Polytetrafluoroethylene (PTFE) is commonly known as a coating for pans under the DuPont trade name Teflon™. It is also superbly suited as a sealant and is superior to many materials in specific ways. For example, it can be used at low and high temperatures and in combination with gasoline, solvents, water and other polar media such as lyes, standard lubricants and brake fluid. PTFE’s chemical resistance is nearly universal.
In 1938, while working for DuPont, American chemist Roy Plunkett was looking for a substitute for the fluorohydrocarbon Freon, which his employer was only allowed to sell to General Motors’ Frigidaire division for patent-related reasons. For his research, he had obtained a supply of tetrafluoroethylene (TFE), which was used as refrigerator coolant. He stored it in small pressurized gas cylinders at low temperatures. When he was ready to use the gas after a fairly long storage period, none was left in the container. But its weight was unchanged. After it was opened, there were white crumbs inside and the inner walls of the container were covered with a thin layer. Plunkett quickly realized that the TFE gas had been polymerized into a plastic. This new plastic, PTFE, proved to be completely resistant to chemical exposure. Not even aqua regia¹ could harm it in any way. But its production was so costly that practical uses seemed inconceivable.
Continue reading PTFE as a Sealing Material
There are many factors to be considered when choosing the right type of hose for your application. There are many different types of hose available on the market. They include metal, rubber, composite, PTFE and fabric. The decision of which hose type to buy depends on the application for which the hose is being used.
Metal hose is ideal for absorbing vibration, misalignment correction, thermal expansion or contraction of piping systems, and protecting equipment from excess motion. Typically, metal hose is used when no other (non-metallic) constructed hose will work. In other words, metal hose is used as a last resort.
Here are some of the factors that should alert you it’s time to use metal hose:
Continue reading When To Use Metal Hose
In our latest video, Gallagher Fluid Seals Engineering Manager Craig Beil discusses the various PTFE fillers used in making seal materials. Fillers include carbon, glass, stainless steel and molybdenum disulfide. Watch the video to learn more about what PTFE fillers can do, and be sure to watch the other videos in our series.
Past videos have explored issues such as radial seal misalignment, the use of spring energized seals and environmentally-designed static seal gaskets.
We hope you can find something useful in each one.
Today we’ll continue our look at spring-energized seals by exploring some of the preliminary considerations to made when working with these seals.
A spring energized PTFE seal is selected to fit an exact set of service conditions found in your application.
Gallagher Fluid Seals recommends conducting a review of the entire sealing environment. You should use the Engineering Action Request (EAR) form before selecting a seal design.
Continue reading Preliminary Considerations for Spring-Energized Seals
Spring energized PTFE seals use one of three different types of springs to energize the jacket. When choosing a spring design, consider two elements: load value and deflection range.
The spring’s load affects its ability to seal, friction, and wear rate. As the load increases, the lips seal tighter, while friction and wear increase proportionately.
The deflection range affects the seal’s ability to compensate for variations in gland tolerances and for normal seal wear. Each spring size has a specific deflection range. The available deflection increases as the seal and spring cross-section grows. This increase could be a deciding factor in choosing a cross-section. Use springs with a wide deflection range when sealing surfaces are not concentric. Continue reading What Springs Do Spring Energized PTFE Seals Use?
Gallagher Fluid Seals is pleased to introduce its newest video, which discusses GORE expanded PTFE.
The clip features our engineering manager Craig Beil discussing the history of this product, its attributes, and the ways Gallagher uses GORE expanded PTFE to help create sealing solutions.
Watch the video above to find out more, and be sure to contact Gallagher Fluid Seals if you have further questions. We look forward to hearing from you.
Spring energized PTFE seals perform reliably in a variety of applications where conventional elastomeric seals fail due to chemical attack, extreme heat or cold, friction, extrusion or compression set.
PTFE seals have three basic design elements:
- A pressure-actuated U-shaped jacket
- A metal spring loading device
- High performance polymeric seal materials
So what is a spring energized PTFE seal? It’s a spring-energized U-cup that uses a variety of jacket profiles, spring types and materials in rod and piston, face and rotary seal configurations. They are used when elastomeric seals fail to meet temperature range, chemical resistance or friction requirements.
Jacket profiles are made from PTFE and other high performance polymers. Spring types are available in corrosion-resistant alloys, including stainless steel, Elgiloy and Hastelloy.
Continue reading What is a Spring Energized PTFE Seal?
Today we’ll conclude our series of blog posts on PTFE by discussing some PTFE radial lip seal applications, as well as a brief look at wear sleeves.
PTFE has superior mechanical and physical properties and chemical resistance, which means the areas where PTFE radial lip seals are used is growing. These areas include:
Diesel Engine Applications
These consist of the front and rear crankshaft, accessory drive, and blower and thermostat seals. PTFE seals are used and tested in these areas because they can meet the performance and life requirements of modern engines.
Minimum wear, performance at high temperatures with limited lubrication, resistance to abrasive contaminants and fluid compatibility are the main factors for PTFE’s use in these applications.
Continue reading PTFE Radial Lip Seal Applications
Today we’ll continue our look at PTFE rotary seals by focusing on three areas: housing/bore considerations, pressure and shaft velocity and shaft misalignment and runout.
Typical PTFE rotary lip seals are pressed into the bore to assure proper OD sealing and seal retention in the housing. Most seal and housings are made from steel and cast iron. Take care when softer materials – aluminum, bronze, plastic – are used for the housing. Aluminum has a thermal expansion rate almost double that of steel. Metal case designs can lose the required press fit in an aluminum housing when they go through thermal cycles due to the higher rate of thermal expansion of aluminum.
A finish range of 32 to 63 μin Ra (0.8 to 1.6 μin Ra) is recommended for service pressures up to 3 psi (0.20 bar). For thicker fluids such as grease, a 125 μin Ra (3.17 μin Ra) finish would be acceptable with no system pressure.
A lead in chamfer is strongly recommended for all seal housings. The chamfer aligns the seal during installation and helps keep the seal from cocking. Both corners of the chamfer should be free of burrs or sharp edges. For pressurized rotary applications, take additional precautions to ensure the seal isn’t pushed from the housing.
Continue reading PTFE Rotary Seals: Housing, Pressure and Shaft Run-Out
As we continue this blog’s PTFE series, we’re going to take a closer look at PTFE rotary seal shaft considerations.
In rotating applications, proper surface finish is crucial for getting positive sealing and the longest seal life possible. Rotating surfaces that are too rough could create leak paths and can also be very abrasive. Unlike elastomer contact seals, PTFE lips can run on very smooth surfaces regardless of lubrication.
Continue reading PTFE Rotary Seal Shaft Considerations