Gylon FDA USP Class VI Clamp Gasket
On a tri-clamp connection, sealing is not provided by the clamp but by the gasket. The clamp sets the compression; the gasket turns it into a seal and absorbs the forces from the line. The choice of its material determines the allowable temperature, chemical compatibility and service life of the connection.
Gylon BIO-PRO is a modified PTFE, more flexible than solid PTFE, that seals under low tightening force. Range from -210 °C to +260 °C with no creep or cold flow. Its blue colour makes it identifiable on the line.
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Tubes Technologies gasket selection guide
Rubberfab references, Gylon gasket
Guidelines for sanitary gasket materials
Gylon style 3504, -210 °C to +260 °C, low tightening force
Gylon BIO-PRO clamp gasket, in blue modified PTFE, style 3504. Service range from -210 °C to +260 °C with no extrusion or cold flow. More flexible than solid PTFE, it seals under low tightening force, which limits mechanical wear and suits torque-limited clamps. Asbestos-free, long service life. Gylon is a registered trademark of Garlock.
Where this material is the right choice, and where it is not
Gylon solves the main drawback of solid PTFE: its rigidity. It is more flexible and seals under low tightening force, which limits mechanical wear on the connection and makes it compatible with torque-limited clamps. Its creep behaviour is far superior to that of solid PTFE, resulting in longer service life and reduced maintenance. It withstands -210 °C to +260 °C without extrusion or cold flow, and resists most chemicals and thermal cycling. Asbestos-free. Its blue colour allows visual identification on an installation.
The Gylon BIO-PRO tri-clamp gasket is a flat gasket without lip; it does not benefit from the centring of a Type II. It may require care during installation. It is a speciality product, more expensive than a standard elastomer, whose value is justified at points with low available torque, thermal cycling or long service-life requirements. On a standard fitting without these constraints, a standard gasket is sufficient.
A flat gasket, without lip
The Gylon BIO-PRO tri-clamp gasket is a flat gasket without centring lip. It is centred by hand in the groove of the two ferrules, like a Type I. Unlike elastomers, it is not available here in a lipped version: the modified material is supplied in sheet form and cut flat.
Manual centring therefore requires particular care during installation, which is the downside of its flexibility and low tightening force. For a point requiring automatic centring, use a material available in Type II or Pure Seal, custom-machined with a lip.
Material properties
| Characteristic | Value |
| Material | Gylon style 3504 |
| Service temperature | -210 °C to +260 °C (-346 °F to 500 °F) |
| Construction | Modified PTFE, Gylon style 3504, blue colour |
| Tightening force | Low, suitable for limited torque |
| Creep | No extrusion or cold flow across the range |
| Asbestos | Asbestos-free |
| Compliance | FDA, USP Class VI, depending on reference (see appendix) |
| Versions | Type I without lip only |
The temperature range and chemical compatibilities come from the supplier’s data. Detailed chemical information is provided in the materials guide and the compatibility sheet, available for download.
Dimensions
Standardised dimensions. The gasket outside diameter corresponds to the ferrule face, the inside diameter to the flow path. A gasket whose inside diameter protrudes into the flow path creates retention; a gasket that is too small opens a crevice.
| Size | Gasket ID (mm) | Gasket OD (mm) | Ferrule flange A (mm) | Tube DN |
| 1″ | 22,9 / 0.900″ | 50,4 / 1.984″ | 50,5 | DN25 |
| 1 1/2″ | 35,6 / 1.400″ | 50,4 / 1.984″ | 50,5 | DN40 |
| 2″ | 48,3 / 1.900″ | 63,9 / 2.515″ | 64 | DN50 |
| 2 1/2″ | 61,0 / 2.400″ | 77,5 / 3.050″ | 77,5 | DN65 |
| 3″ | 73,7 / 2.900″ | 90,9 / 3.579″ | 91 | DN65 |
| 4″ | 98,3 / 3.869″ | 118,9 / 4.682″ | 119 | DN100 |
Millimetre conversions are for guidance only. The complete clamp, ferrule and tube correspondence table is available for download.
The gasket: the sensitive link in the clamp fitting
The quality of a clamp connection depends on three elements: the gasket, the clamp and pipe alignment. The gasket provides the seal and at the same time absorbs the torsional forces transmitted by the line. This dual role is the weak point of the clamp fitting.
A misaligned section makes the gasket work constantly, causing wear and then premature tearing. Excessive tightening pushes the gasket into the flow path and creates a dead leg. The gasket is the consumable part of the connection: it is replaced, not salvaged.
This material compared with others
A gasket material is chosen based on temperature, fluid, dismantling frequency, regulatory requirements and cleaning method. Here is what sets the main materials apart.
| Material | What it offers | Its limitations |
| EPDM (and silicone) | Very flexible, easy to install, economical | Limited temperature, does not withstand oils or solvents |
| FKM Viton | Oils, solvents, acids, up to 204 °C | Strong oxidisers, less flexible, more expensive |
| Solid PTFE | Exceptional chemical and thermal resistance | Rigid, high tightening, creep |
| Gylon 3504 | Flexible, low tightening, creep-resistant, very wide range | Flat without lip, speciality, more expensive |
| Pure Seal | White Gylon equivalent, with or without lip | Less common, availability to be checked |
| Tuf-Flex | PTFE bonded to EPDM, crush-resistant, WFI | More expensive, strong oxidisers to be checked |
| Tuf-Steel | PTFE + 316L stainless steel, creep-resistant, -196 to +288 °C | Expensive, demanding applications |
Each material has a dedicated data sheet with its service ranges, compliance and chemical compatibilities.
Frequently asked questions
Gylon or solid PTFE?
Gylon when the available tightening torque is limited, when the line is subject to thermal cycling, or when service life is the priority. Solid PTFE remains cheaper for a point without these constraints. Gylon provides the flexibility and creep resistance that solid PTFE lacks.
How do I choose the size?
On the outside diameter of the ferrule, like the clamp. The gasket inside diameter must be flush with the flow path without protruding. The correspondence table gives the equivalence between size, ferrule and tube.
Which compliance applies for pharmaceuticals?
The compliance stated by the supplier must be checked reference by reference on the material certificate for the batch delivered. The exact certification must be included in the file.