by Denise Sullivan Denise Sullivan No Comments

Expanded PTFE vs. PTFE

expanded PTFE

Polytetrafluoroethylene (PTFE) is one of the most common materials used for seals. Expanded PTFE, or ePTFE, is a soft material with many of the same properties as PTFE. However, ePTFE is more flexible, making it a better choice for specific applications.

How does ePTFE compare to PFE? For better clarification, let’s look at some of the aspects of the two.

What is Expanded PTFE

Expanded Polytetrafluoroethylene (ePTFE) is a PTFE resin created through a unique processing method that includes stretching, making it flexible. Expanded PTFE has a mesh structure ideal for medical equipment, food processing, oil and gas, and any other industry requiring tight seals.

Like its counterpart PTFE, ePTFE is non-toxic, hygienic, and chemically inert. In addition, its flexible nature allows it to seal tightly over surfaces where traditional seals won’t work. 

Advantages of ePTFE 

Expanded PTFE has high sealability, especially at low stress. It can compensate for irregularities in the surface to create a steadfast seal. The ePTFE gasket sheets have superior resistance to creep and cold flow and adapt well to sealing surfaces.

Applications ePTFE 

The ePTFE gasket sheets have a porous nature making them ideal for use in medical devices. For example, it is found in dental implants and barrier membranes in medical equipment. It is also found in electronic insulators and high-performance filters.

The oil and gas industries use ePTFE sheets to even out bumps and ridges in chemical pipe flanges. Smoothing out the bumps helps to provide a tighter seal between the flanges for better leak control.

Other applications for ePTFE include:

  • Pumps
  • Glass-lined flanges, reactors
  • Heat exchangers
  • Apparatus constructions

Properties of ePTFE 

ePTFE is 100% multidirectional and is physiologically inert for all recommended applications. Other technical properties of ePTFE sheets include the following:

  • Chemical resistance in the entire pH range (except for molten alkali metals)
  • Temperature Range: -268°C to 270°C (-450°F to 518°F).
  • Density of 0.85g/cm3 +/- 0.10g/cm3 
  • Pressure range of vacuum up to 200bar (3000psi)

What is PTFE

Polytetrafluoroethylene (PTFE), also known by its trade name Teflon®, was discovered in the 1950s by Dupont Chemist Roy J. Plunkett. It is a non-wetting, high-density material that is resistant to high temperatures.

Because of its high melting point and insolubility in most solvents, PTFE is the ideal choice for most sealing applications. In addition, PTFE can be unfilled (virgin) or filled with various compounds, such as glass or carbon. 

Advantages of PTFE 

Using PTFE as a seal or gasket has many incredible advantages. These benefits make it the ideal choice for applications across many fields. Let’s take a look at some of those advantages. 

PTFE has a high-temperature resistance. PTFE can withstand temperatures of up to 500°F or 260°C. In addition, PTFE is chemically resistant to aggressive chemicals such as solvents, acids, and bases. 

Along with its temperature and chemical resistance, PTFE has non-corrosive properties and can be used as electrical and thermal insulation. This versatile material comes in a wide range of thicknesses, fillers, and compressed sheets.

Applications PTFE 

There are several applications in which PTFE is the ideal sealing solution. Industrial plants use PTFE as envelope gaskets to contain leakages of the substances being managed. The substance’s water resistance makes it suitable for industrial plants, the food industry, and medical laboratories.

PTFE is also used in construction because of its low frictional quality, which extends the life of the PTFE. The sheets are also used in industries where highly reactive substances because of the sheet’s resistance to acids. 

Properties of PTFE 

PTFE’s low coefficient of friction is not the only property that makes it ideal for many sealing applications. Other properties include:

  • A density of 2.10e3 – 2.2e3 kg/m3
  • Tensile strength is 2.07e7 – 3.45e7 Pa
  • Max Temperature 250°C to 271°C (482°F – 520°F)
  • Melting Temperature 215°C – 339°C ( 599°F to 642°F)
  • Chemical resistance to the entire pH range (except for molten alkali metals)

Conclusion

Both ePTFE and PTFE are suitable for most sealing applications. Determining which product is necessary depends on the application. Contact us today to learn more about our PTFE sealing options.

by Denise Sullivan Denise Sullivan No Comments

Ball Valve Components: What Are They

ball valve components

Ball valves are designed to control flow by rotating an internal ball within a housing. They’re often used for applications where there’s a need to regulate pressure, temperature, or flow rate.

A ball valve has two main parts: a body with a central opening and a ball that fits into the opening. As the ball rotates, it opens or closes the valve. In addition to the main parts, ball valves have different internal components that help them work in different environments. Standard ball valve components include:

  • Chevron packings
  • O-rings and backup rings
  • Floating seats
  • Inserts

Keep reading to learn more about these components.

Chevron Packings

Chevron packings are also called v packing or vee packing seals. These seals automatically react to changes in pressure. Multiple chevron seals are used together to form the overall seal. While these seals have a v-shape, they are shipped with a male and female adapter to provide a flat surface rather than the v-shape.

Chevron ball valve components work well at sealing fluid in centrifugal, static, and reciprocating environments. They are recommended to reduce pressure and avoid shrinkages in the presence of linear or rotary movement. 

These seals are manufactured in virgin PTFE, modified PTFE, and glass or carbon-filled PTFE. While virgin seals are ideal for many conditions, filled compounds are recommended for most applications. Your provider will recommend the optimum PTFE compound.

O-Rings and Backup Rings

O-rings are a standard ball valve component. They are used whenever soft sealing is required to help prevent extrusion. The design of these seals allows them to be used in harsh conditions and with aggressive chemicals.

The o-rings found in ball valves are often used with backup rings. They can be made from neoprene, silicone rubber, polyurethane, and PTFE. The precise material will depend on the application and environment that the seal is employed.

Backup rings are circular sections, which may be cut or uncut, that help prevent the extrusion process. These are employed alongside o-rings or lip seals when couplings are not suitable.

Floating Seats 

A floating ball valve is one where the seat holds the ball in place while it floats around in the valve body. Pressure from the gas or liquid helps to push the ball against the downstream seat to form a tight seal.

Floating seats are used in several applications, such as oil and gas, cryogenic,  heating, and pharmaceuticals. However, they are most commonly found in hydraulic systems. The type of polymeric material used in these seats depends on maximum pressure, working temperature, or the type of gas or fluid it regulates.

Inserts

Like o-rings, inserts are in seats with soft sealing. This gasket can be manufactured from several different thermoplastic materials depending on its conditions. 

For example, virgin PTFE seals are unsuitable for butadiene or styrene service. PEEK material is not resistant to nitric acid or sulphuric acid. However, filled PTFE works well in high temperatures and low pressures, while PCTFE is ideal for cryogenic applications.

Conclusion

Ball valve components help to ensure the valves seal correctly. Depending on the valve application, these components can include o-rings, backup rings, chevron packing, inserts, and floating seats. 

Finding the appropriate seal inserts and materials can be challenging. Contact us today for help determining what best suits your application.