Backup shaft bearings made from DuPont Vespel CR-6100 are part of a Chempump NC series canned motor pump used to load anhydrous HF acid into tank cars at a DuPont plant in Texas.
While the pump’s primary shaft bearings are made of silicon carbide, it is equipped with backup shaft bearings made of Vespel CR-6100. The process fluid provides bearing lubrication and process temperature is ambient.
Safety and reliability are the key benefits gained from the backup shaft bearings made of Vespel CR-6100. The function of the backup bearing is to prevent the rotor from falling, which could allow the escape of HF from the containment area in the event of a primary bearing failure.
The pump was previously equipped with silicon carbide parts for both primary and backup bearings. The use of a backup bearing material with different properties from that of the primary bearing increases safety.
Vespel CR-6100 is an advanced composite material consisting of DuPont Teflon PFA fluoropolymer resin and oriented carbon fibres. The material offers excellent resistance to HF and its low wear and friction properties extend the life of the backup bearings.
When removed for inspection in August 2005, after five years of intermittent service with exposure to HF for the entire time, the Vespel CR-6100 bearing showed no evidence of deterioration.
DuPont Vespel CR-6100 was selected for the backup shaft bearings in the aggressive process-lubricated environment because of its resistance to anhydrous HF, low friction, low wear, high PV capability, dimensional stability and low coefficient of thermal expansion (70% lower than that of carbon steel).
DuPont Vespel CR-6100 is available from Fluid Seals .