Envelope Gaskets - TFM ^TM- Elastik Gasket

WS 7110/1.4571 | WS 7110/3822, 3825,7550 | WS 7110/1.4571/3822, 3825,7550
The pharmaceutical-chemical industry requires low permeation for sealing applications, high chemical resistance, sturdy mechanical resilience and easier processability. TFM™, a PTFE of the second generation, has proven itself. The particles melt more easily into a dense, low pore polymer structure due to the more homogeneous crystalline structure as a result the tightness is significantly improved. High quality 3M™ Dyneon™ TFM™ is used for the envelope gaskets.
PTFE envelope gaskets combine the positive characteristics of TFM™-material with the mechanical behavior of the relevant inserts and have a very high chemical resistance. The positive characteristics are completed with a sturdy diffusion barrier at the inner diameter of the gasket and are optimized across the entire gasket diameter with regards to diffusion. This combination gasket is therefore used for a wide range of applications.

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Optimised corrugated ring geometry

The IDT-elastic gasket with metallic corrugated ring inserts and diffusion barrier [PW-I] was developed for steel and stainless steel flange connections as well as defined as a standard in the chemical industry. This gasket system can be used at 40 bar and 200°C simultaneously – which cannot be achieved with classic PTFE gaskets – thanks to the optimized coordination of the mechanical characteristics of the stainless steel corrugated ring with the TFM™-envelope. The corrugated ring insert is also used to increase the bursting and blow-out resistance. The geometric design of the corrugated ring was chosen in such a way that it prevents cutting through the enclosing TFM™-envelope [cross-sectional flat area] and that it has an optimized characteristics profile due to the chosen corrugated partitions of 3.0mm.
Other TFM™-envelope combinations with inserts have proven themselves in areas which are sensitive to stress, especially for glass lined flange connections. The conditions which are found on the sealing surfaces specifically in enamel applications, such as aggressive media, low surface pressure, sensitive flange surfaces, waviness and warping on the flange sealing surfaces, place high demands on the sealing system.

Non-metallic insert | SIGRAFLEX® EMAIL [WS 3825]

The graphite sheet SIGRAFLEX® was developed specifically for use in PTFE-coated non-metallic gaskets, which as a nonmetallic insert ensures an ideal interplay of the already outstanding characteristics of the individual components. There is a significant improvement of the sealing technological properties of the PTFE-envelope gaskets thanks to the good recovery property of the graphite, the stainless steel foil insert close to the
surface and the combination of the individual layers without adhesives. SIGRAFLEX® is a multi-layer sealing sheet made from flexible graphite foil which is reinforced with two 0.05mm thick stainless foils.
SIGRAFLEX® is made in sheet thicknesses of 2.0mm and 3.0mm and consists of two 0.5mm thick outer and one 1.0mm or 2.0mm thick inner layers of flexible graphite with the density of 1.1g/cm³. The compound is made without adhesive using a special process and corresponds therefore to the highest requirements with regards to strength even at high temperatures.

TFM™-envelope gasket for food and pharma applications

Quality systems, which regulate the manufacture of medicines and pharmaceutical substances were successfully introduced in the EU. The current good manufacturing practice [GMP] guarantees the safety of pharmaceutical raw materials and products but also applies to cosmetics, food and feed and also includes the relevant quality requirements. IDT has developed an envelope gasket for these applications in consideration of GMP. This sealing system combines the positive characteristics of the TFM™-material as an envelope with those of the non-metallic insert made from the biaxial-oriented UNIFLUOR® [WS 7550]. All materials in this combination gasket are FDA conform. Possible leaching of filler or colour pigments from the PTFE insert are safely prevented by the TFM™-coating. The sealing system convinces with a high diffusion tightness whilst featuring at the same time an ideal compensation behavior which is achieved thanks to the low density of the non-metallic insert. The blow-out resistance is increased for designs with additional corrugated ring insert.

Envelope gaskets for electrostatic discharge

Envelope gaskets can be of a dissipative/conductive design for applications for which a static discharge is necessary and required. For this purpose, it is possible to realise the discharge using an electrically conductive PTFE-envelope made from Dyneon™ TFM™ 6221 WS 7221 and/or using an grounding tab/ grounding wire which is fitted to the outer diameter of the corrugated ring. The discharge of the electrical load is ensured via glass lined pipes, metal reinforcement and fan-type lock washers. The retaining brackets can also be fitted to the corrugated ring as assembly and centring aids.

Grounding and equipotential bonding in pipes with insulating gaskets

The grounding of a plant can be obstructed by insulating components such as gaskets or insulating operating materials like greases. The remaining conductive components have to be connected to each other and grounded when using insulating materials such as spacers made from plastic with high resistance. Alternatively, it is possible to ground every plant part individually. In this environment it is particularly important to consider parts which are not visible from the outside, such as: Ball valves with insulating gaskets or also metal inserts in gaskets.

It depends on the specific conditions if equipotential bonding is necessary for pipelines and gaskets:

Insulating coating on the inside
Insulating coating on the outside
Gasket conductive or insulating

Conductive or insulating gaskets require more grounding efforts depending on the situation.
Requirements in equipotential bonding and grounding of conductive objects:
Normally: Grounding is necessary, if capacity > 10 pF

Resistance < 1 MΩ at deep measuring voltage [e.g.10 V] In special cases: Grounding is also necessary

Resistance < 1 MΩ at deep measuring voltage [e.g.10 V] In special cases: Grounding is also necessary

Independent from capacity:

if close to strong charge generating processes
if in touch with product flow in the equipment
if capacity > 3 pF and in zone 0 or 1 of materials in explosive group IIC

Resistance < 100 MΩ is enough, if:

Charge rate < 1μA and
Capacity < 100 pF

Industrial Safety and Health Regulations

The technical regulations on industrial safety and health reflect the regulations on the state of the art, occupational medicine and hygiene and other workplace related findings for the provision and use of equipment and the operation of plants which require monitoring. The Chemistry Committee has created the following professional association regulation “Avoiding Risks of Ignition Resulting from Electrostatic Charges” [BGR 132]. They were adjusted to reflect current law, the developed state of the art and at the same time included in the TRBS 2153 during the development of uniform and coherent rules and procedures. The regulations correspond to the BGI 5127 “Avoiding Risks of Ignition Resulting from Electrostatic Charges” [Information leaflet T 033]. These technical rules apply to the evaluation and avoidance of risks of ignition resulting from electrostatic charges in explosive areas and for the selection and implementation of protective measures to avoid such risks.

Very good media resistance with the exception of liquid alkali metals and some fluorine compounds
Suitable for increased requirements in operational safety, tightness and product purity
Long-term stable compression and recovery characteristics
PTFE is physiologically harmless for continuous operation temperatures up to 260°C as per BG no. 21
Low permeability towards gases and liquids
Anti-adhesive surface
UV and ageing resistant [does not apply to the non-metallic insert made from Centellen WS 3822]
Good non-stick characteristics
Excellent [di]electric properties
FDA-conform PTFE-envelope as well as non-metallic insert made from UNISEAL® [WS 3400], AFM 34 and UNIFLUOR® [WS 7550]
Complies with TA Luft 2002 [VDI 2440/2200] leakage requirements
For compounds with conductive pigment TFM 6221: Electrical conductivity, FDA-conform
For designs with corrugated ring and/or SIGRAFLEX® EMAIL [WS 3825]: Temperature resistance from -200 °C to 200 °C [short term 230°C]
For designs with SIGRAFLEX® EMAIL [WS 3825]: The metal reinforcement in the SIGRAFLEX® material, which is close to the surface and free from advesives, prevents sideway slipping of the graphite laminate for unreinforced or glued graphite inserts [unreinforced or glued] due to flow patterns of the PTFE-envelope
For designs with SIGRAFLEX® EMAIL [WS 3825]: The cold flow and warm flow characteristics typical for PTFE is compensated by the superior recovery behaviour even at high temperatures
For designs with corrugated ring and/or SIGRAFLEX® EMAIL [WS 3825]: Increased blow-out resistance
For designs with corrugated ring and/or Centellen [WS 3822]: Temperature resistance from -50°C to 150°C

For aggressive media which is hazardous for the health
Broad range of applications primarily in the chemical and petrochemical sector
Use in food sector and pharmaceutical production
Used for high requirements in process purity
Gasket systems for pipeline flanges, device and container flanges
In steel pipelines:
TFM™-envelope gasket with corrugated metal ring
TFM™-envelope gasket with aramid fiber insert with/without corrugated metal ring
TFM™-envelope gasket with PTFE insert with/without corru- gated metal ring
For glass lined pipelines, containers, nozzles and assembly openings as well as for low surface pressures, waviness and warping of the flange sealing surfaces and for sensitive flange surfaces, stress and bend sensitive flange connections:
TFM™-envelope gasket with SIGRAFELX® EMAIL insert with/without corrugated metal ring
TFM™-envelope gasket with PTFE insert with/without corru- gated metal ring

Product Range

Technical delivery conditions for non-metallic inserts as per DIN 28091

Envelope gaskets
Design with corrugated metal ring for the use in steel pipe- lines, dimensions as per DIN EN 1514-1 and DIN EN 12560-1 or ASME B 16.21
Design with non-metallic insert, dimensions as per DIN EN 1514-3 and DIN EN 12560-3 or ASME B 16.21
Design with corrugated metal ring and non-metallic insert, dimensions as per DIN EN 1514-3 and DIN EN 12560-3 or ASME B 16.21
Envelope gaskets with corrugated metal ring WS 7110/1.4571 PW-I; thickness: 3.5mm
Envelope gaskets with corrugated ring and non-metallic inserts WS 7110/1.4571/3822; WS 7110/1.4571/3825; WS 7110/1.4571/7550; thickness: 6.5mm or in consideration of the design recommendation 8.5/10.5mm

Envelope Gaskets - TFM ^TM- Elastik Gasket