(49c) Dual Function VALVES for Ethylene Transfer LINE Applications

Economic forces continue to push the capacity of new grassroots crackers higher, and the capacity of cracking furnaces rises ever higher because of economies of scale. The trends in transfer line valve design have necessarily followed this same scale-up path, which has resulted in valves of unprecedented size and complexity.

Rotary tilting disc style valves have emerged as the most cost effective design, primarily due to a smaller envelope and lighter weight as compared to sliding gate, plug or ball valves. Reduced maintenance costs have also been attributed to the rotary tilting disc valve because of the reliable closing (not sensitive to piping loads), simplified maintenance and enhanced safety aspects made possible by the free-acting auto-close feature offered by this design.

Inclined conical, tilting-disc metal seated valves, offering both isolation and non-return function, have been used in transfer line service at three plants since the 1980's. Review of performance level, safety enhancement and routine maintenance history associated with these long life valves shows why the rotary tilting disc style valve design continues to win favor in ethylene plant transfer line applications.