PTFE Ball Valve Seats
by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

The Basics of Ball Valve Seat Materials

Ball valves play a critical role in controlling the flow of fluid and pressure within a pipeline, but their effectiveness and safety is only as good as the seat material used. In this blog post, we are going to review the basics of five commonly used ball valve seat materials.

Ball Valves

Whether found in a petrochemical application where a leak could be environmentally devastating, or in a pharmaceutical laboratory where cleanliness and sanitation are critical, ball valve seats must be reliable and robust. A ball valve consists of the body of the valve, the body cap, the stem, the hollow ball, and the round ball valve seat. 

The ball valve seat is responsible for sealing the fluid inside and uniformly distributing the seating stress. In soft seat ball valve designs, either an elastomer or polymer is used as the seal and are inserted into a metallic seat ring. This approach, as opposed to hard seat ball valves, is popular because it provides good sealing action, is lighter weight, and more cost effective. 

Key Properties of Ball Valve Seat Materials

When choosing a polymer material for a ball valve seat, there are numerous factors that are involved. Key material properties include …

  • Sufficient ductility to provide a reliable seal
  • Dimensional stability to ensure the ball valve seat retains its shape for reliable sealing and performance
  • Very low friction to keep stem torque at a minimum
  • Low coefficient of thermal expansion so that the ball valve seat retains its shape when temperature changes occur
  • Excellent wear resistance for a long service life
  • Chemical compatibility with all media involved 

In some operating environments, it is also important that ball valve seat materials exhibit these properties:

  • Low moisture absorption to prevent dimensional changes in the presence of water or high humidity
  • Maintain performance with repeated sterilization that can include hot water, steam, and harsh cleaning chemicals
  • Good performance in the presence of sudden decompression (i.e., pressure drops over 650 psi)

Recommended Materials for Ball Valve Seats

There are several materials that work well as ball valve seats, including acetal, PEEK, PTFE, TFM, and UHMW-PE.

Acetal Ball Valve Seats

When aggressive environments are involved, Acetal (also known as Delrin) is often used. Acetal provides excellent wear resistance, is very rigid, has good toughness, and is resistant to cold flow. Although its operating temperature range is not very wide (-70°F to 180°F), it can handle pressures up to 5,000 psi. Acetal also works well in radioactive environments  but should not be used with oxygen flow.

PEEK Ball Valve Seats

PEEK offers excellent chemical resistance, very low friction, self-lubrication, and is flame retardant while also possessing a wide operating temperature range (from -70°F to 550°F). It can handle very aggressive applications and works well when there is a need for hot water and steam exposure–but does not do well in the presence of sulfuric acid.

In addition, PEEK is very well adapted to nuclear applications and is available in FDA-approved grades as well as filled grades with improved wear properties and better thermal conductivity. Note that PEEK is usually chosen for ball valve seats when the operating temperature range is outside that of PTFE.

PTFE Ball Valve Seats

PTFE (also known by its trade name, Teflon) has many of the same properties as PEEK, but involves even lower friction, dry running capabilities, and more extensive chemical compatibility. Like PEEK, it is available in FDA-approved grades and can handle cryogenic temperatures down to -50°F and high temperatures up to 550°F as well as pressures up to 5,000 psi.  \

Also like PEEK, PTFE can continue to perform even when repeatedly exposed to hot water and steam. Keep in mind, however, that PTFE does not perform well in the presence of fluorine or alkalies. PTFE is also very easy to clean and available in glass or carbon-reinforced grades that can provide improved wear characteristics, less propensity to cold creep, and lower thermal conductivity. 

TFM Ball Valve Seats

TFM (sometimes referred to by the brand name Dyneon) is a second-generation PTFE material that combines the best properties of PTFE (low friction, chemical resistance, high-temperature performance) with better stress recovery and the ability to handle higher pressures. It is also more elastic and resilient than PTFE. The operating temperature of TFM ranges from -100°F to 450°F and it is well adapted to applications involving steam and thermal fluids.

UHMW-PE Ball Valve Seals

UHMW-PE, which stands for Ultra-High Molecular Weight Polyethylene, has a low coefficient of friction, an operating temperature ranging from -70° F to 200°F, good chemical resistance, good dimensional stability, and good abrasion resistance. In general ball valve seats made from UHMW-PE can handle pressures up to 1,500 psi and can handle low to medium levels of radiation exposure.

Conclusion

Ball valve seals are used in many different industries, including chemical processing plants, oil and gas operations, manufacturing facilities, food preparation, and even residential use. As a leak-proof means of pressure and flow control, their smooth and reliable operation is critical–which is why polymer materials work extremely well for ball valve seats. If you are in the market for a ball valve seat material, contact the experts at Advanced EMC. We can put our years of experience to work for you, helping you select the right material for your project.

 

Most Common Questions about Canted Coil Springs } Advanced EMC Technologies
by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

7 Things to Know About FlexForce Canted Coil Springs

FlexForce canted coil springs have special characteristics that make them useful in a variety of applications, ranging from locking components together in an orthopaedic implant to providing an energizer for mission critical aerospace applicants. In this blog post, we will introduce seven key facts about FlexForce canted coil springs that you need to know.

Are a Specific Design for Springs

Canted coil springs, also known as slant coil or cant coil springs, are springs that have the individual coils set at an angle to each other, rather than having them all parallel. This coil configuration significantly impacts the performance of these springs and makes them ideal for a wide range of uses.

What makes canted coil springs different from other types is the fact that they have a flat load curve when they are compressed. Because of this, canted coil springs generate predictable loads throughout their wide deflection range.

Can be Used as Mechanical Connectors

Canted coil springs are ideal for applications that involve latching, locking, or holding to connect two components (also known as detent mechanisms). Latching involves fastening two parts together so that they can still be disconnected when needed. Locking creates a permanent connection that can only be broken by damaging the sea. Holding, on the other hand, both retains and aligns parts and makes sliding possible via the controlled spring force. 

Canted coils are commonly used to connect two mating surfaces in a highly predictable, repeatable fashion thanks to the flat load curve. When canted coil springs are used, the insertion/removal force can be engineered to a high degree of accuracy.  And when used as a latching, locking, or holding connector, FlexForce canted coil springs provide a lightweight, high strength option that can be used for practically an infinite number of cycles.

Can Provide Exceptional EMI/RF Shielding

One of the common uses of canted coil springs is their ability to effectively provide EMI/RF shielding. Furthermore, the electrical properties of these springs can be customized to provide more optimal shielding against certain ranges of conductive and radiated interference.  

Add to this the fact that they can adapt to irregular and uneven shapes to provide consistent shielding, and it is easy to see why they are a common choice for applications that need to be protected from harmful electromagnetic and radio frequency crosstalk interference.

Can Act as a Multiple Point Electrical Conductor

Some designs depend on multiple electrical contact points, which a canted coil can provide. Using a canted coil spring for electrical connections results in a reliable connection that results in a cooler operation temperature. It allows engineers to manage more power in compact spaces and provides both conducting and grounding capabilities in both static and dynamic applications. In addition, canted coil springs as electrical conductors can perform in some of the harshest operating environments that may involve vibration and shock. It should come as no surprise that canted coil conductors are often used in medical applications inside the human body.

Can be Used with Spring Energized Seals

Canted coil springs work extremely well as the energizer in spring-energized seals. Because of the energizer, spring energized seals are able to maintain contact with the sealing surface, even if issues such as out of roundness, uneven mating surface, runout, hardware gaps, eccentricity, or seal lip wear are present. 

The flat load curve of these springs also means that friction stays fairly consistent in dynamic sealing applications. This makes them ideal for sealing situations that involve critical friction and torque specifications. In addition, canted coil springs are very unlikely to experience compression set. 

Available With a Range of Options

There are several options for canted coil springs. They are available in varying levels of spring force: light, medium, and heavy. And canted coil springs come in both standard and custom sizes. As to the spring wire itself, they are available in wire diameters between 0.25 mm (0.010 inches) and 1.50 mm (0.059 inches). As to the coil width, they come in sizes ranging from 1.5 mm (0.039 inches) and 15 mm (0.591 inches). However, designs can be highly customized if needed.

Finally, the three most common wire materials are Hastelloy, stainless steel (usually 300 series), and copper alloys. For use as a conductor or EMI/RF shielding, stainless steel is recommended. For applications that involve high heat and corrosive media, Hastelloy and Elgiloy may be recommended. Also keep in mind that these canted coil springs can be obtained with nickel, silver, or gold plating.

Used in a Wide Range of Industries and Applications

Canted coil springs are being used in a diverse group of industries and applications, including oil & gas, renewable energy, aerospace, defense, fluid power, transportation, semiconductor manufacturing, and medical devices. 

  • As a mechanical connector, canted coil springs are often used to lock together frame assembly of a ventilator cart or to hold components together in wind turbines.
  • As a multiple contact point conductor, canted coil spring assemblies are often used in active implantables such as pacemakers or neurotransmitters. 
  • As EMI/RF shielding, canted coil springs can be found in electrical enclosures or used with data transmission cables.
  • As a part of a spring energized seal, canted coil springs are used in critical aerospace applications and dangerous petrochemical environments involving extreme heat and corrosive materials.

Conclusion

FlexForce canted coil springs can be used as detent mechanisms, EMI/RF shields, multipoint electrical conductors, and energizing springs in seals. They are available in a number of options and can be fully customized to meet user needs. In addition, their reliable performance has already been proven in number industries and applications. If you are interested in FlexForce canted coil springs, contact us at Advanced EMC today.