Long-life seals cut maintenance

Edited by the Engineeringtalk editorial team Oct 20, 2003

By replacing PTFE O-ring seals with Kalrez Spectrum 6375 perfluoroelastomer parts, Dow AgroSciences has extended the life of dynamic and static seals fitted to its product filling line by some 6000%.

By replacing O-ring seals of polytetrafluoroethylene (PTFE) with DuPont Dow Elastomers Kalrez Spectrum 6375 perfluoroelastomer parts, Dow AgroSciences of Drusenheim, France, has extended the lifetime of dynamic and static seals fitted to its product filling line from one day to an average of two months, an improvement of some 6000%.

The filling line at Dow AgroSciences plant in France processes aggressive solvents, surfactants and concentrated herbicides at temperatures ranging from 10 to 45C, and pressures from 1.5 to 3.5bar.

Filling machine valves on the line were fitted with dynamic PTFE O-ring seals, while the machine hoses were equipped with static O-rings, also of PTFE.

Michel Blondel, mechanical maintenance leader at the plant, explains the problem: "Each time we performed a clean-in-place procedure at 80C, or made a product change on the filler, the PTFE seals became mechanically damaged.

This meant we had to change the PTFE O-rings on a daily basis, since seal lifetime never extended beyond 24 hours before replacement".

The cost to Dow AgroSciences in extra downtime and maintenance had become unacceptable, and the company sought a much more resilient sealing material that would withstand frequent cleaning and product changes, and offer greatly extended seal lifetime.

In conjunction with Kalrez authorised distributor Eriks, Michel Blondel installed dynamic and static Kalrez Spectrum 6375 perfluoroelastomer O-rings to replace the PTFE seals, with dramatic and immediate improvement.

Kalrez Spectrum 6375 is designed specifically for the chemical process industry.

It provides outstanding performance in an extremely wide range of chemicals including acids, bases, amines and steam.

The innovative patented new curing system allows for continuous upper service temperatures of 275C in applications such as mechanical seals, valves, flanges and pumps where elastomeric sealing is critical.

In addition, Kalrez is a thermoset perfluoroelastomer and offers excellent elastic properties and resistance to mechanical damage, unlike PTFE which is a thermoplastic and generally lacks the necessary resilience to withstand mechanical shock in a process application such as this.

Since switching to custom O-rings of Kalrez Spectrum 6375, Dow AgroSciences reports an average seal lifetime of two months.

That's an increase of approximately 6000% over the previously fitted PTFE seals.

"The use of Kalrez Spectrum 6375 allows us to increase the operating uptime of our filling machines and to improve overall reliability of our packing line.

We have also significantly reduced the time spent in O-ring replacement", says Blondel.

He also reports cost savings as a result of major improvements in safety and reliability, and in reduced maintenance.

In a different application at the same plant, seals of fluoroelastomer FEP/FKM, fitted to the piston rod of a Type SRC Alfa Laval valve, failed regularly after only 8h operation.

These seals have now been replaced by Kalrez perfluoroelastomer parts, resulting in an increase in operating lifetime from 8h to between 8 and 12 months.