Figure 3. A high-temperature, dual gas-lubricated seal
A significant advantage of dual gas seals over dual liquid- lubricated seals is the elimination of product contamination. Barrier gases, such as nitrogen, are inert and will not cause contamination or degradation of the process fluid. This advantage has also been applied in the food and pharmaceutical industries in which product purity and safety is paramount.
Low Cost of Ownership
Dual gas-lubricated seals can also offer an overall lower cost of ownership as compared to liquid-lubricated seals. The reduction of energy consumption is a major contributor to this advantage as confirmed by analysis with the FSA Life Cycle Cost Estimator. While the initial capital cost for a dual gas-lubricated seal may be higher than that for a comparable liquid-lubricated seal, when the total cost for the seal and its support system is included, the dual gas-lubricated seal may become more economical because of the simplicity of its support systems. This advantage becomes more compelling when the installation of dual gas-lubricated seals and their systems are considered. The control panels for dual gas seals usually only require simple inlet and outlet connections. However, a liquid seal requires more complex plumbing with proper location, piping slope and cooling water connections. Dual gas-lubricated seals also require little, if any, maintenance when compared to the regular refilling of dual liquid-lubricated seal support fluids.
Figure 4. A simple dual gas-lubricated seal – API 74 piping plan
While dual gas-lubricated seals require careful application and consideration for proper operation, they can provide compelling advantages compared to other sealing solutions. They offer energy efficiency, indifference to dry running conditions, zero product emissions, no product contamination and lower cost of ownership. They provide solutions for difficult sealing challenges because of their advanced design, technology and unique operation.