The right calculation
How balancing unit cost against total system cost can lead to efficiencies

Leading pump manufacturers and chemical processors are reporting significant long-term savings from their initial investments in perfluoroelastomer seals—which provide the highest level of elastomeric sealing performance—through greatly reduced downtime and longer seal life, leading to increased productivity and lower environmental risk.

At a time of high energy prices and global competition, it is natural for companies in the process industries to focus on cost control. Manufacturers of pumps and other fluids handling equipment, for instance, may substitute cheaper materials and components for more expensive ones. But a focus on “component cost” or “unit cost” is often misguided, and is already giving way to a better alternative.

DuPont Performance Elastomers (DPE) has observed that many of its customers for Kalrez high-performance perfluoroelastomer parts are figuring long-term running costs into their calculations. These pump manufacturers and chemical processors are finding that the long-term benefits of premium-priced technology can outweigh the initial investment.
The total cost of an elastomeric seal includes the price of the seal itself, the installation cost, and the cost of leaks and downtime associated with seal failure and routine maintenance. The cost of a seal ranges from e0.5 to several hundred Euros, but the cost of seal failure can be much higher. For a pump without an installed spare, for instance, one industry estimate for the cost of seal replacement is e3,000, based on two hours’ lost production.
The value of technology
This means that when manufacturers opt for low-cost seals, the short-term savings may not always translate into value if the seal does not perform. Conversely, if a premium-priced part outperforms its lesser-priced rival, it can deliver significant value. Each production site has its own view of the equation, but the drive to reduce downtime and extend mean time between repairs (MTBR) is all-pervading. Parts that offer high performance, such as seals that can deliver in the harshest processing environments, can play a big part in improving efficiencies.
Compared to other sealing options, the long-term reliability and performance of Kalrez perfluoroelastomer seals can help the bottom line. Kalrez parts resist over 1,800 aggressive industrial chemicals, solvents and plasmas, at temperatures up to 327 °C. Long-term resistance to chemical damage, swelling and elevated temperatures enables customers to minimize expensive seal failures, improve MTBR, reduce maintenance and operating costs, and increase productivity. Kalrez high-performance perfluoroelastomer seals can also help to improve safety by controlling fugitive emissions and preventing contamination of the process stream. As process manufacturers know, ignoring environmental risk can be costly. The regulatory demands on the industry will continue to increase, driving manufacturers towards cost-efficient environmental solutions.
The benefits obtained from high-performance sealing solutions depend on the nature of the process. DPE has identified four scenarios that help to gauge the effect of sealing technology on total system cost (see figure).
Case A
In the first—rather rare—scenario, a seal that is not made from perfluoroelastomer lasts for the life of the equipment to which it is fitted. Strictly on a cost basis, the use of perfluoroelastomers is not justified in this case.
Case B
In the second scenario, the seal needs to be replaced once or twice during the life of the equipment, either because it has failed or to forestall failure. This introduces the cost of downtime each time the seal is changed, and it could well be cost-effective to use Kalrez perfluoroelastomer seals.
Case C
The third scenario involves seals that fail, and are replaced, several times during the life of the equipment. A conservative estimate is that perfluoroelastomer seals will last four times as long as seals made from conventional materials. As a result, the costs of seal replacement, downtime and possibly cleanup can far outweigh
the higher initial cost of perfluoroelastomers.
Case D
In the fourth scenario, seals are replaced on a maintenance schedule that is designed to avoid the unexpected downtime that follows seal failure. Switching to Kalrez perfluoroelastomer seals can extend the maintenance interval by a factor of two, in some cases three or four, and is generally cost-effective.