New seal refinements include novel designs

Sept. 30, 2009
Sheila Kennedy, contributing editor, explores how refinements broaden applications, improve reliability and reduce costs.

Seals, seal sets and seal support systems help prevent or limit leakage and allow companies to control costs and ensure process reliability and performance, while complying with environmental and safety standards. Recent advances range from new seal materials that meet specific industry requirements to novel designs that serve wider business and application needs.

Engineered materials: Hygienic-design couplings in food, beverage, pharmaceutical, and bioprocessing plants require excellent sealing integrity to protect the product from contamination and bacteria. Trelleborg Sealing Solutions has engineered a fluorocarbon sealing material for a range of static seals for hygienic pipe couplings. The fluorocarbon (FKM) compound was tested with cleaning fluids, hot water, steam, and varying water types to ensure it will provide long-term sealing integrity for pipe coupling gaskets and o-rings. Greater sealing integrity translates to greater product purity, more time between maintenance, and less production downtime and costs.


Volume swell was minimal with the 21 clean-in-place (CIP) media tested. In most CIP media, the change was less than 5%, and in some cases near zero. Trelleborg’s FKM V8T41, which had the best overall performance, is suitable for hot water and steam applications to 338°F, including heat exchangers or other ultra-high-temperature processing equipment, and it performs well in contact with dry and liquid products. The FKM V8605 is designed for processes that have high temperatures, contact with high-fat media such as edible oils or cosmetics, or where lubrication with grease or mineral-based oils is required.

Metal-free design: Some mechanical seal designs avoid the need for special materials. EagleBurgmann demonstrates this in its completely redesigned MR-D series agitator mechanical seals. The seals, suited for applications with sticky, viscous, or dry media, have a shaft sleeve contour that prevents product contact, making it possible to use solid silicon carbide (SiC) on the inboard rotating seat. Because the shaft sleeve can’t come into contact with the product, there’s no need for special materials. In addition, the MR-D’s modular design reduces service and spare parts carrying costs, and allows support for individual options such as floating bearings and a built-in pumping mechanism. The metal-free standard MR-D is suitable for product pressure to 14 bar (200 psi) and temperatures to 392°F.

Multipurpose seal: Seals with modular designs and a common platform for multiple applications simplify and shorten the installation effort. John Crane’s Type 3740 Cartridge Split Seal is designed for both wet and dry applications with few component and material differences. It has three factory preassembled modular components, including the rotor assembly, primary ring assembly, and gland plate assembly. The two variations of the seal are the Type 3740 for wet-running services and Type 3740D for dry-running services. Type 3740 performs reliably in rotating equipment fluid services such as pumps and side-entry agitators, while the Type 3740D is designed for top-entry mixers and other dry-running application with large shaft run-out and harsh operating conditions.

Volatile emission control: To ensure its spindle seals for valves and fittings meet the highest fugitive emission requirements, including the latest TA-Luft regulations and those in EN 15848 and API 622, EagleBurgmann recently updated its BuraTAL seal sets. A spring-backing, live-loading system that maintains the required contact pressure for the seal set ensures extremely low values for leakage and spindle friction. Because BuraTAL is resistant to nearly all chemicals, steam, alcohol, water and oil, excluding strong oxidizers, the new seal sets are suited for original equipment and retrofitting in valves and fittings found in the chemical, petrochemical, refinery and processing industries.

Enhanced support system: Seal reservoirs store barrier or buffer fluid for dual mechanical seals that require clean, cool, well-lubricated secondary seal conditions. Flowserve developed a three-gallon W8 Seal Support Reservoir System that lubricates seal faces while also managing water consumption. It has a visual water flow indicator that allows ready detection of excessive water consumption, a corrosion-resistant 316 SS cooling coil to maintain the optimal buffer/barrier temperature, a pressure regulator to control barrier pressure, and an automatic refill valve to replenish the buffer/barrier fluid from an external header. The support system, designed for liquid-lubricated dual pressurized and non-pressurized mechanical seals, reduces process leakage and lowers operating costs.

E-mail Contributing Editor Sheila Kennedy, managing director of Additive Communications, at [email protected].

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