PTFE envelope gaskets

The materials commonly used in the field of industrial sealing (as rubber or non-asbestos with aramid fibre and elastomeric filler), usually doesn’t fit all the required standards of strength, width, chemical and mechanical resistance that certain application could require.

FF.GI srl is a pioneer in the envelope gaskets industry and we have reached the highest quality standards, using innovative materials, advanced technologies and a qualified work force. Every type of gasket is studied and projected to fulfil the highest needs of a constantly evolving market.


Commonly named “envelope”, it has the purpose of protecting the internal part of the gasket from the substances which they are in contact with; these envelop are mostly made of:

- Virgin PTFE FLON-CHEM 1000;
- Modified PTFE FLON-CHEM 1075;
- Antistatic/Conductive PTFE FLON-CHEM 1022;
- Modified/Antistatic/Conductive PTFE FLON-CHEM 1023;

All the enlisted materials are complying with the US law: FDA, Food and Drug Administration, department of Health and Human Services, Code of Federal Regulations 21 CFR Ch.1; USA regulations sections 177.1550 (a) (1) and (b) Perfluorocarbon Resins;

There is different type of envelop due to the applications and the customers desires, in case of big diameters and small quantities the cost could be too high so we could weld the sealing in one point.

The welding process are done to the “head” without overlapping the two PTFE parts; the perfect execution of the welding is ensured by using the correct parameters of temperature, pressure and time in activity of the part to be welded. Destructive and non-destructive trials are done frequently to homologate the welding process.


These are the most common materials used for the envelope gaskets internal part in order to grant mechanical support:
GRA-FLEX 5400: Expanded graphite resistant to very high temperatures and large thermal shocks; the kind with internal armour in Aisi 316 is strongly resistant to mechanical stresses.

GRA-FLEX 5200: Expanded graphite reinforced with A1200 aluminium double foil that gives high mechanical resistance to the graphite, but at the same time makes it flexible and perfect to be the internal part of a PTFE envelope gasket.
FLON-CHEM-1011-PINK PTFE Modified PTFE silica charged, it maintains the thermic and chemical resistance of PTFE but gaining better elasticity necessary for the sealing process; this gasket is completely FDA and could be used up to 260°C.

BLUFLEX® 3000: Universal non asbestos joint with a base in aramid fibre and nitrile rubber filler.
Bio-soluble ecological ceramic fabric ECOSILC: Material realized with carded bio-ceramic wire, good stability to the temperature, excellent resistance to thermal shocks, good chemical resistance.
Thanks to softness and flexibility is indicated for glazed flange, glass flange, not smooth surfaces.


The corrugated wave ring grant to the envelope gasket the necessary elasticity for a perfect sealing, and at the same time a effective adaptability to eventual irregularities of the flange; is usually furnished in stainless steel AISI 316 (1.4401) or AISI 316 Ti (1.4571).


The gaskets with the undulate ring could be equipped with fixing clips or a special earthclip able to unload any electrostatic charge that could be generated by the machine, a real deal in some kind of industrial processes.


The single hole clip is the most common and it’s used to link the gasket to the grounding with cables, screws and fixing bolts. Particularly for the oval gaskets or big round gaskets, this clip could be used to fix the gasket to the flange where is installed.


The double hole clip is the evolution of the single one, concerning the envelope gaskets that have to be installed between the flanges; in fact with the two holes clip you can eliminate completely all the other solution to fix the gasket to the machine (cables, screws, bolts) making the gasket cheaper and easy to be removed; in addition to that the yellow and green covering allows the gasket to be seen easily inside the machine; these gaskets are available up to DN200 in one piece without welding.


All the envelope gaskets are available in the most common dimensional standards:
- DIN 28148 (both oval and circular);
- BN 83 (Basler Norm);
- DIN 2690 / EN 1514-1 / EN 1514-3 / UNI 2229;
- ANSI B 16.21 for flanges ANSI B 16.5;

- TA-LUFT VDI 2440 type BUR;
- FDA, Food and Drug Administration, 21 CFR Ch.1, 177.1550 (a) (1) and (b) Perfluorocarbon Resins;

In addition, we can produce the envelope gaskets tailored to the customer design up to 5000mm diameter.