STRUCTURAL MODIFICATION

Lee Jinho
Kwangzin Valve Industrial Co.,Ltd, Korea
Kim Harkbong  Kim Moonsang
School of Aerospace and Mechanical Engineering, Hankook Aviation University, Korea

Abstract: The possibility of pressure control with the structural change of a safety valve is investigated. Safety valve is commonly used as safety devices for numerous applications which include boilers, ships, industrial plants, and piping, Setting and stopping pressures of a safety valve, p_set and p_sto ,are traditionally adjusted with a fine tuning of seat ring and valve ring heights, The depth of inside and outside grooves in a valve, h_ar and h_vr are modified and their effects on setting and stopping pressures of a safety valve are tested. The most appropriate values appear 1.0 mm in d_i and 0.5~1.0 mm in d_o , respectively. The valve ring height, h_vr, shows that the best results can be achieved at 2.3 mm for setting pressures of 0.1~0.4 MPa and 1.0 mm for setting pressures of 0.5~1.0 MPa. The stopping pressures increases with the increase of seat ring height, h_sr , upto certain h_sr value and then becomes independent to the seat ring height. This implies that there exists the optimum h_sr ,which provides the largest flow rate and the proper stopping pressure. Stopping pressures of a safety valve are adjusted with the seat ring and valve ring heights. This study, however, demonstrated that the modification of value grooves also changes setting and stopping pressures of a safety valve. Therefore, the proper selection in dimensions of the inside and outside grooves should be considered for the safety valve design.

Key words: Safety valve  Compressive flow  Isentropic flow theory Isentropic comressibility theory  Setting pressure  Stopping pressure  Continuity equation  Momentum equation

Manuscript received on December 12, 2000; revised manuscript January 22, 2001

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