFE gaskets guide; to compare PTFE against other fluoropolymers before you specify, see PTFE vs PVDF vs PFA. Need PTFE gaskets for your process flanges? Share your media, temperature, pressure and flange type, and our team will recommend the correct PTFE gasket design and grade for your application.
Fluoro Polymer Products — Engineering Team
ISO 9001:2015 certified PTFE manufacturer in Anand, Gujarat with 30+ years of hands-on experience engineering fluoropolymer components for chemical, pharma, food and power industries since 1992.