Seal in long-term savings

When it comes to minimizing costs, the traditional focus on component or unit cost may be giving way to an alternative approach. Indeed, more and more users are deciding that the long-term benefits of premium-priced elastomeric seal technology outweigh the initial investment.

By Russell Schnell, DuPont Performance Elastomers

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Today’s business environment is extremely challenging. Chemical manufacturers must contend with fierce marketplace competition, a demanding regulatory environment, and unprecedented energy prices that can offset productivity improvements. So, the companies must strive for even tighter cost control and improved systems efficiency.

When it comes to minimizing costs, the traditional focus on component or unit cost may be giving way to an alternative approach. Indeed, we’re finding that leading pump manufacturers and chemical processors are exploring how the long-term benefits of premium-priced technology outweigh the initial investment.

A truer picture

In the low-bid-focused economic evaluations of the past, equipment was purchased with a view only towards the next year. Elastomeric seals for mechanical pumps were considered disposable parts whose service life was difficult to predict. With the technology available today, it has become a little easier to project the life expectancy of equipment.

This knowledge has permitted companies to venture into new territory — to consider the total cost of the sealing solution, i.e., the price of the elastomeric seal plus the outlays for installation and downtime — including costs incurred by manufacturing slowdowns or potential disturbances such as leakages related to seal quality. In other words, manufacturers are beginning to look at cost reduction over time.

As Figure 1 shows, the expense of unplanned downtime generally far outweighs the initial purchase price of a premium-priced elastomeric seal.

Figure 1. The largest cost component is unscheduled downtime.

Figure 1. The largest cost component is unscheduled downtime.

The cost of an individual seal can range from as little as 50 cents to several hundred dollars. Production costs incurred by seal failure are much higher. The results of interviews we did in Europe in 2005 and 2006 with seal manufacturers, distributors and end users put the downtime cost of standard seal failure at around $3,800 per hour per pump without an in-line spare. (There is no downtime cost with an in-line spare pump.) This takes into account a process shutting down, two hours to replace a seal, lining out the process and start-up. The cost certainly could be higher for a complex process. Pump failure also can lead to other costs, e.g., environmental, safety and quality ones.

What does this mean? When manufacturers opt for low-cost elastomeric seal replacement, the short-term savings may not always translate into long-term value. Conversely, a premium-priced part that outperforms its cheaper rival may deliver significant savings. The difference is that the value can be measured during use rather than at the outset. Extending the mean time between repairs (MTBR) has a strong impact on reducing cost and improving production parameters such as rate and quality.

Successful seal performance requires careful consideration of process conditions, elastomer properties and seal design. A deficiency in any of these areas will result in a reduction of seal service life and the possibility of sudden seal failure. Chemical attack, high temperatures and mechanical stresses are common culprits.

Perfluoroelastomer pluses

Kalrez perfluoroelastomer parts resist more than 1,800 aggressive industrial chemicals and can handle temperatures up to 327ºC. The combination of long-term resistance to chemical damage, swelling and elevated temperatures enables users to minimize expensive seal failures and improve MTBR, thereby reducing maintenance and operating costs and increasing productivity.

For instance, C.D.R. Pompe, Senago, Italy, has dramatically extended the lifetime of O-ring seals operating in aggressive process media by switching to Kalrez Spectrum 6375 perfluoroelastomer parts. “The previous O-rings of fluoroelastomer, mounted on our type FC 35/50 mechanical seal and operating with impure sulfuric acid for dust laying service, failed each time after a maximum service life of only two months. By comparison, the Kalrez Spectrum 6375 O-rings are still operating after two years in an identical critical environment without problems,” says Roberto Michelucci of C.D.R. Pompe.

Dow AgroSciences, Drusenheim, France, has seen the life of dynamic and static seals rise from one day to an average of two months by switching from PTFE to Kalrez Spectrum 6375. “Each time we performed a clean-in-place procedure at 80°C or made a product change on the filler line, the PTFE seals became mechanically damaged. This meant we had to change the PTFE O-rings on a daily basis,” explains Michel Blondel, mechanical maintenance leader at the plant (Figure 2).

Figure 2. Michel Blondel (left) credits change in material with boosting filling-machine seal life more than fifty-fold.

Figure 2. Michel Blondel (left) credits change in material with boosting filling-machine seal life more than fifty-fold.

“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,” he says. Blondel also reports cost savings as a result of major improvements in safety and reliability, and reduced maintenance.

These high-performance perfluoroelastomer seals can help to improve safety by controlling fugitive emissions and preventing contamination of process streams. As chemical makers know, it’s costly not to strive to decrease environmental risk. Regulatory demands will continue to drive manufacturers towards cost-efficient environmental solutions. As an example, the European Union’s Integrated Pollution Prevention and Control directive (IPPC, 96/61/EU ) will take effect this October, compelling process plants to reduce the loss of volatile organic compounds through unexpected leaks, evaporation, flaring or spills.

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