Clamping Device for Ceramic to Metal Seals
Publication Date: 2015-May-26
The IP.com Prior Art Database
In the field of high temperature gas handling, applications of which use ceramic components, there is a need to form reliable ceramic to metal seals which exhibit low (or no) gas leakage rates. Such applications include ceramic gas separation membrane systems, ceramic membrane reactor systems, and solid oxide fuel cells. In addition to high reliability, these seals also are required to have tolerance for thermal cycling and show stable performance over the anticipated lifetime of the system. It is also advantageous that the performance of these seals be verifiable at room temperature during apparatus construction. The ideal solution would also be economical and easy to assemble.
Such ceramic to metal seals as have been disclosed in the prior art, an example of which can be found in WO 2003092106, require significant clamping forces to effect the seal. Many ceramic materials used to fabricate ceramic gas separation membrane systems have limited strength and can be damaged by the application of these high clamping forces. The current concept proposes a means of securing the ceramic components for installation and start-up. An initial clamping force is applied during installation. However, with the device described here, the clamping force releases when the system is heated to the operating temperature. Releasing the force applied by the mechanical clamp serves to prevent the clamp from damaging the ceramic when the assembly is heated to high temperatures. This is accomplished by choosing a design and materials so as to release the clamping forces imposed during initial installation as the system is heated to operation temperatures. During operation, the sealing force is provided by the elevated pressure of the external gas acting through the ceramic joining element instead of a mechanically applied force through the clamp.
The following schematic Figure I and tables illustrate an example of this concept.
Figure I. Schematic Illustration of Clamping Device
A ceramic to metal seal (not shown) is placed between ceramic member, A, and metal alloy plate, B. It is desired to apply a clamping force between the ceramic and the metal plate. In the figure, ceramic membrane member, A, with coefficient of thermal expansion, aA, and length, lA, is clamped to metal alloy plate, B, with coefficient of thermal expansion, aB, and length, lB, by a metal alloy clamp, D, with coefficient of thermal expansion, aD, and length, lD, where element, C, is a compensating spacer with coefficient of thermal expansion, aC, and length, lC. The metal alloy clamp can have a threaded end, E. A nut, F, can be used to apply a load on the compensating spacer C. The load is transmitted through the clamp D and compensating spacer C to the ceramic, A, and the metal plate, B. This load applies the initial clamping force to the ceramic to metal seal desired for installation and start-up. The materials and di...