The PTFE-enveloped gasket combines a PTFE envelope, in contact with the fluid, and an elastomer core that provides flexibility. The temperature range is that of the core: -34 °C to +149 °C in EPDM, up to +204 °C in FKM.

Rubber Fab materials and chemical compatibility guide

Tubes Technologies gasket selection guide

Gasket dimensions data sheet

Rubberfab reference, PTFE-coated FKM gasket

Rubberfab reference, PTFE-coated EPDM gasket

Guidelines for sanitary gasket materials

PTFE-coated clamp gasket, EPDM or FKM core, Type I and Type II

PTFE envelope on elastomer core, without lip and with lip

Sanitary tri-clamp gasket with PTFE envelope on an elastomer core, available without lip (Type I) and with centring lip (Type II). PTFE product face for chemical inertness, EPDM or FKM core for flexibility and elastic memory. Range depending on the core: -34 °C to +149 °C in EPDM, -34 °C to +204 °C in FKM. FDA and USP Class VI compliant. Diameters from 1/2″ to 12″.

Where this material is the right choice, and where it is not

The PTFE envelope provides the chemical inertness of PTFE on the product face, while the EPDM core provides the flexibility that makes sealing easier. It is a good compromise between the chemical performance of solid PTFE and the ease of installation of an elastomer, at a lower cost than a unitised gasket. The face exposed to the fluid is PTFE, so chemical inertness and low leaching are preserved.

Creep remains possible if overtightened, as the envelope is not bonded to the core as in a unitised gasket. The EPDM core limits the temperature to 149 °C; to go higher, it is replaced by an FKM core, which raises the limit to 204 °C. Unlike Tuf-Flex, the envelope and core do not form a single bonded part, which gives less consistent results over time under repeated SIP.

Type I and Type II: the lip changes installation

Type I, or Type B, is a flat gasket without lip. It is centred by hand in the groove of the two ferrules. This is the most common and least expensive version.

Type II, or Type A, has a centring lip that fits into the inside diameter of the ferrule. The gasket positions itself, cannot shift while the clamp is being closed, and alignment of its inner face with the flow path is guaranteed. On lines where a shifted flat gasket creates retention, or on hard-to-reach installations, the lip eliminates the risk of poor centring.

The choice between the two does not depend on the material, which is identical, but on the centring requirement at the installation point. Both versions cover the same temperature range and the same chemical compatibility.

Material properties

The temperature range and chemical compatibilities come from the manufacturer’s data. Detailed fluid-by-fluid chemical information is provided in the materials guide and the compatibility sheet, available for download.

Chemical resistance table

Dimensions

Standardised dimensions, common to all tri-clamp gasket materials. 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.

Millimetre conversions are for guidance only, based on the manufacturer’s dimensions in inches. 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 or stressed 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. Compression is achieved at the torque specified for the clamp, never by feel. 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.

Each material has a dedicated data sheet with its service ranges, compliance and detailed chemical compatibilities.

Frequently asked questions

Enveloped PTFE or Tuf-Flex?

Enveloped PTFE is a good economical compromise when SIP cycling remains moderate. Tuf-Flex, whose PTFE is bonded onto the core in a single unitised part, holds up better under intensive SIP because the envelope does not separate from the core. The first for a standard need, the second for a critical point.

Type I or Type II?

Type I, without lip, for standard installation. Type II, with centring lip, when the gasket must position itself and not shift, particularly where access is difficult or at points where shifting creates retention. Same material, same range; only the centring differs.

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?

FDA and USP Class VI compliance is stated by the manufacturer for sizes 1″ to 4″. Outside this range, it must be verified before being recorded in a file. The exact certification must appear on the material certificate for the batch delivered.

The basket clamp gasket, or sock screen, extends the sieving mesh into a sock shape inserted into the inside diameter of the tube. This extended shape offers up to 300 percent more filtering surface than a flat screen, and therefore a much greater retention capacity before clogging.

Rubber Fab materials and chemical compatibility guide

Gasket dimensions data sheet

Rubberfab screen gasket references

Sock screen inserted into the flow path, +300% filtering surface

Tri-clamp basket gasket, sock-shaped strainer inserted into the inside diameter of the tube. Up to 300 percent more open area than a flat screen, for 300 percent more collection capacity. Designed for large volumes of particles at low pressure drop. 316 stainless steel mesh. Fitted like a standard gasket. Ideal for tank transfers and truck unloading.

The filtering surface the flat screen lacks

A flat screen filters across the tube cross-section only. Its retention capacity is limited and it clogs quickly with a loaded fluid. The basket extends the mesh as a sock into the flow path, which more than triples the filtering surface and delays clogging accordingly.

The impact on operations is direct: more collection capacity, fewer cleaning interventions, fewer shutdowns and strainer changes. On a continuous pharmaceutical line, this means production time gained. The large open area also maintains a low pressure drop despite the flow rate.

The basket protects pumps and equipment from foreign bodies, reduces pump wear and seizing, and retains as much material as possible for quality control. It is particularly suited to transfers between tank and tanker truck, in both directions.

Characteristics

Dimensions and correspondence

The gasket is fitted like a standard gasket, on the outside diameter of the ferrule face. The clamp, ferrule and tube correspondence table, common to all versions, 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. A version with an added function, screen, orifice or measurement port, places more stress on the gasket than a solid gasket. A stressed installation or excessive tightening damages it more quickly. Compression is achieved at the torque specified for the clamp, never by feel.

Frequently asked questions

Basket or flat screen?

The basket for particle-laden fluids and high volumes, where its capacity prevents frequent clogging. The flat screen for a clean fluid where only safety screening is required, with minimal footprint.

Which way should it be inserted?

The sock extends into the inside diameter of the tube, on the upstream side, so that the fluid passes through the mesh from the inside outwards and the particles are retained in the basket. The installation direction follows the direction of flow.

Does it reduce pressure drop?

Compared with a flat screen of the same fineness, yes. The much larger open area passes the same flow rate with less restriction, which matters on high-flow transfer lines.

Gasket dimensions data sheet

Rubberfab screen gasket references

On a tri-clamp connection, the gasket does more than seal. The orifice plate adds a function: setting a flow rate, balancing a back pressure or calming a flow, directly at the connection plane, with no valve or tapping on the line.

Three models cover all needs: the solid undrilled plate, to be drilled according to the target flow rate; the pre-drilled flat plate with centred or eccentric bore; and the conical vertical plate for self-draining vertical lines. Electropolished 316L stainless steel body, EPDM, FKM, silicone or PTFE gasket.

Tri-clamp calibrated orifice plate gaskets, 3 models

Electropolished 316L stainless steel plate, solid, pre-drilled flat or conical vertical, 1/2″ to 6″

Tri-clamp calibrated orifice plate gasket, electropolished 316L stainless steel plate crimped onto a sanitary gasket. Three models depending on the need: solid plate to be drilled to order, pre-drilled flat plate with concentric or self-draining eccentric bore, conical vertical plate for vertical lines. Fitted between two ferrules like a standard gasket. Gasket in EPDM, FKM, silicone, PTFE or Steam-Flon. Sizes from 1/2″ to 6″, up to 4″ for the vertical plate. DIN 32676 series A, B and C standards.

Setting a flow rate without a valve or tapping

An orifice plate is a thin plate with a hole drilled in it, placed in the pipework. As the fluid passes through the orifice, its velocity increases and its pressure drops downstream, creating a fixed, known pressure drop. This restriction sets a flow rate, balances the branches of a network, limits backflow or breaks pressure during SIP phases, at the gasket plane of an existing fitting.

All without a control valve or additional section, and therefore without any added dead leg. The bore diameter is chosen according to the target pressure drop, by hydraulic calculation on a case-by-case basis.

Three models, three needs

The choice of model depends on the line configuration and how the hole is to be defined.

A flat plate placed horizontally in a vertical pipe is not self-draining; it retains liquid upstream. The downward-facing conical plate solves this problem, which is the point of the vertical model.

Bonded gasket or removable gasket

Standard plates with an elastomer gasket are normally bonded to the plate. If the gasket fails, the complete unit is replaced. The removable gasket is offered as an alternative: it makes it easier to machine the holes and prevents contamination of the gasket during drilling.

PTFE is moulded onto the plate. Steam-Flon is available moulded or removable. The choice between bonded and removable depends on whether you drill the plates yourself, and on your replacement approach.

The tab, for identifying and orienting the plate

The tab protrudes from the fitting and signals from the outside that an orifice plate is present in the line, a safety point so that it is neither forgotten nor mistaken. Text can be laser-engraved on it, for example the orifice diameter.

The tab is also used to orient a plate with an eccentric hole. As the hole is always drilled opposite the tab, the tab is oriented upwards during installation, which places the eccentric orifice at the bottom of the flow path for self-draining. The visual marker becomes an installation marker.

Material and manufacturing

The plate is made of 316L stainless steel, electropolished as standard, to remain consistent with the surface requirements of a pharmaceutical circuit. The gasket crimped onto the plate is made from one of the validated compounds in the sanitary range.

Dimensions and correspondence

The plate is fitted like a standard gasket, on the outside diameter of the ferrule face. The clamp, ferrule and tube correspondence table, common to all versions, 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. An orifice plate places more stress on the gasket than a solid gasket, as the plate stiffens the assembly. A stressed installation or excessive tightening damages it more quickly. Compression is achieved at the torque specified for the clamp, never by feel.

Frequently asked questions

Solid or pre-drilled plate?

The solid plate is the standard version delivered, to be drilled according to the calculated flow rate, which leaves the orifice diameter open until the last moment. The pre-drilled plate comes with its bore defined, concentric or eccentric. If you know the target diameter, the pre-drilled plate saves the drilling step.

Concentric or eccentric?

Concentric by default, on lines with no draining constraint. Eccentric, with the bore at the bottom of the flow path, when the line must drain without retention upstream of the plate, typically on a horizontal CIP circuit.

When is the vertical model needed?

On a vertical line. A flat plate retains liquid upstream there; a downward-facing conical plate ensures self-draining. Available up to 4″.

Bonded or removable gasket?

Bonded as standard: if the gasket fails, the complete plate is replaced. Removable when you drill the plates yourself, to avoid contaminating the gasket during machining and to separate gasket replacement from plate replacement.

How is the bore diameter defined?

By calculating the target pressure drop according to flow rate and fluid. It is a hydraulic sizing exercise, handled case by case, not a catalogue value.

How do I choose the plate size?

On the outside diameter of the ferrule, like the clamp. The range covers 1/2″ to 6″, and up to 4″ for the conical vertical model.

The screen gasket is a standard gasket whose centre is occupied by a stainless steel sieving mesh. It filters particles directly in the line, in place of an ordinary gasket, without a strainer or add-on filter housing.

Rubber Fab materials and chemical compatibility guide

Gasket dimensions data sheet

Rubberfab screen gasket references

316 stainless steel mesh, 4 to 325 mesh, filtration from 5,156 to 43 microns

Tri-clamp screen gasket, 316 stainless steel sieving mesh crimped into an elastomer or PTFE sealing gasket. Filters particles in line, interchangeable with a standard gasket. Mesh from 4 mesh to 325 mesh, i.e. from 5,156 to 43 microns, and filter cloths down to 10 microns. FDA and USP Class VI compliant. Sizes from 1/2″ to 6″. Available in a metal-detectable version.

Filtering without a filter housing

The screen gasket replaces a standard gasket and adds a filtration function at the connection point. It protects a pump, a valve or downstream equipment from particles, acts as a prefilter upstream of an expensive membrane, or retains particles in sterile filling products.

The mesh is chosen according to the required fineness. Coarse meshes, 4 to 20 mesh, stop foreign bodies and large debris. Fine meshes, 100 to 325 mesh, go down to 43 microns. Woven filter cloths, combined with a support mesh, reach 10 microns for critical prefiltration.

The peripheral sealing gasket is available in the standard materials, EPDM, PTFE, FKM and silicone, which matches the chemical compatibility and temperature range of the screen to those of the line. A reinforced support, 10 mesh backer, holds fine cloths in place under flow.

Characteristics

Dimensions and correspondence

The gasket is fitted like a standard gasket, on the outside diameter of the ferrule face. The clamp, ferrule and tube correspondence table, common to all versions, 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. A version with an added function, screen, orifice or measurement port, places more stress on the gasket than a solid gasket. A stressed installation or excessive tightening damages it more quickly. Compression is achieved at the torque specified for the clamp, never by feel.

Frequently asked questions

Which mesh size should I choose?

It depends on the size of the particles to be retained. 4 to 20 mesh for debris and foreign bodies, 100 to 325 mesh for fine filtration down to 43 microns, filter cloths to go down to 10 microns. The manufacturer’s filtration guide helps convert between mesh and microns.

Screen or basket gasket?

The screen filters flat at the gasket plane, with a small footprint and limited retention capacity. The basket, or sock, extends into the tube and offers much more surface area, and therefore more capacity before clogging. Screen for a clean flow, basket for a high volume of particles.

Does the screen withstand the same temperature as the gasket?

Yes, the range is that of the peripheral gasket material. A screen with a PTFE gasket withstands higher temperatures than a screen with an EPDM gasket.

On a tri-clamp connection, the gasket does more than seal. Some versions add a function: filtering, regulating, measuring or validating, directly at the connection plane, with no add-on device on the line.

The Smart Gasket is an instrumented gasket with one to four internal passages for thermocouples or accessories. The probe measures the temperature in the flow path, at the gasket plane of an existing fitting, without a thermowell or add-on tapping. It is Rubber Fab’s first historical product.

Instrumented gasket for thermocouples, 1/2″ to 4″, 1 to 4 ports

Smart Gasket clamp gasket, an instrumented gasket with one to four internal ports for thermocouples or accessories. Fitted between two ferrules with the dedicated thermocouple clamp. Sizes from 1/2″ to 4″. 0.090″ ports, compatible with type T, K, J, L, N, R or S probes, long or short. USP Class VI and ADI Free compliant. Temporary or permanent measurement, without a thermowell or costly special fitting.

Measuring in the flow path, at the fitting, without a tapping

Temperature measurement is usually carried out on a dedicated tapping: tee, thermowell, probe, and the associated dead leg. The Smart Gasket moves the probe into the gasket. The thermocouple passes through the gasket and measures at the connection plane, without adding a single tapping to the line.

Each gasket has one to four 0.090-inch ports. One port for a simple measurement, several for thermal mapping or redundancy required during validation. It accepts short or long temperature probes, and a sampling device with a luer lock connection is available.

The Smart Gasket requires the matching Rubber Fab thermocouple clamp, drilled to allow the probes to pass through. Gasket and clamp form a set: holes, ports and number of probes must match. Measurement can be temporary, for a qualification, or permanent in operation.

Characteristics

Dimensions and correspondence

The gasket is fitted like a standard gasket, on the outside diameter of the ferrule face. The clamp, ferrule and tube correspondence table, common to all versions, 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. A version with an added function, screen, orifice or measurement port, places more stress on the gasket than a solid gasket. A stressed installation or excessive tightening damages it more quickly. Compression is achieved at the torque specified for the clamp, never by feel.

Frequently asked questions

Is it ordered with the clamp?

Yes. The Smart Gasket requires the dedicated thermocouple clamp, drilled for the probes. Clamp holes, gasket ports and number of probes must match. Gasket and clamp form an inseparable set.

How many ports should I choose?

One for a simple measurement, several for thermal mapping at the same point or for validation redundancy. The number of ports is fixed during manufacture; it cannot be added afterwards.

Which type of thermocouple?

The gasket accepts types T, K, J, L, N, R and S, in long or short probe versions. The type is chosen according to the temperature range and the reading instrument. Specify the type when ordering.

Four materials are available from stock, each for a specific field of application: EPDM for aqueous media and steam, FKM for oils and solvents, PTFE for maximum chemical inertness, and FEP-encapsulated FKM for chemical resistance with the flexibility of an elastomer. Machining or moulding on request for other needs.

DIN 11864 designations summary

O-ring for DIN 11864 fittings, form A

Aseptic O-ring with no retention zone, EPDM, FKM, PTFE and FEP-encapsulated FKM

Aseptic O-ring for DIN 11864 form A fittings. A sealing element with no dead zone, housed in a standardised groove that compresses it without creep into the flow path. Installed according to DIN 11864-1 v.11.2008, dimensional tolerances to ISO 3601-1. Four materials in stock: EPDM, FKM, PTFE, FEP-encapsulated FKM. FDA, EC 1935/2004 and at least USP Class VI approvals. Machining or moulding on request.

Four materials, four fields of application

The O-ring body is chosen based on fluid and temperature, as for any gasket. The difference lies in the shape, contained in a groove, but the material logic remains the same as for clamp gaskets. The four materials cover most aseptic processes.

FEP-encapsulated FKM deserves a mention. It combines the chemical inertness of the FEP fluoropolymer on the surface with the resilience of an FKM core, giving greater flexibility than solid PTFE. It is the material for hostile chemical media where a bare elastomer O-ring would not hold and where solid PTFE would lack the flexibility to seal.

Aseptic with no dead zone

The DIN 11864 standard defines hygienic and aseptic fittings designed to have no retention zone at the seal. The O-ring is at its heart: housed in a controlled groove and compressed in a controlled manner, it cannot creep into the flow path or create a crevice.

This is the fundamental difference from a flat clamp gasket, whose manual centring and free compression always leave a risk of retention. In an aseptic process, the absence of dead zones is a design requirement, not a luxury. The DIN 11864 fitting also incorporates a compression limiter that minimises the risk of the gasket deforming towards the inside of the tube.

Form A designates the standardised groove geometry for O-rings, the most widespread of the DIN 11864 connections. Sealing repeatability is ensured from one installation to the next, as the groove sets the compression.

Standard and dimensions

The gasket is installed according to DIN 11864-1 v.11.2008. Its dimensions comply with the ISO 3601-1 tolerance standard. The inside diameter and cross-section of the O-ring are defined by the fitting standard and the tube DN.

DIN 11864 fittings exist in three connection forms, threaded, flanged and clamp, all built around the same form A O-ring groove. The correspondence between tube DN, gasket diameter and cross-section is given in the dimensional table, available for download.

Approvals

Aseptic O-rings carry the same approvals as the supplier’s aseptic range: FDA, Regulation (EC) 1935/2004 on food contact materials, and at least USP Class VI. These approvals cover pharmaceutical, biological, chemical and food use.

The material selected must carry the corresponding certificate for the batch delivered. Compliance requirements are assessed material by material and according to the process.

The gasket: the sensitive link in the aseptic fitting

On an aseptic fitting, as on a clamp fitting, the sealing and cleanliness of the process depend on the gasket. A damaged, poorly seated O-ring, or one made of unsuitable material, compromises both sealing and asepsis.

The O-ring is the consumable part of the connection: it is replaced, not salvaged. A gasket that is marked, nicked or outside its temperature range must be changed. The standardised groove limits the risk of incorrect installation, but the choice of material remains the responsibility of the process designer.

Applications

Pharmaceutical, biotechnology, chemical and food processing industries, on aseptic fittings requiring the absence of retention zones. Sterile loops, SIP processes, low dead-volume lines, process points where gasket control takes priority over ease of dismantling.

On frequently dismantled connections where strict asepsis is not required, a flat clamp gasket remains simpler and more economical. The DIN 11864 O-ring is justified when the design requires zero dead zones.

Characteristics

Frequently asked questions

Which material should I choose?

EPDM for water, steam and clean-in-place. FKM as soon as oils, solvents or high temperature are involved. PTFE for maximum chemical inertness. FEP-encapsulated FKM for aggressive media requiring both the chemical resistance of a fluoropolymer and the flexibility of an elastomer. The choice depends on the fluid and operating temperature.

What does FEP encapsulation add to FKM?

FEP encapsulation gives the O-ring the chemical inertness of a fluoropolymer on the surface, while retaining the flexibility of the FKM core. If the encapsulation is punctured, the FKM core continues to resist a wide range of chemicals. It is a compromise between solid PTFE, highly inert but rigid, and a bare elastomer, flexible but less chemically resistant.

Why an O-ring rather than a flat clamp gasket?

Because the O-ring is housed in a groove that contains it, with no possible creep into the flow path and no crevice. The flat clamp gasket, centred by hand and freely compressed, always leaves a risk of retention. In an aseptic process, the absence of dead zones is a regulatory requirement, not a luxury.

What if the required material is not in stock?

The four materials, EPDM, FKM, PTFE and FEP-encapsulated FKM, are kept in stock. For a specific need, a non-standard size or another material, the O-ring is machined or moulded on request.

Form A: what does it mean?

Form A is the DIN 11864 standardised groove geometry for O-rings, the most common one. It sets the cross-section and compression of the O-ring, which guarantees sealing repeatability from one installation to the next.

Tuf-Steel fills PTFE with 50 percent atomised 316L stainless steel. This filler gives PTFE the mechanical strength it lacks: no more creep, no more cold flow, and resistance from -196 °C to +288 °C. It is the most resistant gasket in the range.

Rubber Fab materials and chemical compatibility guide

Tubes Technologies gasket selection guide

Gasket dimensions data sheet

Rubberfab references, Tuf Steel gasket

Guidelines for sanitary gasket materials

PTFE / 316L blend, -196 °C to +288 °C, creep-resistant

Tuf Steel clamp gasket, a proprietary 50/50 blend of unpigmented PTFE and atomised passivated 316L stainless steel. Service range from -196 °C to +288 °C, the widest in the range. The stainless steel filler eliminates PTFE creep and cold flow. Metal-detectable. USP Class VI compliant. Diameters from 1/2″ to 12″. The reference gasket for intensive SIP and WFI.

Where this material is the right choice, and where it is not

Tuf-Steel combines the chemical inertness of PTFE with a mechanical strength that solid PTFE lacks. The 316L stainless steel filler eliminates the creep and cold flow that make solid PTFE leak under thermal cycling. It does not flow back into the tube inside diameter, does not shrink, and holds without re-tightening under intensive SIP as well as in WFI. Its range of -196 °C to +288 °C is the widest in the range, opening it up to steam, hot oil and cryogenic points. It is metal-detectable, an asset in food processing. Backed by a decade of documented use.

Tuf-Steel is among the most expensive gaskets in the range. Its stainless steel filler reserves it for applications that genuinely use its mechanical strength and thermal range. On a cold-water line with no cycling or SIP, a standard PTFE or elastomer is sufficient and costs much less. Its compatibility with highly oxidising products must be checked, as for any filled PTFE.

Type I and Type II: the lip changes installation

Type I, or Type B, is a flat gasket without lip. It is centred by hand in the groove of the two ferrules. This is the most common and least expensive version.

Type II, or Type A, has a centring lip that fits into the inside diameter of the ferrule. The gasket positions itself, cannot shift while the clamp is being closed, and alignment of its inner face with the flow path is guaranteed. On lines where a shifted flat gasket creates retention, or on hard-to-reach installations, the lip eliminates the risk of poor centring.

The choice between the two does not depend on the material, which is identical, but on the centring requirement at the installation point. Both versions cover the same temperature range and the same chemical compatibility.

Material properties

The temperature range and chemical compatibilities come from the manufacturer’s data. Detailed fluid-by-fluid chemical information is provided in the materials guide and the compatibility sheet, available for download.

Dimensions

Standardised dimensions, common to all tri-clamp gasket materials. 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.

Millimetre conversions are for guidance only, based on the manufacturer’s dimensions in inches. 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 or stressed 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. Compression is achieved at the torque specified for the clamp, never by feel. 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.

Each material has a dedicated data sheet with its service ranges, compliance and detailed chemical compatibilities.

Frequently asked questions

Tuf-Steel or Tuf-Flex?

Tuf-Steel for extreme temperatures and the most intensive SIP, with its stainless steel filler and range up to 288 °C. Tuf-Flex for maximum purity in WFI, with its PTFE surface bonded onto an elastomer core. The first is a gasket for strength, the second a gasket for purity and elastic memory.

Type I or Type II?

Type I, without lip, for standard installation. Type II, with centring lip, when the gasket must position itself and not shift, particularly where access is difficult or at points where shifting creates retention. Same material, same range; only the centring differs.

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?

FDA and USP Class VI compliance is stated by the manufacturer for sizes 1″ to 4″. Outside this range, it must be verified before being recorded in a file. The exact certification must appear on the material certificate for the batch delivered.

Pure Seal is a white aseptic PTFE gasket. It combines flexibility and chemical inertness, and is available with or without lip.

Tubes Technologies gasket selection guide

Pure Seal gasket references

Pure Seal clamp gaskets, white aseptic PTFE

White-look Gylon equivalent, with or without lip, custom-machined

Pure Seal clamp gasket, the functional equivalent of Gylon in a white finish. Available with or without lip, custom-machined. Good flexibility and good chemical inertness. Less widespread on the market; availability should be checked depending on dimensions. Diameters and service ranges as per the supplier data sheet.

Where this material is the right choice, and where it is not

Pure Seal offers the flexibility and chemical inertness expected of a modern aseptic PTFE, with a white appearance that distinguishes it from blue Gylon. Unlike the flat, lipless Gylon tri-clamp gasket, it is available with or without lip because it is custom-machined, making it possible to benefit from Type II centring with this family of materials. It targets the same demanding applications as Gylon.

Pure Seal is less common on the market, which means availability must be checked depending on dimensions and lead times may be longer. Public technical data is limited: precise temperature ranges, compliance and chemical compatibilities must be obtained from the supplier before any commitment. It is a niche product handled on quotation.

Type I and Type II: the lip changes installation

Type I, or Type B, is a flat gasket without lip. It is centred by hand in the groove of the two ferrules. This is the most common and least expensive version.

Type II, or Type A, has a centring lip that fits into the inside diameter of the ferrule. The gasket positions itself and cannot shift during closing. For Pure Seal, which is custom-machined, both versions are available.

The choice between the two does not depend on the material but on the centring requirement at the installation point.

Material properties

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.

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.

Each material has a dedicated data sheet with its service ranges, compliance and chemical compatibilities.

Frequently asked questions

Pure Seal or Gylon?

Both are speciality modified PTFEs with similar performance. Gylon is blue, flat without lip in tri-clamp, and more widespread. Pure Seal is white, available with or without lip because it is custom-machined, but less common. The choice depends on availability, appearance and the need for a lip.

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 technical data are guaranteed?

The precise temperature ranges, compliance and chemical compatibilities of Pure Seal must be obtained from the supplier. This product is handled on quotation, with a technical data sheet attached.

Tuf-Flex bonds a PTFE layer onto an elastomer core. The contact surface has the inertness of PTFE, while the body retains the elastic memory of an elastomer. Two cores are available: EPDM up to 149 °C, FKM up to 204 °C.

Rubber Fab materials and chemical compatibility guide

Tubes Technologies gasket selection guide

Gasket dimensions data sheet

Rubberfab references, Tuf flex PTFE / EPDM gasket

Rubberfab references, Tuf flex PTFE / FKM gasket

Guidelines for sanitary gasket materials

Bonded unitised gasket, choice of two cores, without lip and with lip

Tuf Flex clamp gasket, the only unitised gasket in the world: a PTFE layer bonded onto an elastomer core, fully joined. Two versions depending on the core, PTFE on EPDM up to +149 °C, PTFE on FKM up to +204 °C. It combines the chemical inertness of PTFE with the elastic memory of the elastomer. Designed for biopharmaceuticals, ultra-pure water and WFI. Available without lip and with lip. USP Class VI compliant. Diameters from 1/2″ to 12″. Imparts no taste or odour.

The unitised principle, common to both versions

Tuf-Flex resolves the compromise of the critical sanitary fitting. Solid PTFE creeps and leaks at delta T. An enveloped gasket, whose two materials are not bonded, gives inconsistent results and also creeps over time. A bare elastomer leaches extractables.

Tuf-Flex presents the fluid with a PTFE surface bonded onto the core in a single, fully joined part, not simply enveloped. The result: no leaching of elastomer or particles, and the elastic memory of the core is retained, so no re-tightening is needed. The gasket maintains its inside diameter without re-tightening or leaking, including under SIP cycles. It is the gasket for WFI, ultra-pure water and demanding biopharmaceutical applications. It imparts no taste or odour, which also makes it suitable for challenging food processing applications.

Two cores, two fields of application

The only difference between the two versions is the core material, beneath an identical PTFE surface. This core sets the allowable temperature and the behaviour if the envelope is breached.

The choice is based on two criteria. Temperature first: above 149 °C, the FKM core is mandatory. Chemical safety second: on a line where an envelope incident would expose the core to oils or solvents, the FKM version holds where EPDM would swell. On a conventional aqueous circuit below 149 °C, the EPDM version is sufficient and costs less.

Where Tuf-Flex is the right choice, and where it is not

Tuf-Flex is the obvious choice wherever purity and dimensional stability under SIP are the priority: WFI, ultra-pure water, bioprocesses, sterile filling points, taste-sensitive food processing lines. Its PTFE surface does not leach, its elastic memory avoids re-tightening, and it maintains its inside diameter cycle after cycle.

It is more expensive than a standard elastomer or an enveloped gasket. On a simple line with no purity requirement or SIP cycling, it represents an extra cost with no useful benefit. Its compatibility must be checked with highly oxidising products, as for any PTFE. The choice of core must be explicit: an EPDM version installed on a 180 °C line would be outside its range.

Type I and Type II: the lip changes installation

Type I, or Type B, is a flat gasket without lip. It is centred by hand in the groove of the two ferrules.

Type II, or Type A, has a centring lip that fits into the inside diameter of the ferrule. The gasket positions itself and cannot shift during closing. Tuf-Flex is available in both versions, whatever the core.

The choice between the two does not depend on the material but on the centring requirement at the installation point.

Material properties

The temperature ranges and chemical compatibilities come from the manufacturer’s data. Detailed chemical information is provided in the materials guide and the compatibility sheet, available for download.

Dimensions

Standardised dimensions, common to all tri-clamp gasket materials. 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.

Millimetre conversions are for guidance only, based on the manufacturer’s dimensions in inches. 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.

Tuf-Flex compared with other materials

A gasket material is chosen based on temperature, fluid, dismantling frequency, regulatory requirements and cleaning method. Here is what sets the main materials apart.

Each material has a dedicated data sheet with its service ranges, compliance and chemical compatibilities.

Frequently asked questions

EPDM core or FKM core?

The EPDM core covers aqueous circuits up to 149 °C; it is the standard and most economical version. The FKM core goes up to 204 °C and, if the PTFE envelope is breached, resists oils and solvents where EPDM would swell. FKM for high temperature or chemical safety, EPDM otherwise.

Tuf-Flex or enveloped PTFE?

Enveloped PTFE encases a core without being bonded to it, which gives inconsistent results between the two materials and creeps over time. Tuf-Flex bonds the PTFE onto the core in a single unitised part, which maintains the inside diameter without re-tightening. With repeated SIP, the difference in service life is clear.

What happens if the PTFE envelope is punctured?

On the FKM version, the exposed core resists a wide range of chemicals, which limits the consequences of an incident. On the EPDM version, the exposed core withstands aqueous media but not oils or solvents. This is a selection criterion on lines with a chemical risk.

Type I or Type II?

Type I, without lip, for standard installation. Type II, with centring lip, when the gasket must position itself. Both cores are available in both versions.

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.

FKM, or Viton, resists oils, solvents and acids where EPDM fails, with thermal resistance up to 204 °C. Less flexible than EPDM, it requires more care with surface finish and tightening.

Rubber Fab materials and chemical compatibility guide

Tubes Technologies gasket selection guide

Gasket dimensions data sheet

Rubberfab references, Type I gasket without lip

Rubberfab references, Type II gasket with lip

Guidelines for sanitary gasket materials

FKM fluoroelastomer, -34 °C to +204 °C, without lip and with lip

FKM clamp gasket, known under the Viton brand, available without lip (Type I) and with centring lip (Type II). Service range from -34 °C to +204 °C, suitable for steam applications. Resists oils, solvents and acids. FDA and USP Class VI compliant. Diameters from 1/2″ to 12″. Low gas permeability, good resistance to ozone and oxidation.

Where this material is the right choice, and where it is not

FKM withstands oils, fats, hydrocarbons, most solvents and acids, and goes up to 204 °C. It is the material for fatty processes, solvent lines, hot points and circuits where EPDM swells. Its low gas permeability and ozone resistance also make it a gasket of choice on gas lines and ozonated air lines. It is suitable for steam applications.

FKM is less effective against strongly oxidising products, concentrated nitric acid, high-concentration hydrogen peroxide, which degrade it. It is also less flexible than EPDM or silicone, making it more demanding on face quality and tightening to guarantee a seal. Its cost is higher than that of EPDM. On a purely aqueous circuit with no oil or high temperature, EPDM remains the best value for performance.

Type I and Type II: the lip changes installation

Type I, or Type B, is a flat gasket without lip. It is centred by hand in the groove of the two ferrules. This is the most common and least expensive version.

Type II, or Type A, has a centring lip that fits into the inside diameter of the ferrule. The gasket positions itself, cannot shift while the clamp is being closed, and alignment of its inner face with the flow path is guaranteed. On lines where a shifted flat gasket creates retention, or on hard-to-reach installations, the lip eliminates the risk of poor centring.

The choice between the two does not depend on the material, which is identical, but on the centring requirement at the installation point. Both versions cover the same temperature range and the same chemical compatibility.

Material properties

The temperature range and chemical compatibilities come from the manufacturer’s data. Detailed fluid-by-fluid chemical information is provided in the materials guide and the compatibility sheet, available for download.

Chemical resistance table

Dimensions

Standardised dimensions, common to all tri-clamp gasket materials. 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.

Millimetre conversions are for guidance only, based on the manufacturer’s dimensions in inches. 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 or stressed 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. Compression is achieved at the torque specified for the clamp, never by feel. 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.

Each material has a dedicated data sheet with its service ranges, compliance and detailed chemical compatibilities.

Frequently asked questions

FKM or EPDM?

FKM as soon as oils, fats, solvents or a temperature above 149 °C are involved. EPDM on purely aqueous circuits, where it is more flexible, more tolerant of tightening and cheaper. FKM does not replace EPDM with strong oxidisers, where neither is ideal.

Type I or Type II?

Type I, without lip, for standard installation. Type II, with centring lip, when the gasket must position itself and not shift, particularly where access is difficult or at points where shifting creates retention. Same material, same range; only the centring differs.

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?

FDA and USP Class VI compliance is stated by the manufacturer for sizes 1″ to 4″. Outside this range, it must be verified before being recorded in a file. The exact certification must appear on the material certificate for the batch delivered.