Chemical Engineering World IMPACT FEATURE
A major problem facing the world’s leading chemical companies is how to increase their MTBF (mean time between failure) of their screw spindle pumps from several weeks to several years, while improving safety at all pump installations.
For example, a rotary pump might be used as a reactor pump to carry EO/PO (ethylene oxide, propylene oxide), which is a very reactive, dangerous medium. EO/PO end users generally will not change o-ring specifications without thorough proof of chemical compatibility.
Perfluoroelastomers, also known as FFKMs, are elastomeric sealing materials with broad chemical compatibility and high temperature resistance. Selecting an FFKM optimized for EO/PO applications could reduce the possibility of equipment failure.
After repeated failures of multiple FFKMs, a leading EO/PO chemical company located in Eastern Germany was looking for an FFKM that would increase their MTBF from several weeks to several years, while improving safety at all pump installations.
Their previously installed perfluoroelastomers swelled and lacked sealing force, resulting in unplanned maintenance every few weeks, which was unacceptable.
The chemical company contacted Greene Tweed, who offered an ideal solution to extend MTBF – by installing seals manufactured from Chemraz® 505, one of few materials recommended for service in corrosive EO media.
Greene Tweed, a leading global manufacturer of high-performance materials and products, leverages extensive engineering, design, and manufacturing expertise to provide solutions that provide exceptional performance in the challenging environments of the chemical processing market.
After careful evaluation of the application and its operating parameters, Greene Tweed proposed Chemraz® 505 o-rings as a solution. Chemraz® 505, a perfluoroelastomer, provides a broad range of chemical resistance, and is used in o-rings, gaskets, and many other custom shapes. Because of its versatility, Chemraz® 505 is often used as a standard compound and can be found in a variety of applications, including acids, caustics, aldehydes, esters, ethers, aromatics, hot water, steam, amines, methanol, ketones, TBA, and MTBE.
With a temperature range of -22°F to 446°F (-30°C to 230°C), Chemraz® 505 is ideal for processes in subzero temperatures and for use in multisubstance plants or in mixed media due to its broad chemical resistance. Its lower compression set provides better ability to handle such temperature and pressure variations, along with shaft misalignment, and o-ring shrinkage.
After receiving the recommendation to install Chemraz® 505 o-rings in their pumps, the East German chemical company:
- Successfully trialed Chemraz® 505 in an R&D pilot EO service plant in the same location.
- Retrofitted four screw spindle pumps with Chemraz® 505 for a total of 16 mechanical seals.
- Specified Chemraz® 505 for all screw spindle pumps throughout the plant.
Chemraz® 505 successfully replaced all four of the previously used competitor elastomers.
- Improved reliability/MTBF — Chemraz® 505 o-rings have increased pump lifetime from several weeks to almost four years. The pump continues to run without problems. Scheduled maintenance is set for every five years, and it appears this goal will be met without a challenge.
- Excellent chemical resistance in aggressive media and chemical attack — Chemraz 505® reduces the risk of seal swell in EO/PO service, thus decreasing the possibility of equipment failure due to leakage.
Chemraz® Chemical Processing Solutions
For more than 30 years, Greene Tweed has been pushing the limits of materials science developing high-performance solutions for the chemical processing industry. Greene Tweed’s Chemraz® perfluoroelastomers lead the way for critical sealing applications, with proven reliability in harsh environmental conditions. The ultimate elastomeric material, Chemraz® FFKM is engineered from fluorinated monomers, including tetrafluoroethylene and perfluorovinylether, and a cure site monomer for crosslinking. Chemraz® offers the broadest chemical resistance of any elastomeric material, combining the resilience and sealing force of an elastomer with chemical resistance approaching that of PTFE while withstanding a wide range of temperatures (-40°F to 615°F, -40°C to 324°C). Its distinctive chemical composition makes it well suited for a range of applications. Because of its low compression set, outstanding physical properties, and universal chemical resistance, Chemraz® reliably reduces the risk of unplanned downtime due to equipment failure.
For more information