Gallagher recently released our Introduction to Perfluoroelastomers White Paper, available for download on our site. This was written by Russell Schnell, a current contracted employee of Gallagher Fluid Seals, and more importantly, a former Senior Application Engineer with the Kalrez® perfluoroelastomer parts business at DuPont. The following is the third and final excerpt from the White Paper, discussing seal design and a cost-benefit analysis of using perfluoroelastomer seals.
Seal Design with Perfluoroelastomer Seals
Care must be taken when designing and using seals made of perfluoroelastomers. These elastomers typically have a higher coefficient of thermal expansion when compared to other elastomers; plus, they are often used at higher temperatures. If the seal gland design is not correct, seal extrusion will occur, resulting in seal failure. For example, a fluoroelastomer seal is scheduled for replacement with a perfluoroelastomer seal, due to high application temperatures. Shortly after this substitution, the FFKM seal fails due to extrusion. The probable cause is that the seal gland volume was too small to accommodate the thermal expansion of the high performance perfluoroelastomers, a factor that many of today’s seal design handbooks do not adequately take into account.
Continue reading Introduction to Perfluoroelastomers – Part 3
Gallagher recently released our Introduction to Perfluoroelastomers White Paper, available for download on our site. This was written by Russell Schnell, a current contracted employee of Gallagher Fluid Seals, and more importantly, a former Senior Application Engineer with the Kalrez® perfluoroelastomer parts business at DuPont. The following is the second excerpt from the White Paper, discussing the common industries in which perfluoroelastomer seals are used, and why.
Common Industries in Which Perfluoroelastomer Seals are Used and Why
In general, perfluoroelastomers are the most expensive elastomer seals specified in the marketplace; however they also provide the highest performance sealing service. As with any product, the selection of these products should be the result of a cost-benefit analysis.
Oil Processing Industry
One of the earliest uses of perfluoroelastomer seals was in the oil industry (down-hole). Seals used in down-hole oil applications required resistance to high temperatures and aggressive chemicals. Sour oil and gas, resulting from H2S, often caused swift degradation of fluoroelastomer seals. The ability of perfluoroelastomer seals to resist H2S was a major reason for their selection and use. Over time, as wells became deeper and deeper, the application temperatures increased. As a result, in addition to aggressive chemicals, better high temperature resistance was needed and FFKM seals provided that benefit. Finally, seals used in these applications must have an “acceptable” service life. Oil wells are expected to last for many years and a seal failure, especially during initial exploration results in lost time and great expense when down-hole equipment must be retrieved to repair a seal. So the important points for this industry are resistance to aggressive chemicals, high temperatures, and reduced chance of seal failure which can result in tremendous expense.
Continue reading Introduction to Perfluoroelastomers – Part 2
Gallagher recently released our Introduction to Perfluoroelastomers White Paper, available for download on our site. This was written by Russell Schnell, a current contracted employee of Gallagher Fluid Seals, and more importantly, a former Senior Application Engineer with the Kalrez® perfluoroelastomer parts business at DuPont. The following excerpt is the first section of the White Paper, discussing the history or elastomers and perfluoroelastomers, and the chemistry that helped create these modern materials.
Introduction to the World of Perfluoroelastomers
The use of elastomers is widespread in our world. Elastomers have many uses including: sealing fluids, for tires, in chemical plants, in semiconductor manufacturing equipment, for dust and moisture seals on cell phones, and seals on aircraft engines. The function of the elastomer and technology involved can vary from something as simple as a barrier to rain water, to seals in automobile engines, to critical sealing applications on the Space Station. Selection of the correct elastomer in an application is very important for successful and long term equipment operation. Although many different elastomers exist in the marketplace, when the highest service performance is needed, in terms of chemical and high temperature resistance, the choice is perfluoroelastomers.
A perfluoroelastomer can be represented by the letters: FFKM or FFPM (ASTM and ISO designations, respectively). The word itself has two parts, perfluoro (meaning fully fluorinated), and elastomer. Perfluoroelastomers exhibit many properties similar to PTFE (polytetrafluoroethylene), which is also fully fluorinated and considered inert to almost all solvents. PTFE is often referred to as Teflon®, which is a registered trademark of The Chemours Company. PTFE is a plastic, and when compressed, will not recover to its original shape. However, elastomers contain crosslinks, which act as springs to give the material resiliency and the ability to recover after a part has been compressed. This resistance to permanent compression (compression set) gives the material the ability to maintain a seal over time. Finally, while whereas plastics are crystalline, elastomers are amorphous at room temperature; they can be easily compressed and will mold themselves to maintain a seal. Given the chemical structure and performance similarities of FFKMs to PTFE, perfluoroelastomers are sometimes referred to as an elastomeric form of PTFE.
Continue reading Introduction to Perfluoroelastomers – Part 1