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Dynamic performance of a high temperature check valve and initial testing of a ceramic ball valve
B.T. Johnson, J.E. Smith Jr.,
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Standard valves typically have components in them, which are unsuitable for high temperature and corrosive environments. The usage of ceramic components in check and ball valves represents an effective solution for high temperature applications. Ceramic springs and seats were machined using a custom designed computer automated SD 300 Prazi lathe. This lathe was used to fabricate springs of 10, 12, 14 and 16 Turns per Inch (TPI) for check valves and a 17 TPI spring for the ball valve. All ceramic components were produced from Yttria stabilized zirconia. The ceramic seats were machined using a diamond round tool and installed into the valve body. The seats were lapped using a special Metadi diamond polish to mate the sealing surfaces. The valve components were specially altered by Parker Hannifin Corporation to accommodate the ceramic components. A spring pocket was provided in the check valve cap so that the poppet comes to a stop when it hits the spring pocket. This prevents the spring from getting compressed beyond reasonable limits. A spring pocket was also machined into the end flange for the ball valve to accommodate the inlet ceramic spring. Seat pockets were also provided in the valve cap and flange body to accommodate ceramic seats in both. Check valves was tested for leakage and cracking pressure both from ambient temperatures to temperatures of 898 K. Cracking pressures for the ceramic check valves were relatively constant and ranged from (26.455 +/- 0.186) to (8.44 +/- 0.182) psi for the 10 to 16 TPI springs installed in the valve. The ball valve was fabricated from a solid Alumina ceramic ball, core drilled and slotted to match Parker Hannifin's dimensions. Ball valves typically use bidirectional flow however the current design must be unidirectional. The exit seat was solidly mounted while the inlet seat was spring loaded. This arrangement enhances sealing pressure on the ball. The ball was lubricated using a high temperature graphite lubricant. The operating pressure of the ball valve with the 17 TPI spring exceeds our test pressure of 200 psig. The design withstood 200 psid over a two hour period without signs of leakage. These are preliminary experiments with this ball valve design, and represent the initial steps in the development of a high temperature variant.
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