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.
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.
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.
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.
Teflon (PTFE) billets are compression molded tubes and rods made of Polytetrafluorethylene used in numerous industrial applications covering almost every industry, including chemical processing, automotive, food, aerospace, medical device, semiconductor, and fluid handling. These functional parts are popular due to Teflon’s chemical resistance, extreme temperatures, low friction properties, and ability to mold them into the precise shape and size needed.
Types of Molded PTFE Billets
The molded processing techniques we employ are compression, isostatic, and automatic. The determination of which method to use will depend on the type and size of billets being produced, the industry they are being used in, and the manufacturer’s preference.
Compression
Compression molding for PTFE billets is one of the three main processes, with isostatic and automatic as the other options (we will discuss these in a later article). To make a billet using this process, one must design and create the source mold for the rod or tube. The compression mold is a two-part mold that includes a preform component.
The performance has the same shape as the tube or rod being processed. The material is loaded into the mold, pressed under specific pressure and time depending on the grade of PTFE being processed, and then ejected for the mold.
The pressure causes the material inside the preform to conform to the mold’s shape. As a result, any excess material leaks out of the mold. Once the molding process is complete, the billet is ejected from the mold.
Once the billet is extracted from the mold, it is now in what is called the “Green State,” compact into the desired shape, but no molecular change has occurred; this only happens after sintering in our ovens for a designated time between 650 to 715 degrees F.
The billet is left to cool at room temperature. Once cooled, excess material can be machined off to make a smooth, perfectly formed Teflon billet.
Advantages of using compression molding include:
Strong parts
Lower tooling costs
Broad design options
Lower waste generation
Large part manufacturing
Sintering Molded Tubes, Rods, or Semi-Finished Parts.
Sintering results in a change in the PTFE powder that reorganizes the molecules into a compound. To sinter Teflon billets:
Billets must be supported to ensure that they do not sag
Adding an annealing cycle during the sintering processes will help to stop cracks from forming while the compound bakes. Once the billets are out of the oven and cooled to room temperature, they can be machined.
Molding Process
While all molds have physical property variations, the overall process is similar. Therefore, the variations between compression, isostatic, and automatic molded billets are inconsequential to the prevalent use.
The molding process is two-step. It begins with packing the mold and pressing the powder, called the “green state.” Next, the mold is placed under specified pressures depending on whether the material is unfilled (Virgin) or filled with various fillers, glass, carbon, graphite, etc. pressure of up to i.
After pressing, the item is removed from the mold. Workers must be careful during the ejecting of the tube or rod. Mishandling of the green material could result in cracks. Once the mold is removed, the billet is sintered.
conclusion
Molded PTFE billets are ideal for many industries. The properties of PTFE make them chemical resistant, have a low coefficient of friction, and can be manufactured compliant with FDA, Class VI Medical, NACE, Aerospace, and Semiconductor Standards approved for use in medical and food industries. In addition, clean Room Molding for Ultra Pure applications is available.
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.
Rotary seals are essential to maintaining the life of the equipment. While choosing the appropriate rotary seal materials, the rotary shaft mating surfaces are equally important.
Below, we will discuss rotary seals, materials used for seals, and rotary shaft properties.
Rotary Seals
Rotary seals work to help keep the system lubricated while excluding contaminates. A properly fitting seal can positively impact the life of the lubricant. Oil’s life span at 86°F (30°C) is 30 years. However, as the oil heats up, the life span diminishes rapidly to no more than a 30-day life span.
The addition of contaminants and water also limits the life of the oil and the ball bearings. For example, adding .002% water into the oil lubricant will reduce the ball bearing’s life by 50%. The cause of the ball-bearing integrity loss is called hydrogen embrittlement.
Common Materials Used for Rotary Seals
Rotary seals come in several different materials. The optimal choice is dependent on the environment in which it is used. The most common materials include nitrile rubber, polyacrylate rubber, fluoroelastomers (FKM), and PTFE.
While these materials are a good choice for rotary seals, conventional rubber seals are common in static applications where temperature and chemical compatibility are not a concern. PTFE is the solution in high-speed dynamic service requiring low friction seals or where exposure to severe temperature or chemicals exists. There are different types of PTFE used for rotary shaft seals. Users can choose from
Virgin PTFE
Molybdenum Disulfide Filled PTFE (MoS2)
Carbon Filled PTFE
Carbon and Graphite Filled PTFE
Carbon and MoS2 Filled PTFE
Glass Filled PTFE
Glass and MoS2 Filled PTFE
Polymide Filled PTFE
Properties of Rotary Shafts Mating Surfaces That Affect Sealing Performance
Most often, rotary shafts are metal. However, the rotary shaft mating surface could be made from plastics. No matter what material the shaft is made from, some properties will affect the sealing performance of the shaft.
The properties of the rotary shaft that affect sealing performance are the shaft harness and the shaft roughness. The sections below explain in greater detail how the hardness and roughness of the rotary shaft can affect the rotary shaft’s sealing performance.
Rotary Shaft Hardness
The hardness of the rotary shaft is how deep an indenter can penetrate the surface of a shaft. The shaft’s hardness is measured in the Rockwell C scale. The higher the number, the more complex the surface.
As a general rule, the rotary shaft should always be harder than the seal to ensure the seal wears out before the shaft. Additionally, if you choose a harder surface, there are more options for seal materials.
With a rotary shaft with a hardness exceeding 45 Rockwell C, the seal doesn’t have time to polish and “bed in.” That means that any roughness on the surface will cause issues with the seal, wearing it down quicker than average. A shaft with a hardness under 45 Rc requires a softer seal which doesn’t have as long of a life.
The choice of hardness depends on the environmental pressure and shaft speed. For example:
In environments of 1000 psi with rates up to 150 sfpm, a shaft with 70Rc or greater is necessary
Settings using shaft speed 2500 sfpm and 0 psi need a hardness of 60Rc or greater.
Rotary shaft speeds of up to 150 sfpm and 0 psi need a hardness of at least 35Rc, with lubrication, or 44, with no lubrication.
Rotary Shaft Mating Surface Roughness
The rotary shaft’s roughness refers to the shaft surface’s unevenness. To measure the roughness, measurements of high and low points of the shaft and taking the difference to determine the machined tolerance.
Ideally, a smoother surface will increase the seal life and offer outstanding performance. But on the other hand, when the surface is exceptionally smooth, there is no way for the oil to flow between the mating surface and the seal. As a result, the seal wears out quicker without lubricant between the seal and the mating surface.
Of course, a high roughness level can allow leaks through low points on the shaft. Therefore, the rotary shaft roughness needs to be relatively smooth but not so smooth that the seal cannot be lubricated.
Rotary shafts work with the rotary seals to keep lubrication from dirt and water. Understanding the properties of the rotary shaft mating surfaces helps determine the type of seal material chosen. Contact us today for your rotary seal and shaft mating needs.
High-performance liquid chromatography is the ideal method for analyzing various solutions in different fields. This machine, however, requires HPLC spring energized seals that adhere to strict guidelines with slight variation.
Different Liquid Chromatography Types
There are a few different types of liquid chromatography. The primary liquid chromatography types include high-performance liquid chromatography (HPLC), preparative HPLC, and ultra-high-performance liquid chromatography.
High-performance liquid chromatography is used in multiple different industries. HPLC is found in food science, drug development, and forensic analysis. It is used to separate compounds and used for quantitative and qualitative analysis.
Preparative HPLC is used in purification applications as it requires a higher flow rate. This liquid chromatography is also used to separate and collect high-purity compounds. It is also used for large quantities of compounds needed for evaluation and analysis.
Ultra-high-performance liquid chromatography (UHPLC) is similar to HPLC. It is used to separate different constituents of a compound and to identify and quantify the different components of a mixture.
Operating Conditions
HPLC pumps operate in conditions with variable flow rates and small shaft diameters. They have tight leak criteria and operate under a wide range of pressures. HPLC pumps have a medium-speed reciprocation.
Seals in HPLC pumps must withstand the solvents used to separate compounds dissolved in the liquid sample. Solvents used in HPLC include
MeOH (Methanol)
ACN (Acetonitrile)
H2O (Water).
The expected lifetime for seals in HPLC pump environments is a minimum of one million cycles. Seals may last longer depending on the flow rate, pressure, and media.
Seal Designs
HPLC seals prevent leaks from occurring. Should the mile phase lack into the back of the pump, it will impact consistency, accuracy, and pump precision. To effectively prevent leaks, seals should have effective leak resistance in pressures up to 20 kpsi.
Seal Geometry
The geometry of the seal is an important factor. For HPLC pumps, a flange design helps reduce the pump’s pulsation. HPLC spring energized seals have a longer seal ID lip and a polymer backup ring to increase the amount of contact stress.
UHPLC seals have a non-flange design and a shorter seal ID lip. Instead of a polymer backup ring, it uses a ceramic or metal backup ring. These seals have a concave back for higher-pressure distribution.
Jacket Materials
HPLC pumps’ seals have a PTFE or UHMW PE jacket. The UHMW PE material is used in systems with pressures greater than ten kpsi. UHMW PE is an FDA-compatible material for both food and pharmaceutical analysis.
PTFE jackets are the most chemical resistant of the common materials. The PTFE jackets are filled with graphite or polyimide. These fillers are heat and wear-resistant and work well in liquids and steam.
Performance Factors
Sealing performance factors are affected by the different surfaces in the HPLC pump. The housing surface has a suggested static sealing surface between 9.1 to 14.5 μin Ra.
On the plunger surface, a smoother surface is best. For virgin PTFE or UHMW PE, a minimum shaft hardness is 40Rc. The suggested dynamic surface is 7.3 – 14.5 Ra μin.
Medium
Dynamic Surface
Static Surface
Reciprocating
Rotary
RMS
Ra μin
RMS
Ra μin
RMS
Ra μin
Liquids
8 to 16
7.2 to 14.4
8 to 12
7.2 to 10.8
16 to 32
14.4 to 28.8
Plunger alignment needs to have a minimal shaft-to-bore misalignment with tight concentric guidance between the wash body and pump head. For best sealing performance, the shaft-to-bore misalignment should be kept to a minimum.
Shaft To Bore Misalignment at the Seal Area
Shaft Diameter (in inches)
Shaft to Bore Misalignment (in inches)
0.000 – 0.750
0.0020
0.751 – 1.500
0.0025
1.501 – 3.000
0.0030
3.001 – 6.000
0.0035
6.001 – 10.000
0.0045
HPLC Spring Energized Seal Recommendations
The HPLC spring energized seal requirements should be considered during the pump design process. Designers should collaborate with seal engineers early in development. Contact us today to get a quote on your next custom seal needs.
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.
Seals used in the oil and gas industry must withstand high temperatures, high pressure, and a chemically hostile environment. The conditions limit the material used to make the seals for this industry. The most common types of materials include
PTFE
PEEK
UHMW
PCTFE
Hytrel
Let’s look further into these materials, their benefits, and their limitations.
What is PTFE?
Polytetrafluroro Ethylene (PTFE) is a synthetic fluoropolymer with high-temperature resistance, commonly known as Teflon. It is a hydrophobic, high-molecular-weight polymer consisting of carbon and fluorine.
Benefits of Using PTFE
PTFE is ideal for use in the oil and gas industry as it is resistant to extreme high and low temperatures. In addition, PTFE has a low coefficient and a low dielectric constant. Finally, the hydro resistance nature of the material makes it a top choice for working with steam or heated seawater.
One of the most significant benefits of using PTFE is the resistance to harsh chemicals. It has the broadest chemical resistance of commercial polymers. For example, seals made of this material are resistant to hydrogen sulfide, ferric chloride, ferrous sulfate, hydrochloric acid, and hydrofluoric acid.
Limitations of PTFE
PTFE’s limitations make it unsuitable for some uses. For example, it is sensitive to creep and abrasion, requiring regular maintenance. PTFE also has low radiation resistance and can corrode and produce toxic fumes as it breaks down.
Properties of PTFE
PTFE has a density of 2200 kg/m3 with a melting point of 327°C (620°F). PTFE maintains self-lubrication, strength, and toughness at temperatures down to -268 °C (-450.67°F). Additional properties include:
What Are Some Common Oil and Gas Applications of PTFE?
PTFE is one of the more common materials used in oil and gas seals. For example, O-rings, slipper seals, backup rings, piston rings, and spring-energized seals use PTFE material. In addition, natural gas, cold media seals, bearings, and wear components also use PTFE for manufacturing.
What Is PEEK?
Polyetheretherketone, or PEEK, is a colorless organic thermoplastic semi-crystalline polymer with excellent mechanical and chemical resistance properties. It’s high-resistance to terminal degradation makes it useful in oil and gas environments.
PEEK has high mechanical strength and is ideal for high vacuum applications. Its robust nature makes it suitable for demanding applications such as the oil and gas industry. It works well in compressors, pumps, and pistons.
Limitations of PEEK
Despite PEEK’s many benefits, there are some drawbacks to using this material. It has low UV light resistance. It is also unsuitable for nitric acid, sulphuric acid, sodium, and halogens. In addition, it is expensive to make and requires high temperatures to process.
Properties of PEEK
PEEK has a high tensile strength of 25000 to 30000 psi. It has a V0 flammability rating of 1.45mm and can withstand high loads for extended periods without residual damage. Additional properties include:
What Are Some Common Oil and Gas Applications of PEEK?
Labyrinth, spring-energized piston seals, backup rings, and seal packing in the oil and gas industry are manufactured using PEEK materials. In addition, it is the material most often chosen for the face seals at the wellhead to contain the high-pressure production of gas and fluid.
What is UHMW Polyethylene?
Ultra-High Molecular-Weight, UHMW, Polyethylene seals are thermoplastic, semi-crystalline materials. It is lightweight with a high-pressure tolerance that makes it ideal for spring energized seals used by the oil and gas industry.
Benefits of Using UHMW Polyethylene
Seals made from UHMW have the benefit of being both abrasion and impact resistant. This self-lubricating material has a low friction coefficient. It withstands extreme colds and high temperatures.
It has a high molecular weight, meaning UHMW is not likely to melt and flow as a liquid. This material cannot be molded by traditional methods, thanks to the high molecular weight. Instead, it is compression molded to make it stronger.
Limitations of UHMW Polyethylene
While UHMW Polyethylene has many benefits for the oil and gas industry, there are some limitations, such as having a lower maximum continuous surface temperature than other materials.
UHMW Polyethylene has a compressive strength of 3000 psi. In addition, it has a maximum safe workload of 1000 psi in some industries. Overload can cause UHMW polyethylene to crack or break.
Properties of UHMW Polyethylene
UHMW polyethylene seals are self-lubricating and have low surface energy, which makes them ideal for the oil and gas industry. Other UHMW polyethylene properties include
What Are Some Oil and Gas Applications for UHMW Polyethylene?
UHMW polyethylene material is used for seals in the oil and gas industry. It is used to make spring energized seals. It is also used for cargo dock impact bumpers and liners.
What is PCTFE?
Polychorotrifluoroethylene (PCTFE) is a chemical compound with a high tensile stretch and good thermal properties. Its chemical-resistant properties make it ideal for use in the oil and gas industry for seals and other components.
Benefits of Using PCTFE
Seals made with PCTFE are nonflammable and heat resistant up to 175°C (347°F). They are also resistant to acetone, hydrochloric acid, sodium peroxide, citric acid, and sulfuric acid. It is water-resistant as well.
PCTFE has a board temperature range with a useful temperature range of -204.4°C (-400°F) to 193.3°C (380°F). When comparing PCTFE vs PTFE, PCTFE is a stronger polymer with better mechanical properties.
Limitations of PCTFE
PCTFE has many beneficial properties for the oil and gas industry. However, some limitations, such as a lower melting point when compared to PEEK or PTFE, might make it less desirable. Seals used in extreme temperatures may need to be a different material.
Additionally, PCTFE is a stiffer material. While this does allow it to maintain its dimensions better, it does break easier than PTFE. Along with being stiffer, it is not as non-stick when compared to PTFE.
Properties of PCTFE
PCTFE has V-0 flammability and a hardness of 67 at 100°C and 80 at 25°C. Other properties include
What Are Some Oil and Gas Applications for PCTFE?
Like PEEK or PTFE, PCTFE is a great material for seals in the oil and gas industry. It’s chemical resistance, which means it can be used in the most volatile industries. Fillers within the seals can enhance some of the properties. PCTFE is also used in component designs and valve seats.
What is Hytrel?
Hytrel is a thermoplastic polyester elastomer that is plasticizer-free. It is a stable material with needed flexibility while handling high temperatures. It is a worthwhile option to consider for the oil and gas industry.
Benefits of Using Hytrel
As a seal material for the oil and gas industry, Hytrel has good chemical resistance. It can withstand exposure to fuel, hydrocarbon solvents, and oil. Additionally, as the material is exposed to higher temperatures, it becomes more rigid. At lower temperatures, it is more flexible.
Hytrel is abrasion resistance. It offers impact and creep resistance to the seals. It also is resilient and excels at providing flex fatigue and tear resistance. Hytrel has a natural spring-like property and has low hysteresis.
Limitations of Hytrel
As there are several models of Hytrel, only a few are best for use in seals. Hytrel 4556, 4056,4068,4069, and 6356 are the ones that work best. However, these don’t always work well in the oil field, so you should know which ones to look for.
Properties of Hytrel
Hytrel has V-0 flammability and a hardness of 67 at 100°C and 80 at 25°C. Other properties include
What Are Some Oil and Gas Applications for Hytrel?
Hytrel is useful as a seal material in the oil and gas industry. As it is resistant to many chemicals, including hydrocarbon solvents, it is ideal for hazardous conditions.
Which Seal Type is Best for the Oil and Gas Industry?
Each seal type has its uses and benefits for the oil and gas industry. However, the best options are PEEK, UHMW, PCTFE, and Hytrel. It is because they have the best physical properties to withstand the harsh conditions in the oil and gas field.
At Advanced EMC Technologies, we offer custom-engineered sealing systems that provide reliable sealing solutions. Our seals perform under high temperatures, high pressure, and chemically hostile environments. Contact us for more information.
Seals for Oil and Gas Industry FAQ
IS PEEK environmentally friendly?
There is no evidence that PEEK has a significant environmental impact in its service life, disposal, or manufacturing. Toxicity is low and does not contain anything known to be toxic. There is low smoke, poisonous gas emissions, and fire when involved in a fire.
What are spring-energized seals?
Spring-energized seals can store mechanical energy by compressing the spring. As a result, they withstand more pressure and heat than their conventional counterparts. In the end, the mechanical energy stored in the seal keeps it from leaking.
