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.

by Denise Sullivan Denise Sullivan No Comments

5 Common reasons of Valve Seat Failure

valve seat failure

 

Valve seat failure can lead to costly and time-consuming issues. Under certain circumstances, a ball valve seat failure can cause explosions and lead to life-threatening situations. In this article, we will cover the top five causes of failure.

Material Choice

The material choice of the valve seat can contribute to valve seat problems if you pick the wrong option. Different materials work in different operating conditions, so you want to ensure that you research the material carefully before choosing.

The most common material options are 

  • PEEK
  • PTFE
  • TFM
  • PCTFE
  • Acetal
  • Vespel

The wrong material can cause unexpected issues that may damage the hardware of mating components or even physical injury.

Cold Flow

While PTFE, or Teflon, is a common material in valve seats, there could be some cold flow resistance issues. Cold flow is the process when solid material slowly deforms under the influence of long-term mechanical stress.

The cold flow of material during us and cycling causes a slow deterioration in valve performance. Despite cold flow issues, PTFE is still the best choice in many industries. Choose a filled PTFE instead of virgin PTFE to mitigate complications from cold flow. Filled is less susceptible to stress and has better resistance to cold flow.

Excessive Friction

Excessive friction can also cause valve seat issues. Excessive circumferential seal force accelerates wear on the valve, which leads to an increase in torque requirements. The friction between the ball and the valve seat affects how much torque is necessary to turn the ball valve. 

 When the temperature in the valve increases, the pressure between the valve seat and the ball increases. Increased temperature creates greater friction between the valve ball and the seat. 

Eventually, the valve can become locked either open or closed. As the required torque increases, the valve seat is torn apart, and mechanical failure occurs.

Valve Seat Failure: Seat and Seat Carrier Design

The valve seat is one of the most critical components. However, poor seat design can lead to a shortened lifespan, leakage, or catastrophic failure. The catastrophic failure could lead to explosions or life-threatening damage in particular environments.

Soft seat valves typically use metallic seat carriers with the valve seats pressed into them. As with the seat design, the seat carrier design can have similar problems. If the seat carrier design is slightly off, it could make it difficult to determine where the problem lies.

Permanent Deformation

In high-pressure applications, the valve setting of soft seats is necessary. To correctly set soft seals, the valve is repeatedly actuated during part of the build process. This repeated actuation can cause permanent deformation during normal use.

A failure to understand the initial deformation will cause the valve to fail. It won’t fail on initial use, but it will eventually stop working, and the valve will either need to be rebuilt or replaced as a result.

Valve Seat Failure Conclusion

Whether your valve requires PTFE, PEEK, or any other material, you want to ensure you get the appropriate material for your valve seat. Incorrect materials and excessive friction, seat design malfunctions, and permanent deformations can cause failures. 

Contact us today to learn more about the valve seats we offer and assist you in finding the appropriate material for your applications.

 

by Denise Sullivan Denise Sullivan No Comments

Virgin Teflon Balls vs. Glass-filled Teflon Balls: What You Need to Know

virgin teflon balls

At first glance, it might appear that the Teflon Balls are the same as the glass-filled ones. However, closer inspection reveals that the two materials have very different properties. Both virgin Teflon balls and glass-filled Teflon balls have unique properties, making them ideal for different applications.

This article will explore the differences between virgin and glass-filled Teflon balls.

Virgin Teflon Balls

Virgin Teflon balls can be either hollow or solid. Both offer the benefits of being lightweight and ideal for light load-bearing applications. These balls do not require lubrication and, unlike metal balls, are not magnetic and provide heat and electrical insulation.

The strengths of virgin Teflon balls include:

  • Weathering resistance
  • Solid PTFE balls are resistant to corrosion
  • Chemically resistant to all common solvents
  • Thermal resistance
  • Low smoke and toxic gas emissions
  • Abrasion, fatigue, and radiation resistant
  • Can be used in extreme conditions

 Applications

There are several applications in which virgin Teflon balls are the ideal choice. As it is ideal for light load-bearing applications, it is ideal in pump and valve components. Thanks to its electrical insulation properties, it is often used in electrical components.

Other applications where virgin Teflon balls are used include:

  • Sealing
  • Bushing
  • Food processing 
  • Medical device components

Properties

Virgin Teflon balls are generally white or off-white in color. In their natural state, Teflon balls are heavier than water. Other properties include 

 

Properties Unit Method Typical Value
PHYSICAL
Density g/cm3 ASTM D792 2.14-2.18
Hardness points ASTM D2240 51-60
Tensile Strength MPa ISO 527 ≥ 20
Elongate at Break % ISO 527 ≥ 200
Compressive strength at 1% deformation psi ASTM D695 580-725
Impact strength Izod J/m ASTM D256 153
TRIBOLOGICAL
Dynamic Coefficient of Friction / ASTM D1894
ASTM D3702		 0.06
Wear Factor K / ASTM D3702 2.900
PV limit at 3 m/min

             at 30 m/min

             at  300m/min

 N/mm2 * m/min / 2.4

4.2

5.7
THERMAL
Service Temperature °F / -328/+500
Thermal expansion coefficient (linear) 25-100°C 10-5 in/in/°F ASTM D696 6.625-7.206
ELECTRICAL
Dielectric strength  (specimen 0.5mm thick) KV/mm ASTM D149 ≥ 40
Dielectric Constat at 60 Hz and 106 Hz / ASTM D150 2.05-2.10
Volume Resistivity Ω * cm ASTM D257 1018
Surface Resistivity Ω ASTM D257 1017

 

Glass-Filled Teflon Balls

Glass is one of the most common fillers in filled Teflon balls. The filling typically ranges from 5 to 40%. Typically glass-filled Teflon balls are used instead of virgin Teflon balls because these components are stronger, and their compression and wear properties are an improvement.

The strengths of glass-filled Teflon balls include

  • Improved resistance to wear over standard solid PTFE balls
  • Resistant to oxidation and acid
  • High hardness rating
  • High maximum operating temperature
  • Increased compressive strength
  • Low coefficient of friction
  • HIgh UV Light resistance
  • Lower thermal expansion
  • Lower deformation under load

Applications

As with virgin Teflon balls, glass-filled PTFE can be used in many different fields. Some of the more common applications include

  • Petrochemical application
  • Commercial application
  • High-load industrial applications
  • Material handling
  • Precision part manufacturing 
  • Chemical engineering applications

Properties

The properties of glass-filled, carbon-filled, stainless steel, and bronze vary slightly. Understanding the difference will help you know which product is the best choice for each application.

For 25% glass-filled Teflon balls, typical properties include:

Properties Unit Method Typical Value
PHYSICAL
Density g/cm3

lb/in3

 ASTM D792

ASTM D792

 2.25

0.081
Hardness / ASTM D785 Shore D60
Tensile Strength psi ASTM D638 2100
Elongate at Break % ASTM D638 270
Compressive strength  psi ASTM D695 1000
Flexural strength psi ASTM D790 1950
TRIBIOLOGICAL
Dynamic Coefficient of Friction / ASTM D1894

 0.5
Static Coefficient of Friction / ASTM D1894 0.12
THERMAL
Maximum Continuous Operating Temperature °F

°C

 / 260

500
Minimum Continuous Operating Temperature °F

°C

 / -200

-328
Melting Point Temperature °F

°C

 ASTM D3418

ASTM D3418

 635

335
Thermal expansion coefficient (linear) 25-100°C 10-5 in/in/°F ASTM D696 6.4
ELECTRICAL
Dielectric fACTOR AT 1MHz / ASTM D150 2.4
Dielectric Constant at 1 MHz / ASTM D150 0.05
Surface Resistivity Ω * cm ASTM D257 >105

 

15% glass-filled Teflon balls properties are:

Properties Unit Method Typical Value
PHYSICAL
Density g/cm3

lb/in3

 ASTM D792

ASTM D792

 2.15-2.25

0.0777-0.0813
Hardness / ASTM D2240 60-64
Tensile Strength psi ASTM D638 2490-3700
Elongate at Break % ASTM D638 250-280
Compressive strength  psi ASTM D695 853-925
Impact strength Izod J/m ASTM D256 14.0-15.5
TRIBIOLOGICAL
Dynamic Coefficient of Friction / ASTM D1894

 0.060
Static Coefficient of Friction / ASTM D1894 0.050
THERMAL
Maximum Continuous Operating Temperature °F

°C

 / 518

270
Minimum Continous Operating Temperature °F

°C

 / -436

-260
Thermal expansion coefficient (linear) 25-100°C 10-5 in/in/°F ASTM D696 8.9-12.7
ELECTRICAL
Dielectric factor at 1MHz kV/mm ASTM D149 16.0-19.0
Dielectric Constant at 1 MHz / ASTM D150 2.3-2.5
Surface Resistivity Ω * cm ASTM D257 >1015

 

10% carbon filled

Properties Unit Method Typical Value
PHYSICAL
Density g/cm3

lb/in3

 ASTM D792

ASTM D792

 2.25

0.081
Hardness / ASTM D785 63
Tensile Strength MPa ASTM D1457 15
Elongate at Break % ASTM D1457 180
Compressive strength  MPa ASTM D695 100
TRIBIOLOGICAL
Dynamic Coefficient of Friction / ASTM D1894

 0.12-0.14
Static Coefficient of Friction / ASTM D1894 0.14-0.16
THERMAL
Maximum Continuous Operating Temperature °F

°C

 / 260

500
Minimum Continuous Operating Temperature °F

°C

 / -200

-328
Melting Point Temperature °F

°C

 ASTM D3418

ASTM D3418

 635

335
Thermal expansion coefficient (linear) 25-100°C 10-5 in/in/°F ASTM D696 9.5 x 10-5
ELECTRICAL
Dielectric factor at 1MHz / ASTM D150 –
Dielectric Constant at 1 MHz / ASTM D150 –
Surface Resistivity Ω * cm ASTM D257 >103

 

Bronze filled (40%) PTFE balls have a specific gravity of 3.0-3.12g/cm3 and a tensile strength of 22-27 Mpa, with a hardness of 65-68. Stainless steel-filled PTFE has a specific gravity of 3.35 g/cm3, a tensile strength of 22 Mpa, and a harness of 65-69.

Which Is Best?

Both virgin and glass-filled Teflon balls have their benefits. The ultimate choice of which ball you should use depends on the environment you are working in and your basic equipment needs.

Ready to learn more? Contact us today to learn about the types of Teflon balls we offer and which choice best meets your needs.

 

by Denise Sullivan Denise Sullivan No Comments

High Performance Electric Vehicle Seals

electric vehicle seals

 

There is a push for more people to drive electric vehicles. While they are more environmentally friendly, the motors differ significantly from traditional combustion engines. Electric vehicle seals must keep lubrication confined to the gearbox, dirt, and debris out of the motor while providing engine efficiency.

In this article, you will gain a basic understanding of

  • How electric vehicles and internal combustion engines differ
  • Design considerations for electric vehicle seals
  • Types of materials used in making seals for electric vehicles

Differences in Electric Vehicle and Internal Combustion Engines

If you are standing outside an electric vehicle looking at it, you may not notice many differences between it and a gas-powered automobile. The overall external design is the same, except the electric car has no exhaust pipe.

However, below the surface, the two engines are significantly different. Gas-powered have a gas tank, gas pump, motor, carburetor, alternator, smog controls, and hundreds of other moving parts. In addition, the engine requires seals to keep oil and other fluids from leaking out. 

An electric vehicle engine only has one main moving part: the motor. Despite the motor being in a dry environment, seals are still required to help keep dirt and dust out of the engine and the lubricants needed for the vehicle gearbox. 

Both electric vehicles and internal combustion engines require specialized seals to keep the motors/engines working efficiently.

Electric Vehicle Seal Design Considerations

Electric vehicle motors work more efficiently and require seals that can handle their unique needs. The seals used in electric vehicles often exceed the minimum requirements of seals found in internal combustion engines. In addition, many of them must work in dry environments.

Friction

Friction is one of the primary design considerations for electrical vehicle seals. While friction in any engine is not desired, electric vehicles need a lower friction seal than traditional gas-powered engines. Any friction created by seals causes efficiency loss in power output. 

If the engine isn’t efficient, the battery won’t be able to have the range that it should. A motor working harder to make up for the efficiency loss won’t be able to travel as far as it should. Lower friction is essential to gain better efficiency and long distance. 

Dry Running

Electric vehicles require both dynamic and static seals. The dynamic seals are often called rotary lip seals.  While they don’t require oil seals, electric motors need seals that work in a dry-running environment. 

The primary shaft uses a rotary seal to prevent dirt, dust, and water from entering the electric motor. If fluid and debris enter the motor, it can damage the engine and cause it to break down or damage some of the highly charged electrical components so that it won’t work efficiently.

In addition to running in a dry environment, the rotary seals must withstand the higher speeds electric motors run. The components spin up to 18,000 rpm, about three times faster than a traditional combustion engine. As a result, seals in these engines have to withstand high-speed running without lubrication.

Electric Vehicle Seal Materials

Not all materials common seal materials work well in electric vehicles. However, two of the more common types are PTFE and molded rubber. The materials are used for different applications but are necessary as part of the vehicle’s makeup.

PTFE Seals

Polytetrafluoroethylene (PTFE), more commonly known as Teflon, is a nonreactive material with a low coefficient of friction. Therefore, it is ideal for high-temperature environments found in an electric vehicle motor.

Seals made from PTFE are usually found on the e-axle and help to act as a barrier between the motor and gearbox. The engine is a dry environment, while the gearbox requires lubrication. The PTFE seal keeps lubricant from seeping into the motor. In addition, the seal’s dry side has a lip that keeps dust and dirt out of the engine.

In addition to keeping the lubricant in the gearbox and dirt out of the motor, the PTFE rotary seal can withstand the high speeds in the car’s engine. Additionally, it provides low friction to keep the motor running efficiently.

Molded Rubber

While PTFE is the ideal seal material for the e-axle, molded plastic is the perfect solution for valve housing. The valve housing needs a seal that will withstand high temperatures and pressure in the area. The T-junction area of the seal is the most problematic area known for failure. 

Molded rubber seals are push-in-place rubber gaskets that perform well under pulsating pressure. These gaskets can handle temperatures of up to 302°F (150°C) and 50 Bar pressure. In addition, it requires more gland space than seals used in a traditional combustion engine.

Conclusion

Electric vehicles are rising in popularity. However, due to the nature of their engines, they require different seals than a traditional combustion engine. These seals need to have lower friction and handle high-speed rotation.

Need seals for your electric vehicle manufacturing? Contact us today to find out how we can create custom seals for your project.

by Bill Vardeman Bill Vardeman No Comments

Understanding FEP Encapsulated Helical Springs

 

FEP encapsulated helical spring seals are approved for cryogenic and FDA use.

Fluorinated ethylene propylene (FEP) is one of the most popular jackets for encapsulated rings used in cryogenic, corrosive environments, and even FDA-approved food grades. It is well-known by many of the trade names Teflon FEP, Neoflon FEP, and Dyneon FEP. FEP encapsulated helical springs are one type of these seals.

Let’s take a closer look at what an FEP encapsulated helical spring is, the properties of these seals, and the benefits of using them.

What is an FEP Encapsulated Helical Spring

FEP Helical spring seals are created from helical springs. These are elastic coiled mechanical devices. Most consumers are used to seeing helical springs in equipment and devices that store and release energy.

A helical spring seal provides sealing solutions for industries operating in extreme conditions. These seals provide a gas-tight sealing system that meets environmental regulations and reduce fugitive emissions.

FEP encapsulated helical springs seals are housed within a durable, chemical jacket made from fluorinated ethylene propylene. The FEP jacket allows the spring seal to work in chemically corrosive environments or extreme temperatures. 

What are the Properties of FEP Encapsulated Springs

FEP encapsulated helical spring seals’ properties make them ideal for use in extreme conditions. A wide variety of industries can use these spring seals to meet their needs. 

Property Test Method Units Results
Encapsulation Max Service Temperature 8,000-hour aging tests °C / °F 204 / 400
Encapsulation Tear Strength ASTM D1004 (Initial) N / Kg 2.65 / 0.270
Encapsulation Tensile Strength ASTM D638
@ 24°C / 75°F		 PSI / Bar / MPa 3,400 / 234 / 23.0
Encapsulation Impact Strength ASTM D256
@ 24°C / 75°F		 J/m2 No Break
Encapsulation Hardness ASTM D2240 Shore 56
Encapsulation Specific Gravity ASTM D792 g/cm3 2.15
Encapsulation % Elongation @ Break ASTM D638
@ 24 °C / 75°F		 % 325
Encapsulation Flex Modulus ASTM D790 PSI / Bar / MPa 85,000/5,860 / 586
Encapsulation folding Endurance ASTM D 2176 Cycles 100,000
Encapsulation Ignition Temperature Vul045 °C / °F ≥530 / ≥986
Encapsulation Color Visual N/A Off Clear
Moisture Absorption Vul046a % <0.01

 

Advantages of FEP Encapsulated Spring Seals

FEP encapsulated spring seals have many advantages for industrial settings such as cryogenics, aerospace, and oil. It has some of the same advantages as using PFA encapsulated seals.

FEP encapsulated helical spring seals’ properties make them ideal for use in extreme conditions. A wide variety of industries can use these spring seals to meet their needs. 

The FEP jacket protects from corrosive chemicals. FEP has an excellent resistance rating for several chemicals, including the following.

  • Gasoline
  • Hydrochloric Acid (1-5, 20, and 30%)
  • Isobutyl Alcohol
  • Isopropyl Alcohol
  • Propane Gas
  • Sulfuric Acid ( 1-6, 20, 60, and 98%)
  • Sulfuric Hydroxide (1 and 50%)

FEP also has a wide operating range. It works in a temperature range of -420°F (-251°C) to 400°F (204°C). At cryogenic temperatures, FEP encapsulated helical springs remain flexible. This flexibility makes it preferable to O-rings in a cryogenic environment. 

The FEP encapsulated helical springs have low friction. It gives them a minimal stick-slip behavior. A low compression set allows the seal to return to its original shape after deformation.

Best FEP Encapsulated Helical Springs

FEP encapsulated helical seals have several advantages in cryogenic and corrosive environments. They withstand temperatures as low as -251°C (-420°F) and are flexible even at low temperatures. 

Advanced-EMC will work with you to find the encapsulated helical spring solution your application needs, from FDA-approved solutions for use with food processing equipment or a reliable, cryogenically compatible solution for a rocket. Contact us today to learn more.

FAQ

Is FEP silicone?

No, FEP stands for fluorinated ethylene propylene. A Teflon coating protects the seal from hazardous conditions such as extreme temperatures and chemical environments. FEP can encase silicone rings, but it is not silicone itself.

Is FEP the same as PTFE?

No, while both are Teflon substances, there are several key differences. FEP is better with gas and vapor permeability, while PTFE has a lower coefficient of friction. 

 

by Jackie Johnson Jackie Johnson No Comments

Guide to Cryogenic Seals for Marine Loading Arms

cryogenic seals for marine loading arms

A marine loading arm is a flexible, mechanical arm that assists with loading or unloading ships. Typically, they transport petroleum and other chemicals between vessels and containers at the docks. 

Marine loading arms are an alternative to using direct hookups. Like direct connections, you must completely drain the loading arms before breaking off the links by either using high-pressure air to blow out traces or stripping the line using a pump.

Due to what these loading arms carry, they can operate at cryogenic temperatures. Choosing the appropriate seals for this use is essential to ensure the safety of operators and machines alike. Let’s look further into cryogenic seals for marine loading arms.

Why Use Cryogenic Temperatures

Some liquids are too volatile to transport naturally. That is why they are cryogenically cooled into their liquid form. Cooling the air to cryogenic temperatures requires a process of compression, cooling, and expansion.

Moving cryogenic liquids instead of gas is safer and less likely to explode or cause a fire in the event of an accident. However, as these liquids are at sub-zero temperatures, you should use protective equipment when handling them.

There are many types of gasses transported using cryogenic temperatures. The most common use of marine loading arms to load onto ships include liquified petroleum gas, liquified natural gas, liquid oxygen, liquid nitrogen, liquid hydrogen, and liquid helium. The table below shows at what temperatures these gasses are transported.

 

Gas Temperature °C Temperature °F
Liquified Petroleum Gas -48°C -54.4°F
Natural Gas -162°C -259.6°F
Liquid Oxygen -182°C -295.6
Liquid Nitrogen -196°C -320.8°F
Liquid Hydrogen -253°C -423.4°F
Liquid Helium -269°C -452.2°F

 

Cryogenic Seal For Marine Loading Arms Design Consideration

The most common cryogenic loading arm seals are a polymer material that has a metallic energizer. These materials include

  • PTFE
  • PCTFE
  • TFM
  • UHMW PE

PTFE is often the first choice because it is compatible with a wide range of chemicals, has an extremely low coefficient of friction, and is thermally stable. Another valuable material for cryogenic seals is Torlon® Polyamide-imide. Torlon PAI is rigid even at cryogenic temperatures. 

These materials have excellent chemical compatibility, low friction, dry-running, and good dimensional stability. Dimensional changes can be accounted for using a spring-energized seal or sizing the seal by accounting for plastic’s coefficient of thermal expansion. 

Cryogenic seals made with PTFE, and its variants, offer a high strength-to-weight ratio, excellent durability, and self-lubricating properties.

What Cryogenic Seals Materials to Avoid

Traditional compression seals are not a viable choice for cryogenic use. Natural rubber, silicone, Buna-N, fluorocarbon, and ethylene-propylene can handle sub-zero temperatures. However, they cannot correctly seal at cryogenic temperatures. Temperatures below -32°C (-25.6°F) cause the rubber to become brittle.

If you use an inappropriate seal, it will eventually fail. Upon failure, the hazardous liquids flowing through the marine loading arm will escape and can be life-threatening. Some dangers include explosion, fire, asphyxiation, or frostbite.

In addition, there will be dimensional changes between when the seal is installed and when it experiences cryogenic operating conditions. You must ensure that the chosen polymer or elastomer doesn’t become brittle at the cryogenic temperatures involved.

Cryogenic Seal Maintenance Considerations

Periodically, cryogenic seals will require maintenance and replacement. Some things to ensure a longer seal life include understanding conditions, knowing what the seal can withstand, and knowing what to look for when it comes to wearing and lubricating.

Understand Conditions 

The conditions in which your marine loading arm works will affect the seals. Temperature, movement, and pressure will eventually cause the seal to wear out and increase leak rates.  If you know and understand the exact conditions where the seals will work, you can pick the suitable material for longer-lasting usage.

Knowing What the Seal Can Withstand

All seals have a limit to what they can withstand. Cryogenic seals can withstand temperatures from -269°C (452.2°F) to 148°C (300°F). They can typically withstand chemicals, natural gas, petroleum, and liquid nitrogen. They can also withstand high-pressure conditions.

Know What to Look for When it Comes to Wear

All seals wear out. Eventually, cryogenic seals are not excluded. Seals begin to wear on the seal face, causing a leak. You should inspect seals regularly for signs of distress, such as chips and grooves. If there are any indications of wear, then you should replace the seal immediately.

Lubricate

The cryogenic fluids themselves usually make for poor lubricators.  Any added lubricants or even moisture can freeze onto the face of the seal, causing the seal to shatter or, worse yet, the system to lock up and experience catastrophic damage.  However, not using lubrication can result in issues like slip-stick vibration.  

Lubricating cryogenic seals is virtually impossible. As a result, using unfilled polymer materials or a modified material may be the only option.

Best Cryogenic Seals for Marine Loading Arms

Choosing the best cryogenic seals for marine loading arms will depend on what you are transporting. Most cryogenic seals will work in marine loading arms, but some materials work better than others. The most common materials are PTFE, PCTFE, TFM, and UHMW PE.

Advanced EMC offers a wide array of cryogenic seals. If you are interested in purchasing cryogenic seals, contact us today!

 

FAQ

How do you seal liquid nitrogen?

Sealing liquid nitrogen requires either silicone or PTFE seals. If the seal comes into contact with the liquid nitrogen, PTFE seals are the better choice as this material can handle cold flow without causing creep.

What is the purpose of marine loading arms?

Marine loading arms load or unload vessels carrying petroleum products. They are made of several sections of pipes connected by quick-connect fittings and swivel joints. Cryogenic seals are used between the fittings and joints when transporting liquid nitrogen, liquid petroleum, or any other liquid stored at cryogenic temperatures.

 

Food Processing and PTFE Spring-Energized Seals
by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

PTFE + Spring-Energized Seals: A Reliable Solution for Food and Pharmaceutical Processing

The primary challenge in specifying a seal is finding a solution that achieves consistent seal integrity for the operating conditions involved. However, when food or pharmaceuticals are involved, additional challenges arise — and can be met using PTFE spring-energized seals.

Design Concerns for Food and Pharmaceutical Seals

There are a number of critical design considerations involved with any type of sealing application, such as operating temperature, pressure, velocity, wear rate, friction, and chemical compatibility.

When food, dairy, or pharmaceuticals are involved, however, there are additional criteria. The first of these is finding a material that is compliant with relevant standards. In the United States, the main standard is the Food and Drug Administration standard FDA 21 CFR Part 177. This standard covers indirect food additives and thus applies to seals. For a material to be considered FDA compliant, it must be safe for human consumption and chemically inert.

Another potential challenge related to food and pharmaceuticals is MRO (Maintenance, Repair, and Operations): 3-A (Dairy and Milk) sanitary standards 18-03 for rubber materials and 20-27 for polymers, as well as NSF (National Sanitation Foundation) sanitary practice standards such as NSF/ANSI 2-2021. Such standards and practices deal with CIP (Clean-In-Place) and SIP (Sanitize-In-Place).  CIP/SIP processes often involve …

  • Extremely high temperatures, which can affect seal integrity and dimensional stability if the right material is not selected
  • Exposure to hot water and steam, which can prove problematic for materials that have a significant water absorption rate
  • Aggressive media, which can permanently compromise seal integrity if the jacket material is not compatible with the cleaning media

Wear resistance is also a critical factor: as the seal begins to wear, its particles become a potential source of contamination. This is particularly problematic when food, dairy, beverage, or pharmaceuticals are involved because those wear particles will likely be ingested. The seal material must, therefore, have a low rate of wear and be safe for occasional ingestion.

Extreme temperatures are often involved and can range from cryogenic (where elastomers and polymers may develop brittle behavior) to extreme heat (where the strength and stiffness of the seal material may be significantly reduced). Seal materials for food and pharmaceutical applications may experience both temperature extremes during regular operation, which may involve the CIP/SIP procedures discussed earlier.

Lubrication is also a major design choice for food and pharmaceutical sealing solutions. But, again, contamination must be considered and the chances are not good when it comes to finding a food-safe lubricant that is compatible with the sealing material and provides the necessary reduction in friction. A better solution would be a material with an extremely low coefficient of friction that is also self-lubricating.

Finally, any application involving food, beverages, or pharmaceuticals must have highly reliable seals. A seal failure can result in ruined products, dangerous contamination, and the potential for lawsuits.

PTFE Spring-Energized Seals

One highly reliable solution for food, dairy, and pharmaceutical applications is spring-energized PTFE seals. Spring-energized seals include an energizer that maintains seal integrity during …

  • Extreme temperatures and temperature variation, including temperatures related to CIP/SIP processes
  • Changes in pressure as well as reliable performance over a range of pressures (including vacuum conditions)
  • Seal or shaft wear
  • Shaft misalignment, eccentricity, or dimensional changes

In addition, spring-energizers add permanent resilience to the seal jacket — and an excellent option for the seal jacket is PTFE.

Virgin PTFE (also referred to as unfilled PTFE) is both FDA and USDA approved. PTFE also provides excellent high-temperature performance, experiences no water absorption, and is extremely chemically inert, all of which combine to give it the ability to maintain seal integrity during the most aggressive CIP/SIP procedures. In addition, PTFE is hydrophobic, thus repelling water and making it even easier to keep clean.

PTFE also exhibits good wear resistance, and what wear the seal jacket does experience will be compensated for by the spring energizer. And virgin PTFE provides excellent performance over a range of temperatures, from cryogenic -450°F to high temperatures up to 450°F. PTFE also has the lowest coefficient of friction of any solid at 0.1. Furthermore, it does not require lubrication because it is self-lubricating.

Conclusion

PTFE spring-energized seals are an excellent solution to the sealing challenges of food, dairy, beverage, and pharmaceutical processing. Combining the outstanding properties of FDA-approved virgin PTFE with the reliability and integrity of spring-energizers leads to high integrity and consistent sealing even in aggressive or extreme operating conditions.

If you are looking for seals related to food or drug processing, contact Advanced EMC today. Our sealing solution experts will work with you to find the right type of spring-energized seal for your application, including everything from the seal jacket geometry to the spring material and configuration.

Benefits of PTFE for Sealing Applications
by Jackie Johnson Jackie Johnson No Comments

Benefits of PTFE For Sealing Applications

PTFE (Polytetrafluoroethylene), also known by its trade name Teflon, is a polymer material commonly used in sealing applications that offers unparalleled stability and sealing characteristics across an extremely wide range of temperatures, from the extreme heat of a space shuttle engine to the cryogenically cold temperatures used to preserve

In this article, we will discuss how and why PTFE is one of the best materials to use for seals in a wide variety of applications.

Low Friction

PTFE has the highest melting point and lowest friction, and is the most inert of all the fluoropolymers. It has a continuous service temperature rating of 500 degrees Fahrenheit. Molding powders are excellent, fine cut granular resins, well suited for a variety of demanding chemical, mechanical, electrical and non-stick surface applications.

Such applications include:

  • Cookware
  • Outdoor Rain Gear
  • Medical Devices
  • And more!

Cryogenic Applications

Cryogenic seals are used with super-cooled media, like liquid hydrogen or compressed natural gas, at temperatures below -238°F and down to -460°F (absolute zero). Cold temperatures like this are rough on a seal because at these temperatures most materials begin to exhibit highly brittle behavior and lubricants typically cannot be used because they will freeze. PTFE seals, however, can handle temperatures all the way down to -450°F and are capable of dry running because of their extremely low friction. PTFE cryogenic seals are used in industries like oil & gas, pharmaceuticals, and aerospace.

High Temperature Applications

PTFE seals work well at the other end of the spectrum, too. They can continue to function in extreme temperatures up to 600°F, and continuous operating temperatures up to 600°F. Note that a filler may be required to enable the PTFE to dissipate heat more quickly. It’s not uncommon to see PTFE seals in petroleum or steam applications where temperatures greatly exceed 200°F.

PTFE is also non-flammable, making it ideal for use in applications such as jet propulsion engines. Where other materials would simply melt under the pressure of constant exposure to high temperature flames, PTFE is built to withstand even the hottest of environments.

The use of seals for high temperature applications include oil and gas industry and aerospace, to name a few.

Chemical Applications

The chemical resistance of PTFE is some of the best on the market. It is stable in most aggressive and corrosive media, including:

  • Acetone
  • Chloroform
  • Citric Acid
  • Hydrochloric Acid
  • Sulfuric Acid
  • Tallow
  • Sodium Peroxide
  • And more!

However, it should be pointed that that PTFE is not chemically resistive to liquid or dissolved alkali metals, fluorines and other extremely potent oxidizers, as well as fluorine gas and similar compounds. Outside of those, PTFE is an excellent choice for applications involving chemicals.

Oil and Gas Industry

Seals are critical for the safe and reliable operation of oil rigs across the globe. Not only do seals need to be able to withstand a wide variety of extreme temperatures, but they need to be able to handle extreme pressures as well. For well drilling, for example, seals need to handle pressures from 345 to 2070 bar (5000 to 30000 psi).

For those reasons, PTFE is an incredibly popular material to make oil and gas seals out of. Because of it’s resistance to heat, cold and high pressure, PTFE can withstand the rigors of oil and gas unlike any other material.

Spring-energized Seals

In order to retain sealing power under extreme temperatures, many engineers and designers go with spring-energized PTFE seals. The spring provides optimal sealing by forcing the lip of the seal against the mating surface and helps to account for dimensional changes as a result of temperature fluctuations.

A highly efficient seal is created as the system pressure increases enough to take over from the spring and engage the shaft or bore. The spring or energized seal assembly provides permanent resilience to the seal jacket and compensates for jacket wear, hardware misalignment and eccentricity. The jacket material is critical in design to assure proper seal performance.

Rotary Shaft Seals

Using PTFE in rotary shaft seals allows them to be able to run at higher pressures and velocities when compared to other materials. They are also able to have tighter sealing, often exceeding 35 BAR and can run at far more extreme temperatures ranging from -64 degrees Fahrenheit (-53 degrees Celsius) to 450 degrees Fahrenheit (232 degrees Celsius).

On top of that, they are:

  • Inert to most chemicals
  • Can withstand speeds up to 35 m/s
  • Compatible with most lubricants
  • Come in a wide range of sizes
  • And more!

Conclusion

PTFE is an ideal sealing material for both extremely high temperature applications and demanding cryogenic applications. It retains its key sealing properties: stiffness, strength, dimensional stability (may require spring energizer), low friction, and chemical compatibility- even in the most aggressive operating conditions.

Need PTFE sealing solutions? Advanced EMC Technologies is the leading provider of PTFE spring energized and rotary shaft seals in the US. Contact us today!

FEP Encapsulated O-Rings | Advanced EMC Technologies
by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

FEP Encapsulated O-Rings

FEP encapsulated o-rings can survive corrosive chemicals and retain their sealing power in extreme temperatures, which is the main reason more and more engineers are choosing them for harsh environment applications. But what makes these particular o-rings special and what options are available for them?

What Makes Encapsulated O-Rings Different?

Unlike traditional o-rings, encapsulated o-rings contain a solid or hollow core that is typically made from a very elastomeric material. The exterior of the encapsulated o-ring is able to protect the encased elastomer from corrosive media that would adversely affect its performance. Together, the core and encapsulating polymer are able to provide a highly reliable seal even in extremely harsh conditions that may involve aggressive chemicals, extreme temperatures, and high pressures.

Encapsulated o-rings can be used in a wide variety of applications, including flanges, swivels, joints, valve stems, pumps, and even rocket engines. They serve as an excellent replacement for solid PTFE o-rings that are just not flexible enough for sealing in the long term. 

Characteristics of FEP

One of the most popular materials for the jacket of an encapsulated o-ring is FEP (fluorinated ethylene propylene), which has several trade names including Teflon FEP, Neoflon FEP, and Dyneon FEP. It is well known for its resistance to chemical attack, low friction, and a wide operating temperature range of -420°F through 400°F.  FEP remains flexible even at cryogenic temperatures, as well. One of its key characteristics is a very low compression set, allowing it to return to its original shape after deformation. FEP is also non-flammable and easy to lubricate.

While FEP is often compared to PTFE (Teflon), there are several key differences to keep in mind. For example, it does have a low coefficient of friction but it is higher than PTFE; at the same time, it still possesses very low friction with minimal stick-slip behavior. In addition, FEP does exhibit better vapor and gas permeability, which could be key for some applications. It is also melt processable, which means it can be vacuum formed, injection molded, and extruded. And, like PTFE, it is easy to clean even viscous liquids from.

FEP is available in FDA-approved grades, is considered a high purity material, and is less expensive than PFA, another commonly used jacket material. Note that FEP is commonly used in applications such as pump housings, medical components, food processing, fluid handling, and chemical processing.

Recommended Cores for FEP

FEP encapsulated o-rings work especially well with FKM and silicone cores, but there are other options available. FKM, which is a fluro-elastomer, has rubber-elastic properties which allow it to reassume its original shape and form after deformation. This results in excellent properties related to compression set. Silicone cores are not as stiff or hard as FKM cores and exhibit very good flexibility, even in cold temperatures. When combined with a hollow core geometry, this additional flexibility means that less energy is needed to achieve a tight seal. They work best for applications that involve low compressive forces.

Cores made from stainless steel, such as SS 301 or 302, exhibit excellent performance at both cryogenic and high temperatures, ranging from -420°F to 500°F. These cores usually take the form of a spiral spring (not unlike spring-energized seals) and exhibit minimum compression set and good resilience. They are not commonly used with FEP, however. EPDM, which stands for ethylene propylene diene monomer, is a synthetic rubber that performs well in temperatures ranging from -58°F to 300°F. Again, this particular core material is not recommended for use with FEP.

Selecting an FEP Encapsulated O-Ring

First, there are limitations associated with FEP encapsulated o-rings. They should not be used with liquid alkali metals and some fluorine  compounds, and should not be exposed to abrasive media such as slurries and some powders. 

They are not suitable for applications that involve high pressures and are limited to static or slow moving applications. In addition, they are not recommended for applications where the o-ring will be highly elongated and end-users should be aware that installation forces will be higher for FEP encapsulated o-rings.

However, experts agree that chemical attack and swelling are among the most common causes of o-ring failure, and the use of FEP encapsulated o-rings can solve both of these issues. FEP with an FKM core is a standard solution with a low compression set, recommended for operating temperature ranges not exceeding -4°F to 401°F. 

Use of a solid silicone core results in better low temperature performance, with an operating temperature range of -46°F to 401°F. A hollow core, on the other hand, involves lower contact pressures and is ideal for sensitive or fragile equipment. 

Conclusion

FEP encapsulated o-rings involve several key advantages, starting with their excellent chemical resistance, which allows them to be used with corrosive chemicals. These o-rings can handle pressures up to 3,000 psi and provide both an excellent service life and reliable sealing, all at a cost effective price. Their reliability and durability also translate to less downtime and better M&O costs. If corrosive media or extreme temperatures are destroying your o-rings, it may be time to consider an FEP encapsulated solution.

Advanced-EMC will work with you to find the encapsulated o-ring solution your application needs, from FDA-approved solutions for use with food processing equipment or a reliable, cryogenically compatible solution for a rocket. Contact us today to learn more.