by Denise Sullivan Denise Sullivan No Comments

Introduction to PTFE Lip Seals

PFTE Lip seals

Radial shaft seals are often found in aggressive environments with high temperatures and pressures. Unfortunately, these environments are also frequently dry-running and unsuitable for traditional radial shaft seals. So, what are the options if traditional radial shaft seals won’t work? Using PTFE lip seals as rotary shaft seals can offer better protection and longer life than conventional radial shaft seals. Understanding these lip seals are essential to helping you make the right choice for your sealing needs.

What Are PTFE Lip Seals

PTFE (polytetrafluoroethylene) lip seals have a lip on the interior diameter (ID) that allows it to fasten to an outer diameter (OD) of a metal casing or shaft. The seal is completed with a gasket sandwiched between the sealing lips.

Not all lip seals are spring-energized. Therefore, the force from radial contact is lower. The lower pressure allows the seal to function at higher surface speeds of up to 10,000 sfpm. This type of seal is for high rates, making it the go-to choice for sealing rotating shafts.

PTFE Lip Seal Fillers

PTFE Lip seals can be enhanced by using fillers instead of virgin PTFE. Fillers can help the seal withstand sintering temperatures. Some of the filled compounds include:

  • Carbon-Graphite
  • Carbon Fiber
  • Aromatic Polyester
  • Molybdenum Disulfide and Fiberglass
  • Fiberglass
  • Graphite
  • Mineral
  • Stainless Steel

Each filler offers higher temperature resistance and lower creep rates than virgin PTFE. In addition, some offer lower abrasion or better corrosive protection depending on the filler type. Which type of filler you want will rely on the application where you use the lip seals. 

Applications That Use PTFE Lip Seals

PTFE lip seals are found in most applications where speed is concerned. However, they also are ideal for conditions where highly corrosive compounds or in dry, abrasive environments. 

Aerospace

The aerospace industry needs seals that can cope with extreme temperatures, surface velocities, and high pressures. External gearbox seals are just one place where PTFE lip seals are used in the aerospace industry.

Lip seals can handle the extremes and offer advanced fuel consumption efficiency. Better efficiency of burning about half-gallon of fuel per mile can save airlines an operating cost of $1.7 million per year. 

Other instances in which the aerospace industry uses lip seals include military applications such as:

  • Lift fans for vertical lift
  • Wing flap and slats actuator seals
  • Rotorhead
  • Equipment in arresting system to catch aircraft as it lands on aircraft carrier decks

Automotive

In the automotive industry, PTFE lip seals are employed in the drive shafts of the top-fuel blowers in NASCAR engines. Traditional crankshaft seals were burning out in these engines due to the high speeds and rapid pressure increases within five minutes at racing speeds.

They are also in e-drive and cooling systems in electric vehicles. Lip seals in electric cars can handle the shaft speeds seen in these automobiles. Electric vehicles can run at over 18,000 RPM, a higher rate than gas-powered cars. 

Conclusion

PTFE lip seals are ideal for rotary shafts operating at high speeds and temperatures, such as in the automotive or aerospace industries. Choosing suitable fillers can also help extend the seal’s life. Contact us today, and we can help you determine which PTFE lip seal options you want.

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.