Styles of PTFE

Molded and Sintered PTFE: This type of PTFE was the first to be introduced to the market. This style is made from virgin or reprocessed PTFE resin, without fillers, which is then molded, compressed and sintered. As with any other type of plastic, PTFE has a high creep factor when compressed. The creep factor is detrimental and can lead to having to re-tighten the bolts to maintain seating pressure and prevent leakage. The higher the temperature in the application it is used for, the more the creep factor will increase. Even with these drawbacks, PTFE is affordable, easily available and highly chemical resistant.

Skived PTFE: This style is similar to molded and sintered PTFE as it is also make of virgin or reprocessed PTFE without fillers. Instead of molding an individual sheet, the sheets are taken from a billet of PTFE with a process called skiving. The skiving process was developed to overcome manufacturing deficiencies of the molding process. Skived PTFE shares the same creep characteristics as molded and sintered PTFE.

Molded or Skived Filled PTFE: In order to correct the creep characteristics of molded and skived PTFE, manufacturers started adding mineral fillers or fibers in order to reduce creep factor. This indeed reduced the creep characteristics but not by a significant amount.

Restructured Filled PTFE: Besause the addition of fillers in the molding process was not enough to significantly reduce creep, a new manufacturing process was developed to produce filled PTFE sheets. In this new process the material is laminated before being sintered, which yeilds a highly fibrillated structure with significantly less creep. The different fillers used in this process are as follow: • Barite: Added for use in strong caustic service. Also FDA compliant.

• Mineral Silica: Used for strong acidic service.

• Hollow Glass Microshperes: Used to increase compressibility.

• Synthetic Silica: Used as subsitute for glass microspheres.

Expanded PTFE: This style of PTFE is made by heating and stretching PTFE before sintering it. Lke all PTFE it has strong chemical resistance, but unlike molded or skived PTFE, this material has a high compressibility and is good for use in flanges made from fragile materials. The only drawback to this material is that its floppy and difficult to install, especially if the flanges cannot be separated.

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PTFE Stem Packing

PTFE Stem Packing: Description: Our PTFE stem packing manufactured in the USA from 100% PTFE resin with no fillers or additives and is extruded, eliminating the leak path potential allowed by conventinal spiral tape wrapping. Our PTFE stem packing is also slightly expanded allowing grater compressibility under lighter compression loads.

For customers requiring Graphite filler, Graphite can be added with loading levels as high as 20% by weight.

Technical parameter: Temperature Min. -450ºF (-268ºC)/Max 500ºF (315ºC)
Speed 200 fpm (1 m/s)
Pressure 1450 psi (100 bar)
PH Value 0-14 (except molten alkali metals and elemental fluorine)

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Ameri-lon Pump Packing

Construction: Cross-lock Braid Features: Manufactured from a skived PTFE and Graphite blend. No surface lubricant is required for this naturally lubricious packing, so it never washes out. Unlike filament yarn packings wicking is not an issue. This packing performs exceptionally in abrasive applications.
It last long and stands up to tough applications. It is the most versatile valve or pump packing we sell which is why we gave it has Ameri- in it's name.
Usage:
As both PTFE and graphite are excellent sealing materials, they give Ameri-lon packing exceptional sealing properties that other products cannot offer. Ameri-lon packing is tough and durable, self-lubricant, heat and chemical resistant. It also has good thermal conductivity and very low friction factor.
Application:
Excellent versatile packing for pumps, valves, mixer, agitators or other equipments. Great on abrasive applications. Suitable for use in any rotary, reciprocating or static gland,against all chemicals except very strong oxidizers such as Oleum, Aqua Regia,fuming Nitric Acid and Fluorine.
Limitations: pH: 0-14
Pressure: Up to 300 psi Pumps / 4000 psi -Valves
Shaft Speed: Up to 4500 feet per minute
Temp Rating: -328 to 536 F
Mechanical Seals : http://www.mechanicalseals.net

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Vulcan Multi-Spring Seals

Introduction Vulcan Multi-Spring Seals

Vulcan’s extensive 16XX range of Multi-Sprung Seals are commonly specified for arduous applications, such as corrosive process fluids or demanding operating parameters. The standard designs are available with a chemically resistant PTFE wedge component, which is spring loaded to force the flexible angular lip of the wedge into tight contact with the shaft.

The same spring force impacts a sufficient load to the rotary face to create a suitable seal interface with a varied choice of standard stationary seats, most commonly our Type 25 V Seat. Balanced face designs are also available for higher duty applications. ‘O’-Ring variants, of both balanced and nonbalanced Types, are available as standard. All the seal faces and wedges interchange with most common competitor designs by fitting into their retainers.

Applications

The 16XX family range are ideally suited for corrosive duties and are commonly utilised in the chemical industry, due to the inertness and sealing nature of the wedge design. These seals are also very suitable for a wide spectrum of application conditions. Their operating suitability range is enhanced by the ‘O’-Ring alternative design and the wide range of available elastomers.

Standard Vulcan 16XX Types Type 1609 Series Standard multi-sprung, grub screwed seal, available in a wide variety of face and secondary seal, materials and designs. Type 1659 Series As above, but compact design complies to DIN 24960 (EN12756) and ISO 3069 standards. Type 1645 Series Thin profiled, multi-sprung, grub screwed seal, conforming to ANSI B73 for American standard equipment.

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What are the different styles of PTFE

Molded and Sintered PTFE:

This type of PTFE was the first to be introduced to the market. This style is made from virgin or reprocessed PTFE resin, without fillers, which is then molded, compressed and sintered. As with any other type of plastic, PTFE has a high creep factor when compressed. The creep factor is detrimental and can lead to having to re-tighten the bolts to maintain seating pressure and prevent leakage. The higher the temperature in the application it is used for, the more the creep factor will increase. Even with these drawbacks, PTFE is affordable, easily available and highly chemical resistant.

Skived PTFE:

This style is similar to molded and sintered PTFE as it is also make of virgin or reprocessed PTFE without fillers. Instead of molding an individual sheet, the sheets are taken from a billet of PTFE with a process called skiving. The skiving process was developed to overcome manufacturing deficiencies of the molding process. Skived PTFE shares the same creep characteristics as molded and sintered PTFE.

Molded or Skived Filled PTFE:

In order to correct the creep characteristics of molded and skived PTFE, manufacturers started adding mineral fillers or fibers in order to reduce creep factor. This indeed reduced the creep characteristics but not by a significant amount.

Restructured Filled PTFE:

Besause the addition of fillers in the molding process was not enough to significantly reduce creep, a new manufacturing process was developed to produce filled PTFE sheets. In this new process the material is laminated before being sintered, which yeilds a highly fibrillated structure with significantly less creep. The different fillers used in this process are as follow:

• Barite: Added for use in strong caustic service. Also FDA compliant.

• Mineral Silica: Used for strong acidic service.

• Hollow Glass Microshperes: Used to increase compressibility.

• Synthetic Silica: Used as subsitute for glass microspheres.

Expanded PTFE:

This style of PTFE is made by heating and stretching PTFE before sintering it. Lke all PTFE it has strong chemical resistance, but unlike molded or skived PTFE, this material has a high compressibility and is good for use in flanges made from fragile materials. The only drawback to this material is that its floppy and difficult to install, especially if the flanges cannot be separated.

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General Service of Metal Bellows

Metal Bellows seals can seal with Flexible Graphite instead of a rubber boot or O-Ring Elastomers allowing it to be used in higher temperature applications. No Springs to clog. Metal Bellows seals are a very effective method of maintaining Mechanical Seal face pressure on the seal face.

Metal Bellows seals that do use O-Rings only require one static o-ring to seal off any leakage along the shaft in Chemical Service this o-ring can be Aflas, EPDM, Nitrle, Viton, Encapsolated PTFE, Ameri-rez, or PTFE.
Because the O-Ring is static it will not wear on the shaft. When installed correctly metal bellows seals will provide exceptionally long service. Metal bellows seals are and excellent solution on chemical applications where Kalrez, Chemrez,Viton, FKM, Buna, Aflas or EPDM are not compatible.
For many years an inexpensive form of metal bellows seals have been used very successfully in the waste water / sewage industry and in the agricultural fields pumping irrigation water. These Mechanical Seals were generally made of a formed bellows rather than a welded bellows. Welded bellows seals are much stronger and have superior flex and recovery characteristics which are more ideal to holding seal faces together but cost more to manufacture. Welded metal bellows seals are less prone to metal fatigue and are available in single and double ply.

General Service of Metal Bellows

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